2020.08.31_CCO.p12_PFASMassLoadingProtocol

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TABLE OF CONTENTS
1 INTRODUCTION ................................................................................................ 1
2 DESCRIPTION OF PFAS MASS LOADS ......................................................... 2
2.1 Mass Loading Terminology......................................................................... 2
2.2 Cape Fear River PFAS Mass Load .............................................................. 2
2.3 Bladen Bluffs and Kings Bluff PFAS Sampling ......................................... 2
2.4 Cape Fear River PFAS Mass Loading Model ............................................. 3
3 SAMPLING AND MEASUREMENT LOCATIONS AND FREQUENCIES ... 4
3.1 Cape Fear River PFAS Mass Load Sampling ............................................. 4
3.2 Bladen Bluffs and Kings Bluff PFAS Sampling ......................................... 4
3.3 Cape Fear River PFAS Mass Loading Model Sampling ............................. 5
3.4 Potential Adjustments to Sampling Program............................................... 6
4 CALCULATION METHODOLOGIES ............................................................... 6
4.1 Cape Fear River PFAS Mass Load Calculation Methodology .................... 6
4.1.1 Baseline Mass Load Calculation Methodology .............................. 6
4.1.2 In-River Mass Load Calculation Methodology .............................. 7
4.1.3 Captured Mass Load Calculation Methodology ........................... 10
4.2 Bladen Bluffs and Kings Bluff Intake Calculation Methodology ............. 11
4.3 Cape Fear River PFAS Mass Loading Model Calculation Methodology . 12
4.4 PFAS Mass Loading Model Pathways ...................................................... 13
4.4.1 Upstream Cape Fear River (Transport Pathway 1) ....................... 13
4.4.2 Tributaries – Willis Creek, Georgia Branch Creek, and Old Outfall
002 (Transport Pathways 2, 7 and 9) ........................................................ 14
4.4.3 Aerial Deposition to the Cape Fear River (Transport Pathway 3) 14
4.4.4 Onsite Groundwater (Transport Pathways 5 and 6) ...................... 14
4.4.5 Outfall 002 (Transport Pathway 4) ............................................... 15
4.4.6 Adjacent and Downstream Offsite Groundwater (Transport
Pathway 8) ................................................................................................ 16
4.5 Potential Adjustments ................................................................................ 16
5 REPORTING ...................................................................................................... 17
6 REFERENCES ................................................................................................... 17

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LIST OF TABLES
Table 1: PFAS Analytical Methods and Analyte list
Table 2: Surface Water, Seep and River Sampling Locations and Flow Measurement
Methods
Table 3: Groundwater Monitoring Well Sampling and Water Level Measurement
Locations

LIST OF FIGURES
Figure 1: Potential PFAS Transport Pathways to the Cape Fear River from Site
Figure 2: Cape Fear River Watershed and Downstream Drinking Water Intakes
Figure 3: Groundwater Monitoring Well Sampling and Water Level Measurement
Locations
Figure 4: Surface Water, Seep and River Water Sampling and Flow Measurement
Locations
Figure 5: Cape Fear River Sample Locations

LIST OF APPENDICES
Appendix A: Field Methods
Appendix B: Supporting Calculations – Direct Aerial Deposition on Cape Fear River
Appendix C: Supporting Calculations – Onsite Groundwater
Appendix D: Supporting Calculations – Adjacent and Downstream Offsite
Groundwater

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LIST OF ABBREVIATIONS
CFR Cape Fear River
CFR-BLADEN Bladen Bluffs
CFR-KINGS Kings Bluff
CFR-TARHEEL Tar Heel Ferry Road bridge
CO Consent Order
DEQ Department of Environmental Quality
DSI Dynamic Solutions International
EFDC Environmental Fluid Dynamics Code
kg Kilograms
L/s liters per second
mg/s Milligrams per second
Mass Loading Protocol PFAS Mass Loading Protocol
NC North Carolina
ng/L nanograms per liter
PFAS Per- and polyfluoroalkyl substances
SOP Standard Operating Procedures
USGS United States Geological Survey

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1 INTRODUCTION
Geosyntec Consultants of NC, PC (Geosyntec) has prepared this per- and polyfluoroalkyl
substances (PFAS) Mass Loading Protocol (“Mass Loading Protocol”) on behalf of The
Chemours Company FC, LLC (Chemours) pursuant to the requirements of Paragraph 1
(a) and (b) of the Addendum to Consent Order Paragraph 12 (CO Addendum). The
objective of this Mass Loading Protocol document is to describe the sampling and
measurement activities, calculation methods and reporting requirements associated with
the following mass loading programs:
 Cape Fear River PFAS Mass Load Sampling;
 Bladen Bluffs and Kings Bluff PFAS Sampling; and
 Cape Fear River PFAS Mass Loading Model Pathway Sampling.
The CO Addendum specifies that PFAS mass loading calculations estimate the mass
loading for each of the PFAS compounds listed in Attachment C of the CO (February 25,
2019). The calculations presented in this document are suitable for evaluating the mass
loads of any given set of selected PFAS. For the purposes of calculations and reporting
for Paragraph 1 of the CO Addendum, the set of PFAS will be those listed in Attachment
C of the Consent Order and listed in Table 1.
The remainder of this document is organized as follows:
 Section 2 – Description of PFAS Mass Loads which presents an overview of the
three types of PFAS Mass Loading quantities described by this protocol
document;
 Section 3 – Sampling and Measurement Locations and Frequency which presents
the sampling requirements for the mass loads;
 Section 4 – Calculations which present the protocol by which the mass loads will
be calculated; and
 Section 5 – Reporting which describes how the results of the protocol will be
reported.

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2 DESCRIPTION OF PFAS MASS LOADS
This section provides first an overview of terms used in this document and then an
overview of each of the sampling, calculation and reporting activities for the three mass
loading programs.
2.1 Mass Loading Terminology
The following mass loading terms are used in this document:
 Mass Load – the quantity in kilograms (kg; mass) of PFAS present in a pathway
over a period of time (e.g., 5 kg from a pathway over a certain number of days).
This quantity is used to assess the total amount of PFAS that have reached the
Cape Fear River;
 Mass Discharge – the quantity in milligrams per second (mg/s; mass over time)
of PFAS present in a pathway at a specific point in time. This quantity is used for
assessing the relative loadings from the different pathways in the Mass Loading
Model and the loading of PFAS at Bladen Bluffs and Kings Bluff raw water
intakes.
2.2 Cape Fear River PFAS Mass Load
The Cape Fear River PFAS Mass Load focuses on PFAS mass loads measured in the
river, and loads prevented from reaching the Cape Fear River from the Fayetteville Works
Facility. Specifically, three loads are assessed:
1. The “In-River Mass Load” which is the total measured in-river PFAS mass load
that reached the river as measured in kg over a period of time based on time-
weighted concentrations of PFAS from samples collected at the Tar Heel Ferry
Road bridge (CFR-TARHEEL) and Cape Fear River flow volumes;
2. The “Captured Mass Load” which is the PFAS mass load, measured in kg,
prevented from reaching the Cape Fear River by remedies implemented by
Chemours; and
3. The “Baseline Mass Load” which is the sum of the River Mass Load and the
Captured Mass Load. The Baseline Mass Load will be used to assess PFAS Mass
Loading reductions to surface water achieved over time.
2.3 Bladen Bluffs and Kings Bluff PFAS Sampling
The Bladen Bluffs and Kings Bluff PFAS sampling will collect monthly samples to
measure PFAS loadings in the Cape Fear River adjacent to the Bladen Bluffs and Kings

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Bluff points in time from discrete water samples. The loadings are expressed as mass per
unit time, i.e., mg/s.
2.4 Cape Fear River PFAS Mass Loading Model
The Cape Fear River PFAS Mass Loading Model will estimate the mass discharge of
PFAS from nine potential PFAS transport pathways to the Cape Fear River. The potential
pathways are listed below, and are shown on the conceptual diagram provided in Figure
1:
 Transport Pathway 1: Upstream Cape Fear River and Groundwater – This
pathway is comprised of contributions from non-Chemours related PFAS sources
on the Cape Fear River and tributaries upstream of the Site, and upstream offsite
groundwater with PFAS present from aerial deposition;
 Transport Pathway 2: Willis Creek – Groundwater and stormwater discharge
and aerial deposition to Willis Creek and then to the Cape Fear River;
 Transport Pathway 3: Direct aerial deposition of PFAS on the Cape Fear River;
 Transport Pathway 4: Outfall 002 – Comprised of (i) water drawn from the Cape
Fear River and used as non-contact cooling water, (ii) treated non-Chemours
process water, (iii) Site stormwater, (iv) steam condensate, and (v) power
neutralization discharge, which are then discharged through Outfall 002;
 Transport Pathway 5: Onsite Groundwater – Direct upwelling of onsite
groundwater to the Cape Fear River from the Black Creek Aquifer;
 Transport Pathway 6: Seeps – Onsite groundwater seeps A, B, C and D above
the Cape Fear River water level on the bluff face from the facility that discharge
into the Cape Fear River;
 Transport Pathway 7: Old Outfall 002 – Groundwater discharge to Old Outfall
002 and stormwater runoff that flows into the Cape Fear River;
 Transport Pathway 8: Adjacent and Downstream Offsite Groundwater – Offsite
groundwater adjacent and downstream of the Site upwelling to the Cape Fear
River; and,
 Transport Pathway 9: Georgia Branch Creek – Groundwater, stormwater
discharge and aerial deposition to Georgia Branch Creek and then to the Cape
Fear River.
Results of the mass loading model assessments are expressed as both the PFAS mass
discharge (in mg/s) per pathway and the relative estimated mass discharge per pathway.

