NCD991278540_20051103_Weyerhaeuser Company_FRBCERCLA RI_Remedial Investigation 2000 - 2005-OCR

A Weyerhaeuser
The future is growing'"
November 3, 2005
Mr. Randy Bryant
Project Manager
USEPA Region IV
Waste Management Division
.. '
61 Forsythe Street, S.W., I Ith Floor
Atlanta, GA 30303-3104
Subject: Weyerhaeuser Company
Former Chlorine Plant, OU-3
Martin County, North Carolina
Corporate Headquarters
PO Box9777
Federal Way WA 98063-9777
Tel [phone]
l[B) &: © @ 0 WI & ~
1171 NOV Q 9 2005 IJdJ,
SUPERFUND SECTION
Preconstruction Investigation Workplan -Target Excavation Area 2a
Dear Mr. Bryant:
In a letter dated May 19, 2005, Weyerhaeuser Company (Weyerhaeuser) responded to the United States
Environmental Protection Agency's (USEPA's) Review Comments on the Remedial Action (RA) Workplan for
the Fonner Chlorine Plant (FCP) area at the Weyerhaeuser Martin County, North Carolina, facility. In that
letter, Weyerhaeuser responded that they would perform a preconstruction investigation around Target
Excavation Area 2a to determine the practicable extent of the excavation. On September 26, 2005, a conference
call was held among Weyerhaeuser, the USEPA, and RMT, Inc. (RMT), to discuss the details of the
preconstruction target area investigation.
Enclosed is Wcyerhaeuser's !'reconstruction Investigation Workplan describing the field activities for this
investigation. It includes the status of the FCP site, the reasons and the objectives for the investigation of Target
Area 2a, the proposed field activities and documentation, and the implementation schedule.
Weyerhaeuser is prepared to execute the preconstruction investigation immediately upon your approval of the
workplan. Please contact me (253-924-6650) if you have any questions.
Sincerely,
:z::::::t
Environmental Manager
Enclosures: Preconstruction Investigation Workplan
Figure I -Proposed Soil Boring Locations
Table 2 of January 14, 2005, Technical Memorandum
cc: Kris Krause -RMT, Inc.
! Nile Testennan -NCDENR
John Gross -Weyerhaeuser
l:\WPMSN\l'Jf\00-05 \00172,0000 I •L000510072-00 I .DOC
• •
Preconstruction Investigation Workplan
Weyerhaeuser Company
Former Chlorine Plant Target Area 2a
1.0 Introduction
1.1 CERCLA Site Status
The Fonner Chlorine Plant (FCP) area of the Weyerhaeuser Company (Weyerhaeuser) Plymouth
Wood Treating Plant Site (site) in Plymouth, North Carolina, is being remediated under the
Superfund Alternative Sites Program of the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). In September 2003, the Record of Decision (ROD)
was issued for the site, followed by the lodging of a Consent Decree in May 2004 to perform
Remedial Design/Remedial Action activities. The final Remedial Action (RA) Workplan,
containing the Remedial Design for this alternative, was approved by the United States
Environmental Protection Agency (US EPA) in June 2005.
1.2 Workplan Background
On April 26, 2005, the USEPA provided written comments to Weyerhaeuser on the draft
Remedial Action (RA) Workplan. They stated that additional soil sampling may be necessary for
the Target Excavation Area 2a prior to the RA construction. This was in response to the total
mercury concentrations, which exceeded the Remedial Goal Objective (RGO) of 20 ppm in three
of four soil borings (DP-I 1, DP-12, and DP-13) sampled during the performance of an
investigation conducted as part of the predesign activities in November 2004.
During this predesign investigation, soil sampling was conducted at 2, 4, 8, and 12 feet below
ground surface at each of the three boring locations. As presented in a January 14, 2005,
Technical Memorandum, the average mercury concentrations at these three boring locations were
13.2, 20.4, and 15.5 ppm, respectively (Table 2 from this Technical Memorandum is attached).
Although eight of the 12 soil samples collected from these three borings showed mercury
concentrations of less than 12 ppm, four of the 12 samples showed concentrations of between
30 and 50 ppm at the 4-foot interval. The USEPA also commented that the excavation should
extend somewhat deeper than 4 feet below ground surface unless underground obstructions would
prevent a deeper excavation.
In response to the USEPA's April 26, 2005, comments on the draft RA Workplan, Weyerhaeuser
agreed in a letter dated May 19, 2005, to conduct a preremedial action construction investigation
to determine the practicable extent of the excavation that could be conducted in Target
Excavation Area 2a. This investigation is necessary because excavation in this target area will be
limited as a result of the area's overall configuration, and its proximity to cooling towers, a major
motor control center, subsurface foundations, and underlying/overhead utilities. The data from
this investigation will be evaluated to design an excavation area that will result in the average
concentration ofresidual mercury remaining in soil to be below the RGO of20 ppm.
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• •
On September 26, 2005, a conference call was held among Weyerhaeuser, the USEPA, and RMT,
Inc. (RMT), to discuss the details of the preconstruction investigation. As requested by the
USEPA, this investigation will provide additional mercury data for the shallow soil north of
Target Excavation Area 2a to delineate the final extent of this area prior to conducting excavation
activities. It was agreed during this discussion that this additional information, in conjunction
with the existing analytical data for this area, will preclude the need for confirmation sampling
and associated analytical delays during RA excavation activities. This will eliminate unsafe open
excavations and unsupported, exposed sidewalls for extended periods.
This workplan presents the anticipated Remedial Action preconstruction investigation activities
for Target Excavation Area 2a.
2.0 Preconstruction Investigation Activities
2.1 Objectives of the Preconstruction Investigation Activities
The purpose of the preconstruction investigation field activities is to obtain site-specific analytical
information north of Target Excavation Area 2a, namely from within the "alleyway" between the
Motor Control Center and the Cooling Tower. The specific objectives for the preconstruction
investigation activities are as follows:
To determine soil mercury concentrations north of the Target Excavation Area 2a extent
presented in the May 2005 RA Workplan
To determine the practicable extent of soil excavation for Target Excavation Arca 2a
The tasks to be performed during the preconstruction field activities include advancing soil
borings to collect the analytical data and proper management of the investigative-derived waste
materials. These activities are discussed further in the following subsections.
2.2 Field Investigation
The soil boring pro,,'fam is anticipated to consist of up to two soil borings that would be advanced
north of the Target Excavation Area 2a footprint presented in the RA Workplan._ The borings will
be advanced to an estimated depth of 6 feet below ground surface (bgs) since elevated levels of
mercury have not been detected below 5 feet in any of the previous Area 2a soil borings.
Approximate soil boring locations are presented on Figure I.
The soil borings will have to be advanced by hand, and final locations will be closely coordinated
with the Weyerhaeuser utility managers since the area between the Motor Control Center and the
Cooling Tower has very limited access and has significant surface and subsurface obstructions,
including an extensive network of buried utilities. Upon surface pavement coring, soil will be
sampled using a hand auger and/or hand-driven split-spoon sampler, and analytical samples will
be collected in 2-foot intervals from 2 to 6 feet bgs (i.e., two samples collected for analysis per
borehole, one sample from the 2-foot to 4-foot bgs interval, and one sample from the 4-foot to
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• •
6-foot bgs interval). Analytical samples will be sent to Weyerhaeuser Analytical Testing Services
in Federal Way, Washington, for total mercury analyses.
2.4 Decontamination of Drilling and Sampling Equipment
The equipment used for soil sampling will be washed with water/ Alconox and rinsed with clean
water prior to beginning the field investigation. The same procedure will be applied to the down-
hole augering and sampling tools between boring locations and to all sampling equipment prior to
it leaving the sampling area. Water used for cleaning will be obtained from a potable water
source.
2.5 Investigation-derived Waste Management
Decontamination water, soil, and other solid waste decontamination material generated from the
investigation activities will be containerized on-site. Waste materials will be handled in
accordance with the Field Sampling and Analysis Plan and the Health and Safety Plan previously
approved by the USEPA for the FCP. The soil cuttings will be disposed in accordance with
applicable state and federal regulations based on the results of the soil sample testing analytical
results, and the decontamination water (approximately 5 gallons) will be disposed at the site's
wastewater treatment plant.
3.0 Documentation and Data Evaluation
A preconstruction technical memor_andum will be prepared documenting soil borings and soil borehole
abandonment forms. The soil analytical information will be evaluated and used to determine and finalize
the limits of Target Excavation 2a as well as to develop an appropriate excavation approach. The soil
borehole abandonment form will be prepared and submitted to the North Carolina Department of
Environment and Natural Resources (NCDENR).
4.0 Schedule
The field activities are expected to be completed within one working day and are anticipated to
commence in November 2005, pending the USEPA's approval of this prcconstruction workplan and the
availability of personnel. The analytical information obtained during this investigation is expected to be
immediately incorporated into the remedial action efforts. Borehole abandonment documentation will be
provided to the NCDENR within 30 days of the completion of the well abandonment.
l,\WPMSN\P ffi00-05 l00\72\00001\L0005\0072-001 A DOC 3
,----
/
COOLING TOWER
WATER PIPES
SDP-7
\
\
!
J
MOTOR CONTROL CENTER
i2J --
21 -
LEGEND
I/ /I
LIMITS OF TARGET EXCAVATION
AREA 2A AS PRESENTED IN
THE MAY 2005 RA WORKPLAN
OVERHEAD PROCESS PIPING
iZ1 PIPE CHASE SUPPORT FOOTER
•
SCPSB-15
@ CP-OS-1
@ SB-11C
S DP-12
[<88-41
0
PROPOSED SOIL BORING
LOCATION (FINAL LOCATION TO
BE FIELD DETERMINED)
SHALLOW SOIL BORING
LOCATION
GROUNDWATER MONITORING
WELL LOCATION
PREDESIGN GEOTECHNICAL
BORINGS
PREDESIGN DIRECT PUSH
LOCATION
MAXIMUM MERCURY
CONCENTRATION DETECTED
TOP 10 FEET, AND DEPTH
DETECTED
10 20
SCALE: 1·-10•
IN
PROJECT: WEYERHAUSER COMPANY
FORMER CHLORINE PLANT
PLYMOUTii, NORTH CAROLINA
--------------SHEET TITLJiRECONSTRUCTION INVESTIGATION
-l------'P'-'Rc::O:::PO~S=E=D:;....::SO=IL:...:BO=R:..:l::.:N:.=G:...:L;::OC=A.:..:Tlc::O:::Nc:....::MAP=--=.. __ --1
DRAWN BY: REYZEKD SCALE:
CHECKED BY: BSS 1 "= 1 O'
APPROVED BY: KOK
DATE: NOVEMBER 2005
PROJ. NO. 5100. 72
FllE NO. 51007201.DWG
FIGURE 1
7« Heart/and Trail
Madison, W1 53717-1934
P.O. Box 8923 53708-8923
Phone: [phone]-
Fax: 608-831-J.J.34
•
Table 2
Total Mercury Summary
Weyerhaeuser Company
•
Former Chlorine Plant -Plymouth, North Carolina
DP-10 2
4
8
12
DP-I I 2
4
8
11
DP-12 2
4
8
12
DP-13 2
4
7
12
HA-I 4-6
I:\ WPMSN\P moo-05 l 00\72\00001 \T0005 I 0072-00 I. DOC
19.7
<0.1
0.8
1.3
0.1
44.4
0.2
8.1
29.6
49.8
<0.1
2.2
11.3
38.8
0.3
11.4
26.9
•
RMT,Jnc.
744 Heartland Trail (53717-1934)
PO Box 8923 (53708-8923)
Madison, WI
•
Letter of Transmittal
Tel. [phone] • Fax [phone]
To: Facilitated Meeting Group Date: April 7, 2004
Prepared By:
Signature:
We are sending you:
1 4/7/04
1 4/7/04
1 4/7/04
Project No.: 5119.12
Subject: Action Item Memoranda
Stacy McAnulty Title Senior Project Manager
IBl Other: Action Item Memoranda·
Action Item Guidance materials for remedy goal discussion (1 page)
#15
Action Item
#16
Action Item
#29
Status of the likely use of Welch Creek by striped bass
(3 pages)
Revised Remedial Action Objectives (1 page)
These items are transmitted via e-mail and hard copy regular U.S. Mail
I:\ WPMSN \Pff\00--05119\ 12\ l.000511912-0IO.DOC 4/7104 TRANSL TR.DOC FORM F334 (04/24/01)
Date:
To:
From:
Subject:
• •
Weyerhaeuser Project l\1emorandum
April 7, 2004
Facilitated Meeting Group
RMT, Inc. (Stacy McAnulty)
Action Item #15, Guidance Materials for Remedy Goal Discussion
The US EPA and other stakeholders at the October 15, 2003, meeting of the Welch Creek facilitated
meeting group identified the need for additional significant guidance materials to help with remedy goal
discussions. The two references listed below were provided for consideration by the USEPA (Sharon
Thoms) and NOAA (Michel Gielazyn).
USEP A. Framework for Application of the Toxicity Equivalence Methodology for Polychlorinated
Dioxins, Furans and Biphenyls in Ecological Risk Assessment (External Review Draft). U.S.
Environmental Protection Agency, Risk Assessment Forum, Washington, DC, 630/P-03/002A, 2003.
http:// cf pub .epa. gov /ncea/raf/recordi sp I av .cfm ?deid=5 5669
USEPA. Interim Report on Data and Methods for Assessment of2,3,7,8-tetrachlorodibenzo-p-dioxin
Risks to Aquatic Life and Associated Wildlife. March 1993. EPA/600/R-93/055.
http:/ /yosemi t e.epa. gov /water/ owrcca ta I og. nsf/0/ f73bfff dcef I ef0c8525 6b06007 23de8 ?Open Document
l:\WPMSN\Pfl\00.051 l9\12\Mll0051 !9!2-013.DOC 4n/04
• •
Weyerhaeuser Project Memorandum
Date: April 7, 2004
To: Facilitated Meeting Group
From: Weyerhaeuser (Martin Leho) and US Fish and Wildlife Service (Tom Augspurger)
Action Item #16 -Status of the Likely Use of Welch Creek by Striped Bass Subject:
The October 15, 2003, Stakeholder meeting identified an action item (#16) to check the status of striped
bass use of Welch Creek by contacting fisheries biologists familiar with this system. Tom Augspurger
and Martin Lebo conducted separate phone discussions with James W. (Pete) Kornegay (252/338-3607)
on the life history of anadromous species in the Roanoke River system. Mr. Kornegay is the Coastal
Region Fisheries Research Coordinator with the NC Wildlife Resources Commission's (NCWRC)
Division of Inland Fisheries. A synthesis of the two conversations is provided below based on a
November 20, 2003 email prepared by Tom Augspurger (see Attachment) and notes by Martin Lebo
during a January 15, 2004 call with Mr. Kornegay.
Striped Bass in the Roanoke River System
■ Welch Creek would not have its own population of striped bass; individuals using the creek would
be part of the larger Roanoke-Albemarle Sound population until migrating out of the system to join
the coastal stock.
■ The Roanoke-Albemarle Sound population of striped bass was declared "restored" in 1997.
■ Since the stock has been declared restored, there is now an emphasis on restoration of impaired
habitat system-wide
General Life History of Striped Bass
•
•
•
•
•
•
•
•
•
•
March -males move upstream to spawning region
April -females move upstream
May -spawning occurs when river temperature is 18-22°C (:.. River Mile 125) .
Eggs are semi-buoyant and hatch while being transported downstream (near Hamilton, -River
Mile 60).
Yoke sac larvae attain some vertical movement capability when they reach Plymouth (-River
Mile 5)
Approximate age 2 weeks -develop mouth parts and feed on zooplankton
Approximate age 2 to 4 months -fingerlings forage on small crustaceans
Fall -juveniles move into Albemarle Sound and feed on small fish
Sexual maturity -

2

to 3 years for males; 4 to 6 years for females
Older adults -move out of the Sound to integrate into coastal stock
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• •
Weyerhaeuser Project Memorandum
Nursery Use of Tributaries
■ Potential areas include Western Albemarle Sound, the Roanoke River delta, the distributaiies
network, and local tributaries.
■ Data specific to Welch Creek have not been collected by the NCWRC. However, Welch Creek is
expected to be used by striped bass based on data collected in the main stem of the Roanoke River
near the mouth of Welch Creek and other blackwater creeks in the system (e.g., Warren Neck
Creek).
■ Food availability is the key determinant of location when dissolved oxygen (DO) and temperature
are adequate. Juveniles would not utilize Welch Creek during periods of low DO.
■ Forage strategy would have juvenile striped bass enter tributary creeks for short periods (i.e., few
. days) to feed on small fish or crustaceans.
■ Sub-adult striped bass forage (largely on blueback herring) in the middle to lower portions of
blackwater creeks in the system.
Other Anadromous Species
■ Hickory Back, River herring (Alewife and Blue-back), and shad all have similar life histories with
variation in timing of spawning and location.
• Mature adults of all species spend most of the year in coastal ocean waters -including striped bass
when older adults present in the population.
■ Juvenile stages of herring and shad tend to stay in rivers longer than other species and leave when a
sharp drop in temperature occurs.
l:\WPMSN\Pffit)()•OSI 19\12\MOOOSl 1912·014.DOC 4nl04 2
• •
Weyerhaeuser Project Memorandum
Attachment
F¥'om.::];6fu -iA,fg~riu'tgct@fws;!!'ovrsMTP,:Tom· Augspurgcr@ri•s:i!ov¥\;_./k:, .. ·1
. . -.... r.,_..,. ____ ...,....;,...,_-======'-"="-""-'-"-""-"-="-"===-='-'l-~.,_--~;;.....~.<ci
Sent: Thursday, November 20, 2003 I 0:28 AM
To: [e-mail]; [e-mail]; [e-mail]:
[e-mail]; [e-mail];
[e-mail]; [e-mail];
[e-mail]; [e-mail]
CC: [e-mail]
Subject: striped bass information
Hello -
One of the action items for the Weyerhaeuser Welch Creek work was to foilow-up on the status of striped bass
in the creek by contacting fisheries biologists familiar with the system. On October 30, 2003, I spoke with
James W. (Pete) Kornegay (252/338-3607), Coastal Region Fisheries Research Coordinator with the North
Carolina Wildlife Resources Commission's (NCWRC) Division of Inland Fisheries. Here's a summary:
Welch Creek would not have its own population of striped bass; striped bass found there would be part of
the larger Roanoke-Albemarle Sound population
the Roanoke-Albemarle Sound population of striped bass was declared "restored" in I 997
no data specific to Welch Creek have been collected by the NCWRC, however, Welch Creek is expected to
be use.ct by striped bass based on data collected in the mainstem of the Roanoke River near the mouth of
Welch Creek and blackwater creeks nearby similar to Welch Creek ( e.g., Warren Neck Creek)
striped bass are routinely found in the mainstem of the Roanoke River near Welch Creek in the NCWRC
sampling
young-of-year striped bass use the middle to lower portions (areas of the stream where dissolved oxygen
levels are sufficient) ofblackwater tributaries like Welch Creek as nursery areas
sub-adult striped bass forage (largely on blueback herring) in the middle to lower portions of black water
creeks
since the stock has been declared restored, there is now an emphasis on restoration of impaired habitat
system-wide
Please give me a call if you have any questions. Have a good rest of the week,
Tom Augspurger
919/856-4520 x.21
919/856-4556 (fax)
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• •
Weyerhaeuser Project Memorandum
Date:
To:
From:
Subject:
April 7, 2004
Facilitated Meeting Group
Weyerhaeuser (Martin Lebo) and RMT, Inc. (Stacy McAnulty)
Action Item #29, Revised Remedial Action Objectives
The USEPA and other stakeholders at the January 14, 2004, meeting of the Welch Creek facilitated
meeting group identified the need to refine the Remedial Action Objectives (RAOs). The facilitated
meeting group discussed adding an ecological RAO to address potential habitat impacts resulting from
active remedy implementation. The following RAOs were presented at the January 14, 2004, meeting.
The proposed additional ecological RAO is added in bold text.
Revised Remedial Action Objectives
Human Health
• Maintain acceptable levels of potential risk to site-specific human receptors
Ecological
• Protect the health of local populations and communities of biota
■ Reduce the dioxin concentrations in whole fish tissues over time to the extent practicable
• Achieve surface water concentrations at or below surface water standards, to the extent practicable
■ Limit biological uptake of COCs from the sediment in areas with excess potential risk, to the extent
practicable
■ Minimize the adverse effects of remediation activities on the eidsting aquatic environment
and/or wetland habitat, to the extent practicable
Management of Migration
• Minimize significant migration of COC-containing sediment in delineated areas of concern, to the
extent practicable
No modification was made to the proposed human health RAO, as presented at the facilitated meeting.
Specifically, human consumption of fish is not included as a separate RAO because no unacceptable risk
was calculated for this pathway. Furthermore, because fish consumption is implicitly included in the
human health exposure, it does not appear to warrant a separate RAO.
l:\WPMSN\Pmoo.051 ]9\ 12\Ml)(X)5] 1912-015.DOC 4/7/04
•
RMT, Inc.
744 Heartland Trail (53717-1934)
PO Box 8923 (53708-8923)
Madison, WI
Letter of Transmittal
Tel. [phone] • Fax [phone]
To: Jessica Wollmuth
John Gross
Michel Gielazyn
Mike Edwards
Nile Testerman
Paul Schroeder
Harold Taylor
Sharon Thoms
Tom Ausgpurger
Jennifer Wendel
Kathy Huibregtse
Prepared By: Linda Rawson
Dear Stakeholders:
Date:
•
1/28/04
5119.12
Effects of Roanoke River Stage on
the Hydrodynamics and Sediment
Transport Potential of Welch Creek
Enclosed please find a copy of the Effects of Roanoke River Stage on the Hydrodynamics and Sediment
Transport Potential of Welch Creek by Steven Scott of the U.S. Army Core of Engineers. Per Randy
Bryant's request, copies a~e being distributed to entire stakeholder meeting group.
Stacy has done an initial review and indicates no significant changes have been made.
Please contact Stacy directly with questions.
J: \ Wl'MSN \l'JT\00-05119\ 12 \ 1..000511912-004, DOC l/28/04 Tl<ANSLTR.DOC FQl{M f-334 {04/24101)
• •
EFFECTS OF ROANOKE RIVER STAGE ON THE
HYDRODYNAMICS AND SEDIMENT TRANSPORT
POTENTIAL OF WELCH CREEK
January 9, 2004
Stephen H. Scott
Coastal and Hydraulics Laboratory, Waterways Experiment Station (WES)
U.S. Army Engineer Research and Development Center
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
Prepared for: U.S. Environmental Protection Agency, Region 4
North Superfund Management Branch
Waste Management Division
61 Forsyth St.
Atlanta, GA 30303-8960
• •
BACKGROUND
A number of studies have been conducted by the Engineering Research and Development
Center, Waterways Experiment Station (ERDCWES) to evaluate sediment mobilization
potential in Welch Creek. The hydrodynamics of Welch Creek were evaluated for a
number of tidal surge and freshwater inflowing storm events using RMA2, a two-
dimensional finite element hydrodynamic numerical model. The tidal surge events
consisted of hurricane, northeaster, and wind tide events. The freshwater flood events
were 2,5,10, 25, 50, and 100-year return flow events. For each simulation, the bed shear
stress resulting from the flows was related to the erodibility of Welch Creek sediments.
Based on the computed shear stress and the measured critical shear stress for erosion of
the Welch Creek sediments, sediment transport computations were performed and
summarized. For the tidal surge events, only the hurricane event resulted in flows high
enough to potentially mobilize bed sediments, however, the potential for significant bed
erosion to occur was judged to be low due to the short duration of the event. The analysis
indicated that the reach of Welch Creek from Master Transect 7 (MT-7) through General
Transect 15 (GT-15) contained flows with the highest bed shear stress distribution.
Analysis of the return freshwater flood events indicated that the 2-5 year events had a low
potential for sediment mobilization due to relatively low bed shear stress, whereas the ten
year and greater events had a high potential for sediment mobilization due to the long
term duration of flows with bed shear stress exceeding 0.20 Pascal. As with the tidal
surge events, the reach of Welch Creek between MT-7 and GT-15 indicated the highest
potential for erosion and transport of bed sediments. The modeling results are detailed in
an ERDCWES technical report (Scott 2001).
The results of the above-described study indicated that the highest potential for
mobilization of Welch Creek bed sediments was for the IO year-100-year return flood
events. However, the simulations were performed for a constant water surface elevation
of 0.9 ft at the Roanoke River (average at the Weyerhaeuser gauging location). The
Roanoke River stage can vary considerable due to releases from Roanoke Rapids dam
( ~ 130 miles upstream from the mouth of Welch Creek) or localized and regional storms.
It is possible that the higher return flow events (I 0-IOO years) may occur regionally, thus
the Roanoke River stage could potentially be much higher (2.0-2.5 feet). This would
result in over bank flooding, a reduction in the energy slope in Welch Creek, and lower
bed shear stress due to lower flow velocities.
A second report was prepared by the ERDCWES to further summarize the study results
and determine a reasonable value of critical bed shear stress for the initiation of bed
erosion in Welch Creek (Scott 2002). Based on the initial study results, bed sediment
laboratory analyses, and published data on the critical shear stress for mobilizing fine
sediments, a value of 0.2 Pascal was chosen as representative for Welch Creek.
This study presented in this report was performed to evaluate the change in sediment
mobilization potential due to higher Roanoke River stages. Additionally, the impact of
wetland over bank flows on sediment mobilization was evaluated, as well as how future
2
• •
changes in Welch Creek watershed morphology will alter the hydrodynamics and
sediment transport in the creek.
APPROACH
The previous study (Scott 2001) utilized RMA2 to compute water surface elevations and
flow velocities in Welch Creek for the selected events. Concurrent with this analysis,
Weyerhaeuser conducted hydrodynamic simulations with a one-dimensional model. The
two-dimensional model provides both lateral and longitudinal (stream wise) resolution of
flow velocity and water surface elevation (depth averaged). The one-dimensional model
provides laterally and depth averaged flow velocity and water surface elevation. In order
to compare the one-dimensional model results, the RMA2 data were presented as an
average value at each transect.
For this study, the bed shear stress was computed in two dimensions with RMA2. The
model computes velocity and water surface elevation at each node in the model domain.
The velocity is computed from the Manning equation:
R211 * S 1/2
V=l.49* 1 (I)
n
with R the hydraulic radius, Sr the energy slope, and n the Manning coefficient for
roughness. The value of Manning n is the total roughness of the channel when used to
compute velocity and water surface elevation. This includes the form roughness, which
takes into account variations in channel plan form, bed forms, vegetation, and channel
geometry, and the grain roughness, which is based on the size of the bed sediments. For
the Welch Creek hydrodynamic computations, a Manning n of approximately 0.03 was
used due to the sinuosity of the channel, irregular geometry, and presence of vegetation.
To compute the grain roughness, a relationship developed by Strickler (Strickler 1923)
was utilized:
d 116
n =-so_
g, 20 (2)
with n8, the Manning n for grain roughness and d5o the median grain size of the bed
sediment. When computing the bed shear stress responsible for erosion of the bed, the
grain roughness should be used instead of the total roughness. By definition, the bed
shear stress is defined by:
(3)
3
• •
with y the specific weight of water. Substituting equation 3 into equation I, and using the
grain roughness computed by equation 2 for the value of Manning n results in the
following expression for grain bed shear stress:
'· ( n y v 2
r• = y* 1.49) * R113 (4)
with V the velocity magnitude. For the bed shear stress computations, fine sand was
assumed based on bed sample analysis. This resulted in a grain roughness of
approximately 0.01.
To evaluate the impact of a higher Roanoke River stage on potential sediment mobility, a
series of model simulations were conducted for both the ten year and twenty-five year
return flood events with Roanoke River water surface elevations of 0.9, 1.5, 2.0, and 2.5
feet msl. The potential for sediment mobilization due to over bank flows was evaluated
by examining the velocity distribution of return flows during the Hurricane Dennis event
which was previously modeled.
ANALYSIS
The modeled study area is presented in Figure I. The upstream boundary of the Welch
Creek study area was the Highway 64 Bridge, approximately 4 miles upstream from the
Roanoke River. The lower boundary was the creek mouth at the Roanoke River. The
extent of the modeled area was out to approximately the 5.0 ft ms! contour. The top bank
elevation of Welch Creek is variable, ranging from approximately 1.5 feet to 2.0 feet msl.
The average creek top width is approximately I 00 feet. The RMA2 model numerical
mesh is shown in Figure 2. The mesh consisted of 3185 elements and 9185 nodes.
The previous studies indicated the upper half of Welch Creek (Highway 64 Bridge to GT-
12) is relatively stable with a low potential for sediment mobilization. Therefore the
results of this analysis will be presented for only the lower 1.75 miles of the channel (GT-
12 to MT-10).
The results of the analysis are presented as color contours of grain bed shear stress in the
lower Welch Creek channel (Figures 3-10). The results are given for the maximum flows
for the event hydrograph. The threshold of the assumed critical grain bed shear stress for
bed erosion is the red contour (approximately 0.20 Pascal). The white areas on the
figures represent values of bed shear stress below the minimum scale value.
4
• •
MODELING RES UL TS
This section presents the simulation results for the IO and 25-year return flood events
with varying Roanoke River stage and the Hurricane Dennis over land flow velocity
distribution simulation.
MODELING SCENARIO 1: IO Year Return Flood Event in Welch Creek with
Roanoke River Water Surface Elevations of 0.9, 1.5, 2.0, and 2.5 feet ms!
Figures 3, 4, 5, and 6 present the bed shear stress contours for the IO-year event for
Roanoke River water surface elevations of 0.9, 1.5, 2.0, and 2.5 feet ms! respectively.
The only area where the critical shear stress threshold is exceeded is the creek reach
between MT-7 and GT-15 for the 0.9 ft and 1.5 ft simulations. The 2.0 ft and 2.5 ft.
simulations show bed shear stress values well below the critical threshold value of 0.20
Pascal for the entire reach, indicating negligible potential for bed erosion. The bed shear
stress in the reach of Welch Creek near the mouth (in the vicinity ofMT-10) is below the
critical shear stress threshold of 0.20 Pa for all simulations, therefore the potential for
erosion is negligible.
MODELING SCENARIO 2: 25 Year Return Flood Event in Welch Creek with
Roanoke River water surface elevations of 0.9, 1.5, 2.0, and 2.5 feet ms!
Figures 7, 8, 9, and IO present bed shear stress contours for the 25 year return flood event
in Welch Creek with Roanoke River water surface elevations of 0.9, 1.5, 2.0, and 2.5 feet
msl. The critical bed shear stress threshold is exceeded for the 0.9 ft and 1.5 ft ms!
simulations, whereas the higher Roanoke River stages (2.0 ft and 2.5 ft ms!) reduce the
flow velocity and bed shear stress levels to acceptable levels. As with previous
simulations, the primary area of concern with respect to sediment mobilization is the
stream reach from MT-7 to GT-15, which reflects the location of the pre 1970 wastewater
discharge from the Weyerhaeuser plant. The bed shear stress in the reach of Welch
Creek near the mouth (in the vicinity of MT-I 0) is below the critical shear stress
threshold of 0.20 Pa for all simulations, therefore the potential for erosion is negligible.
MODELING SCENARIO 3: Evaluation of Over Bank Flow Velocities During
the Hurricane Dennis Recession
The velocity of over bank flows is highly dependent on the Manning n roughness value
used in the computation. The wetlands adjacent to Welch Creek are highly vegetated and
thus are best represented in the model by a high roughness value in the range of 0.06 -
0.10. The thick vegetation along with the shallow depths in the wetlands during the
recession indicates that a high value of roughness is appropriate to use. However, to
simulate the worst-case scenario, lower roughness values were used in the range of 0.03-
0.05 in the simulation. Figure 11 shows the velocity contours for the peak of the
Hurricane Dennis recession. The velocities range from a low of approximately 0.1 feet
per second in the outer reaches of the wetland to approximately 0.3 -0.4 feet per second
adjacent to the stream channel. Note that the maximum velocities are adjacent to the
5
• •
sinuous reach of Welch Creek just before the MT-7 transect. Because of the extreme
channel sinuosity, the flow tends to leave the channel and flow directly across the bends.
A cut-off channel has formed in this reach that will eventually carry all the flow.
Because the wetlands are primarily covered in vegetation with a.substantial amount of
organic material covering the soil, it is highly unlikely that these low flows (0.1 -0.4 feet
per second) will mobilize the soil.
POTENTIAL BED SCOUR DUE TO FLOW EVENTS IN WELCH CREEK
The depth of erosion into the Welch Creek channel bed due to the simulated storm surge
events and return flood events was estimated in the previous study (Scott 2001). This
was estimated based on the simulated hydrodynamics, the erosion rate of bed sediment
samples, the assumption of a 0.9 ft water surface elevation at the Roanoke River (for the
return flood events), and the assumption of uniform erosion rate. The average erosion
depth for the lower ten creek reaches (bounded by MT-7 to MT-I 0) ranged from I mm
for the Hurricane Dennis tide surge event to 63 mm for the 25 year return flood event.
The average maximum erosion depth for the creek reaches between MT-7 and GT-IS
ranged from approximately 2 mm for the Hurricane Dennis event to 78 mm for the 25-
year return flood event. Table I presents the erosion depth data for Hurricane Dennis and
the 10 and 25-year return flood events. The assumption of a higher Roanoke River stage
(1.5 -2.5 feet) will result in lower bed shear stress, thus decreasing the depth of erosion
in the Welch Creek bed.
Event A VI! Erosion Depth -mm Max A vi! Erosion Depth -mm
Dennis I 2
10-Yr 43 65
25-Yr 63 78
IMPACT OF URBANIZATION OF THE WELCH CREEK WATERSHED ON
LOWER WELCH CREEK
If the upper Welch Creek watershed is developed, the amount and rate of runoff will
increase resulting in a higher discharge with higher peak flows. The upper Welch Creek
channel will adjust to this increased flow by deepening and widening. This is illustrated
by the following proportionality relationship developed by Lane (Lane 1955):
(5)
With Qw the water discharge, Sb the bed slope, Qs the sediment discharge, and D50 the
median grain size of the bed sediments. From this relationship, it can be seen that by
increasing the water discharge with a constant bed slope and median sediment grain size,
the sediment discharge must increase. This increase in sediment supply is the result of
erosion of the bed, over-steepening of the banks, and the resultant bank failures. The
increased sediment load will deposit in the upper section of lower Welch Creek. The
6
• •
coarser fraction of the load will settle in the upper section of lower Welch Creek
(Highway 64 to M-4), thus raising the bed in this reach. This will result in over bank
flows occurring at lower discharges. Thus the increased peak flows resulting from
upstream urbanization will be attenuated by the higher potential for over bank flows in
the upper part of lower Welch Creek. The finer fractions may deposit in the lower reach
of the Creek (MT-4 through MT-I 0), thus having a beneficial effect of providing a cap
over the contaminated layers. Thus urbanization of the upper creek watershed will not
increase sediment mobility in the lower reaches of Welch Creek.
CONCLUSIONS AND RECOMMEND A TIO NS
The simulations of the IO and 25 year return storm events indicate that only when the
Roanoke River has a stage of 1.5 feet or less does the bed shear stress reach the critical
threshold limit for erosion (0.20 Pascal). As demonstrated in the earlier Welch Creek
modeling studies conducted in 200 I, the reach for which the bed shear stress values meet
or exceed 0.20 Pascal was between transects MT-7 and GT-15.
Over bank velocities resulting from hurricane recession flows ranged from 0.1 to 0.4 feet
per second. Flows of this magnitude would not be expected to erode or entrain wetland
soils, particularly those covered with organic debris.
The future development and urbanization of the upper Welch Creek watershed will
impact the stability of the creek thus changing the sediment load delivered to the lower
reaches of Welch Creek. Although higher creek discharge and peak flows are to be
expected, the changes in creek morphology due to increased sediment delivery will
attenuate these impacts, thus the potential for increased sediment mobilization in the
lower creek is considered very low.
Modeling results indicate that the reach of Welch Creek adjacent to transect MT-10 is
stable and at a low risk for sediment mobilization.
The worst-case scenario of Welch Creek bed erosion depth is for the 10 and 25-year
return flood events assuming a Roanoke River stage of 0.9 feet ms!. An assumption of
higher Roanoke River stage will result in lower bed shear stress values and ·subsequently
lower erosion depths.
The results of this and previous studies indicate that the reach of Welch Creek bracketed
by transects MT-7 and GT-I 5 has the highest potential for sediment mobilization due to
either tidal or return flood events. It is recommended that remedial or mitigation actions
be directed to this reach of the creek.
7
• •
REFERENCES
Lane, E.W., Design of Stable Channels, Transactions of the American Society of Civil
Engineers, Vol 120, pp 1234-1279.
Scott, S.H., Sediment Mobilization Potential in the Roanoke River and Welch Creek, NC,
ERDCWES Technical Report, September-200 I.
Scott, S.H., Sediment Erosion and Transport Potential in Welch Creek, Technical Note to
EPA, April 2002.
Strickler, A., Beitraezo zur Frage der Gerschwindigheits Formelund der
Rauhigkeitszahlenfuer Strome Kanale und Geschlossene Leitungen, Mitteilungen des
Eidgenossischer Amtes fuer Wasserwirtschaft, Bern, Switzerland, 1923.
j
8
• •
Roanoke River
-6.5
-9.0
-11,5
-14.0
-16.5
-19.0
' Hwy 64 Bridge
Figure I. Modeled area of Welch Creek -bed elevation
9
• •
Figure 2. Model numerical mesh for Welch Creek-3585 elements and 9185 nodes
•
Shear Stress -Pa
■ I 0200
·-0.150
0.100
0.050
•
Figure 3. Maximum bed shear stress contours in Welch Creek for a IO-year flood event
and a 0.9 ft Roanoke River stage
11
• •
Shear Stress • Pa
■ 0.200 I 01W
I ,,oo
0.050
Figure 4. Maximum bed shear stress contours in Welch Creek for a I 0-year flood event
and a 1.5 ft Roanoke River stage
12
• •
Shear Stress -Pa
0.150
Figure 5. Maximum bed shear stress contours in Welch Creek for a I 0-year flood event
and a 2.0 ft Roanoke Ri vcr stage
13
• •
Shear Stress -Pa
0.200
0.150
Figure 6. Maximum bed shear stress contours in Welch Creek for a I 0-year flood event
and a 2.5 ft Roanoke River stage
14
• •
Shear Stress -Pa
0.200
0.150
I 0.100
. .
■ 0.050
Figure 7. Maximum bed shear stress contours in Welch Creek for a 25-year flood event
and a 0.9 ft Roanoke River stage
15
• •
Shear Stress -Pa
0.200 I 0150
I 0.100
■ 0.050
Figure 8. Maximum bed shear stress contours in Welch Creek for a 25-year flood event
and a 1.5 fl Roanoke River stage
16
• •
Shear Stress -Pa
. ; 0.200
0.150
0.100
Figure 9. Maximum bed shear stress contours in Welch Creek for a 25-year flood event
and a 2.0 ft Roanoke River stage
17
• •
Shear Stress -Pa I ,.,oo
0.150
0.100
0.050
Figure 10. Maximum bed shear stress contours in Welch Creek for a 25-year flood event
and a 2.5 fl Roanoke Ri vcr stage
• •
Velocity -ft/s
I 0.400
0.350
0.300
0.250
0.200
I 0.150
0.100
Figure 11. Maximum recession flow velocity contours in Welch Creek for the Hurricane
Dennis event
19
November 6, 2003
Integr,A
Envin:S,,tal
Solutions • 100 Verdae Bl,d. 29607-3825
P.O. llox 16778 29606-6778
Greenville, SC
Telephone: [phone]
Fax, 864-281-0288
·.I,
Mr. Randy Bryant
Remedial Project Manager i.l .11 t
United States Environmental Protection Agency
North Site Management Branch
61 Forsyth Street, SW
Atlanta, Georgia 03303-3140
'I
:. , ~ : NOV -7 2003
---------j
~ .. ,,-.,•·nr·1""• ,,-,-·,r ,'i l I'. '. ' .. [ ' d\! JJ ~ ,-I~ I ; I •
Subject: Employee Questionnaire Regarding Placement of Wastewater Treatment Solids
Former Hog Fuel Storage Area
Operable Unit #1-Landfill No. 1 Area
Weyerhaeuser Company
State Road 1565, Martin County, North Carolina
Dear Mr. Bryant:
As required in the signed Consent Decree and Statement of Work and identified in the approved
Remedial Design (RD) Work Plan, attached for your review and comment is a questionnaire for use as
part of the Landfill RD data collection activities. As you may recall or may have discussed with
Jennifer Wendel, after the Public Meeting on the Proposed Plan for the Landfill No. 1 area, additional
anecdotal information was uncovered by Weyerhaeuser Company (Weyerhaeuser) that supported a
possible change in the area requiring cover within the existing Landfill No. 1 footprint. Specifically,
Appendix A-Responsiveness Summary of the Record of Decision, Remedial Alternative Selection for
Landfill No. 1 Area, Operable Unit #1, Weyerhaeuser Site, Martin County, North Carolina, reflects a
comment made by Weyerhaeuser during the Public Comment for the Proposed Plan for Landfill
No. 1 Area addressing this issue. In the comment, Weyerhaeuser stated that several employees
volunteered additional information that wastewater treatment solids may not have been placed in the
portion of the landfill area known as the Former Hog Fuel Storage Area. As a result of the comment,
United States Environmental Protection Agency (USEPA) acknowledged the need to refine the exact
borders of the landfill during the RD phase in the Record of Decision. Therefore, during the initial
implementation activities of the RD, formal interviews of employees who may have additional
information regarding past site activities will be conducted to further refine the limits of Landfill
No.1.
Attached is a proposed questionnaire that will be completed during the interviews with individual
employees. We expect to interview up to six Weyerhaeuser employees. Bill Morris of Weyerhaeuser
and I will contact you in the next few days to discuss the interview and field sampling schedule.
I:\ WPGVL \l'JT\00--05115\04 \1.000511504--004.DOC
!) I
•
Mr. Randy Bryant
. United States Environmental Protection Agency
November 6, 2003
Page2
Sincerely,
RMT North Carolina, Inc.
~~v~
Michael B. Parker, P.E.
Senior Project Manager
•
Attachments: Employee Questionnaire Regarding Placement of Wastewater Treatment Solids
Site Map-Landfill No. 1 Area
cc: Bill Morris, John Gross, Mike Edwards, Weyerhaeuser Company
/ Nile Testerman,'j'-JC DENR
Kathy Huibregtse, RMT
Central Files
I:\ Wl'GVI. \PJT\00--05115\04 \ IJXl0511504-004.DOC
:; • •
Remedial Design Workplan for Operable Unit No. 1 (Landfill No. 1)
Weyerhaeuser Company-Plymouth, North Carolina
Employee Questionnaire Regarding Placement of Wastewater Treatment Solids at the
location known as the Former Hog Fuel Storage Area
In a document known as the Record of Decision, the United States Environmental Protection
Agency (USEPA) provided the selected remedial alternative for Landfill No. 1. This alternative
requires placement of a capping system on Landfill No. 1. Weyerhaeuser submitted comments
on the Record of Decision because several Weyerhaeuser employees volunteered additional
information that wastewater treatment solids might not have been placed in the location known
as the Former Hog Fuel Storage Area (as identified on Figure 4-1 of the Remedial Design (RD)
Workplan). If this location does not contain wastewater treatment solids, then placement of a
cover system in this area may not be necessary. As a result of the comments Weyerhaeuser
submitted, USEPA has allowed additional investigation to determine if wastewater treatment
solids were placed at the Former Hog Fuel Storage Area. This investigation includes
conducting employee interviews and collecting samples. The information that you provide will
be incorporated into a report for USEPA, and will assist us in determining whether wastewater
treatment solids were placed at this location.
.... -. ~. -" ·_,." ' ·::,~ q . ~,-,., ·; ·-,,.. ~ !':~: '"C:_,,i'"" .\f::•0 .... , 1;:,s;,;;• .·::.t""""·· ' ':,):..:-~ ;: ··1•_-'. ' :.;,. . ' . 'K '<:< .,·(;,; '
Employee Identification Number
Duration of Employment at Weyerhaeuser,
Plymouth, North Carolina.
General description of job responsibilities from
approximately 1981 to 1985.
What do you remember about the condition of
Landfill No. I in 1981?
What do you remember about the placement of
wastewater treatment sludge being used as a cover
material for Landfill No. 1?
What areas of Landfill No. 1 were covered with
wastewater treatment solids?
Do you have any other knowledge or information
about Landfill No. 1 that may be important in the
design of the required cover system?
I:\ WI'GVL \PJT\00-051 J5\04\Z00051150-t-OOJ.DOC 11/06/03
0 500
' - ---1000 1500
SCALE: 1"=500'
LEGEND
:woo
APPROXIMATE LANDFILL LIMITS
A Weyerhaeuser
PROJECT: WEYERHAEUSER PAPER COMPANY
PLYMOUTH, NORTH CAROLINA
LANDFILL No. 1 AREA
SHEET TITLE:
DRAWN BY1 OMC SCALE1
l.'.C:.:HE::C:.:K.:.E.:Dc.B:..Y-,-==---AS NOTED
a..:•::.PP.:..::RO;::V.::E:c:Dc....:Bc.cY.c, -----, DATED PRINTE01
DATE1
liMI.
NORTH CAROUNA, INC.
PROJ. NO. SUS.03
FILE NO.
f{){) V9rd11• 8/VQ,
GreenvflltJ, SC 29607-3825
P.O. Sox 16778 29808-8778
Phon•: 86-f-281-0030
Fax: [phone]
j:/cad/5115/03/s era tch.dgn
825 Diligence Drive, Suite 205
Newport News, Virginia 23606
tel: [phone]
fax; 757 596-2694
June 30, 2003
Ms. Beth Walden
Remedial Project Manager
U.S. Environmental Protection Agency
Atlanta Federal Center
61 Forsyth Street, S. W.
Atlanta, Georgia 30303-3104
PROJECT:
DOCUMENT NO:
EPA Contract No: 68-W5-0022
Work Assignment-930-RICO-041B
3282-930-RI-RIRT-1754]
•
·, \
' '
' : I JUL l.
'·
SUBJECT: Revised Final Remedial Investigation Report, Lower Roanoke River
Martin, Washington and Bertie Counties, North Carolina
Dear Ms. Wendel:
CDM FEDERAL PROGRAMS CORPORATION (CDM) is pleased to submit three copies of
the Revised Final Remedial Investigation (RI) report for the Lower Roanoke River Sh1dy. The
report incorporates revisions based on Weyerhaeuser Company comments on the Final RI
( dated June 2002), additional catfish ,data from location 436, as well as revisions in the
recently-submitted Human Health and Ecological Risk Assessments.
If you have any questions concerning the attached, please call me at [phone], ext. 225.
Sincerely yours,
CDM FEDERAL PROGRAMS CORPORATION
,,Y~//4 . .,_ /
Lynne J. France
Project Manager
Attachment
cc: Robert P. Stern, EPA Project Officer w / o attachment
Phil Vorsatz, EPA Region 4
Jennifer Wendel, EPA Region 4
Sharon Thoms, EPA, Region 4
Bobby Lewis, EPA, SESD
Tom-Augspergey,_US.EWS ______ ~
CNile.Testerinan,~oJJ::Jprth Carolina . rr
Dr. Luanne Williams, State of North Carolina
Michelle Vollasin, State of North Carolina
Kim Miller, USGS
Dr. Stephen Scott, USACE, WES
Weyerhaeuser Document Control
consulting • engineering • construction • operations
lntegra. • ; ~;-',. 'r.
