DEQ-CFW_00043418

Hazardous Waste Section
File Room Document Transmittal Sheet
M
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Larry Stanley
NCD047368642
DuPont Fayetteville
Corrective Action (CA)
RCRA Facility Investigation (RFI)
Comments on Phase III (Stage 2) RFI report
5/19/2014
NC HWS
File Room Use Only NCD047368642
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DEQ-CFW-00043418

John E. Skvarla, III
Secretary
May 19,2014
Mr. Jamie A. VanBuskirk
Project Director
DuPont Corporate Remediation Group
6' )24 Fairview Road
Charlotte, NC 28210
Re: Final RCRA Facility Investigation Report
DuPont Fayetteville Works
Fayetteville, NC
EPA ID # NCD 047 368 642
Dear Mr. VanBuskirk:
The North Carolina Hazardous Waste Section (HWS) has completed a review of the
document titled Final RCRA Facility Investigation Report. Due to technical questions raised by
this review process, the HWS has determined that the document does not constitute an
acceptable report. Comments intended to aid with. revisions to the RCRA Facility Investigation
(RFI) report are listed below.
Section
k&-mmu;f,
1) Other than the figure numbers, Figure 5 (Perched Zone Water Thickness) and Figure 6
(Perched Zone Water Thickness) appear to be identical. The elevation of the top of the clay
layer and the thickness of the saturated zone on top of this clay layer (i.e., the perched water zone
thickness) are depicted on both maps. In other words, there are two sets of contours on each
map. The text of the report, however, refers to the two identical maps as if unique information is
shown on each. DuPont-CRG should simplify the text of the report and/or the maps.
2) Willis Creek discharges directly to the Cape Fear River, and the HWS is under the impression
that the creek is a perennial stream. (However, the creek is described in Section 7.2.3 as having
ephemeral characteristics.) The apparent elevation difference between the creek level and the
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DEQ-CFW-00043419

regional groundwater elevation in the vicinity of the creek probably results from lithologic and
stratigraphic variations in the aquifer. Based on the data points cited in the Phase III RFI report
(i.e., monitoring wells SMW-10 and SMW-11), the HWS is reluctant to conclude that
groundwater in the regional aquifer flows beneath Willis Creek. Without additional supporting
data, the HWS recommends that DuPont-CRG reconsider this conclusion and revise the Phase III
report accordingly.
Section 3.2
Phase III RF1 Activities
3) There is an area west of SWMU 16 that is prominently displayed on aerial photos such as
Figure 9 (SWMUIAOC Location Map). At its maximum, the irregularly shaped area measures
approximately 1500 feet by 1300 feet. The area appears to lack vegetation. As a response to this
comment, DuPont-CRG should identify this area, and if information is available, discuss the area
in the Phase III RFI report.
Section
Soil Analytical Data ScreeninZ Process
4) Soil screening criteria are discussed in the HWS's recently updated version of Guidelines for
Establishing Remediation Goals at RCRA Hazardous Waste Sites (12/11/2013). This document
can be accessed at http://portal.ncdenr.org/web/wni/hw/technical/guidance.
Section 7.2.1
Identification of Constituents of Concern
Groundwater
5) DuPont-CRG used EPA's Vapor Intrusion Screening Level (VISL) calculator to evaluate the
potential risk posed by the groundwater to indoor air migration pathway at the DuPont -
Fayetteville facility. The NC Division of Waste Management has developed a guidance
document designed to assist with the investigation and evaluation of vapor intrusion into indoor
air. In the future, all DWM programs, except the UST program, will use this guidance document
to evaluate indoor air scenarios. (The DWM guidance was recently placed on the internet and
can be viewed or downloaded at: http://portal.nedenr.org/web/wm/dwm-new-vapor-guidance.)
The HWS recommends that DuPont-CRG use the DWM guidance to evaluate the potential for
vapor intrusion at the DuPont -Fayetteville facility and compare the results to those achieved
using EPA's guidance.
S I ection 7.2-1
Identification of Constituents of Concern
Surface Water
6) The locations of the surface water samples collected in the Cape Fear River are not shown on
Figure 10 of the RFI report. A map that shows these surface water sampling locations should be
added to the RFI report.
DEQ-CFW-00043420

Section 7.2.1
(le iricatio of Constituents of Concern
Z',roundiFater to Surface Water
7) '17hc text of Section 'eLLl indicates that the anal rtical results for some moortori-rig wells located
adjacent to the Cape Fear Xib-er (LI'W-01 through Ll'' -015) were compared to the ;SIC 2.B
Surface Water Quality- Standards for Class C waters.. Since the sqp ertt of the Cape tear River
adjacent to the DuPont plant was re-classified as a WS-TV surface wester -goy in 2009, this
comparison seems to be i apply p.>iate. Also riot- that a perennial tributary ;,gerkerally has the
same surface outer classii' c ation cr:, the stream into which Jt isc harw es.) DuPort-CRG should
verify that the Cape e Fear River and its tributaries are currently classified. as WS surface -�-atcr
bodies and; it se, revise the tent of Section 2.1 with a. tic>re ine ningfi I comparison.
Section 7.2.3
>Sun iary (if Potential Receptor as Ex. os re frathnivai=s
Soil
) In order to compare arsenic concentrations in sail to backaround concentrations, DuPont-CRG
must collect site-s ecific background soil samples,
Section 7.2.3
Suminan, of Potential Rees for and Ex osure Pathways
Groundwater
9) DuPont-CRG should identify of any cuff -.site: receptors rorlb o Willis Creek an discuss whether
groundwater from the site has the potential to niigate beneath Willis Creek. and impact these
receptors.
Responses to comments and/or revisions to the -'l should be submitted to the HWS
within ninety (.90) days of the recent of this letter by DuPo.. t Corporate Remediation Group. If
your office has questions concerning this coi-respon.dence, please contact me at (919) 70-81.11.
or at
Larry Stanley, Hy rogeolof ist
Division of Waste Management, NC t�E'NR
ec: Jon D. Johnston, t_ S EPA, Region. 4
Mike Johnson, Dt Pora- avettevilie
Bobby Nehns
Bud McCarty
Larry Stanley
[ DuPor,t_'W 41' 's
DEQ-CFW 00043421