RA-841_5701_CA_RPTS_20200107

2725 E. Millbrook Road, Suite 121
Raleigh, North Carolina 27604
Telephone [phone]
Fax [phone]
www.atcgroupservices.com

January 7, 2020

Mr. Mark Petermann
North Carolina Department of Environmental Quality
Division of Waste Management - Underground Storage Tank Section
1646 Mail Service Center
Raleigh, North Carolina 27699

Re: Feasibility Evaluation
Allen Hansen Property
5002 Wake Forest Highway
Durham, Durham County, North Carolina 27703
NCDEQ Risk Ranking H290D
NCDEQ Incident No. 5701
ATC Project No. SLP0570104
Task Authorization: TA-4

Dear Mr. Petermann:

ATC Associates of North Carolina, P.C. is submitting the enclosed Feasibility Evaluation for the
above referenced site. If you have any questions or require additional information, please contact
our office at [phone].

Sincerely,

ATC Associates of North Carolina, P.C.

Elizabeth A. Allyn Gabriel Araos, P.E.
Project Manager Senior Project Manager

Feasibility Evaluation

Allen Hansen Property
5002 Wake Forest Highway
Durham, Durham County, North Carolina 27703
NCDEQ Incident No. 5701
ATC Project No. SLP0570104

TABLE OF CONTENTS

1.0 SITE DESCRIPTION .............................................................................................1
2.0 SITE CHARACTERIZATION .............................................................................1
2.1 Site and Regional Geology ......................................................................1
2.2 Site and Regional Hydrogeology .............................................................1
2.3 Soil Characterization ................................................................................2
2.4 Groundwater Characterization .................................................................2
3.0 REMEDIAL STRATEGIES TO DATE ................................................................3
4.0 REMEDIAL EVALUTAION .................................................................................3
5.0 REMEDIATION STRATEGY ...............................................................................4

TABLES
Table 1 Preliminary Remediation Technologies
Table 2 Remedial Evaluation Cost Estimates

FIGURES
Figure 1 Site Topographic Map
Figure 2 Site Map
Figure 3 Potential Receptor Map
Figure 4 Groundwater Elevation Contour Map
Figure 5 Dissolved Benzene Isoconcentration Contour Map

APPENDICES
Appendix A Mann-Kendall GSI Toolkits
Appendix B AxNano Proposal

AxNano Evaluation January 7, 2020
Allen Hansen Site – Incident #5701 ATC Project No. SLP0570104
1
1.0 SITE DESCRIPTION

The Allen Hansen Property is located at 5002 Wake Forest Highway in Durham, Durham County,
North Carolina. Figure 1 depicts the site on a topographic map and Figure 2 depicts monitoring
well locations and other site features. The site consists of a one-story vacant building. Ten
monitoring wells are associated with the site. In May 1990, Allen Hansen’s well was sampled due
to complaints of gasoline in his water supply well. A receptor survey identified 15 wells within
1,000 feet, ten of which are used for drinking water as shown on Figure 3. The site risk ranking
is H290D. A surface water body is located approximately 500 feet south of the site. Public water
is available to properties along and immediately off Highway 98, Oak Grove Parkway, and Sherron
Road. Properties along Patterson Road, Stallings Road, and Husketh Drive to the north-northeast of
the site were found to be supplied by water supply wells. The nearest surface water body is an
unnamed tributary of Little Lick Creek approximately 490 feet south southwest of the site.

2.0 SITE CHARACTERIZATION

2.1 Site and Regional Geology
According to the Geologic Map of North Carolina, produced by the State of North Carolina,
Geological Survey in 1985, the property lies in the Piedmont Physiographic Province of North
Carolina. The property is located within the Carolina Slate Belt. More specifically, the property
is located within sedimentary rocks of the Chatham Group which consists of conglomerates,
mudstone and sandstone from the Triassic Period.

Boring logs from the September 2011 Soil and Groundwater Assessment Report by Terraquest
Environmental Consultants, Inc. indicated that the site subsurface consisted of tan clay in the
upper approximately 0-10 feet below ground surface (ft bgs). Bedrock was encountered during
the advancement of the soil borings at 10 ft bgs.

2.2 Site and Regional Hydrogeology

The occurrence and movement of groundwater in the Piedmont is within two separate but
interconnected water-bearing zones. A shallow water-bearing zone occurs within the surficial
soils and a deeper zone occurs within the underlying bedrock. Groundwater in the shallow soil
AxNano Evaluation January 7, 2020
Allen Hansen Site – Incident #5701 ATC Project No. SLP0570104
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zone occurs in the interstitial pore spaces between the grains comprising the surficial soils.
Groundwater in this zone is typically unconfined. Groundwater movement is generally lateral
from recharge areas to small streams that serve as localized discharge points. The occurrence
and movement of groundwater in the underlying water-bearing zone within the crystalline
bedrock is controlled by secondary joints, fractures, and faults within the bedrock. On a regional
scale, the direction of groundwater flow is typically from uplands to major streams and
groundwater sinks.