744 I-le,lrrbnd Trnil 53717-1934
Enlliron ital
Solutions
June 26, 2003
Ms. Beth Walden
Remedial Project Manager
USEPA Region IV
61 Forsyth Street, SW
Atlanta, GA 30303-3104
l'.O. Box 8923 .B708-8923
,\,taJison, \X'I
Telephone: MlS-831-4444
Fax: <"JOS-83 1-3334
\\'WW.rmrinc.com
Subject: Sediment Coring and Fine Interval Sampling Results Report, Lower Roanoke River,
Weyerhaeuser Plymouth Mill, P;Iymouth, North Carolina
Dear Ms. Walden:
On behalf of the Weyerhaeuser Company (Weyerhaeuser), enclosed for your review and consideration is the
Sediment Coring and Fine Interval Sampling Results Report for the Lower Roanoke River (LRR) study area.
An executive summary of this report was sent to you on October 31, 2002. This report supplements the ongoing
LRR Remedial Investigation/Feasibility Study (RI/FS) activities being led by the United States Environmental
Protection Agency (USE!' A).
The LRR RI includes a number of sediment coring locations that have lower concentrations of dioxins/furans
and mercury indicating possible burial by less impacted sediment. Therefore, this study was developed to
funher evaluate the ve11ical distribution of constituents within the sediment profile.
The sediment coring and fine interval sampling assessment provides site-specific data concerning sediment
chemistry for nine locations in the Roanoke River. At five of the nine locations, subsampling of the sediment
cores at small increments (fine-layer sampling) was performed to better define the distribution of chemicals of
potential concern (COPCs) with depth. These locations are generally consistent with sample locations assessed
by the USEPA during the RI data collection activities. As such, the enclosed information augments the
agency's data.
The sediment coring and fine interval sampling assessment clearly shows burial of COPCs by cleaner sediment.
Burial in the range of 0.2 to 0.8 feet below the sediment surface was observed at all fine-layer coring locations.
In most cases, the elevated COPC zone is below the biologically active sediment layer. These data establish that
the biologically active surficial layer and near-surface sediment (i.e., top 0.5 foot) are recovering through natural
sediment deposition and accumulation. This ongoing accumulation of cleaner sediment in conjunction with the
protected dam,controlled 1low system of the Lower Roanoke River appears to provide a stable environment for
the natural recovery of the river system.
!: \ Wf>MSN \l'JT\00-05112\25\l.000511225-008.DOC
~/ff
-J
Ms. l3cth Walden
USEPA Region IV
June 26, 2003
Page 2
• •
The enclosed data report provides additional information and a more detailed discussion of the results presented
in the summary memorandum (October, 2002). Weyerhaeuser believes that these supplemental data and
findings arc valuable for understanding the Roanoke River system. We greatly appreciate your consideration of
this matter.
Sincerely,
RMT. Inc.
~;1.111~
Stacy A. McAnulty, P.E.
Senior Project Manager
Enclosure
cc: Mr. Philip Yorsatz, USEPA Region 4
Ms. Jennifer Wendel, USEPA Region 4
Mr. Nile Testerman, North Carolina Depa11ment of Environmental and Natural Resources
Mr. Jeff Welti, North Carolina Department of Environmental and Natural Resources
Mr. John Gross, Weyerhaeuser Company
Ms. Kathryn Huibregtse, RMT
I:\ Wl'/l.lSN\J'J'J'\00-05112\25\L000511225·008.00::
-NORTH CAROLINA • DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WASTE MANAGEMENT
MICHAEL F. EASLEY, GOVERNOR
WILLIAM G. Ross, JR., SECRETARY
DEXT.ER R. MATTHEWS, DIRECTOR
19 June 2003
Ms. Jennifer Wendel
Supcrfund Branch, Waste Management Division
US EPA Region IV
61 Forsyth Street, S. W.
Atlanta, Georgia 30303
SUBJECT: Review of Sediment Quality Triad Assessment
Roanoke River
Weyerhaeuser Company
Manin County
Dear Ms. Wendel:
•
The State of North Carolina has reviewed the Sediment Quality Triad Assessment, Roanoke
River received by the Di vision on 29 April 2003. The following comments are offered:
Attached are comments by Ms. Trish Finn MacPherson from the North Carolina Division of
Water Quality. In addition, Ms. Sandy Mon submitted in an email the following comments:
"Regarding the sediment toxicity, I would caution -that although they found no statistically
significant reductions in survival, and the more sensitive endpoint of growth, this does not
necessarily represent a similar lack of potential toxic effects to the still more sensitive production
endpoint. Toxicity that negatively impacts reproduction will have obvious, potentially serious,
ecosystem impacts. Toxicity endpoints are generally evaluated in longer-term chronic tests that
cover a reproductive cycle of the organism, in this case 28-42 days." She also stated in a later
email that "My only caution is the concern expressed in my previous email, re: using growth
endpoints as a surrogate for long-term reproduction capacity, although the benthic assessment
would provide some indication of community/ population reproductive problems."
If you have any questions, please call me at 919-733-2801 ext. 350.
Sincerely,
--P)~
Nile P. Testerman, P.E.
Environmental Engineer
1646 MAIL SERVICE CENTER, RALEIGH, NORTH CAROLINA 27699-1646
401 OBERLIN ROAD, SUITE 150, RALEIGH, NC 27605
PHONE: [phone] \ FAX: [phone]
AN E0UAL OPPOATUNJTY/AFFIRMATIVE ACTION EMPLOYER· 50% RECYCLED/10% POST•CONSUMEA PAPER
•
Memorandum To: Jimmie Overton
Sandy Mort
• Division of Water Quality
Biological Assessment Unit
June 6: 2003
From: Trish Finn lvlacPherson
Subject: Review of benthos data in "Sediment Quality Triad Assessment, Roanor,e River" Weyerhauser Company, April 2003
Consultants for Weyerhauser sampled the lower RoanokE: River and thE: lv1'1ddle River (waterbody that splits off from the Roanoke and flows down the other side of Huff Island to Albemarle Sound) for benthos in May 2001, using a dip net for qualitative bank and shallow water sampling, and a petite ponar for deep water sampling. Their results suggests no differences in the benthic community above, near, or below the mill in Plymouth, or between the Roanor,e River and the Middle River. DWQ sampled the Roanoke River slightly below their most downstream stations (RR08L and RR08R) in 1985, 1990 and 19ll4.
Comparison of our data with the downstream benthos data in the report, which states that sampling was consistent with our sampling methods, suggests substantial differences either in sampling method or changes in the community since DWQ last sampled. In the 1990's DWQ collected 9 and 10 EPT taxa, however in 2001 the EPT richness number was 3 at RR08R and 1 at RR08L. Very high numbers of oligochaetes were collected at all sites in 2001, but DWQ has never found such high numbers and typically collect few oligochaetes. Very high numbers of chironomids were also collected in 2001, and again DWQ has never collected such high numbers. Such high numbers of worms and chironomids indicate the sweep sampling focussed on bottom deposits rather than the snags and banks in DWQ sampling. Despite these differences, if the taxa list for all the 2001 sites is compared with DWQ taxa list for relatively outdated samples, the same taxa in general are being found now as in the past. One noteable difference is the mayfly, Stenacron interpunctatum, which was not collected anywhere in 2001, but was abundant in all DWQ samples.
If it is assumed that sampling in 2001 was consistent at all sites, and there is no reason not to assume this, then the conclusion that there is a similar benthic community at all the sites is a reasonable one, exce;:,t that RRiO is clearly the worst site. When worms, chironomids and amphipods make up between 71 % and 98 % of the benthic abundance, then very enriched conditions are present, and a very tolerant community exists. This is what the report concludes also.
I have several minor comments relating to use of NC DWQ methods and metrics:
Section 6, page 14 -Would disagree with the statement that most benthos collections produce voluminous data sets.
A;:,pendix E -Table 3-2 notes that the NCBI classifications for Coastal A streams was used to determine the NCBI descriptor (Poor or Fair), yet these sites are considered Coastal 8 by DWQ and so Coastal A criteria should not have been used. This does not change conclusions.
t was confused by the iold out taxa table in Appendix E labelled di;:,net data. This appears to be an incomplete summary of Table 3-1 (though in a mo,e user friendly format). The samplers also appear to ::,e confused, as both the dipnet and ponar tables are labelled "Roanoke River, VA"'!
C
June 17, 2003
lntegrat.A
Enviro,z~al
Solutions
Ms. Beth Walden
Remedial Project Manager
USEP A Region IV
61 Forsyth Street, SW
Atlanta, Georgia 30303-3104
Dear Ms. Walden:
• 744 Heartla~'~ 93,f 'J / (j
P.O. Box 8923 53708-8923
Madison, WI
Telephone: [phone]
Faxc 608-831-3334
On behalf of the Weyerhaeuser Company (Weyerhaeuser), enclosed for your review and
consideration is the Lower Roanoke River (LRR) Wildlife and Vegetation Surveys Report that
provides supplemental information to the ongoing LRR Remedial Investigation/Feasibility Sh1dy
(Rl/FS) activities. These supplemental data were collected to aid in the evaluation of whether wildlife
and vegetation populations along the LRR system have been adversely impacted.
The wildlife and vegetation surveys were conducted in May 2001 for the LRR sh1dy area. A specialty
subcontractor, Springbom Laboratories, Inc., performed the surveys. These qualitative surveys were
conducted along the banks of the LRR near the town of Plymouth, North Carolina. Survey stations
that generally correlated with the USEPA wetland soil sampling locations (Baseline Ecological Risk
Assessment LRR Study [USEPA, June 2002]) were established along the banks of the Roanoke River
within the USEP A's sh1dy area. These areas were also coincident with transect locations identified in
the Sediment Quality Triad Assessment Report (RMT, April 2003) for benthic sampling. Prior to
initiation of the surveys, species and habitat information for the Lower Roanoke River area was
obtained from various sources, including the Roanoke River National Wildlife Refuge. The habitat
and species information available from the literahire was used for comparison purposes in order to
assess habitat quality in the LRR study area.
Seventeen (nine upstream and eight downstream) survey stations were established along both the left
and right bank of the approximate 12-mile stretch of the LRR sh1dy area, from upstream of the
Weyerhaeuser facility, down to the Highway 45 Bridge. The wildlife surveys were concentrated on
bird species, but included incidental observations or evidence of mammals, amphibians and reptiles.
The vegetative survey assessed the flood plain vegetation at 17 riverside sites and five inland sites.
A total of 42 bird species were identified during the 5-day survey. These included abundant,
common, uncommon, and occasional species, following the abundance categories used by the
Roanoke National Wildlife Refuge. The survey was conducted dming the nesting season for avian
species. Many of the birds observed were considered resident breeders or NeolTopical migrants.
Additional species may be present during the fall and spring migration period. The species observed
during the smveys were anticipated to be in the sh1dy area and were noted on the Roanoke River
National Wildlife Refuge bird species list. No state or federally listed threatened or endangered avian
species were recorded. Swamp habitat in the LRR sh1dy area was clearly very productive for some
Neotropical migrant species.
J: \ Wl't.1SN \PJT\00-05112\25 \ LOOOS 11225-007 .IX>C
Ms. Beth Walden
USEP A Region IV
June 16, 2003
Page2
• •
Observations of mammals and herptiles and/ or their respective signs were recorded during the
surveys. Several mammalian species were observed along the LRR banks during the surveys. Turtles
were very abundant along the river shoreline. Two species of snakes were also observed.
Vegetation surveys consisted of an assessment of flood plain vegetation growing along the shoreline,
and up to 40 meters into the adjacent wetland areas at select stations. The dominant'canopy, shrub-
layer, and ground-layer species were recorded at each survey location. Overall, the survey data
verified that most of the vegetation observed along the LRR matches the classifications identified in the
literature. There was a lack of congmence among five inland sampling stations. However, this may be
because the subsidiary sampling points were not located far enough inland into a transition zone
(owing to physical barriers or property owner boundaries) or because too few sampling points were
established/investigated to make the sample quantitatively comparable. No threatened or endangered
plant species were observed during the survey. According the United States Fish and Wildlife Service,
no federally threatened or endangered plant species are currently listed for Bertie, Martin, or
Washington Counties. Two state-listed plant species (Schizandra glabra and Lilaeopsis carolinsis) are
reported in Martin and Washington Counties; however, these species were not observed in the study
area.
The wildlife and vegetation surveys indicated that the habitat quality is apparently excellent based on
the munerous avian species observed and the historical and current land use for the sh1dy area. The
observed wildlife and vegetation are representative of nahiral habitat requirements for wildlife
populations expected to exist in the LRR system. These supplemental qualitative survey data are
useful in evaluating whether wildlife and vegetation populations along the .LRR system have been
significantly and adversely impacted.
The enclosed report provides a full account of the survey details and results. Weyerhaeuser believes
that this supplemental information is valuable for understanding the overall Lower Roanoke River
ecological system. Please contact either Weyerhaeuser's project manager John Gross (253/924-4190)
or Stacy McAnulty (608/662-5195) if you have any questions regarding this report.
Sincerely,
RMT, Inc.
~~u~~E~
Senior Project Manager
Enclosure
cc: Mr. Philip Vorsatz, USEPA Region 4
Ms. Jennifer Wendel, USEPA Region 4
Mr. Nile Testerman, North Carolina Department of Environmental and Nah1ral Resources
Mr. Jeff Welti, North Carolina Department of Environmental and Nah1ral Resources
Mr. Chuck Gibson, Weyerhaeuser Company
Mr. John Gross, Weyerhaeuser Company
Mr. Martin Lebo, Weyerhaeuser Company
Ms. Kathryn Huibregtse, RMT
I:\ Wl'1'.1.SN\PJT\00-051 l 2 \25\ L00051122S-007.DOC
•
Memorandum To: Jimmie Overton
Sandy Mort
•
Division of Water Quality
Biological Assessment Unit
June 6, 2003
From: Trish Finn l✓iacPherson
Subject: Review of benthos data in "Sediment Quality Triad Assessment, Roanc:,i;e River" Weyerhauser Company, April 2003
Consultants for Weyerhauser sampled the lower Roanoke River and the Middle River (waterbody that splits off from the Roanoke and flows down the other side of Huft Island to Albemarle Sound) for benthos in May 2001, using a dip net for qualitative bank and shallow water sampling, and a petite ponar for deep water sampling. Their results suggests no differences in the benthic community above, near, or below the mill in Plymouth, or between the Roanoke River and the Middle River. DWO sampled the f'<oanoke River slightly below their most downstream stations (RR08L and RR08R) in 1985, 1990 and 1994.
Comparison of our data with the downstream benthos data in the report, which states that sampling was consistent with our sampling methods·. suggests substantial differences either in sampling method or changes in the community since DWO last sampled. In the 1990's DWO collected 9 and 10 EPT taxa. however in 2001 the EPT richness number was 3 at RR08R and 1 at RR08L. Very high numbers of oligochaetes were collected at all sites in 2001, but DWO has never found such high numbers and typically collect few oligochaetes. Very high numbers of chironomids were also collected in 2001. and again DWO has never collected such high numbers. Such high numbers of worms and chironornids indicate the sweep sampling focussed on bottom deposits rather than the snags and banks in DWO sampling. Despite these differences, if the taxa list for all the 2001 sites is compared with DWO taxa list for relatively outdated samples, the same taxa in general are being found now as in the past. One noteable difference is the mayfly, Stenacron interpunctatum, which was not collected anywhere in 2001, but was abundant in all DWO samples.
If it is assumed that sampling in 2001 was consistent at all sites, and there is no reason not to assume this, then the conclusion that there is a similar benthic community at all the sites is a reasonable one, except that RR10 is clearly the worst site. When worms, chironomids and amphipods make up between 71 % and 98 % of the benthic abundance, then very enriched conditions are present, and a very tolerant community exists. This is what the report concludes also.
I have several minor comments relating to use of NC DWO methods and metrics:
Section 6, page 14 -Would disagree with the statement that most benthos collections produce voluminous data sets.
Appendix E -Table 3-2 notes that the NCBI classifications for Coastal A streams was used to determine the NCBI descriptor (Poor or Fair), yet these sites are considered Coastal B by DWQ and so Coastal A criteria should not have been used. This does not change conclusions.
I was confused by the fold out taxa table in .4ppendix E labelled dipnet data. This appears to be an incomplete summary of Table 3-1 (though in a mo,e user friendly format). The samplers also appear to be confused, as both the dipnet and ponar ta:iles are labelled "Roanof-e River, VA" ! !
RM[ lntegr.
Env;ro, ital
Soluti011s
April 28, 2003
Ms. Beth Walden
Remedial Project Manager
USEP A Region IV
61 Forsyth Street, SW
Atlanta, GA 30303-3104
• 744 1--lcartlaml Trail 53717-1934
P.O. Hox 8923 53708-8923
.\fadison, \VI
Tdeph(mt': 608-831-4444
Fax: [phone]
{ -::--::----~~·:w.rmtinc.com
1. t ! : . f,c; lc; /F-f-1v;·1e·-
1 • . , --: . •--'.J !-~ ., i I
i I ) .
; ,.1 i. APR 2 9 2003 I I
I ' . l ~I,~~~--~~-~;~--: ... _~ .. --~--..
--•-. • I/ t...,' / ', j (,, , ,·•··, 1.-, . . I '
Subject: Sediment Quality Triad Assessment Report for the Roanoke River, Weyerhaeuser
Company, Martin County, North Carolina
Dear Ms. Walden:
On behalf of the Weyerhaeuser Company (Weyerhaeuser), enclosed for your review and
consideration is the Sediment Quality Triad Assessment Report for the Lower Roanoke River (LRR)
study area. An executive summary of this report was sent to you on October 31, 2002. This report
supplements the ongoing LRR Remedial Investigation/Feasibility Study (RI/FS) activities being led
by the United States Environmental Protection Agency (USEPA).
The sediment quality triad (SQT) assessment, conducted in May 2001 for the LRR study area, follows
the USEPA's protocols for an effects-based, weight-of-evidence approach. This assessment provides
site-specific, co-located data concerning surficial sediment chemistry, sediment toxicity, and benthic
community structure for 14 locations in the Roanoke River and three locations in the Middle River.
These locations are generally consistent with sample locations and collection dates assessed by the
USEPA during the RI data collection activities. As such, the enclosed information augments the
agency's data.
The sediment quality triad assessment indicates that, irrespective of location and the presence or
absence of sediment contaminants, the LRR benthic community is representative of the nahiral river
system. The SQT assessment of the LRR shows no indication of toxicity to laboratory organisms or
alteration or degradation of the indigenous benthic macroinvertebrate community from four
constituents of potential concern (dioxin, mercury, copper, and pentachlorophenol). This finding is
based on both the laboratory bioassays of Roanoke River sediment and the in situ benthic community
surveys. Given the complexity of the issues present in the Lower Roanoke River (e.g., salt water
intrusion, water ejevation changes due to proximity to the Sound, etc.), direct evaluation of benthic
community metrics is essential to developing reliable risk-based decisions. These supplemental LRR
data are also useful in evaluating whether there are significant impacts to the Roanoke River system
from chemicals present in sediment within Welch Creek.
I:\ Wl'MSN\PJT\00-05112\25\LOOOSI J225-004.l:XX
Ms. Beth Walden
USEP A Region IV
April 28, 2003
Page 2
• •
The enclosed data report provides additional information and a more detailed discussion of the
results presented in the summary memorandum (October, 2002). Weyerhaeuser believes that these
supplemental data and findings are valuable for understanding both the Roanoke River and Welch
Creek systems. We greatly appreciate your consideration of this matter.
Sincerely,
RMT, Inc.
~q<J.mc~
Stacy A. McAnulty, P.E.
Senior Project Manager
Enclosure
cc: Mr. Philip Vorsatz, USEPA Region 4
Ms. Jennifer Wendel, USEP A Region 4
Mr. Nile Testerman, North Carolina Department of Environmental and Natural Resources
Mr. John Gross, Weyerhaeuser Company
Ms. Kathryn Huibregtse, RMT
I:\ WPMSN\l'/T\00-05112\25\L00051 l2Z5--004.1XJC
lntegr.
Enuin; ·ntal
Solutions
September 25, 2002
Ms. Jennirer Wendel
Remedial Project Manager
United States Environmental Pro1eetion Agency, Region IV
61 Forsyth Street, SW
Atlanta, GA 30303-3104
Subject: Drart Revision 2 -Remedial Investigation Report
Welch Creek
Weyerhaeuser Company, Martin County, North Carolina
Dear Ms. Wendel:
• 744 Heartland Tr"ail 53717-1934
P.O. Box 8923 53708-8923
i\ladison, W!
Telephone: 608-:D 1-4444
Fax, 608-8Jl-lll4
On behalf of Weyerhaeuser Company (Weyerhaeuser), RMT, Inc., (RMT), is submitting the enclosed Draft
Revision 2 Remedial Investigation (RI) Report for the Welch Creek area. This document incorporates the
USEPA's review comments dated November 13, 2001, the agreements that were reached in our February 26,
2002, meeting, and additional discussions with USEPA technical reviewers. This document is required by the
Administrative Order by Consent (Docket No. 98-10-C) dated March 24, 1998.
Two copies of the RI report for the Welch Creek area are enclosed for your review and approval. One copy or
the document has been submitted directly to Mr. Nile Testerman at the North Carolina Department of
Environment and Natural Resources (NCDENR), to Mr. Tom Augspurger of the U.S. Fish and Wildlife Service,
and to Sharon Thoms of USEP A. Two copies of the Draft Revision 2 RI have been directly submitted to Lynn
France of CDM Federal.
Please review and approve the enclosed report. If you have any questions, please call.
Sincerely,
~~~---
K,~
Scmor Project Manager
~-/~J~e-1_, .
Kathry t. Hu1bregtse /td>ic___
Principal-in-Charge
Attachments: Draft Revision 2 Remedial Investigation Report Welch Creek Area (Volumes I and 2)
cc: Mr. Nile Testerman, NCDEHNR
Mr. Tom Augspurger, US Fish and Wildlife Service
Ms. Lynn France, CDM Federal
Ms. Sharon Thoms, USEPA
Mr. Rodney Proctor, Weyerhaeuser Company
Mr. Steve Woock, Weyerhaeuser Company
Mr. Jeff Stamps, Weyerhaeuser Company
I:\ Wl'MSN \ PJT\00-05100\44 \ LOOOS l 0044-020, rx:x:
Southern Envimnmento\ Field Station.
A Weyerhaeuser
Dear Mr. Vorsatz:
• PO Box. 1391
New Bern, North Carolina 28563-1391
ph. 252-633-7279 fa, 252-633-7634
Subsequent to meeting with the USEPA in June 2002, Weyerhaeuser Company (Weyerhaeuser) received
a letter from Ms. Jennifer Wendel requesting sediment data that was collected by Weyerhaeuser from the
Albemarle Sound during 1996-1997. The reques1ed information is provided in the first enclosure, titled
"Albemarle Sound Sediment Characterization and Dioxin/Furan Study, Sample Collection and Data
Listing Summary." This enclosure was prepared in response to USEPA's data request since the project
information previously had not been compiled for distribution. You should note that the project was
undertaken for internal use and although sample collec1ion and analytical procedures were of high
quality, the project was not explicitly designed to meet specific EPA data quality objectives.
Also enclosed for your information is a memo that our contractor, RMT, Inc., prepared for
Weyerhaeuser. This memo summarizes a preliminary screening of the Albemarle Sound sediment data
with remedial goal objectives derived from CDM's Baseline Ecological Risk Assessment for the Lower
Roanoke River. The referenced CDM document was prepared for the USEPA and is dated June 5, 2002.
Weyerhaeuser believes the comparisons give some perspective to the Albemarle Sound data, despite the
obvious uncertainties in extrapolating from the exposure models used for the river to conceptually
accurate models for the sound.
Should you have any questions please do not hesitate to call.
Sincerely,
WEYERHAEUSER COMPANY
~6fLSCJoo4-
stephen E. Woock
Aquatic Scientist/Field Station Manager
Encls/2
cc: Ms. Jennifer Wendel, USEPA
Ms. Beth Walden, USEPA
..M<'Nile Testerman, North Carolina Department of Environment and Natural Resources
Mr. Jeff Stamps, Weyerhaeuser
Ms. Karen Saucier, RMT, Inc.
• • .;N•~ Project Technical Memorandum
Date:
To:
From:
Cc:
Subject:
Introduction
September I 6, 2002
Steve Woock and Jeff Stamps
Karen C. Saucier and Heather Smith
Joe Jackowski, Kathy Huibregtse, Stacy McAnulty, Bernd Rehm and Kris Krause
Preliminary Screening of Albemarle Sound Sediment Data to Corrected Lower Roanoke
River RGOs
Sediment data collected by Weyerhaeuser for the Albemarle Sound in 1996 and 1997 was documented in the
Weyerhaeuser Southern Environmental Field Station Research Report entitled Albemarle Sollnd Sediment
Characterization and DioxinlFllran Swdy. Sample Collection and Data Listing Sllmmary. In an effort to review
these sediment observations in a conservative ecological risk-based context, Weyerhaeuser requested that RMT
conduct a preliminary screening level comparison of the dioxin/furan data for the Albemarle Sound sediments to
the corrected remedial goal options (RGOs) initially developed for the Lower Roanoke River Baseline
Ecological Risk Assessment (COM, 2002). This comparison should be considered a preliminary screening
assessment because of significant differences in the Roanoke River and Albemarle Sound ecosystems.
Modifications of the selected receptors and exposure assumptions to be more representative of the Albemarle
Sound would be necessary to develop site specific RGOs. However, the following comparison to these
corrected RGOs is expected to be a conservative and preliminary indication of potential ecological risks
associated with sediment dioxin concentrations.
Lower Roanoke River Remedial Goal Options with Corrections
Prior to initiating the screening level comparison, the RGOs for wildlife species presented in Lower Roanoke
River Final Baseline Ecological Risk Assessment Report (CDM, June 2002) were adjusted to address noted
errors in the relied upon dietary exposure models. In RMT' s Initial Technical Review Comments, Lower
Roanoke River, Final Base/i;,e Ecological Risk Assessment Report (CDM, lllne 2000), provided to the USEPA
on September JO, 2002, specific mathematical errors were identified in the dietary exposure modeling.
Adjustment of the models to address the corrections will result in a reduction of the Hazard Quotients for the
affected endpoints and a corresponding increase in the RGOs relative to those presented in the report.
The specifics of the RGOs calculations were not provided in the Lower Roanoke River BERA and in the
absence of the details, the RGO calculations could not be identically recreated. The modified RGOs should, as a
result, be considered an approximation. For the purpose of correcting RGOs for this screening level assessment,
the adjustments in dietary exposure modeling will include the following:
1. Dietary exposure modeling presented in the Lower Roanoke River BERA for upper trophic level endpoints
included a modeled ingestion of JOO percent of diet plus an additional percentage of sediment or soil
(typically 2 to 10.4 percent, depending on receptor). This approach clearly results in a daily dietary intake
of greater than 100 percent, which is not realistic. For the purpose of defining RGOs for this screening
level assessment, the dietary intake of the HQ/RGO equation will be adjusted to reflect 100 percent
total dietary intake.
I:\ WPMLW\PJT\00-05112\23\1'\000.il 1223-00LDOC
• • Project Technical Memorandum
2. Dietary exposure models for piscivorous endpoints incorporate inaccurately derived whole fish tissue
concentrations, derived by addition of fillets and carcass concentrations without correction for the relative
tissue weights and incorporate the suspect and anomalously high white catfish sample (RR436WCF). For
the purpose of defining RGOs for this screening level assessment, the dietary exposure model for fish
eating endpoints will be adjusted to reflect the next highest fish tissue result (LMB436-carcass).
3. The Lower Roanoke River BERA relics upon the results of a Nosek study on ring-necked pheasants ( 1992)
modified by additional uncertainty fac_tors in the assessment of potential avian risk from dioxin exposures.
As noted in the revised Final Baseline Ecological Risk Assessment for the Welch Creek Area,
Weyerhaeuser and RMT do not agree with this derivation of the avian toxicity reference value (TRY) for
dioxin. In recent interpretations, Oak Ridge National Laboratory (ORNL) researchers (ORNL, 1996) and
the USEPA in the Region 6 Hazardous Waste Combustor guidance (USEPA, 1998) characterized the Nosek
study as a chronic study or as not requiring application of an additional uncertainty factor. For the purpose
of defining RGOs for this screening level assessment, the toxicity reference value derived from the
Nosek (1992) study without the application of an additional uncertainty factor will be used.
Table I presents the corrected RGOs corresponding to both No Observed Adverse Effect Levels (NOAELs) and
Lowest Observed Adverse Effect Levels (LOAELs) for wildlife species.
Discussion of Screening Comparison
Table 2 presents a summary of Albemarle Sound sediment samples for which dioxin analytical results are
available and compares the data to the corrected RGOs. The dioxin/furan data was converted to 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalent concentrations (TEQs) for this screening level
comparison. TEQs for each sediment sample were calculated using World Health Organization (WHO) toxicity
equivalent factor (TEF) methodology for mammalian and avian species as presented in Van den Berg, et al.
(\998). The dioxin TEQs for sediment samples collected in 1997 include full congener analyses, however, the
1996 values are calculated using 2,3,7,8-TCDD and 2,3,7,8-tetrachlorodibenzofuran (TCDF), which were the
only congeners analyzed in that year's samples.
Figures l and 2, respectively, present a preliminary screening of dioxin TEQ results for sediment samples
collected in I 996 and 1997 in comparison to the LOAEL-, and NOAEL-based RGOs for mammals. No
observed dioxin TEQ in Albemarle Sound sediment samples are above LOAEL-based RGOs for mammalian
receptors. Only one of 19 surficial sediment samples (a deep water and central basin sample: ALBW-11 0-2"),
collected in 1997, contains dioxin TEQ at a concentration slightly greater than mammalian NOAEL-based RGO.
Figures 3 and 4 present a preliminary screening of dioxin TEQ results for sediment samples collected in 1996
and 1997, respectively, in comparison to the NOAEL-based RGOs for the most conservative avian species (barn
swallow). No observed dioxin TEQ in Albemarle Sound sediment samples are above LOAEL-based RGOs for
avian receptors. In addition, no observed dioxin TEQ in Sound sediment samples are above corrected NOAEL-
based RGOs for avian receptors.
· As depicted in Figures 2 and 4, samples from the sandy sediment areas, represented by shallow water sediment
samples WA-S3, WB-S2, and ALW-15, do not contain dioxin TEQ at concentrations greater than even the most
conservative NOAEL-based RGOs.
Figures 5 and 6 present a preliminary screening of dioxin TEQ results for multiple depth intervals at sediment
sample W A-D3 in comparison to LOAEL-, and NOAEL-based RGOs, for the mammalian receptor and most
conservative avian species, respectively. The core sample at WA-D3 indicates that cleaner sediment is being
2 I:\ WPML W\PJT \()(}.-05112 \23 \ M0005 i l 223-00 I. 0CX:
• • Project Technical Memorandum
accumulated in the upper interval of the core sample showing the potential mechanism for improvement in the
Sound ecosystem.
Additional Considerations
As presented in the introduction, this comparison should be considered a preliminary screening assessment
because the receptors and exposure assumptions represented in the RGOs developed for the Lower Roanoke
River environment may not be representative of the Albemarle Sound. However, application of Lower Roanoke
River exposure assumptions to the Sound environment represents a conservative screening evaluation because
of the differences in the habitat and wildlife species expected to be present in the two areas. In general, most
wildlife exposures (wading birds, diving ducks, semi-aquatic mammals) in the Sound are likely to occur in the
shallow margins of the Sound. As noted in the discussion above, the sandy sediments typical of this
environment contain very low concentrations of dioxin TEQ. For the open water areas of the Sound, wildlife
exposures are likely to be typified by fish eating birds such as the osprey and eagle. Limited exposure to
sediment is anticipated for these wildlife receptors which feed in deeper waters.
As noted on page 9-39 of the Lower Roanoke River Baseline Ecological Risk Assessment (COM, 2002), "While
the NOAEL-based RGO provides an estimate of the highest media concentration that would not result in
adverse effects to an ecological receptor, it does not provide information regarding the concentration where
ecological effects would be expected to occur." As such, presence of individual sample results above a
NOAEL-based RGO is not indicative of a potential adverse ecological risk.
Environmental data available for the Sound also provide evidence that conditions in the Sound are in the process
of natural recovery. Specific examples include:
■ As noted in the discussion above, the core sample at W A-D3 indicates that cleaner sediment is being
accumulated in the upper interval of the core sample showing the potential mechanism for improvement in
the Sound ecosystem.
■ Gamefish dioxin TEQs for the western Albemarle Sound have been below the State's 3 part per trillion
(ppt) advisory threshold value for a number of years. Because of this, and because of similar results for
Roanoke River and Welch Creek fishes, the North Carolina Department of Health and Human Services has
rescinded the consumption advisory for gamefish in the western Albemarle Sound.
■ Overall Fish trends -Tissue data for dioxin in fish from Albemarle Sound have been evaluated
independently by both Weyerhaeuser and USEPA (Dioxin Trends in Fish at Four Locations, USEPA,
October, 2001). Fish tissue data trends from 1989 to 1999 or 2001 were assessed. Decreasing dioxin TEQ
concentration trends have been evident since the early to mid 1990s for various fish species collected from
several locations in the Sound.
Summary of Conclusions
The following conclusions were drawn from this preliminary screening level comparison of the Albemarle
Sound sediments to the corrected Lower Roanoke River RGOs:
1. No sediment samples from the Sound contain dioxin TEQ at concentrations above corrected LRR LOAEL-
based RGOs for any receptor.
2. No sediment samples from the Sound contain dioxin TEQ at concentrations above corrected LRR NOAEL-
based RGOs for avian receptors.
3. Only one surficial interval (0 to 2") sediment sample from the deep water basin of the Sound contains .
dioxin TEQ at concentrations above corrected LRR NOAEL-based RGOs for mammalian receptors. Semi-
3 I:\ WPML W\ PJT\00-05112\23 \MOOO 511223-00 I. DCX:
• • Project Technical Memorandum
aquatic mammals are expected to have no direct contact with sediment in the deep water areas of the
Sound, and limited access to food organisms originating from there.
4. Samples from the sandy sediment areas, represented by shallow sediment samples that also reflect the
Sound areas of highest potential exposure, do not contain dioxin TEQ at concentrations greater than even
the most conservative NOAEL-based RGOs.
5. Deposition of cleaner sediment materials over more heavily impacted sediment is observed in the fine-layer
core sample that was collected during this limited investigation.
6. Sediment RGOs based upon the receptors evaluated in the Lower Roanoke River BERA provide a
conservative point of comparison for sediments from Albemarle Sound since the types of receptors and
their associated feeding patterns would reduce potential exposures to contaminated sediments.
The results of this conservative screening do not support significant additional investigative or remedial
activities to address ecological risk concerns for the Albemarle Sound.
4 I:\ WPMLW\PJT\00-05112\23\MOOOSl lnJ-oot.IXX
Barn Swallow
Wood Duck
Green Heron
Table 1
Lower Roanoke River RGOs -Corrected
54
350
1,130
1,200
540 Adjust dietary intake from 109 percent to l00 percent.
Replace White Catfish (WCF436 + WCC436) with next highest fish
tissue result (Laroemouth Bass carcass from Station 436).
3,500 Adjust dietary intake from l03 percent to 100 percent.
Consistent with Sample et al., (1996) and USEPA (1999),utilize
Nosek TRY without additional lOX uncertaint factor.
11,300 Adjust dietary intake from l06 percent to JOO percent.
Consistent with Sample et al., (1996) and USEPA (1999), utilize
Nosek TRY without additional IOX uncertaint factor.
12,000 Adjust dietary intake ram 102 percent to l00 percent.
Replace White Catfish (WCF436 + WCC436) with next highest fish
tissue result (Largemouth Bass carcass from Station 436).
Consistent with Sample et al., (1996) and USEPA (1999), utilize
Nosek TRY without additional !OX uncertainty factor.
i:\wpmlw\pjt\00·05112\23\AS_Sed_l.x!s\Table 1 RGOs • Corrected
•
•
• •
Table 2
Preliminary Screening Comparison of Dioxin TEQs in Albemarle Sound Sediment to
Lower Roanoke River Ecological RGOs for Dioxin TEQ
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11/14/96 P2663A OffMackey's GRAB 49.1 195.8
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11/14/96 P2664A Marker I ' X-SEC 55.8 219.6
Albemarle Sound @
11/14/96 P2665A Marker I X-SEC 49.4 166.4
Albemarle Sound @
11/14/96 P2666A Marker I X-SEC 40.5 153.9
Average of triplicate Albemarle Sound @
11/14/96 samples above Marker I 48.6 (a) 180.0"'
11/14/96 P2667A Chowan River X-SEC 19.1 54.9
11/25/97 P2951 WA-S3 0-2" 0-2" 0.140 0. 797
11/25/97 P2944 WA-03 0-2" 0-2" 48.8 149.3
11/25/97 P2945 WA-D3 4-6" 4-6" 135.2 339.3
11/25/97 P2949 WA-D3 6-8" 6-8" 45.3 96.2
11/25/97 P2946 WA-D3 8-10" 8-10" 31.8 61.8
11/25/97 P2947 WA-D3 10-12" 10-12" 13.7 16.6
11/25/97 P2948 WA-D3 20-22" 20-22" 4.9 2.7
11/25/97 P2950 ALBW-15 0-2" 0-2" 0.141 0.426
12/1/97 P2957 ALBW-110-2" 0-2" 57.6 150.3
12/1197 P2952 ALBIV-9 0-2" 0-2" 45.3 126.7
12/11/97 P2965 IVB-S2 0-2" 0-2" 0.046 0.013
12/12/97 P2975 WB-D3 0-2" 0-2" 45.5 118.1
12/12/97 P2980 WB-D6 0-2" 0-2" 29.1 73.4
12/11/97 P2985 ALBE-20 0-2" 0-2" 23.7 43.4
r ,, .. ,
> :,;{(;' Number of Samples "':: ,.
; .. ,, .. , ... ,,,. Corrected(b) Mammalian RGOs For Roanoke River {nl!fkg) Above RGOs /"( '" ',,:: River Otter LOAEL-based RGO 540 0 of 19 "'
/C iie:t ''J'.
River Otter NOAEL-based RGO 54 2 of 19 •~,i:~~-"~ 1J .. \• ,\y .,,,.:~~
';ti ,,,,,· -Number of Samples ~·:,•·: .• £• ' (i Correctcd(bl Avian RGOs ror Roanoke River (nl!fkg) A hove RGOs
;:1,,:t. .1 .. '., .. Barn Swallow LOAEL-based RGO 3,500 0 of 19
Barn Swallow NOAEL-based RGO 350 0 of 19 ,, L. ·t .•,: .,, . ., : . .· Heron LOAEL-based RGO 12,000 0 of 19 ,,' .:: Heron NOAEL-based RGO 1,200 Oaf 19
-·" ' . " Wood Duck LOAEL-based RGO 11,300 Oaf 19 '.• .. .,,. ' ., "' ''"Wood Duck NOAEL-based RGO 1,130 0 of 19
{a) Sample result represents an average of analytical results for three triplicate samples (P2664A, P2665A, and P2666A) taken at River
Marker I on November 14, 1996.
(b) Please refer to Table I for information on nature of corrections to wildlife RGOs initially presented in Lower Roanoke River Baseline
Ecological Risk Assessment (CDM. 2002).
i:\wprn/w\pjl\00•05112'23VS_Sed_l.lrJs\Table 2 Summary of TEOs·RGOs
ci X c,
-=-0 w I-
,: ·x
0
0
Figure 1
Preliminary Screening of 1996 Mammalian TEQ Data
600 ~------------'----------=--------------------~
500
400
300
200
100
··············································································································· ·••-. . . . . . .
Corrected LOAEL-
based RGO
540 ng/kg
Corrected NOAEL-
based RGO
54 ng/kg
34.8 49-1 48.6 . ···················································································································
Albemarle Sound off
Bull Bay
Albemarle Sound @
Highway 32
Off Mackey's Albemarle Sound @
Marker 1
19.1
Chowan River
•
•
Figure 2
Preliminary Screening of 1997 Mammalian TEQ Data -0-2"
600 ----------------------------------------~
500
400
c,
-"' c,
E.
Sl 300 >-c: -~
.2 □
200
100
················································································································ ... .
Corrected LOAEL-
based RGO
540 ng/kg
Corrected NOAEL-
based RGO
54 ng/kg
WA-S3 0-2" WA-D3 0-2"' ALBW-15 0-2" ALBW-11 0-2" ALBW-9 0-2" WB-S2 0-2" WB-D3 0-2" WB-D6 0-2" ALBE-20 0-2"
•
•
Figure 3
Preliminary Screening of 1996 Avian TEQ Data
350 ······················································································································~
300
250 m "' C> .s
fil 200 ,..
C ·x
0
i5
150
100
50 33.5
0 +----
Albemarle Sound off Bull
Bay
111.8
Albemarle Sound @
Highway 32
. .
195.8
Off Mackey's
180.0
Albemarle Sound @
Marker 1
54.9
Chowan River
Corrected NOAEL-
based RGO
350 ng/kg
•
•
Figure 4
Preliminary Screening of 1997 Avian TEQ Data -0-2"
350 •·•·••·····•····•••·•••···••··•···•···•••••••·•••···•••••·•••••••••·••··•·•••••···•·•···•••••·•···••••••••••••·•·• ••• •
300 Corrected NOAEL-
based RGO
350 ng/l<g
250 '5;
-" c, ..s
0 200 w f-
~ ·;.
0 149.3 150.3 c 150
118.1
73.4 •
0.013 I 43.4
WA-S3 0-2" WA-D3 0-2'" ALBW-15 0-2'" ALBW-11 0-2" ALBW-9 0-2" W!l-S2 0-2•• WB-D3 0-2" WB-O6 0-2" ALBE-20 0-2"'
Figure 5.
Preliminary Screening of Mammalian TEQ Data from WA-D3
WADS c, ,-1 ""
WA-D3 4-6" 1111:-135.2
WA-0,S~ j•I 45.3
WA-D3 8-10" a 31.8
WA-D3 20-22"
0 100
Corrected NOAEL-
based RGO
54 ng/kg
200 300 400
Dioxin TEQ (nglkg)
500 600
Correc ed LOAEL-
based RGO
540 ng/kg
•
•
Figure 6
Preliminary Screening of Avian TEQ Data from WA-D3
WA-D3 0-2" 149.3
WA-D34-6" -
339.3
WA-D36-8" -~ . . 96.2
61.8
2.7
0 40 80 120 160 200 240
Dioxin TEO (ng/kg)
280 320 360
Corrected NOAEL-
based RGO
350 ng/kg
•
•
400
___ ____,. ____ , ___ _ A RESEARCH REPORT Title Page
SOUTHERN ENVIRONMENTAL FIELD STATION
Weyerhaeuser
Research & Development New Bern, NC 28563
0 Technical Report
0 Technical Note
0 Trip Report
■ Other
Project No. 709,6940
Page 1 of 16
Albemarle Sound Sediment Characterization and Dioxin/Furan Study
Sample Collection and Data Listing Summary
Executive Summary
This document presents information on sample collection and summarizes data for sediment samples
collected in 1996 and 1997 from the Albemarle Sound, NC. The document was prepared to transmit
the information, which was requested by the USEPA Region IV. Sediment core or Ponar grab samples
were collected in November 1996, and November and December 1997, from a total of 35 locations
extending from the western to eastern portions of the sound. Data on physical characteristics (e.g.
organic content and/or particle size) were obtained from 48 samples collected at these locations. A
total of 21 samples from 13 of the locations were sampled and analyzed for dioxins/furans. Vertical
distribution of dioxins and furans with sediment depth was characterized in one location in 1997.
General observations from the compiled data:
Concentrations of 2,3,7,8-TCDD were non-detectable in surface core samples (0-2 inch) from
Albemarle Sound sites located in shallow water {<8 feet water depth). Among sites in deep water (>8
feet), 2,3,7,8-TCDD concentrations in surface core samples ranged from 7.34 parts-per-trillion (ppt or
ng/Kg) in the eastern sound to 32 ppt near the Highway 32 bridge. The 2,3,7,8-TCDD concentrations
in sample layers of a deep water core from the western sound initially increased from 25.1 ppt at 0-2
inches to 92.2 ppt at 4-6 inches core depth. Concentrations declined below the 4-6 inch layer, likely
becoming non-detect in an unanalyzed interval between 12 and 20 inches core depth. Non--detect
concentration was confirmed in the next deeper {20 to 22 inch) layer.
Organic matter and particle size data indicate a correspondence between water depth and sediment
character in the sound. Sediments from shallow water sites contained low organic matter (<3.2%) and
high sand fractions(> 72.7%) whereas deep water sites contained high organic matter (>5. 7%) and low
sand fractions (<47.9%). Across the sound (i.e., north to south orientation), the clay fractions and water
depth appear positively correlated. On a longitudinal basis (i.e., west to east orientation), organic rich
sediments {>8.0%) predominate in deep water areas and extend to the Alligator and Pasquotank
Rivers.
From the current data summary, the following general observations can be made:
1. Shallow water areas of the sound contain high sand fractions, low organic matter, and non-
detectable 2,3,7,8-TCDD concentrations.
DISTRIBUTION TO LOCATION AUTHOR'S SIGNATURE
TECHNICAL INFORMATION CENTER TIC
AUTHOR'S NAME (Typed)
Stephen E. Woock
PROJECT NO. APPROVED BY (Signature)
7096940
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2. Detectable concentrations of dioxins were found in sampled organic sediments in deep water.
3. Dioxin concentrations in the organic sediments in deep water lessened east of the Highway 32
bridge.
4. Dioxin concentrations in a deep water sediment core were greater at a subsurface sediment depth,
indicating that burial is likely occurring.
5. Organic rich (>8.0%) sediments predominate in the deep water portions of the sound, extending
from the western sound to the Pasquotank and Alligator Rivers.
Introduction
Sediments from Albemarle Sound were sampled in 1996 and 1997.
Ponar grab samples were collected in November 1996, at five sites to generally characterize 2,3,7,8-
TCDD/F and Total TCDD/F (i.e., the full seventeen congener analysis was not done), and Total
Organic Carbon (% TOC) concentrations (Figure 1 ). Four of these sites correspond to where NPDES
monitoring of fish tissues has been done since the early 1990s. The fifth site ("Off Mackey's") was
situated roughly midway between the Roanoke River mouth and the Highway 32 bridge. The grab
samples, which nominally sample the surface to about 6 inch depth depending on bottom hardness,
were in most cases collected as composites along transects at these locations. This compositing
method provides a physically averaged data point for the area. At one site, vicinity of Marker 1 off the
mouth of the Roanoke River, three independent samples were obtained to assess variability associated
with the sampling procedure. The appendix DATABASE and Sample Memos provides specific
identifying information for the individual grabs at the sites, and visual descriptions of the recovered
bottom materials.
In 1997, fourteen sediment core layer samples were analyzed from nine cores collected in the western,
middle, and eastern portions of the sound (Figure 2). These samples were analyzed for the seventeen
2,3,7,8-substituted and Total homologue dioxins/furans and% TOC. In addition, twenty-seven Ponar
grab samples were obtained from several of the core sites and additional sites along transects across
the sound (transects WA and WB, Figure 2). Analyses of these grab samples included organic matter
and particle size fractions.