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3 SAMPLING AND MEASUREMENT LOCATIONS AND FREQUENCIES
This section describes sampling and measurement locations and frequencies for the mass
loading programs. The field methods to be used for the sampling programs is provided in
Appendix A.
3.1 Cape Fear River PFAS Mass Load Sampling
To assess the Cape Fear River PFAS In-River and Baseline Mass Loads (Section 2.2), a
24 hour composite sample of the Cape Fear River will be collected twice per week using
an autosampler placed at CFR-TARHEEL (Figure 2). Additional sampling will be
conducted within 24 hours of rain events when these rain events are predicted two days
before and with at least a 70% likelihood and to be of 1 ½ inches or greater in a 24 hour
period. Such additional sampling will be conducted up to twice per month for any month
in which there are two or more such rain events. River flow volumes corresponding to
collected samples will be determined using Cape Fear River flows as reported by the
United States Geological Survey (USGS).
Remedies implemented or to be implemented by Chemours (e.g. onsite seeps interim
remedies, Outfall 002 remedy) will prevent PFAS mass loads from reaching the Cape
Fear River. For certain remedies, specific sampling frequency and methods and flow
measurements will be specified in sampling plans or other sampling requirements (e.g.
NPDES permits) for such remedy.
Sampling will be conducted for a period of five years. At the end of each reporting year,
Chemours may apply to DEQ for modification of this protocol.
3.2 Bladen Bluffs and Kings Bluff PFAS Sampling
To sample the PFAS mass loading near the Bladen Bluffs and Kings Bluff Intakes
(Section 2.3), grab samples will be collected on a monthly basis from the Cape Fear River
adjacent to both intakes (Figure 2). For the Bladen Bluffs Intake sample location, flows
as reported by the United States Geological Survey (USGS) river gauging station at the
W.O. Huske Dam will be used to determine river flow volumes corresponding to
collected samples. For the Kings Bluff Intake sample location, flows as reported by the
USGS river gauging station at Cape Fear River Lock & Dam #1 will be used to determine
river flow volumes corresponding to collected samples.
Sampling will be conducted for a period of five years. At the end of each reporting year,
Chemours may request to DEQ for modification of the protocol.

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3.3 Cape Fear River PFAS Mass Loading Model Sampling
To assess the relative mass loading of PFAS to the Cape Fear River from the potential
PFAS mass loading pathways (Figure 1), pathway inputs to the Mass Loading Model will
be sampled. The following pathways and locations will be sampled (Figures 3 and 4)1,2:
 Transport Pathway 1: Upstream Cape Fear River;
 Transport Pathway 2: Willis Creek;
 Location: Intake River Water at Facility;
 Transport Pathway 4: Outfall 002;
 Transport Pathway 5: Onsite Groundwater (Table 2)3;
 Transport Pathway 6: Onsite Seeps (Seeps A through D);
 Transport Pathway 7: Old Outfall 002;
 Transport Pathway 9: Georgia Branch Creek; and
 Location: CFR-TARHEEL;
Where Site access and Site conditions permit, samples will be collected as 24-hour
composite samples. Flow rates will be measured after sample collection at seep and creek
locations specified in Table 2. Flow rates will be measured using flumes at the seeps and
using flow velocity gauging at Willis Creek and Georgia Branch Creek. Flow will then
be used to calculate volumetric flow rates. Flow data for the Intake River Water at
Facility location and Outfall 002 will be obtained from facility discharge monitoring
reports. Flow data, adjusted for travel time, recorded at the USGS river gauge at the W.O.
Huske Dam will be used for CFR-TARHEEL and CFR-BLADEN. Flow data recorded
at the USGS river gauge at Cape Fear Lock and Dam #1 will be used for CFR-KINGS.

The travel time adjustment calculations were based on a calibrated hydrodynamic model
using the Dynamic Solutions International (DSI) version of the Environmental Fluid

1 Transport pathway 3, direct aerial deposition, is estimated based on modeling calculations
and therefore is not sampled.
2 Transport pathway 8, adjacent and downstream groundwater, is estimated based on transport
pathway 1, upstream Cape Fear River and is therefore not sampled for pathway estimation
purposes. The downstream river is sampled to evaluate the PFAS mass loading to the Cape
Fear River.
3 This list of groundwater wells to be sampled is derived from the Corrective Action Plan
(Geosyntec, 2019b) with wells INSITU-02 and BLADEN-1S removed as these wells are
perennially dry.

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Dynamics Code (EFDC). The model domain runs from downtown Fayetteville, North
Carolina to Lock and Dam #1 near Kelly, North Carolina. The model was calibrated to
flow data from the USGS gauges at W. O. Huske Dam and Lock and Dam #1 and water
surface elevation data (from the USGS Gauges at Fayetteville, NC and the W. O. Huske
Dam) for two periods: January-February 2017 and May-June 2018.
To estimate travel times from W. O. Huske Dam to the Bladen Bluffs Intake, a dye release
was modeled for 5 hours from Huske Dam at the following flow rates based on real flow
data from calendar year 2017. Travel times were estimated based on first arrival as
defined by the point where the concentration at the arrival point reaches 10% of the
maximum concentration at the indicated location. The travel time to river flow
relationships to locations CFR-BLADEN, CFR-TARHEEL and CFR-KINGS (i.e.,
regressions) had R2 values of 0.997, 0.997, and 0.943, respectively.
The sampling of the inputs to the Mass Loading Model will be conducted for a period of
one year on a monthly basis and then for the next four years on a quarterly basis. At the
end of each reporting year, Chemours may apply to DEQ for modification of the protocol.
3.4 Potential Adjustments to Sampling Program
Planned sampling outlined in this protocol document will be conducted where locations
are safely, logistically and legally accessible. The sampling and measurement protocols
described in this section have been outlined based on the present understanding of Site
conditions. If conditions change, modifications may need to be made to this protocol.
Additionally, during a field program, the field team may need to modify the sampling
program outlined in this protocol. Modifications to the sampling protocol will be
described in submitted reports described in Section 5.
4 CALCULATION METHODOLOGIES
This section presents the calculation methodologies to be applied to estimate the mass
loading quantities for the three mass loading programs.
4.1 Cape Fear River PFAS Mass Load Calculation Methodology
This subsection presents the calculation methodology for calculating the Cape Fear River
PFAS Baseline Mass Load, In-River Mass Load and Captured Mass Load.
4.1.1 Baseline Mass Load Calculation Methodology
The Baseline Mass Load is calculated following Equation 1 below:
Equation 1: Total PFAS Baseline Mass Load
𝑀஼ிோ = 𝑚஼ிோ +𝑚ோ௘௠௘ௗ௜௘௦

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where,
𝑀஼ிோ = is the Baseline Mass Load of PFAS compounds in the Cape Fear River,
including the mass load prevented from reaching the Cape Fear River by
implemented remedies, measured in kg;
𝑚஼ிோ = is the River Mass Load estimated using PFAS concentrations in samples
taken in the Cape Fear River downstream of the Site where the river is well mixed
and using measured river flow volumes; and
𝑚ோ௘௠௘ௗ௜௘௦ = is the Captured Mass Load prevented from reaching the Cape Fear River
by remedies implemented by Chemours;
There have been numerous interim and permanent actions taken to limit PFAS reaching
the Cape Fear River prior to this baseline period, i.e., air abatement measures (installation
of the thermal oxidizer and carbon beds, etc.), grouting of the terracotta pipe, sediment
removal from channels, among others, and these may not be captured in this baseline load
calculation methodology but should be considered in the overall assessment of PFAS
reductions.

