NC0003573_Appendix G - DEQ Email Communication & GWTP Engineering Report_20210921

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Appendix G
DEQ E-mail Communication
Engineering Report —Treatment of Groundwater
and Upgradient Seeps Water
TR0795
Aug-2021

Subject: RE: Re: Seeps and GW NPDES Permit Application (Outfall 004)
From: Fields, Dianne L <[e-mail]>
Sent: Thursday, August 12, 2021 11:21 AM
To: Grzyb, Julie; Chernikov, Sergei
Cc: Garon, Kevin P; Ruiter, J. B; Compton, Christel E
Subject: Re: Seeps and GW NPDES Permit Application (Outfall 004)
Julie and Sergei,
I am writing to provide you minor update on the flows specified in our Chemours Fayetteville Works NPDES Permit Application for the Groundwater Treatment
System (submitted as Outfall 004 on June 13, 2021). In the application, the total average flow on Form 2D was 1.756 mgd (1,219 gallons per minute). We are
maintaining a treatment system flow rate design of 1,500 gallons per minutes but have refined the anticipated flowrate of extracted black creek aquifer
groundwater from a total of 800 gallons per minute to 830 gallons per minute as shown in the table below. We are therefore requesting that NCDEQ provide a
permit based on this new flowrate.
Water Source
Approximate Flow Rate
Seeps A and B Baseflow°
161 gpm
Seeps A and B Stormflow*
108 gpm
Groundwater from Surficial Aquifer°
150 gpm
Groundwater from Black Creek Aquifer
830 gpm
Total Flow
1,249 gpm
* Seeps stonnflow represents maximum increase over baseflow averaged over 24-hour period.
0 Seeps baseflow and Shallow Groundwater may include some double counting. Seeps baseflow represents the 95th
percentile instantaneous flow from each of Seeps A and B at location representative of the remedy capture location.
If you need amended documents, please let us know.
Respectfully,
1

Dianne
Dianne L Fields
Sr. Environmental Consultant
910-678-1384 office
919-628-8055 mobile
The Chemours Company
Fayetteville Works Plant
22828 NC Hwy 87 West
Fayetteville, NC 28306
Chemours-
< style=">
This communication is for use by the intended recipient and contains information that may be privileged, confidential or copyrighted under applicable law. If you
are not the intended recipient, you are hereby formally notified that any use, copying or distribution of this e-mail, in whole or in part, is strictly prohibited.
Please notify the sender by return e-mail and delete this e-mail from your system. Unless explicitly and conspicuously designated as "E-Contract Intended", this
e-mail does not constitute a contract offer, a contract amendment, or an acceptance of a contract offer. This e-mail does not constitute a consent to the use of
sender's contact information for direct marketing purposes or for transfers of data to third parties.
https://www.chemours.com/en/email-disclaimer
2

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ENGINEERING REPORT -
TREATMENT OF GROUNDWATER
AND UPGRADIENT SEEPS WATER
Prepared for
The Chemours Company FC, LLC
1007 Market Street
PO Box 2047
Wilmington, DE 19899
Prepared by
Geosyntec Consultants of NC, P.C.
2501 Blue Ridge Road, Suite 430
Raleigh, NC 27607
Geosyntec Project Number TR0795
June 2021

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TABLE OF CONTENTS
1. INTRODUCTION AND BACKGROUND 5
1.1 Site History and Overview 5
1.2 Process Overview 6
2. DESIGN BASIS 8
2.1 Aquifer Location 8
2.2 Influent Water Quality 10
2.3 Groundwater and Seeps Outfall 13
2.4 Influent Untreated Water Quality — Comparison to Water Quality Criterial3
2.5 Pilot Studies 15
2.6 Pumping & Conveyance Design 15
3. PROPOSED TREATMENT DESIGN 16
3.1 Overall Narrative 16
3.2 Individual Unit Operations 19
3.2.1 Metals Oxidation 19
3.2.2 Filtration 19
3.2.3 Granular Activated Carbon Adsorption 19
3.2.4 Solids Handling and Dewatering 20
3.3 Operability and Maintenance Considerations 20
3.4 Process Monitoring 21
4. SUMMARY 21
5. REFERENCES 21
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LIST OF TABLES
Table 1: Hydraulic Loading of Representative Groundwater and Seep Sources
Table 2: Representative Well and Seep Locations and Estimated Flowrates
Table 3: Influent Design Basis for the Groundwater Treatment System
LIST OF FIGURES
Figure 1: Remedy Alignment and Proposed Groundwater Treatment System Location
Figure 2: Groundwater Flow Direction and Seep Locations
Figure 3: Comparison of Carbon Isotherms for Heptachlor Epoxide, Two PAHs, and HFPO-
DA
Figure 4: Conceptual Process Flow Diagram of Primary Treatment Train and Solids Recovery
Process
LIST OF APPENDICES
Appendix A: Analytical Data for Groundwater & Seep Sources for the Engineering Design
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ACRONYMS AND ABBREVIATIONS
BCA Black Creek Aquifer
CO Consent Order
GAC granular activated carbon
GPM gallons per minute
GWTS groundwater treatment system
HDPE high density polyethylene
HFPO-DA hexafluoropropylene oxide-dimer acid
HRT hydraulic retention time
mg/L milligrams per liter
MTZ mass transfer zone
NCDEQ North Carolina Department of Environmental Quality
ND Non -detect
NPDES National Pollutant Discharge Elimination System
PAH polycyclic aromatic hydrocarbons
PFAS per- and polyfluoroalkyl substances
PFMOAA perfluoro- 1 -methoxyacetic acid
PMPA perfluoro-2-methoxypropanoic acid
STD standard
TSS total suspended solids
ug/L micrograms per liter
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1. INTRODUCTION AND BACKGROUND
This Engineering Report was prepared by Geosyntec Consultants of NC, P.C.
(Geosyntec) for the Chemours Company FC, LLC (Chemours) to provide a description
of the future treatment works to be installed for the collection and treatment of
groundwater and surface water from locations along the proposed groundwater remedy
alignment at the Chemours Fayetteville Works, North Carolina site (the Site). The
groundwater remedy includes a barrier wall, water extraction network, and treatment
system (Groundwater Treatment System or GWTS) is a requirement of the Addendum to
the Consent Order paragraph 12 (CO Addendum) amongst Chemours, the North Carolina
Department of Environmental Quality (NCDEQ), and Cape Fear River Watch entered by
the court on October 12, 2020.
The goal of the GWTS is to achieve a removal efficiency of 99%, as measured by
indicator parameters hexafluoropropylene oxide-dimer acid (HFPO-DA), perfluoro-2-
methoxypropanoic acid (PMPA), and perfluoro-1-methoxyacetic acid (PFMOAA). The
remedy is to commence operation by March 15, 2023 per paragraph 3(b) of the
Addendum to the CO. To meet this requirement, Chemours intends to complete
construction of the GWTS by April 1, 2022. Chemours will need to pump and treat the
water collected by the remedy to protect the barrier wall's structural integrity. The GWTS
therefore needs to be operational prior to the remedy's construction in June 2022.