A map of the spatial distribution of organic matter in the sound was prepared, based on visual
interpretation and by-hand drawing of isopleths, using data from this study and from the literature. The
combination of the dioxin/furan data and area coverage of organic matter in sediments can provide a
provisional means of estimating the spatial distribution of dioxins/furans in Albemarle Sound.
Methods
Sample handling and equipment decontamination
Waterproof field books were used to record all sampling information. All sampling and processing
equipment used to collect core and grab samples for dioxin analyses were decontaminated prior to use
and between sites. Acrylic core tubes, Ponar grab sampler, aluminum composite pans, knives, spoons
and aluminum foil were rinsed with methanol and hexane. Samples were placed in clean-certified
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glass jars. For organic matter and particle size samples, the Ponar grab sampler and composite pans
were rinsed with water between sites.
Study design and sampling
The first objective was to determine possible spatial differences in sound sediment dioxin and sediment
character (i.e., organic matter and particle size) in a latitudinal orientation (i.e., south to north}. Two
south to north oriented transects, termed WA and WB, and additional sites along the Highway 32
bridge (ALBW transect) were sampled (Figure 2). On each transect, a shallow water core sample of
surface (0-2") sand was obtained for dioxin/furan analyses. Also, one deep water core from the middle
of the WA transect and two deep water cores from the WB transect, one near the middle and the
second from the north end, were obtained for dioxin/furan analyses. Similar to the WB transect, one
shallow water core sample of surface (0-2"} sand and two deep water cores were obtained from along
the Highway 32 bridge for dioxin analyses. All cores from deep water sites were examined, described
visually, and sectioned with depth to obtain 5-6 individual sediment sample layers. However, only the
0-2" surface sediment sample layers of core samples were analyzed from all but the WA-D3 core. In
addition, several grab samples were obtained along the WA and WB transects from core locations and
additional shallow and deep water areas for organic matter and particle size analyses. Locations for
these are provided in the appendix DATABASE and Sample Memos.
The second objective was to determine possible spatial differences in sound sediment dioxin and
character in a longitudinal orientation (i.e., west to east). The spacing of the WA, WB, and ALBW
transects outlined above provides this information for the western and middle portions of the sound.
However, to evaluate the eastern portion of the sound, a core was obtained from the middle of the
sound off the Little River (ALB-20, Figure 2). Similar to the previous deep water cores, this core was
described and sectioned for five individual sediment sample layers, though only the surface 0-2" layer
was analyzed.
The third objective was to determine dioxin concentrations in sediment depth layers in the sound. To
make a preliminary assessment of this objective, all sample layers from the WA transect deep water
core W A-D3 were analyzed for dioxins/furans.
Organic matter and particle size data were plotted and a map of the distribution of organic matter was
prepared using data from this study and the literature (Riggs et. al., 1993; Wyrick, 1993).
Analytical
Percent solids and volatile solids (organic matter) were measured using methods from Standard
Methods for the Examination of Water & Wastewater, 18th Edition. TOG measurements were made
using the Puget Sound Estuary Protocol. Particle size was determined gravimetrically using method
ASTM D422.
Dioxin and furan samples were extracted using methods described in NCASI Technical Bulletin No.
551, "NCASI Procedures for the Preparation and Isomer Specific Analysis of Pulp and Paper Industry
Samples for 2,3,7,8-TCDD and 2,3,7,8-TCDF" (1989). The sample extracts were analyzed by EPA
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method 1613, "Tetra-through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS"
using high resolution GC/MS operating in the selected ion monitoring mode for enhanced sensitivity.
To improve detection levels for TCDD in low-level samples collected in 1997, six of the samples were
re-extracted and re-analyzed using larger initial sample volumes.
Results Summary
All data are provided in the appendix DATABASE and Sample Memos. Analytical lab data reports and
chain-of-custody records can be provided.
Dioxins in surface sediments of the sound
Concentrations of 2,3,7,8-TCDD were non-detectable in surface core samples from Albemarle Sound
sites located in shallow water (<8 feet). Among sites in deep water (>8 feet), surface sediment 2,3,7,8-
TCDD concentrations ranged from 7.34 parts-per-trillion (ppt) in the eastern sound to 32 ppt near the
Highway 32 bridge. Ponar grabs samples collected in 1996 had similar, though sometimes slightly
greater values that probably represent a mixture of surface and slightly deeper, and presumably older,
dioxin/furan distribution.
Dioxins in core sample layers
The 2,3,7,8-TCDD concentrations in sample layers of the WA-D3 core from the western sound initially
increased from 25.1 ppt at 0-2 inches to 92.2 ppt at 4-6 inches core depth (Figure 3). Concentrations
declined below the 4-6 inch layer, reaching 2.64 ppt in the 10-12 inch sediment layer. The 2,3,7,8-
TCDD concentration likely becomes non-detect in an unanalyzed interval between 12 and 20 inches
core depth. Non-detect concentration was confirmed in a 20-22 inch layer.
Sediment character
Organic matter and particle size data indicate a correspondence between water depth and sediment
character in the sound (Figures 4 and 5). Sediments from shallow water sites contained low organic
matter (<3.2%) and high sand fractions (>72.7%) whereas deep water sites contained high organic
matter (>5.7%) and low sand fractions (<47.9%). Across the sound (i.e., north to south orientation),
the clay fractions and water depth appear positively correlated.
On a longitudinal basis (i.e., west to east orientation), organic rich sediments (>8.0%) in the sound are
predominant in deep water areas and extend to the Alligator and Pasquotank Rivers (Figure 6).
Discussion
From the current data summary, the following general observations can be made:
1. Shallow water areas of the sound contain high sand fractions, low organic matter, and non-
detectable 2,3,7,8-TCDD concentrations.
2. Detectable concentrations of dioxins were found in sampled organic sediments in deep water.
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3. Dioxin concentrations in the organic sediments in deep water lessened east of the Highway 32
bridge.
4. Dioxin concentrations in a sediment core were greaier at a subsurface sediment depth, indicating it
is likely that burial is occurring.
5. Organic rich (>8.0%) sediments predominate in deep water portions of the sound, extending from
the western sound to the Pasquotank and Alligator Rivers.
References
Riggs, S. R., J.T. Bray, R.A. Wyrick, C.R. Klingman, D.V. Ames, J.C. Hamilton, K.L. Lueck and J.S.
Watson. 1993. Heavy metals in organic-rich muds of the Albemarle Sound estuarine system. Report
No. 93-02. Albemarle -Pamlico Estuarine Study. US Environmental Protection Agency, National
Estuary Program and NC Department of Environment, Health, and Natural Resources. 173 p.
Wyrick, R.A. 1993. Clay mineralogy and geochemistry of Holocene sediments of the Albemarle Sound
estuarine system, North Carolina. MS Thesis, East Carolina University. 123 p.
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Albemarle Sound
Dioxin sample sites: 1996
* = Ponar grabs
Figure 1. Sediment grab sampling sites in Albemarle Sound, 1996.
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Dioxin sample sites: 1997
9 = deep water co re
@ = sha I low water (sand) core
Figure 2. Sediment core sampling sites in Albemarle Sound, 1997.
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2,3,7,8-TCDD concentration (ppt) displayed in core sediment layers, TOG{%) adjacent
inches
o.o-
-
2.0-
-
4.0-
-
6,9-
-
a.o-
-
10.0-
-
12.0-
-
14.0-
-
1s.o-
-
18.0-
-
20.0-
-
22.0-
-
24.0 -
-
26.0 -
-
28.0 -
1997 WA-O3
·1JNbtl
JOf9)\
.,·'.•,.•,,t;
3.4
3.0
2.3
1.8
1.4
1.1
Figure 3. 2,3,7,8-TCDD and TOC in a sediment core profile at WA-D3, 1997.
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10
5
0
100
50
-
-
100
50
Organic
matter%
--
Silt%
100-+-----
Clay%
50
WA'-WA
10
water
depth (feet)
2
0 7,100 14,200 21,300
North distance (feet)
Figure 4. Organic matter and particle size of transect WA.
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South
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10
Organic matter%
5
Silt%
50
100-+----
Clay%
50
0 _j_---.J--
WB'-WB
10
water
l~d~e~p~th~(f:ee~t~)--============--========:--------~ 20-
0
North
7,700 15,400
distance (feet)
23,100
Figure 5. Organic matter and particle size of transect WB.
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South
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Chowan River
N % organic matter
• Project No. 709-6940
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Pasquotank River
scale i ■ >11 □ 3
~2 Gl 9 D <1
miles 8 7
Perquimans River +
==~□5
Hwy45
Roanoke River
...
::::::::. '.;
A llig a to~"\'--.._
River '-\ ~ J ~
Figure 6. Distribution of organic content in sediments of Albemarle Sound
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I
APPENDIX
DATABASE AND SAMPLE MEMOS
notes:
DATABASE 3 pages, TEQs on 3rd page
SAMPLE MEMOS 1 page
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; f'.2665A
290 130 I '
1:=:______ _ ___________ :__=.::--=--=·----·--==-:.::____ _:..::::::L~---__:~~ I -~-----:1-------
~L~i ""'' ,,...-1-~.,,.,~,,.,~~' ~,,.., 0 ~ -~~ 0 ~ -'T ~~ "'~-=1!=~~~:.:,,="<:'::'"'c_{'"~ ' """:::f ::"''"_j
[i>'2934'"" ""T "i ------~-I ·-··----. -·---~-----:---------------1
!~~35 '
:1·--i" ' 1
:P2944 ··l ·····No,1.66l~d~~ --··· ·····m· -N-6ii3Bl •-· -t'Tii:i". ·"ii'sg-.. ··· --14·500 .. ·· ··231 ,,a·-Nocs.oo> Nocs.9s)·-·"!'""-N□(s.98)·
ip2945 ND{9.11) . _N,0{9._1_1) -39-3 _____ 102 ,-840 648 17300 447 237 ND(7,24). : _N __ D{!,_24)_ Nl)(7.24) ....
;p2949··· ······No(4_29) NDc4:~---·239·· ··-6:oo ,a.9 36.o ··--· 1200·-···· · 496 15900 _·· ··· ·oo_:f··· ·-···ro'.'if i4·:g · ND(s.30i·· Nci(s.30> · ·
P2946 ND{7.66) ND(7.66} _ 173 I f;l~(OJ_S) 14.1_ "', ___ -_17.9 947 414 1~ _ 65.4 38.9 ND{S.57) ND(557) ND(5.S7).
P2947 .. 6.15 . 2.41 114 -·-r _}.92 7.36 . 16.0 ; -·-741f ---310 142CO 9.07 7.28 ND(1.41) ND(l.41) -Nci(1.41)
P2948. ··~ND,2.01)·~-;----Nb(2.01) · --66.( ND(2.13} ND{2.13) ·9.83-----·,-------546 248 ·146Qc) ·No(o.48)-·i ND(0.48) ! ND(1.29) ·ND(1.29) _ ND(t29)
P2936
i
i~~31 ______ >----------------~-----------------·--·---------·---·---·-·I_._._ .. __ -·-·-·----•-··-
P2938 ... ·I· ...... ! . i···-··-
;-~~~f--·=~~··· ' \--------
[ p294,..··· -· ···1 · ·· r · 1'
-l
i••--··I
. :---··-·--... j ......... !
;:~--.. ·-] ······/·
····I .. ,.. . ...... ]
iP2952 _:._ . ...1-__ -;,N"D'°("9,'63°')-_-,-_-__ "N"D"(9".6"3')'-t---,25"7~-,_-+.i--N~D"(~1"0.71),----C--;N"D~("10~.1~)--+----3~1~ .• ~--+--~1-;4"10~---54=5--+--;15300=cc-i'--· 154 95.9 ! ND(S.45) ND(S.45) f-No(S.4~-j
).P~7 ·-·---·-!-_ND(9JJ13} ... -f-.-.N[:i(?_.06) --·295 . ND(li .. 4) ····24.i"" l---~.5 ~-+-····_-~.,-"430~·-·_:··-_· __ ··-·-5af"" --··-;-5300·--··209···-·-. ·····;·;-i ... r .. N6(5.22)···--·: ·····No(S:22)···" r•····No(S.22)•-,• ··1
::= i No<o.23) . ND<o.23> ~Nocc(°'o."'56)~-+l-. -'N~o-(o~56J---No(o.56)_~ No(o.56)__ 12.9 s~---139 o.31 o.37 1 ND(o.31>·.; ND(o.31> · ND(0.31> ·
P2963 i
!P2965 --·No(o.sSf ·-· -"ND(O.ss)
iP2962
if?966 ....
iP2967
ND(0.89) ND(0.89) ---ND(0.89) -_,_ ND(0.89) ---·9.57 . 3.75 · ND(0.49)
iP2968 iP297if -1 ...... ND(s:OO)~(s."90)·_ --+--·-·_3_3~7_· ·--~·-N~-6df 3i ..
;p2969 .. 1..... --~---·--,•--·1-
. . I
·········553 ... · 1 .. 1.7000 .,fiii'"" ..... aia··· Nri{S:i/ii··· .. ;··· .N'ci(is."9ij"···!· ...... N6(6.iii)··· ··1
. ----~-;--~~ . -; -----+ + ! . . .... j.. . ... I 41.3
)::;~ ---.!•-·--·-··------. ----1--·--""·•-
:·:-~ .. ··-· ·· l--··-·!:{Q(3.:.~ ..... : .. _ ~_g.(8.:~.-... -r--"2-;16~~--_-._~_N" . .£?~(1~_4~~~~)_-_
]p2973 I , I
159 _, 199 ----,cioo---_ -,,o·--j_,i2oo-~ _877--·-si• 1 Niils:01j :"_□is_•~>f:N~C~~'.i.::/
---+---,~5~.7~. --!---34.9 -_.; __ 1760 --581-__ : -\-_,6200 __ .L 11:2'" -29.7_ ! ND(4,92} '~-ND(4,92) . i _ND(4s,i-J !:=-·1 _ND(3.04) -'. .. ND(3.04). l----297:_~-j_
Strictly Proprietary (Red): Disclosure strictly limited to persons on a managed !isl. Contact
Proprietary (Yellow): Disclosure limited to persons confidentially bound to Weyerhaeuser on a need to know basis.
Non-Proprietary (Green): Disclosure unlimited.
•
•
A RESEARCH REPORT
ES& T Southern Environmental Field Station
Research & Development
Strictly Proprietary (Red): Disclosure strictly limited to persons on a managed list. Contact
Project No. 709-6940
Page 15 of 16
Proprietary (Yellow): Disclosure limited to persons confidentially bound to Weyerhaeuser on a need to know basis.
Non-Proprietary (Green): Disclosure unlimited.
Dioxin/Furan TEQs
......... " .. ]
'
•
•
A RESEARCH REPORT
ES&T Southern Environmental Field Station
Research & Development
Project No. 709-6940
Page 16 of 16
Sa~e No. Memo
P2661A NNE frOITI MKl:i°3,4 Grab S~es Composited 10' 1)pooa1 ·112tu11x:21an/bm sittysand 360009N 76233'N/ 1S·2)porlar-1/2iuux21anibm sillysandwic1ams 360040N7623 lfN/'N 3)ponarluDgrey/bm clayw/some black sill on top 3601 04N 76 23
P2662A·"·---·8£Tu-~f ~~fk~ !\!:'at?0i~~!;-i&1~tct-~£~c\~t~~biii:Sii·~n-iOpj6.SB .. 49~ff6-~-~W-iB'-~-p~g 168 (same dmriph·ori" ;:;· above) 35 sa 34N 76 29 47W 18' 3) Piling 1iH;1·m;-d;SCripiIOrll~~-~t)-355823N76·29-41 w-iC14)Piliig
10511.n siltyfsand w{ciams 35 58 15N 75 29 3f!',N ~~~~~~~-~-~-~--~~== __________ _
P2663A · ·--Powerlin~s "150yds due west 1rom 71h pole ·1[00\ C~l ma(,\en 3'GiabST7' -a;.;y clay w/black Weaks & grey/1.bm sib on top sorTI<! clams 35 58 06N Rt 35 47V-l
P2664A --Fr~"M'arkir 1To·aeath~ ~-~@·each ;;abs~e-REr 11i 1)Grey··c1aY"wi>;;;;;.;.;$aSn001e;;;_-:jSCiffliSlirs100N76 39 14W 1Z 21arey clayw/some bm dis:-,:;;-.is -many Ci.iiTI$ 35 56 SON 76 39 14w 1Z 3)($,lm"e ;:reWiptiOfil.$"~-35-ss"iiN.76
,~=~--""'~0a1cwec __________ . ___________________________________________________ ··------··-·-·--·---··--_______ _
P2665A see P2664
P2666A seeP2664
P2667A ·1/4mile S o1 bfidgen.nnlog paraDel 8' l)Gcab 1f'2!ulx2bfownsa-ndw/some-sills andlev.'c1allls 3602 i-4Nia4110W20'~Glab1uil g[eyclayw/black siru~s some bm and tan $Ills Cntop 36 02 43N 76 41 31W21' 3)Grabtul (suTle descripiion u
_____ above).36 02 34N 75 41 46W 21' 4)Grab luD (Same d~_stripJion) 36 02 24N_ 76 42 03.w ---·---____ ··--··------·------·--·-------·-·--· ,-.. ----··-· ·----·------... ___ -·-·--· ·-
P29:31 S•Z clean· bm-~and w/marrt cl.ams 35 56 42N 76 36-lfffl
P2930 6'z deanbr= med. und lewclams 3556 50N763615W
~235
2929
~-~ · ··--~~m~~!!6~~,%!:;;e~~:s~:2c~~iJf~_;~~~\~\~~bli"0~/4~-iot.ii 1e~""iiio:·;--1;4I: i;;ov,n·s·~d .. 1··,;r:··s;·g;ey··sand;iblacli"spe~·k-s·s~-~s··;"i4·c1ean·gre;;:s;nd,-_· ____________ _
I~ :-cS------··"12'ZbrOWl'ISitty-sand-w/clamsis·s10N763612W ... .. -----------------
\~;:~ 1~i :::t:~~!tcf;I~~~~b~;!~"io;~i~tt:~!};7slr4;t~·1roow··
P2935 1Tz blac~•gey clay_ w/11.&darll br0','111 surlace silts 35 58 OON 76 35 47'W
1~2944 __ 1_6'z Section 0.0. 2JJ" 0.0. 4.0" Loose su1idall. bm sills g.ding1otinn b~!k gCll'p_•Q:o·. 05· sainp]ed1em0Ved ~lo co_re ex!rud~. 4.o. 8.0" ·aiaCk-bm-!ilm sedime·nl 8.0•. 28"_8m c!•Y)'llsmd__blii;_k speck5 3558 ~ 7535 47W
15~:~~-=--::::iE:;!:~:t~f;~··: _______________ -----·--· ---·----------··
IP2947 5ee P2944. Sedion 10~ 12" -------------·· ------·-----·--··-----~·-·----·
i p294a-· 5ee P294-4. Section -20 • 22" · ···----··--···-·----------· -----------·
IP2936 -· 18'z black•gey ctayw/ft. brown su1ace sill 35 58-3SN 76 35 A.OW
!:'~37 . 19'z black•!1~~YJl/lt. brown orange surl. Sjlts 35 59 _!ON 76 3535,W~---------------
[ ~.?33!'1 ......... 1 !}_I gr.ey_ clay _l'(/1:!,_ b!11 __ s_~ __ s_~s.}~ .. 5~--3:?.~ .. .?.~-~5 ?i:Y.'. . ..
P2939 19'z grey.blick dayw/tt. &darll brown surlace sills 360005N 76 351-z.-N
P2940 13'z ut}'blOWfl & gre}'medU'Tl sand some_smaQ clams 3600 11N 7635 11W
P2941 /z sill bm,grey sandw/S1'me black sills & clams 360022N 76350f?N-/
~~2 __ .............. S:z_br.~.is~ jen~.s.1:1:!d.w/bl_1~k. S;i!\_layef_~.~.~ ?_6 .. 35.0?.V'!. ......... _ ...... _ ......... _ .......... ... .... ... ... ... .... .. ... . . . . . . ........................ .
P2943 S'z brown s_and _w/black silt layer• many clams. macrophyles._llTiphipods 36 00 36N 76 35 row
~2952-.. ~' _-__ -·-1,9',z 5:~ction O.o ... ~_.O"_ ,Pr,o_C,es_s_ed_ifl lab, Ol"l .. f 211m cOr_e to_t_a1Iing1h ,?_4"_-o.f 0.5· ·g._t0i.S:urta~e .. sil __ ~,f _5_.l! ~1.ack_:!lf~. gorp __ ~'.o_. 1,~:0" Bm~~1~tWr1iG~0i~e:ak_s,._1f~.:.?4 er D_a~ ~ .. ~1~ clay
1rps::r·· .·· . "i_ti•-se_ction{i0.:·2.0-·p;O(eSsed·in1a·ti~Oll _1_21i/9iC~~-i01a1~"91h22" 0 O. 0."5;·u, bin. surl:·siil 0.5 '. _i.O" ai:ic_~~iey_ go_~·1.o · ~'ii Bm cla-y.W/b1aCk.Streaks· ... .. .. . .. ~-:~~-~-------~-~:~-·
I
P.2950 composrte ot 2 .. 2". cores. same description 0-7/S' It. br0','111 sand 7/S' •4" grey sand clean w/black specks
P2964 13' •· brn sils on top ol black-grey sandy dayw/m,rrt clams 35 59 12N 76 24 00\J./ /~= ·--·-···· :zuic;rs::l~~:~
3
~ ;.i94 \~Jc~~e:'.~%~ ol eiCh _ 0 ~ Ji4·i: redibrri sand ji4·: 1 :5 bla_cklsh s~ sand 1.5. l( tan 0,,,a:;,,::::::::::::::: ______ _
IP2962 10' n.bm s1fy sand-some dam sheUs 3559 58N 7624 00W .
P2966 .. ·· 18'1 ii. red/bm s_ilts on top _ol black "gorp" ~lm•rrt_l:l•ms 36 _00 18N 76 24 ooW _____ . ---·--···-·--··--
p2957 19'z It. red/bITl-siitS .. on·,01:lthinnefi"ay!fi!.bfa"Ck g~rp-ihan wa.01 also brown day on boHom 36 00 SSN 76 24 121,•r ···-----·· ---------i
~ -· _, .... ~.z .~.arr1_e .~-~-~rip~o-~ 1.1,~-~-.l>Ja_c_k_ 9(!rp_!~.~ ~·.R? 3§ __ 0.).}0N_ J.6 .. ?.~..1 -~·-· . _ _ .. -··-············ ........ _ ................. _ .. ··-----···· .. ····· _______ ·-·--.... _ ..... _ ................. ____ . _ ........................ __ ....... -............. _____ .... __ ............... ----·" ..... ·--.. ______ ..... -·-__ ··---_ ·---·-•-··
P2975 Seciion O. 2" processed in lab 12/12/97 Core Description: Tolal length 18" o. 0.5· Loose bm. floe. 0.5 • 4.5" Mos!l-j black sol\ gorp w/bm clay mix 4,5 • 8.75" Firm bm. clay w/hHle patches ol black sill 8.75 • Hr Dari! grey clayw/black streaks
P2969 l_B'z. U_,_br_own Silt_~ a!_oP .. mt,ieWdt,_ep black gorp. some brT'I dam bottom_& clams _36,02_ 12N 76 24 _19'-N_ ..... .......... _ _ ____________ _
~::~~· ........ ~~~:~:~:·~=:~~:~:~::·::~:~':d;~s 7~;~·t;x=36~ .. ~-7.:~.2~?3~ .. :.~--. : .... ··.~ ... :, ·~·-.. :~: ...................... ·-. ......................... ... ....... . ........... . __ . ········· . _ .... :···-•·····-.--·-··--·-----··-·-·""'
P2980 Section O. 2" processed in lab 12/12.197 Core Description: To1al length 21 3/4" O. 0.5 loose bm. Floe 0.5-4" Black gorp w/some bm day 4-20" Sm day w/some black streaks 20-21 3/4 Oar\! grey sandy clay
P2972 1 l'z ,en, _s_ilty _s_a_fld; __ on_t_op bl~_ck:thick _s_a,:id betc,w .. a_nd tan s!Jl!_s_an(l .. o_n_~otlom_ ~ m~re: o! cfiity __ sa.fl<:l .. l~ar:i s,.~_~_nk ~.haDO\'J_a1ea_s .no. tja_ms_ 36_()3 ~?-~. !~ 2.4 .. Jf!I.
ll;:;1········· ··:'.~_-~:~~::: ::n!t·J~e:~t;:~:::~~:t:-~n~ :t:r~!~~~~P;~·~~ ~~·;8 ~~ ~W . . . . ... . ....... .. ... . . ... . ...
~ ···-... · 19'i SectionO-Z' Pl'}?te5sedin.lab 12/12/97 Core Descripliyn: To1al~nglh 241/4" 0-0.5" Loose bm. Ao(·Q_-5·: :i"i/4;°e"'!Ck.!joip:i 1_/4". 1i:[_D_~gr~y/b1Tl day ·10·:241/4• Dark 9fey_saf1(jyciaywh0:,00'f~ebris s1ar1~-;-5_:__ ____ ----~
I Strictly Proprietary (Red): Disclosure strictly limited to persons on a managed list. Contact
Proprietary (Yellow): Disclosure limited to persons confidentially bound to Weyerhaeuser on a need to know basis.
Non-Proprietary (Green): Disclosure unlimited.
•
•
NORTH CAROLINA A -
DEPARTMENT OF EN9,}NMENT AND NATURAL RESOURCE~_
DIVISION OF WASTE MANAGEMENT &•~w ~,-• r'r~ o. ~-_.,, m ,,;,, ___ _
MICHAEL F. EASLEY, GOVERNOR
WILLIAM G. Ross, JR., SECRETARY
DEXTER R. MA TTIIEWS, DIRECTOR
Ms. Jennifer Wendel
01 July 2002
Superfund Branch, Waste Management Divisi_on
US EPA Region JV
61 Forsyth Street. SW
Atlanta, Georgia 30303
MCDENR
SUBJECT: North Carolina Applicable or Relevant and Appropriate Requirements (ARARs)
Former Chlorine Plant, Weyerhaeuser Plymouth Wood Treating Plant
Plymouth, Martin County
Dear Ms. Wendel:
The Stale of North Carolina has reviewed the request from EPA to list the stale Applicable or Relevant and Appropriate Requirements (ARARs) specific to the Weyerhaeuser Plymouth Wood Testing Site in Plymouth, North Carolina. The following North Carolina ARAR.s are to be met at this site.
State Location-Specific ARARs:
General Solid Waste Location Standard (15A NCAC Chapter 13B)
NC Coastal Area Management Act (NCGS Chapter 113A. Article 7)
State Action-Specific:
Hazardous Waste (15A NCAC Subchapler 13A.006, .0107, .0108, .0109, .0110, .OJ 12) Surface Water and Wetland Quality (15A NCAC Subchapter 2B.0100 and .0200)
Effluent Limitations (15A NCAC Subchapter 2B.0400)
Air Quality ( 15A NCAC Subchapter 2D .0400, .0500, . I I 00, .0540)
Dredging (15A NCAC Chapter4 and Chapter 2B)
Discharges to Surface Water (15A NCAC 2H.OIOO)
Solid Waste (15A NCAC Subchapter 13B.0100
NC Solid Waste Management Act (NCGS 130A, Article 9)
State Chemical-Specific ARARs:
Groundwater (15A Subchapter 2L .0101, .0102 .. 0103, .0105, .0106, .0109, .0110, .0111, .0112, .0113, .0114, .0201, .0202 (Mercury standard of I.I ug/L), and .0315.
If you have any questions or comments, please call me at 919 733-280 I, extension 350.
Sincerely,
Nile P. Testerman. PE
Federal Remediation Branch
Superfund Section
1646 MAIL SERVICE CEJ'ffER, RALEIGII, NORTII CAROLINA 27699-1646
401 0BERLl1". ROAD, SurfE 150, RALEJGH, NC 27605
PHONE: [phone] I FAX: [phone]
AS EQUAL OPPORTU:'l.1TY/AffiRMA11"EACTIOS EMPLOYER· 501k RECYCLED/I OW POST-CONSUMER PAPER
••
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
February 21, 2002
Rodney Proctor
CHI L28
Director, Environmental Affairs
Weyerhaeuser Company
PO Box 9777
Federal Way, WA 98063-9777
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960 ' :-----.__
' ----: r) 1£: ---------
1 f ._,
r·1·1· -----..... . . ,.....,..... ---. '-I ' ,r--,,, .._ __ __
----c.-' ,, J,\lf) , ... _. -_ ~ / --... __ ) ,;_, .) ':('i"/n; I
-----· . J 1,:\, ' ·---=-.:_:______/
RE: Approval of the Final Remedial Investigation Report and Final Baseline Ecological
Assessment Report, Landfill No. I Area, Weyerhaeuser, Martin County, North Carolina
Dear Mr. Proctor:
The United States Environmental Protection Agency (EPA) has completed it's review of the
above referenced documents. EPA approves the documents as the Final Remedial Investigation
Report and the Final Baseline Ecological Assessment Report for the Landfill No. I Area.
If you have any questions, please call me at (404)-562-8799.
cc: Jeff Stamps, Weyerhaeuser
Nile Testerman, NCDENR
Tom Augspurger, USFWS
Kathy Huibregtse, RMT
Lynne France, CDM
Internet Address (UAL)• http://www.epa.gov
Recycled/Recyclable• Printed wilh Vegetable oa Based Inks on Aecycied Paper (Minimum 30% Postconsumer)
J
,, Jute.d
£111•~ 11e11t,,l
Sol11tio11$
December 21. 200 l
Ms. Jennifer Wendel
Remedial Project Manager
USEPA Region IV
Waste Management Division
61 Forsyth Street. SW
Atlanta. GA 30303-3 l 04
Subject: Response to USE!' A Technical Review Comments
• 744 Heartland Trail 53717-1934
P.O. Box 8923 53708-8923
,\1adison, WI
Telephone: [phone]
Faxc 608-831-33]4
Revised Remedial Investigation and Revised Baseline Ecological Risk Assessment Rep011s
Welch Creek Area, Weyerhaeuser Company Site, Manin County, North Carolina
Dear Ms. Wendel:
Attached for your review are initial technical responses to review comments presented in your letter dated
November 13. 200 l. The responses to the review comments on the revised Remedial Investigation Report
(RMT. July 2001) are presented in Attachment I: The responses to the USEPA"s review comments on the
Baseline Ecological Risk Assessment Report (RMT, July 2001) are presented in Attachment 2. Review
comments have been categorized by general and specific comments as presented in your letter dated
November 13, 2001. For ease of review, the original comment is presented in bold typeface with the
accompanying response following in normal typeface. In addition to the comment responses, we have included
two appendices that present additional detail supporting technical concerns that have been identified. Appendix A
presents a review of conclusions of the United States Army Corps of Engineers (ACOE) hydrodynamic model for
Welch Creek. Appendix B presents a comparison of potential sediment mobility analyses.
Many of these initial responses acknowledge that the text will be clarified or modified as requested. In some
instances. additional information has been presented to address the technical comment. and form the basis for the
response to the comment. Several issues remain open for technical discussions to be scheduled early in 2002.
If you have questions regarding the enclosed information, please contact either of us.
Sincerely,
,G,,U..uf?/1;~// 4.--
topher D. Krause
I rojcct Manager
Attachments:
,/' h,/./utwH..-k. ~4/C-
n R. Huibregtse
Principal-in-Charge
Attachment I -Responses to USEPA Comments on the RI Report
Attachment 2 -Responses to USEPA Comments on the Draft Baseline Ecological Risk Assessment Report
Appendix A -Review of ACOE Model Conclusions
Appendix B -Comparison of Potential Sediment Mobility Analyses
cc: Rodney Proctor. Joe Jackowski, Jeff Stamps. Steve Woock -Weyerhaeuser Company
Steve Scott, ACOE
Del Baird. Lynn France -CDM Federal
Tom A_ugspurger, USFWS
. Nile Testerman,.NCDENR
Pmject File 5100.59
I:\ WP~1SN\P JT\00-l\5 l 00\44\Ul005 I 0044.Q l 6.DOC
• •
Attachment 1
Responses to USEP A Comments on the RI Report
I:\ WPMSN\PJl\00.QS 100\JJ\lJlOOS I 0()4.t.O 16. DOC
• •
Responses to USEPA Comments on the RI Report
Welch Creek Area Investigation
Weyerhaeuser Company Site, North Carolina
General Comment
1. The Executive Summary, and Summary and Conclusions reference to treatability studies
and in situ treatment options should be removed or augmented with a notation that ex situ
options will also be studied. The statement appears to pre-define the scope of feasibility
study; Welch Creek's low gradient, slow flows, rural land use, and Weyerhaeuser's use of
suction dredges to remove wastewater solids from their ponds indicate that removal of the
tons of wastewater solids in Welch Creek should also be examined if a Treatability Study is
proposed.
Comment noted. Ex situ remedial options will be evaluated as pan of the Feasibility Study (FS)
process, as appropriate. Please note that maintenance dredging activities do not confirm the
implementability and/or effectiveness of environmental dredging in the Welch Creek setting.
2. The COPC Migration and Significance section conclusions are contrary to those of the U.S.
Army Corps of Engineers Waterways Experiment Station (WES) which evaluated Welch
Creek sediment mobility as part of their lower Roanoke River assessments. In order to
facilitate resolution, please provide an analysis of the different input assumptions employed
and the basis for use in the computation of the hydrodynamics of each flow event. Absent
resolution of the differences in the two modeled conclusions, the EPA will employ an
independent peer review panel to determine the appropriate conclusion which will he
incorporated into the final RI document for Welch Creek. The specific comments provided
by technical reviewers are included in the Specific Comments Section in order to highlight
some of the more critical differences noted.
The WES findings on sediment mobilization in Welch Creek indicates that the thin active
layer of fine sediment and organics (1-10 mm) is most probably mobilized within varying
degrees for the storm surge and freshwater storm events. It is evident that elevated dioxin
loads are associated with low to moderate flows in Welch Creek. A dioxin fingerprinting
study concluded that Welch Creek is the most likely continuing source of dioxin to the lower
Roanoke River system. Additionally, high volume dioxin sampling by the USGS revealed
elevated dioxin TEQ values in surface water during low flows in Welch Creek. The flows
that occurred during the high volume dioxin sampling were low,(< 0.05 Pa bed shear
stresses), yet the ISO micron filter indicated a high concentration of dioxin in the water
column. The highest dioxin concentration was measured on the ISO micron filter, which is
most probably coarse organics from the Welch Creek bed that had mobilized at the
relatively low flow rates. It is apparent from the various studies performed that although
waste water solids have not been discharged into Welch Creek for decades, dioxin is still
readily available to Welch Creek flows. Because the highest concentration of dioxin-laden
J:\WPMSN\P! ,00-05 IOOI--Wll.0005 l0044•016.0CX:
• •
sediments is located in the bed of Welch Creek, it stands to reason that it is the major
source of dioxin into the water column.
The U.S. Army Corps of Engineers (ACOE) and Beak International Incorporated (Beak). on
behalf of Weyerhaeuser. have evaluated the potential for sediment mobilization within W_elch
Creek as part of two separate RI projects. Both are credible modeling efforts that were intended
to better describe how the Welch Creek system works and to evaluate the potential for physical
transport of sediment. Because of limited in stream data for calibration of either model. neither is
able, at this point. to predict the absolute thresholds for sediment mobilization nor the absolute
quantities of eroded sediment. On an informal basis, and at the request of the USEPA, efforts
were made by Weyerhaeuser and ACOE representatives to provide consistency between the
modeling approaches. as practical. As with any modeling effort, somewhat differing input
parameters were selected by the individual modelers based on their professional judgement and.
experience. As a result. certain model conclusions differ. However, there are also significant
areas of agreement between these two evaluations.
For the initial comparison requested by the USEPA above, the ACOE model conclusions (Scott,
2001) are revisited to illustrate areas of agreement and to discuss areas of differences.
Attachment I presents a detailed review and discussion of the ACOE conclusions. In summary,
there is agreement and some areas of disagreement between the Weyerhaeuser and the ACOE
study conclusions (Scott. 2001, Section 5, page 16). In particular, there is strong agreement by
Weyerhaeuser with the following ACOE conclusions and observations:
■ The reach of Welch Creek upstream ofMT-6 is predicted to be stable (see P. 9, I" paragraph
of ACOE report) and presents a low risk of sediment erosion and mobilization
■ The highest shear stresses would be generated in the reach of Welch Creek bound by
transects MT-7 and GT-15 (i.e., approximately 1600 linear feet). Differences between the
model interpretations center around the magnitude of the flow event that could potentially
mobilize the sediment. but the models generally agree regarding the area with the highest
potential for sediment mobility.
■ Any modeling effort has uncertainty. For larger flow events, the level of uncertainty
increases and would likely remain because of the low probability of collecting field
measurements during the high-flow events.
Furthermore, as requested above, " ... an analysis of the different input assumptions employed and
the basis for use in the ... [model] "is provided in Attachment 2. This attachment includes a
matrix table that compares the two models in detail and discusses the significance of the input
parameters on the conclusions. In summary. two major differences between the model
components affect the conclusions:,
■ Wetland flooding mechanisms· these affect the predicted shear stresses exerted by the
flowing water during various wind surge and precipitation events
The way in which the models simulate wetland flooding and subsequent drainage back to
Welch Creek influences how the models represent the whole-water sampling events and
affects the subsequent model predictions. The Weyerhaeuser model allows for a greater
amount of wetland fiooding at lower water elevations than the ACOE model. This results in
J:\WPMSN\J'JTIIXJ.Q5 l00\4.JIL0005 IO:J.l-4.QI 6 DOC 2
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greater wetland storage of water. In the Weyerhaeuser model, the drainage of this wetland
storage increases predicted shear stress for the modeled Hurricane Dennis event compared
with the Northeaster and the wind tide events. Observed data from the whole-water
sampling of those three events substantiates short-term sediment mobilization following
Hurricane Dennis but not the other two events. Because the ACOE model does not appear
to include wetland storage as a significant factor below an elevation of 2.5 feet NGVD, the
Hurricane Dennis and Northeaster events produce similar shear stresses when simulated by
the ACOE model. This leads to the ACOE's interpretation that all three wind surge events
are comparable to 2 to 5 year flood events.
■ Sediment shear strength values -these values are compared to the modeled shear stresses
exerted by the flowing water to evaluate if sediment is potentially mobilized within the creek
Differences in the estimated sediment shear strength values account for most of the
difference in the interpretation of the magnitude of the flow events that have the potential to
cause sediment mobilization. Based on its interpretation of the two PES shear strength tests,
the ACOE selected a very low, constant shear strength of0.017 Pascals (Pa) throughout the
creek length and with depth in the sediment. The ACOE's original sediment samples (i.e.,
those that were collected from Welch Creek and tested as is using the PES versus the later
testing of wet-sieved and reconsolidated samples) resulted in shear strength values that
appear to range from approximately 0.03 Pa to 0.24 Pa with limited erosion measured
(Figure A7, Scott 2001). In contrast, based on the TSS measured in 1999 during the wind
surge events, literature from other sediment sites, and the physical properties of the sediment
that vary throughout the creek, the Weyerhaeuser predicted shear stresses were compared to
higher shear strengths ranging from 0.2 to I.I Pa. The Weyerhaeuser model predicts less
potential for sediment mobility at lower flow rates (i.e., IO-year to 25-year events) overall
because of the higher and variable sediment shear strengths that were used as model inputs.
Attachment 2 presents a detailed discussion of the selected sediment shear strength values
by the ACOE and Weyerhaeuser.
It is a conclusion of the Weyerhaeuser model and the whole water sampling that the critical shear
stress is exceeded in at least a portion of Welch Creek during an event that causes shear stress ,
greater than the Northeaster, but less than Hurricane Dennis. We believe that these two events
bracket the critical shear stresses that will initiate sediment mobility in Welch Creek.
While there is a higher level of uncertainty with the value of critical shear strength of the
sediments, the credibility of Weyerhaeuser' s model predictions is demonstrated through a
comparison of the model predictions and the actual total suspended solids (TSS) measurements
that were made during the Welch Creek RI. Both models have used the TSS measurements to
calibrate against the wind surge events (i.e., measured TSS is compared to the model predictions).
This comparison is included in Attachment 2 (see the summary memorandum). In summary, the
Weyerhaeuser model threshold shear strengths were established so that mobility was not
predicted in the model for the events when TSS was not observed during sampling, and so that
the model would predict mobility during the Hurricane Dennis sampling event, which was the
only sampling event where TSS was measured above background levels. While the ACOE model
predicts sediment mobility for the Hurricane Dennis event, it also predicts a similar amount of
J:\WPMSN\PJTI00-05100\44\1..0005 10044-016 DOC 3
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sediment mobility for the Northeaster sampling event. In actuality, the TSS measurements during
the Northeaster event were similar to background TSS levels. These measurements were
obtained beginning nearthe steepest portion (or near peak flow) of the Northeaster stom1 surge
hydrograph and continued through the flow recession. as the water and sediment left the creek
(i.e .. the data are representative of the highest expected suspended solids in the water column).
Whole water samples were collected during the time period that the ACOE model predicts
significant TSS loading. As such. the Weyerhaeuser model provides a credible overall
representation of potential sediment transport in Welch Creek because of the model's ability to
adequately predict the conditions under which sediment may become mobilized based on the
limited field data.
Removing some of the inherent uncertainty in the physical transport models would likely require
several more years of additional data collection, monitoring, modeling and reporting. In the end,
uncertainty would likely remain for the larger precipitation events (i.e., 10-, 25-, 50-, JOO-year
recurrence intervals) because of the low probability of capturing these events in a short
monitoring time frame.
The relative risk posed by the dioxin mass transport to the Roanoke River has not been evaluated
as part of the Welch Creek RI. However, it is important to note and consider the following:
■ The surficial sediment dioxin concentrations within the area of concern (MT-7 to GT-15)
and throughout the lower creek system (i.e .. downstream of transect MT-6) are below risk-
based Remedial Goal Options (RGOs) calculated by both Weyerhaeuser and the United
States Environmental Protection Agency (USEPA).
■ Within and adjacent to the area of concern for potential physical mobilization, the dioxin
1-TEQs vary and are relatively low. At MT-7, the dioxin 1-TEQ was 6 ng/kg for sediment
(i.e., approximately I-foot depth). Just downstream of the area of concern at MT-8, the
dioxin 1-TEQ was measured as 90 ng/kg for the surficial sediment (i.e., 0.5-foot depth
interval) and ranges from 15 to 200 ng/kg for flocculent sediment (i.e., surficial sediment
within the top I inch).
■ The dioxin game fish advisory for the Roanoke River and Welch Creek was recently
removed by the State of North Carolina, indicating an improving aquatic system in and
downstream from Welch Creek
The 200 l high-volume dioxin sampling conducted by the USGS near the mouth of Welch Creek
(RRI05) confirms dioxin 1-TEQs previously measured by Weyerhaeuser using conventional
I-liter sampling techniques. The USGS result of 0.94 pg/L compares with the 1999 RI whole
water baseline monitoring result of 0.23 pg/Land the 1995 median surface water result of
1.1 pg/L (1-TEQs).
As requested in subsequent specific comments, this high-volume surface water data will be
incorporated into the Welch Creek RI. Weyerhaeuser is currently reviewing the quality assurance
of the high-volume sampling and analytical procedures, as well as observed field quality control
measures. Our initial review of the data has discovered some potential quality control issues
associated with the high volume sampling. These issues can be discussed in detail during our
February meeting.
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The USEPA notes that the 150 micron filter contained dioxin and interpret this to mean that
Welch Creek sediment has been mobilized. However. other transport mechanisms, influences
from the Roanoke River flow into Welch Creek. and changes in field conditions during the time
of sampling (i.e., approximately 8 hours) may be represented by this high-volume sample result.
A discussion of the high volume sampling results will be included in the final RI.
3. The approach used to calculate the RGO for Mercury in fish tissue based on mercury
concentrations in all fish locally collected does not result in a goal which is protective of
either the fish themselves or the higher tropic ecological receptors studied in the BERA. The
mercury goal of 0.74 mg/kg would not be protective of early life stages of fish and may
hinder fishes ability to spawn (Matta et al., 2001). Fjeld et al. (1998) found adverse effects
at 0.3 mg/kg tissue residue. Conaby Creek was chosen as a reference site for the Welch
Creek RI for its similarity in geochemical, hydrological, and ecological properties. EPA
considers the reference site to be an appropriate reference for investigation of contributions
of the Weyerhaeuser facility to Welch Creek, and the fish tissue sample data should be
included when calculating the average local background levels.
A computation of mercury RGOs for sediments and fish tissue which are protective of
ecological receptors selected for Welch Creek is important information to include in the
reports. EPA has calculated site specific average sediment to biota accumulation factors
(BAFs) and has applied these factors to the entire data set of observed sediment and fish
concentrations in Welch Creek. A more representative relationship is possible using all of
the data, rather than the maximum fish concentration detected at MT-4 and the maximum
sediment concentration detected at MT-6. The two attached excel spread sheets contain the
EPA calculated BAFs and example RGO calculations. Please revise Table 9-16 in the RI
and 8-12 in the BERA to include a Range of Ecological RGOs for Dioxin TEQ and Mercury
in both sediments and fish tissue. Mercury is a COC for the Welch Creek sedimenl~ and
should be evaluated in the feasibility study.
Mercury was designated as an ecological COC in the Baseline Ecological Risk Assessment
Report for Welch Creek (RMT, June 2001) (Welch Creek BERA) based predominantly, if not
solely, on the ingestion offish by the piscivorous endpoint species and emergent insects by the
insectivorous endpoint species. As a result, potential remediation goals were focused on the
protection of piscivorous species that would potentially be exposed to mercury in fish from
Welch Creek. As identified in the RI and BERA text. there is not a relationship between mercury
in sediment and mercury in fish tissue. as such a remedial goal for mercury in sediment would not
necessarily translate into reduction in fish tissue concentrations.
The Welch Creek BERA focused on the derivation of potential mercury remediation goals for the
aforementioned piscivorous measurement endpoint species on the recognized source of mercury
(Welch Creek fish). The RGO for mercury in fish proposed in the Welch Creek BERA was
derived using whole fish mercury data from the reference location (Conaby Creek) in addition to
other local reference locations [Roanoke River upstream of the Weyerhaeuser mill and Cashie
River (NC DENR, 2001), Albemarle and Pamlico Sound region (USFWS, 1992), Pettigrew State
Park upland lakes (NC DENR, 1999)] and was based on USEPA Region IV practice and
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precedence for deriving background criteria. As outlined in the BERA, there is precedent for this
alternative approach in Region IV. According to Michael Arnett (USEPA Region IV RPM), the
Cold Creek Swamp Superfund site Proposed Plan will include a RGO for fish that is the greater
of either 0.5 mg/kg or local background.
General Comment #3 cites values that supposedly reflect whole fish concentrations at which
potential adverse physiologic effects occur. Review of the Fjeld et al .. 1998 reference reveals
that the concentration of 0.3 mg/kg body weight cited as being potentially deleterious to fish is
based on a subjective evaluation offish behavior. It is also important to note that the authors
stated that the concentration of mercury at which effects were observed reflect "body
concentrations of Hg (>0.3 ug/g) may be found in eggs from piscivorous fish in lakes receiving
diffuse atmospheric deposition of mercury." This is a clear indication that the authors have
concluded that the whole fish concentration of mercury at which they observed effects in test
specimens is reflective of background mercury concentrations.