Aquifer testing such as slug testing has not been performed at the site, therefore, hydraulic
conductivity values are not known. Depth to groundwater has historically ranged from 14.60 to
35.35 feet below the top of well casings. Groundwater flow direction at the site is to the west
(Figure 4). Light non-aqueous phase liquid (LNAPL) has not been detected at the site.

2.3 Soil Characterization
Soil excavation was performed in August 2012 during which 943.52 tons of impacted soil was
removed. A 550-gallon orphan tank was discovered during removal. On July 13, 2015, four soil
borings were advanced at the site by a track-mounted Geoprobe utilizing direct push technology.
The soil samples were advanced to the east and west of the area previously excavated in 2012 in
order to define the horizontal extent of residual impacted soils at the site. No petroleum constituent
concentrations were detected above their respective Soil-to-Groundwater MSCCs or Residential
MSCCs standards. The horizontal extent of impacted soils has been defined in the east and west
directions. Based on the limited extent of impacted soils that could be excavated at the site, ATC
did not recommended additional soil excavation at the site. On March 2, 2018, ATC supervised
the installation of soil borings SB-1 through SB-7 in the vicinity of monitoring well MW-5,
MW-9, and WSW-1. Two soil samples were also collected during the installation of MW-9 at
depths of 0-4 feet bgs and 4-8 feet bgs. No petroleum constituent concentrations were detected
above their respective Soil-to-Groundwater MSCCs or Residential MSCCs standards.

2.4 Groundwater Characterization
LNAPL has not been identified at the site; however, concentrations have exceeded Gross
Contamination Levels (GCLs) as recently as July 2014. After the implementation of remedial
strategies starting in November 2014, concentrations have been reduced and remain below the
AxNano Evaluation January 7, 2020
Allen Hansen Site – Incident #5701 ATC Project No. SLP0570104
3
GCLs. During the February 2019 sampling event, the dissolved benzene plume (the constituent with
the greatest number of affected monitoring wells) is defined in the direction of groundwater flow
(Figure 5). The Mann-Kendall GSI Toolkit indicates that concentrations in monitoring wells MW-
1A, MW-2, MW-3, and MW-5 are decreasing or stable with the exception of naphthalene in MW-
1A which exhibits no trend and ethylbenzene in MW-5 which also exhibits no trend, but has been
below the 2L Standard during the last three sampling events. The Mann-Kendall GSI Toolkits for
wells impacted above the 2L Standards with four or more monitoring events are included in
Appendix A.

3.0 REMEDIAL STRATEGIES TO DATE
AFVR
A total of five aggressive fluid and vapor recovery (AFVR) events have been conducted at the
site to date (November 25, 2014; December 29, 2014; July 23, 2015; February 15, 2018; and
January 15, 2019). The events have recovered a total of 1,022 gallons of petroleum impacted
groundwater and 0.69 gallon of petroleum impacted vapor. After the initial AFVR event, most
concentrations decreased significantly and have generally continued to decrease. However, a
rebound was noted in the concentrations during the February 2019 sampling event which
followed the January 2019 AFVR event.

Oxygen Releasing Substrate Sleeves
Oxygen Releasing Substrate (ORS) sleeves were placed in monitoring wells MW-1A, MW-2, MW-
3, and MW-5 on September 19, 2017. Concentrations decreased significantly after the placement of
the ORS sleeves; however a rebound was noted during the February 2019 sampling event.

4.0 REMEDIAL EVALUTAION

ATC has prepared this evaluation of remedial alternatives and proposed approach for an interim
remedial action the above referenced site. ATC is recommending an aggressive approach for
remedial cleanup due to the time frame of the initial incident (1990) and to reduce liabilities
associated with the adjacent water supply wells. The following sections and the attached tables
details our evaluation of remedial alternatives, injectate selection, proposed scope of work, and
estimated costs.
AxNano Evaluation January 7, 2020
Allen Hansen Site – Incident #5701 ATC Project No. SLP0570104
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ATC conducted an evaluation of remedial alternatives as detailed on the attached Table 1. The
reviewed technologies included chemical oxidation using persulfate, soil excavation/removal, air
sparge/soil vapor extraction (AS/SVE), groundwater pump and treat, dual phase extraction,
monitored natural attenuation (MNA), and surfactant injection.

In summary, soil excavation, groundwater pump and treat, dual phase extraction, and surfactant
injection were not selected due to the following: limited impacted soils; site geology (low
permeability soils); site hydrogeology (poor groundwater recovery during previous AFVR events);
and expensive capital costs. The three remaining remedial technologies (chemical oxidation, MNA
and AS/SVE) were further reviewed and cost estimates were prepared. Table 2 presents the
remedial evaluation costs estimates. Based on our review of the available technologies, ATC
recommends the injection of RemRx™ CRP (Controlled Release Polymer) Persulfate as the most
cost effective remedial strategy for the subject site.