This document provides the conceptual design and engineering assumptions for the
GWTS, in accordance with the National Pollutant Discharge Elimination System
(NPDES) permit application requirements. The permit application requires that
Chemours identify effluent characteristics of those parameters identified in the EPA
Application Form 2D New Manufacturing, Commercial, Mining, and Silvicultural
Operations That Have Not Yet Commenced Discharge of Process Wastewater (EPA Form
2D).
1.1 Site History and Overview
The Site is located on NC Highway 87, 15 miles southeast of the City of Fayetteville, and
south of the Bladen-Cumberland County line. The Site encompasses 2,177 acres of
relatively flat undeveloped open land and sloping woodland bounded on the east by the
Cape Fear River, on the west by NC Highway 87, and on the north and south by farmland.
The ground on which the Site is situated slopes East towards the Cape Fear River. The
proposed treatment facility is to be located on the southeastern portion of the Site just
north of the William O. Huske Lock & Dam.
E.I. du Pont de Nemours and Company (DuPont) purchased the property in parcels from
several families in 1970. The Site's first manufacturing area was constructed in the early
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1970s. Currently, the Site manufactures plastic sheeting, fluorochemicals, and
intermediates for plastics manufacturing. A former manufacturing area, which was sold
in 1992, produced nylon strapping and elastomeric tape.
DuPont sold its Butacite® and SentryGlas® manufacturing units to Kuraray America,
Inc. in June 2014; these are now a tenant operation. In July 2015, DuPont separated its
specialty chemicals business into a new publicly traded company named The Chemours
Company FC, LLC. With this separation, Chemours became the owner of the entire 2,177
acres of the Fayetteville Works along with the Fluoromonomers, Nafion® membranes,
and Polymer Processing Aid (PPA) manufacturing units. The polyvinyl fluoride (PVF)
resin manufacturing unit remained with DuPont as a tenant operation.
In addition to the manufacturing operations, Chemours operates two natural gas -fired
boilers and a biological wastewater treatment plant for the treatment of DuPont and
Kuraray process wastewater and sanitary wastewaters from DuPont, Kuraray, and
Chemours.
1.2 Process Overview
Groundwater at the Site currently flows east towards the Cape Fear River. The extraction
and conveyance portion of the treatment design proposes to capture the groundwater flow
via the installation of a network of groundwater extraction wells and to capture the
baseflow of seeps originating upgradient of the remedy and flows during rainfalls up to
0.5 inches in depth. The extracted groundwater and seeps water will then be collected and
conveyed to be treated by the GWTS which is proposed to be located in the southeast
corner of the Site. The proposed location is shown in Figure 1.
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Proposed
new GWTS
location
Legend
S Extraction well
- Planned groundwater remedy route
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Figure 1: Remedy Alignment and Proposed Groundwater Treatment System Location
The GWTS will be comprised of a series of chemical and physical separation steps.
Chemical oxidation and pH adjustment will first be employed to precipitate metals, such
as iron, to prevent downstream contamination or fouling of the granulated activated
carbon (GAC) media. The precipitated metals and other particles above an appropriate
control threshold will be removed via ultrafiltration membranes or some other suitable
separation technology. The filtered effluent will then be treated for per- and
polyfluoroalkyl substances (PFAS) by GAC adsorption. The reject from the filtration and
GAC systems will undergo dewatering through a thickening tank and filter press or
centrifugation, from which the sludge cake will be disposed of offsite and the press water
will be recycled to the influent of the thickening tanks. Periodic backwashing will extend
membrane and carbon media life, and the carbon will be removed and replaced based on
breakthrough monitoring of several three -vessel carbon trains in a lead -middle -lag
arrangement. Associated design elements such as pumps, piping, electrical,
instrumentation and control for interlocks, mechanical and civil/structural elements will
be finalized during the detailed design phase. This design concept may be optimized
based on ongoing benchtop studies and data acquisition.
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2. DESIGN BASIS
2.1 Aquifer Location
The ground on which the Site is situated slopes east from the facility towards the Cape
Fear River. The main groundwater aquifers therefore also flow towards the Cape Fear
River. Furthermore, there are four seeps that also contribute surface water flow to the
Cape Fear River, as identified in Figure 2.
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Proposed groundwater remedy alignment
Seep
Nearby tributary to river
General direction of groundwater flow
Site boundary
Figure 2. Groundwater Flow Direction and Seep Locations
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The groundwater originates from two main aquifers, known as the Black Creek Aquifer
(BCA) and the Surficial Aquifer. These two zones are separated by the Black Creek
Confining Unit along most of the length of the proposed groundwater remedy alignment,
and the BCA is underlain by the Upper Cape Fear Confining unit, which is a layer of
competent clay.
The groundwater daylights near the Cape Fear riverbank as various seeps. There are four
seeps (Seeps A through D), although only two of these are major hydraulic contributors
(A and B) which will require collection for treatment. The estimated hydraulic loading in
gallons per minute (gpm) from the two aquifers and four seeps, post remedy construction,
is shown in Table 1.
Table 1: Hydraulic Loading of Representative Groundwater and Seep Sources
Water Source
Approximate Flow Rate
0
Seeps Baseflow
161 gpm
*
Seeps Stormflow
108 gpm
°
Groundwater from Surficial Aquifer
150 gpm
Groundwater from Black Creek Aquifer
800 gpm
Total Flow
1,219 gpm
* Seeps stormflow represents maximum increase over baseflow averaged over 24-hour period.
0 Seeps baseflow and Shallow Groundwater may include some double counting. Seeps baseflow represents the 95th
percentile instantaneous flow from each of Seeps A and B at location representative of the remedy capture location.
Actual flows may vary from these model results due to variability in rainfall. The largest
rainfall effect is expected to be seen in the seeps stormflow parameter in Table 1; the cited
108 gpm value is the 24-hour average flow for a 0.5 inch storm event. The seeps' baseflow
quantity is also a conservative estimate (i.e. high -end). For this reason, the extraction
system and the GWTS will be designed to handle reasonable expected flow variations
and the GWTS currently has a planned capacity safety factor such that a maximum design
flow of 1,500 gpm has been selected.
2.2 Influent Water Quality
The source water to the GWTS will be the extracted groundwater and captured seep
water. The groundwater will be extracted from a series of approximately 60 extraction
wells installed along the length of the proposed groundwater remedy alignment. Water
will also be captured from seeps originating upgradient of the barrier wall (Seeps A and
B). Since the GWTS has not yet been installed, the influent water quality presented in
this report is from representative wells in the associated aquifers and the seeps. The
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currently available non-PFAS analytical data from the individual untreated groundwater
and seep sources, or their closest analogs, has been collected and is summarized in the
memorandum Chemours Fayetteville Works — Groundwater and Seeps Water Quality
Assessment (Geosyntec, 2021). Relevant analytical data for the engineering design,
including the PFAS data, is provided in Appendix A.