The parameters evaluated in the study conducted by Matte et al., 2001 consisted of
multigenerational hatch success, larval survival, juvenile growth, sex ratio, fecundity, and
fertilization success. The effects of mercury at several body burden concentrations were
equivocal on the parameters mentioned previously. In addition. the whole body fish
concentrations cited by Matta et al., 2001 that were observed to induce adverse physiological
function were greater ( I.I -1.2 mg/kg body weight) than the whole fish mercury RGO proposed
in the Welch Creek BERA (0.74 mg/kg).
The review comment indicates that site-specific average sediment to biota accumulation factors
(BAFs) are provided and used in the development of revised RGOs. The use of an average BAF
implies a strict linear relationship between sediment and biological tissue which is not evident in
the data set of observed mercury concentrations in sediment and fish from Welch Creek.
Clearly, exposure to background mercury in whole fish tissues contributes substantially to the
modeled ecological risk. Given the absence of a correlation between environmental media
(sediment and surface water) and biological tissues (fish tissue), as confirmed by the recent
Welch Creek database, no technical basis exists for addressing mercury in sediment that can with
confidence predict significant reductions in mercury concentrations in fish tissues or in estimated
risk. Protective goals should not be calculated for mercury in sediment and fish tissues without
adequate consideration for mercury background.
Specific Comments
1. Executive Summary Page iv, Paragraph 4. Institutional controls are not effective in
reducing exposure to ecological receptors. Suggest clarilication to the sentence to explain
what is meant by "limiting the uptake of dioxin by fish", specifically how this might be
achieved by institutional controls. Table 8-1 in the 1999 Preliminary Site Characterization
Summary does not contain a technology for "limiting the uptake of dioxin by fish."
J;\WPMSN\PJT\! '-051 f)(J\.J-IIUn051{)(~4-016.DOC 6
• •
Clarification will be provided. Covering affected sediments (with clean sediments or engineered
media) will limit the exposure pathway between fish and sediment. thereby reducing the potential
for uptake.
2. Section 3.2, Surface Water Sampling. Please include a description of where the samples
were collected in the stream (depth, cross section).
Surface water grab samples were collected from three locations in Welch Creek (MT-I, MT-6.
and MT-8) and two locations in Conaby Creek (CC-6 and CC-8). The samples were collected
from mid-channel and mid-depth at each sampling location. The text of this section will be
modified to include the requested information.
3. Section 3.5, Whole Water Sampling. The sampling method is not detailed enough to
determine if it is representative of the system (sampling rate, flow rate, volume of water
from each depth, etc.).
The whole-water samples were collected using an ISCO™ automated sampler. The model used
was the ISCO TM 2000 that has a sample collection rate of 5 Uminute. A 350 mL sample bottle
was collected at each programmed sample time. The sample collected is composed of equal
volumes from each of the four sample depths (i.e. 87.5 mL from each depth interval). The
contents of three of the sample bottles collected when the highest TSS concentrations were
observed during the surge event were composited for subsequent dioxin analysis. This additional
detail will be added to the text of the final RI.
4. Section 3.5, Whole Water Sampling, page 3-7, first paragraph. The flow of 200 cfs should be
substantiated.
An average flow of 200 cfs was estimated for the smallest of the whole-water sampling events
(i.e. the windtide event). It was estimated by calculating the volume of water in Welch Creek
between the peak stage and the low stage of the wind tide event and dividing by the duration of
the event. This calculation is discussed in more detail in Subsection 7.2.1 page 7-8. The text of
Subsection 3.5 of the final RI will be revised to include this information to support the 200 cfs
flow rate.
5. Section 4.1.2, Surface Water, second paragraph. Please describe the TSS collection method
and flow conditions, and a description of where in the stream they were collected. It is not
valid to compare turbidity and make correlations to TSS.
Samples that were collected as part of the RI for TSS analysis were collected in the same manner
and at the same time as the surface water grab samples. (see the response to Specific
Comment 2) Under circumstances where the correlation between turbidity and TSS has been
established. turbidity can be used to make an estimate of TSS. However, because these
relationships have not been established for Welch Creek and Conaby Creek, this correlation can
not currently be drawn. Therefore, the comment comparing turbidity to TSS will be removed in
the final text.
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6. Table 4-3 should probably have a footnote describing the sample location and analytical
results for sample ID's MT0SLB-SUR-S, MT06MP-40-SUR-S, and MT08MP-70-SUR-S.
The concentrations of 2,3,7,8-TCDD in these samples greatly exceed those of any other
surface water sample. If these values are real and accurate, they would be the appropriate
maximum concentrations for inclusion in Section 6 (maximum COPC concentrations by
media) and they would drive all the risk quotients for water. If they are not intended for
that use, they should be deleted from the table or have their applicability described in a
footnote
Samples MT05LB-SUR-S. MT06MP-40-SUR-S, and MT0SMP-70-SUR-S were collected as part
of an evaluation of pore water performed for the 1995 investigation. (Volume 3. Attachment 9 of
the Compilation of Existing Data Technical Memorandum, April. 1998.) As part of this analysis,
a sample of the surficial sediment was collected from Welch Creek. This sample was centrifuged
in the lab into a solid and liquid fraction. The samples designated with the suffix "S" represent
the results of the analysis of the solid fraction of the sample. The samples designated with the
suffix "L" represent the results of the analysis of the liquid fraction of the sample. Because
neither sample is representative of surface water quality, the results of this analysis (both solid
and liquid results) will be deleted from Table 4-3 in the final Welch Creek RI.
7. Section 6.1.1, Sediment, page 6-3, starting on the second paragraph. This is a repeated
comment on the discussion of atmospheric sources. This shows up at several locations in the
document. Please put in it one section.
The discussion of atmospheric deposition will be consolidated into one section of the RI and
referenced as appropriate in the conclusions and executive summary.
8. The results of background samples for PCDDs/PCDFs in sediments (discussed on page 6-5)
should be augmented with a discussion of the background concentrations of PCDDs/PCDFs
determined in the Roanoke River well-upstream of the Weyerhaeuser Plymouth mill. The
background sediment samples for the Roanoke River study had TEQs one to two orders of
magnitude less than those reported for Conaby Creek. A sediment screening value was
derived for the Roanoke River study as 2-times background, which results in 15.75 ng/kg
TEQs, as compared to the 126 to 196 ng/kg TEQs determined in Conaby Creek. More
discussion of regional background values would be helpful; there are certainly values far
less than those of Conaby Creek nearby which could be used for comparison to Welch
Creek sediment values.
We agree that using a combined or averaged background concentration would be more
representative. We propose to use an average of Conaby Creek and Roanoke River background
samples to develop background concentrations of dioxin and mercury in sediment, as well as
dioxin and mercury in fish tissue.
9. Page 6-5 notes that TEQs could only be calculated for those samples where all of the 2,3,7,8-
substituted PCDDs/PCDFs were analyzed. In fact, TEQs can be calculated for those
samples where only 2,3,7,8-TCDD and TCDF were measured as long as it is acknowledged
that these represent the minimum TEQs (i.e., the total TEQs for all isomers are greater
J :\ WPM SN\PJT\00-05100\-W.UXlOS t 00-U-O I 6.l)()C 8
• •
than or equal to the ,·alues derived from these two isomers). This is important for two
reasons. First, 2,3,7,8-TCDD and TCDF represent most of the TEQs in many samples.
Second, and important for the final RI, the highest TEQs for Welch Creek would be
;::5,670 ng/kg with this approach, rather than the 4,536 reported on page 6-6 and in several
tables. While the TEQs may be higher if all isomers were considered, this does not diminish
the fact that the TEQs for at least two samples exceed what is currently being reported as
the maximum (despite only having two isomers for TEQ calculations).
TEQs will be calculated for samples that were only analyzed for 2.3,7,8-TCDD and 2,3.7.8-
TCDF and presented in tables of the final RI. The Risk Assessment used the highest sediment
TEQ (based on 2,3.7,8-TCDD and 2.3.7,8-TCDF) in the analysis of risk and conservatively
rounded upward to 5700 ng/kg.
10. Please provide the flow conditions for the period when surface water samples were collected
from other Welch Creek locations (those reported in Table 6-3 and on page 6-9).
PCDDs/PCDFs in those samples range from 1 x 104 to 1 x 10·2 ng/1 TEQ (using TEFs from
USEPA 1989); this range of values may be considered for modeling baseflow loadings
(instead of the 2 x 104 ng/1 value) once flows are known.
We have no data regarding flow in Welch Creek. The sample collected from the baseflow whole-
water sampling event was determined to be most representative of the water quality leaving
Welch Creek during baseflow conditions for the following reasons:
■ The whole-water sample was depth-integrated.
■ The whole-water sample was collected near the mouth of Welch Creek.
■ The whole-water sample was collected during a period of known river stage conditions.
■ The whole-water sample was collected during a mild stage recession.
Surface water grab samples that were collected at mid-depth above the flocculent wastewater
solids, at locations over a mile upstream were not considered to be representative of the transport
at the mouth of Welch Creek.
11. The Welch Creek data from the USGS high volume dioxin sampling conducted as part of
the Roanoke River investigation should be integrated into Section 7. Selection of wnste
loading input values should be supported by discussing all of the available estimates for the
input parameters, this is particularly important for the PCDDs/PCDFs in surface water
because of the lower detection limits employed by the USGS. Their data can be used in
loading calculations provided that the sampling was performed at a flow event that can be
used in the modeling. For example, the Roanoke River background sampling for the USGS
high volume PCDDs/PCDFs sampling effort was about 0.00005 ng/1, or one-half the value
used in the Roanoke River loading calculations in Section 7. Also, the Welch Creek
PCDDs/PCDFs concentration was about 0.00095 ng/1, or about 4-times that used in the
baseflow loading calculations of section 7. The range of values and the flows at the time of
sample collection should be provided as context for the values ultimately used in loading
calculations.
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The use of TEQs based on the USEPA 1989 TEFs to calculate loadings can mask the release
of the most toxic isomers from Welch Creek sediments. Note that the surface water dioxin
data (Table 6-6) indicate that 2,3,7,8-TCDD and TCDF are detected in Welch Creek surface
water and they are below detection in the background Roanoke River water (Table 4-3).
Hence, the load of the most toxic isomers (as opposed to the lower toxicity hepta-and octa-
PCDDs/PCDFs) is a concern that should be discussed in the documenL This concern is
made more clear by examining the USGS high-volume sampling PCDD/PCDF data for all
of the isomers. It could also be addressed by using the World Health Organization TEFs
which do a better job of capturing the avian, mammalian and fish toxicity of PCDDs/PCDFs
than the older USEPA 1989 TEFs
The use of TEQs does not mask the release of the most toxic isomers, but sums the toxicity of all
the congeners as equivalents of the most toxic form. as directed by EPA early in the RI design
process. The USGS high-volume sampling results will be used to assess the sensitivity of the
mass loading calculations in the RI. The mass loading analysis presented in the RI concluded that
the annual loading from Welch Creek represents 0.83 to 1.34 percent of the total Roanoke River
TEQ loading. If the high-volume sampling results are used in the analysis, the TEQ mass loading
to the Roanoke River is reduced by approximately one-half and contribution of dioxin TEQ from
Welch Creek increases during baseflow conditions by approximately four times. The effect of
applying these results to the TEQ mass loading calculation would result in the annual loading
from Welch Creek representing up to 6.6 percent of the total Roanoke River loading.
However, this calculation likely significantly underestimates the Roanoke River mass loading and
significantly overestimates the Welch Creek baseflow contribution. This annual loading
calculation for the Roanoke River does not account for increased transport of dioxin TEQ during
precipitation events. Runoff of dioxin from burned land and from other upland sources of dioxin
is likely to be a significant source of dioxin to the Roanoke River that would not be accounted for
in this calculation using the Roanoke River baseflow high-volume sample.
Dioxin TEQs ·calculated using the WHO TEFs are presented for comparison in text and data
tables throughout the RI. The mass loading of dioxin TEQ will also be calculated using the WHO
TEFs and will be included in the final Welch Creek RI for comparison.
12. Section 7.2, Please provide information on the proportions of clay and organic material in
the waste water. Is the waste water clay distinctive of the process or similar to native
clays?
We have no information on the proportion of clay and organic material in the historic wastewater.
We also have not performed any analysis to distinguish between native clays and the clays there
were used in the paper-making process.
13. Section 7.2, The statement that presence of wastewater solids in Welch Creek provides
evidence that local hydrological condition do not readily move this material should be
augmented with some additional discussion. For this statement to be meaningful, it would
seem to be necessary to know the volume of wastewater solids present when discharge
ceased in 1988. Unless the volume or depth of wastewater solids is about the same, then
LIWPMSNIPJTI00-05 l00\J.ll[Jl00510044-0l6 DOC lO
• •
material may well be moving in the system. Presence tells us that much waste remains in
this environment, not how much might have left the system over the last decade. Post-
hurricane profiles of the unconsolidated wastewater solids could be prepared to determine
whether they stayed in place. Without some estimate of the original amount of wastewater
solids in Welch Creek at the time the discharge was removed or a comparison of sediment
stability through time, statements about sediment stability based on existence of waste are
potentially misleading.
It is understood that the presence of wastewater solids alone does not prove that the wastewater
solids can not be mobilized. Please note that even if Welch Creek bathymetric data were
available from 1988. the TSS monitoring and whole water sampling provide a better estimate of
the stability of the existing creek sediment. As requested. additional discussion will be added that
will include the results ofTSS monitoring during baseflow as well as during surge and
precipitation flow events.
14. Section 7.2, Migration and Significance, fifth paragraph, third sentence -This sentence
should read: "These barriers divert the flow of water from the wetlands to Welch Creek
just above the confluence with the Roanoke River."
The text of the report will be modified as requested.
15. Section 7.2.1, Welch Creek, page 7-8, first paragraph. Why was the average flow used
instead of the peak flow?
In order to estimate the mass of dioxin TEQ leaving Welch Creek during a particular event. the
estimated average flow rate was multiplied by the duration of the event and by the average
concentration during the event. If the peak flow were multiplied by the duration of the event, the
volume of water leaving Welch Creek would have been grossly overestimated. and therefore the
mass of dioxin TEQ would have been overestimated as well.
16. Section 7.2.1, Welch Creek, page 7-10, second paragraph. The mass of dioxin TEQ can not
be verified as to the representativeness based on the limited sampling methodology. It is not
clear if the calculation are conservative.
Refer to the responses to Specific Comments 2, 3 and 5 for more discussion of whole-water and
surface water grab sampling methodology.
The mass loading of dioxin TEQ is a "best estimate" that was made using the whole-water
sampling results and estimated storm event recurrence intervals. The mass loading of dioxin in
the Roanoke River is likely underestimated since the calculation applies a baseflow dioxin TEQ
concentration to the entire year's annual average flow. The whole water sampling method may
also over-estimate the concentration in water leaving Welch Creek, since the method equally
weights depth intervals, elevating the importance of the bottom intervals. which would have
lower flow velocities. For these reasons. we believe that the calculations and subsequent analysis
are sufficiently conservative.
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17. Section 7.23, Potential Sediment Mobilization Under Precipitation Events, page 7-15, first
paragraph. What value was used for the estimate of erodability? The wood chips, hark, etc.
can increase the erodability.
The analysis that was presented in the RI did not make any assumptions regarding the erodibility
of the sediments. The analysis in the RI evaluated the potential for sediment mobility by
comparing the model-predicted shear stresses to the estimated threshold shear strength of the
sediment. Where the predicted shear stress exceeded the estimated shear strength, we concluded
that there was potential for sediment mobilization. Consistent with the approved work plan, no
attempt was made to quantify the amount of erosion by using an estimate of sediment erodibility.
18. Section 7.2.3 Potential Sediment Mobilization Under Precipitation Events. The Army of
Corps of Engineer study conducted as part of the Roanoke River investigation provided
evidence supporting a much lower shear stress number. The laboratory results indicated
that the minimum critical shear stress for Welch Creek sediments is generally less than
0.1 Pa, with trace erosion occurring at< 0.05 Pa. The Welch Creek sediments have an
average density between 1.08 and I.I g/cu cm. This indicates that the sediments consist of
95 percent water by volume. The top layer of sediments is a mix of flocculated fine
sediments (silts and clays) and organic material. This thin layer is highly erosive and
mobilizes at low to moderate flows in Welch Creek. The Corp of Engineer's analysis
concluded that the thin active bed layer (1-10 mm) in Welch Creek is mobilized for the
freshwater storm events (2 and 5 year events), with bed scour (1-4 inches) possible for the
10-100 year storm surge events.
In addition, for the freshwater storm event analysis (2-100 year events), the downstream
water surface elevation boundary (Roanoke River) was set at 1.5 ft, which is 0.6 feet higher
than the average Roanoke River stage at Plymouth. The Corp of Engineers assumed an
elevation of 0.9 ft for the Roanoke River for the 2-10 year events because it is possible to
have that magnitude of a storm in the Welch Creek watershed without affecting the stage of
· the Roanoke. For the 25-100 year events, it would probably be a regional storm, thus the
Roanoke River would be higher and a 1.5 ft water surface elevation would be a legitimate
assumption. By assuming a higher downstream water surface elevation, the energy grade
line is less, therefore the computed bed shear stresses are less.
Flooding on the Roanoke River that would likely accompany a storm event, will generally result
in flooding on Welch Creek, therefore, the downstream boundary condition was set 0.6 feet above
average stage in the Roanoke River. While this is a reasonable assumption, a comparison
between the ACOE and Weyerhaeuser models for the 2-10 year flood events shows that there is
linle difference in the predicted shear stress for these flood events. A discussion of model
sensitivity to the downstream boundary condition will be added to the RI text.
19. Figure 8-1 is titled Conceptual Human Health Model for Welch Creek and Adjacent
Wetlands, yet aquatic, terrestrial, and avian biota are depicted as receptors. Please correct.
The title of Figure 8-1 will be revised to read Conceptual Model for Welch Creek and Adjacent
Wetlands.
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20. The source of the permeability coefficient for dermal exposure should be identified in the
tables.
The appropriate risk calculation tables for dermal exposure to surface water will be revised to
include the source of the dermal permeabililty coefficients for the COPCs.
21. Table 8-1. There are discrepancies between the values shown here for wetland soil and
those reported in Standard Tables 2.4 and 3.4 in Appendix K. Please reconcile. Also, as
shown in Table 2.4, chromium exceeds its screening value and should be a COPC.
The discrepancies between the values shown for wetland soil in Table 8-1 and in Standard
Tables 2.4 and Table 3.4 in Appendix K will be reconciled.
Chromium was considered a COPC for wetland soil in the risk assessment. Table 2.4 will be
revised to show that chromium exceeds the screening value and is considered a COPC.
22. Table 8-2. The Region IV guidance cited here does not mention exposure duration for
recreational fishermen. EPA's 1991 Human Health Evaluation Manual, Supplemental
Guidance: "Standard Default Exposure Factors" lists an exposure duration of 30 years for
recreational fishermen. Please make appropriate changes.
The exposure duration relied upon for the Reasonable Maximum Exposure (RME) evaluation of
the recreational adult fisherman was selected to reflect the adult fraction of a 30 year residential
exposure duration (or approximately 25 years). At the request of USEPA and to represent a more
conservative evaluation. the human health risk assessment will be revised using the exposure
duration of 30 years for the recreational fisherman.
23. Standard Tables 3.4 and 7.5RME, 7.8RME, 7.5CT, 7.8CT, 8.5RME, 8.SRME, 8.5CT, and
8.8CT. There are discrepancies between the COPCs and the concentrations of COPCs for
wetland soil shown in Table 3.4 and the 7-series and 8-series tables. Please reconcile the
differences and reflect changes in text, in appropriate 9-series and 10-series tables, and in
Appendices I and J.
The discrepancies between the COPCs and the concentrations of CO PCs for wetland soil will be
reconciled in the tables and the text.
24. Standard Tables 3.5 and 7.6RME, 7.9RME, 7.6CT, 7.9CT, 8.6RME, 8.9RME, 8.6CT,
8.9CT. There are discrepancies between the CO PCs and the concentrations of CO PCs for
wetland water shown in Table 3.5 and the 7-series and 8-series tables. Please reconcile the
differences and reflect changes in text, in appropriate 9-series and 10-series tables, and in
Appendices I and J.
The discrepancies between the COPCs and the concentrations of CO PCs for wetland water will
be reconciled in the tables and the text.
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25. Section 9.5.2, Page 9-8. Text states that "Statistical evaluation of the variances of the whole
fish mercury data concluded that, within some of the designated forage groups, there was a
significant (P<0.05) difference between Welch Creek and Conaby Creek observations."
This sentence should be revised to read "Statistical evaluation ... concluded that there was a
significant (P=0.0001) difference between the average mercury concentration in fish in
Welch Creek and the average concentration in Conaby Creek (BERA Appendix D)." The
sentence to be changed is misleading because it suggests that the differences between the
two creeks only effected certain forage groups, when the average was also effected. The
predator and large forage fish, which tended to show the higher mercury in Welch Creek,
are the dietary components of the river otter and great blue heron, according to BERA
Appendix D.
Fish were collected from Welch Creek and Conaby Creek for the purpose of inclusion of
appropriate COPC body burdens in the dietary exposure model estimation of daily intake of the
piscivorous measurement endpoint species. As specified in the Ecological Risk Assessment Study
Design and Sampling and Analysis Plan (RMT, 1999), fish were segregated into feeding groups
specific for the piscivorous measurement endpoint species.
Fish data were evaluated to determine if real differences existed in body burden of ecological
COPCs from fish collected from Conaby Creek and Welch Creek. The initial statistical
evaluation indicated that there was a statistically significant (P<0.05) interaction between
individual forage groups and location. In light of the statistically significant interaction,
statements concerning any potential real statistical differences between mercury tissue
concentration of all fish from Conaby Creek and Welch Creek can not be made. Subsequent
statistical evaluations were conducted to determine where the differences in body burdens of
forage groups existed between Conaby Creek and Welch Creek fish. The results of these
analyses were discussed in detail in Appendix D.
26. Section 9.5.2, Mercury, Page 9-10. Text on line 4 indicates that at a higher mercury
concentration the rate of methylation will decrease. This is a misinterpretation of the
literature source (Krabbenhoft et al., 1999). It is the rate of increase in the methelyation
rate that decreases as mercury concentrations increase. Clearly, the shape of the function,
with the plateau in rate of methyl mercury production, is illustrated in Figure E-3 of the
BERA. The bend in the curve, however, occurs at mercury concentrations higher than the
levels which occur in Welch Creek, based on EPA's experience at other sites and the data
for Welch Creek wetlands. Tbis finding is very encouraging because it shows that actions to
reduce the concentration in sediment will result in a corresponding decrease in
concentrations of methyl mercury in sediments, and consequently in biota. Suggested is to
take out the entire paragraph, because we have our own data for Welch Creek on methyl
mercury in sediments and do not have to infer concentrations of methyl mercury a
literature extrapolation.
Weyerhaeuser does not have methyl mercury data for Welch Creek or Conaby Creek, as stated in
the report. If the USEPA has data on methyl mercury in sediments from Welch Creek,
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• •
Weyerhaeuser would appreciate the opponunity to review this data in light of the published
trends in the literature and the importance of this issue to the overall project.
As to the review comment about "rate" of methylation, we believe the confusion is semantic.
"Rate" of methylation refers to the ratio of methyl mercury to total mercury. Since methyl
mercury is derived from total mercury. the "rate" at which methyl mercury is produced decreases
at high concentrations of total mercury. This has been documented in the literature. Comparing
the total mercury concentrations (normalized to LOI) with the methylation graph (Figure E-3). it
is likely that Welch Creek sediments are in a concentration range where methylation is not a
strong function of total mercury content. In other words, reducing total mercury in sediment by
even 50 percent will have little impact on the methyl mercury concentrations.
27. Section 9.6.2, Preliminary Ecological Remedial Goals, Page 9-13, last line. Suggested
language change: "It is also assumed that the relationship between concentrations and
exposure is linear." For systemic toxicants, the acceptable exposure level is set equal to the
threshold for toxicity, with application of an appropriate margin of safety. See RAGS
Part B.
The text will be modified as requested.
l:IWPMSN\PJl\()().05 l00\44\1..0005 (()(}4...Ql6 DOC 15
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Attachment 2
Responses to USEPA Comments on the
Draft Baseline Ecological Risk Assessment
1:\WPMSN\PJT\(Xh 5100\4411.000510044-016 DOC
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Responses to USEPA Comments on the Draft Baseline Ecological Risk Assessment
Welch Creek Area Investigation
Weyerhaeuser Company Site, North Carolina
General Comments
1. Much progress has been made in developing toxicity profiles for the COPCs. Pertinent
literature has been identified and included in the derivation and discussion of toxicity
reference values (TRVs). The appropriate literature has now been identified and discussed
(very good progress), however, EPA disagrees with some of the selected TRVs based on our
interpretation of that literature. For example, the PCDD/PCDF discussion (pages F-2 to
F-21) for mammals correctly identifies Heaton et al. (1995) and Tillitt et al. (1996) as
applicable references and proceeds to summarize these studies. However, the Heaton et al.
(1995) lowest observable adverse effect level (LOAEL) of 3.6 ng TEQs/kg body weight/day
for adult female mink is lower than the LOAEL (page F-8 and in the BERA calculations) of
10 ng/kg body weight/day based on Murray et al. 1979. EPA believes the Heaton et al.
(1995) reference to be the most applicable to deriving the TRV; this is not an esoteric
concern because it is three times lower than the TRV used now. If the Heaton et al. (1995)
reference is used, then the risk calculations for all mammals would increase by about a
factor of 3. We have a similar concern with the avian PCDD/PCDF TRV
Toxicity profiles were relied upon as outlined in the approved Welch Creek Ecological Risk
Assessment Study Design Addendum (February 2000). and as further discussed and agreed upon
in the September 19. 2000 meeting between USEPA, Weyerhaeuser, and RMT. The uncertainty
analysis was expanded as requested by USEPA in the Revised Welch Creek Baseline Ecological
Risk Assessment (RMT June 2001) to include a discussion of referenced studies in the July 2000.
USEPA comments (Attachment 2, General Comment I) on the Welch Creek Baseline Ecological
Risk Assessment (RMT April 2000).
The Heaton et al. (1995) study identified in the agency review was not used in the development
of a mammalian TRV for the following reasons.
■ The primary contaminant of concern for the study is polychlorinated biphenyl (PCB)
■ The 2,3.7 ,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalent concentrations (TEQs)
presented in the study are semiquantitative in that they were derived using a screening level
fluorometric bioassay. The TEQs do not represent the results of a standard analytical
procedure for 2,3,7,8-substituted polychlorinated dibenzodioxins/polychlorinated
dibenzofurans.
■ The article further indicates that "PCBs contribute a major portion of the TEQs ... other
compounds can contribute to the total TEQs." Lack of specific analytical quantification of
the contributors the TEQs relied upon in the study conclusions minimizes the suitability of
this reference for the Welch Creek BERA.
Overall. the cited literature, although appropriate for inclusion in a discussion of TRY
uncertainty. does not support modification of the mammalian TRY for dioxin.
l:\WPMSN\PJT\OJ.051001,..1.i\l..0005100-lJ,0!6.DOC
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2. The benthic community analysis by the Rapid Bioassessment Protocol (RBP) was developed
to assess the impacts of traditional water quality problems. such as nutrient enrichment and
low dissolved oxygen. The metrics calculated by the RBP primarily address traditional
water quality impairment. Metrics specifically for t?xics are lacking. Therefore, effects of
toxics may be confounded by effects of low dissolved oxygen conditions present in both
creeks. I agree with Davis Lenat's recommendation to include comparison of dissolved
oxygen readings over time between the two creeks in the interpretation of the data. The
conditions in Conaby Creek could be due to frequent low dissolved oxygen events, relative
to Welch Creek. Because of the limitations associated with dissolved oxygen, EPA disagrees
with the risk assessment's conclusion that there is no unacceptable risk to the benthic
community. The test apparently may have had low power to detect a difference between the
two creeks due to confounding effects. EPA advocates a triad approach, combining
measurements of effects in the field, chemical analysis, and toxicity testing. No one point on
the triad "trumps" another in this approach. This approach, also described as
"weight-of-evidence", considers the statistical power of the test or study to detect a
difference in the study population and the strength of the association between the
measurement and the causative agent.
The benthic community assessment endpoint was defined as an evaluation of the ecological
health of the fresh water macroinvertebrate community. specifically in terms of structure and
function in support of upper trophic levels. David Lenat concluded that the general study design
was adequate to compare the benthic communities of Welch Creek and Conaby Creek. The
benthic macroinvertebrate survey method used was more robust than most Rapid Bioassessment
Protocol collection methods.
The suggested dissolved oxygen readings over time with collocated sediment and littoral
invertebrate sampling are not available. Dissolved oxygen measurements collected during RI
sampling and benthic sampling of Welch Creek and Conaby Creek. do not indicate appreciable
differences in dissolved _oxygen conditions between the two creeks at the time of and at the
locations sampled.
Both Welch Creek and Conaby Creek populations appear adapted for low dissolved oxygen
conditions identified as present during the warm season by limited water quality data. There
appears to be no major differences between the benthic invertebrate communities in the two
creeks: thus, c·hemical toxicity does not appear to have altered the Welch Creek benthic
community relative to the low dissolved oxygen-driven swamp stream local conditions. Data are
not available, however, to draw detailed conclusions regarding a relationship between dissolved
oxygen and risk to the benthic community.
Agency review comment #8 on the Data Evaluation and Exposure Modeling Technical
Memorandum for the Welch Creek Area (reference), requested a "weight of evidence" approach
relative to interpretation of the data for Assessment Endpoint: I-Health of the Freshwater Benthic
Community. Specifically, the agency comment noted that" ... site -specific data, is expected to
carry a greater weight of evidence than the literature studies." The reliance on a weight of
evidence approach was selected to assign higher weighting to actual site observations relative to
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laboratory testing rather than comparing observed media concentrations to literature benchmarks.
This process takes into account site-specific factors such as those affecting bioavailability.
USEPA process guidance (1997) says that for ecological risk assessments that entail more than
one type of study (or line of evidence), a strength of evidence approach should be used to
integrate different types of data to support a conclusion. The strength of evidence provided by
different types of tests and whether one type of study should be more heavily weighted over
another should already have been established during Step 4 (study design) of the ecological risk
assessment process. In doing so, the data interpretation and analysis will be more likely to be
objective and unbiased. Additional information was provided in responses to USEPA
Attachment 2. general comments 5 and 6 (September 2000).
Weyerhaeuser and RMT maintain that the data indicate the health of the fresh water
macroinvertebrate community, specifically in terms of structure and function in support of upper
trophic levels, is not adversely affected relative to the reference creek.
3. The lack of apparent effects in the benthic community assessment should not trump the
toxicity test results on Hyalella azJeca, which indicated reduced growth in Hyalella azJeca at
the most contaminated locations. The toxicity to Hyalella azteca is further supported by
absence of these organisms at the toxic locations, while present elsewhere. Benthos ut MT-1
were dissimilar from benthos at MT-6 and MT-8. It is possible that benthos at MT-6 and
MT-8 have been altered by the contamination (or by physical properties of the wastewater
solids). Changes to the benthic community may represent loss of one or more sensitive
species. Revisions brought text from the appendix forward into the report but did not
enhance the discussion of the relative sensitivity to toxic chemicals between dominant
species. Suggested is to explore elevated metals in sediments as a potential cause of growth
reduction.
Please refer to response to USEPA Attachment 2, general comment 6 (September 2000). For
clarity. the text can be supplemented with an additional discussion of the relative sensitivity of
dominant species to sediment COPCs.
4. WHO TEQs for fish were not calculated. The best approximation was the WHO TEQs for
mammals, which may or may not overestimate toxicity to fish. Highest reported TEQs for
mammals are approaching the threshold of risk for literature-reported tissue residue
reproductive effects in sensitive fish species or sensitive life stages. Potential risk to fish
reproduction is an important consideration. Suggest calculation of a fish TEQ.
This comment represents a deviation from the assessment endpoints. and measurement endpoints.
as agreed upon in the Welch Creek Ecological Study Design and Addendum (RMT February
2000). Comparison of observed concentrations in fish tissues to conservative literature
benchmarks was not specified in the Study Design and as such was not represented in the two
previous draft versions of this BERA report.
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5. Dioxin WHO mammalian TEQs in surface water (Table 4-2) were as high as 9.8 ng/L at
MT-6 compared to laboratory experiments on brook trout (Salvelinusfontinalis) which
found reduction in survival of sac fry at exposures to 8 ng/L 2,3,7,8-TCDD (Walker and
Peterson, 1994). Growth of rainbow trout (Oncorhynchus mykiss) fry can be reduced at
levels of dioxin in surface water as low as 3.93 ng/L (Mehrle et al., 1988). Survival in adult
mosquitofish (Gambusia afjinis) was reduced at exposures to 3.1 ng/L of 2,3,7,8-TCDD
(lsensee, 1978; Isensee and Jones 1975). It is interesting to note that mosquitofish were
observed in Conaby Creek but were absent in Welch Creek during the fish community
survey (Table 7-6). The potential for concentrations of dioxin in surface water to impact
fish reproduction is an important consideration in the risk assessment. Suggest to add an
evaluation of the concentrations in surface water relative to toxicity data to Section 7.0 in
conjunction with discussion of site-specific surface water and wetland water toxicity testing.
The surface water concentration referenced in the USEPA technical review comment is
overstated by three orders of magnitude. As presented in Table 4-2 of the BERA, the maximum
observed dioxin TEQ (WHO mammalian) in surface water was 0.0098 ng/L in surface water
sample WCSW-02 collected at MT-6. Comparison of this maximum concentration to the
conservative benchmarks further supports the conclusions drawn from the direct toxicity testing
for Welch Creek surface water and wetland waters, where no adverse growth or survival effects
were indicated.
Regarding the comment about mosquitofish being absent in Welch Creek, we believe the
technically appropriate comparisons for impact focus on metrics identifying presence or absence
of reasonably similar communities, not presence or absence of a single species. In addition, it
would be inappropriate to conclude that mosquitofish are absent from Welch Creek based on the
results of one survey event. Not all species are expected to be observed at any one specific
sampling event. Lack ofmosquitofish in the 1999 Welch Creek survey is not unexpected in that
mosquitofish are typically not well represented in the boat shocking work due to inherent
difficulties with their habitat, size, and the shocking technique. Specifically, during shocking,
mosquitofish tum-up very close to shore and in brush that is usually out of reach from the boat.
In addition, centrarchids are usually more visible once the bottom is stirred. As such, they tend to
get netted first and smaller fishes (such as mosquitofishes) tend to sink out of sight or get lost in
the debris stirred up on each shocking approach. Lastly, the efficiency of boat shockers typically
declines with decreasing fish size due to effective surface area and electrical field density
relationships.
Mosquitofish have been observed in Welch Creek both historically and recently. Mosquitofish
were collected from Welch Creek between 1994-95. Most were captured by netting the shallows
in thick leaf litter/algae areas. In addition, during an electrofishing event in October 200 I, several
mosquitofish were observed near MT5 and MT6.
The results of the fathead minnow toxicity testing indicated that there was not an effect on growth
and survival of the fathead minnows exposed to Welch Creek surface water. The presentation of
the fathead minnow toxicity testing results can be supplemented to include a tabular summary of
COPC concentrations and physical/ chemical information for the corresponding surface water
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• •
samples. However. additional analysis of the data beyond the purposes for which it was collected
could lead to biased and/or conflicting. conclusions which could divert or confound the risk
characterization process (USEPA 1997). We propose to not add any additional comparisons or
tables to the BERA.
6. Concentrations in emergent insects were compared with concentrations in insects from a
lake in Northern Quebec. The relevance of comparison between a lake in Northern Quebec
and Welch Creek is questioned. Northern lakes are known for enhanced methylation of
mercury, hence concentrations of mercury in biota tend to be higher up north. The study of
northern Quebec may represent background in Quebec, but not in North Carolina. The
BERA is inaccurate in concluding that mercury in insects represents background levels
from atmospheric deposition in North Carolina. Atmospheric deposition is higher up north
than down here in the South. The statement suggesting that mercury in aquatic insects is
not associated with the facility is not supported by Canadian data and should be deleted.
Statement on Page 8-9 indicating that emergent insect data was from a national study is
incorrect and should be deleted. Repeated statements that mercury concentrations in
emergent insects were comparable to background should be deleted, due to lack of
comparability between literature data and Welch Creek.
Information regarding mercury concentrations in emergent insect tissues is not available for
Conaby Creek or the Roanoke River. Given the global distribution of mercury and its recognition
as a state-wide, as well as regional issue, remediation goals for mercury should not be derived
without adequate consideration for mercury background. Although the data supplied is from
Canada, it, combined with the background data from the Florida Everglades and Pettigrew State
Park in North Carolina, support the conclusions that have been dr~wn in the BERA.
7. The goals of Superfund cleanups are to protect human health and the environment and to
comply with ARARs. When specific ARA Rs are not available or may be insufficiently
protective, Superfund develops a reasonable maximum exposure scenario in the baseline
risk assessment that describes current and potential risk posed by the site to determine
what is necessary to achieve protection. The exposure assumptions and toxicity values used
for the Weyerhaeuser investigation, while conservative, are reasonable. The
characterization in the uncertainties section of assumptions made by the risk assessment as
of low confidence and upper bound estimates is inaccurate. EPA has an enormous effects
data base on dioxin for aquatic organisms. Site-specific tissue data have indicated that
dioxin can desorb from soils and sediments to become a source of exposure to receptors, as
evidenced by detection in tissues of biota. The uncertainties section must not exaggerate the
uncertainties associated with the conservative scenario. The 95 percent UCL should not be
described as an "upper bound" estimate of exposure, but rather should call it a "high-end"
exposure estimate. The same is true of intake rates used in the risk assessment.
Exposures and intakes characterized in the text as "upper bound" estimates will be modified as
requested.
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8. Statements that a probabilistic risk assessment would have resulted in a lessened estimate of
risk must be deleted, because a probabilistic risk assessment was not performed. Whether
the risk assessment represented an individual risk or a population-level risk was never
defined in the risk assessment. Exposure assumptions would need to be presented in much
greater detail, as explained in previous comments on probabilistic risk assessment, to
specify what type of risk assessment this was. EPA views the risk assessment as a risk to the
assessment endpoint (i.e., to a collection of populations) rather than to a population or to an
individual. PRGs based on central values (mean, median, CTE) of risk from a distribution
of variability might not he sufficiently protective of populations.
Statements referencing site-specific probabilistic risk assessment results will be reviewed and
removed, as appropriate.
9. RGOs should also be reported for the toxicity testing results. These are the range of the
highest concentration that had no effect on the endpoint to the lowest concentration that
affected the endpoint. An analysis of direct toxicity is lacking in this risk assessment.
Reduced growth of Hya/ella azteca was observed at transects MT-6 and MT-8. Table 7-lOa
indicates that direct toxicity was associated with elevated levels of chromium, coppt,r,
mercury, and nickel in wastewater solids at MT-6 and MT-8. Constituents associated with
direct toxicity should be carried forward as CO'cs into the FS.
In response to USEPA comments (Attachment 2. Objective 2, Comment 4) on the Welch Creek
Baseline Ecological Risk Assessment (RMT April 2000), a presentation of the toxicity testing
results was supplemented to include a tabular summary of COPC concentrations and
physical/chemical information for the samples evaluated in toxicity samples. However, the data
gathering activities for Assessment Endpoint# I were not designed to generate information to
derive a sediment RGO for direct toxicity. Setting chemical-specific RGOs based on toxicity
testing would imply that the observed effect is causally related and quantitatively correlated to the
observed chemical concentrations. In this specific instance. the sediment samples under
evaluation are physically and chemically complex; the observed reduction in growth response of
the organisms cannot be readily attributed to a specific chemical concentration. It is our opinion
that the use of this data is beyond the purposes for which it was collected could lead to biased,
conflicting, or superfluous conclusions which could divert or confound the risk characterization
process (USEP A 1997).
Additionally, this issue was discussed in the September 19, 2000 meeting, and it was agreed that
site-specific. chemical-specific RGOs would not be developed based on the available direct
toxicity data.
Specific Comments
1. Table 3-1, Summary of Ecological Risk Assessment Study Design for Welch Creek. Text
was not expanded to qualitatively describe the relative composition of the mixed
invertebrate samples. Qualitative information from biological field sample notes was
promised in response to comments. Table 3-1 still states that the measurement endpoint
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was emergent insects, when in actuality insufficient emergent insects were captured and the
analysis was based on infauna! organisms or larval stages of insects.
A qualitative description of the invertebrate species that comprise the individual mixed
invertebrate samples cannot be provided based upon the information that is available in the field
notes.
A footnote has been added to Table 3-1 for clarification. This table is a summary of the Study
Design. The collection of single emergent species organisms was intended, however, due to
insufficient mass of single species. mixed emergent insects were used in the alternative scenario
calculation for the barn swallow. Infauna! organism (chironomids) data were used as a surrogate
for the emergent insects in the conservative scenario calculations for the barn swallow. This
approach was identified in the approved Welch Creek Ecological Risk Assessment Study Design
and Addendum (February 2000).
2. Table 3-4, Summary of Life History for Wood Duck (Aix sponsa). The soil consumption
rate by the wood duck is indicated to be from USEPA (1993). However, USEPA (1993),
Table 4-4, Page 4-20 lists the soil ingestion rate for the wood duck as 11 percent (dry
weight). The value of 2 percent used in the assessment is an incorrect value for the source.
Suggest that the change be addressed in uncertainties section for how much difference it
would make to the risk assessment if incidental ingestion term were 11 percent of dry-
weight intake rate.
The reference will be corrected to reflect that the life history information that was used in the risk
calculations for the Wood Duck was from USEPA/ERT. dated March 1999. The uncertainty
section will be expanded to address the difference it would make in the risk assessment if
incidental ingestion of soil for the wood duck were 11 percent of the total daily dietary intake
rate.
3. Section 3.2, Ecological Risk Assessment Study Design, Page 3-5. Regulations governing
hazardous waste specify a regulatory decision framework which places a high burden of
proof on verifying that there is not an effect, i.e., potential risk versus proof of impact.
Suggested language change: "Therefore, the testable hypothesis for this endpoint will
evaluate ... " The term "confirm" emphasizes Type I errors, when the concern in this
regulatory context is Type II errors.
The referenced text is consistent with the approved Welch Creek Ecological Risk Assessment
Study Design and Addendum (February 2000). Hypotheses are typically phrased as a definitive
statement (either positive or negative) that are either confirmed or refuted (the "null" hypothesis).
This approach is consistent with the initial response to USEPA 's specific comment I in
Attachment 2 (September 2000).
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4. Section 4.1, Environmental Media Results, Page 4-2. It is an exaggeration to suggest that
dioxins are not dissolved in the water column. The small quantities that are dissolved are of
concern to EPA.
Clarification will be provided.
5. Section 4.1, Environmental Media Results, Page 4-2. The text states that the "toxic form of
chromium was not detected in sediment." The implication is that trivalent chromium is
non-toxic. This statement is incorrect and should be revised. Trivalent chromium can also
be toxic to biota.
The language will be revised to reflect that "Hexavalent chromium, the more toxic form, was not
detected in sediment."
6. Section 5.1, Migration and Exposure Pathways, Page 5-1. The diffusion of methyl mercury
from buried sediments up into the water column is an omission in Section 5.1, which should
also be addressed in the FS, if deeper sediments are more contaminated than surface
sediments used in the risk assessment.
A discussion of the potential for diffusion of methyl mercury from buried sediments into the
water column will be included in Section 5.1.
7. Some discussion was added (page 7-13) in response to the recommendation that the relative
sensitivity of the fathead minnow be discussed. While the cited reference (Elonen et
al.1998) is very relevant, please note two additional points. First, our comment focused on
the fathead minnow's sensitivity relative to the endangered shortnose sturgeon, and a
reference (Dwyer et al. 1999) was provided. Second, Figure 3 of Elonen et al. (1998)
indicates that the fathead minnow is the fourth most sensitive species out of ten used for
comparison purposes, and the paper indicates that the fathead minnow was approximately
8 times less sensitive to TCDD than lake trout, the most sensitive species evaluated to date.
The BERA 's statements that the fathead minnow was the most sensitive of the seven species
tested by that paper's author is correct, but this only partially addresses the our comment
on this issue.
Additional clarification will be provided regarding the sensitivity of the fathead minnow.
However. sensitivity relative to species inappropriate for coastal stream habitat typified by Welch
Creek and Conaby Creek will not be incorporated into the document.
8. Section 8.1, Hazard Quotient Estimation, Page 8-2. Preliminary remediation goals,
developed based on acceptable exposure levels, must incorporate an adequate margin of
safety. EPA considers the practice of setting exposure levels equal to (or greater than)
effects levels insufficiently protective, because effects levels great enough to be statistically
significant in a test might be great enough to result in changes at the population level, if the
power of the toxicity test was low. In ecological risk assessment, no safety factor or
modifying factor is used to adjust the toxicity reference dose. Suggested language change:
"Although ... LOAELs can be similarly influenced by experimental design, LOAELs,
I,\ WPMSN\J' JT\00-0S 1 (l(J\-W\UXXJS 1 ()().U.Q l 6.DOC 8
• •
involving relatively minor effects that are not directly associated with potential effects on
populations (i.e., not reproduction, growth, or mortality) might be appropriate for use in
risk management decisions, provided these are based on sufficiently sound studies." Text
on Page 8-22 stating that "LOAELs ... are more appropriate for use in risk management
decision making ... " should be deleted.
The text twill be modified to be consistent with text modifications in the comparable section for
the Final Baseline Ecological Risk Assessment for the Landfill No. 1 Area.
9. Section 8.4.2, Exposure Assessment, Page 8-21. The text implies that conservatism was the
reason for using a time-use factor of 100. The reason was not simply for conservatism but
because the complete risk characterization equation actually has both an exposure time and
an averaging time, although not shown because they typically cancel out. Because the time
animals were dosed in the toxicity study (i.e., averaging time) was less than a year, it is
inappropriate to assume that animals present for part of a year (i.e., exposure duration) will
not exhibit the effect. Text should be modified to remove the statement that time uS1, factor
of 100 percent is a screening-level assessment.
Statements that the time use factor of 100 percent is solely utilized in screening level assessments
will be removed from the text.
10. Section 8.4.2, Exposure Assessment, Page 8-20. Qualitative information on taxon in mixed
invertebrate samples was not provided.
See response to Specific Corrunent # I.
11. Some discussion was added (page 8-21) which addressed the our recommendation that the
alternative modeling include the likelihood that species will forage in what may be more
contaminated areas for a portion of the year. The uncertainty analyses now captures this
issue as a potential underestimate of risk, but with 500+ acres of settling ponds which likely
have higher concentrations of CO PCs (because they are closer to the ultimate source), this
caveat needs more emphasis (or data from the ponds to put it in perspective).
In response to USEPA's general corrunent 2. Attachment 2, on the Baseline Ecological Risk
Assessment (April 2000) the uncertainty discussion was expanded to describe the potential
underestimation/ overestimation of modeled ecological risk for those receptors whose foraging
range differs from the area represented by Welch Creek. However, alternative modeling with
additional COPC exposure outside of Welch Creek is not planned because:
■ as agreed to in the Welch Creek Ecological Risk Assessment Study Design Addendum
(February 2000), the conservative exposure scenario for ecological receptors evaluated
already assumes foraging entirely within the affected area of Welch Creek; and,
■ Risk management/remedy decisions for Welch Creek media can only be based on potential
risk associated with Welch Creek media.