4.1.2 In-River Mass Load Calculation Methodology
The In-River Mass Load is the estimated mass, in kilograms, that has reached the Cape
Fear River over a period of time. The River Mass Load, 𝑚஼ிோ, is calculated using
primarily composite samples from the Cape Fear River and corresponding river flow
volumes. The In-River Mass Load is calculated for a given time period following
Equation 2 below:
Equation 2: In-River Mass Load
𝑚஼ிோ = ෍ ෍ 𝐶஼ிோ,௡,௜ × 𝑉஼ிோ,௡
୍
௜ୀଵ
ே
௡ୀଵ

where,
𝑚஼ிோ = is the Total PFAS mass load estimated from PFAS concentrations in samples
taken in the Cape Fear River downstream of the Site where the river is well mixed
and measured river flow volumes;
𝑛= represents individual time intervals during a monitoring period;
𝑁= is the total number of time intervals in a monitoring period;
i = represents each of the PFAS constituents being evaluated;

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I = represents total number of PFAS constituents included in the summation;
𝑐஼ிோ,௡,௜ = is the measured or estimated concentration of PFAS for each baseline mass
loading time interval based on samples collected from the Cape Fear River; and
𝑉஼ிோ,௡ = is the volume of Cape Fear River water that flowed passed the sampling
point during the baseline mass loading time interval.
4.1.2.1 Calculation of Time-Weighted Average Concentrations
During a time period, multiple samples will be collected, most of them being composite
samples and some potentially being grab samples. The calculation methodology outlined
here considers all collected samples in the time period, including cases where samples
are collected contemporaneously with each other and cases where composite sample
collection events do not occur successively, as is the case with twice weekly 24 hour
composite samples. To facilitate this calculation, the overall time period is separated into
discrete time intervals with corresponding time-weighted concentrations calculated for
each interval. The time intervals are defined as the duration in time between two sampling
events, where sampling events consist of:
 Beginning of a composite sample collection;
 End of a composite sample collection; or
 Collection of a grab sample.
Equation 3 shows the formula used to calculate the total flow volume for each interval.

Equation 3: Mass Load Time Interval Concentration
𝐶஼ிோ,௡,௜ = ෍ 𝐶஼ிோ,௡,௜,௞ × 𝑤௞
௄
௞ୀଵ

= ෍ 𝐶஼ிோ,௡,௜,௞
𝑡௡𝑡௞
∑𝑡௡𝑡௞
௄௞ୀଵ
௄
௞ୀଵ

where,
𝐶஼ிோ,௡,௜ = is the measured or estimated concentration of PFAS for each baseline
mass loading time interval based on samples collected from the Cape Fear
River;

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𝑛= represents individual time intervals during a monitoring period;
i = represents each of the PFAS constituents being evaluated;
k = represents a concentration sample considered in the mass load time interval;
K = is the total number of concentration samples considered in the mass load time
interval;
𝐶஼ிோ,௡,௜,௞ = is the measured concentration of PFAS for each sample result
considered in calculating the time-weighted average concentration for a mass
load time interval; and
𝑤௞ = is the weighting factor calculated for and applied individually to each
concentration, where,
𝑡௡ = the length of time of the mass load time interval; and
𝑡௞ = the length of time of the collected sample. For composite samples, 𝑡௞ is the total
length of the composite sample collection period. If 𝑡௞ <𝑡௡, i.e., the composite
sample collection time is less than the interval time, or a grab sample was
collected, then 𝑡௞ is set to equal the interval time for the purposes of concentration
weighting.
4.1.2.2 Calculation of Travel Time Adjusted Flow Volumes
To calculate the mass load, river flow volumes are calculated for each time interval using
United States Geological Survey (USGS) reported flows at the W.O. Huske Dam. A time
offset is applied to the flow data to account for travel time for the flow passing the W.O.
Huske Dam to reach the CFR-TARHEEL location. River flow passing the W.O. Huske
is estimated to have a travel time between 2 and 12 hours to reach CFR-TARHEEL
depending on river flow (e.g., the flow rate passing W.O. Huske Dam at 8 am will arrive
at CFR-TARHEEL at 11 am for a 3 hour travel time). Travel times are estimated based
on the results of a numerical model of the Cape Fear River which developed a regression
curve between the USGS reported gage heights at W.O. Huske Dam and travel times.
Equation 4 shows the formula used to calculate the time offset. The total volume of flow
for each mass loading interval is calculated as the sum of all individual flow
measurements for an interval where each measurement multiplied by its corresponding
15-minute time duration. Equation 5 shows the formula used to calculate the total flow
volume for each interval.
Equation 4: Travel time offset W.O. Huske Dam to Tar Heel Ferry Road Bridge
𝑡௢௙௙௦௘௧ = 13,422 ∙𝑄ௐைு஽ିଵ + 2.019
where,

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𝑡௢௙௙௦௘௧ = is the travel time flow in the Cape Fear River takes in hours to pass from the
W.O. Huske Dam to CFR-TARHEEL based on the measured flow in the Cape
Fear River at the W.O. Huske Dam;
𝑄ௐைு஽ିଵ = is the inverse of the measured flow rate of the Cape Fear River at W.O.
Huske Dam for a given point in time in cubic feet per second (ft3/s); and
13,422 𝑎𝑛𝑑 2.019 = are constant values, which correspond to the slope and
intercept of the regression line, respectively.

Equation 5: Cape Fear River Flow Volume per Interval
𝑉஼ிோ,௡ = ෍ 𝑄ௐைு஽,௡,௠ା௧೚೑೑ೞ೐೟ × (𝑡௡,௠ −𝑡௡,௠ିଵ)
ெ
௠ୀଵ

where,
𝑉஼ிோ,௡ = is the volume of Cape Fear River water that flowed past the sampling point
during the baseline mass loading time interval;
n = represents the baseline mass loading time intervals number for which the volume
is being calculated;
m = represents a 15-minute flow measurement recorded by the USGS station at W.O.
Huske Dam during a baseline mass loading time interval “n”;
M = the total number of 15-minute flow measurements recorded by the USGS station
at W.O. Huske Dam during a baseline mass loading time interval “n”;
𝑄ௐைு஽,௡,௠ା௧೚೑೑ೞ೐೟ = is the Cape Fear River flow rate (units of volume per time) at
Tar Heel Ferry Road bridge based on the recorded values at W.O.Huske Dam and
adjusted for travel time as described in Equation 4; and
𝑡௡,௠ −𝑡௡,௠ିଵ = is the length of time for the flow measurement durations (units of
time reported typically in 15-minute intervals by USGS).
4.1.3 Captured Mass Load Calculation Methodology
Remedies implemented or to be implemented by Chemours (e.g., onsite seeps interim
remedies, Outfall 002 remedy, etc.) will prevent PFAS mass loads from reaching the Cape
Fear River. The specific methodology for estimating the prevented mass per remedy will
be developed on a per remedy basis. The goal of such calculations will be to estimate, for
a given time period, the PFAS mass diverted from reaching the Cape Fear River by the
remedy that would have otherwise reached the Cape Fear River.

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4.2 Bladen Bluffs and Kings Bluff Intake Calculation Methodology
This subsection presents the methodology used to calculate PFAS mass at Bladen Bluffs
and Kings Bluff Intakes. Total PFAS mass is calculated as:
Equation 6: Mass at Bladen Bluffs and Kings Bluff Intakes
𝑀஻஻/௄஻ = ෍ 𝑀௜ =෍ 𝐶௜ × 𝑄
ூ
௜ୀଵ
ூ
௜ୀଵ

where,
MBB/KB = Total PFAS mass in the downstream river locations (Bladen Bluffs or Kings
Bluff Intakes) measured in mass per unit time [MT-1], typically mg/s;
i = represents each of the PFAS constituents being evaluated;
I = represents total number of PFAS constituents included in the summation of Total
PFAS concentrations;
Mi = mass load of each PFAS constituent i with measured units in mass per unit time
[MT-1], typically mg/s;
Ci = concentration of each PFAS constituent i with measured units typically in
nanograms per liter; and
Q = volumetric flow rate with measured units in volume per time [L3T-1], typically
liters per second (L/s). For Bladen Bluffs, the volumetric flow recorded at W.O.
Huske Dam is adjusted for travel time using Equation 7.
For Bladen Bluffs, the time offset applied to the flow recorded at W.O. Huske Dam will
be estimated based on the results of a numerical model of the Cape Fear River, which
developed a regression curve between the USGS reported gage heights at W.O. Huske
Dam and travel times (Equation 8).
Equation 7: Travel time offset W.O. Huske Dam to Bladen Bluffs
𝑡௢௙௙௦௘௧ = 8,826 ∙𝑄ௐைு஽ିଵ + 1.530
where,
𝑡௢௙௙௦௘௧ = is the travel time flow in the Cape Fear River takes in hours to pass from the
W.O. Huske Dam to Bladen Bluffs Intake location based on the measured flow in
the Cape Fear River at the W.O. Huske Dam;
𝑄ௐைு஽ିଵ = is the inverse of the measured flow rate of the Cape Fear River at W.O.
Huske Dam for a given point in time in cubic feet per second; and

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8,826 𝑎𝑛𝑑 1.530 = are constant values, which correspond to the slope and intercept
of the regression line, respectively.