Groundwater sampling was completed at four representative groundwater wells and three
seep locations. The seep locations are shown relative to the site in Figure 2. The
groundwater wells are analogs for the various groundwater sources to be collected by the
new extraction network along the groundwater remedy alignment, as described in Table
2. Two of the seep locations (Seep A at Wall Point and Seep B at Wall Point) are analogs
for the seep baseflow and surface runoff that will be intercepted by the groundwater
remedy. The samples collected at the location Seep A minor tributary are not analogs of
seep water as the location was artificially disturbed prior to sample collection to introduce
sediment into the sample. The results from Seep A minor tributary were, however,
included in the engineering design as a safety factor.
Table 2: Representative Well and Seep Locations and Estimated Flowrates
Representative Water
Location Tag
Flowrate
(gpd)
Flowrate
(gpm)
Proportion
/0)
Black Creek Aquifer at North
EW-1
668,794
464
47%
Black Creek Aquifer at South
EW-3
428,198
297
30%
Surficial Aquifer at North
PIW-5S
104,760
73
7%
Surficial Aquifer at South
PIW-10S
75,773
53
5%
Seep A minor tributary*
SEEPA-TR-N
31,522
22
2%
Seep A at Wall Point
SEEP -A -WALL
50,501
35
4%
Seep B at Wall Point
SEEP-B-WALL
67,133
47
5%
* Samples were artificially disturbed at SEEP-A-TR-N prior to collection to introduce turbidity.
The dataset used for the GWTS design is inclusive of untreated water data collected
during sampling events from 2019 and 2020 and a series of 11 sampling events that
occurred during March and April 2021. PFAS compounds were specifically sampled for
on March 3, March 26 and April 28, 2021. Appendix A provides a detailed overview of
the average, maximum, and minimum concentrations of all untreated water parameters
sampled for treatment design. The water collected at these wells (EW-1, EW-3, PIW-5S
and PIW-10S) and two seep locations (SEEP -A -WALL and SEEP-B-WALL) is assumed
to be representative of the total groundwater and seep flow that will be extracted and
treated by the GWTS.
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In addition to PFAS analyses, a variety of supporting analytes such as total suspended
solids (TSS), and metals (such as aluminum and iron) were sampled as they were
considered key parameters of concern that would inform the pre-treatment system
upstream of the PFAS removal stage. Flow -weighted composite concentrations for each
parameter were developed for each of the groundwater and surface water groupings, as a
design aid for the development of the influent design basis. The average, minimum and
maximum mass loading of each untreated water parameter and Table 3+ compound was
estimated using the average, minimum, and maximum concentrations from the analytical
data and the flow rates in Table 1. Thus, the flow -weighted, mass -based composition for
the untreated water groundwater sources was estimated by summing the mass loadings
from PIW-5S, PIW-10S, EW-1, and EW-3. The flow -weighted average composition for
the seeps was estimated by summing the mass loadings from SEEP -A -WALL, SEEP-B-
WALL, and SEEP-A-TRN.
The projected concentrations in the combined influent to the GWTS were estimated from
the flow -weighted concentrations groundwater and surface water groupings. Upon
construction completion of the groundwater remedy, it is estimated that the total dry -
weather groundwater and surface water flows will be 950 gpm and 161 gpm, respectively.
The groundwater and surface water groupings were combined by flow -weighting the
average, minimum, and maximum concentrations using these estimated post -construction
flows. The design of the GWTS is based on the contaminant profile in Table 3.
Table 3: Influent Design Basis for the Groundwater Treatment System
Constituent
Units
Projected Concentrations
Influent Design
Basis
Avg.
Min.
Max.
Min.
Max.
HFPO Dimer
Acid
ug/L
12.2
8.22
18.9
4.11
28.3
PFMOAA
ug/L
64.3
17.5
192
8.73
288
PMPA
ug/L
13.2
8.38
22.5
4.19
33.8
Total table 3+
(20 compounds)
ug/L
139
54.9
352
27.4
528
Aluminum, total
mg/L
1.52
1.16
2.20
0.58
3.30
Bromide
mg/L
ND
ND
ND
ND
ND
Calcium, total
mg/L
4.07
3.74
4.55
1.87
6.82
Carbonate
Alkalinity
mg/L
ND
ND
ND
ND
ND
Chloride, total'
mg/L
8.30
4.85
11.6
2.42
17.4
Fluoride, total
mg/L
0.11
0.11
0.11
0.06
0.17
Hardness
mg/L
ND
ND
ND
ND
ND
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Constituent
Units
Projected Concentrations
Influent Design
Basis
Avg.
Min.
Max.
Min.
Max.
Iron, total
mg/L
4.86
2.28
8.56
1.14
12.8
Magnesium,
total
mg/L
2.37
2.27
2.53
1.13
3.80
Manganese,
total
mg/L
0.08
0.06
0.15
0.03
0.23
pH
Std units
6.61
6.50
6.80
6.5
8.5
Phosphate
mg/L
ND
ND
ND
ND
ND
Sulfate (as SO4)
mg/L
24.7
13.3
33.9
6.66
50.9
Total Dissolved
Solids
mg/L
78.5
66.8
93.3
33.4
140
Total Organic
Carbon
mg/L
1.11
0.57
2.01
0.29
3.01
TSS2
mg/L
59.2
38.4
120
19.2
180
SEEP -A -WALL and SEEP-B-WALL each had one observation above 30,000 milligrams per liter (mg/L) chloride.
Data has been excluded and can be considered an outlier for the basis of design.
2 Potentially 250 mg/L during peak storm events (see below). This also does not include the total suspended solids
(TSS) contribution from solids generated during pretreatment.
2.3 Groundwater and Seeps Outfall
The treated groundwater and seeps water will be discharged to the Chemours Fayetteville
Site Outfall 002 discharge line to the Cape Fear River. The average flow rate from the
Outfall 002 is 18.025 million gallons per day. The water quality assessment accounted
for the combination of loads from Outfalls 004 and 002. In addition, the water quality
assessment accounted for the mixing zone analysis that was conducted for Outfall 002
that documented a river dilution of 8:1 (Geosyntec, 2019).
2.4 Influent Untreated Water Quality - Comparison to Water Quality Criteria
The groundwater and seep data for non-PFAS compounds were compared to North
Carolina's surface water quality criteria. This screening -level exercise was conservative
as no treatment was assumed. Results are documented in a memorandum - Chemours
Fayetteville Works - Groundwater and Seeps Water Quality Assessment (Geosyntec,
2021). After flow -weighting the groundwater and seeps' concentrations, incorporating
the load from Outfall 002, and applying an 8:1 dilution from the Outfall 002 mixing zone,
heptachlor epoxide and polycyclic aromatic hydrocarbons (PAHs) warrant consideration
as additional pollutants targeted for removal by the GWTS.