This approach was discussed and agreed upon in the September 19, 2000 meeting.
!:I WPMSN\PJn()(). 05100\4Jll.1XXl5 J (Xµ4.o 16. DOC 9
• •
The current language in the uncertainty section can be modified to make clear that potential
ecological risk associated with foraging away from the Creek is unknown but could be greater
than that estimated for Welch Creek.
12. Section 8.6.1 0 Dioxin/Furans, Page 8-26. The severity and incidence ofa response depends
on the shape and slope of the dose-response curve. The text regarding the geometric mean
is improved in this version because it does not attribute a threshold of response to the GM.
Suggested is that Weyerhaeuser continue to present the GM as an example of a value in
between a NOAEL and LOAEL but not to interpret this value to have any toxicological
significance or to interpret it as a "bright line" for a PRG. EPA uses a methodology called
the Benchmark Dose Method to estimate a threshold, such as an effect dose to IO percent of
population, however, the BMD is rigorous and technically grounded versus the arbitrary
method of taking a geometric mean.
We respectfully request that the text that is currently provided in the BERA be accepted by the
USEPA. In our September 19, 2000 meeting, we feel that this issue was discussed and agreed
upon. and the text in the BERA is consistent with our agreement.
13. Section 8.6.2, Mercury, Page 8-27. Text states that as concentrations of mercury in
sediment reach I mg/kg that the production of methyl mercury by bacteria may cease. This
statement, implying that more mercury is good for the environment, is incorrect. The rate
of methyl mercury production increases rapidly at low total mercury concentrations as
concentrations in sediment rises and reaches a plateau somewhere around 50 mg/kg,
depending on the site.
The text does not conclude or imply that more mercury is good for the environment. The text
does conclude that the relationship between methyl mercury production and total mercury is not
linear.
Please also see the response to Attachment# I; Comment #26.
14. Table 8-11, Summary of Ecological COCs and Primary Sources of Risk, Page 8-39.
Statement that fish concentrations in Welch Creek are equal to local and regional
background should be deleted. Concentrations in Welch Creek fish are significantly
elevated above the reference station at greater than the 90'h percent confidence level.
The initial statistical evaluation indicated that there was a statistically significant (P<0.05)
interaction between individual forage groups and location. In light of the statistically significant
interaction, statements concerning any potential real statistical differences between all fish from
Conaby Creek and Welch Creek can not be made. Subsequent statistical evaluations were
conducted to determine where differences in body burdens of forage groups existed between
Conaby Creek and Welch Creek fish
Please refer to response to Comment #25.
l:\WPMSN\PJT~)(}.(}~ ')()l,4.N.OOOS!OOJJ-016.DOC IO
• •
15. Table 8-1, Ecological RGOs and Site Observations, Page 8-41. Table header is mistaken)~·
referring to the landfill.
The table header will be revised.
16. Section 9.1, Ecological Health of the Fresh Water Macroinvertebrate Community, Page 9-1.
Suggested is to arrange the text to consider the hydric soil community and the benthic
invertebrate community separately since they each have their own assessment endpoints.
According to the process guidance (USEPA 1997), the selection of assessment endpoints and an
agreement on the appropriateness of the assessment endpoints should be agreed upon in Step 3,
problem formulation, of the ecological risk assessment process. The entire process leading to site
investigation and risk characterization assumes the selection of appropriate assessment endpoints.
Assessment endpoints were agreed upon in the approved Ecological Risk Assessment Study
Design and Addendum (February 2000). Addition of assessment endpoints is not appropriate at
this point in the process.
17. Section 9.1, Ecological Health of the Fresh Water Macroinvertebrate Community, Page 9-1.
Statement in last 3 lines on Page 9-1 that indicates that observed reduction in growth of
Hyalella azteca in Welch Creek is somehow balanced out by lack of effects on mortality or
in the wetlands should be revised. Comment on the Draft BERA requesting an analysis of
the power of the RBP test has not been incorporated. (See General Comments No. 2 & 3.)
The agreed upon resolution of the initial agency comment on the Draft BERA, relative to the
power of the RBP test, was to solicit and include in revised BERA an independent agency review
of the benthic macroinvertebrate sampling, data interpretation. and conclusions. The independent
review was completed and results discussed in the revised BERA
The independent review supported that the general study design was adequate to compare the
benthic communities of Welch Creek and Conaby Creek. As such rilodification of the conclusion
relative to the ecological health of the freshwater benthic community, specifically in terms of
structure and function in support of upper trophic levels does not warrant modification.
18. Section 9.2, Health and Reproductive Capacity of the Fisheries Resource, Page 9-2. Suggest
to compare concentrations in fish tissue and surface water to literature effects data.
Suggest to evaluate the relative sensitivity of the fathead minnow versus other fish species
such as the sturgeon and mosquitofish. The lack of mosquito fish in areas where dioxin
water concentrations exceed values in the literature associated with mortality in adults may
be more than coincidental. (See General Comment 4) More evidence to support that
fishery resources are not at risk should be presented.
Please refer to our responses to General Comment #4 and #5. Site-specific survey data and
laboratory toxicity data supports that the fishery resource is not at risk.
I:\ WPMSN\P Jl\00-05 I 00\4-1\LOOOS l 004-1.016. DOC 11
• •
19. Appendix K, Toxicity Tests. Please comment on the acceptability of the fathead minnow
test considering that ten fish were apparently lost when the laboratory technician knocked
over several beakers on more than one day.
The fish that were lost during the test were from several different sample replicates from both
Welch Creek and Conaby Creek. These fish were not included in statistical analyses performed
on the results of the fathead minnow toxicity testing.
l:\WPf..lSN\PJT\OO.QS I00\4J\UXXl51004-i-016 DOC 12
• •
Appendix A
Review of ACOE Model Conclusions
I:\ WPMS N\PJT'-l)().QS l OO\-l4\L000510044-016.DOC
• •
This attachment presents a review and discussion of the ACOE conclusions (Scott. 2001 1). On the
following pages. the ACOE' s text is bold for the conclusions section of the report. and Weyerhaeuser' s
discussion of the conclusion is presented as regular shaded text.
From page 16, Scott, S.H. 2001. Sediment mobilization potential in the Roanoke River and Welch Creek, North
Carolina. ERD/Cl-!L TR-01-XX, U.S. Army Engineer Research and Development Center, Vicksburg,
Mississippi.
I:\ V.'PMS1'<'\J' Jl'll0-0:'i 100\4.J\lJ.lOOS l 00.14-016. DOC
• •
Review of ACOE Model Conclusions
(Scott, 2001; Section 5, page 16)
Numerical models are excellent tools for describing how a system works, not for predicting absolute
quantities. The analysis data presented in this report must be interpreted based on relative results
between the flow events, with an understanding of the uncertainty involved in modeling. Any
modeling effort will involve uncertainty based on limited field and verification data, channel
geometry data, and numerous assumptions that are necessary to simplify the problem at hand.
With this in mind, the following conclusions are drawn from the results:
Agree. Both the Weyerhaeuser and ACOE predictions include uncertainty. Neither model is calibrated to
flow measurements associated with the storm surge events (i.e .. Hurricane Dennis. Northeaster, and Wind
Tide events). The Roanoke River model likely involves less uncertainty since this model was calibrated
through a series of dam release flow events, including a simulated flood flow of approximately
18.000 cfs.
■ The storm surge events (Hurricane Dennis, Northeaster, and Wind) produce only surficial
erosion of the bed with a low potential for any significant scour to occur.
Agree. Limited sediment erosion was observed. Based on the actual TSS measurements made
near the mouth of Welch Creek during these events. the Northeaster and Wind Tide events
showed no elevated TSS above baseline flow conditions. Hurricane Dennis resulted in a limited
increase in TSS.
■ Model results indicate that the reaches of Welch Creek bounded by transects MT7 -GT15
have the highest potential for bed erosion.
Agree. Both models identify this zone (MT-7 to GT-15) as having the highest potential for bed
erosion. This section is narrow and shallow, which increases the water velocity (and shear stress)
through this portion of the creek.
■ The assumption of a steady, uniform erosion rate over the long duration flood hydrographs
may not be valid. Erosion rates may be much less or much greater for deposits under the
surface layer. Erosion depth is presented in this report only for comparison of results
between events.
Agree. Estimated erosion depths should only be used for comparative purposes between events
and not viewed as absolute quantities. The actual flood hydrographs may be of shorter duration
and the estimated erosion rate may vary with depth.
■ The erosion potential for the 2 and 5 year flood hydrograph simulations is comparable to
that of the storm surge events in both magnitude and location of peak erosion potential
(transects MT7 -GTlS).
Disagree with regards to the Hurricane Dennis conclusion. The 2 and 5 year flood simulations
are comparable to the Wind Tide and Northeaster storm surge events. However, there is a
l:\WPMSN\PJT'l)().Q5 l 'QW-l111Xl05100-i-l-016.DOC
• •
difference in opinion as to the magnitude of the flow associated with Hurricane Dennis.
Weyerhaeuser·s model predicts higher flow and shear stresses associated with Hurricane Dennis,
as compared to the ACOE's interpretation. The actual TSS measurements indicate that the Wind
Tide and Northeaster events were associated with stable sediments (i.e .. these TSS measurements
were comparable to background). However, a limited increase in TSS was observed in Welch
Creek during Hurricane Dennis.
■ The IO-year flood hydrograph simulation represents the highest erosion and mobilization
potential of all events, with higher peak mean reach erosion rates than the storm surge
events.
Partially agree. The 2 and 5 year flood events (or Wind Tide and Northeaster storm surge events)
are associated with stable sediments. For small, localized precipitation events, the IO-year flood
may represent the highest shear stress experienced by Welch Creek.
■ The 25, 50, and 100 year flood hydrograph simulations indicate an increasingly higher
erosion potential for the lower reaches of Welch Creek, but the uncertainty of the
magnitude of the downstream stage boundary reduces the probability for these events to
occur.
Agree. There is likely an increasing potential for erosion with larger storms. However. for
larger, more regional flood events, the Roanoke River level rises as well. This downstream
boundary effect of the Roanoke River reduces the sediment erosion potential within Welch Creek,
which is acknowledged by the ACOE.
Page 13 (last paragraph) of the ACOE report states ... "It is a valid assumption that 2, 5, and
IO year storm events could occur on a subregional basis in the Welch Creek watershed with an
average stage in the Roanoke River (0.9 feet). For the 25, 50. and l00 year flood events there is a
high probability that these storms would be regional, with increased water surface elevations in
the Roanoke River due to flood flows from tributaries and higher releases from Roanoke Rapids
dam. An increased stage in the Roanoke River would decrease the energy slope in Welch Creek
and thus decrease the erosion potential. Therefore, the IO year flood event most likely represents
the worst case of erosion potential for the flood events."
■ The erosion potential for Roanoke River bed sediments is low considering the type of
sediments and the regulated flows from Roanoke Rapids dam. Areas with the highest
concentrations of contaminates are generally natural depositional areas that will not be
adversely affected by the range of flows in the Roanoke.
Agree. The erosion potential for the Roanoke River bed sediment is low because, in part, the
river's flow is dam:controlled. This hypothesis was tested and verified by the ACOE through a
series of dam-release flow events that were monitored by the USGS and used to calibrate the
Roanoke River model. One of these dam-release events simulated a relatively large flood.
l:\WPMSN\Pfl"ll}(}.05100,-Ull1l005 IOOJJ.Qlb DOC 2
• •
Appendix B
Comparison of Potential Sediment Mobility Analyses
1: I WPMS N\PJTI00-05100\+l\Ll)()(}:'i 1 ()()44.Q 16. DOC
• •
WELCH CREEK
Remedial Investigation
MEMORANDUM -Comparison of
Potential Sediment Mobility Analyses
Beak Rer: 22018.1
Submitted to:
RMT Inc.
744 Heartland Trail
Madison, Wisconsin
Submitted by:
Beak International Incorporated
14 Abacus Road
Brampton, Ontario
December 2001
• •
COMPARISON OF ACOE'S AND WEYERHAEUSER'S
POTENTIAL SEDIMENT MOBILITY ANALYSES
The stability of Welch Creek sediments has been evaluated by Weyerhaeuser (Beak, 2001) and the
United States Anny Corps of Engineers (ACOE) (Scott, 200 I) as part of Remedial Investigations for
the Welch Creek and Roanoke River watersheds, respectively. Both evaluations utilize numerical
hydrodynamic and sediment transport models to predict shear stress and sediment stability under
various hydrologic conditions (i.e., storm surge and flood flows). Under many of these conditions, the
two models provide similar predictions. However, under certain conditions, the predictions and
corresponding conclusions regarding sediment stability differ. The objective of this memorandum is to
provide a side-by-side comparison of the two models to identify similarities in the modeling efforts
and differences contributing to deviations in conclusions. The comparison is presented in the attached
series of tables, as follows:
• Part A provides a side-by-side comparison of the hydrodynamic component of each model.
This component computes the shear stress that is applied to the sediment. It includes a
comparison of model type and grid, treatment of the wetlands, method of computing shear
stress, and model predictions for various storm surge and flood flow events.
• Part B provides a side-by-side comparison of the sediment transport component of each
model. This component computes the sediment stability based on the predicted shear stress
and estimated sediment shear strength. It includes a comparison of the parameter values used
to characterize the sediment, the method of estimating sediment shear strength, a comparison
of predicted and measured sediment stability, and a comparison of conclusions.
For the upper portion of Welch Creek, the two models predict similar shear stress and provide similar
conclusions regarding the stability of sediments. Both models predict that the sediments are stable in
this region.
For the lower portion of Welch Creek, the two models predict similar shear stress under low and
moderate hydrologic conditions. This similarity is significant as it demonstrates that differences in
model type and computational method have negligible affect on the overall conclusions.
Differences in conclusions about sediment stability are for the lower portion of the creek and arise
from deviations in model assumptions and parameter values. The two most significant differences are
the assumed degree of wetland flooding during extreme hydrologic conditions, and the parameter
values used to characterize sediment stability (i.e., sediment shear strength). These differences are
described as follows:
• The adjacent wetlands are an integral part of the hydrology of the Welch Creek system and
affect the volume of water transported through the creek channel. Although each model
accounts for wetland flooding, the degree of flooding differs, which affects the predicted shear
stress. The overall significance is that the Weyerhaeuser model tends to predict higher shear
stress for extreme storm surge and flood flow events, as compared to the ACOE model. The
Weyerhaeuser model bases its estimates of the degree of wetland flooding and associated
shear stress on field observations, local topography, water elevation records and total
suspended solids (TSS) measurements under varying hydrologic conditions.
Beak International Incorporated
Reference: 22018. I
December 200 I
RMT, Inc.
Welch Creek RI -Comparison of
Potential Sediment Mobility Analyses
' ,
• •
• Sediment stability is defined by comparing the shear stress of the flowing water to the
sediment shear strength. Stability is inferred when the shear stress is less than the sediment
shear strength. Potential mobility is inferred when the shear stress is greater than the sediment
shear strength. The sediment shear strength parameter values differ between the two models.
The ACOE model assumes constant shear strength, whereas the Weyerhaeuser model assumes
variable shear strength to reflect the different sediment properties observed throughout the
creek. The ACOE model also assumes a low shear strength inferred from laboratory
measurements, whereas the Weyerhaeuser model assumes a higher shear strength based
primarily on predicted shear stress and the timing of elevated TSS concentrations for
Hurricane Dennis. The evaluation of sediment stability is a developing field, and consequently
different shear strength values are expected depending upon the source and interpretation of
data.
The accuracy of each model can be assessed through a comparison between model predictions and
field observations. In 1999 and 2000, RMT Inc. conducted a field monitoring program to measure the
concentration of TSS within Welch Creek during three storm surge events and one baseline period.
One of the three storm surge events, Hurricane Dennis, was of sufficient magnitude to cause limited
sediment mobility, whereas the other two storm surge events did not. For these two non-transport
events, the TSS concentration within Welch Creek remained at baseline concentrations ranging from 5
to IO mg/L. The shear stress predictions are compared in Figures I and 2 for the Northeastern event
and Hurricane Dennis, respectively. The sediment stability predictions are compared to actual TSS
measurements in Figures 3 and 4. (Predicted shear stress and sediment stability for the 20 January
2000 wind event are presented in Figures 1.3 and 2.4 in the accompanying matrix). The main
observations from these figures are as follows:
• The ACOE model and Weyerhaeuser model predict similar shear stress during the
Northeastern storm surge event (Figure I) and the wind event (see Matrix Figure 1.3),
demonstrating similarity between the two models when wetland flooding is not a factor.
• The ACOE model predicts a lower shear stress during Hurricane Dennis than the
Weyerhaeuser model (Figure 2), demonstrating differences between the two models during
extreme storm surge events that are associated with wetland flooding.
• The ACOE model predicts sediment mobility for Hurricane Dennis (Figure 3), the
Northeastern event (Figure 4) and the wind event (see Matrix Figure 2.4) although the TSS
monitoring data indicates sediment mobility for only Hurricane Dennis. This finding indicates
that the ACOE model may under predict the shear stress during Hurricane Dennis and/or
under predict the shear strength of Welch Creek sediments. The ACOE suggest (Scott, 200 I)
that the peak TSS concentration was missed during monitoring of the Northeastern and wind
events. However, TSS monitoring data overlap with the occurrence of elevated TSS as
predicted by the ACOE model and indicates TSS was at baseline concentration throughout the
receding portion of both events.
• The Weyerhaeuser model correctly predicts sediment mobility for Hurricane Dennis (Figure
3) and sediment stability for both the Northeastern event (Figure 4) and the wind event (see
Matrix Figure 2.4). This finding indicates that the Weyerhaeuser model may provide a better
estimate of sediment stability during the monitored events.
The TSS monitoring data provides the strongest evidence to support the predictions on st:diment
stability from the Weyerhaeuser model.
Beak International Incorporated
Reference: 220 I 8. I
December 200 I
2 RMT, Inc.
Welch Creek RI -Comparison of
Potential Sediment Mobility Analyses
.. • •
Figure I I She..ar Stress During the Northeastern Evt:nl
1.0 -. e:.. Q8 . -Weyerhaeuser Results
-+-ACCI: Results
E Q6
;, Q4 • • • .c Q2 "' .._ ---
QO
QO Q2 Q4 Q6 Q8 1.0 1.2 1.4 1.6 1.8
Distance from Mouth (mi)
Figur,: 21 Shear Stress During Hurricane 0.-:nnis
1.0 -. e:.. Q8 . E Q6 ;,
• Q4 • •
'\
-Weyerhaeuser Results
-+-ACCI: Results -
'\ / ;Ji Q2 r-.___ -
QO
QO Q2 Q4
-
Q6
--------. -
Q8 1.0 1.2 1.4 1.6 1.8
Distanc,: frOm .\lonth (mi)
Figure 31 TSS During llurrir.anc Dennis
60
so i 40
£ 30
~ 20
10
0
8/JOfi9 QOO 8/JOm 12:00
□ ,......
-~ .._
•
1...; Shear Strength ...
Exceeded (I)
8/JI fJ9 QOO
□ Measured TSS
....-ACC£ Prediction (I)
-weyerhaeuser Predlcrlon
n
8/JI f/912:00 9! m Qm
l<'igure 4i TSS During lhe Northeastern Event
60
so i 40
2-30
"' ~ 20
10
0
I fl5KJJQOO
f
j
-,.,,. --...._
~
I film 12:00
□ Measured TSS
-+-ACCI: Predlcdon ... -weverhaeuser Prediction (2)
□ u u u
I f26KJJQOO I fl.6K1J I 2:00 I rDKJJQOO
( 1) The Weyerhaeuser model predicts that the shear stress will exceed the threshold shear
strength during Hurricane Dennis.
(2) The Weyerhaeuser model predicts that the shear stress will not exceed the threshold shear
strength during the Northeastern event.
Beak International Incorporated
Reference: 22018. I
December 200 I
3 RMT, Inc.
Welch Creek RI -Comparison of
Potential Sediment Mobility Analyses
Similarities:
Differences:
Discussion:
Similarities:
Differences:
Discussion:
Beak International Incorporated
Reference: 22018.1
December 200 I
•
•
•
•
•
•
•
•
•
•
•
•
EXECUTIVE SUMMARY -COMPARISON OF POTENTIAL SEDIMENT MOBILITY ANALYSES
HYDRODYNAMIC AND SHEAR STRESS MODEL COMPARISON
The two models predict similar shear stress for low to moderate storm surge and flood flow events where the flow is confined to the creek channel.
The two models predict different shear stresses for extreme storm surge and flood flow events that are associated with flooding of the wetland .
The similarity between the two models is significant as it demonstrates that differences in model type and computational method have negligible affect on the overall conciusions.
In the case of extreme storm surge events, such as for Hurricane Dennis, the Weyerhaeuser model predicts higher shear stress than does the ACOE model. Hurricane Dennis differs from the other events investigated for two
reasons. First, the wetlands adjacent to the creek were flooded during Hurricane Dennis (as indicated by both field observations and measured water elevations in the Roanoke River), whereas the other events are not associated
with wetland floodii)g. Second, the TSS concentrations measured during Hurricane Dennis were elevated above the baseline concentration for a short period of time, whereas the measured TSS concenirations were at baseline
levels during the other events. This latter point indicates possible mobilization of sediment only during Hurricane Dennis. These two distinguishing features of Hurricane Dennis are interrelated since wetland flooding during a
storm surge event could cause sediment mobilization due to increased shear stress in the creek induced by a greater volume of water flowing into (and subsequently out of} the creek to flood the wetlands. The difference between
the ACOE model and Weyerhaeuser model is attributed to the degree of flooding accounted for in each model. The ACOE model estimates a lesser degree of flooding and predicts lower shear stress than the Weyerhaeuser model
for Hurricane Dennis.
In the case of extreme flood flow events, the Weyerhaeuser model also predicts higher shear stress than does the ACOE model, but in this case, the ACOE model assumes a greater degree of wetland flooding in the upper portion of
the creek. Wetland flooding during a flood flow event decreases shear stress in the creek since the volume of headwater flow in the creek channel is reduced by the amount flooding into the wetland. The greater degree of wetland
flooding is attributed to the higher friction coefficient used in the ACOE model.
SEDIMENT TRANSPORT MODEL COMPARISON
The two models both predict the highest potential for sediment erosion in the vicinity of MT-7 and the low,st potential for sediment erosion upstream of MT-6 .
The two models predict different potentials for erosion in the vicinity of MT-7, particularly at low to moderate storm surge and flood flow events where the flow is confined to the creek channel.
In the case oflow to moderate storm surge events, the ACOE model predicts erosion, whereas the Weyerhaeuser model predicts none. The Weyerhaeuser model for sediment transport is based on field measurements ofTSS, which
indicated stable sediments for two low to moderate storm surge events. The ACOE model is based on PES laboratory test results for original and remixed sediment, which may have resulted in an over prediction ofTSS for the two
low to moderate storm surge events.
In the case of low to moderate flood flow events, the ACOE model predicts erosion, whereas the Weyerhaeuser model predicts none. The ACOE model equates the 2-yr and 5-yr flood flow events to the Hurricane Dennis and
Northeastern storm surge events since similar shear stresses are predicted.
In the case of extreme flood flow events, the Weyerhaeuser model also predicts higher shear stress than does the ACOE model, but in this case, the ACOE model assumes a greater degree of wetland flooding in the upper portion of
the creek. Wetland flooding during a flood flow event decreases shear stress in the creek since the volume of headwater flow in the creek channel is reduced by the amount flooding into the wetland. The greater degree of wetland
flooding is attributed to the higher friction coefficient used in the ACOE model.
Page 1 RMT, fnc.
Welch Creek RI~ Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
•
MODEL DESCRIPTION
Model:
Model grid:
Wetlands:
Friction coefficient:
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART 1:
ACOE
RMA2 (WES, 2000) -two-dimensional depth averaged
finite element hydrodynamic numerical model.
SAM (SAM, 2000) -integrated computer system used to
compute velocity and shear stress distribution.
Coincides with transects denoted by RMT. Creek width and
depth modified from field measurement (RMT, 1995).
Included -represented as part of the two-dimensional grid
within the RMA2 model.
Mannings n = 0.03 -average of depth varied coefficient
based on assumed value.
HYDRODYNAMIC AND SHEAR STRESS MODEL COMPARISON
WEYERHAEUSER
DWOPER (NOAA, 1985)-one-dimensional depth and
width averaged finite difference hydrodynamic numerical
model.
SEDTRAN (Beak, 200 I) -proprietary computer program to
compute sediment transport.
Coincides with transects denoted by RMT. Creek width and
depth determined from field measurement (RMT, 1995).
Included -represented as off-channel storage within the
DWOPER model.
Mannings n = 0.01 -calculated from 0.01 mm (medium
silt) grain roughness and assumed 5 cm bed form.
Page 2
DISCUSSION
Negligible difference. Although the two models differ in spatial resolution and computational method,
these differences will have a negligible affect on the overall conclusions.
Minor difference. As illustrated in Figure 1.1, the cross sectional area at each transect is 15% smaller in the
ACOE model than in the Weyer_haeuser model. A smaller cross sectional area will cause a greater predicted
shear stress.
Figure 1.11 Wclch Creek .Morphometry
Comparison ofWeycrhaeuscr's )lodel Grid and ACOE's .Modd Grid
120
"a I 00 I ---w,yerhaeuset s grid r
= I.\. I -ACQ'sgrid
t 80 I/ ""-'\ <
" flJ ~ -...----:11 ~ ____...____ ------. 40 ----......-.
< 20 '--'
0 0 " ro s-~ ~ "' "' .. ,,. M ~ y ::' e-i2: !;: 7 i2: !;: 7 7 !;: i2: .... ~ .... .... .... I.J I.J I.J I.J I.J I.J I.J I.J I.J I.J I.J
Transect
Significant difference. Although both models represent the wetlands, assumptions regarding the extent of
wetland flooding during extreme storm surge and flood flow events differ. For extreme storm surge events,
the Weyerhaeuser model predicts a greater extent of wetland flooding than does the ACOE model, whereas
for extreme flood flow events, the ACOE model predicts a greater extent of wetland flooding than does the
Weyerhaeuser model. This difference is significant to the overall conclusions, as discussed throughout this
comparison.
Significant difference. The differing friction coefficients between the two models results in a significant
difference in the extent of wetland flooding during extreme flood flow events since a higher friction
coefficient results in a greater water surface elevation within the upper portion of the creek. This difference
is significant to the overall conclusions, as discussed throughout this comparison.
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
•
MODEL DESCRIPTION
Shear stress equation:
Model calibration/validation:
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART 1: HYDRODYNAMIC AND SHEAR STRESS MODEL COMPARISON ( ... continued)
ACOE WEYERHAEUSER
_ll__ = 3.28 + 5.75 In( _!__) u. dH _ll__ = 25 In( 3.32 u, h)
U, V
From SAM (2000) applicable to rough beds, including From Yalin ( 1992) applicable to stationary, uniform, flat
coarse sand, gravel and cobble. beds with a hydraulically smooth (i.e., Re<5) flow regime.
Hydrodynamic model of Welch Creek was neither Hydrodynamic model of Welch Creek was neither
calibrated nor verified against fie1d measurements of flow, calibrated nor verified against field measurements of flow,
velocity or water surface elevation. velocity or water surface elevation.
A second model, developed for the Roanoke River, was
calibrated to field measurements of velocity and flow.
Page 3
DISCUSSION
Negligible difference. As illustrated in Figure 1.2, the difference between the ACOE and Weyerhaeuser
methods of computing shear stress is negligible.
Figure 1.21 Estimated Shear Stress,
Comparison of ACOE and Weyerhaeuser Methods
QS· ~ --Weyerhaeuser' s Method I n -o-04 --<>-ACCi' s Method I /'" ~ . . 03 " ____., " 00
" 02 ------" " <15 QI
QO
0 200 400 6(JJ 800 1,000 1,200 1,400 1,600
FJow (cfs)
Since neither model has been calibrated to field flow conditions within Welch Creek, neither model
provides a definitive conclusion. This is particularly true under extreme storm surge and flood flow events
when wetland flooding may be a factor. The degree of wetland flooding and magnitude of the friction
coefficient provide the greatest uncertainty, which can only be resolved through comparison to field
observations.
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
STORM SURGE
SIMULATIONS
Comparison of shear stress
predictions for storm surge
events not associated with
wetland flooding:
Beak International Incorporated
Reference: 220 I 8.1
December 2001
• •
PART 1: HYDRODYNAMIC AND SHEAR STRESS MODEL COMPARISON (, .. continued)
ACOE . WEYERHAEUSER
Events simulated: Events simulated:
• Wind Event (20-21 January 2000); and • Wind Event (20-2 I January 2000); and • Northeastern (25-26 January 2000). • Northeastern (25-26 January 2000) .
Upstream boundary: Upstream boundary:
• Welch Creek flow-constant at 25 cfs for both events. • Welch Creek flow-variable based on prorated gauged
tributary flows
• Wind Event -25 cfs;
• Northeasten -varies from 60 to I IO cfs during event.
Downstream boundary: Downstream boundary:
• Roanoke River water surface elevation -variable based • Roanoke River water surface elevation -variable based
on field measurements from USGS at highway 45 on field measurements from Weyerhaeuser at mill
bridge. monitoring pier near confluence with Welch Creek;
• Wind Event-peak water elevation of 0.9 ft, receding
1.6 ft over IO hours;
• Northeastern -peak water elevation 1.57 ft, receding
2.8 ft over 16 h·our.
Page 4
DISCUSSION
Minor difference. As illustrated in Figures 1.3 and I .4, the ACOE model and Weyerhaeuser model provide
comparable predictions for the two storm surge events that are not associated with wetland flooding (i.e., the
Wind Event and the Northeastern). The differenees between the two models are relatively small and likely
explained by boundary conditions, creek morphometry, friction coefficient and computational method.
This similarity is significant as it demonstrates that differences in model type and computational method
have negligible affect on the overall conclusions.
Figure 1.31 Shear Stress During the 20Jan. 2000 Wind Event,
Comparison of Weyerhaeuser and ACOE Results
030 ... --e-weyerhaeuser Results e:. . ~ ACO:. Results : 020 • ;;
• • ~ 0 -= 010 "' -.,. • -:: ,,____
000
---
000 020 040 060 080 1.00 1.20 1.40 1.60 I.BO
Di.stance from .Mouth (mi)
Figure I.4t Shear Stres~ During the 25 Jan. 2000 Northeastern,
Comparison of Weyerhaeuser and ACOE Results
030 · ~ -Weyerhaeuser Results
• --<>-ACCT Results _; 020 ft
"' • / ~ ..
"' 010 V --__,,. .,. I • :::. '-ef
ooo·
000 020 040 060 080 1.00 1.20 1.40 1.60 1.80
Distance from Mouth (mi)
(The shear stress values presented are the peak shear stress at each transect during the storm surge event).
RMT, Inc.
Welch Creek Rl -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
•
STORM SURGE
SIMULATIONS
Comparison of shear stress
prediction for storm surge
event associated with wetland
flooding:
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART 1: HYDRODYNAMIC AND SHEAR STRESS MODEL COMPARISON ( ... continued)
ACOE WEYERHAEUSER
Events simulated: Events simulated:
• Hurricane Dennis (30-31 August 1999). • Hurricane Dennis (30-31 August 1999) .
Upstream boundary: Upstream boundary:
• Welch Creek flow-constant at 25 cfs. • Welch Creek flow-variable based on prorated gauged
tributary flows;
• Hurricane Dennis-varies from 5 to IO cfs during the
event.
Downstream boundary: Downstream boundary:
• Roanoke River water surface elevation -variable based • Roanoke River water surface elevation -vafiable based
on field measurements from USGS at highway 45 on field measurements from Weyerhaeuser at mill
bridge. monitoring pier near confluence with Welch Creek;
• Hurricane Dennis -peak water elevation of 2. 75 ft,
receding 3.3 ft over 39 hours.
Page 5
DISCUSSION
Significant difference. As illustrated in Figure 1.5, the ACOE model and Weyerhaeuser model do not
compare for Hurricane Dennis. Hurricane Dennis differs from the Northeastern and wind events for two
reasons. First, the wetlands adjacent to the creek were flooded during Hurricane Dennis (as indicated by
both field observations and measured water elevations in the Roanoke River), whereas the other two storm
surge events are not associated with wetland flooding. Second, the TSS concentrations measured during
Hurricane Dennis were elevated above the baseline concentration for a short period of time, whereas the
measured TSS concentrations were at baseline levels throughout the other two storm surge events. This
latter point indicates possible mobilization of sediment only during Hurricane Dennis. These two
distinguishing features of Hurricane Dennis are interrelated since wetland flooding during a storm surge
event could cause sediment mobilization due to increased shear stress in the creek induced by a greater
volume of water flowing into (and subsequently out ot) the creek to flood the wetlands. The difference
between the ACOE model and Weyerhaeuser model is attributed to the degree of flooding accounted for in
each model. The ACOE model estimates a lesser degree of flooding and predicts lower shear stress than the
Weyerhaeuser model for Hurricane Dennis.
Figure 1.51 She.ar Stre:;s Ch.tring the 30 Aug. 1999 Hurricane,
Comparison of Weyerhaeuser and ACOE Resul~
l.(X) ':,' -----Weyerhaeuser Result5 {with flooding) i 080· ··•·.·Weyerhaeuser Result5 (without flooding)
• " ;;
" • 0 1Ji ... ' • '-
Q60 ----ACCE Results --
----------
\ -Q'IO. \/ Q20 r----.. ---
Q(X) . ... -·•················---···-··· --~.; .....................
Q(X) Q20 Q'IO Q60
.
QBO l.(X) 1.20 l.'IO 1.60 I.BO
Distance from .Mouth (mi)
. RMT, Inc.
Welch Creek R1 -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
•
FLOOD FREQUENCY
SIMULATIONS
Comparison of shear stress
prediction for moderate flood
flow frequency events:
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART 1: HYDRODYNAMIC AND SHEAR STRESS MODEL COMP ARI SON ( ... continued)
ACOE WEYERHAEUSER
Events simulated: Events simulated:
• 5-year flood flow; and • 5-year flood flow; and
• JO-year flood flow. • JO-year flood flow .
Upstream boundary: Upstream boundary:
• Welch Creek flow-variable based on Beak (2001) • Welch Creek flow-variable based on Beak (2001 );
with flows reduced by approx. 15% to remove • 5-year flood flow -496 cfs;
watershed area below highway 64 bridge; • I 0-year flood flow -667 cfs . • 5-year flood flow ---422 cfs;
• I 0-year flood flow -~567 cfs .
Downstream boundary: Downstream boundary:
• Roanoke River water surface elevation -constant at 0.9 • Roanoke River water surface elevation -variable at 1.5
ft m.s.l. based on long term average water surface ft m.s.l. plus 0.15 ft semi-diurnal tidal amplitude based
elevation on average water surface elevation during high flow
events.
Page 6
DISCUSSION
Minor difference. As illustrated in Figures 1.6 and 1.7, during moderate (i.e., 5-yr and 10-yr) flood flow
events the ACOE model predicts higher shear stress than does the Weyerhaeuser model. The difference
could be attributed to differing downstream boundary conditions (i.e., the downstream water elevation was
0.9 ft and 1.5 ft for the ACOE model and Weyerhaeuser model, respectively). Differing creek morphometry,
friction coefficients and computational method could also contribute to the difference.
This similarity is significant as it demonstrates that differences in model type and computational method
have negligible affect on the overall conclusions.
Figure 1.6: Shear Streis During the 5-Y r Flood l<low Event,
Comparison of Weyerhaeuser and ACOE Remits
1.0.
~£ ---a-weyerhaeuser Results ~ QB _._ ACcr Results
C ;; 06 -= ~ 04 .,, -• 02 -' " '-~ ~
00
OCO 020 040 060 080 I.CO 1.20 1.40 1.60 1.80
Distan•~ from Mouth (mi)
Figure 1. 71 Shear Stre;;;s During the 10-Yr Flood Flow Event, Comparison of Weyerhaeuser
and AC OE Results
1.0· i; -Weyerhaeuser Results ~ QS
0 ----ACCT. Results
.!: 06 "' -• : 04 ;;
1 02 :: ~
00
OCO 020 040 060
--
--cc: / ----------080 I.CO 1.20 1.40 1.60 1.80
Distance from Mouth (mi)
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
• •
FLOOD FREQUENCY
SIMULATIONS
Comparison of shear stress
prediction for high flood flow
frequency events:
Beak International Incorporated
Reference: 220 l 8.1
December 2001
,,-------•
PART 1: HYDRODYNA.i'\UC AND SHEAR STRESS MODEL COMPARISON ( ... continued)
ACOE WEYERHAEUSER
Events simulated: Events simulated:
• 50-year flood flow; and • 50-year flood flow; and
• 100-year flood flow. • 100-year flood flow.
Upstream boundary: Upstream boundary:
• Welch Creek flow -variable based on Beak (200 I) • Welch Creek flow-variable based on Beak (2001);
with flows reduced by approx. 15% to remove • 50-year flood flow-1,142 cfs;
watershed area below highway 64 bridge; • 100-year flood flow-1,391 cfs . • 50-year flood flow -~971 cfs;
• 100-year flood flow-~I, 182 cfs .
Downstream boundary: Downstream boundary:
• Roanoke River water surface elevation -constant at 0.9 • Roanoke River water surface elevation -variable at 1.5
ft m.s.1. based on long term average water surface ft m.s.l. plus 0.15 ft semi-diurnal tidal amplitude based
elevation .. on average water surface elevation during high flow
events
Page 7
DISCUSSION
Significant difference. As illustrated in Figures 1.8 and 1.9, during high (i.e., 50-yr and 100-yr) flood flow
events the Weyerhaeuser model predicts a significantly higher shear stress between river mile 1.0 and 1.6
than does the ACOE model. The difference is attributed to the higher friction coefficient used in the ACOE
model, which causes a significant increase in the water surface elevation and associated wetland flooding in
the upper portion of the creek. This reduces the flow in the main channel, thereby reducing the shear stress.
The Weyerhaeuser model does not predict the occurrence of flooding during these events; therefore the
entire flow is confined to the main channel.
Figure 1.8: Shear Stres~ During the 50-Yr Flood Flow E"·ent,
Comparison of Weyerhaeuser and ACOE Results
1.0 ',::' ----Weyerhaeuser Results ~ QB -e-ACC£ Results
" -:: (16 "' \ / "--" ' -" (14 .c ~\ / -----------' .Ar ~ "' " -'; / -~
0 (12 "V .., --..... 0.
(10.
ClCO (120 (140 (160 ClBO I.CO 1.20 1.40 1.60 I.BO
Distam.e from Mouth (mi)
Figure 1.9; Shear Stress During the 100.Yr Flood Flow Event,
Comparison of Weyerhaeuser and ACOE Resulll!
1.0 --':,' -e-weyerhaeuser Results i Q8 / --. \ -+-ACCE Results / \. 0 " ;; (16 \ ~ / "'-" ~--• " (14 "'\// -~ "' ----/ " .,/ '-..__ -.,, • (12 ., • -0::
QO·
ClCO (120 (140 (160 ClBO I.CO 1.20 1.40 1.60 I.BO
Distance from Mouth (mi)
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
• •
MODEL DESCRIPTION
Sediment erosion rate:
Erosion volume:
Model calibration/validation:
Beak International Incorporated
Reference: 22018.1
December 200 I
PART 2:
ACOE
E = 8.4366r-0.1447
Based on PES laboratory test results using both original and
remixed sediments.
Constant at 6.4 cc/g.
Sediment transport model calibrated to TSS monitoring data
obtained by RMT during three storm surge events. Model
calibrated for both critical shear stress and erosion rate.
SEDIMENT TRANSPORT MODEL COMPARISON ( ... continued)
WEYERHAEUSER
NIA
Variable ranging from l .4 to 6.4 cc/g.
Sediment transport model calibrated to TSS monitoring data
obtained by RMT during three storm surge events. Model
calibrated for critical shear stress.
Page 9
DISCUSSION
The Weyerhaeuser model evaluates the potential mobilization of Welch Creek sediments under differing
storm surge and flood flow conditions. The scope of the study did not include detailed analysis of the depth
or amount of solids potentially mobilized during periods of mobility, in accordance with the USEPA-
approved Work Plan Addendum.
Significant difference. The ACOE model computes the depth of erosion based on the estimated erosion
volume. As illustrated in Figure 2.2, the erosion volume varies significantly along Welch Creek, although
the ACOE model assumes a constant value that is equal to the highest value for the creek. This indicates that
the depth of erosion is over predicted by the ACOE model throughout much of the creek.
Figure 2.2: Estimated Volume of Sediment Removed Per Gram of Erosion
Comparison of ~rf'yerhaeuser and ACOE Estimates
7.0 ------,~ • ..... ~ 6.0 ,-\ /\ 0 ~ 5.0 I \/ \ / l 4.0 _/ • \ ..,.. -;; 3.0 • 0 _/ \ A / '-■. / -~ 20 l,/ 'rl < -"' 1.0 _.._. Weyerhaeuser' s Estimate --o--ACCE's Estimate I QO· M 0 N ~ ~ 0 N ~ ~ ~ ;i " "I ~ ,t " M N ;! i' >' >' >' >' r >' ~ >' >' C, C, C, :,: C, C, C, :,: C, C, C, C, :,: C, C, C, C,
Transect
Significant difference. As illustrated in Figures 2.3 through 2.5, the ACOE model predicts sediment
mobility during all three storm surge events, whereas both the measured TSS and Weyerhaeuser predictions
indicate sediment mobilization during only Hurricane Dennis (i.e., the 30 Aug. 1999 event), and sediment
stability during the Northeastern and Wind Event (i.e., the two storm surge events in Jan. 2000). The ACOE
model suggests that the actual TSS during these two events could be greater than that measured, however,
this is unlikely since the timing of the measured TSS coincides with the occurrence of peak TSS as
predicted by the ACOE model. This finding suggests that the ACOE model does not provide a reliable
match to the observed data.
RMI, Inc.
Welch Creek R1 -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
•
-MODEL DESCRIPTION
Model:
Sediment properties:
Sediment shear strength:
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART 2: SEDIMENT TRANSPORT MODEL COMPARISON
ACOE WEYERHAEUSER
SAM (SAM, 2000) -integrated system of computer SEDTRAN (Beak, 200 I) -dynamic solution to the two-
programs developed by WES. dimensional advection dispersion equation including
sediment erosion and deposition.
Sediment size 0.176 mm (fine sand) Sediment size 0.01 mm (medium silt)
Bulk density I.I glee Bulk density 1.04 to 1.18 glee
Dry density 0.16glcc Dry density 0.16 to 0.71 glee
Specific gravity 2.65 Specific gravity 1.33
Porosity 94% Porosity 47 to 88%
Sediment size and bulk density measured by ACOE from 2 Sediment size and bulk density measured by RMT ( 1995)
samples; dry density and porosity estimated from assumed from 18 samples; dry density and porosity estimated by
specific gravity. Beak (200 I) from computed specific gravity.
Constant at 0.017 Pa, based on the foJJowing: Variable ranging from 0.2 to 1.1 Pa, based on the foJlowing:
• PES laboratory test results using both original and • Literature indicates that the shear strength of soft
remixed sediments for two samples. cohesive sediments can range from 0.1 to 1.1 Pa;
The two sediment samples were obtained in the vicinity of • The ACOE laboratory test results using only original
sediments indicate that ihe shear strength of sediments MT--4 and MT-7. The ACOE tested each sample twice: first at MT-7 is greater than or approximately equal to 0.2 using the original sample in a semi-undisturbed state; and Pa; and second using a remixed and reconsolidated sample with the
coarse organic fractio:ri removed. Remixed sample were • The TSS field monitoring results indicate that the shear
tested smce a layer of leaf material, twigs and sticks strength of sediments near MT-10 is approximately
approximately ¼ inch thick was observed that tended to equal to or less than 0.4 Pa, and that the shear strength
naturaJJy armor the underlying sediments, whereby of sediments near MT-7 is approximately equal to or
potentiaJly increasing the shear strength. less than 0.6 Pa.
Page 8
DISCUSSION
Negligible difference. Although the two models differ in computational method, this difference wiJI have a
negligible affect on the overall conclusions.
Significant difference. The ACOE model assumes that the sediment composition throughout Welch Creek
is Wliform, whereas the Weyerhaeuser model recognizes the variability in sediment composition. Consider
as an example sediment dry density. As illustrated in Figure 2.1, the measured data indicates a high degree
of spatial variability in sediment dry density along Welch Creek. The lowest values occur within the pre-
1970 deposits near MT-IO where shear stresses are lowest, and the highest values occur within the
transitional zone near MT-7 where shear stresses are highest. The ACOE model assumes a constant dry
density that equal to the minimum value for the creek. Literature indicates that sediment dry density is one
of various factors affecting sediment stability. Low dry density indicates low shear strength, and high dry
density indicates high shear strength.
Figure 2.1: Dry Demity of Welch Creek Sediment
Comparison of W eyerhacuscr and. ACOE Estimates
1.0
I I -e-weyerhaeuser' s Esdmate -o--ACcr's Estimate 7 QB
:§ !', J\ -t Q6
-------I \/ \ _,/ -
"" = :5 Q4 ~ I ■ 'V -------->, -
-----• Q QZ ----
QQ ;:J 0 •-~ :1 0 ~ ~ " ~ "' ~ ~ ~ S: "' ;! ~ ,-' ,-' >" ;! >-' ,-' ~ >" >-' " " " :,: " " :,: " " :,: " :,: " " " " Transect
Significant difference. The differing estimate of sediment shear strength is highly significant to the overaJI
conclusions of sediment mobility.
Shear strength estimates based on the PES test are considered less representative of actual creek conditions
and subject to interpretation considering that: only two samples were tested; the PES method may not be
representative of actual in-field conditions; and a series of these tests were conducted on the remixed
sediments. Remixed samples were included in the ACOE analysis since the original samples contained a
large quantity of coarse organic material at the surface ihat, according to ACOE observations, played a
significant role in the erosion characteristics of Welch Creek sediments. They observed that at times, the
coarse organic material armored the underlying sediment whereby retarding erosion, and at other times, it
re-suspended the sediment as the organic material became dislodged. The process of remixing ihe sediments
to remove the coarse organic material renders the sediment different from the original.
Interpretation of shear strength based on the TSS monitoring may be considered the most representative
estimate available since these involve the undisturbed, native sediment and include the entire creek. Factors,
such as the natural variability in sediment composition and the potential influence of coarse organic
material, are addressed through the TSS monitoring program in conjunction with predicted shear stress.
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
/ •
STORM SURGE
SIMULATIONS
Conclusions regarding erosion
during storm surge events:
FLOOD FREQUENCY
SIMULATIONS
Conclusions regarding erosion
during flood flow events:
Beak International Incorporated
Reference: 22018.1
December 200 l
•
•
•
•
•
•
•
•
PART 2:
ACOE
The potential for erosion between MT-7 and GT-15 is •
significantly greater than that of other reaches;
Stonn surge events will result in trace surface erosion
with negligible erosion into the bed sediments.
ACOE
The sediments are likely stable upstream of MT-6; •
The potential for erosion between MT-7 and GT-15 is
greater than that of other reaches; •
The erosion rates for the 2-yr and 5-yr flood flow
events are estimated to be on the order of the Hurricane
Dennis storm surge event; •
A 10-yr flood flow event is considered by the ACOE as
the most likely worst case conditio~;
The predicted erosion at the higher flood flow events is
uncertain since the downstream water surface elevation
may be higher than the assumed 0.9 ft.
beak
SEDIMENT TRANSPORT MODEL COMPARISON ( ... continued) '
WEYERHAEUSER
The sediments in Welch Creek remain stable during
moderate storm surge events, and may be mobilized for
a short duration (i.e., a few hours) during extreme surge
events.