4.3 Cape Fear River PFAS Mass Loading Model Calculation Methodology
This subsection presents the Mass Loading Model methodology for estimating the mass
discharge of PFAS from the potential PFAS transport pathways to the Cape Fear River.
The Total PFAS mass discharge entering the Cape Fear River is defined in this model as
the combined mass per unit time or mass discharge (e.g., mg/s) from potential pathways.
Total PFAS mass load entering the Cape Fear River is calculated as:
Equation 9: Cape Fear River Estimated Mass Discharge from Mass Loading Model
𝑀𝐷஼ிோ = ෍෍ 𝑀𝐷௣,௜ =෍෍൫𝐶௡,௜ × 𝑄௡൯
ூ
௜ୀଵ
ଽ
௣ୀଵ
ூ
௜ୀଵ
ଽ
௣ୀଵ

where,
MDCFR = Total PFAS estimated mass discharge entering the Cape Fear River,
measured in mass per unit time [MT-1], typically mg/s;
p = represents each of the 9 potential PFAS transport pathways described further in
Section 4.4. To facilitate model construction, the Seeps (Transport Pathway 6)
were further discretized as Seep A (Transport Pathway 6A), Seep B (Transport
Pathway 6B), Seep C (Transport Pathway 6C) and Seep D (Transport Pathway
6D);
i = represents each of the PFAS constituents being evaluated;
I = represents total number of PFAS constituents included in the summation of Total
PFAS concentrations;
MDp,i = mass load of each PFAS constituent i from each potential pathway p with
measured units in mass per unit time [MT-1], typically mg/s;
Cp,i = concentration of each PFAS constituent i from each potential pathway p with
measured units in mass per unit volume [ML-3], typically nanograms per liter
(ng/L); and
Qn = volumetric flow rate from each potential pathway n with measured units in
volume per time [L3T-1], typically L/s.

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4.4 PFAS Mass Loading Model Pathways
The nine potential pathways representing compartments to the PFAS Mass Loading
Model are described below. These pathways were identified as potential contributors of
PFAS to river PFAS concentrations.
4.4.1 Upstream Cape Fear River (Transport Pathway 1)
The upstream PFAS mass discharge contribution to Cape Fear River will be estimated
using measured Cape Fear River PFAS concentrations and flow rates. One water sample
will be collected immediately upstream of the Site and Willis Creek at River Mile 76 to
estimate upstream PFAS mass discharge contribution to Cape Fear River. River water
samples will be collected at the thalweg (i.e., deepest point of the river transect) at mid-
depth in the water column.
Volumetric flow rates for the Cape Fear River were measured at the USGS flow gauging
station located at the W.O. Huske Dam, approximately 0.5 river miles downstream of the
Site. The volumetric flow rate immediately upstream of the Site (River Mile 76) will be
estimated using a volumetric budget accounting for flows between River Mile 76 and the
W.O. Huske Dam. The volumetric flow rate at River Mile 76 will be estimated by
subtracting inflows from Willis Creek, upwelling groundwater, seeps to the river, and
Outfall 002 and by adding the river water intake from Chemours to the flow rate
measurement from the W.O. Huske Dam (Equation 6).
Equation 6: Flow at Upstream Cape Fear River and Groundwater
𝑄௎௣௦௧௥௘௔௠ = 𝑄ௐைு஽ − ൫𝑄ௐ஼ +𝑄ைி଴଴ଶ +𝑄ை௡௦௜௧௘ ீௐ +𝑄ௌ௘௘௣௦൯ + 𝑄ூ௡௧௔௞௘
where,
𝑄௎௣௦௧௥௘௔௠ = is the flow volume at River Mile 76;
𝑄ௐைு஽ = is the flow volume at W.O. Huske Dam, as reported by the USGS;
𝑄ௐ஼ = is the flow volume at Willis Creek, as measured by the point velocity method;
𝑄ைி଴଴ଶ = is the flow volume at Outfall 002 as reported in Facility Discharge
Monitoring Reports;
𝑄ை௡௦௜௧௘ ீௐ = is the flow volume for onsite groundwater, as calculated based on the
cross-sectional area, hydraulic gradient, and hydraulic conductivity for segments
of the Black Creek Aquifer along the Cape Fear River Frontage;
𝑄ௌ௘௘௣௦ = is the summed flow volume for Seeps A, B, C, and D, as measured using
flumes; and

PFAS Mass Loading Protocol.docx 14 August 2020
𝑄௜௡௧௔௞௘ = is the flow volume at the Facility intake, as reported in the Facility DMRs.

4.4.2 Tributaries – Willis Creek, Georgia Branch Creek, and Old Outfall 002
(Transport Pathways 2, 7 and 9)
The PFAS mass discharge contribution to the Cape Fear River from tributaries to the
Cape Fear River (Willis Creek, Georgia Branch Creek and Old Outfall 002) will be
estimated using PFAS concentrations and flow rate data. PFAS samples will be collected
at each tributary at a location near the discharge point to the Cape Fear River, but still far
enough upstream in the tributary where they are not potentially influenced by the Cape
Fear River. Since analytical sample locations are near the discharge point to the Cape
Fear River, model input for tributaries will account for loading from groundwater
discharging to the tributary, onsite surface water runoff into the tributary, and direct aerial
deposition on these tributaries
Volumetric discharge rates for the tributaries will be measured using a flume at Old
Outfall 002 and flow velocity gauging at the creeks as outlined in the Seeps and Creeks
Investigation Report (Geosyntec, 2019a). Detailed methods for flow measurements are
presented in Appendix A.
4.4.3 Aerial Deposition to the Cape Fear River (Transport Pathway 3)
The PFAS mass discharge from direct aerial deposition of PFAS to the Cape Fear River
will be estimated using air deposition modeling results for HFPO-DA from the Site
(ERM, 2018). Average deposition rates to the Cape Fear River will be estimated based
on the reported aerial extent and deposition contours. Estimated deposition rates will be
combined with the average river surface area and estimated residence time of flowing
Cape Fear River water to estimate a mass discharge from aerial deposition. The mass
discharge of PFAS compounds will be estimated by using the relative concentration ratios
of other PFAS to HFPO-DA based on measured concentrations from offsite wells.
Supporting documentation for this estimation is included in Appendix B. The 2018
emissions reduction scenario outlined in the ERM report (ERM, 2018) is likely a
conservative assumption as further air emission reductions controls have been
implemented compared to the modeled scenario. As assessment of air emissions controls
continues, the bases of estimating PFAS mass discharge to the river from this pathway
may be updated.
4.4.4 Onsite Groundwater (Transport Pathways 5 and 6)
The Mass Loading Model describes two groundwater PFAS transport pathways to the
Cape Fear River. First, the indirect pathway of groundwater to the onsite seeps which

PFAS Mass Loading Protocol.docx 15 August 2020
discharge to the Cape Fear River, and second, the direct pathway of Black Creek aquifer
groundwater discharging directly to the river.
4.4.4.1 Indirect Pathway – Onsite Groundwater Seeps to River (Transport Pathway 6)
Four seeps at the Site have been identified that discharge directly to the Cape Fear River:
Seep A, Seep B, Seep C and Seep D (Figure 4). The PFAS mass discharge from these
seeps to the Cape Fear River will be estimated using measured PFAS concentrations and
volumetric discharged rates. Volumetric discharge rates will be calculated using flumes
as detailed in Appendix A.
4.4.4.2 Direct Pathway – Groundwater Discharge to River (Transport Pathway 5)
The PFAS mass discharge of onsite groundwater discharge from the Black Creek Aquifer
to the Cape Fear River will be estimated by calculating the sum of the PFAS mass
discharge for eight segments of the Black Creek aquifer along the Cape Fear River
frontage. PFAS mass discharge for each segment will be calculated based on the
following parameters:
 The cross-sectional area of the Black Creek Aquifer for each segment, as
determined from a three-dimensional hydrostratigraphic model of the Site;
 The hydraulic gradient for each segment, as determined from groundwater level
contours in the vicinity of the river frontage;
 The hydraulic conductivity for each segment, as determined from slug tests
conducted on monitoring wells representative of the Black Creek Aquifer; and
 PFAS concentrations detected in monitoring wells in the vicinity of each segment.
Further details on the onsite groundwater discharge term and associated calculations are
provided in Appendix C.
4.4.5 Outfall 002 (Transport Pathway 4)
The PFAS mass discharge of PFAS from Outfall 002 to the Cape Fear River will be
estimated using measured PFAS concentrations and measured Outfall 002 volumetric
flow rates. The concentration of PFAS compounds for Outfall 002 will be adjusted for
PFAS already present in the sample collected at the Intake River Water at Facility before
being input into the model. The PFAS present in intake water are already accounted for
in the Mass Loading Model in pathways 1, 2, and 3 (Upstream River, Willis Creek and
Direct Aerial Deposition). Daily volumetric discharge from Outfall 002 to the Cape Fear
River is recorded and will be used to calculate the volumetric flow rate.