The proposed remedy will allow the time released delivery of oxidants to reduce VOCs and
expedite natural attenuation and site closure.

5.0 REMEDIATION STRATEGY

Sodium persulfate is very reactive and produces innocuous byproducts, all of which make it an
excellent choice for environmental applications to treat contaminated groundwater. Upon contact
with benzene and fuel related compounds, persulfate will rapidly mineralize the compounds to
carbon dioxide, unlike aerobic biostimulation methods which may take years to decades to reduce
contaminant concentrations. ATC proposes the emplacement of RemRx™ CRP Persulfate within
nine CRP treatment wells and ten CRP treatment borings to reduce contaminant concentrations in
groundwater at the site. The attached Figure 6 depicts the proposed locations of the proposed
treatment wells and treatment borings.

The proposed strategy for the Allen Hansen Property includes constructing nine CRP treatment
wells using 4-inch diameter schedule 40 polyvinylchloride (PVC) with a 20-foot PVC screened
interval. The top of the screened interval will correspond to the water table. Within each well, a fine
AxNano Evaluation January 7, 2020
Allen Hansen Site – Incident #5701 ATC Project No. SLP0570104
5
mesh sleeve will be lowered in to the well. Once in place the sleeve will be filled with
approximately 75 lbs of CRP Persulfate. An approximate total of 675 lbs of CRP Persulfate is
proposed for the initial treatment within the nine CRP treatment wells. In the event additional
treatments are required, the spent CRP can be easily removed from the wells and disposed as
required, and reapplied if necessary.

For the area located in the NCDOT right of way (MW-1A and MW-3), permanent injection wells
are not feasible in the areas of monitoring wells. Therefore, ten CRP treatment borings will be
advanced by a conventional drill rig capable of advancing a 6-inch diameter borehole. The CRP
treatment boring would be advanced to a depth corresponding to approximately 15 feet below the
water table. Once at depth, drilling tooling will be removed from the boring and CRP will be
backfilled up to the water table. Approximately 82.5 lbs of CRP will be placed into each CRP
treatment boring, totaling 825 lbs of CRP within the ten treatment borings. A copy of the proposal
prepared by AxNano is included in Appendix B.

Following the injection event, ATC will submit an Injection Event Record detailing the injection
activities. Groundwater sampling events are proposed following the injection event at intervals of
one month, three months, and six months post-injection.