WEYERHAEUSER
Sediments are stable upstream of MT-6 during all flood
flow events considered;
Sediments are stable between MT-IO and MT-8 during
the 2-yr to 25-yr flood flow events, and of uncertain
stability during the 50-yr and 100-yr event;
Sediments are stable in the vicinity of MT-7 during the
2-yr to 10-yr flood flow events, of uncertain stability
between the 25-yr and 50-yr flocd flow event, and
potentially mobilized during the l00-yr flood flow
event
Page 11
DISCUSSION
The differing conclusions regarding erosion potemial during storm surge events are due to the following:
• The ACOE model derives erosion potential based on the PES laboratory test using both original and
remixed sediments, whereas the Weyerhaeuser model derives erosion potential based primarily on in-
field TSS monitoring;
• The ACOE results assumes that the TSS monitoring results are inconclusive since the ACOE model
prediction differ from the field measurements; whereas Weyerhaeuser assumes that the PES laboratory
results are inconclusive since the ACOE model prediction differs from the field measurements;
• The ACOE model predicts a lower shear stress for Hurricane Dennis (i.e., the 30 Aug. 1999 storm surge
event) than the Weyerhaeuser model, which is related to greater predicted wetland flooding.
DISCUSSION
The differing conclusions regarding erosion potemial during flood flow events are due to the following:
•
•
•
•
•
•
•
The ACOE model derives erosion potential based on the PES laboratory test using both original and
remixed sediments, whereas the Weyerhaeuser model derives erosion potential based primarily on in-
field TSS monitoring;
The ACOE assumes that the TSS monitoring results are inconclusive since the ACOE model prediction
differ from the field measurements, whereas Weyerhaeuser assumes that the PES laboratory results are
inconclusive since the ACOE model prediction differs from the field measurements;
The ACOE model predicts a lower shear stres:; for Hurricane Dennis (i.e., the 30 Aug. 1999 storm surge
event) than the Weyerhaeuser model, which is related to greater predicted wetland flooding;
The ACOE model equates the erosion potential for low and moderate flood flow events to Hurricane
Dennis since a low shear stress is predicted for both events, whereas the Weyerhaeuser model equates
the erosion potential for high flood flow events to Hurricane Dennis since a high shear stress is
predicted for both events;
The ACOE model predicts a reduced erosion potential during high flood flow events since significant
wetland flooding is assumed, whereas the We~1erhaeuser model predicts a higher erosion potential
during high flood flow events since the flow is assumed to be confined to the creek channel;
The Weyerhaeuser model over estimates the shear stress during high flood flows since flow is assumed
to be confined to the channel. Even so, the maximum shear stress is in line with that predicted for
Hurricane Dennis, which had a limited resuspension.
Maximum shear stress for all storm surge events, including Hurricane Dennis, were simulated to low
and moderate events. This is inconsistent with TSS field observations.
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
-•
MODEL DESCRIPTION
Model calibration/validation:
... continued
Beak International Incorporated
Reference: 22018.1
December 2001
•
PART2:
ACOE
SEDIMENT TRANSPORT MODEL COMPARISON ( ... continued)
WEYERHAEUSER
.
Page IO
DISCUSSION
Figure 2.3: TSS During the 30 Aug. 1999 Hurricane,
Comparison of Weyerhaeuser and ACOE Results
60
■ Measured TSS
50 ■ --o-ACa Prediction r-o... -weyerhaeuser Prediction (1)
i 40 l \ 30 0
"' "' ;-20 ~ Shear Strength p
10 Exceeded (lJ
■ -0,
8/30fl9 000 8/30fl9 1 2:00 B /31 fl9 0 00 8/31 fl'l 12:00 9A fi9 000
(I) The Weyerhaeuser model predicts that the shear stress exceeds the shear strength during H. Dennis.
Figure 2.44 TSS.During the 20Jan. 2000Wind Event,
Comparison of Weyerhaeuser and ACOE Results
60 .. Measured TSS 50 -o-ACcr Prediction
"' Weverhaeuser Prediction (2)
f 40
30
"' _/ '\ a!; -20 / 10 · ■ cl
0
1 /20/00000 1 /20/001 2:00 1 /21 /00 0 00 1 /21 /0012:00 1 /22 /00 0 00
(2) The Weyerhaeuser model predicts that the shear stress will not exceed the shear strength.
Figure 2.51 TSS During the 25Jan. 2000 Northeastern,
Comparison of Weyerhaeuser and ACOE Results
60
-■ Measured TSS
50 I' "'¾_ -o-ACC£ Prediction
(3) "' 40 rl1 ~ -weyerhaeuser Prediction 1 30 f "' a!; 20 j -10
■ ■ II ■
0
I /25 /00 0 00 1 /25 /00 I 2: 00 1 /26 /00 0 00 1 /26/001 2:00 I ril /00 0 00
(3) The Weyerhaeuser model predicts that the shear stress will not exceed the shear strength.
RMT, Inc.
Welch Creek RI -Sediment Mobility
Comparison of Potential Sediment Mobility Analyses
• • United States Department of the Interior
FISH AND WILDLIFE SERVICE
Ms. Jennifer Wendel
North Site Management Branch
Waste Management Division
Raleigh Field Office
Post Office Box 33726
Raleigh, Nonh Caroli.na 27636-372?
October 10, 2001
U.S. Environmental Protection Agency
Atlanta Federal Center
61 Forsyth Street, SW
Atlanta, Georgia 30303-3104
Dear Ms. Wendel:
w
i
The U.S. Fish and Wildlife Service (Service) has reviewed the July 2001 Revised Draft Remedial
Investigation Report (Revised Draft RI), Welch Creek Area, prepared by RMT, Inc. for the
Weyerhaeuser Company site in Martin County, North Carolina Service comments are provided
pursuant to the Fish and Wildlife Coordination Act, as amended (16 U.S.C. 661-667e). They are
intended as technical assistance for the U.S. Environmental Protection Agency's (USEPA)
investigations, assessments, and planning conducted pursuant to the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980, as amended ( 42 U .S.C. 9601
et seq.). Service comments do not represent any position that the U.S. Department of the Interior
may adopt concerning possible injury to natural resources under their trusteeship.
The Revised Draft RI addresses many of the issues identified by the Service as concerns with the
April 2000 initial draft of this docume_nt. The text is now clear on the scope and methodology of
the ISCO sampling, nature of the Welch Creek sills, Welch Creek wetland contaminant
migration, and significance of the fish consumption advisory in terms of risk management. Also,
the additional. sampling and analyses performed over-the past year adequately address the data
gaps with regard to surface water low-level mercury analyses (concentrations in Welch Creek do
not appear to exceed State surface water standards) and fish tissue mercury (concentrations in
Welch Creek fish are elevated relative to fish taken from the Conaby Creek reference site, but not
alarmingly so).
We did not see the following Service recommendation, previously identified in the initial draft
RI, addressed or resolved:
• We asked that flow conditions for the period when surface water samples were collected
from other Welch Creek locations (those reported in Table 6-3 and on page 6-9) be
provided. PCDDs/PCDFs in those samples range from 1 x 10-4 to 1 x JO·' ng/1 TEQ
(using TEFs from US EPA 1989); this range of values may be considered for modeling
baseflow loadings (instead of the 2 x 10-4 ng/1 value) once flows are known.
• •
Five issues related to Contaminants of Potential Concern (COPC) Distribution (Section 6) and
COPC Migration and Significance (Section 7) were identified by this review:
• Table 4-3 should probably have a footnote describing the sample location and analytical
results for sample ID's MT05LB-SUR-S, MT06MP-40-SUR-S, and MT0SMP-70-SUR-
S. The concentrations of2,3,7,8-TCDD in these samples greatly exceed those of any
other surface water sample. If these values are real and accurate, they would be the
appropriate maximum concentrations for inclusion in Section 6 (maximum COPC
concentrations by media) and they would drive all the risk quotients for water. If they are
not intended for that use, they should be deleted from the table or have their applicability
described in a footnote.
• The results of background samples for PCDDs/PCDFs in sediments (discussed on page 6-
5) should be augmented with a discussion of the background concentrations of
PCDDs/PCDFs determined in the Roanoke River well-upstream of the Weyerhaeuser
Plymouth mill. The background sediment samples for the Roanoke River study had
TEQs one to two orders of magnitude less than those reported for Conaby Creek. A
sediment screening value was derived for the Roanoke River study as 2-times
background, which results in 15.75 ng/kg TEQs, as compared to the 126 to 196 ng/kg
TEQs determined in Conaby Creek. More discussion of regional background values
would be helpful; there are certainly values far less than those of Conaby Creek nearby
which could be used for comparison to Welch Creek sediment values.
• Page 6-5 notes that TEQs could only be calculated for those samples where all of the
2,3,7,8-substituted PCDDs/PCDFs were analyzed. In fact, TEQs can be calculated for
those samples where only 2,3,7,8-TCDD and TCDF were measured as long as it is
acknowledged that these represent the minimum TEQs (i.e., the total TEQs for all
isomers are greater than or equal to the values derived from these two isomers). This is
important for two reasons. First, 2,3,7,8-TCDD and TCDF represent most of the TEQs in
many samples. Second, and important for the final RI, the highest TEQs for Welch Creek
would be :::5,670 ng/kg with this approach, rather than the 4,536 reported on page 6-6 and
in several tables. While the TEQs may be higher if all isomers were considered, this does
not diminish the fact that the TEQs for at least two samples exceed what is currently
being reported as the maximum (despite only having two isomers for TEQ calculations).
• The use ofTEQs based on the USEPA 1989 TEFs to calculate loadings can mask the
release of the most toxic isomers from Welch Creek sediments. Note that the surface
water dioxin data (Table 6-6) indicate that 2,3,7,8-TCDD and TCDF are detected in
Welch Creek surface water and they are below detection in the background Roanoke
River water (Table 4-3). Hence, the load of the most toxic isomers (as opposed to the
lower toxicity hepta-and octa-PCDDs/PCDFs) is a concern that should be discussed in
the document. This concern is made more clear by examining the USGS high-volume
sampling PCDD/PCDF data for all of the isomers. It could also be addressed by using
• •
the World Health Organization TEFs which do a better job of capturing the avian,
mammalian and fish toxicity of PCDDs/PCDFs than the older USEPA 1989 TEFs
• The Welch Creek data from the USGS high volume dioxin sampling should be integrated
into Section 7. Selection of waste loading input values should be supported by discussing
all of the available estimates for the input parameters, this is particularly important for the
PCDDs/PCDFs in surface water because of the lower detection limits employed by the
USGS. Their data can be used in loading calculations provided that the sampling was
performed at a flow event that can be used in the modeling. For example, the Roanoke
River background sampling for the USGS high volume PCDDs/PCDFs sampling effort
was about 0.00005 ng/1, or one-half the value used in the Roanoke River loading
calculations in Section 7. Also, the Welch Creek PCDDs/PCDFs concentration was
about 0.00095 ng/1, or about 4-times that used in the baseflow loading calcuiations of
section 7. The range of values and the flows at the time of sample collection should be
provided as context for the values ultimately used in loading calculations.
• The COPC Migration and Significance section conclusions are contrary to those of the
U.S. Army Corps of Engineers Waterways Experiment'Station which evaluated Welch
Creek sediment mobility as part of their lower Roanoke River assessments. More
discussion of the various approaches employed, and likely reasons for their disparate
conclusions on Welch Creek sediment mobility, would be helpful. Also, the Revised
Draft RJ's statements (on page 7-4 for example) that presence of wastewater solids in
Welch Creek provides evidence that local hydrological condition do not readily move this
material should be augmented with some additional discussion. For this statement to be
meaningful, it would seem to be necessary to know the volume of wastewater solids
present when discharge ceased in 1988. Unless the volume or depth of wastewater solids
is about the same, then material may well be moving in the system. Presence tells us that
much waste remains in this environment, not how much might have left the system over
the last decade. Secondly, we previously recommended that post-hurricane profiles of the
unconsolidated wastewater solids be prepared to determine whether they stayed in place.
Without some estimate of the original amount of wastewater solids in Welch Creek at the
time the discharge was removed or a comparison of sediment stability through time,
statements about sediment stability based on existence of waste are potentially
misleading.
The Service re-states the concern that the Draft Revised RJ's Executive Summary, and Summary
and Conclusions, reference to treatability studies and in situ treatment options should be removed
or augmented with a notation that ex situ options will also be studied. The statement appears to
pre-define the scope of feasibility study; Welch Creek's low gradient, slow flows, rural landuse,
and Weyerhaeuser's use of suction dredges to remove wastewater solids from their ponds
indicate that removal of the tons of wastewater solids in Welch Creek should be examined.
We still have concerns regarding the June 2001 Baseline Ecological Risk Assessment (BERA)
. Report, Welch Creek Area. Because this document is a final version, we will not detail the
• •
concerns here other than to note the following issues which appear unresolved from previous
correspondence:
• Much progress has been made in developing toxicity profiles for the CO PCs. Pertinent
literature has been identified and included in the derivation and discussion of toxicity
reference values (TRYs). While appropriate literature is considered, the Service
disagrees with some of the selected TRYs based on our interpretation of that literature.
For example, the PCDD/PCDF discussion (pages F-2 to F-21) for mammals correctly
identifies Heaton et al. (1995) and Tillitt et al. (1996) as applicable references and
proceeds to summarize these studies. However, the Heaton et al. (1995) lowest
observable adverse effect level (LOAEL) of 3.6 ng TEQs/kg body weight/day for adult
female mink is lower than the LOAEL (page F-8 and in the BERA calculations) of 10
ng/kg body weight/day based on Murray et al. 1979. The Service believes the Heaton et
al. (1995) reference to be the most applicable to deriving the TRY; this is not an esoteric
concern because it is three times lower than the TRY used now. If the Heaton et al.
(1995) reference is used, then the risk calculations for all mammals would increase by
about a factor of 3. In short, the appropriate literature has now been identified and
discussed (very good progress), but more work is still required to select the appropriate
TRY from the reviewed literature. We have a similar concern with the avian
PCDD/PCDF TRY
• Some discussion was added (page 7-13) in response to the Service recommendation that
the relative sensitivity of the fathead minnow be discussed. Whil_e the cited reference
(Elonen et al.1998) is very relevant, please note two additional points. First, our
comment focused on the fathead minnow's sensitivity relative to the endangered
shortnose sturgeon, and a reference (Dwyer et al. 1999) was provided. Second,. Figure 3
of Elonen et al. ( 1998) indicates that the fathead minnow is the fourth most sensitive
species out of ten used for comparison purposes, and the paper indicates that the fathead
minnow was approximately 8 times less sensitive to TCDD than lake trout, the most
sensitive species evaluated to date. The BERA's statements that the fathead minnow was
the most sensitive of the seven species tested by that paper's author is correct, but this
only partially addresses the Service's comment on this issue.
• Some discussion was added (page 8-21) which addressed the Service's recommendation
that the alternative modeling include the likelihood that species will forage in what may
be more contaminated areas for a portion of the year. The uncertainty analyses now
captures this issue as a potential underestimate of risk, but with 500+ acres of settling
ponds which likely have higher concentrations of CO PCs (because they are closer to the
ultimate source), this caveat needs more emphasis ( or data from the ponds to put it in
perspective).
We appreciate the opportunity to provide these comments and look forward to working with you
to resolve them at the late October meeting for this site. The Revised Draft RI and Final BERA
certainly address many of the concerns and recommendations we have previously voiced; we
appreciate the USEPA's, RMT, Inc.'s and Weyerhaeuser's attention to those and hope for a
• •
productive resolution to the remaining issues outlined in this letter. If you have any questions
regarding Service comments, please contact me at 919/856-4520 x.21 or via e-mail at
tom_ [e-mail].
Sincerely,
1:3::;r.a
Ecologist
References:
Dwyer, F.J., D.K. Hardesty, C.G. Ingersoll and D.W. Whites. 1999. Assessing Contan1inant
Sensitivity of American Shad, Atlantic Sturgeon and Shortnose Sturgeon. Interim Report -April
1999. U .. S. Geological Survey, Biological Resources Division, Columbia Environmental
Research Center, Columbia, MO.
Elonen, G.E., R.L. Spehar, G.W. Holcombe, R.D. Johnson, J.D. Fernandez, R.J. Erickson, J.E.
Tietge and P.M. Cook. 1998. Comparative toxicity of2,3,7,8-tetrachlorodibenzo-p-dioxin to
seven freshwater fish species during early life-stage development. Environ. Toxicol. Chem. I 7:
472-483.
Heaton, S.N., S.J. Bursian, J.P. Giesy; D.E. Tillitt, J.A. Render, P.O. Jones, D.A Verbrugge, T.J.
Kubiak, and R.J. Aulerich. 1995. Dietary exposure of mink to carp from Saginaw Bay, Michigan.
I. Effects on reproduction and survival, and the potential risks to wild mink populations. Arch.
Environm. Contam. Toxicol. 28: 334-343.
Murray, F.J., F.A. Smith, K.O. Nitschke, C.G. Huniston, R.J. Kociba and B.A. Schwetz. 1979.
Three-generation reproductive study of rats given 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in
the diet. ToxicoLAppl. Pharm. 50: 241-252.
Tillitt, D.E., R.W. Gale, J.C. Meadows, J.L. Zajicek, P.H. Peterman, S.N. Heaton, P.O. Jones,
S.J. Bursian, T.J. Kubiak, J.P. Giesy, and R.J. Aulerich. 1996. Dietary exposure of mink to carp
from Saginaw Bay. 3. Characterization of dietary exposure to planar halogenated hydrocarbons,
dioxin equivalents, and biomagnification. Environ. Sci. Technol. 30: 283-291
• • cc:
Dr. Garland Pardue -FWS, Raleigh, NC
Mr. Greg Hogue, REO, DOI/OEPC, Atlanta, GA
Dr. Diane Beeman, FWS, AES/TS-EC, Atlanta, GA
Mr. Jerry Holloman, FWS, Roanoke River NWR, Windsor, NC /
Mr. Lynn Wellman, USEPNETAG, Atlanta, GA
Ms. Sharon Thoms, USEP A, Atlanta, GA
Dr. Tom Dillon, NOANHAZMAT, Atlanta, GA
1'4s Brenda Beatl), CDfvf Fedetttl P1ograt113, Bottldct, CO
Mr. Nile Testerman; NCDSWM-Superfund Section, Raleigh, NC
c:\wp9.0\weyer8.wpd
Integrat.
Environ 1tal
Sulutinns
August 31, 2001
Ms. Je1rnifer Wendel
Remedial Project Manager
~-µ__:r-
•
744 Heartland Trail 53717-1934
P.O. Box 8923 53708-8923
Madison, WI
Telephone; 608-83 1-4444
Fax, 608-831-3334
United States Environmental Protection Agency, Region IV
61 Forsyth Street, SW
SUPERFUNO SECTION Atlanta, GA 30303-3104
Subject: Request for Time Extension
Final Remedial Investigation and Baseline Ecological Risk Assessment Reports
Former Landfill No. 1, Weyerhaeuser Company, Martin County, North Carolina
Dear Ms. Wendel:
In a letter dated August 1, 2001, the United States Environmental Protection Agency (USEPA)
provided c01mnents on the final remedial investigation (RI) and baseline ecological risk assessment
(BERA) reports for the above-mentioned site. In that letter, you requested that page revisions for both
documents be submitted to USEP A within 30 days of the receipt of the USEP A comments.
Since receiving the USEPA comments, Weyerhaeuser and RMT have been preparing responses to the
comments, and discussing the comments in detail with you to prepare final documents that can be
approved by the USEP A. In reviewing and discussing the comments, the North Carolina
groundwater standard for dioxin is unclear and a revised standard is currently proposed. As a result
of this, we have not reached resolution as to how to appropriately finalize the documents.
Consistent with telephone discussions with you regarding this issue earlier today, on behalf of
Weyerhaeuser, RMT is requesting that a time extension of 30 days be granted to continue discussions
with the USEPA regarding how to most appropriately address this issue. Please approve this time
extension by signing in the space provided below.
If you have any questions, please call.
Sincerely,
RMT, Inc.
stopher D. Krause
Senior Project Manager
Enclosures
cc: Rodney Proctor -Weyerhaeuser Company
Jeff Stamps -Weyerhaeuser Company
Lynn France -CDM Federal
Nile Testerman -NCDENR
~tb~/--
Principal-in-Charge
Approved: Jennifer Wendel
I:\ WI '!vlSN \ l'JT\00-05 100 \46 \ l.000510046·003.DOC
' ·1 • • I
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
August l, 200 I
Rodney Proctor
REGION 4
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
-··-·--A TLAN.TA,_\.LL,u.tu.iJ"" 30303-8960
ID), [E (G [E ~ WJ le fru
lru AUG -3 2llOI l!JJ
g~~c~o
2
r~ Environment.~filil~-RFUND SECTION
Weyerhaeuser Company
PO Box 9777
Federal Way, WA 98063-9777
Re: Review of the Revised Remedial Investigation Report (RI) and the Revised Baseline
Ecological Risk Assessment (BERA) documents, Landfill l Area, Weyerhaeuser Martin
County Facility
Dear Mr. Proctor:
The United States Environmental Protection Agency (EPA) has completed it's
review of the above referenced documents. Both documents do a good job in addressing
previous EPA comments made on the draft reports. However, a few modifications are
necessary before the documents can be approved as Final. EPA comments on the Revised
RI report are included as Attachment l to this letter, and comments on the Revised BERA
are included as Attachment 2.
To avoid duplication, comments on the Baseline Ecological Risk Assessment are
included as the separate Attachment 2, and are not repeated for the summary of the BERA
included in the RI Report. However, Section 8 of the RI Report, which summarizes the
BERA, should be modified to appropriately reflect the comments made on the BERA.
In general, the comments are minor and should require only page modifications.
Therefore, a re-submital of either of the documents in their entirety is not required. For
the RI, the major revisions requested involve the calculation of risk for the Future
Residential Groundwater use scenario, and for the discussions in the uncertainties sections
of the Risk Assessment. For the BERA, the majority of comments require minor
rewording in the uncertainties discussions.
RT
• •
Please submit page revisions for both documents, as appropriate, within 30 days of
receipt of this letter. If you have any questions, please feel free to call me at [phone].
cc: Jeff Stamps, Weyerhaeuser
Nile Testerman, NCDENR
Tom Augspurger, USFWS
Lynn France, CDM Federal
Kathy Huibregtse, RMT
lcil
Wendel
Remedial Project Manager
• •
Attachment I
EPA Comments on the Revised RI Report
Landfill I Area
Weyerhaeuser Site, Martin County North, Carolina
General Comment
I. Section 6.1.2, page 6-6, Section 7.3.3, page 7-12 and Section 9, page 9-2. These
sections states that since 2,3, 7,8-TCDD was not detected in any groundwater sample,
no groundwater quality standard was exceeded. Please remove this language from
these sections. The state's groundwater standard for dioxin, makes no mention of the
2,3,7,8 congener; rather, it lists the standard as "dioxin -2.2 x 10·10 rhg/L." The State
of North Carolina 2L standard for dioxin has been defined as the total Dioxin, as
calculated by the TEQ Therefore, the State ground water quality standard has been
exceeded at FL-03-1, FL-04-1, FL-05-1, FL-06-1, FL-06-02, FL-07-01, FL-08-01,
FL-09-01, FL-09-02 and FL-I 0-0 I. In addition, the groundwater standard was
. exceeded at the up gradient monitoring wells FL-01-0 I, FL-01-02, FL-02-0 I and FL-
02-02, at levels similar to those in downgradient wells.
Specific Comments
I. Executive Summary, page iii. Please discuss the results of the carcinogenic risk
calculations for Residential exposure to ground water in the executive summary.
1. Section 6.1.3, page 6-12. Previously, EPA asked for clarification of what is meant by
literature values with respect to predicting mercury methylation rates. No references to
the stated values are provided.
2. Section 7.1.2, page 7-4. Please include a child resident receptor, in addition to the
adult receptor already included, for exposure to groundwater. Also, calculate remedial
goal options (RGOs) for non-carcinogenic chemicals of concern (COCs) using child
resident exposure assumptions; use adult resident exposure_ assumptions for
carcinogenic COCs. This combination of receptors yields the lowest, most protective
groundwater RGOs. ·
3. Table 7-1. The exposure point concentrations for groundwater were calculated as the
means of the concentrations of contaminants in the shallow and intermediate monitor
wells. This would be appropriate if these wells were, according to Region 4 policy, "in
the highly concentrated area of the plume." No mention ofa contaminant plume was
found Lacking a discernable plume, Region 4 policy is to use the lower of the
maximum concentration and the 95% UCL on the mean. Please recompute the
exposure point concentrations for groundwater and recalculate risk accordingly.
I'
,,
• •
4. Section 7.3.3, page 7-12. The text should state that the dioxin TEQ concentration
exceeds the EPA residential target soil level for dioxin TEQ (1 ppb). The change was
made in the Executive Summary.
5. Section 7.2.2, page 7-7 and 7-8. Previously,'EPA requested that discussion of
alternative Cancer Slope Factors for dioxin be limited to the uncertainty discussion in
the risk assessment. The language was not moved, just duplicated. Please remove the
discussion from Section 7.2.2, beginning with the sentence "There is considerable ·
debate. " through the rest of this paragraph.
6. Section 7.4, page 7-14, Second bullet. Previously, EPA noted that data qualified
with a "J" indicating estimated may mean that the actual value is higher or lower, not
necessarily "biased high." The change was made on p.7-15. Please make the change
on p. 7-14 as well.
7. Section 7.4, page 7-13. The statement that using toxicity values with low confidence
ratings and high uncertainty factors typically results _in an overestimate of risk implies
that the "true" risk is known. Since we are unsure of the "true" risk, the statement is
unsupportable. The.same holds for the statement regarding extrapolation of data from
animals to humans. Please remove these statements form the uncertainty section, or
revise the language to state that the "true risk" is either over or under that calculated
in the RI.
l 0. Table 8-21:
• The Dioxin TEQ Range for the conservative scenario using the EPA ITEF
method should be 0.00003.§ to 0.00077
• The Mercury range for the conservative scenario should be 0.04 to 15.3
Table 8-22: Please re-label the Table as the Wet land Portion ..
Table 8-23:
• Cover Soil: Conservative· Dioxin Range-ITEFs-should be 0.00003.§ to
0.00077
Alternative Dioxin Range-ITEFs-should be 0.00005 to 0.0011
Please fill in range, mean and background (if availabl.e)
Wetland Soil: All ranges are incorrectly reported. The soil RGO ranges from
8-21 are reported, please substitute with the correct numbers from Table 8-22.
11. Appendix N, Standard Table 2-4. Please include the Ground water ARARS and .
TBCs to this Table.
• •
Attachment 2
EPA Comments on the Revised Baseline Ecological Risk Assessment
Landfill I Area
Weyerhaeuser Site, Martin County, North Carolina
General Comments
I. Some degree of conservatism in a baseline risk assessment is appropriate.
Conservatism is appropriate in the risk assessment in order to protect local populations
and communities of biota. Protecting at the median exposure level to a population
using the LOAEL as the benchmark may or may not be protective of a population,
because the dose-response curve and the characteristics of the populations are often
unknown. Text should be reworded to take out statements implying that the
alternative scenarios and LOAELs are the "more appropriate" assumptions for risk
management decisions (e.g., Page 8-2, 3'd paragraph; Page 8-3, line 3; and Page 8-26, ·
line 16) Text in the 2"d full paragraph on Page 8-25, which indicates that
conservatism is not appropriate in remedy decision-making should be revised.
2. Results of toxicity testing must not be interpreted as non-toxic due to background.
B~ckground comparisons address the question of whether the constituent is site
related. Risk assessments (toxicity tests, etc.) address the question of potential
adverse effects. Background constituents can have associated potential adverse health
effects. The issues of background and toxicity must be kept separate. Chemicals for
which the ERA predicts a potential risk using site-specific biological data, cannot be
eliminated from a risk assessment based on background. Eliminating for background
is a risk management consideration. In some cases background levels are not
necessarily protective. Conclusions regarding background can be addressed briefly in
the uncertainties section but should not be overemphasized or misinterpreted.
3. The red-tailed h_awk, red fox, and barn owl were chosen for their diet's inclusion of
small mammals. The tissue data for the short-tailed shrew was not included in the risk
calculations. The higher concentrations of site-related constituents measured in the
short-tailed shrew are not anomalous but are as a result of the shrew's lifestyle and
feeding strategy, which has been observed to cause higher concentrations in shrews
than in mice and voles for many types of contaminants in soil (Johnson et al, 1996).
The uncertainty section should address how the results of the risk assessment may
underpredict actual risk because the shrew sample was not included. The uncertainty
section addresses a diet of entirely shrews but does not address the more likely
scenario for shrews in a portion of the diet. The text presents a condition of no shrews
in the diet at all as a "more likely" scenario. It is unreasonable to suggest that the diet
would lack shrews entirely. Current risk estimates underestimate reasonably likely
exposures.
• •
Specific Comments
I. Executive Summary, Pages ii through iii. Unless a probabilistic risk assessment is
part of the report, it should not be mentioned in the executive summary.
2. Section 8.2.1, Conservative Risk Estimates for Upland Portion of Landfill No. 1,
Pages 8-4 through 8-8. The lack of site-specific background information adds
considerable uncertainty for cover soils. Aluminum in the cover soils is generally
higher than in the surrounding wetlands, and the presence of elevated aluminum is
generally associated with elevated concentrations of other COCs in soils. Aluminum
salts are commonly used in wastewater treatment processes. The evidence supports
that aluminum in cover soils might be site related versus associated with background
levels. Text on Pages 8-6 through 8-8 stating that "observed aluminum concenfrations
are consistent with naturally occurring concentrations" should be revised or deleted.
The wording on Page 8-I 4 "Aluminum, although resulting in an alternative hazard
quotient greater than 1.0, is present in soils at concentrations consistent with average
concentrations in Eastern United States soils." is preferred.
3. Section 8.2.2, Conservative Risk Evaluation for Wetland Portion of Landfill No.
1, Page 8-10; 8-13. Please remove the comparisons made between concentrations in
wetland soils from Landfill I with concentrations in U.S. soils. The Landfill I wetland
soils concentrations should only be compared to the concentrations in wetland soils of
the Roanoke River.
4. Section 8.4.1, Uncertainty Analysis, Characterization of Affected Media, Page 8-
20. The upland soils and wetland soils potentially contain numerous compounds other
than those identified as COPCs. The uncertainties section should discuss this point.
Tentatively identified compounds are one example.
5. Section 8.4.2, Exposure Assessment, Pages 8-21 through 8-22. The text discusses·
certain data points as outliers when insufficient evidence is provided, other than the
fact that they are higher than others. It is not unusual for a landfill to have non-
uniform distribution of contaminants. Also, tissue concentrations in wetland biota are
expected to vary with concentrations in wetland soil, which will explain the observed
variation for dioxin TEQ and chromium.
6. Section 8.4.2, Exposure Assessment, Pages 8-23 through 8-24. The body weights
and food ingestion rates used for the conservative scenario are not unrealistic. They
are similar to wildlife models in Sample and Suter ( 1994). Please revise the discussion
in this section.
7. Section 8.4.2, Exposure Assessment, Page 8-25. Text in paragraph 3 states that the
risk assessment results. for both the conservative and alternative scenarios represent an
upper-bound estimate of risk. Although the potential risk estimated with the
• •
conservative scenario is a high-end estimate of risk, neither ihe conservative scenario
or the alternative scenario are upper bound estimates because there are higher
estimates of exposure and higher estimates of toxicity in the literature than were used
in the Landfill I risk assessment. Please revise the discussion in this section.
8. Section 8.4.3, Uncertainty in Toxicity Assessment, Aluminum, Pages 8-26
through 8-27. Aluminum bioavailability is primarily a function of pH. Any pH
information for the landfill soil should be provided. The main point of the appendix on
· aluminum in the draft Eco Soil Screening Guidance was that aluminum bioavailability
depends on pH. However, pH is not specifically discussed for the landfill. If no pH
information is available, a statement to this effect should be added.
9. Section 8.4.3, Uncertainty in Toxicity Assessment, Chromium, Page 8-27.
· Chromium is primarily of potential concern in cover soils, yet no measurements-of
cover soils are available to confirm the assumption that it was trivalent chromium.
The argument that reducing conditions in sediments can convert hexavalent chromium
may apply to wetland soils but not to the upland soils. Section 8.4.1 should discuss
the uncertainty associated with lack of characterization of hexavalent chromium in
soils and biota. According to the meeting/conference call on April 26, 200 I, EPA was
expecting a footnote on the risk characterization tables for chromium directing the
reader to the uncertainties section where calculations for both trivalent chromium and
hexavalent chromium would be presented . .The TRY for hexavalent chromium was to
be presented in the uncertainties section. The uncertainties section does not present
the value of the alternative TRY or the value of the hazard quotient when the
alternative TRY is used. It only states that the hazard quotient would be 4 times
greater.
IO Table 8-20, Range of Ecological RGOs for Wetland Portion of the Landfill No. 1
Area, Page 8-65. This.Table may need revisions:
RGO ranges for dioxin TEQ (WHO mammalian) and chromium for the American
woodcock are the same for the conservative and alternative scenarios. Body weights
and ingestion rates are the same in Appendix K for the alternative and conservative
scenarios for the American woodcock.
The RGO for mercury for the barn owl was 0.2 mg/kg in the December 2000 draft
ERA It has changed to 1.2 mg/kg in the final ERA· The change is because a value of
0.0158 was used for the mercury BAF in small mammal tissues for wetland soils.
Table 4-16 lists the correlation as negative for mercury in small mammal tissues in
wetland soils. The RGO for the barn owl is the product of the TRY and the body
weight divided by the product of the BAF for small mammals and the ingestion rate.
The BAF for small mammals is based on the average concentration in tissues divided
by the average concentration in wetland soils, because the regression in Appendix D
was not significant (Table 4-16). The average concentration of mercury in small
mammal tissues is 0.0458 mg/kg. The average concentration in wetland soils in
• •
FLWS-01, FLWS-03, FLWS-05, and FLWS-06 is 0.479 mg/kg. The BAF for small
mammals is 0.0956. The RGO is 0.0064 mg/kg-day multiplied by body weight of
0.442 kg divided by the BAF of0.0956 then divided by the ingestion rate of0.15
kg/day. The answer is 0.2 mg/kg RGO for mercury with the NOAEL and
conservative scenario. Likewise, tlie RGO for mercury with the LOAEL and
conservative scenario is 2.0 mg/kg. The RGOs for mercury and the alternative
scenarios are O. 62 and 6. 2 mg/kg.
The RGOs for mercury and the green heron for the conservative scenario are higher .
than the corresponding values for the alternative scenario. The frog BAF used in
Appendix K is 0.04. There were three frogs collected from the wetlands having
concentrations of0.032, 0.026 and 0.024 mg/kg mercury. The frogs were·collected
near stations FLWS-0 I, FLWS-05 and FL WS-03. Mercury concentrations in wetland
soils at these locations were 0.362, 0.089, and 0.714 mg/kg. The BAF for frogs is
calculated as the average tissue concentration divided by the average wetland soil
concentration because no significant regression was observed (Table 4-16) The BAF
by the quotient of averages is 0.0704, which accounts for the difference (Table 8-20).
11. Table 8-21, Ecological Remedial Goal Options and Background Considerations,
Page 8-68. The footnote for dioxin states that it is dioxin TEQ calculated by the
USE PA (I 989) method, but the value of 0.54 for the alternative scenario (goose) is
for the WHO avian method. The cover soil observations also range higher for the
WHO avian method than the values shown on Table 8-21.
12. Table 8-21, Ecological Remedial Goal Options and Background Considerations,
Page 8-68. The RGO ranges are a conglomerate of the food chains for several
different assessment endpoints. The assessment endpoints vary widely in their degree
of exposure and sensitivity. For example, the goose had a hazard quotient greater than
I. 0 for only the conservative NOAEL scenario. Consequently, its RGO range is
generally greater than observed concentration ranges at the site. The RGO range of
the less-sensitive goose engulfs the ranges for the other assessment endpoints, masking
the finer points of the assessment's conclusions. The comparison of the overall RGO
ranges across assessment endpoints with background is not valid because it does not
protect all assessment endpoints. (See Page 8-31, lines I & 2.) The figures in
Appendix K do a better job at presenting this comparison.
13. Section 10.0, References. References for the papers Bundy el al. ( 1996) and Van der
Putte el al. (I 980) are not provided in Section I 0.0. These two appear on Page 8-27. ·
The paper Forbes and Carlow ( 1999) (Page 8-28) does not appear in reference
CDM • Federal Programs Corporation
A Subsidiary of Camp Dresser & McKee Inc. ~ IE ll: IU 11 ll:\ ~ consulting
engineering
construction
operations
825 Diligence Drive
Suite 205
Newport News, VA 23606
Tel: [phone] Fax: [phone] , Q J~l 3 1 J~ ~
July 30, 2001
Ms. Beth Brown-Walden
Remedial Project Manager
U.S. Environmental Protection Agency
Atlanta Federal Center
61 Forsyth Street, S.W.
Atlanta, Georgia 30303-3104
s
,1
'. I :-·,SUPERFUND S:[CTI
. 1 ~ •, 1 Pr
. --
PROJECT: EPA Contract No: 68-W5-0022
Work Assignment-030-RICO-041B
DOCUMENT NO: 3280-030-RI-RIRT -11239
SUBJECT: Draft Remedial Investigation Report, Lower Roanoke River
Martin, Washington and Bertie Counties, North Carolina
Dear Ms. Brown-Walden:
CDM Federal Programs Corporation (CDM Federal) is pleased to submit three copies of
the Draft Remedial Investigation report for the Lower Roanoke River Study. Copies of
the report are being sent under separate cover to members of ET AG, Dr. Russ Plumb,
Dr. Stephen Scott, Ms. Kim Miller and Ms. Jennifer Wendel. If you have any questions
concerning the attached, please call me at [phone], ext. 225.
Sincerely yours,
CDM FEDERAL PROGRAMS CORPORATION
Lynne J. France, P.G.
Project Manager
Attachment
cc: Lynn Wellman, EPA, Region IV
Sharon Thorns, EPA, Region IV
Bobby Lewis, EPA, SESD
Tom Augsperger, US FWS
Tom Dillon, NOAA
Nile Testerman, State of North Carolina
Document Control
Jennifer Wendel, EPA Region IV
Dr. Stephen Scott, USACE, WES
Dr. Russell Plumb, Lockheed Martin
Kim Miller, USGS
Gary Clemons, CDM Federal Region IV Program Manger
)N
Rll(I
June 28, 2001
Integrate.
Environmental
Solutions
Ms. Jennifer Wendel
Remedial Project Manager
United States Environmental Protection Agency, Region lV
61 Forsyth Street, SW
Atlanta, GA 30303-3104
Subject: Final Baseline Ecological Risk Assessment Reports
Welch Creek Area
• 100 Verdae Blvd. 29607-3825
P.O. Box 16778 29606-6778
Greenville, SC
Telephone: [phone]
Fax, 864-281-0288
SUPERFUND SECTION
Weyerhaeuser Company, Martin County, North Carolina
Dear Ms. Wendel:
On behalf of Weyerhaeuser Company (Weyerhaeuser), RMT, lnc. (RMT), is submitting the enclosed Final
Baseline Ecological Risk Assessment (BERA) reports for the Welch Creek area. This document incorporates
USEPA review comments dated July 17, 2000, agreements that were reached in our September 19, 2000,
meeting, and additional data that was collected to support the BERA since the draft BERA was submitted to the
USEPA. This document is required by the Administrative Order by Consent (Docket No. 98-10-C) dated
March 24, 1998.
Two copies of the BERA report for the Welch Creek area are enclosed for your review and approval. One copy
of the document has been submitted directly to Mr. Nile Testerman at the North Carolina Department of
Environment and Natural Resources (NCDENR), to Mr. Tom Augspurger of the U.S. Fish and Wildlife Service,
and to Sharon Thoms ofUSEPA. Two copies of the final BERA have been directly submitted to Lynn France
of COM Federal.
The FinalBERA°R_eport submittal comprises bound replacement Volume l of2 (Text) and Volume 2 of2
(Appen_dices): ·
Please review and approve the enclosed reports. lfyou have any questions, please call.
Sincerely,
RMT, Inc.
¾.:J{opi._r. \j b. /{i)(l.,,( SQ I ';i-)
Kristopher D. Krause, P.E.
Senior Project Manager
~LflU &r/ftv;,~ {~n I1/ Huibregtse ' ;fc![
Principal-in-Charge cl-
-Attach.ments: Final Baseline Ecological Risk Assessment Report Welch Creek Area (Volumes I and 2)
cc: Mr. Nile J'esterrnan, NC DEHNR
Mr. Tom Augspurger, US Fish and Wildlife Service
C:\ DAT A\ HYDRO\5100\ WORO\ECORISK\ ECO6&7 _CO\l'INAL BERA\ L000S I00·B-001.DOC
•
Ms. Jennifer Wendel
United States Environmental Protection Agency, Region IV
June 28, 2001
Page 2
Ms. Lynn France, COM Federal
Ms. Sharon Thoms, USEPA
Mr. Rodney Proctor, Weyerhaeuser Company
Mr. Steve Woock, Weyerhaeuser Company
Mr. Jeff Stamps, Weyerhaeuser Company
Central Files (2)
•
G:\ DAT A\ HYDRO\S 100\ WORD\ECORISK\ ECO6&7 _CO\FINAL BERA\ LO00SI0D-B-001.O0C
,...1. . -,
825 Diligence Drive, Suite 205
Newport News, Virginia 23606
tel: [phone]
fax: [phone]
June 27, 2001
.
•
Ms. Jennifer Wendel
Remedial Project Manager
U.S. Environmental Protection Agency
Atlanta Federal Center
61 Forsyth Street, S. W.
Atlanta, Georgia 30303-3104
PROJECT:
DOCUMENT NO:
EPA Contract No: 68-WS-0022
Work Assignment-930-RICO-041B
3280-930-RI-RJRT-14764
•
SUBJECT: Final Remedial Investigation Report, Lower Roanoke River
Martin, Washington and Bertie Counties, North Carolina
Dear Ms. Wendel:
COM Federal Programs Corporation (CDM) is pleased to submit four copies of tl1e Draft
Remedial [nvestigation (RI) report for tlie Lower Roanoke River Study. Copies of the report
are being sent under separate cover to members of ET AG, Dr. Russ Plumb, and Dr. Stephen
Scott. The enclosed documents and covers should be placed in tlie Draft RI report binders as
follows:
1) The contents of Volume 1 (text) should be replaced in its entirety.
2) Appendix G, Identification of Tentatively Identified Compounds, should be
added at the end of Volume 2.
3) Appendix B, Table 10-B, Page 2 of 2 should be replaced
4) Covers and Spines for both Volume 1 and Volume 2 binders should be
replaced.
Revisions incorporated in this Final RI report include:
• Edits in response to comments from EPA and ET AG on the Draft RI
• Summaries of additional related studies not available at the time that the Draft
RI was prepared
• Removal of the Human Health Risk Assessment
As we discussed, one of the review comments was not addressed: CDM was unable to obtain
data on the volume or concentration of dioxins/ furans of wastewater discharged during the
years of plant operation. Therefore, CDM could not calculate the mass of dioxin discharged
during that time. Also, one reviewers commented that tl1e data tables in Appendix A were
cut off. Unfortunately, the originals available to CDM are also cut off.
consulting• engineering. construction• operations
• • CDNI]
Since the draft report was submitted, several additional related studies have been completed.
These include additional dioxin fingerprinting studies performed by Dr. Plumb, the
Albemarle Sound depositional study conducted by Dr. Allen_ Teeter and additional modeling
analyses performed by Dr. Scott. The results of these investigations have been summarized in
the Final RI. ln addition, the Baseline Ecological Risk was finalized and the revisions have
been incorporated into the summary of the BERA that is found in Section 6 of the RI.
As requested, the Human Health Risk Assessment has been removed from the Final Rl
report. The risk assessment will be revised and re-submitted as a separate document when
the additional catfish analytical data become available and are incorporated into the
assessment.
If you have any questions concerning the attached, please call me at [phone], ext. 225.
Sincerely yours,
COM
Lynne J. France
Project Manager
Attachment
cc: Beth Brown-Walden, EPA Region 4
Sharon Thoms, EPA, Region 4
Bobby Lewis, EPA, SESD
Tom Augsperger, US FWS
Tom Dillon, NOAA
Nile Testerman, State of North Carolina
Dr. Stephen Scott, USACE, WES
Dr. Russell Plumb, Lockheed Marlin
Gary Clemons, COM Federal Region IV Program Manger
Document Control
March 20, 200 l
lntegra•J
Environ 11,c:r,tal
Solutio,l'°J~ ·
Ms. Jennifer Wendel
Remedial Project Manager
USEPA Region IV
6 I Forsyth Street, SW
Atlanta, GA 30303-3104
Subject: Weyerhaeuser Welch Creek Work Plan-Addendum 3.1
Dear Ms. Wendel:
(<_i"
744 Hearcland Trall 53717-1934
P.O. Box 8923 53708-8923
Madison, WI
Telephone: [phone]
Fax, 608-831-3334
\6)
1
I< ii: IU '11 I<•~
l\fu MAR 2 7 2001 \\1JJ
SUPERfUND SEC1l0N
Attached is the revised Welch Creek Work Plan Addendum 3.1 for the additional sampling activities that we ' agreed to implement during our September 19 and 20, 2000, meeting in Atlanta, Georgia. This Work Plan
Addendum includes the approach to the hydrologic evaluation that will be performed on Welch Creek. It has
also been modified to include the changes discussed in our conference call of March 13, 2001. In addition to
these changes, we will also be continuing our discussions and infom1ation exchange with the U.S. Army Corps
of Engineers' project manager Steve Scott and CDM-Federal's Del Baird on the boundary conditions for the
hydrology calculations and modeling, the sources of information we will be accessing fo~ our literature review
of sediment and soli_ds shear strength, and any additional local stream systems that we will be using as reference
streams. The work that is included in this Work Plan Addendum will be performed concurrently with the
evaluation of the data that was recently collected while implementing Welch Creek Work Plan Addendum 3.0.
The results of these evaluations will be incorporated into the revised draft Remedial Investigation (RI) and
Baseline Ecological Risk Assessment (BERA) reports, which will be submitted to the USEPA no later than
60 days after completion of the data validation.
Please review and sign the signature line on this letter if you approve this addendum. If you have any questions,
please contact me, at 608-662-5178.
Sincerely,
Rlv!T nc.
ristopher D. Krause .
Senior Project Manager
Attachment
cc: Niles Testerman -NCDENR
Approved By
Jennifer Wendel
Remedial Project Manager
Steve Scott-U.S. Army Corps of Engineers
Del Baird, Lynn France -CDM Federal
Rodney Proctor, Jeff Stamps, Steve Woock -Weyerhaeuser Company
Kathy 1-iuibrcgtse -RMT, Inc.