Heptachlor epoxide was only detected in one well (PIW-5S) and one seep (SEEP -A -
WALL) at low levels. The PAH compounds were only detected at low levels in one (PIW-
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5S) of the six untreated groundwater and seep sources. As detailed in the Groundwater
and Seeps Water Quality Assessment (Geosyntec, 2021), Chemours will be resampling
these locations to confirm the presence of these compounds.
However, if these compounds are occasionally present in the influent to the GWTS it is
unlikely that they will pass -through the GWTS. Heptachlor epoxide is extremely well
adsorbed by activated carbon due to its size, double bonds, and the presence of chlorine
atoms in the structure. PAHs tend to have strong sorptive interactions with carbon due to
their hydrophobic nature and size. Activated carbon itself is composed largely of
graphene plates, and this molecular similarity strengthens the binding energies via t-7c
dispersive forces. A thorough review of the use of activated carbon (as well as other
adsorbents) for removal of PAHs from water can be found in Chemosphere 148 (2016),
336-353. A number of other literature sources are also available that include adsorption
equibria (i.e. isotherms), kinetics, and the combined effects in traditional packed bed
adsorbers which give rise to dynamic capacities for various PAHs on activated carbons.
Loading mg/g
TR0795
Sorption of Various Organic Compounds on Activated Carbon
- Weptech Ior epoxide
- Ben zo k} fl u ora nth en
- Benno; b jfl uo ra nthe the
HFPO-OA
100 -
10 -
1
a.nnm
C_0t
n. I
Concentration, ni /L
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Figure 3: Comparison of Carbon Isotherms for Heptachlor Epoxide, two PHAs, and
HFPO-DA. Data from "Carbon Adsorption Isotherms for Toxic Organics" (EPA-
600/8-80-023, April 1980).
The PFAS compounds this system is designed to treat adsorb to carbon more weakly than
PAHs, as shown in Figure 3. Additionally, they are present in the water at concentrations
roughly two orders of magnitude higher than the PAHs (and roughly four orders of
magnitude higher than the heptachlor epoxide) that may be present in the intake water.
As this treatment system will be run to prevent breakthrough of the three indicator PFAS,
it is expected that heptachlor epoxide and the PAHs will be readily sorbed by the GAC
and therefore are not expected to cause or contribute to exceedances of water quality
criteria in the Cape Fear River if present in the wastewater.
2.5 Pilot Studies
Pilot studies have been completed by vendors to verify the effectiveness of their proposed
pretreatment methods and confirm performance of their selected carbon media to remove
the required constituents and loadings from representative feed water. Tests were
performed using bulk water collected from the sources in Table 2, which was
proportionally blended based on collected flow contribution. The vendors were also
furnished influent water quality data for each source. These pilot studies are being used
to inform the efficacy of proposed full-scale treatment design, including pretreatment
dosing chemistry and residuals characterization (for solids separation and solids -handling
designs).
2.6 Pumping & Conveyance Design
Groundwater modeling remedy development presently indicates a total of approximately
50 new BCA and extraction wells and 10 surficial aquifer extraction wells will be required
to intercept groundwater. The combined maximum total flow rate produced from these
wells is expected to be approximately 950 gpm.
Each well pump is expected to extract approximately 5 to 30 gpm and will be sized to
have additional flow capacity for contingency. The extraction wells are currently planned
as high -density polyethylene (HDPE) construction below finished grade, whereas the
wellhead will be of polyvinyl chloride construction.
Each wellhead will then tee into their corresponding conveyance line (i.e., North or South
Force mains), constructed of HDPE. Approximately two thirds of the required extraction
wells will convey groundwater through the North Force main while the remaining third
is conveyed via the South Force main. The conveyance lines will be sized to
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accommodate the total collected flow of the extraction with added contingency to allow
for increased extraction rates if required. Extracted groundwater will be conveyed to a
surge tank prior to being treated by the GWTS.
The seep flow will be impounded at or near seep capture locations (impoundment storage)
to provide equalization storage during rainfall events and remove readily
settleable/suspended solids prior to being conveyed to a break tank and treated by the
GWTS.
The total maximum dry weather flow to the GWTS after the groundwater remedy is fully
operational, including seep flow, is estimated to be 1,111 gpm. Total flow over a 24-hour
period with rainfall is estimated to average 1,219 gpm (see Table 1). The design flow rate
for the GWTS was selected to be 1,500 gpm to allow for increased groundwater extraction
from the extraction wells and potential uncertainty in post -installation flow behavior from
the seeps.
At the break tank, the influents from the extracted groundwater and the seeps will be
combined. The effluent of the tank will then be drawn on demand by the GWTS. The
impoundment storage will be dredged periodically, and solids characterized and disposed
of at an appropriately designated facility.
3. PROPOSED TREATMENT DESIGN
3.1 Overall Narrative
Based on turnkey vendor proposals currently under consideration, the GWTS is assumed
to be comprised of the following series of treatment units:
1. Metals oxidation;
2. Ultrafiltration (UF) or similar solids separation technology;
3. Granular Activated Carbon (GAC) adsorption;
4. Solids Handling & Dewatering; and
5. Ancillary processes for backwashing and residuals handling.
The influent oxidation system will be designed to help ensure complete oxidation of
reduced iron species (or other dissolved metals), by means of pH adjustment and possible
addition of inorganic coagulant and/or flocculant. Following oxidation, flow will proceed
to the solids separation unit in which particle sizes above an appropriate control threshold
will be removed. The filtrate will then be pumped to the GAC adsorption process, which
will remove the PFAS and other contaminants from the water. Influent flow to the carbon
beds may be pH adjusted to improve treatment performance. The GAC effluent will
undergo further pH adjustment back to near -neutral conditions and then be discharged to
the Cape Fear River via the pipe that conveys existing flows from Outfall 002 to the river.
TR0795 16 June 2021

Geosyntee °
consultants
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NC 1-i,oi Nu: C-35flO onJ C-295
The solids separation unit reject, solids separation unit cleaning, and GAC backwash
water will collect in one or more thickener tanks. The thickened solids will be dewatered
using a filter press or centrifuge. Sludge cake will be transferred into hoppers that will be
trucked off -site for disposal at a permitted waste disposal facility. The dewatering filtrate
will be returned to the head of the plant and blended with the influent downstream of the
oxidation tanks. A backwash water tank will store a limited volume of treated water to
supply GAC backwash, polymer dilution, and other process water requirements. A GAC
backwash waste tank will collect backwash water and bleed it back into the treatment
process downstream of the oxidation tanks. Process design considerations for each unit
operation are further described in Section 3.2.
Based on vendor experience, Chemours' current operational experience at Outfall 003
elsewhere at the facility, and outcomes of past treatability pilot studies, it is anticipated
that a treatment design consisting of these elements will successfully address treatment
requirements. In addition, Chemours is currently performing treatability studies based on
anticipated wastewater characteristics of the groundwater and seeps.
A conceptual process flow diagram (PFD) of the GWTS and the associated sludge
handling system is shown in Figure 4.
TR0795 17 June 2021

TR0795
Geosyntec
consultants
Georynt“Canud1onts ofNC, P.C.