PFAS Mass Loading Protocol.docx 16 August 2020
4.4.6 Adjacent and Downstream Offsite Groundwater (Transport Pathway 8)
The PFAS mass discharge from adjacent (i.e., across or on the east side) and downstream
offsite groundwater to the Cape Fear River will be calculated based on estimated
upstream groundwater loading described in Section 4.4.1. PFAS detected in offsite
groundwater originate from aerial deposition which has occurred in all directions from
the Site (Geosyntec, 2019b). These aerially deposited PFAS have subsequently infiltrated
to groundwater and migrate towards the Cape Fear River where they lead to upstream,
adjacent and downstream offsite groundwater PFAS mass. The upstream offsite
groundwater PFAS mass discharge will be estimated relatively simply by using measured
river flows and concentrations at River Mile 76 upstream of the Site. Here only the
upstream offsite groundwater PFAS mass discharge is present in the river at this location.
Conversely, the adjacent and downstream offsite groundwater PFAS mass discharge is
difficult to measure directly since many PFAS mass discharges from all other pathways
are present in the river where these offsite groundwater contributions join the river.
Additionally, adjacent and downstream offsite groundwater have a relatively small
component of the Total PFAS mass discharge making their additional contributions to
the total discharge difficult to distinguish from other discharges already present.
Therefore, since PFAS mass discharge from offsite groundwater both upstream and
downstream of the Site follow the same dynamics (deposition, infiltration, migration,
discharge) the adjacent and downstream PFAS mass discharge will be scaled from the
upstream offsite groundwater mass discharge estimate. The downstream offsite
groundwater loadings are scaled to the upstream offsite groundwater loadings based on
the length of river downstream of the Site known to be in contact with offsite groundwater
containing PFAS compared to the length of the river upstream also in contact with offsite
groundwater containing PFAS. A description of these calculations is presented in
Appendix D.
4.5 Potential Adjustments
The calculation methodologies described in this section have been outlined based on the
present understanding of Site conditions. If conditions or methods change, modifications
may need to be made to this protocol. For example, two components of the pre-design
investigation, anticipated in Q3 and Q4 2020, includes installation of passive flux meters
in wells along the Cape Fear River and aquifer tests in extraction wells adjacent to the
Cape Fear River. Both investigations will provide a better understanding of the
connection between the Black Creek Aquifer and the Cape Fear River. Accordingly, the
Mass Loading Model may be modified to incorporate findings from these investigations.
Modifications to the calculation methodologies will be described in submitted reports

PFAS Mass Loading Protocol.docx 17 August 2020
described in Section 5. At the end of each reporting year, Chemours may request to DEQ
a modification of the protocol.
5 REPORTING
The data and results from the three mass loading sampling programs (Cape Fear River
Mass Loads, Bladen Bluffs and Kings Bluff Intakes Mass Discharge, and the Cape Fear
River Mass Loading Model) will be provided to NCDEQ on a quarterly basis where
outputs for the previous quarter are provided within ninety (90) days of the end of the
previous quarter.
6 REFERENCES
Geosyntec, 2019a. Seeps and Creeks Investigation Report. Chemours Fayetteville Works.
26 August 2019
Geosyntec, 2019b. Corrective Action Plan. Chemours Fayetteville Works. December 31,
2019.

TABLES
TABLE 1
PFAS ANALYTICAL METHODS AND ANALYTE LIST
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants NC P.C.
Analytical Method Common Name Chemical Name CASN Chemical Formula
HFPO-DA*Hexafluoropropylene oxide dimer acid 13252-13-6 C6HF11O3
PEPA Perfluoro-2-ethoxypropionic acid (Formerly Perfluoroethoxypropyl carboxylic acid)267239-61-2 C5HF9O3
PFECA-G Perfluoro-4-isopropoxybutanoic acid 801212-59-9 C12H9F9O3S
PFMOAA Perfluoro-2-methoxyacetic acid 674-13-5 C3HF5O3
PFO2HxA Perfluoro-3,5-dioxahexanoic acid (Formerly Perfluoro(3,5-dioxahexanoic) acid)39492-88-1 C4HF7O4
PFO3OA Perfluoro-3,5,7-trioxaoctanoic acid (Formerly Perfluoro(3,5,7-trioxaoctanoic) acid)39492-89-2 C5HF9O5
PFO4DA Perfluoro-3,5,7,9-tetraoxadecanoic acid (Formerly Perfluoro(3,5,7,9-tetraoxadecanoic) acid)39492-90-5 C6HF11O6
PMPA Perfluoro-2-methoxypropionic acid (Formerly 2,3,3,3-Tetrafluoro-2-(trifluoromethoxy)propanoic) 13140-29-9 C4HF7O3
PFO5DA Perfluoro-3,5,7,9,11-pentaoxadodecanoic acid 39492-91-6 C7HF13O7
PS Acid (Formerly PFESA-BP1)Ethanesulfonic acid, 2-[1-[difluoro[(1,2,2-trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2-
tetrafluoro- (Formerly PFESA-BP)29311-67-9 C7HF13O5S
Hydro-PS Acid (Formerly PFESA-BP2)Ethanesulfonic acid, 2-[1-[difluoro(1,2,2,2-tetrafluoroethoxy)methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2-
tetrafluoro- (Formerly PFESA-BP2)749836-20-2 C7H2F14O5S
PFHpA*Perfluoroheptanoic acid 375-85-9 C7HF13O2
Notes:
* - HFPO-DA and PFHpA are also analyzed by EPA Method 537 Mod.
EPA - Environmental Protection Agency
PFAS - Per- and Polyfluoroalkyl substances
SOP - Standard Operating Procedure
Table 3+ Lab SOP
TR0795