TABLES
TABLE 1
PRELIMINARY REMEDIATION TECHNOLOGIES
Allen Hansen Property
5002 Wake Forest Highway
Durham, Durham County, North Carolina
NCDEQ Incident #5701
Media Contaminant
Concentrations Geology Considerations Geochemistry Health & Safety/Accessibility Cost Timeframe Permitting Other
RemRx CRP Persulfate
Oxidant chemicals are injected which
react with the contaminant, producing
carbon dioxide. Most common
delivery is via injection wells or direct-
push injection.
Can be utilized for both soil
and groundwater remediation,
although soil remediation is
more challenging and may not
achieve injectate distribution
at shallow depths.
Challenging for LNAPL
conditions, best for low
groundwater
concentrations.
Success highly dependent on site
geology and effectiveness of
injectate distribution.
Natural organic matter and
other reduced species may
compete for oxidant demand
and therefore reduce
effectiveness.
Some technologies may not be appropriate for active
sites due to safety concerns.
High initial costs for purchase
of injectates, but little O&M
and capital costs. Costs may
be prohibitive for large
plumes. Overall cost
considered moderate in
comparison to other
technologies.
Very short timeframe for
remediation compared to
other technologies.
Injection permitting required.
Technology screening data
may be highly variable for
different injectates. Detailed
evaluation of individual
injectates recommended for
further evaluation.
Chemical oxidation could potentially be effective for
source area remediation. However, chemical oxidation
injectates are typically more cost effective when used for
high contaminant concentrations.
Yes
Excavation and Removal
Physical removal, commonly via
excavation, of contaminated media
and off-site treatment and disposal (or
alternate on-site treatment and
replacement).
Primarily utilized for soil
remediation and removal of
contaminated debris and
materials. Contaminated soil
removal may also assist in
reducing dissolved phase
contaminant concentrations.
Very effective method to
remove highly-impacted
soil
Soil types can impact rate of
excavation (minimal impact);
severe limitations in competent
material (bedrock) that restrict
traditional excavation methods.
No significant concerns
noted.
Safety concerns are similar to those associated with
any construction related excavation project and
include shoring, excavation access (near buildings
and buried utilities), soil types and parameters, and
dewatering.
Costs for excavation can vary
significantly depending on
site conditions (depth of soil
excavation and groundwater,
locations of utilities and
structures, access limitations,
etc.) and treatment and
disposal costs.
Very short timeframe for
remediation compared to
other technologies.
NA
Fugitive emissions (dust) can
be an challenge. Excavation
depths are generally limited
on smaller sites with
improvements.
Soil remediation is not required at this site.No
Air Sparging
Injection of air into the saturated zone
to strip volatile organics and create
oxygenated conditions favorable to
aerobic biodegradation. Where
volatile stripping is the primary
mechanism, SVE is used to remove
vapors.
Primarily utilized for
groundwater remediation, but
SVE typically performed in
conjunction for soil
remediation.
Applicable as long as
there is no free product.
Subsurface heterogeneity causes
injected air to develop fingered
flow patterns resulting in areas that
are not contacted by injected air
(i.e. uneven treatment). Well
spacing and intervals must be
properly designed to ensure
adequate contact with
contamination.
Can create favorable
conditions for iron
precipitation due to increase
in dissolved oxygen levels
(clogging pore spaces and
possible iron fouling when
used with pump & treat
systems).
Accessibility may present challenges based on
size/type of site (location for system building,
installation of sparge wells, trenching etc.). Possible
problems with noise levels, vapors, proximity of
residents or businesses. Possible vapor intrusion into
buildings. Possible groundwater mounding causing
plume to migrate.
Expensive capital costs
usually combined with SVE
system. Lower permeability
zones will require longer
treatment timeframes, thus
increasing costs
Moderate timeframe for
remediation compared to
other technologies.
Injection permitting required.
Air sparging can be used to
deliver alternative gas
mixtures for chemical or
biological treatment. Gases
include cometabolic substrate
(propane), oxidant (ozone), or
reductant (hydrogen sulfide).
Air sparging could potentially be effective for source area
remediation. However, the use of an injection technology
is likely more cost effective than air sparging for the
limited area to be remediated.
Possibly
Groundwater Pump & Treat
Removal of contaminated groundwater
to the surface for treatment.
Aboveground treatment for liquid
phase and vapor phase (if necessary).
Appropriate for groundwater
remediation only.
Wide range of
concentrations can be
removed using air
stripping. Liquid-phase
carbon adsorption as
necessary.
Anisotropic conditions may limit
the ability to create sufficient
drawdown to establish capture
zones. Possible stagnation zones.
Contaminant movement is largely a
function of hydraulic conductivity
of aquifer.
Possible iron fouling of
equipment during
aboveground treatment.
Accessibility may present challenges based on
size/type of site (location for system building,
installation of recovery wells, trenching etc.).
Possible problems with noise levels, vapors,
proximity of residents or businesses.
High capital cost; extensive
O&M required; sampling
requirements for discharge
permitting; high electrical