NC L.IctiM, Nu; 4.. end G-295
Feed
a
■
Frac tank
Frac tank
Caustic
Chlorine
Coagulant
Anionic
polymer
Decant
Anionic polymer
OF
Vessel
OF
Vessel.
OF
Vessel
iJF
I _
Vessel jl�*
OF
Vessel
Cone
Bottom
Tank
H2SO4
pH to 3-5
Frac tank
Frac tank
CIP
Caustic
St35
12' diameter vessels
GAG
GAG
GAC
GAC
GAC
GAG
GAG
GAG
GAG
Caustic
pH to 6-9
OF Reject
Sludge
T
Cone
Bottom
Tank
Decant
Frac tan
Filtrate
Cationic polymer
Filter
Press
Solids
■
Soilds roll -off
Frac tank
4
To Outfall
Frac tank
To GAC BiW,
Rinse, Sluice
GAC
— Backwash
Out
GAC System
Solids handling
Pre- and post- treatment
Figure 4: Conceptual Process Flow Diagram of Primary Treatment Train and Solids Recovery Process System
18
June 2021

Geosyntee °
consultants
GrusymccCmisidimi<x ofNC. RC.
NC 1-i,oi Nu: C-3500 mt.' C-295
3.2 Individual Unit Operations
3.2.1 Metals Oxidation
One or more influent oxidation retention tanks will be selected to allow for a hydraulic
retention time (HRT) of 30 minutes at the design flow of 1,500 gpm. The HRT has been
selected to achieve the optimal pH range of 6.5 to 7.5 and allow for the oxidation and
coagulation of ferrous iron (Fe2+) to the less soluble ferric iron (Fe3+). Multiple tanks may
be configured in a duty, active -standby configuration, with the capability to take one or
more tanks offline for maintenance and still process the total plant flow of 1,500 gpm.
Upstream of the tanks, chemical augmentation via an inorganic coagulant, sodium
hydroxide, and sodium hypochlorite will be performed to adjust the pH, limit biofouling,
and promote metals coagulation in the retention tanks. pH adjustment chemicals (sodium
hydroxide and sulfuric acid) will be added to reach the target pH based on feedback from
one or more pH probes.
3.2.2 Filtration
Effluent from the oxidation process is pumped to the solids separation operation, via two
or more pumps in duty -standby configuration.
Ultrafiltration membranes or a similar solids separation process will be used to remove
fine solids and turbidity down an appropriate control threshold upstream of the GAC beds
to prevent fouling and extend runtimes between carbon backwashes or media
replacement. The currently proposed OF system will be comprised of parallel banks of
submerged membranes, provided as a prefabricated system, including the vessels,
influent, effluent and backwash manifolds, automatic open/close valves, and any other
ancillary equipment required.
The filtered effluent from the solids separation process will be directed to a pH adjustment
tank where sulfuric acid can be dosed to lower the pH to approximately 3.5 prior to being
transferred to the GAC system. This pH adjustment is expected to improve GAC
performance and extend service life. The reject and backwash from the solids separation
process will routed to the sludge handling system to be dewatered prior to disposal.
3.2.3 Granular Activated Carbon Adsorption
PFAS removal will be accomplished using GAC adsorption. Filtered effluent will be
pumped from the pH adjustment tank to the GAC system and will enter three GAC
adsorption trains, each designed to treat one third of the design flow (500 gpm). Each
vessel will be configured as a down -flow process where water enters the top of the
adsorber and exits through the bottom. In this configuration, adsorption of contaminants
TR0795 19 June 2021

Geosyntee °
consultants
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NC 1-i,oi Nu: C-35flO onJ C-295
(i.e., PFAS) will begin in the upper portion of the GAC bed. The mass transfer zone
(MTZ) will move from the top of the bed downwards as each portion of the bed becomes
saturated with the contaminants. Eventually, breakthrough will occur wherein the effluent
of the tower contains the contaminant. Multiple carbon adsorbers will be arranged in
series to capture the breakthrough.
A three -column, lead/middle/lag, configuration per train is proposed for the GWTS. It is
assumed that complete saturation of the lead column will occur prior to the initiation of a
carbon changeout. During routine operation the lead column will act as the primary
contaminant remover. The MTZ will travel from the top of the bed to the bottom until
breakthrough of a contaminant of concern occurs. The spent GAC in the lead column will
then be replaced with new GAC and the previous lead column will be placed in the lag
column position. The expired GAC will be shipped offsite for disposal and if appropriate,
regeneration of the carbon. The previous middle column will then become the lead
column and the previous lag/third position column will become the second position
column. It is expected that this operating the system in this manner will result in
significant operations and maintenance savings without compromising removal
efficiencies.
Preliminary sizing for this application indicates that a series of 12-foot diameter vessels
that can hold 20,000 pounds of carbon each will provide for the required hydraulic
loading rate and Empty Bed Contact Time for PFAS removal.
Effluent from the GAC trains will be transferred to a storage tank, where caustic will be
dosed to the effluent upstream of the tank to adjust the pH back to neutral prior to
discharge. This tank is sized to provide an appropriate retention time for the pH
adjustment step.
The used backwash water will be collected and transferred to the thickening process for
dewatering and disposal.
3.2.4 Solids Handling and Dewatering
The thickened sludge from the bottom of the thickening operation will be pumped to a
filter press or similar technology for dewatering. The supernatant decanted from the top
of the sludge thickening operation will be recycled to the influent of the initial chemical
oxidation step for reprocessing.
3.3 Operability and Maintenance Considerations
Process equipment has been selected from established vendors who maintain available
inventory of critical spare parts, and the turnkey service provider should also have access
to spares inventory based on duplication of unit operations in their commercial fleet. The
TR0795 20 June 2021

Geosyntec °
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GrusymccCmisidimi<x ofNC. RC.
NC 1-i,oi Nu: C-35flO onJ C-295
modular nature of the process train means that it is readily expanded or modified to adjust
to future changes in process conditions or treatment requirements.
3.4 Process Monitoring
The treatment process will be instrumented to monitor process performance consistent
with industry best practices. Process data will be recorded in a remotely accessible
database with an extended storage capacity and uninterruptible power supply.
Regulatory compliance will be maintained by means of routine sampling and analytical
testing of the untreated influent and treated water discharge points. Once a week, the
influent to each train and the effluent of each vessel will be sampled and tested at the Site
internal laboratory. Percent breakthrough is calculated for each PFAS indicator species.
First PMPA, and then PFMOAA, breakthrough values are used to determine when a bed
replacement is triggered. Generally once breakthrough begins to be observed in the
middle vessel, the lead vessel's media is changed out. The former lead vessel, filled with
new media, then becomes the lag vessel, former lag becomes the middle vessel, and
former middle vessel becomes the new lead vessel.