Page 1 of 1 August 2020
TABLE 2
SURFACE WATER, SEEP AND RIVER SAMPLING LOCATIONS AND AND FLOW MEASUREMENT METHODS
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC P.C.
Location ID Location Description Sample Collection Method Flow Measurement Method
OLDOF-1 Mouth of Old Outfall 002 24-hour composite Flume
SEEP-A-1 Mouth of Seep A 24-hour composite Flume
SEEP-B-1 Mouth of Seep B 24-hour composite --
SEEP-B-2 Tributary to Seep B --Flume
SEEP-B-TR1 Tributary to Seep B --Flume
SEEP-B-TR2 Tributary to Seep B --Flume
SEEP-C-1 Mouth of Seep C 24-hour composite Flume
SEEP-D-1 Mouth of Seep D 24-hour composite Flume
WC-1 Mouth of Willis Creek 24-hour composite Velocity Probe
GBC-1 Mouth of Georgia Branch Creek Grab Velocity Probe
CFR-MILE-76 Cape Fear River Mile 76 Grab USGS Data
CFR-BLADEN Cape Fear River at Bladen Bluffs Grab USGS Data
CFR-KINGS Cape Fear River at Kings Bluff Raw Water Grab USGS Data
TAR HEEL Cape Fear River at Tar Heel Ferry Road Bridge 24-hour composite USGS Data
W.O. Huske Dam USGS Gauge Site No. 02105500 --USGS Data
Intake River Water at
Facility
Water Drawn Through the Intake Sampled at
the Power Area at the Site 24-hour composite Facility DMRs
Outfall 002 Outfall 002 in open channel 24-hour composite Facility DMRs
Notes:
-- not applicable
DMRs - discharge monitoring reports
EPA - Environmental Protection Agency
PFAS - per- and polyfluoroalkyl substances
USGS - United States Geological Survey
TR0795 Page 1 of 1 August 2020
TABLE 3
GROUNDWATER MONITORING WELL SAMPLING AND WATER LEVEL MEASUREMENT LOCATIONS
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC, PC
Area Hydrogeological
Unit1 Well ID Adjacent Surface Water
Feature
Onsite Black Creek PIW-3D Cape Fear River
Onsite Floodplain PIW-7S Cape Fear River
Onsite Black Creek PIW-7D Cape Fear River
Onsite Floodplain LTW-01 Cape Fear River
Onsite Black Creek LTW-02 Cape Fear River
Onsite Floodplain LTW-03 Cape Fear River
Onsite Floodplain LTW-04 Cape Fear River
Onsite Black Creek LTW-05 Cape Fear River
Onsite Black Creek PZ-22 Cape Fear River
Onsite Surficial PW-06 Georgia Branch Creek
Onsite Surficial PW-07 Georgia Branch Creek
Onsite Surficial PW-04 Old Outfall
Onsite Black Creek PW-11 Old Outfall
Onsite Black Creek PW-09 Willis Creek
Onsite Surficial SMW-11 Willis Creek
Onsite Surficial SMW-10 Willis Creek
Onsite Black Creek SMW-12 Willis Creek
Onsite Floodplain PIW-1S Cape Fear River / Willis Creek
Onsite Surficial PIW-1D Cape Fear River / Willis Creek
Offsite Black Creek Bladen-1D Georgia Branch Creek
Notes:
1. Hydrogeologic units for existing wells determined based on boring log descriptions.
TR0795 Page 1 of 1 August 2020
FIGURES
RainRain
Cape F
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ChemoursFayetteville WorksManufacturing Area
ChemoursFayetteville WorksManufacturing Area
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Perched Zone Clay
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Non-contact cooling water from river
Non-Chemours treated process water
Stormwater
(4) Outfall 002 (Pipe to River)
Groundwater
Seep B
Seep A
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(9) G
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Raleigh, NC August 2020
Figure
1
Potential PFAS Transport Pathways to the Cape Fear River from Site
Chemours Fayetteville Works, North Carolina
Note: Image is conceptual and is not to scale
^_Kings Bluff Intake Canal
ChemoursFayettevilleWorks
Start ofCape FearRiver
Wilmington
Fayetteville
Raleigh
Bladen BluffsIntake
W.O. Huske Dam
Greensboro
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NorthCarolina
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Cape Fear River Watershed and Downstream Drinking Water Intakes
Chemours Fayetteville Works, North Carolina
Figure
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and the GIS User Community.
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
^_Chemours Fayetteville Works
Upper Basin
Middle Basin
Lower Basin
July 2020
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LTW-05
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Chemours Fayetteville Works, North Carolina
Figure
3Raleigh
1,000 0 1,000500 Feet
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Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Notes:1. Due to the scale of the map, pairs of wells that are in close proximity have been offset for visibility. Therefore, the placement of these wells on this map do not reflect their true geographic coordinates. 2. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of Environmental Quality Online GIS.
3. Basemap source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.
Legend
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³Legend
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!(Sample Location
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Notes:1. The outline of Cape Fear River is approximate and is based onopen data from ArcGIS Online and North Carolina Department ofEnvironmental Quality Online GIS.2. Basemap sources: Esri, DigitalGlobe, GeoEye, Earthstar
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Chemours Fayetteville Works, North Carolina
Figure
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1,000 0 1,000500 Feet
August 2020
2,000 0 2,0001,000 Feet
!(
!(
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³
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³
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Chemours Fayetteville Works, North Carolina
Figure
5Raleigh
2 0 21 Miles
August 2020
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1
2
APPENDIX A
Field Methods
Appendix A
1 August 2020
APPENDIX A
FIELD METHODS
This appendix describes the field methods and procedures that will be employed for collecting
onsite seep and surface water samples, gauging stream flow, groundwater level measurements,
water quality parameter assessment and sample collection.
ONSITE SEEP AND SURFACE WATER SAMPLE COLLECTION METHODS
Onsite Seep and Surface Water Composite Sampling Methods
Autosamplers will be used to collect 24-hour integrated samples from various surface water bodies
and onsite Seeps. The autosamplers will collect sample aliquots once per hour. The sample tubing
from the autosampler will be positioned at minimum 2 inches above the bottom of the water body
flow with the open end of the sample tubing pointed in the downstream direction to minimize the
potential for sediment accumulation and uptake. Autosampler materials will be consisting of high-
density polyethylene (HDPE) tubing, silicon tubing, and an HDPE sample reservoir. Water from
the sample reservoir will be decanted into laboratory supplied bottles (e.g. 250-milliliter [mL]
HDPE bottles for PFAS analysis) and then sent to an approved laboratory. Field parameters will
be measured twice for composite samples: once during composite sampling (collected directly
from the water stream), and once after composite sampling (collected from the autosampler
reservoir). The following water quality parameters will be recorded:
•pH;
•Temperature (degrees Celsius [°C]);
•Specific Conductivity (microsiemens per centimeter [µS/cm]);
•Dissolved Oxygen (DO) (milligrams per liter [mg/L]); and,
•Oxidation-Reduction Potential (ORP) (millivolts [mV])
Creek and Seep Water Grab Sampling Methods
Where composite sample collection is not feasible due to access or other field conditions, creek
and seep water samples will be collected as grab samples. Laboratory-supplied 250 mL HDPE
sample bottles will be lowered into the flowing water of the creek to collect the sample. The bottles
will be lowered into the stream either using a properly decontaminated dip rod with bottle attached
with a nylon zip tie, or in shallow streams, by hand. The bottle will be lowered into the stream
with the cap removed, open and facing oncoming flow. Where possible, the sample will be
collected from the middle of the stream. Care will be taken to avoid collecting suspended solids or
other materials in the sample. The following water quality parameters will be measured after
sample collection using water from the same location in the stream:
•pH;
•Temperature (°C);
•Specific Conductivity (µS/cm);
Appendix A
2 August 2020
•DO (mg/L); and
•ORP (mV).
Cape Fear River Water Grab Sampling Methods
Cape Fear River water samples will be collected using a peristaltic pump and new dedicated HDPE
tubing and dedicated silicone tubing for the pump head at each location. The tubing will be lowered
to the specified sampling depth below the water surface using an anchor weight and the tubing
fastened to the anchor pointing upwards. Surface water will be pumped directly from the
submerged tubing through the pump head to a flow-through cell. Field parameters will be
monitored over a 5-minute interval, then the flow-through cell will be disconnected, the tubing cut
to provide a new, clean end and a grab sample will be collected from the discharge of the peristaltic
pump in new 250 mL laboratory-supplied HDPE bottles. The following water quality parameters
will be measured:
•pH;
•Temperature (°C);
•Specific Conductivity (µS/cm);
•DO (mg/L); and
•ORP (mV).
FLOW GAUGING METHODS
Flow velocity will be measured after sample collection at seep and creek locations specified in
Table 2. Flow velocity will be measured using flumes where they exist, otherwise flow velocity
will be measured via flow meters.
Flumes
Flumes are currently installed in Seep A, Seep B, Seep C, Seep D, and Old Outfall 002 under
Nationwide Permit 38 (United States Army Corps of Engineers, June 2019). Where present, they
will be used to calculate flow based on the data collected by the level logger installed in the flume.
Flow Velocity Gauging
Where flumes are not installed (i.e., Willis Creek and Georgia Branch Creek), the flow rate of the
stream will be measured using a submersible flow meter. The flow meter will be placed beneath
the flowing stream along the cross section of the stream at regular intervals (e.g. every six inches)
and the height of the water will be recorded along with the recorded water velocity. These
measurements will then be used to calculate the volumetric flow of water passing through the
structure based on the regular geometry and measured flow rates. Flow will be measured using
two to three transects to assess variability in estimated flow. Transects that have fairly uniform
cross sections that could be gauged with minimal disturbance will be selected.
Appendix A
3 August 2020
SYNOPTIC WATER LEVEL MEASUREMENTS
Water level measurements for monitoring wells listed in Table 3 will be collected during a single
synoptic event. At each location, notes on well condition, weather, date and time of collection,
depth to bottom of well and depth to water level from top of casing will be recorded.
GROUNDWATER SAMPLING METHODS
Designated monitoring wells will be monitored as part of the quarterly monitoring activities. These
wells are listed in Table 3 and Figure 3.
The groundwater samples will be analyzed for the list of Table 3+ compounds listed in Table
1.Field equipment will be inspected by the program on-Site supervisor and calibrated daily prior
to use according to the manufacturer’s recommended guidelines. Field parameters will be
measured with a water quality meter after sample collection and will include the following:
•pH;
•Temperature (°C);
•Specific Conductivity (µS/cm);
•DO (mg/L);
•ORP (mV);
•Turbidity (nephelometric turbidity units [NTU]); and,
•Color.
Non-dedicated or non-disposable sampling equipment will be decontaminated immediately before
sample collection in the following manner:
1.De-ionized water rinse;
2. Scrub with de-ionized water containing non-phosphate detergent (i.e., Alconox®); and
3.De-ionized water rinse.
Disposable equipment (e.g. gloves, tubing, etc.) will not be reused. New sample containers will
be used for each sample.
Groundwater samples will be collected, where possible, using low-flow sampling techniques as
discussed in detail in the Long-term Groundwater Monitoring Plan (Parsons, 2018) and briefly
summarized here.
1. New disposable or dedicated HDPE tubing will be placed at the midpoint of the well’s
screened interval.
2.Water will be purged through a flow-through cell attached to a water quality meter capable
of measuring pH, temperature, specific conductivity, dissolved oxygen, and ORP.
3.Water will be pumped using a peristaltic pump, with dedicated silicone tubing for the pump
head, at wells with water level less than 30 feet. A submersible pump will be used for wells
with water level deeper than 30 feet.
Appendix A
4 August 2020
4. Groundwater will be pumped directly from submerged tubing through the pump head to a
flow-through cell until field parameters (pH, temperature, specific conductivity, DO, ORP)
and will be stabilized within ±10% over three consecutive readings within a five-minute
interval. If field parameters stabilized, but turbidity remains stable yet elevated greater than
20 NTU, field personnel will purge five well volumes prior to sample collection.
5. Water levels in the designated wells will be monitored during purging so that minimum
draw-down of the water column was maintained.
6.Once flow-through cell readings are stable, the flow-through cell will be disconnected, the
tubing cut to provide a new clean end and samples will be collected from the discharge of
the peristaltic pump in new 250 mL laboratory-supplied HDPE bottles.
7.Sample identification information (e.g., well/sample identification number, sample time
and date, samplers’ names, preservative, and analytical parameters) will be recorded on the
bottle label with permanent ink after the sample will be collected.
Sample Packing and Shipping
Upon sample collection, each containerized sample will be placed into an insulated sample cooler.
Wet ice will be placed around the sample containers within heavy-duty plastic bags within the
sample cooler.
A chain-of-custody form was completed by the field sample custodian for each sample shipment.
Sample locations, sample identification numbers, description of samples, number of samples
collected, and specific laboratory analyses will be recorded on the chain-of-custody form.
Field QA/QC Samples
Field quality assurance/ quality control (QA/QC) samples will be collected as discussed in detail
in the Long-term Groundwater Monitoring Plan (Parsons, 2018) and summarized below:
1. For samples collected to be analyzed by Method EPA 537 Modified, three blind duplicate
samples will be collected.
2.For samples collected to be analyzed by Method Table 3+, three blind duplicate samples
will be collected.
3.For samples collected to be analyzed by EPA 537, three Modified Matrix Spike and Matrix
Spike Duplicate (MS/MSD) samples will be collected.
4.For samples collected to be analyzed by Method Table 3+, three MS/MSD samples will be
collected.
5. For groundwater samples, equipment blanks and field blanks will be collected daily.
6. For surface water samples, three equipment blanks will be collected.
REFERENCES
Parsons, 2018. Long-term Groundwater Monitoring Plan. September 28, 2018.
Parsons, 2020. Fayetteville Works Health and Safety Plan.
Appendix A
5 August 2020
United States Army Corps of Engineers. Nationwide Permit 6. 19 March 2017. http://saw-
reg.usace.army.mil/NWP2017/2017NWP06.pdf. Accessed 30 January 2019.
United States Army Corps of Engineers. Nationwide Permit 36, 06 June 2019.
APPENDIX B
Supporting Calculations – Direct Aerial
Deposition on Cape Fear River
Appendix B
1 August 2020
APPENDIX B
SUPPORTING CALCULATIONS – DIRECT AERIAL DEPOSITION ON CAPE FEAR
RIVER
INTRODUCTION AND OBJECTIVE
Nine pathways (Figure 1) are identified as potentially contributing to observed Cape Fear River
per- and polyfluoroalkyl substances (PFAS) concentrations. These pathways include direct PFAS
aerial deposition to the Cape Fear River. This pathway is identified as Transport Pathway Number
3 in the PFAS mass loading model. The mass discharge (mass per unit time measured in milligrams
per second [mg/s]) from direct aerial deposition of PFAS to the Cape Fear River will be estimated
by scaling air deposition modeling results for Hexafluoropropylene oxide dimer acid (HFPO-DA;
ERM, 2018). The objective of this appendix is to present the calculations for estimating aerially
deposited PFAS directly on the Cape Fear River during a mass loading event.
APPROACH
HFPO-DA mass loading directly to the Cape Fear River will be estimated using the reported aerial
extent and deposition contours modeled for October 2018 (ERM, 2018). As depicted in (Table
B1), the HFPO-DA air loading data (micrograms per meters squared [µg/m2]) provided from ERM
(2018) will be used to calculate the net hourly deposition rate (nanograms per meters squared per
hour [ng/m2/hr]) using Equation 1 below:
Equation 1: Net Hourly Deposition Rate
𝐷𝑅ோ் = 𝑀𝐿஺ூோ
𝑡஺ூோ
where:
𝐷𝑅ோ் = Net hourly deposition rate with units of mass per area per time (M L-2 T-1), typically
in ng/m2/hr;
𝑀𝐿஺ூோ = Air mass loading of HFPO-DA with units of mass per area (M L-2), typically µg/m2;
and
𝑡஺ூோ = time that air mass loading was modeled (T), typically hours.
Depositional area along the river will be calculated using available data for river width and
computed river lengths where deposition contours were modeled (ERM, 2018). Average river
width in meters (m) along sections of the Cape Fear River will be estimated in GIS. As depicted
in Figures B1 through B5, five sections along the Cape Fear River (Center, Up River Sections 1
and 2, and Down River Sections 1 and 2) with HFPO-DA concentrations contours ranging from
40 to 640 µg/m2 have been identified and the length of the Cape Fear River along each of the
sections will be measured. For each section, the average river width and lengths between contours
shown in Figures B1 through B5 will be used to calculate cross-sectional areas (in m2) as described
in Equation below:
Appendix B
2 August 2020
Equation 2: Cape Fear River Surface Area for Each Section
𝐴௦ = 𝐿௦ × 𝑊௦
where,
𝐴௦ = total spatial area over which deposition occurs between contours (L2) in section “s”,
typically in m2;
s = section along the Cape Fear River with HFPO-DA concentrations contours ranging from
40 to 640 µg/m2 (five sections in total);
𝐿 = total length of river within section “s”, typically in m; and
𝑊௦ = average river width in section “s”, typically in m.
Start and end deposition rates (ng/m2/hr) for each section along the Cape Fear River will be
estimated based on the deposition contours and corresponding net hourly deposition rate (Table
B1); a combined deposition rate for each section will be calculated as the average of the start and
end deposition rates. River velocity (meters per hour [m/hr]) will be estimated from measured flow
rates from USGS (2020) and the calculated river cross sectional area. Section lengths will be used
to calculate HFPO-DA travel time based on the estimated river velocities. The combined
deposition rate (ng/m2/hr) from Table B1, section area (m2), and travel time (hr) will be used to
calculate mass HFPO-DA deposited (ng) as follows in Equation 3 below.
Equation 2: Total HFPO-DA Mass Discharge to Cape Fear River
𝑀𝐷ுி௉ைି஽஺ = ෍𝐷𝑅஺௏ீ,௦ × 𝐴௦ × 𝑡௦
ௌ
௦ୀଵ