costs.
May be difficult to achieve
cleanup standards without
additional technology.
Cleanup time generally
considered moderate to long
in comparison to other
technologies.
Discharge permitting required
for treated liquid and possibly
air effluents.
Provides hydraulic control.
Not considered appropriate because this technology is
unlikely to achieve cleanup standards in a reasonable
timeframe. If plume control is needed, pump and treat
could be performed in conjunction with another
technology. However, this does not appear warranted at
this time.
No
Dual Phase Extraction
High vacuum system to remove
various combinations of contaminated
groundwater, free-phase NAP:, and
vapors. Lowers water table around the
well exposing contaminants in vadose
zone, which are accessible to vapor
extraction. Aboveground treatment
for liquid phase and vapor phase (if
necessary).
Can be utilized for both soil
and groundwater remediation.
Wide range of
concentrations can be
removed using air
stripping. Liquid-phase
carbon adsorption as
necessary. Off-gas
treatment using catalytic
oxidation or vapor-phase
carbon (as necessary).
Higher influent flow rates
associated with high permeability
soils. As with SVE, success with
vadose zone treatment depends on
sufficient air permeability for
advective air flow.
Possible iron fouling of
equipment during
aboveground treatment.
Accessibility may present challenges based on
size/type of site (location for system building,
installation of recovery wells, trenching etc.).
Possible problems with noise levels, vapors,
proximity of residents or businesses.
High capital cost; extensive
O&M required; sampling
requirements for discharge
permitting; high electrical
costs.
May be difficult to achieve
cleanup standards without
additional technology.
Cleanup time generally
considered moderate to long
in comparison to other
technologies.
Discharge permitting required
for treated liquid and possibly
air effluents.
Provides hydraulic control.
Not considered appropriate because this technology is
unlikely to achieve cleanup standards in a reasonable
timeframe. If the only goal is hydraulic control and
recovery, pump and treat would be more cost effective,
but still very expensive, than dual phase extraction.
No
Monitored Natural
Attenuation (MNA)
Involves physical, chemical and
biological processes which act to
naturally reduce the mass, toxicity, and
mobility of subsurface contamination
to acceptable levels.
Can be utilized for both soil
and groundwater remediation.
Not applicable to LNAPL
conditions, best for low
dissolved- or adsorbed-
phase concentrations
following source
removal.
Subsurface lithology and
groundwater migration pathways
must be carefully assessed to ensure
extent of contamination is
delineated prior to technology
selection.
Success highly dependent on
site geochemistry. Some
geochemical sampling is
required to determine the
contaminant reduction
processes at the site.
The potential impacts to downgradient receptors must
be evaluated carefully. No significant concerns with
relation to accessibility.
Significantly lower initial cost
than active remediation
methods, but long term
monitoring costs may
outweigh initial cost benefit.
Long timeframe for
remediation compared to
other technologies.
Generally no special
permitting is required.
Typically requires long-term
monitoring. Site
characterization may be more
complex, costly, and time-
consuming. Public
perception may not be
favorable. May be applicable
to all or part of a site. The
technology has the potential
to impact domestic and public
water supplies and surface
water features.
Based on the risk assessment, a more aggressive
approach is warranted to minimize risks and meet cleanup
objectives. However, MNA may be appropriate in
combination with active source area remediation to
address residual impacts.
Possibly
Surfactant Enhanced Aquifer
Remediation
Injection and extraction of surfactant
solution to mobilize VOCs. Extracted
fluids are removed via AFVR.
Appropriate for soil and
groundwater remediation.
Low dissolved phase
VOC concentrations
Low permeability zones may not be
treated effectively. Efficiency
varies greatly depending on ability
to contact resident VOCs.
Numerous volumes of flushing
through low permeability zones.
No significant concerns
noted.
Accessibility needed for installation of injection and
extraction wells. Injectates may pose a health and
safety concern.
Requires extraction
technology via AFVR events Short to moderate timeframe Injection permitting required.
Low recovery during previous
AFVR events could limit the
recovery of surfactant and
flushing effectiveness
Not likely due to geological considerations and low liquid
recovery from aquifer. Surfactant flushing would be not
be effective
No
Further Evaluation
Warranted?Technology Technology Description Potential for Success at Subject Site
TABLE 2
REMEDIAL EVALUATION COST ESTIMATES
Allen Hansen Property
5002 Wake Forest Highway
Durham, Durham County, North Carolina
NCDEQ Incident # 5701
Treatment Area 6,000 sq ft Monitoring Wells 10
Injection Points 19 WSW 3
Injectate 1,500 lbs Schedule Semiannual
Type Controlled released polymer pellets
Permanganate
Injectate $23,000 Remedial Well Installation 44,125.00$
Direct Push/Drilling $51,956 Equipment (new)150,000.00$
Trenching 25,000.00$
O/M $22,000/year x 2 years 44,000.00$
Total $78,231 Total $84,780 TOTAL 263,125.00$
Remediation Costs
RemRx CRP Persulfate $78,231
MNA $84,780
AS/SVE $263,125
Annual Cost $5,652
15 years $84,780
Other costs (reports, NOI, misc)$3,275
Remediation Evaluation Allen Hansen
RemRx CRP Persulfate MNA Air Sparge/Soil Vapor Extraction