Date
1:1 WP MSN\I' JT\00-051 00\44\L0005 l 0044-00 1. DOC
• •
\V elch Creek Remedial Investigation/Feasibility Study (RI/FS)
Work Plan Addendum 3.1 -Hydrologic Evaluation
\Veyerhaeuser Facility, Martin County, North Carolina
Overview
The United States Environmental Protection Agency (USEPA)-approved remedial investigation activities
for the Welch Creek area were completed in 1999. However, after the USEPA's technical review of the
draft Welch Creek Remedial Investigation (RI) Report and a subsequent meeting to discuss the USEPA's
comments, three areas were identified that require additional hydrologic evaluation: (I) the potential for
Welch Creek sediment mobilization under possible future precipitation-driven flow events, (2) the
frequency of wind tide and storm surge events, and (3) the mass flux of dioxin TEQ to the Roanoke River
using the average annual flow as the flow rate that would occur in the creek during periods between
events.
This Work Plan Addendum identifies the objective of each task and the evaluation methods that will be
used to obtain the required information. This supplemental data will be intee,'fated into the final Welch
Creek RI and Baseline Ecological Risk Assessment (BERA) Reports.
Additional Hydrologic Evaluation
Task l: Evaluate the Potential for Welch Creek Sediment Transport Under Possible Future
Precipitation Events
Background and Objective:
During their review of the draft Welch Creek Rl, the USEPA noted that the whole-water
sampling focused on wind tide and storm surge events and did not include precipitation-driven
flow events. The completed sampling and analyses followed the approved work plan and were
based on local experience and the professional judgment that wind and storm events comprise
the most frequently significant high-velocity flow situations. However, to reduce uncertainty
about the effects of Welch Creek hydrology, the USEPA reviewers requested additional
analysis of the potential for sediment transport in response to future precipitation-driven flow
events.
Technical Approach:
The first step in evaluating the potential effect of precipitation-driven events on sediment
remobilization within the creek is to estimate th_e magnitude and frequency of Welch Creek
stream flow events. Flow in lower Welch Creek cannot be estimated by stage-discharge
techniques due to low velocities and tidal influences; thus, historical flow records are not
I:\ WP MSN'\P JT\00-051OO\H\2000510044.002. DOC 03/2010 I
• •
available. Data from local streams that are gauged will be used to estimate the storm flows
associated with the 2-ycar, 5-year, 10-year, 25-year, SO-year, and 100-year flood events. The
Welch Creek flows from these events will be estimated by proportioning the flows from the
gauged creeks based on the relative drainage basin area.
The local streams that are being considered for the analysis include Ahoskie Creek, Conetoe
Creek, and Van Swamp Creek, as summarized in Table I. These streams are selected since they
are all located within the Albemarle-Pamlico drainage basin and have similar physiographic
features to Welch Creek. Ahoskie Creek is located to the northwest of Welch Creek, within the
Lower Chowan River watershed; whereas, Conetoe Creek is located to the west, within the
Lower Tar River watershed. Van Swamp Creek is located immediately to the east of Welch
Creek and is within the Lower Roanoke River watershed. These stream gauging stations are
also being considered since they are all still active and have been operational for at least 20
years. Other gauging stations within the vicinity of Welch Creek are either inactive or arc of
relatively short duration.
Table l
Summary of USGS Gauging Stations within the Proximity of Welch Creek
Ahoskie Creek Ahoskie Hertford Chowan 02053500 63 mi2
Conetoe Creek Bethel Pitt Tar 02083800 78 mi2
Van Swamp Hoke Washington Roanoke 02084557 24 mi'
Creek
Welch Creek Plymouth Washington Roanoke Not gauged 28 mi2
The second step in evaluating the effect of precipitation-driven flow events is to estimate the
velocity and shear stress in the Welch Creek channel associated with each flood event. A tiered
approach will be used to evaluate potential remobilization of surficial sediment. A screening-
level analysis of the 100-year event will be done at each of the master transect cross sections.
The creek velocity at each location will be estimated through standard analytical techniques,
which will take into account the general rise in creek stage associated with the precipitation-
driven event. The flow area at each cross section will be estimated assuming that the Roanoke
River will also be flooded to a similar extent to Welch Creek. The shear stress applied to the
surficial sediment at peak flow for the event will be calculated from the average channel
velocity. These velocity estimates will be developed by applying standard engineering
principles and calculation methods. If locations are identified for which sediment may
potentially be remobilized during peak storm flows, a one-dimensional hydrodynamic model
will be used to better evaluate peak velocities in the creek during precipitation-driven flow
events.
2 J. \ WP MSNIP JT\00-05100144\20005 ! 0044-001. DOC 03120/0 I
\.:
• •
The proposed model to be applied to Welch Creek, if calculations indicate a potential for
sediment remobilization, is the one-dimensional hydrodynamic model (DWOPER) developed
by the National Weather Service (NWS) of the National Oceanic and Atmospheric Agency
(NOAA) (Fread, 1987). The model solves the complete one-dimensional St. Venant equations
of unsteady now using an implicit finite difference solution allowing the model to simulate
complex hydraulic features such as backwater and tidal effects. Boundary conditions for
modeled precipitation-driven events will be based on measured water elevation data for the
Roanoke River and estimated stream now for Welch Creek. Water elevation is measured at
Weyerhaeuser's monitoring pier within the Roanoke River near its connuence with Welch
Creek. The available data accurately characterize the changes in water elevation attributed to
noods, tides, and stom1 surge.
Finally, a range of shear strengths for the Welch Creek sediment will be developed using shear
strength data from Welch Creek (samples collected and analyzed by the USACOE) and recent
publications concerning the shear strength and erodibility of cohesive sediment deposits. Many
of these theoretical equations correlate physical index parameters, such as bulk density, with the
shear strength of the sediment deposits. Therefore, the physical characterization of the
wastewater solids performed as part of the 1995 investigation will serve to characterize the
Welch Creek sediment. The shear strength of the Welch Creek sediment will also be estimated
using published data from similar deposits (i.e., data provided by the COE and other sources),
as available. The estimated range of sediment shear strength values will be compared with the
shear stress values that will be calculated for each flood event at the various transect locations to
assess the potential for sediment mobilization.
If the calculated velocity produces sheer stresses that are less than the estimated sheer strength
of the sediment materials, then it will be concluded that precipitation events do not mobilize this
material and further evaluation of these events will not be performed.
However, if the calculated velocity, based on the one-dimensional modeling, produces shear
stresses at a location that exceed the shear strength of the sediment, an estimate of the duration
of the critical stream velocity will be determined for that location. Actual export of remobilized
sediment will not be determined in the proposed analysis and would require further
characterization of surficial sediment in the creek, and sediment fate and transport modeling.
Further, the proposed analysis does not distinguish between deposited wastewater solids and
native material that may have been deposited in the creek in recent years.
Task 2: Analyze the Frequency of Wind Tide and Storm Surge Events
Background and Objective:
During their review of the draft Welch Creek RI, the USEPA noted that the whole-water
sampling, and therefore the sediment transport evaluation, focused on wind tide and storm surge
3 I:\ WPMSN\P 11\00-05 I 00144\ZOO0S 10044-002. DOC 0J/20/0 !
• •
events. The US EPA reviewers commented that an additional analysis of the frequency and
duration of wind tide and stom1 surge events was necessary to put into perspective the potential
for sediment mobilization due to these events.
Technical Approach:
Historical stage data from the Roanoke River and available hurricane information from the
NOAA will be used to evaluate the magnitude, duration, and frequency of wind tide/stonn surge
events. These events will be summarized according to the magnitude and frequency of the
events over the available period of record. The 1999 whole-water sampling results obtained
during three wind tide/storm surge events will then be put in context with regard to the
magnitude, duration, and frequency of the events and the potential for sediment mobilization
clue to these type of events.
Task 3: Calcnlatc the Mass Flux of Dioxin TEQ to the Roanoke River Using the Average Annual
Welch Creek Flow Rate
Background and Objective:
During their review of the draft Welch Creek RI, the USEPA noted that the mass flux of dioxin
TEQ was calculated using the baseflow rate of IO cfs rather than the average annual flow rate.
The average annual flow rate is estimated as approximately 28 cfs, which includes both
baseflow and precipitation runoff. The USEPA reviewers commented that the mass flux of
dioxin TEQ should be calculated using the average annual Welch Creek flow rate as the
baseline flow condition.
Technical Approach:
The mass flux of dioxin TEQ from Welch Creek will be calculated using the average annual
flow as the baseline flow condition. The average annual flow will be multiplied by the whole
water "baseflow" concentration and the number of non-event days in a year. The flux from the
whole-water sampling events (i.e., Hurricane Dennis, northeaster, and wind surge) will then be
added to the average annual flux. This additional calculation will be presented in the final RI
Report.
Reference
Frcad, D.L. 1987. National Weather Service Operational Dynamic Wave Model. Hydrologic Research
Laboratory, National Weather Service, NOAA. April 1987.
4 1:IWPMSN\PJT\00.05 I00\4,I\Z0005 !0044•002. l)OC 03/2010 I
• • UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
March 5, 2001
Rodney Proctor
CHI L28
Director, Environmental Affairs
Weyerhaeuser Company
PO Box 9777
Federal Way, WA 98063-9777
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960
Re: Review of the Draft Remedial Investigation Report (RJ) and the Draft Baseline Ecological
Risk Assessment (BERA) documents, Landfill I Area, Weyerhaeuser Martin County Facility
Dear Mr. Proctor:
The United States Environmental Protection Agency (EPA) has completed it's review of ·
the above referenced documents. EPA comments on the Draft R1 report are included as
Attachment I to this letter, and comments on the BERA are included as Attachment 2.
To avoid duplication, comments on the Baseline Ecological Risk Assessment are included
as the separate Attachment 2, and are not repeated for the summary of the BERA included in the
RI Report. However, Section 9 of the RI Report, which summarizes the BERA, should be
modified to appropriately reflect the comments made on the BERA.
Comments are not provided on the Executive Summaries or the Conclusions/
Recommendations (Section 9 of the R1 and of the BERA) portions of the documents. The EPA
expects that these sections of both documents will be revised to reflect the enclosed comments
and agreements made on the revisions to each.
A written response to EPA comments and a follow-up technical meeting may be necessary
to resolve issues identified in the comments. In any case, in accordance with the schedule
established in the Administrative Order by Consent, please submit a revise R1 report which
incorporates the attached comments within 45 days of the receipt of this letter.
Internet Address (UAL)• http://www.epa.gov
Rocycled/Recyclabto • Printed with Vegetable Oil Based Inks on Recycled Paper (Minimum 30% Postconsumer)
• •
If you have any questions, please feel free to call me at [phone].
cc: Jeff Stamps, Weyerhaeuser
(Nile Testerman, NCDENR
Tom Augspurger, USFWS
Lynn France, COM Federal
Kathy Huibregtse, RMT
• •
ATTACHMENT 1
EPA COMMENTS ON THE DRAFT RI REPORT
LANDFILL 1 AREA, WEYERHAEUSER COMPANY SITE
MARTIN COUNTY, NORTH CAROLINA
General Comments
1. The Primary objective of the RI for the Landfill 1 Source Area was to determine the
nature and extent of impacts [from the Landfill] to the degree necessary to assess the level
of risk presented by the site and to evaluate the appropriate types of remedial response
actions. This was accomplished by two Phases of field work and sampling. Fallowing the
first phase (Phase 1), a list of Preliminary Contaminants of Concern (PCOCs) was
developed for the pathways of concern at the Site.
Following review of the Phase 1 data, EPA discussed with Weyerhaeuser and their
representatives the possibility of streamlining data collection needs during Phase 2. In
alignment with the EPA guidance Conducting Remdia/ Investigations and Feasibility
Studies/or CERCLA Municipal Landfill Sites (OSWER Directive 9355.3-11, February
1991) an agreement to limit further sample collection to establish the full extent of
contamination associated with the wastewater treatment solids on the surface of the
Landfill was reached. This guidance allows EPA and responsible parties to focus RI/FS .
tasks on just the data required to evaluate alternatives that are most practical for municipal
landfill sites.
Further, EPA has established capping (containment) as the presumptive remedy for
municipal landfill sites. EPA and Weyerhaeuser have agreed that some containment
remedy which would limit the direct contactto contaminants in surface soils (and
wastewater treatment solids) which are on the surface of the landfill would be
implemented at the site. Therefore, Phase 2 sampling which was to have included surface
soil sampling an appropriate number of samples from a 60-ft grid across the landfill was
not conducted. Please provide a description of the Phase 2 sampling agreements and
presumptive remedy discussions. In the absence of a landfill cover which will eliminate
exposure to the surface soils (and wastewater treatment solids) on the landfill, a full
delineation of the nature and extent of surface soil contamination would have to be
conducted.
2. Even though shallow groundwater is not used currently as a potable source, the future
residential use of the groundwater should be evaluated in the Risk Assessment. This
approach is consistent with Region IV risk assessment guidance which states: "If the
groundwater is considered to be potable, the future consumption of groundwater for
residential purposes should be evaluated. Ingestion and inhalation of chemicals volatilized
from groundwater should be considered." Please modify the Risk Assessment portion of
the RI accordingly.
• •
3. When evaluating the concentrations of dioxin in environmental media and biota the non-
detected congeners were treated as zero concentration instead of as half the detection
limit. This is inconsistent with EPA's policy for treating non-detects described in the
Guidance for Data Useability in Risk Assessment (Part A) (USEPA 1992). The dioxin
TEQs should-be recalculated with treatment of non-detects as a surrogate concentration of
one-half the detection limit. This same comment was made on the Welch Creek Draft RI
and BERA documents.
4. NC GW 2L for potable water
Specific Comments
1. Pg i, Executive Summary; Section 7.3.3, pg 7-11. In discussing the dioxin TEQ
concentration and comparing it with the EPA industrial target soil level, the text should
also state that the residential target soil,level for dioxin TEQ (1 ppb) is exceeded.
2. Pg i, Executive Summary, elsewhere in the report. The term "North Carolina Maximum
Acceptable Concentrations (NC MACs)" should be explained (to what do they apply? Are
these values promulgated?) and referenced.
3. Section 2.2, page 2-2; Please define where the waste water solids originated from and why
they are of a concern to the sites.
4. Section 2.4,2 page 2-5, first sentence. This should be one mile range in this sentence.
5. Section 2.4.2 ,page 2-5 third paragraph; Please change the statements in this paragraph to
indicate that the private wells are "not downgradient" from Landfill 1.
6. Section 2.4.2 ,page 2-5 fourth paragraph; Please note in the text that the four public water
supply wells are downgradient of the site.
7. Section 3.4, p. 3-4. This section states that deep monitoring wells were installed at two
downgradient locations. Please include the rationale for not installing a third, upgradient,
deep monitoring well.
8. Section 4.1, p. 4-1. The second paragraph describes surface water drainage features that
were constructed on the south side of the landfill. Please indicate these features on a site
map, so that the location can be compared to the location of wetland soil samples
collected south of the landfill.
9. Section 4.2.2, p. 4-4, first paragraph. Please include a description of the actual observed
thickness of the confining unit. It is somewhat misleading to refer to the clay as a
"confining unit" throughout the paragraph, only to state in the last sentence that it is a
"relative aquitard" with a hydraulic conductivity of 5 .9x 1 O·• cm /s. It appears that the
• •
discussion mixes regional geologic information with site~specific information. As the
regional geology was discussed in Section 2.3, this section should discuss information
about the unit as it is found at the site.
10. Section 4 3, p. 4-5. This section should include the results of the hydraulic conductivity
tests described in Section 3.5 (p. 3-7). The wells that were tested and the results of the
tests should be listed in a table.
11. Section 4.3.1 page 4-6 first paragraph first sentence; Please state that the flow that is
being described is the shallow unconfined system.
12. Section 4.3.1 page 4-6; The effects of the landfill on the local flow paths should be
evaluated. The RI states that wells FL-01 and FL-02 are up gradient but no ground water
elevation data exists with in the fill material. Therefore it is unknown if landfill creates a
mounding effect which is likely if the material is very permeable. Further evaluation
should be discusses, and more support that FL-01 and FL-02 are upgradient should be .
given.
13. Section 4.4. 1, page 4-6; Please compare the level of the wetland water and the shallow
ground water and describe how they are connected with the highly permeable soil.
14. Table 4-1. The geologic unit associated with each sample should be listed in an additional
column on this table.
15. Table 4-2; Define NM. Also this is one of the many tables that does not have a page
number:
16. Section 5.1, top ofpg 5-2 -screening values. EPA Region 4 now uses the EPA Region·
9 Preliminary Remediation Goals (PRGs) for screening ofCOPCs. (EPA 2000) The
noncancer based values must still be adjusted to a HQ of0. l.
17. Section 6.1.1, Page 6-4. Although there are no ARARs for PCBs in cover soil, the EPA
Office of Solid Waste and Emergency Response (OSWER) Directive number 9355.4-01
(August 15, 1990) has issued guidance on Remedial Actions for Superfund Sites with
PCB contamination. This guidance established a Remediation Goal of 1.0 ppm (mg/Kg)
for sites with Residential use potential and 10.0 to 25.0 pmm for sites with industrial use ..
Please modify the second paragraph on page 6-4 accordingly.
18. Section 6.1.3, page 6-12, third paragraph; In the discussion on methyl mercury it is not
clear what is meant by literature values. Please clarify this text.
19. Section 7.1.2, p. 7-2. Please include residential ingestion exposure to groundwater as a
possible future use scenario.
20. Table F-4, bis(2-ethylhexyl) phthalate exceeds the state standard of3 µg!L and should be
considered a COC as well
• •
21. Section 7.4.1 pg 7-14, uncertainty of site data. The statement that the
"concentrations ... are biased high due to incorporation of environm_ental data qualified as
estimated" is suspect. Usually estimated values (J qualified) can be higher or lower. If
there is information t_o support this statement that the Landfill No. I site data are truly
biased high, it should be presented here. Otherwise the verbiage should be revised to
indicate that this uncertainty may result in either an under-or over-estimation of the risk.
22. Section 7.4.3, pg 7-15; Table 7-7, uncertainty of dioxin assessment. The discussion here
inappropriately implies that, in using the TCbD slope factor (CSF) in HEAST, EPA is
grossly overestimating the risk. The third sentence in the last paragraph on the page
(starting: "This CSF, published in HEAST. .. ") should be revised to read: "This CSF,
published in HEAST, is the current value used by EPA in the Superfund program. This
value may be changed (higher or lower) based on the EPA dioxin reassessment report
which is scheduled to be finalized soon." Table 7-7, showing alternate dioxin CSFs,
should be moved to Appendix K. The rnain body of the risk assessment, Section 7, should
only show the risks from the CSF (1.5E+5) EPA is currently using for site decisions.
23. Section 7.4.3, pg 7-16 -uncertainty assessment. The third sentence in the last paragraph
on pg 7-16 (" ... the exposure estimates are likely to be greater than the maximum
exposures that can be reasonably expected to occur.") is NOT consistent with EPA risk
assessment guidance regarding the RME. This sentence must be deleted.
24. Section 7; App. L. The chemical risk tables (now in Appendix L) are a vital part of the
risk assessment and thus, should be moved to Section 7 of the report.
25. Tables 7-2, L-2A, L-2B -groundskeeper scenario. The soil ingestion rate of 50 mg/d
(used for the regular onsite worker who does not have intense contact with the soil) is not
appropriate for the groundskeeper receptor. For this receptor, an incidental soil ingestion
rate of 480 mg/d should be assumed. (EPA 2000, 1991) For the same reasons, the skin
surface area to come in contact with soil should be higher for the groundskeeper receptor
than for the regular onsite worker.
26. Tables 7-2, L-6A, L-7 A -Adult trespasser. The incidental soil ingestion rate for the adult
trespasser should be I 00 mg/d. (EPA 2000, 1991) This value applies to sediment as well.
27. Table 7-3a -oral toxicity values. For manganese, the dietary intake of Mn must be·
subtracted from the IRIS RID. A value of0 02 mg/kg/d should be used for Mn in soil.
For chromium, speciation data (showing the level of total Cr versus hexavalent Cr) must
be presented and discussed. Otherwise, the RID for hexavalent Cr should be used.
28. Table 7-4a -inhalation toxicity values. EPA has a provisional inhalation slope factor of
3.1 kg-d/mg for Benzo[a]pyrene. (EPA-PROV)
29. Section 7; App. L. The chemical risk tables (now in Appendix L) are a vital part of the
risk assessment and thus, should be moved to Section 7 of the report.
• •
30. Section 8.4, Direct Ecological Effects Characterization, Page 8-8. The report states that
the maximum observed concentrations of barium and manganese were higher in the
wetlands than in the landfill cover materials and therefore the wetland concentrations are
not attributable to the landfill. Concentrations of barium and manganese are elevated in
. wetland soils with respect to Conaby Creek. The document fails to present an alternate
theory for the source of barium and manganese in wetland soils. It is possible that barium
and manganese can desorb from cover materials, wash into the wetlands, and bind to
wetlands soils. Wetland soils have a higher organic content and presumably a higher
cation exchange capacity than cover soils. Wetland soils may capture and retain metals
draining off the wetland. Text stating that barium and manganese in wetland soils are not
site-related should be removed or clarified.
31. Section 8.4, Direct Ecological Effects Characterization, Page 8-8. Exchangeable barium
as associated with cation exchange sites on clay minerals and organic matter does not
behave the same in the. environment as covalently-bonded barium in minerals.
Concentrations of barium less than Eastern U.S. regional background cannot negate a
finding of potential risk in a site-specific biological study. Toxicity potentially attributable
to barium in a toxicity test indicates that barium might be bioavailable in wetland soils. If
barium were present in the form of naturally occurring minerals, instead of on cation
exchange sites, it would have been detected at similar levels in the site-specific
background sediment
32. Section 8.0. Please include the Tables of the Summary HQs for each receptor endpoint
from the Draft BERA in this section of the RI.
• •
References
EPA 2000. Supplemental Guidance to RAGS: Region 4 Bulletins, Human Health Risk
Assessment Bulletins. EPA Region 4, Website version updated May 30, 2000:
http://www.epa.gov/region4/waste/oftecser/healtbul.htm
EPA 1991. Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation
Manual, Supplemental Guidance, "Standard Default Exposure Factors", Interim Final, OSWER
Directive 9285.6-03, March 25, 1991.
EPA ( 1989). Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation
Manual, Part A. Interim Final, EPA OERR, December 1989.
IRIS, 2001. Integrated Risk and Information System, National Center for Environmental
Assessment, Office of Research & Development. (website [www.epa.gov/iris], updates added
periodically).
HEAST, 1997. Health Effects Assessment Summary Tables, FY 1997 Update, Office of Solid
Waste and Emergency Response, USEPA, July 1997.
NCP 1990. National Oil and Hazardous Substance Pollution Contingency Plan, Final Rule, 40
Code of Federal Regulations Part 300, March 8, 1990.
EPA-PROV. EPA provisional toxicity values support document available on request from Office
of Technical Services, EPA Region 4. ·
• •
ATTACHMENT 2
EPA COMMENTS ON THE DRAFT BASELINE
ECOLOGICAL RISK ASSESSMENT REPORT
LANDFILL 1 AREA
WEYERHAEUSER COMPANY SITE, MARTIN COUNTY, NORTH CAROLINA
General Comments
I. The Draft Hazardous Waste Identification Rule (HaWIR) model was released for public
comment last November. There is no HaWIR rule, instead EPA Office of Solid Waste is
working on a model which provides a risk-based framework for reviewing wastes for
Subtitle C of RCRA. The Congressional Budget for FY0 I contained a rider specifying
that the Ha WIR model cannot be used for regulatory decision making until it has been
reviewed by the Science Advisory Board or the National Academy of Science.
The statement in the RI and BERA that the MA TC represents "de mini mus" threshold is
taken out of context. The HaWIR model is developing a set of exposure scenarios and
NOAEL and LOAEL values for sensitive reproductive effects. The model does not mean
to imply that any time you take a NOAEL and a LOAEL and create a MA TC that it
represents de mini mus threshold, but only within the context of the conservative scenarios
and values that are being developed for the Ha WIR model. The term de mini mus has a
specific meaning in the RCRA context having to do with Land Disposal Restrictions
(LDRs).
EPA has not adopted the Ha WIR model to decision making at existing landfills or at
Superfund sites. The Ha WIR model is being developed for a national-scale assessment
and was not intended to be applied at the site level. At the national level, EPA had to ·
come up with some number between the NOAEL and LOAEL to apply as a generic
criterion. The choice of the MA TC is somewhat arbitrary from a toxicological
perspective. For remedial decision making at Superfund sites, remedial goal option ranges
are developed for the LOAEL to NOAEL range.
The MA TC should be removed from the BERA and the RI report as a toxicological
benchmark since it is misleading and does not necessarily represent a risk_ management
decision tool.
2. Background: Chemicals for which the ERA predicts a potential risk using site-specific
biological data, cannot be eliminated based on Eastern U.S regional background. The
unconsolidated waste material forming the landfill cover might have higher bioavailability
than metals in natural soils, which was the purpose of taking site-specific body burden
measurements. The behavior of wastewater solid metals with respect to biological
receptors can vary from that of mineral soils. The background soil data can be used for
comparison to on-site data only for Landfill I, but should not be used to eliminate a
COPC.
• •
3. Toxicity Testing: Barium and manganese are not the only potential explanation for the
observed toxicity in FLWS-05 and -06. Apart from the possibility of confounding effects
of water conductivity changes during the test (which might be addressed by repeating the
test), the toxicity results can be interpreted as caused by chemicals other than barium and
manganese. For example, concentrations of copper, chromium, barium, dioxin TEQ,
manganese, mercury, vanadium, and zinc are higher at station FLWS-06 than at FL WS-
03. One or more of any of these constituents might be the source of observed toxicity at
FLWS-06. The reports should be revised to remove the implication that only barium and
manganese are the potential toxicants.
The magnitude of the effect at FL WS-05 versus the effect at FL WS-06 should not be
over-interpreted. The difference between the mean dry-weight of the amphipods at the.
end of the test at Station FLWS-05 (0.176 ± 0.042) and Station FLWS-06 (0.207 ±
0.029) is insignificant Results should not be interpreted to mean that the concentrations
of toxicants at Station FL WS-05 must be the highest.
Please create a table summarizing direct toxicity results. Include No Observed Effect
Concentration (NOEC) to Lowest Observed Effect Concentration (LOEC) ranges for
each COPC. Include the direct toxicity NOEC and LOECs on a summary table with the
food-chain preliminary RGOs in Chapters 8.0 of the ERA and RI.
4. Please explain whether the BERA exposure models address the possibility of the red-tailed
hawk (under the Upland Portion of the Landfill 1 Area) and the barn owl and red fox
(under the Wetland Portion of the Landfill 1 Area) consuming shrews such as the one
sampled and discussed on Page 4-15. This would seem important as the shrew that was
sampled had levels of dioxin 10 times and mercury 8-10 times that of the other small
mammals samples. A discussion of the effect on the risk calculations for the above
receptors should be included in the BERA.
5. An appendix similar to Appendix F should be included for the ecological COPC screening
for Landfill 1. All detected analytes should be included on the table, even those for which
no screening value is available.
6. Include an appendix with data summary tables for all analytes showing frequency of
detection, summary statistics, location of maximum, and range of detection limits for non-
detects. Also include a sample by sample summary of the data showing the concentrations
of all analytes detected or for non-detects the detection limit. Include the data validation
flags and the Tentatively Identified Chemicals (T!Cs).
• •
Specific Comments
I. Executive Summary, Please add the following language to the uncertainties discussion
here, and to Section 8 of the RI (in corresponding places):
A Page iii, after first sentence:
"However, since a model species is chosen within a food chain group, or receptor
endpoint, risk calculations are set up to represent a group of species at a higher level of
biological organization, sharing a common diet".
B. Page iii, after last sentence in first paragraph:
"However, some conservatism is still appropriate in the risk assessment in order to protect
local populations and communities of biota. Because the dose-response curve and the
characteristics of the populations are often unknown, some degree of conservatism is
appropriate.
C. Page iii, after last sentence in second paragraph: ·
"Application of probabilistic risk assessment (PRA) will not necessarily change the
outcome of a risk assessment to result in a lower estimate of risk. In both the point
estimate(deterministic) and the PRA, the risk assessment will evaluate realistic exposure to
a differentially exposed !axon, generally resulting in similar estimates of risk between the
two methods. The difference between the two methods is that PRA generates probability
distributions to characterize variability or uncertainty in the risk estimates, while point
estimates of multiple scenarios produce at best a semi-quantitative analysis of
variability/uncertainty. For risk assessments like Landfill I, where PRA is not used, the
uncertainty around the risk estimate was evaluated semi-quantitatively through risk
estimates based on both the conservative and alternative exposure assumptions. In fact,
for the Landfill I assessment, it is important to note that, although the conservative and
alternative scenarios were based on different strategies, the results of the two scenarios
were virtually indistinguishable from a risk management perspective. For most of the
food-chain model assessment endpoints in the Landfill I BERA, there was little difference
between the conservative and the alternative scenario results. Typically, remedial
decisions will be based on conservative exposure estimates (Section 6.1.2 of USE PA,
1989a). In the case of ecological risk assessment, conservative exposure is not exposure
to a high-end member of a population of a receptor species, as is reasonable maximum
exposure in human health risk assessment. Conservative exposure in the ecological
context looks at realistic exposure to a differentially exposed species within the group of
species represented by the assessment endpoint".
2. Section 4.1, Environmental Media Results, Page 4-1, third bullet. It is a misnomer to call
the food-chain COPCs the refined COPCs. The final set ofCOPCs is the union of the
direct-toxicity COPCs and the food-chain COPCs. The risk assessment will address the
entire "preliminary" set of CO PCs. As stated in EPA Region 4's Supplemental Guidance,
the risk assessment is to address both direct toxicity and indirect toxicity through the food '
• •
chain.The constituents which exceeded the screening values for sediments are COPCs for
the freshwater benthic community assessment endpoint. A contaminant that is a potential
direct toxicant cannot be addressed through a food chain analysis. All constituents
exceeding screening values are potential direct toxicants. Therefore, none can be
"refined" by food chain analysis. Please clarify the text of this section.
3. Section 5.2, Exposure Modeling, Page 5-2. Please modify the text to indicate that the set
of intake assumptions for the food chain models in the alternative scenario are not
technically more "site-specific" than the conservative inputs required by EPA but are
based on average body mass.
4. Table 5. l, Range of Exposure Point Concentrations for selected constituents. There is a
Table 5-la for dioxins and a Table 5-1 b for metals, but no table appears for PCBs. PCBs
are included on Table 5-10 as a constituent for which daily exposures were estimated.
Please include tabulated exposure point concentrations for PCBs.
5. Table 5-11, Estimated Daily Exposures, Wetlands, Page 5-22. The estimated
conservative/maximum exposure doses for the American woodcock for metals were
between 2 to 50 percent lower than predicted from the exposure point concentrations in
Table 5-1 b. For example, the maximum concentration of arsenic in wetland soil is
reported as 62.9 mg/kg. The assumed incidental ingestion rate of soil was 0.01 I kg/day
for the woodcock. Multiplying the 62.9 mg/kg by the 0.011 kg/day and dividing by the
assumed body weight (0.1338 kg) yields 5.2 mg/kg-day. (Arsenic was not detected in
earthworm tissues.) Table 5-11 has 3.1 mg/kg-day for the conservative maximum
scenario for arsenic. Please check the math and correct any discrepancies.
6. Section 7.0, Direct Ecological Effects Characterization. As shown in Figure 6-3 of the RI
Report and Table 7-2, the relative magnitude of the chemical concentrations vary between
the two growth-reducing locations, FLWS-05 and FLWS-06. Except for some chemicals,
such as acetone and arsenic, concentrations of most chemicals are higher in the growth-
reducing stations than in the normal-growth stations. It is unnecessary for the same
chemical to be present in both growth-reducing stations. Toxicity could be contributed by
one or more of the other chemicals. Toxicity should not only be attributed to barium and
manganes_e in the ERA.
7. Table 7-2, Comparison of Constituent Concentrations in Direct Toxicity Samples, Page 7-
.4. Footnotes are missing on the table. Please include footnotes
8. Section 8.2.1, Insectivorous Mammal, Aluminum, Page 8-4. Aluminum concentrations in
wetland water at 32.5 mg/Lare very high (Handbook of Hydrology by David Maidment).
Even with just the exposure to surface water, the hazard quotient exceeds 1 for the short-
tailed shrew under the conservative scenario. The toxicity study on rats (Ondreicka et al.,
1966) administered aluminum chloride in drinking water; bioavailability is not the issue
here. The argument for eliminating aluminum as a COPC must also address elevated
concentrations in water.
• •
9. Section 8.2. l, Insectivorous Mammal, Aluminum, Page 8-4. The concentrations of
aluminum in the earthworms and mixed terrestrial invertebrates were very high. The
hazard quotients would be well over l for all scenarios even if the entire diet were
earthworms without any incidental ingestion of soil. Please discuss the high values in
tissue observed. Were the worms depurated before chemical analysis to clear soil in the
gut? Eastern U.S. background levels of aluminum do not explain the elevated aluminum
in earthworm tissues. Aluminum should remain a COC for the ecological risk assessment.
The statement on Page 8-5 that aluminum is not a site-related constituent is unproven.
Aluminum is commonly used in wastewater treatment processes. The solids covering the
landfill are a waste material not a soil. It is not appropriate to compare wastewater solids
concentrations to average concentration ranges in soil.
I 0. Section 8.2. I, Insectivorous Mammal, Chromium, Page 8-4. Please note in the text that
the hazard quotient for the conservative scenario would be 6.6 if the chromium were
assumed to be hexavalent chromium. Describe hexavalent chromium measurements. _The
argument that reducing conditions in sediments can convert hexavalent chromium may
apply to wetland soils but not to the upland soils.
11. Section 8.4.1, Uncertainty Analysis, Characterization of Affected Media, Page 8-20.
There were many analytes that were detected but data was rejected during the validation
process. The laboratory analysis was confounded by the presence of non-target analytes,
which elevated the detection limits. Certain pesticides and phenols might be present in
cover soils or wetland soils at levels greater than the risk screening values, but were
reported as non-detect due to analytical difficulties. Also, there were numerous non-target
analytes, which may have associated toxicity. It is possible that the site-specific toxicity
testing was influenced by presence of non-target analytes in sediment. The uncertainty
discussion should be expanded to explain how analytical challenges may have affected the
risk assessment results. Also, expand the discussion of the validity of qualified metals data
in cover soils and wetland waters.
12. Section 8.4.2, Uncertainty Analysis, Exposure Assessment, Page 8-21. Although the
potential risk estimated with the conservative scenario is a high-end estimate of risk, it
should not be described as an "upper bound" because none of the variables in the exposure
model are bounded. Also change terminology on Page 8-24, line 9, where "upper bound"
is used to describe risk estimates for the 95 percent upper confidence level on the mean.
13. Section 8.4.2, Uncertainty Analysis, Exposure Assessment, Food Ingestion Rates, Page 8-
22. Please expand the uncertainties discussion to describe the relative differences made in
the risk estimate by assuming alternative versus conservative ingestion rates for the
different assessment endpoints.
14. Section 8.6, Preliminary Remedial Goal Options, Page 8-28. The calculations of the
PRGs based on the exposure point concentration divided by the corresponding hazard
quotient will provide a rough estimate of the PRG. This method, referred to here as the
"ratio method," fixes the origin of the plot of concentration in the organism versus
concentration in the soil at zero, which can over or underestimate actual exposure
• •
depending on relationships observed (Appendix C) A more rigorous analysis is suggested
for this important result. The results from Appendix C for mixed terrestrial invertebrates,
earthworms, and plants more often fit a straight line than results for small mammals or
frogs. For wider-ranging animals (e.g., small mammals and frogs) where a linear
relationship was not observed, the ratio method is the only practical option. For
constituents demonstrating a linear relationship, substitute the concentration in the biota
with the concentration in the sediment ( or soil) multiplied by the bioaccumulation factor
(i.e., the slope of the line in Appendix C). Rearrange the equation to solve for the
concentration in sediment ( or soil) to achieve the target hazard quotient. Express the
results as a LOAEL to NOAEL range for both the conservative and alternative scenarios.
I 5. Section 8.6, Preliminary Remedial Goal Options, Page 8-28. No reference has been given
to support the claim that the MA TC represents "de mini mus" threshold for exposure. One
cannot make a general statement that a certain point between the NOAEL and the LOAEL
equates to de mini mus risk, because the degree of risk will depend on the study design, the
proportion of the study animals having a positive response at the LOAEL, and the severity
of the effect being investigated. Use of the MA TC does not reduce the uncertainty in the
threshold levels but only serves to obfuscate the uncertainty by expressing a range of
results as a single value. Please see general comment 1.
Reference for HaWIR: http://www.epa.gov/epaoswer/hazwaste/id/hwirwste.htm
16. Table 8-19, Range of Ecological RGOs for Upland Portion of the Landfill No. 1 Area, .
Page 8-64. While RGOs for dioxin TEQs appear to be correct, the RGOs for chromium
for the insectivorous mammal (Short-tailed shrew) are too high. For example, assuming a
chromium concentration in soil of 9;869 mg/kg for the LOAEL-based alternative scenario,
and the relationship between soil concentrations and tissue concentrations in Appendix C,
a hazard quotient of around 14 or 15, is produced, which is substantially higher than the
target hazard quotient of 1. Please check and correct the calculations for chromium
RGOs.
17. Section 9.2, pages 9-3 through 9-5. It appears that the Assessment Endpoint numbers
may be, in some cases, mistakenly labeled and out of order in this section. Please check
the numbers and order of the Assessment Endpoints in this section.
18. Section 9.2. Please elaborate on or further explain the statement under each Assessment
Endpoint "Limited potential for unacceptable risk to the __ endpoints is indicted by the
deterministic point estimate of risk", in plain English, pleasel
19. Section 9.2.1. Please provide a recommendation as to the ultimate fate of the study of this
Assessment Endpoint, as included for the others.
• •
References
Ondreicka, R., E. Ginter, and J Kortus. 1966. Chronic toxicity of aluminum in rats and mice and
its effects on phosphorus metabolism. Brit . .!. Indus/. Med. 23:305-313.
OSWER Directive 9285. 7-28 P. Issuance of Final Guidance: Ecological Risk Assessment and
Risk Management Principles for Superfund Sites. Memo from Stephen D. Luftig to
Superfund National Policy Managers in the Regions. Dated October 7, 1999.
USEPA 1989a. Risk Assessment Guidance for Superfund, Volume I Human Health Evaluation
Manual (Part A). Published by the U.S. Environmental Protection Agency, Office of
Emergency and Remedial Response, Washington, D.C. EPA/540/1-89/002.
NORTH CAROLINA
DEPARTMENT OF ENVIRO.T AND NATURAL RESOURCES
DIVISION OF WASTE MANAGEMENT ·
MICHAEL F. EASLEY, GOVERNOR
William G. Ross Jr., SECRETARY·
WILLIAM L. MEYER, DIRECTOR
Ms. Jennifer Wendel
28 February 2001
Superfund Branch, Waste M~agement Division
US EPA Region IV
61 Forsyth Street, S. W.
Atlanta, Georgia 30303
SUBJECT: Review of Draft Remedial Investigation and Ecological Risk
Assessment Reports
Landfill No. 1
Weyerhaeuser Company
Martin County
Dear Ms. Wendel:
The State of North Carolina has reviewed the Draft Remedial Investigation and
Ecological Risk Assessment Reports for the Landfill No. 1 area at th~ Weyerhaeuser
Company site. The reports are dated December 2000 and received by the Division
on 28 December 2000. The following comments are offered:
I . Please be aware that clean up . to restrictive use (industrial) will require .
institutional controls such as land use restrictions and deed recordation.
2. Please contact the North Carolina Division of Health and Human Services
(Mr. Ken Rudo, 919 715-6430) for any pM~eter in the ground water (e.g:,
dioxin TEQ) that has no North Carolina ground water standard (2L), interim
2L, recommended 2L, MCL, federal drinking water standard , or Region IX
tap water value.
3. Attached are comments from Ms. Hanna Assefa on the human and ecological
risk assessments.
1646 MAIL SERVICE CENTER, RALEIGH, NORTH CAROLINA 27699-1646
401 OBERLIN ROAD, SUITE 150, RALEIGH, NC 27605
PHONE: [phone] \ FAX: [phone]
AN EOUAL OPP0RTUNJ1Y/AFFIRMATJVE ACTION EMPLOYER -50% RECYCLED/10% POST-CONSUMER PAPER
4. se8n 9: Please list the individual inorgan.discussed.
If you have any questions, please call me at 919-733-2801 ext. 350.
Sincerely,,
I
Nile P. Testerman, P.E.
Environmental Engineer
NORTH CAROLINA
DEPARTMENT OF ENVIRONa,JT AND NATURAL RESOURCES
DIVISION OF WASTE MANAG~NT
MICHAEL F. EASLEY, GOVERNOR
William G. Ross Jr., SECRETARY
WILLIAM L. MEYER, DIRECTOR
Memorandum
To: Nile Testerman
Environmental Engineer
.• f:edera!,Rcmediation Branch
Fram: Hanna Assefa ,/\.l1r
Environmental Toxicologist
Inactive Hazardous Sites Branch
February 23, 2001 _
Re: Baseline Ecological Risk Assessment Report Landfill No. I
Weyerhaeuser Company
Martin County, North Carolina
I have reviewed the subject document and offer the following comments:
I. Metals that have shown potential unacceptable risk have been compared to national or regional
background levels. Why were they not compared to site specific background concentrations?
2. There was one short tailed shrew sample that had dioxin and mercury concentrations ten times that
detected in the other mammalian samples. Other metals were not analyzed for in that sample.
How was this data used?
3. The concentration observed in cover soils for copper and selenium depicted in FigureJ-1 is
. incorrect.
4. The tables in appendix f have footnotes but the footnotes have not been identified in the body of the
tables. Also, the footnotes for dioxin should be 2 and 3 not I and2.
5. Under findings and conclusions (Section 9) chemicals that have a hazard quotient > I for the
maximum concentration detected and NOAEL were assumed to have limited potential to pose
· unacceptable risk to the assessment endpoint in question. These assessment endpoints should be
retained for determining the final RGO's. -· · ·· · · ·
6. A table sho,...,ing the most sensitive assessment endpoint for each chemical and the pRGO's would
be helpful.
1646 MAIL SERVICE CENTER, RALEIGH, NORTH CAROLINA 27_699-1646
· 401 OBERLIN ROAD, SUITE 150; RALEIGH, NC 27605
PHONE: [phone] IFAX: 919-715-3605
. AN EQUAL OPPORTUNrTY/AFFIRMATNEACTION EMPLOYER· 50% RECYCLE0/10% POST-CONSUMER PAPER
!
• •
...._
UNITED STATES ENVIRONMENTAL PROTECT!
REGION 4
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960
0
[}, G 1£</i;,' IE n \II ,i ~
n JUL 2 o 200, --D
I SUPERFUND SECTION
February 20, 2001
Rodney Proctor
CHI L28
Director, Environmental Affairs
Weyerhaeuser Company
PO Box 9777
Federal Way, WA 98063-9777
RE: Approval of the Final Remedial Investigation Report, Former Chlorine Plant Area,
Weyerhaeuser, Martin Cou_nty, North Carolina
Dear Mr. Proctor:
The United States Environmental Protection Agency (EPA) has completed it's review of the
above referenced document The original report was submitted on June 30, 2000. The EPA
provided comments in a letter dated October 31, 2000. A response to comments and page
revisions for the Final report were received on January 24, 2001.
With the page revisions, and response to our October 31, 2000 comments, the EPA approves the
document as the Final Remedial Investigation Report for the Former Chlorine Plant Area.
If you have any questions, please call me at (404)-562-8799.
-
• A. Weyerhaeuser
J11e furure is growing·
Decemher 20, 2000
A. Stanley Mciburg
Deputy Administrator
EPA Region 4
61 Forsyth Street, S.W.
Atla.11\a, GA 30303-8960
Dear Mr. Meiburg:
' . . ,__, : .· . ...; . ,, ,..; ~ ,.,e'1 e,l,., ,..., ,......
Pl"!"''~
Corpo11tte Heridqu11r~ers
PD Box 9777
F,dml Way WA 981163-,777
T,I 1153) 914 ms
This letter is· to follow up on the Novemher 9th meeting and provide you with our view of the
proposed "Partnership Agreement" received on November 16, 2000. ·
Weyerhaeuser has reviewed the proposed "Partnership Agreement", requesled and received
clarifications from Beth Walden, and finds the Agreement unacceptable for various reasons,
some of which arc:
• Information flow is one-sided. Weyerhaeuser is to provide information to USEPA in 15 days
but United States Environmental Protection Agency (USEPA) will not provide draft
documents that would allow meaningful input from our technical staff ..
• No real opportunity for Weyerhaeuser to challenge specific elements of the documents or ·
data and no mechanism to discuss the technical inadequacies. The USEPA is not committed
to any response and will only incorporatc-comment-s "with which it is.in agreement" or
"deems important".
• Inadequate time period for document review and comment (i.e. 10 days ~fler re1;eipt of the
final document). This time frame for review is controlled hy the Rem_edial Project Manager
and is apparently not ncxible. The short time compromises our ability to properly evaluate
the documents w1d prepare written comments for consideration.
The Weyerhaeuser technical staff continues to have a concern that the current scope of work,
including the stated 90% completion of the Remedial Investigation, is inadequate for compliance
with the NCP and will result in flawed risk evaluation and remedy analysis. We are highly
skeptical, based upon our field observations, that the.cu_rrent EPA contractor has the background
and experience required for such a complex undertaking. We a.re also doubtful that a hydro-
dynamic model of the complex Roanoke River system cw1 be adequately calibrated and
interpreted by July 31, 2001 as indicated by your staff._
Given the current unbending position by EPA Region IV staff, Weyerhaeuser has no choice but
lo begin to initiate the following activities:
December 20, 2000
Stanley Mciburg
Page 2
• •
• Prepare to closely oversee all site work and contractor activities
• Document all deficiencies in field work
• Develop every possible legal and technical defense against EPA seeking cost
reimbursement for work that doe, not complywith NCP,
I want to reemphasize Weycrhaeuser's desirc·to assume-the respon~ibility for the Lower Roanoke
River Study. We continue to believe that this is the best uppronch and that this is the way that
Congress assumed the Superfund Law would work (i.e. Willing PRP's would fund the work with
EPA staff oversight). We have been disappC1inted that the staff in Region IV have been
unwilling to approve this approach.
Weyerhaeuser has an excellent track record when worlQng with numerous PRP groups and has
lead at least three major Superfund projects including the on-going project at Plymouth mill.
Based on our previous successes, we urge you to re-evaluate the staff position and allow us to
assume the lead on the Lower Roanoke River project. We are ready and willing to take on this
responsibility,
Very truly yours,
J.P. Odendahl for
Rodney Proctor
c: Dick Green
Robert Jourdan
Phil Vorsatz
Beth Walden
Gary Risner -Sort 52
Joe Jackowski -CH2J28
Mr. Rodney Proctor
Weyerhaeuser
PO Box 9777
1u:
•
Federal Way, WA 98063-9777
Dear Mr. Proctor:
•
DRAFT
I am writing in response to your letter of December 20, 2000, regarding the EPA's initial draft of a partnership agreement for sharing information and soliciting Weyerhaeuser input on the Remedial lnvestigation and Feasibility Study (RI/FS) for Operable Unit 2 of the Weyerhaeu~er Plymouth Site (Lower Roanbke River):" The concept of a partnership agreement was discussed in our meeting of December 9, 2000. A draft was provided to your contact, Kathy Huibregtse, on November 16, 2000, and was discussed with her during the week of December 11, 2000 ..