4. SUMMARY
In summary, the groundwater and seep flow associated with the proposed groundwater
remedy will be collected and treated (by physical/chemical precipitation, filtration and
carbon adsorption). It is anticipated that the environmental impacts associated with the
groundwater and seep water will be significantly diminished and the treated water will
exhibit a significant reduction in PFAS target compounds, total suspended solids and
dissolved metals. PAHs, and heptachlor epoxide will also be treated if present. This will
reduce the impact of these pollutants in the Cape Fear River.
5. REFERENCES
Geosyntec, 2019. Mixing Zone Report, Addendum, Chemours Fayetteville Works
Outfall 002. October 2019.
Geosyntec, 2021. Memorandum to Chemours. Chemours Fayetteville Works —
Groundwater and Seeps Water Quality Assessment. June 10, 2021.
TR0795 21 June 2021

Geosyntee °
consultants
GrusymccCmisidimi<x ofNC. RC.
NC 1-i,oi Nu: C-35flO onJ C-295
APPENDIX A
Analytical Data for Groundwater & Seep Sources
for the Engineering Design
TR0795 June 2021

June 2021
Table Al: EW-1 Table 3+ Compound Summary
Location:
EW-1
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
9
9
ND
ND
ND
ND
ND
Hfpo Dimer Acid
6
0
3.30
1.60
6.90
5.30
1.94
Hydro -EVE Acid
9
8
0.05
0.05
0.05
0.00
ND
Hydrolyzed PSDA
9
3
0.48
0.02
1.60
1.58
0.69
Hydro -PS Acid
10
9
0.03
0.03
0.03
0.00
ND
NVHOS
8
0
0.26
0.11
0.59
0.48
0.20
PEPA
10
0
0.48
0.06
1.70
1.65
0.61
PES
9
8
0.01
0.01
0.01
0.00
ND
PFECA B
9
9
ND
ND
ND
ND
ND
PFECA-G
10
10
ND
ND
ND
ND
ND
PFMOAA
10
0
34.20
13.00
74.00
61.00
24.13
PFO2HxA
10
0
10.64
2.90
32.00
29.10
10.08
PFO3OA
10
0
1.16
0.10
4.20
4.10
1.53
PFO4DA
10
8
1.04
0.08
2.00
1.92
1.36
PFO5DA
10
10
ND
ND
ND
ND
ND
PMPA
10
0
2.79
1.10
7.50
6.40
2.27
PS Acid
10
10
ND
ND
ND
ND
ND
R-EVE
9
3
0.13
0.04
0.35
0.32
0.13
R-PSDA
9
3
0.17
0.04
0.47
0.43
0.17
R-PSDCA
9
9
ND
ND
ND
ND
ND
Table A2: EW-1 Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
3
1
0.06
0.04
0.09
0.05
0.04
Bromide
12
12
ND
ND
ND
ND
ND
Calcium
3
0
2.70
2.60
2.80
0.20
0.10
Carbonate Alkalinity
0
0
--
--
--
--
--
Chloride
12
0
7.19
6.30
10.00
3.70
1.00
Fluoride
3
3
ND
ND
ND
ND
ND
Hardness
0
0
--
--
--
--
--
Iron
24
0
1.73
1.40
2.10
0.70
0.23
Magnesium
3
0
1.37
1.30
1.50
0.20
0.12
Manganese
23
0
0.02
0.02
0.03
0.01
0.00
pH
2
0
6.90
--
--
--
0.14
Phosphate
1
1
ND
ND
ND
ND
ND
Sulfate
12
0
15.08
14.00
17.00
3.00
1.00
Total Dissolved Solids
3
0
64.00
51.00
78.00
27.00
13.53
Total Organic Carbon
12
12
ND
ND
ND
ND
ND
Total Suspended Solids
3
0
8.80
5.90
13.00
7.10
3.72
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table A3: EW-3 Table 3+ Compound Summary
Location:
EW-3
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
15
12
0.097
0.095
0.1
0.005
0.002645751
Hfpo Dimer Acid
10
0
13.03
9.30
16.00
6.70
2.15
Hydro -EVE Acid
15
0
0.75
0.42
1.10
0.68
0.20
Hydrolyzed PSDA
15
0
4.25
1.50
6.50
5.00
1.85
Hydro -PS Acid
15
0
0.51
0.16
0.98
0.82
0.36
NVHOS
13
0
1.52
0.43
4.80
4.37
1.36
PEPA
15
0
2.85
1.80
4.90
3.10
0.77
PES
15
11
0.00
0.00
0.01
0.00
0.00
PFECA B
15
15
ND
ND
ND
ND
ND
PFECA-G
15
15
ND
ND
ND
ND
ND
PFMOAA
15
0
132.13
27.00
470.00
443.00
129.07
PFO2HxA
15
0
32.53
14.00
91.00
77.00
20.87
PFO3OA
15
0
14.77
5.20
43.00
37.80
11.94
PFO4DA
15
0
6.76
1.20
20.00
18.80
6.66
PFOSDA
15
6
0.91
0.01
2.40
2.39
0.77
PMPA
15
0
8.41
5.70
12.00
6.30
1.78
PS Acid
15
8
0.42
0.23
0.56
0.33
0.12
R-EVE
15
2
0.73
0.17
1.20
1.03
0.33
R-PSDA
15
0
1.21
0.65
1.70
1.05
0.33
R-PSDCA
15
3
0.04
0.01
0.10
0.09
0.03
Table A4: EW-3 Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
3
0
0.75
0.41
1.40
0.99
0.56
Bromide
22
22
ND
ND
ND
ND
ND
Calcium
3
0
8.43
7.70
9.30
1.60
0.81
Carbonate Alkalinity
0
0
--
--
--
--
--
Chloride
22
0
12.42
3.00
16.00
13.00
2.67
Fluoride
4
3
0.32
0.32
0.32
--
--
Hardness
0
0
--
--
--
--
--
Iron
44
0
9.37
2.60
14.00
11.40
3.10
Magnesium
3
0
5.10
4.80
5.40
0.60
0.30
Manganese
43
0
0.20
0.16
0.25
0.09
0.02
PH
3
0
6.83
--
--
--
0.29
Phosphate
1
1
ND
ND
ND
ND
ND
Sulfate
22
0
59.95
14.00
72.00
58.00
12.44
Total Dissolved Solids
4
1
123.33
120.00
130.00
10.00
5.77
Total Organic Carbon
22
16
0.74
0.50
0.98
0.48
0.20
Total Suspended Solids
4
0
31.08
3.30
87.00
83.70
37.92
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table A5: PIW-10S Table 3+ Compound Summary