10 Air Sparge Wells, 15 Soil Vapor Extraction Wells

FIGURES

2725 E. Millbrook Road, Suite 121
Raleigh, NC 27604
[phone]
SITE TOPOGRAPHIC MAP
PROJECT NO: SLP0570103
DATE: 8/7/2014 REVIEWED BY: GA
ALLEN HANSON SITE
INCIDENT #5701
5002 WAKE FOREST HIGHWAY
DURHAM, NORTH CAROLINA
Quadrangle: Elm City
FIGURE 1
SCALE:
AS SHOWN
SITE
2725 E. Millbrook Road, Suite 121
Raleigh, NC 27604
[phone]
POTENTIAL RECEPTOR MAP
PROJECT NO: SLP0570103
DATE: 7/30/14 REVIEWED BY: KR
ALLEN HANSON SITE
INCIDENT #5701
5002 WAKE FOREST HIGHWAY
DURHAM, NORTH CAROLINA
Quadrangle: Durham County GIS
FIGURE 3
SCALE: 1” = 370’
Active Water Supply Well Location
Inactive Water Supply Well Location
2
SITE
500 feet
1,000 feet
1
2456
8
7
9
10
15
14
13
3
12
11

APPENDIX A

MANN-KENDALL GSI TOOLKITS
Evaluation Date:Job ID:
Facility Name:Constituent:
Conducted By:Concentration Units:ug/L
Sampling Point ID:Benzene Toluene Ethylbenzene Xylenes Naphthalene
Sampling Sampling
Event Date
1 4/4/2011 2600 3000 160 1600 1
2 8/8/2011 6500 15000 1600 10200 130
3 11/1/2011 4300 9000 890 6100 150
4 7/2/2014 7800 5800 1900 6000 670
5 1/27/2015 290 36 56 181 30
6 5/10/2016 1,900 62 1,000 125 1
7 10/12/2016 240 18 55 81 4.1
8 10/10/2017 1.7 1 0.77 3.7 0.53
9 3/14/2018 112 13.0 13.2 69.4 12.9
10 2/19/2019 78.8 118 94.3 318 26.4
11
12
13
14
15
16
17
18
19
20
Coefficient of Variation:1.46 2.14 1.51 2.12 1.73
Mann-Kendall Statistic (S):-25 -21 -19 -21 -7
Confidence Factor:100.0%100.0%99.9%100.0%86.4%
Concentration Trend:Decreasing Decreasing Decreasing Decreasing No Trend
Notes:
1.At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples.
2.Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing;
≥ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S≤0, and COV ≥ 1 = No Trend; < 90% and COV < 1 = Stable.
3.Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales,
Ground Water, 41(3):355-367, 2003.
DISCLAIMER: The GSI Mann-Kendall Toolkit is available "as is". Considerable care has been exercised in preparing this software product; however, no party, including without
limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such
party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in
this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein.
MW-1A CONCENTRATION (ug/L)
GSI Environmental Inc., www.gsi-net.com
GSI MANN-KENDALL TOOLKIT
for Constituent Trend Analysis
12-Mar-19 Incident #5701
Allen Hansen Property MW-1A
ATC Associates of North Carolina, P.C.
0.1
1
10
100
1000
10000
100000
07/09 11/10 04/12 08/13 12/14 05/16 09/17 02/19 06/20Concentration (ug/L)Sampling Date
Benzene
Toluene
Ethylbenzene
Xylenes
Naphthalene
Evaluation Date:Job ID:
Facility Name:Constituent:
Conducted By:Concentration Units:ug/L
Sampling Point ID:Benzene Toluene Ethylbenzene Xylenes Naphthalene
Sampling Sampling
Event Date
1 8/8/2011 1600 4100 710 8500 160
2 11/1/2011 2800 4700 870 8300 350
3 7/2/2014 1100 91 520 420 160
4 1/27/2015 750 49 310 145 44
5 5/10/2016 38 170 1,500 3,500 650
6 10/12/2016 810 74 170 1,120 56
7 10/10/2017 41.8 14.5 23.1 74.9 16.3
8 3/14/2018 8 10.7 30.9 512 10.7
9 2/19/2019 33 4.6 8.7 33.9 7.5
10
11
12
13
14
15
16
17
18
19
20
Coefficient of Variation:1.56 2.27 1.47 1.44 1.29
Mann-Kendall Statistic (S):-20 -26 -26 -28 -18
Confidence Factor:100.0%100.0%100.0%100.0%100.0%
Concentration Trend:Decreasing Decreasing Decreasing Decreasing Decreasing
Notes:
1.At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples.
2.Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing;
≥ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S≤0, and COV ≥ 1 = No Trend; < 90% and COV < 1 = Stable.
3.Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales,
Ground Water, 41(3):355-367, 2003.
DISCLAIMER: The GSI Mann-Kendall Toolkit is available "as is". Considerable care has been exercised in preparing this software product; however, no party, including without
limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such
party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in
this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein.
MW-2 CONCENTRATION (ug/L)
GSI Environmental Inc., www.gsi-net.com
GSI MANN-KENDALL TOOLKIT
for Constituent Trend Analysis
12-Mar-19 Incident #5701
Allen Hansen Property MW-2
ATC Associates of North Carolina, P.C.
1
10
100
1000
10000
11/10 04/12 08/13 12/14 05/16 09/17 02/19 06/20Concentration (ug/L)Sampling Date
Benzene
Toluene
Ethylbenzene
Xylenes
Naphthalene
Evaluation Date:Job ID:
Facility Name:Constituent:
Conducted By:Concentration Units:ug/L
Sampling Point ID:Benzene Toluene Ethylbenzene Xylenes Naphthalene
Sampling Sampling
Event Date
1 8/8/2011 170 300 34 430 6.1
2 11/1/2011 67 92 16 212 1
3 7/2/2014 2200 190 790 870 180
4 1/27/2015 2300 500 710 1020 300
5 5/10/2016 1,300 770 1,300 12,100 650
6 10/12/2016 410 18 95 71 30
7 10/10/2017 92.1 71.2 21.3 251 10.9
8 3/14/2018 11.2 0.58 1 5.6 0.96
9 2/19/2019 349 176 97.6 361 35
10
11
12
13
14
15
16
17
18
19
20
Coefficient of Variation:1.21 1.30 1.98 2.20 0.91
Mann-Kendall Statistic (S):-18 -18 -14 -18 -4
Confidence Factor:100.0%100.0%99.6%100.0%75.8%
Concentration Trend:Decreasing Decreasing Decreasing Decreasing Stable
Notes:
1.At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples.
2.Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing;
≥ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S≤0, and COV ≥ 1 = No Trend; < 90% and COV < 1 = Stable.
3.Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales,
Ground Water, 41(3):355-367, 2003.
DISCLAIMER: The GSI Mann-Kendall Toolkit is available "as is". Considerable care has been exercised in preparing this software product; however, no party, including without
limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such
party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in
this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein.
MW-3 CONCENTRATION (ug/L)
GSI Environmental Inc., www.gsi-net.com
GSI MANN-KENDALL TOOLKIT
for Constituent Trend Analysis
12-Mar-19 Incident #5701
Allen Hansen Property MW-3
ATC Associates of North Carolina, P.C.
0.1
1
10
100
1000
10000
100000
11/10 04/12 08/13 12/14 05/16 09/17 02/19 06/20Concentration (ug/L)Sampling Date
Benzene
Toluene
Ethylbenzene
Xylenes
Naphthalene
Evaluation Date:Job ID:
Facility Name:Constituent:
Conducted By:Concentration Units:ug/L
Sampling Point ID:Benzene Toluene Ethylbenzene Xylenes Naphthalene
Sampling Sampling
Event Date
1 10/12/2016 1,900 3300 810 6,000 270
2 12/24/2016 4200 11000 2000 12500 480
3 10/10/2017 1480 2220 397 3830 186
4 3/14/2018 99.2 940 40.6 3440 14.3
5 2/19/2019 767 889 333 2,140 151
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Coefficient of Variation:0.93 1.15 1.07 0.74 0.78
Mann-Kendall Statistic (S):-6 -8 -6 -8 -6
Confidence Factor:88.3%95.8%88.3%95.8%88.3%
Concentration Trend:Stable Decreasing No Trend Decreasing Stable
Notes:
1.At least four independent sampling events per well are required for calculating the trend. Methodology is valid for 4 to 40 samples.
2.Confidence in Trend = Confidence (in percent) that constituent concentration is increasing (S>0) or decreasing (S<0): >95% = Increasing or Decreasing;
≥ 90% = Probably Increasing or Probably Decreasing; < 90% and S>0 = No Trend; < 90%, S≤0, and COV ≥ 1 = No Trend; < 90% and COV < 1 = Stable.
3.Methodology based on "MAROS: A Decision Support System for Optimizing Monitoring Plans", J.J. Aziz, M. Ling, H.S. Rifai, C.J. Newell, and J.R. Gonzales,
Ground Water, 41(3):355-367, 2003.
DISCLAIMER: The GSI Mann-Kendall Toolkit is available "as is". Considerable care has been exercised in preparing this software product; however, no party, including without
limitation GSI Environmental Inc., makes any representation or warranty regarding the accuracy, correctness, or completeness of the information contained herein, and no such
party shall be liable for any direct, indirect, consequential, incidental or other damages resulting from the use of this product or the information contained herein. Information in
this publication is subject to change without notice. GSI Environmental Inc., disclaims any responsibility or obligation to update the information contained herein.
MW-5 CONCENTRATION (ug/L)
GSI Environmental Inc., www.gsi-net.com
GSI MANN-KENDALL TOOLKIT
for Constituent Trend Analysis
12-Mar-19 Incident #5701
Allen Hansen Property MW-5
ATC Associates of North Carolina, P.C.
1
10
100
1000
10000
100000
08/16 11/16 03/17 06/17 09/17 12/17 04/18 07/18 10/18 02/19 05/19Concentration (ug/L)Sampling Date
Benzene
Toluene
Ethylbenzene
Xylenes
Naphthalene