where,
𝑀𝐷ுி௉ைି஽஺ = total mass discharge of HFPO-DA into the river across all sections, with units
of mass per time (M T-1), typically mg/s;
s = section along the Cape Fear River with HFPO-DA concentrations contours ranging from
40 to 640 µg/m2;
S = total number of sections along the Cape Fear River with HFPO-DA concentrations contours
ranging from 40 to 640 µg/m2, five in total;
𝐷𝑅஺௏ீ,௦ = average deposition rate based from the ERM model (2018) in section “s”, typically
in ng/m2/hr;
𝐴௦ = spatial area over which deposition occurs in section “s”, typically in m2; and
𝑡௦ = travel time through the river length in section “s”, typically in hr.
As reported in the Corrective Action Plan (Geosyntec 2019), ten offsite groundwater seeps south
of Old Outfall 002 (Seeps E to M) were identified on the west bank of the Cape Fear River south
of the Site. Seeps E to M were sampled in October 2019 and Seeps E to K were sampled in March
Appendix B
3 August 2020
2020. The results of both sampling events indicate that Seeps E to M show an aerial deposition
PFAS signature (concentrations decrease in seeps more distant from the Site). Accordingly, the
offsite seep data will used to build a relationship, i.e., scaling factor, between HFPO-DA and other
PFAS compounds (Figure B6). This scaling factor will be used to estimate mass discharge of Total
PFAS compounds to the Cape Fear River as shown in Equation 4.
Equation 4: Mass Discharge to Cape Fear River
𝑀𝐷௉ி஺ௌ = 𝑀𝐷ுி௉ைି஽஺ × 𝑅
where,
𝑀𝐷௉ி஺ௌ = total mass discharge of PFAS compounds into the river, typically in mg/s;
𝑀𝐷ுி௉ைି஽஺ = total mass discharge of HFPO-DA into the river, typically in mg/s; and
𝑅 = average ratio of measured HFPO-DA to PFAS compounds across the nine offsite seeps.
REFERENCES
ERM, 2018. Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater
Effects. 27 April 2018.
Geosyntec, 2019. Corrective Action Plan. Chemours Fayetteville Works. December 31, 2019.
USGS, 2020. USGS 02105500 Cape Fear River at Wilm O Huske Lock near Tarheel, NC.
Available at: https://waterdata.usgs.gov/nwis/uv?site_no=02105500
Length (m): 903.00
Measurement of Cape Fear River Length at Center Section
Chemours Fayetteville Works, North Carolina
Figure
Notes:HFPO-DA - Hexafluoropropylene oxide dimer acid; or dimer acid; or GenX
µg / m2/yr - micrograms per square meter per year
HFPO-DA deposition model contours for October 2018 from ERM, 2018, Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.
1 0 10.5 Miles
³
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
ite Boundary
40 µg/m2/yr
80 µg/m2/yr
160 µg/m2/yr
320 µg/m2/yr
640 µg/m2/yr B1
Modeled Deposition Contours, October 2018 Scenario
Raleigh, NC August 2020
Length (m): 489.90
Measurement of Cape Fear River Length at Up-River Section 1
Chemours Fayetteville Works, North Carolina
Figure
Notes:HFPO-DA - Hexafluoropropylene oxide dimer acid; or dimer acid; or GenX
µg /m2/yr - micrograms per square meter per year
HFPO-DA deposition model contours for October 2018 from ERM, 2018, Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.
1 0 10.5 Miles
³
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
Site Boundary
Modeled Deposition Contours, October 2018 Scenario
40 µg/m2/yr
80 µg/m2/yr
160 µg/m2/yr
320 µg/m2/yr
640 µg/m2/yr B2August 2020Raleigh, NC
Length (m): 908.05
Measurement of Cape Fear River Length at Up-River Section 2
Chemours Fayetteville Works, North Carolina
Figure
Notes:HFPO-DA - Hexafluoropropylene oxide dimer acid; or dimer acid; or GenX
µg / m2/yr - micrograms per square meter
HFPO-DA deposition model contours for October 2018 from ERM, 2018, Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.
1 0 10.5 Miles
³
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
Site Boundary
Modeled Deposition Contours, October 2018 Scenario
40 µg/m2/yr
80 µg/m2/yr
160 µg/m2/yr
320 µg/m2/yr
640 µg/m2/yr B3August 2020Raleigh, NC
Length (m): 586.39
Measurement of Cape Fear River Length at Down-River Section 1
Chemours Fayetteville Works, North Carolina
Figure
Notes:HFPO-DA - Hexafluoropropylene oxide dimer acid; or dimer acid; or GenX
µg /m2/yr - micrograms per square meter per year
HFPO-DA deposition model contours for October 2018 from ERM, 2018, Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.
Raleigh, NC
1 0 10.5 Miles
³
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
Site Boundary
Modeled Deposition Contours, October 2018 Scenario
40 µg/m2/yr
80 µg/m2/yr
160 µg/m2/yr
320 µg/m2/yr
640 µg/m2/yr B4August 2020
Length (m): 564.68
Measurement of Cape Fear River Length at Down-River Section 2
Chemours Fayetteville Works, North Carolina
Figure
Notes:HFPO-DA - Hexafluoropropylene oxide dimer acid; or dimer acid; or GenX
µg /m2/yr - micrograms per square meter per year
HFPO-DA deposition model contours for October 2018 from ERM, 2018, Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.
Raleigh, NC
1 0 10.5 Miles
³
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Legend
Site Boundary
Modeled Deposition Contours, October 2018 Scenario
40 µg/m2/yr
80 µg/m2/yr
160 µg/m2/yr
320 µg/m2/yr
640 µg/m2/yr B5August 2020
!(
!(
!(
!(
!(
!(
!(
!(!(Cape Fear RiverSEEP-E
SEEP-F
SEEP-G
SEEP-H
SEEP-I
SEEP-J
SEEP-K
SEEP-LSEEP-M
Old Outfall 00
2
Willis Creek
Georgi
a