Location:
PIW-10S
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
7
7
ND
ND
ND
ND
ND
Hfpo Dimer Acid
6
0
3.23
2.80
3.90
1.10
0.45
Hydro -EVE Acid
7
1
0.01
0.01
0.01
0.00
0.00
Hydrolyzed PSDA
7
7
ND
ND
ND
ND
ND
Hydro -PS Acid
7
0
0.11
0.09
0.15
0.06
0.02
NVHOS
6
1
0.03
0.02
0.04
0.01
0.01
PEPA
7
0
1.69
1.50
2.10
0.60
0.23
PES
7
7
ND
ND
ND
ND
ND
PFECA B
7
7
ND
ND
ND
ND
ND
PFECA-G
7
7
ND
ND
ND
ND
ND
PFMOAA
7
0
2.99
1.50
4.70
3.20
1.14
PFO2HxA
7
0
3.70
2.40
5.40
3.00
1.03
PFO3OA
7
0
0.70
0.45
0.99
0.54
0.20
PFO4DA
7
0
0.26
0.16
0.37
0.21
0.08
PFOSDA
7
2
0.02
0.01
0.03
0.02
0.01
PMPA
7
0
4.91
4.00
5.70
1.70
0.71
PS Acid
7
7
ND
ND
ND
ND
ND
R-EVE
7
0
0.15
0.09
0.20
0.11
0.04
R-PSDA
7
0
0.31
0.19
0.42
0.23
0.10
R-PSDCA
7
7
ND
ND
ND
ND
ND
Table A6: PIW-10S Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
4
0
0.84
0.62
1.20
0.58
0.28
Bromide
12
12
ND
ND
ND
ND
ND
Calcium
4
0
0.44
0.43
0.46
0.03
0.02
Carbonate Alkalinity
0
0
--
--
--
--
--
Chloride
12
0
4.13
3.10
5.50
2.40
0.66
Fluoride
3
3
ND
ND
ND
ND
ND
Hardness
0
0
--
--
--
--
--
Iron
24
13
0.52
0.04
2.60
2.56
0.78
Magnesium
4
0
0.60
0.58
0.61
0.03
0.01
Manganese
24
0
0.01
0.01
0.01
0.00
0.00
pH
3
0
6.77
--
--
--
0.25
Phosphate
0
0
--
0.00
0.00
--
--
Sulfate
12
0
9.94
9.00
11.00
2.00
0.67
Total Dissolved Solids
3
0
30.67
27.00
33.00
6.00
3.21
Total Organic Carbon
12
3
0.85
0.67
1.10
0.43
0.15
Total Suspended Solids
3
0
9.63
3.90
19.00
15.10
8.18
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table A7: PIW-5S Table 3+ Compound Summary
Location:
PIW-5S
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
6
0
0.986666667
0.57
1.8
1.23
0.478567306
Hfpo Dimer Acid
5
0
33.80
25.00
41.00
16.00
5.97
Hydro -EVE Acid
6
0
1.55
0.82
2.00
1.18
0.40
Hydrolyzed PSDA
6
0
15.67
5.00
28.00
23.00
8.26
Hydro -PS Acid
6
0
1.25
0.58
1.40
0.82
0.33
NVHOS
5
0
0.70
0.65
0.77
0.12
0.04
PEPA
6
0
26.00
17.00
44.00
27.00
10.16
PES
6
6
ND
ND
ND
ND
ND
PFECA B
6
6
ND
ND
ND
ND
ND
PFECA-G
6
6
ND
ND
ND
ND
ND
PFMOAA
6
0
38.00
31.00
61.00
30.00
11.42
PFO2HxA
6
0
31.17
27.00
38.00
11.00
4.07
PFO3OA
6
0
8.58
7.50
10.00
2.50
0.97
PFO4DA
6
0
7.05
4.70
8.70
4.00
1.34
PFOSDA
6
0
5.23
1.90
6.60
4.70
1.76
PMPA
6
0
60.67
39.00
100.00
61.00
23.53
PS Acid
6
0
2.32
1.30
4.30
3.00
1.13
R-EVE
6
0
2.42
1.90
3.00
1.10
0.42
R-PSDA
6
0
3.70
2.90
4.70
1.80
0.63
R-PSDCA
6
0
0.05
0.04
0.07
0.03
0.01
Table A8: PIW-5S Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
2
0
0.91
0.86
0.96
0.10
0.07
Bromide
11
11
ND
ND
ND
ND
ND
Calcium
2
0
1.95
1.90
2.00
0.10
0.07
Carbonate Alkalinity
0
0
--
--
--
--
--
Chloride
11
0
5.80
5.40
6.30
0.90
0.28
Fluoride
2
2
ND
ND
ND
ND
ND
Hardness
0
0
--
--
--
--
--
Iron
22
0
0.79
0.04
12.00
11.96
2.52
Magnesium
2
0
0.82
0.79
0.84
0.05
0.04
Manganese
22
0
0.02
0.02
0.03
0.01
0.00
pH
2
0
6.75
--
--
--
0.35
Phosphate
0
0
--
0.00
0.00
--
--
Sulfate
11
0
22.36
20.00
24.00
4.00
1.63
Total Dissolved Solids
2
0
51.00
46.00
56.00
10.00
7.07
Total Organic Carbon
11
1
0.90
0.52
1.10
0.58
0.20
Total Suspended Solids
2
0
2.45
2.00
2.90
0.90
0.64
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table A9: SEEPA-TR-N Table 3+ Compound Summary
Location: SEEPA-TR-N
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
7
7
ND
ND
ND
ND
ND
Hfpo Dimer Acid
4
0
12.85
8.40
19.00
10.60
4.51
Hydro -EVE Acid
7
2
0.08
0.06
0.10
0.04
0.02
Hydrolyzed PSDA
7
4
0.05
0.03
0.08
0.05
0.03
Hydro -PS Acid
7
2
0.28
0.24
0.33
0.09
0.04
NVHOS
6
2
0.09
0.07
0.12
0.05
0.03
PEPA
7
2
4.52
2.90
6.80
3.90
1.68
PES
7
7
ND
ND
ND
ND
ND
PFECA B
7
7
ND
ND
ND
ND
ND
PFECA-G
7
7
ND
ND
ND
ND
ND
PFMOAA
7
2
6.20
5.00
7.90
2.90
1.16
PFO2HxA
7
2
12.54
9.70
16.00
6.30
2.49
PFO3OA
7
2
2.12
1.70
2.80
1.10
0.43
PFO4DA
7
2
1.44
1.20
1.80
0.60
0.25
PFO5DA
7
2
0.35
0.32
0.38
0.06
0.02
PMPA
7
2
13.02
9.10
17.00
7.90
3.36
PS Acid
7
7
ND
ND
ND
ND
ND
R-EVE
7
2
0.50
0.26
0.89
0.63
0.26
R-PSDA
7
2
0.96
0.48
1.60
1.12
0.47
R-PSDCA
7
4
0.01
0.00
0.01
0.00
0.00
Table A10: SEEPA-TR-N Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
2
0
14.14
0.27
28.00
27.73
19.61
Bromide
11
10
0.27
0.27
0.27
--
--
Calcium
2
0
1.30
1.00
1.60
0.60
0.42
Carbonate Alkalinity
0
0
--
--
--
--
--
Chloride
11
0
4.16
3.50
5.40
1.90
0.54
Fluoride
2
2
ND
ND
ND
ND
ND
Hardness
0
0