In your letter you present your view of EPA'~ draft process as not sufficiently flexible, without adequate time or opportunity to rcvi'ew and discuss EPA documents. -As discussed in our meeting the intent of the draft agreement was io provide a process for obtaining Weyerhaeus~r review and input to draft documents in a way that would be meaningful, but not delay the process. As discussed between Ms. Huibregtse and Beth Brown, the EPA Remedial Project Manager, Weyerhaeuser was to be given the specific oppoitunity to comment on the upcoming FS Screening Technical Memorandum and to palticipate in the fS scoping meeting, both significant deliverables. I regret ifit was not made· cle~r at that t_i-1_nc that EPA woul.d be flexible on most but not all review times (sampling plans tend to require shalt turn-around due to the logistics of field work). Review times in excess of the two weeks proposed would likely be granted for large complex documents.
lfyou would like to propose specific,Janguage changes to the proposed agreement, my staff and J would consider them seriously. Work on the project is not, however, being delayed while these issues are discussed. If you conclude thara workable agreement that meets your needs is not possible, EPA will accept that as well. ln that case EPA will periodically share with you, on our own, information on the scope and progress of our investigation and studies, as• appropriate. EPA will continue to request, and expect Weyerhaeuser to provide, existing information related to the Site.
. ,·:,..._
·,
l 1 :(:? i✓o .001 ? .OS • •
2
I believe strongly that the concern you express in your letter regarding the adequacy of EPA's efforts under the current scope of work is unwarranted. As you are aware EPA is utilizing resources, internal and external, with much expertise in· areas needed to accomplish this work. EPA can and will ensure the adequacy of all _work and its consistency with the NCP. As discussed in our meeting of December 9, 2000, EPA does not believe it is in the best interests of the project or the Superfund program in Region 4 to-,witch leads on this Site at this time. . . ... : 'i:·:.: ,.·.-. If you would like to discuss thi~ further, please feel free to contact me, or contact Beth Brown at [phone].
Sincerely,
A Stanley Meiburg
Deputy Regional Administrator
\ . , I' .·, : .: 1 Ii,: ' • , I
l·,11 • I
-~. [,, j \.-,,.,., ,,
I.
Integral.
Environ . ta/ • Solutions
t,J~ 12:C
744 Heartland Trail 53717-1934
P.O. Box 8923 53708-8923
Madison, WI
Telephone: [phone]
Fax, 608-831-3334
November 16, 2000
Ms. Jennifer Wendel
Remedial Project Manager
USEPA Region IV
DEC 1 2000
::;UPERFUND SECl"ION
61 Forsyth Street, SW
Atlanta, Georgia 30303-3104
Subject: Weyerhaeuser Welch Creek Work Plan Addendum 3.0
Dear Jennifer:
Attached is the Welch Creek Work Plan Addendum 3.0 for the additional sampling activities that we
agreed to implement during our September 19 and 20, 2000 meeting in Atlanta, Georgia. The
approach to the hydrologic calculations is being submitted under separate cover. If you approve the
plan, the anticipated schedule is that the described activities would be performed during the week of
November 27, 2000, with actual sample collection initiated on November 28, 2000. We expect work to
last about 7 days.
Please review and sign the signature line on this letter if you approve this addendum. If you have
any questions, please contact me at 608-662-5178.
Sincerely,
RMT, Inc.
!{~~b,1~
Kristopher D. Krause
Senior Project Manager
cmk
Attachment
Approved By
Jennifer Wendel
Remedial Project Manager
cc: Hanna Assefa, Niles Testerman -NCDENR
Tom Augspurger -U.S. Fish and Wildlife
Del Baird, Lynn France, Mike Profit, Murray Wade -CDM Federal
Kevin Koporec, Ted Simon, Sharon Thoms, Philip Vorsatz -USEPA
Rodney Proctor, Jeff Stamps, Steve Woock-Weyerhaeuser
Date
I:\ WPMSN\PJl\ 00-USIOU\3.t\ L0005 I003~-0l 2.DOC
• •
Welch Creek Remedial Investigation/Feasibility Study (RI/FS)
Work Plan Addendu1n 3.0
Weyerhaeuser Facility, Martin County, North Carolina
Overview
The United States Environmental Protection Agency (USEPA)-approved remedial investigation
activities for the Welch Creek area were completed in 1999. However, after the USEPA's
technical review of the draft Welch Creek Remedial Investigation (RI) Report and a subsequent
meeting to discuss the USEPA's comments, two areas were identified that require additional
sample collection and analysis: (1) surface water sampling for low-level mercury analyses, and
(2) reference site fish tissue sampling for mercury. Because there is also no quantified mercury
data available for the upstream Roanoke River surface water and representativeness of the
available dioxin surface water information is uncertain, an additional surface water sample will
also be collected from the Roanoke River, and is included in this addendum. The Work Plan
Addendum identifies the objective of each task and the investigation methods that will be used
to obtain the required information. This supplemental data will be integrated into the final
Welch Creek RI and Baseline Ecological Risk Assessment (BERA) Reports.
Additional Sample Collection Activities
Task 1: Surface Water Sampling for Low-Level Mercury
Background and Objective:
During the USEPA's review of the draft Welch Creek RI, it was noted that the detection
limit of the method used for mercury in surface water exceeded the surface water
quality standard for North Carolina, which is an Applicable or Relevant and
Appropriate Requirement (ARAR). Thus, no conclusions can be made about current
surface water mercury concentrations relative to the ARAR. Because approved
methods now exist to analyze mercury at concentrations relevant to the ARAR,
Weyerhaeuser has agreed to conduct additional surface water sampling of Welch
Creek surface water and of selected background sampling locations under flow
conditions that are not influenced by storm or excessive wind tide events. The samples
will be analyzed using low level analytical techniques. These results will be compared
to the North Carolina surface water quality standard of 0.012 rig/ L for total mercury
and utilized in the updated human health and ecological risk assessments.
1:\ \Vl'l-1SN\ !'fl\ 00.os I no\3•1\Z0005 I003-1·007. DOC 11/16/00
• •
Project Approach:
Surface water samples will be collected at three locations from Welch Creek and from
two reference locations on Conaby Creek. Surface water samples will be collected at
the same locations as the surface water samples that were previously collected as part
of the RI (i.e., MT-1, MT-6, MT-8, CC-6, and CC-8; see Figure 4-4 and 4-5 of the RI/FS
Work Plan, dated October 1998).
The surface water samples will be collected using procedures specified in the approved
RI/ FS Work Plan (RMT, 1998). Samples will be collected from mid-channel at each
transect location and from mid-stream depth. Surface water will be drawn into
precleaned laboratory bottles or transfer containers using a peristaltic pump and
single-use, precleaned tubing. The samples will be collected and handled following
the clean-hands-dirty-hands collection principle defined in the USEPA Method 1669.
Low-level total mercury and methyl mercury analysis will be performed using
Method 1631 by Frontier Geoscience Laboratory, as described in the Quality Assurance
Project Plan (QAPP; RMT, 1998).
Task 2: Roanoke River Upstream Surface Water Sampling
Background and Objective:
To date, the most recent information available for Roanoke River surface water quality
of the Welch Creek constituents of concern (COCs) is the NCDEHNR revised SIP
report (NCDEHNR, 1996). This testing did not quantify low-level mercury
concentrations. Furthermore, the data collection techruques are not well defined and
thus the representativeness of the sample data is uncertain for evaluating the
significance of Welch Creek as a source of either mercury or 2,3,7,8-PCDD/PCDF to
the Roanoke River. To address this concern, surface water sampling will be conducted
at one upstream Roanoke River location under flow conditions that are not influenced
by storm or excessive wind tide events. These conditions will provide a conservative
estimate of the background mercury and dioxin TEQ concentration in the river. The
sample will be analyzed for dioxins and furans as well as mercury. Total mercury and
methyl mercury will be analyzed using low-level analytical techniques.
Project Approach:
A surface water sample will be collected from mid channel in the Roanoke River
upstream from the mill at the location where the powerlines cross the river. This
location is 4.3 river nules (6.9 km) upsti•eam of the mouth of Welch Creek and is
representative of background conditions because it is also upstream of the distributary
channels in the Roanoke delta and is normally free-flowing. Because this sample will
be used to assess the flux of dioxin and mercury in the Roanoke River, this sample will
2 !:\ WP/\\SN\PJT\00•05100\3'1\%0005IO0J.I-007.DOC 1 J/ 16/00
• •
be collected from four equally spaced depth intervals, similar to the whole-water
samples that were previously collected in Welch Creek.
Surface water will be drawn from each depth interval into precleaned h·ansfer
containers using a peristaltic pump and single-use, precleaned tubing. Equal volumes
from each depth interval will be poured into the sample bottles to form the composite
utilized for analyses. The samples will be collected and handled following the clean-
hands-dirty-hands collection principle defined in the proposed USEPA Method 1669.
Suspended solids analyses will be performed on the composite sample using the
analytical procedures from the approved QAPP (RMT, 1998). Low-level total mercury
and methyl mercury analysis will be performed using Method 163] by Frontier
Geoscience Laboratory, as described in the Quality Assurance Project Plan (QAPP;
RMT, 1999). The 2,3,7,8-PCDD/PCDF analysis will be performed using Method 16l3
by WATS Laboratory, as described in the Quality Assurance Project Plan (QAPP; RMT,
1999).
Task 3: Conaby Creek Whole Fish Tissue Collection
Background and Objective:
Whole fish were not collected in Conaby Creek during the initial RI activities, and fish
tissue data for mercury from other nearby water bodies were used for comparison
purposes in the RI and BERA. Upon review of the information, USEPA preferred a
comparison to the site-specific reference location, Conaby Creek. Additional data are
necessary to allow appropriate comparisons for background mercury concentrations in
whole fish tissues. To address this issue, Weyerhaeuser will collect and analyze whole
fish tissue samples from the site-specific reference location, Conaby C~eek.
Project Approach:
To maintain consistency and to facilitate comparison of results to the Welch Creek data
already collected, the additional whole fish tissue collection activities planned for
Conaby Creek will be the same as those conducted during the previous data collection
activities at Welch Creek. The specific objective of the additional fish collection
activities in Conaby Creek is to provide a more complete reference data set for
comparison of the whole fish tissue results obtained from Welch Creek. The Conaby
Creek whole fish tissue results will be used in the preparation of the Final Remedial
Investigation and Baseline Ecological Risk Assessment Reports for the Welch Creek
area.
The following narrative presents collection, preparation, and analytical protocols and
procedures for characteriwtion of whole fish tissues from Conaby Creek. The
3 I:\ W l't-lSN\l'/T\00-0S l00\3'1\Z0U0S 10034-007.l>OC 11 / 16/00
• •
collection of fish requires scientific collection permits issued by the North Carolina
Marine Fisheries Commission and North Carolina Wildlife Resources Commission
(NCWRC). Additional information on the process required to obtain these scientific
collection permits was provided in Appendix C of the Ecological Risk Assessment
Study Design and Sampling and Analysis Plan for the Welch Creek area (RMT, 1999).
Fish Col/ectio11 a11d Ha11dling
Fish will be collected in the vicinity of transects CC-6 and CC-8, in Conaby
Creek (See Figure 5-2 of the Ecological Study Design [RMT, March 1999]). The
actual distance up and downstream from the specific transect location will
depend upon the availability of fish.
As with Welch Creek fish tissue collections, various fish collection techniques
will be available and employed as necessary. The primary fish collection
method proposed for use in Conaby Creek will be boat electrofishing.
Supplemental collection methods, including gillnetting, dip netting, and
minnow traps, will be used as necessary.
Fish collection and handling in the field is designed to minimize potential cross
contamination and assure sample quality control. To meet the objective of
these proposed fish sampling activities, the fish collection efforts will target
those types of fish species (i.e., bottom feeding fish and upper trophic level
predator fish) used for the conservative risk analysis. Additionally, the fish
collection efforts will target fish taxa (i.e., large and small forage fish) used to
support the alternative site-specific risk analysis.
If practical, the number of fish collected at each reference location will be
sufficient to provide enough tissue for three analytical replicates for each of the
four fish types (i.e., bottom feeders, predators, large forage fish, and small
forage fish). If sufficient fish tissue for three replicates cannot be obtained from
the transect locations, a minimum of two replicates will be collected from each
sampling location.
Procedures will follow the guidance in the North Carolina Department of
Environment and Natural Resources (NCDENR) Standard Operating
Procedure (SOP) manual (NCDENR, 1997), where appropriate, and Guidance for
Assessing Che111icnl Con tn111i11ntion Dntn for Use i11 Fish Advisories (USEP A, 1995) as
needed.'
4 I:\ IVl'MSN\!'JT\00-05100\.1-1\Z0Ul)5[0U.l,l-007.DOC JI/ !6/(/0
• •
Fish Tissue Preparatiou
Whole fish tissue samples will be shipped to EnChem Laboratories in Madison,
Wisconsin, for initial processing. A processing and analysis request and chain-
of-custody sheet will accompany the shipped samples.
The handling and preparation of whole fish tissue for analysis will be
consistent with the protocols described in the Welch Creek Ecologicnl Risk
Assess111e11t Study Design nnd Snmpling mu/ Analysis Pinn (RMT, 1999).
Fish Tissue Analysis
Homogenized fish tissue composites will be analyzed for total mercury by
USEPA Method 7471A.
Sample preparation and analyses will be performed following the same
procedures utilized for the previous Welch Creek fish testing. Mercury data
will be reported on a wet-weight basis. Lipid and moisture content will also be
determined. Additional information on analytical requirements and
specifications are presented in the QAPP (RMT, 1998).
Data Management and Reporting
Data validation and management activities will be conducted consistent with applicable
guidelines as outlined in the Ecological Risk Assessment Study Design and Sampling and
Analysis Plan for the Welch Creek area (RMT, 1999) and associated reference work planning
document (QAPP; RMT, 1998).
Sixty days following receipt of validated analytical data, the modified draft Remedial
Investigation (RI) for the Welch Creek source area will be provided to the USEP A.
5 I:\ W 1'r.1SN\ l'JT\00-05 lO0\J.!\Z0005JODJ.l•D07.DOC l 1/ 16/00
November 8, 2000
lntegrat.
E11viro111 _ ,,ta/
Solutions
Ms. Jennifer Wendel
Remedial Project Manager
United States Environmental Protection Agency, Region IV
61 Forsyth Street, SW
Atlanta, GA 30303-3104
Subject: Welch Creek RI/FS Work Plan Addendum 3.0
Weyerhaeuser Company Site,
State Road 1565, Martin County, North Carolina
Dear Ms. Wendel:
wey--?<_1
• 744 Heartland Trail 53717-1934
P.O. Box 8923 53708-8923
Madison, WI
Telephone: [phone]
Faxc 608-831-3334
RECE/\/ED
NOV 142000
SUPERFUND SECT!O~'
In response to the United States Environmental Protection Agency's (USEPA's) comments on the
draft Welch Creek RI and to the subsequent meeting in Atlanta on September 19 and 20, 2000, RMT
has prepared, and has enclosed, a Work plan Addendum to address the additional data collection
activities that are required to meet the objectives of the remedial investigation. Specifically, this
addendum addresses sampling tl1e surface water in Welch Creek and Conaby Creek for low-level
mercury, sampling the surface water in the Roanoke River upstream from the Weyerhaeuser facility
for dioxin/furan and mercury, and whole-fish tissue sampling for mercury analysis at Conaby Creek.
A separate Work Plan Addendum is being prepared that presents the hydrologic calculation
approach to further assess precipitation-related flow conditions as agreed to in the meeting in Atlanta
on September 19 and 20, 2000.
Please review and approve the enclosed Work Plan Addendum by signing in the space provided
below. As always, if you have any questions, please call me.
Sincerely,
Enclosure
cc: Steve Woock, Weyerhaeuser Company
Rodney Proctor, Weyerhaeuser Company
Jeff Stamps, Weyerhaeuser Company
Nile Testerman, NCDENR
Approval By
Ms. Jennifer Wendel
Remedial Project Manager
Date
I:\ \\/!'MSN\ Pff\00--05100\34\ 1.00051003-1-0IO.DOC 11/08/00
• •
Welch Creek Remedial Investigation/Feasibility Study (RI/FS)
Work Plan Addendun1 3.0
Weyerhaeuser Facility, Martin County, North Carolina
Overview
The United States Environmental Protection Agency (USEPA)-approved remedial investigation
activities for the Welch Creek area were completed in 1999. However, after the USEPA's
technical review of the draft Welch Creek Remedial Investigation (RI) Report and a subsequent
meeting to discuss the US EPA' s comments, two areas were identified that require additional
sample collection and analysis: (1) surface water sampling for low-level mercury analyses, and
(2) reference site fish tissue srnnpling for mercury. Because there is also no quantified mercury
data available for the upstream Roanoke River surface water and representativeness of the
available dioxin surface water inforn1ation is uncertain, an additional surface water sample will
also be collected from the Roanoke River, and is included in this addendum. The Work Plan
Addendum identifies the objective of each task and the investigation methods that will be used
to obtain the required information. This supplemental data will be integrated into the final
Welch Creek RI and Baseline Ecological Risk Assessment (BERA) Reports.
Additional Sample Collection Activities
Task 1: Surface Water Sampling for Low-Level Mercury
Background and Objective:
During the USEP A's review of the draft Welch Creek R[, it was noted that the detection
limit of the method used for mercury in surface water exceeded the surface water
quality standard for North Carolina, which is an Applicable or Relevant and
Appropriate Requirement (ARAR). Thus, no conclusions can be made about current
surface water mercury concentrations relative to the ARAR. Because approved
methods now exist to analyze mercury at concentrations relevant to the ARAR,
Weyerhaeuser has agreed to conduct additional surface water sampling of Welch
Creek surface water and of selected background sampling locations under flow
conditions that are not influenced by storm or excessive wind tide events. The samples
will be analyzed using low level analytical techniques. These results will be compared
to the North Carolina surface water quality standard of 0.012 rtg/L for total mercury.
Project Approach:
Surface water samples will be collected at three locations from Welch Creek and from
two reference locations on Conaby Creek. Surface water samples will be collected at
!:\ Wl'I-ISN\l'Jl\00~05 l00\3-1\ZU005J003-l-007.DOC J 1/08/00
• •
the same locations as the surface water samples that were previously collected as part
of the RI (I.e., MT-1, lv!T-6, MT-8, CC-6, and CC-8; see Figure 4-4 and 4-5 of the R[/rS
Work Plan, dated October 1998).
The surface water samples will be collected using procedures specified in the approved
Rl/FS Work Plan (RMT, ·1998). Samples will be collected from mid-channel at each
transect location and from mid-stream depth. Surface water will be drawn into
precleaned laboratory bottles or transfer containers using a peristaltic pump and
single-use, precleaned tubing. The samples will be collected and handled following
the clean-hands-dirty-hands collection principle defined in the USE PA Method 1669.
Low-level total mercury and methyl mercury analysis will be performed using
Method 1631 by Frontier Geoscience Laboratory, as described in the Quality Assurance
Project Plan (QAPP; RMT, 1998).
Task 2: Roanoke River Upstream Surface Water Sampling
Background and Objective:
To elate, the most recent information available for Roanoke River surface water quality
of the Welch Creek constituents of concern (COCs) is the NCDEI-INR revised SIP
report (NCDEI-INR, 1996). This testing did not quantify low-level mercury
concentrations. Furthermore, the data collection techniques are not well defined and
thus the representativeness of the sample data is uncertain for evaluating the
significance of Welch Creek as a source of either mercury or 2,3,7,8-PCDD/PCDF to
the Roanoke River. To address this concern, surface water sampling will be conducted
at one upstream Roanoke River location under flow conditions that are not influenced
by storm or excessive wind tide events. These conditions will provide a conservative
estimate of the background mercury and dioxin TEQ concentration in the river. The
sample will be analyzed for dioxins and furans as well as mercury. Total mercury and
methyl mercury will be analyzed using low-level analytical techniques.
Project Approach:
A surface water sample will be collected from the Roanoke River upstream from the
mill at the location where the powerlines cross the river. This location is 4.3 river miles
(6.9 km) upstream of the mouth of Welch Creek and is representative of background
conditions because it is also upstream of the distributary channels in the Roanoke delta
and is normally free-flowing. Samples will be collected from mid-cham1el at each
transect location. Because this sample will be used to assess the flux of dioxin and
mercury in the Roanoke River, this sample will be collected from four equally spaced
depth intervals, similar to the whole-water samples that were previously collected in
Welch Creek.
I:\ W J',\ISN\ l'Jl'\IJIJ.IJ5 J00\3-I\Z0005 I 00J,1-007. UOC 11/08/00
• •
Surface water will be drawn from each depth interval into precleaned transfer
containers using a peristaltic pump and single-use, precleaned tubing. Equal volumes
from each depth interval will be poured into the sample bottles. The samples will be
collected and handled following the clean-hands-dirty-hands collection principle
defined in the proposed USEPA Method 1669. Low-level total mercury and methyl
mercury analysis will be performed using Method 1631 by Frontier Geoscience
Laboratory, as described in the Quality Assurance Project Plan (QAPP; RMT, 1999).
The 2,3,7,8-PCDD/ PCDF analysis will be performed using Method 16l3 by WATS
Laboratory, as described in the Quality Assurance Project Plan (QAPP; RMT, "1999).
Task 3: Conaby Creek Whole fish Tissue Collection
Background and Objective:
Whole fish were not collected in Conaby Creek during the initial RI activities, and fish
tissue data for mercury from other nearby water bodies were used for comparison
purposes in the RI and BERA Upon review of the information, USEPA preferred a
comparison to the site-specific reference location, Conaby Creek. Additional data are
necessary to allow appropriate comparisons for background mercury concenh·ations in
whole fish tissues. To address this issue, Weyerhaeuser will collect and analyze whole
fish tissue samples from the site-specific reference location, Conaby Creek.
l'ro j ect Approach:
To maintain consistency and to facilitate comparison of results to the Welch Creek data
already collected, the additional whole fish tissue collection activities planned for
Conaby Creek will be the same as those conducted during the previous data collection
activities at Welch Creek. The specific objective of the additional fish collection
activities in Conaby Creek is to provide a more complete reference data set for
comparison of the whole fish tissue results obtained from Welch Creek. The Conaby
Creek whole fish tissue results will be used in the preparation of the Final Remedial
Investigation and Baseline Ecological Risk Assessment Reports for the Welch Creek
area.
The following narrative presents collection, preparation, and analytical protocols and
procedures for characterization of whole fish tissues from Conaby Creek. The
collection of fish requires scientific collection permits issued by the North Carolina
Marine Fisheries Commission and North Carolina Wildlife Resources Commission
(NCWRC). Additional information on the process required to obtain these scientific
collection permits was provided in Appendix C of the Ecological Risk Assessment
Study Design and Sampling and Analysis Plan for the Welch Creek area (RMT, 1999).
l:\ WP/\!SN\ !'JT\00·05100\3,1\ZOOOS !0034·007. DOC I J/08/00
• •
Fis/, Colleclio11 anti f11111tlli11g
Fish will be collected in the vicinity of transects CC-6 and CC-8, in Conaby
Creek (See Figure 5-2 of the Ecological Study Design [ Rlv!T, March ·19991). The
actual distance up ;:1nd downstrean1 fron1 the specific transect location will
depend upon the availability of fish.
As with Welch Creek fish tissue collections, various fish collection techniques
will be available and employed as necessary. The primary fish collection
method proposed for use in Conaby Creek will be boat electrofishing.
Supplemental collection methods, including gillnetting, clip netting, and
1ninnow traps, will be used as necessary.
Fish collection and handling in the field is designed to minimize potential cross
contamination and assure sample quality control. To meet the objective of
these proposed fish sampling activities, the fish collection efforts will target
those types of fish species (i.e., bottom feeding fish and upper trophic level
predator fish) used for the conservative risk analysis. Additionally, the fish
collection efforts will target fish taxa (i.e., large and small forage fish) used to
support the alternative site-specific risk analysis.
If practical, the number of fish collected at each reference location will be
sufficient to provide enough tissue for three analytical replicates for each of the
four fish types (i.e., bottom feeders, predators, large forage fish, and small
forage fish). lf sufficient fish tissue for three replicates cannot be obtained from
the transect locations, a minimum of two replicates will be collected from each
sampling location.
Procedures will follow the guidance in the North Carolina Department of
Environment and Natural Resources (NCOENR) Standard Operating
Procedure (SOP) manual (NCDENR, 1997), where appropriate, and Guidm1ce for
Assessing Chemical Co11/nminatio11 Dain for Use in Fis/, Advisories (USEPA, 1995) as
needed.
Fish Tissue Preparation
Whole fish tissue samples will be shipped to EnChem Laboratories in Madison,
Wisconsin, for initial processing. A processing and analysis request and chain-
of-custody sheet will accompany the shipped samples.
The handling and preparation of whole fish tissue for analysis will be
consistent with the protocols described in the Welch Creek Ecological Risk
Assess111e11t Study Desig11 and Sa111pli11g n11{/ Analysis Pinn (RMT, 1999).
I:\ IVl'r-.1SN\ Pf]\ 00•05 I 00\34\Z00051003-!-007. DOC l l/08/00
• •
Fis!, Tissue Analysis
I-Iomogenizecl fish tissue composites will be analyzed for total mercury by
USEPA Method 74TIA
Sample preparation and analyses will be performed following the same
procedures utilized for the previous Welch Creek fish testing. Mercury data
will be reported on a wet-weight basis. Lipid and moishue content will also be
determined. Additional information on analytical requirements and
specifications are presented in the QAPP (RMT, ·1998).
Data Managen1ent and Reporting
Data validation and management activities will be conducted consistent with applicable
guidelines as outlined in the Ecological Risk Assessment Study Design and Sampling and
Analysis Plan for the Welch Creek area (RMT, 1999) and associated reference work planning
document (QAPP; RMT, ·1998).
Sixty days following receipt of validated analytical data, a technical memorandum
summarizing the findings of the additional sampling will be provided to the USEPA
I:\ \Vl':-.ISN\ l'Jl\00-05l00\3-I\Z00051003-l-007.DOC 11/08/00
JAM CS 9. HUNT JR,
GOVERNOR
81!...L HOLMAN
SECRETARY
WILLIAM L. MEYER
DIRECTOR
,,
'I
.•·-·
,. • --:1-
y·~~
'
:· :~-.
. f: ..
• NOR.AROLINA DEP/..RTMEI-./T OF
ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WASTE MANAGEMENT
26 June 2000 FILE COPY
Ms. Jennifer Wendel
Superfund Branch, Waste Management Division
US EPA Region JV
6 I Forsyth Street, S. W.
Atlanta, Georgia 30303
SUBJECT: Review of Draft Remedial Investigation Report
Welch Creek Area
Weyerhaeuser Company
Martin County
Dear Ms. Wendel:
The State of North Carolina has reviewed the Draft Remedial Investigation Report for the Welch Creek area at the Weyerhaeuser Company site dated April 2000 and received by the Division on 27 April 2000. The following comments are offered:
I.
2.
3.
4.
5.
6 .
The data from the remedial investigation indicate that the extent of chemicals of potential
concern is not defined. Samples taken at the most downstream location of Welch Creek contain contaminant levels above background concentrations. In addition, samples taken at the interface of sediment and clay in Welch Creek are above background concentrations.
Please explain how the extent of contamination will be determined in the Roanoke River and Welch Creek.
Page 3-3, last paragraph: Please explain why methyl mercury was not included in the analytical tests for sediment.
Page 4-4, greenish-gray silt or sand material: Please state if this area between transects GT· 14 and GT-15 has a strong hydrocarbon-like odor or a sheen as observed on the olive-brown to black clay rich material immediately upstream and downstream.
Table 4-2: Please state if the 2,3, 7,8-TCDD and -TCDF concentrations are the same as the 2,3,7,8-PCDD and -PCDF chemicals of potential concern listed on Table 2-1.
Tables 4-2, 4-3, 4-4 and 4-5: Please state if TEQ' s will be calculated for sediment and surface water as they are for wetland soil and wetland water.
Figure 4-2 and Table 4-2: Please correct the differences in sample interval and material type listed on the figure and table. For example, at location GT-22 on Figure 4-2 the sample
interval is 6-7 feet while on the table it is listed as midpoint.
1646 MAIL SERVICE CENTER, RALEIGH, NORTH CAROLINA 27699•1646
401 OBERLIN ROAD, SUITE 150, RALEIGH, NC :'.7605
PHONE 91 9•733-4996 FAX 91 9-7 l S-3605 AN EQUAL OPPORTUNITY/ AFFIRMATIVE ACTION EMPLOYER -50% RECYCLED/10% POST-CONSUMER PAPER
7.
8.
9.
I I.
12.
Figu--2: The vertical extent of possible contamin.on has not been determined. At
location GT-22 the deepest sediment sample, at the 6-7-foot interval level, contains 2,3,7,8-
TCDD levels at 12.7 ng/kg. Please define the extent of contaminants vertically.
Page 6-6, results: Please state why TEQ's were not calculated for all sediment samples as
I isted in Table 6-1.
Table 6-3: Please state why the TEQ's were not calculated for all surface water samples.
Page I 0.4, Section I 0.2.2: Our office is concerned that dioxin found in the sediment and fish
in Welch Creek may have entered the Roanoke River or downstream water bodies. A
weather event like a hurricane may have allowed dioxin from Welch Creek to enter
downstream water bodies. Please state how Weyerhaeuser plans to investigate possible
dioxin contamination in the Roanoke River or other water bodies.
Page I 0.4, Section I 0.2.2: Site specific data upstream and downstream of Welch Creek
should be used to determine loading to Roanoke River from Welch Creek.
Additional comments from other North Carolina personnel are attached.
If you have any questions, please call me at 9 I 9-733-2801 ext. 350.
Sincerely,
Nile P. Testerman, P.E.
Environmental Engineer
• • UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
Mr. Rodney Proctor
Director, Environmental Affairs
Weyerhaeuser Company
Mail Stop CH I L28
33663 Weyerhaeuser Way South
Federal Way, WA 98003
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960 RECEIVED
MAY 15 2000
May Io, 2000SUPERFUND SECTION
Re: Review and comments on the Draft Remedial Investigation Report for the Former Chlorine Plant
Area, Weyerhaeuser Site, Martin County, North Carolina
Dear Mr. Proctor:
The United States Environmental Protection Agency (EPA) has completed it's review of the subject
document. The document was very well written, and generally fulfills the requirements for a Draft
Remedial Investigation Report (RI). Our comments on the document are included as Attachment I
to this letter. All comments should be incorporated into the Final version of the RI report, or
responded to in writing, The Final version of the RI should be submitted to the EPA after 30 days
following receipt of this letter.
Also with this letter, EPA is approving the ,request to perform a Treatability Study at the Former
Chlorine Plant Area of the Site. A Draft Treatability Study Work Plan and schedule for completion
of the work should be submitted to the EPA for review within 60 days following receipt of this letter.
If you have any questions regarding our comments on the Draft RI report, or would like to schedule
a meeting to discuss the comments, please contact me at [phone],
Attachment
cc: Nile Testerman, NCDENR '
Tom Augspurger, USFWS
Terry Chuhay, CDM Federal
Kathy Huibregtse, RMT
Sine ely,
'"~ ~:::f!-P
Remedial Project Manager
Internet Address (URL),. http://www.epa.gov
Recycled/Recyclable • Printed with Vegelable Oil Based Inks on Recycled Paper (Minimum 30% Postconsurner)
• •
Attachment 1
U.S. EPA Comments on the Remedial Investigation Report
Former Chlorine Plant
Weyerhaeuser Company Site, Martin County, North Carolina
General Comments
I. There is no discussion of spills or mercury usage at the Former Chlorine Plant. Some information
should be added to the document both in the introduction and in sample location justifications
2. There is little description or rationale as to why samples were collected where the were. The
reader is left to make their own rationale as to why the samples were collected at specific locations.
Total mercury concentrations in subsurface soils range from 0.4 to 45,800 mg/kg, a wide range of
values. The median concentration is 2.1 mg/kg, a low value because only about 5 of the 24 samples
were actually in the mercury cell room. Discussion of the low median value is misleading.
3. Many of the soil sampling locations were outside of the soil excavation area. The rational for not
collecting samples until 4 ft bgs within the excavation area was to avoid sampling clean fill.
Therefore, since samples were not collected above the 4 ft elevation at locations outside of the
excavated area, there is a data gap from 0-4 ft.
4. Please indicate whether the drinking water wells have been sampled.
5. The length of time for the source to dissipate by natural groundwater flow was not determined.
6. According to EPA Region IV guidance, if the groundwater is considerec:I to be potable, then "the
future consumption of groundwater for residential purposes should be evaluated." Since the state of
North Carolina considers all groundwaters, except those that have chloride concentrations in excess
of 250 mg/I, as potential sources for potable water, this requirement applies. Further, the state's
groundwater quality standard for mercury, 1.1 µg/1, is an ARAR, and does apply at the site unless
a variance to the standards has been granted.
7. Section 6: There are atmospheric source of mercury. To quantify the mass loading on the river
is a stretch. The presentation of the quantification mercury ofloading is misleading to the public. If
the discussion is Section 6 is going to retained in this RI, then additional work should be done. Please
provide a range and compare the different types ofriver systems and how they will affect the mercury
concentrations. Also, a calculation of the total quantity of mercury in the soils beneath the former
chlorine plant should be added and discussed in terms of a source, not just the mercury levels
currently found in the groundwater. Based on some brief calculations for the soil volume that is
estimated to contain >10 mg/kg of mercury, the corresponding mass of total mercury is 7,450
pounds. Undoubtably, this mass (almost 4 tons) of mercury represents a considerable source. I am
very uncomfortable with the discussion in Section 6.
• •
8. The document is disingenuous in its presentation ofrisk associated with elemental mercury. Since
there is no toxicity value for oral exposure, the entire risk estimate is based on inhalation of dust.
There is no consideration for the toxic effects due to oral or dermal exposure for either receptor. In
cases such as this, use of a surrogate is appropriate. Region IV policy on mercury is to use the
toxicity value for mercuric chloride as a surrogate for total mercury.
9. Please reformat the risk assessment according to the standard format specified in U.S. EPA's·
1997 document entitled: Risk Assessment Guidance for Superfund, Volume I: Human Health
Evaluation Manual, (Part D, Standardized Planning, Reporting, and Review of Superjund Risk
Assessment,).
Specific Comments
I. Section 1.3 Page 1-2 second bullet: Please provide dates for the referenced plans.
2. Section 2.1.4 Page 2-2, Second Paragraph: Please provide the depth of the sheet-piling.
3. Section 2.2 Page 2-3: Please indicate how much mercury was used at the plant over the years, and
how much was disposed. This will help to determine the volume released to the environment. See
general comment I. Also, please provide the location of the permitted off-site commerical landfill
where the D009 hazardous waste was disposed.
4. Section 2.4.1 Page 2-7: Please list the depth of the well intake for 045.
5. Section 2.4.2 Page 2-8 and 2-8: The closest well as described is cross-gradient or perpendicular
to the gradient. From the information provided it can not be stated that they are upgradient.
6. Section 2.4.2 Page 2-9 First paragraph: If the homes are located to the southeast and the regional
flow is to the east the residents are not upgradient.
7. Section 2.4.4 Page 2-9: Please explain the significance of the two square mile area south of the
Plymouth Mill.
8. Section 3.2 Page 3-2 Second Paragraph fourth sentence: Please put units on the -70.
· 9. Section 3.3 Page 3-3 Third sentence: The sentence refers to direct-push CPT Soil sampling.
Should it be DPT?
I 0. Section 3.6.4 Page 3-9 Second sentence: The figure lists the pore water sample as CPPW-03 not
CPPW-07.
11. Section 3.7 Page 3-9: Please indicate whether the surveying was conducted by a registered land
surveyor. Survey notes should be provided if not.
• •
12. Section 3.8 Page 3-10: What make and model ofGPS was used to obtain an accuracy of+/-3
feet. Calibration data should be provided.
13. Table 3-1: Please correct the bottom of screen (depth-ft) for well MW2-2.
14. Section 4. It would be beneficial to show an aerial view of each of the flow regimes.
15. Section 4.1 Page 4-2: Please explain in greater detail why preference was given to visula and
laboratory characterizations over cone penetrometer testing outputs.
I 6. Figure 4-1: Please explain why the Yorktown Aquifer has a"?" after it's name.
17. Figure 4-2: Please explain the reason for the"?" at the end of soil boring CPSB-01.
18. Section 5. I. I Page 5-2: Please include in the section any sample taken a the site that may
represent site specific background mercury concentrations. This data could be compared to the
literature background concentrations.
19. Section 5.1.1 Page 5-3 Fourth paragraph Second sentence: Please indicate the depth of the east
U-drain.
20. Section 5. 1.1 Page 5-4 First paragraph, Second sentence: The remaining portion of the U-drain
and the concrete storage tanks have not been addressed. In addition, the contour lines on Figure 5-1
A indicate the detection of72.4 mg/kg was at location CPSB-15, when in fact it was at CPSB-16.
Please revise Figure 5-1. The discussion should focus on the uncertainty of the full characterization
of the eastern u-drain.
21. Section 5 .1.1 Page 5-4 Second paragraph, Third sentence: Based on the groundwater flow
patterns, mercury could have been transported to CPSB-24. Section 4 stated clearly that due to the
leakage from the cooling towers, the groundwater flow is radial. Furthermore due to the bulkheads,
groundwater flow patterns could likely show a preferential path around them. There is one data point
at this location. It is not likely to be a source area but the last sentence in the paragraph is not
supported by the data.
22. Section 5.2.4 Page 5-11 Third paragraph: The extent of the groundwater mound has not been
determined. The flow to the south-southeast is likely very local. The regional flow in the shallow
aquifer is to the north. Previous sections also make reference to a divide and flow being to the north
and to the south. This is misleading when the we are talking about such a small area. The regional
flow is north.
23. Section 5.2.4 Page 5-11 Fourth paragraph: This somewhat disagrees with the previous
paragraph.
24. Section 5.2.4 Page 5-12 Second paragraph: Since wells CP-03-1, CP-08-1 are not west of the
chlorine plant, they should be discussed with the information in the next paragraph.
• •
25. Section 5 .2.6 Page 5-16: Please state the comparative values for microbial biomass. (Background
at landfill 1 or for the area).
26. Section 5.2.6 Page 5-16: This section does not discus if this is atypical or if microbial community
is stressed and what the potential causes of the stress could be. Does the cooling tower leakage have
an impact on the community?
27. Section 5.3 Page 5-18 Second paragraph: The discussion of the upstream mercury contamination
needs to be further defined. Is there possibly another source?
28. Section 5 .3 Page 5-18 Third paragraph: The upstream bank change is located approximately 600
ft. upstream and the facility is located on the outside of the river bend. Most of the river flow is next
to the bulkhead. This area would not be a typical depositional area. If this area was a depositional
area then the soft sediments would.be much thicker. The bulkhead area receives much of the flow
energy.
29. Section 5.3 Page 5-18: Rail lines just upstream from the bulkhead indicate that this was a material
transfer location and a possible source of mercury spills. Please confirm this assumption and comment
on the likelihood that this may be a source of the upstream mercury contamination.
30. Table 5-2 does not have data for CPSB-25, yet it is located on Figure 5-1.
31. Figure 5-5 A-C: Map A representing the mercury concentrations in the groundwater at surface
elevation 4 to -6 feet is not complete to the 0.010 mg/L concentration. The North Carolina
groundwater standard for mercury is 0.011 mg/L. Please revise the figure to better reflect the NC
standard.
32. Section 6.4 Page 6-6: Add the migration of contaminated sediments down the river and to the
sound.
33. Section 6.4.1, Page 6-7: Future construction activities at the plant will be a surface soil source.
There is a need for shallow soil data outside of the excavation area.
34. Section 6.4.2, Page 6-8 and 6-9: The assumptions that were made in calculating the groundwater
transport of mercury are not supported by the rest of the document. For example the shallow aquifer
hydraulic conductivity and total mercury concentrations are not consistent with earlier presented
values. The thickness of the zones are not consistent and the widths are not justifiable. Justification
for the values used should be provided or the mass of mercury should be recalculated.
35. Section 8.1.1: Please explain in more detail the statement that the flecks of metallic mercury
observed are not due to an ongoing source of mercury (ie: as a separate phase of mercury in soil).
36. Section 8.1.2, Page 8-4: The atmospheric loading needs to be reevaluated. The lower reaches
of the river.are mainly wetlands which work as filters for metals and other contaminants; therefore
the loading of mercury should be less. There is no discussion comparing the Roanoke river basin with
• •
the other studied systems. Furthermore actual surface water data could be used to support this type
of comparison.
• • Rr:------,,.
Transmittal Letter .. ,,_,')
RMT, Inc. ("RMT")
744 Heartland Trail (53717-1934)
PO Box 8923 (53 708-8923)
Madison, WI
Tel. [phone] • Fax [phone]
To: Mr. Nile Testerman
North Carolina Department of
Environmental and Natural Resources
Division of Solid Waste Management
401 Oberlan Road
Suite 150
Raleigh, NC 27605
Prepared By:
Signature:
We are sending
@Report
. COPIES DATE · NO.·,
APR 27 2000
SUPERFUND SECTION
Date: 4/26/00
Project No.: 5100.23
Subject: Weyerhaeuser Company
Martin County, North Carolina
Title Senior Project Manager
DESCRIPTION
1 4/25/00 Remedial Investigation Report -Welch Creek Area
These items are transmitted as checked below:
0For your use
Remarks
Enclosed is a copy of the draft Remedial Investigation Report for Weyerhaeuser Company. This
report was submitted to the USEPA on April 25, 2000.
Please call if you have any questions.
l:\Wl'f.lSN\l'JT\00-05100\2J\UXIOS1002J.020.OOC -l/26/00 TRANLTRLDOT FOR/'-.1 F334 (06/15/99)
April 25, 2000
lntegrateca,
Environn,-.il
Solutions
Ms. Jennifer Wendel
Remedial Project Manager
USEP A Region IV
Waste Management Division
61 Forsyth Street, SW
Atlanta, Georgia 30303-3104
Subject: Remedial Investigation Report. Welch Creek
Weyerhaeuser Company, Martin County, North Carolina
USEPA Docket No.: #98-10-C
Dear Ms. Wendel:
744 Heartland Trail 53717-1934
P.O. Box 8923 53708-8923
Madison, WI
Telephone: [phone]
Faxo 608-831-3334
On behalf of Weyerhaeuser Company in accordance with the Administrative Order by Consent.
RMT, Inc. (RMT), has enclosed six copies of the Re111edial /11vestigatio11 (RI) Report for tHe Welch Creek
area at the above-referenced site. This RI Report for the Welch Creek area was performed consistent
with the approved Re111edial /11vestigatio11 a11d Feasibility Study Work Plan (October 1998).
The available data have been evaluated and are sufficient to support the RI/FS and the remedy
decision-making process. The RI concludes that there is a relatively limited degree of adverse effects
to the ecosystem and that institutional controls are in-place for fish ingestion; therefore, remedial
options that limit the uptake of dioxin by aquatic organisms and fish appear to be the most
applicable. To further develop and screen these types of alternatives, it is recommended that focused
treatability studies be performed to better evaluate in situ technology options for capping ,md
containment. The treatability studies proposed would focus on the placement and performance of
i11 situ options.
The Baseline Ecological Risk Assess111ent Report for the Welch Creek area is being submitted under
separate cover concurrent with this document.
Please review and approve the enclosed report. Upon receiving your written comments, RMT will
begin preparing the final RI report and the Remedial Action Objectives Technical Memorandum for
this area.
If you have questions regarding the enclosed information, please contact either of us.
Sincerely,
RMT,Inc. t~
~uibregtse ~
Principal-In-Charge
cc: Rodney Proctor, Weyerhaeuser Company
Jeff Stamps, Weyerhaeuser Company
Steve Woock, Weyerhaeuser Company
Project File 5100.23
Krist pher D. Krause
Project Manager
I:\ WPM SN\ PJl\00-05100\23\ L000510023-019. DOC
JAMES B. HUNT JR.::.
GOVcRNOR
BILL HOLMAN
SECRETARY
---';:". 1-----~rr:-'T ---... --' - -.. ..____..!.i.:...-.s
• NOR.CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES·
DIVISION OF WASTE MANAGEMENT
20 April 2000
Ms. Jennifer Wendell
Superfund Branch, Waste Management Division
US EPA Region IV
61 Forsyth Street, S. W.
Atlanta, Georgia 30303
SUBJECT: Review of Draft Remedial Investigation Report
Former Chlorine Plant
Weyerhaeuser Company
Martin County
Dear Ms. Wendell:
The State of North Carolina has reviewed the Draft Remedial
Investigation Report for the former chlorine plant at the Weyerhaeuser
Company site dated February 2000 and received by the Divisionon 11
February 2000. The following comments are offered:
1. Page 2-4, Section 2.2: ·Please list the location of the permitted off
site commercial landfill where the D009 hazardous waste was
disposed.
2. Page 2-7, Section 2.4.1: Please list the depth of the well intake fcr
045.
3. Table 3-1: Please correct the bottom of screen (depth-ft) for well
MW-2-2.
4. Page 4-2, Section 4.1: Please explain m greater detail why
1646 MAIL SERVICE CENTER, RALEIGH, NORTH CAROLINA 27699•1646
401 OBERLIN ROAD, SUITE 150, RAL0EIGH, NC 27605
PHONE [phone] FAX [phone]
AN EQUAL OPPORTUNITY/ AFFIRMATIVE ACTION EMPLOYER -50% RECYCLED/10% POST-CONSUMER PAPER
pr.ence was given to visual and l.ratory characterizations
over cone penetrometer testing outputs.
5. Figure 4-1: Please explain why the Yorktown Aquifer has a"?"
after its name.
6. Figure 4-2: Equipotential lines are not drawn for cross section A
to A' due to sparseness of data. Please state if you feel the
equipotential lines could be drawn in the vertical direction as the
hydraulic head data are not as sparse.
7. Figure 4-2: Please explain the reason for the"?" at the end of soi
boring CPSB-01.
8. Page 5-2, Page 5.1.1: Please include in the section any sample
taken at the site that may represent site specific background
mercury concentrations. This data could be compared to the
literature background concentrations.
9. Page 5-9, Section 5.2.2: The ground water standards do apply at
the site unless a variance to the ground water standards has been
granted. Please provide a copy of the variance (See 15A NCAC
2L .0113).
10. Figure 5-5 A-C: The extent of mercury in the ground water has nct
been determined. Map A representing the mercury concentration;
in the ground water at surface elevation 4 to-6 feet is not complete
to the 0.010 mg/L concentration. The North Carolina ground
water standard for mercury is 0.011 mg/L. Please provide
information on the extent of mercury in the ground water.
11. Figure 5-10: The extent of mercury in the sediment has not been
determined. The mercury content in sediment sample CPSD-06
increases with depth. Samples CPSD-09 and CPSD-10, the most
downgradient samples, contain mercury near the 10 mg/kg level.
Please provide information on the extent of mercury in the river
sediment and underlying native sand.
12. P•8-, Section 8.1. i, Subsurface S. Please explain in more
detail the statement that the flecks of metallic mercury observed
are not due to an ongoing source of mercury (i.e., as a separate
phase of mercury in soil).
13. Attached are comments from our Industrial Hygienist on the
baseline human health risk assessment.
If you have any questions, please call me at 919-733-2801 ext. 350.
Sincerely,
11Jv4~
Nile P. Testerman, P.E.
Environmental Engineer