APPENDIX B

AXNANO PROPOSAL

2901 East Gate City Blvd, Suite 2200 │ Greensboro, NC 27401 │ 540-818-2000
www.remrxremediation.com
1
September 9, 2019

Gabriel Araos, PE
ATC Associates
2725 E. Millbrook Road, Suite 121
Raleigh, NC 27604

RE: Proposal for Groundwater Treatment
Allen Hanson Site
NCDEQ Incident #5701
5002 Wake Forest Highway
Durham, Durham County, NC

Dear Mr. Araos:
Thank you for your interest in RemRx™ CRP Permanganate (Controlled Release Polymer pellets)
for In Situ Chemical Oxidation. The sustained delivery of oxidant from RemRx™ CRP has been
developed to eliminate or greatly reduce the occurrence of contaminant rebounding, ultimately
reducing site remediation cost and time.

Brief Site History
RemRx has reviewed the provided site documents and understands that a release of petroleum
fuel was identified at the subject site in May of 1990 from an underground storage tank (UST) of
unknown size and unknown location which was reportedly abandoned in 1970. A one story
building occupies the site property.
Investigations began in 2011. Fifteen water supply wells were found to be present within 1,000
feet of the site and a surface water body was found approximately 500 feet from the site. In 2012,
943.52 tons of impacted soil were excavated and disposed. During the course of the environmental
investigations, 10 monitoring wells have been installed (MW-1A through MW-10) to date.
Three water supply wells (WSW-2, WSW-3, and WSW-4) were sampled in 2019 and no fuel
constituents were detected above laboratory reporting limits. Municipal water is available to
properties along and immediately off Highway 98, Oak Grove Parkway, and Sherron Road.
Groundwater elevations measured in site monitoring wells indicate that groundwater flows to the
west; however, contaminant plume geometry indicates that groundwater flow is to the southwest.
Contaminants detected above NC 2L Groundwater Quality Standards include benzene; toluene;
xylenes; naphthalene; 1,2-dibromoethane; 1,2-dichloroethane; 1,2,3-trichloropropane; 1,2,4-
trimethylbenzene; and vinyl chloride. Previous groundwater remediation efforts have included
oxygen release socks and aggressive fluid vapor recovery (AFVR).
Allen Hanson Site
NCDEQ Incident #5701
2901 East Gate City Blvd, Suite 2200 │ Greensboro, NC 27401 │ 540-818-2000
www.remrxremediation.com
2