--
--
--
--
--
Iron
22
0
13.90
0.74
44.00
43.26
14.73
Magnesium
2
0
1.46
0.82
2.10
1.28
0.91
Manganese
22
0
0.17
0.05
0.55
0.50
0.12
pH
2
0
6.75
--
--
--
0.35
Phosphate
0
0
--
0.00
0.00
--
--
Sulfate
11
0
10.73
10.00
12.00
2.00
0.79
Total Dissolved Solids
2
0
106.00
42.00
170.00
128.00
90.51
Total Organic Carbon
11
0
12.88
5.30
24.00
18.70
5.74
Total Suspended Solids
2
0
1100.00
1100.00
1100.00
--
0.00
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table All: SEEPA-WALL Table 3+ Compound Summary
Location: SEEPA-WALL
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
24
0
1.219166667
0.14
9.1
8.96
1.728462289
Hfpo Dimer Acid
11
0
28.36
19.00
41.00
22.00
5.94
Hydro -EVE Acid
24
0
1.60
0.14
3.50
3.36
0.72
Hydrolyzed PSDA
24
0
24.05
3.30
72.00
68.70
16.10
Hydro -PS Acid
29
3
1.35
0.01
3.50
3.49
0.57
NVHOS
23
0
1.03
0.23
1.70
1.47
0.44
PEPA
28
0
11.75
6.90
22.00
15.10
4.75
PES
24
24
ND
ND
ND
ND
ND
PFECA B
24
24
ND
ND
ND
ND
ND
PFECA-G
29
29
ND
ND
ND
ND
ND
PFMOAA
29
0
70.93
15.00
130.00
115.00
41.13
PFO2HxA
29
0
35.38
18.00
55.00
37.00
11.30
PFO3OA
29
0
11.44
4.40
18.00
13.60
4.16
PFO4DA
29
0
6.91
1.40
11.00
9.60
2.28
PFO5DA
29
1
4.47
0.25
7.10
6.85
1.54
PMPA
28
0
27.25
17.00
46.00
29.00
7.94
PS Acid
29
2
4.56
0.02
31.00
30.98
5.92
R-EVE
24
0
1.36
0.80
3.60
2.80
0.53
R-PSDA
24
0
2.47
0.32
8.30
7.98
1.42
R-PSDCA
24
5
0.06
0.02
0.12
0.10
0.02
Table Al2: SEEPA-WALL Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
7
0
3.48
0.11
14.00
13.89
4.93
Bromide
12
12
ND
ND
ND
ND
ND
Calcium
7
0
3.14
1.31
6.40
5.09
2.24
Carbonate Alkalinity
5
5
ND
--
--
--
ND
Chloride
18
0
5.56
4.00
12.20
8.20
2.07
Fluoride
3
2
0.41
0.41
0.41
--
--
Hardness
0
0
--
--
--
--
--
Iron
27
0
1.63
0.07
21.40
21.33
4.10
Magnesium
7
0
0.89
0.51
1.50
0.99
0.36
Manganese
27
0
0.05
0.02
0.42
0.40
0.08
pH
3
0
6.77
--
--
--
0.25
Phosphate
5
4
1.00
1.00
1.00
--
--
Sulfate
16
0
14.88
8.60
30.30
21.70
5.96
Total Dissolved Solids
7
0
62.64
39.50
113.00
73.50
26.15
Total Organic Carbon
16
0
2.98
0.58
10.40
9.82
2.31
Total Suspended Solids
9
0
124.26
4.70
712.00
707.30
223.19
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.

June 2021
Table A13: SEEPB-WALL Table 3+ Compound Summary
Location: SEEPB-WALL
Table 3+ Compounds
# of Results
# of Non -Detects
Average (ug/L)
Min (ug/L)
Max (ug/L)
Range (ug/L)
Std Dev (ug/L)
EVE Acid
29
0
8.624137931
1.4
46
44.6
11.3600382
Hfpo Dimer Acid
17
0
37.47
25.00
85.00
60.00
18.93
Hydro -EVE Acid
29
0
3.30
0.85
11.00
10.15
2.77
Hydrolyzed PSDA
29
0
43.93
21.00
120.00
99.00
22.31
Hydro -PS Acid
33
2
1.63
0.49
4.70
4.21
1.32
NVHOS
28
0
3.57
1.80
8.50
6.70
1.88
PEPA
31
0
22.13
12.00
50.00
38.00
11.69
PES
29
25
0.07
0.01
0.21
0.20
0.10
PFECA B
29
27
0.11
0.05
0.17
0.12
0.09
PFECA-G
33
31
0.11
0.00
0.21
0.21
0.15
PFMOAA
33
0
118.08
4.80
200.00
195.20
80.31
PFO2HxA
33
0
34.76
11.00
50.00
39.00
13.64
PFO3OA
33
0
7.20
2.50
12.00
9.50
2.80
PFO4DA
33
0
1.95
0.79
7.70
6.91
1.20
PFO5DA
33
5
0.72
0.13
1.90
1.77
0.62
PMPA
31
0
47.19
32.00
87.00
55.00
17.18
PS Acid
33
1
7.56
0.04
31.00
30.96
8.97
R-EVE
29
0
4.38
2.00
13.00
11.00
3.45
R-PSDA
29
0
5.81
2.50
16.00
13.50
3.64
R-PSDCA
29
2
0.11
0.05
0.38
0.33
0.10
Table A14: SEEPB-WALL Treatment Parameter Summary
Treatment Parameter
# of Results
# of Non -Detects
Average (mg/L)
Min (mg/L)
Max (mg/L)
Range (mg/L)
Std Dev (mg/L)
Aluminum
6
0
0.80
0.39
1.45
1.06
0.46
Bromide
12
12
ND
ND
ND
ND
ND
Calcium
6
0
0.96
0.69
1.58
0.89
0.32
Carbonate Alkalinity
4
4
ND
--
--
--
ND
Chloride
20
0
7.67
5.00
16.20
11.20
2.97
Fluoride
3
3
ND
ND
ND
ND
ND
Hardness
0
0
--
--
--
--
--
Iron
26
0
0.85
0.37
3.75
3.38
0.68
Magnesium
6
0
0.82
0.67
1.31
0.64
0.25
Manganese
26
0
0.03
0.02
0.41
0.40
0.08
pH
3
0
6.67
--
--
--
0.29
Phosphate
4
4
ND
ND
ND
ND
ND
Sulfate
15
0
10.70
7.00
24.40
17.40
4.70
Total Dissolved Solids
6
0
46.33
26.00
74.00
48.00
15.64
Total Organic Carbon
15
0
3.92
2.60
5.50
2.90
0.87
Total Suspended Solids
10
0
93.60
11.00
300.00
289.00
113.50
*pH expressed in standard units
Legend:
ug/L = micrograms per liter
mg/L = milligrams per liter
Min = minimum
Max = maximum
Range = difference between max and min
Std Dev = standard deviation
Engineering Report - Groundwater and Seeps Treatment System
Prepared by: Geosyntec Consultants of NC, P.C.