Remedial Approach
RemRx believes that in-situ chemical oxidation (ISCO) of the fuel related compounds present at
the site using RemRx™ CRP Persulfate is a sustainable and method to treat groundwater at the
site. Upon contact with benzene and fuel related compounds, persulfate will rapidly mineralize the
compounds to carbon dioxide; unlike aerobic biostimulation methods which may take years to
decades to reduce contaminant concentrations.
After a thorough review of the site documents provided, RemRx proposes the emplacement of
RemRx™ CRP Persulfate within nine CRP treatment wells and ten CRP treatment borings to reduce
contaminant concentrations in groundwater at the site. The attached Figure 1 depicts the proposed
locations of the proposed treatment wells and treatment borings.
The proposed CRP treatment wells will be constructed using 4-inch diameter schedule 40 polyvinyl
chloride (PVC) with a 20-foot PVC screened interval. The top of the screened interval will
correspond to the water table. Within each well, a fine mesh sleeve will be lowered in to the well.
Once in place the sleeve will be filled with approximately 75 lbs of CRP Persulfate. An approximate
total of 675 lbs of CRP Persulfate is proposed for the initial treatment within the nine CRP treatment
wells. In the event additional treatments are required, the spent CRP can be easily removed from
the wells and disposed as required, and reapplied if necessary.
RemRx understands that permanent injection wells are not feasible in the areas of monitoring wells
MW-1A and MW-3. Therefore, RemRx proposes the placement of CRP within ten CRP treatment
borings. The proposed CRP treatment borings will be advanced by a conventional drill rig capable
of advancing a 6-inch diameter borehole. The CRP treatment boring would be advanced to a depth
corresponding to approximately 15 feet below the water table. Once at depth, drilling tooling will
be removed from the boring and CRP will be backfilled up to the water table. RemRx estimates
that 82.5 lbs of CRP will be placed in to each CRP treatment boring, totaling 825 lbs of CRP within
the ten treatment borings.

Budgetary Costs
RemRx has prepared budgetary pricing for the CRP Persulfate material and freight. RemRx will
also provide a technician to assist with the initial deployment.
Unit Rate Estimated Units Estimated Unit Cost
Oxidant Demand Determination $200 1 No Charge
CRP Persulfate $15/ Pound 1,500 lb $22,500
Mesh Sleeve No Charge
Shipping Flat Rate for 1500 lbs 1 $500
On Site Technical Support No Charge
Estimated Treatment Area 1 RemRx™ CRP Persulfate Costs $23,000

Allen Hanson Site
NCDEQ Incident #5701
2901 East Gate City Blvd, Suite 2200 │ Greensboro, NC 27401 │ 540-818-2000
www.remrxremediation.com
3

Limitations
RemRx believes that the proposed CRP application described above will significantly reduce
concentrations of dissolved fuel constituents at this site.
Based on RemRx’s review of available documents, the vertical extent of groundwater at the site
has not been fully delineated. This remedial approach does not address potential deeper
groundwater impacts at the site. This remedial approach also assumes that underground and
aboveground utilities will not be present in the remedial areas.
Results depend on specific site conditions, please discuss your site with a RemRx™ Technical
Manager. The information provided is for guidance only. It is recommended that a treatability study
be performed to verify applicability to your specific contaminant and site conditions. RemRx™
makes no warranty or representation, expressed or inferred, and nothing herein should be
construed as to guaranteeing actual results in field use, or permission or recommendation to
infringe any patent.
RemRx appreciates the opportunity to review this project and offer our recommended remedial
approach for this site. We look forward to discussing this project in more detail with you in the
near future.

Sincerely,

Alexis Carpenter, PhD Jeff Albano, PG
Scientist RemRx™ Consultant
540-818-2000
[e-mail]
Allen Hanson Property –Incident #5701
5002 Wake Forest Highway
Durham, North Carolina
Figure 1. Proposed CRP Treatment Well Location Map
2901 East Gate City Blvd, Suite 2200
Greensboro NC 27401
336-217-5171
Proposed 4-Inch CRP Treatment Well
Note: Figure modified from ATC’s Figure 5 Dated 3/7/19
Benzene Concentration (µg/l)
Benzene Isoconcentration Contour
(Dashed Where Inferred)
(11.2)
Proposed 6-Inch CRP Treatment Boring