B
r
a
n
c
h

C
r
e
e
k
Figure
B6Raleigh
³Path: P:\PRJ\Projects\TR0795\Database and GIS\GIS\Baseline Monitoring Workplan\TR0795_Offsite_Seep_Locations.mxd Last Revised: 7/30/2020 Author: jkasunicAugust 2020
Projection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
1,000 0 1,000500 FeetLegend
Observed Seep
Nearby Tributary
Site Boundary
Notes:1. Seep E to M samples were collected where the seeps enteredthe Cape Fear River. Their locations on this figure have beenslightly adjusted to facilitate interpretation so that they do notappear to be in the Cape Fear River.2. The outline of Cape Fear River is approximate and is basedon open data from ArcGIS Online and North CarolinaDepartment of Environmental Quality Online GIS (MajorHydroshapefile).3. Basemap Source: Esri, DigitalGlobe, GeoEye, EarthstarGeographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN,and the GIS User Community
Chemours Fayetteville Works, North Carolina
Southwestern Offsite Seeps Locations
TABLE B1
NET HOURLY HFPO-DA DEPOSITION RATE
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants NC P.C.
Air Loading
(µg/m2)
Air Loading
(ng/m2) Time (year) Time (hour)
Net Hourly Deposition Rate
(ng/m2/hr)
River Sections Within Air
Loading Zones
40 40,000 1 8,760 4.6 Up River Section 2
Down River Section 2
80 80,000 1 8,760 9.1
Up River Section 1
Up River Section 2
Down River Section 1
Down River Section 2
160 160,000 1 8,760 18.3 Center
Up River Section 1
Down River Section 1
320 320,000 1 8,760 36.5 Not used in calculations
640 640,000 1 8,760 73.1 Not used in calculations
Notes:
1. HFPO-DA model values are from ERM (2018). Modeling Report: HFPO-DA Atmospheric Deposition and Screening
Groundwater Effects. 27 April 2018.
2. Air deposition contours are shown in Figures J-2 through J-6.
3.Net hourly deposition rates are used in the mass discharge calculations, Table J5.
Abbreviations:
HFPO-DA: Hexafluoropropylene oxide dimer acid; or dimer acid.
µg/m2: micrograms per meter square.
ng /L: nanograms per liter.
ng/m2/hr: nanograms per meter square per hour.
TR0795 Page 1 of 1 August 2020
APPENDIX C
Supporting Calculations – Onsite
Groundwater Pathway
Appendix C

1 August 2020
APPENDIX C
SUPPORTING CALCULATIONS – ON SITE GROUNDWATER PATHWAY
INTRODUCTION AND OBJECTIVE
Based on the conceptual site model, the Black Creek Aquifer and the Flood Plain deposits at the
riverbank are the primary hydrogeologic units that are potentially in hydraulic connection with the
Cape Fear River. The Cape Fear River stage is lower than the top of the Black Creek Aquifer,
except during peak rainfall or flooding, indicating that the Cape Fear River is a discharge boundary
for the aquifer. Onsite groundwater from the Black Creek Aquifer discharging to the Cape Fear
River is therefore a potential pathway for per- and polyfluoroalkyl substances (PFAS) mass
loading to the Cape Fear River. This pathway was identified as Transport Pathway Number 5 in
the PFAS mass loading design in the. The objective of this appendix is to provide calculations for
estimating PFAS mass loading from onsite groundwater discharge based on calculated PFAS mass
flux for segments of the Black Creek Aquifer along the river frontage.
APPROACH
The PFAS mass loading from onsite groundwater discharge will be estimated as follows:
1. The Cape Fear River frontage will be divided into 8 segments (Figure C1). Each segment
includes at least one groundwater monitoring well that is considered representative of the
Black Creek Aquifer and that is included in the Corrective Action Plan (Geosyntec, 2019b).
2. The thickness of the Black Creek Aquifer (h) will be estimated for each segment based on
the segment length and the cross-sectional area of the Black Creek Aquifer, as determined
by the three-dimensional hydrostratigraphic model of the Site, constructed using CTech’s
Earth Volumetric Studio (EVS) software (Geosyntec, 2019b):
ℎ =
𝐴
𝑙
where h is the Black Creek Aquifer thickness [ft];
A is the cross-sectional area of the Black Creek Aquifer [ft2]; and
l is the segment length [ft].
The EVS model output for each segment is presented in Figure C2.
3. The hydraulic gradient (i) will be derived based on the groundwater level contour map. For
each segment, the gradient will be estimated based on the distance between contour lines
in the vicinity of the river frontage:
Appendix C

2 August 2020
𝑖 =
𝛥ℎ
𝑑
where i is the hydraulic gradient [ft/ft];
Δh is the head difference between two contour lines [ft]; and
d is the estimated distance between the contour lines [ft].
This approach is considered to best represent the likely groundwater fluxes discharging
from the Black Creek Aquifer to the Cape Fear River. Based on hydrographs from wells
along the river presented in Figure C3 hydraulic gradients in the aquifer are relatively
constant over time. With the exception of large changes in the river level (over ten feet),
these wells respond to river level fluctuation in a subdued manner.
4. The hydraulic conductivity (K) will be estimated for each segment using the results of slug
tests conducted for select monitoring wells representative of the Black Creek Aquifer. The
range of slug test results for LTW-02, LTW-03, and LTW-05 will be used to determine the
hydraulic conductivity of segments 3,4, and 7, respectively since these wells are located in
the corresponding segments. For other segments where no slug tests are performed, the
range of slug test results for the entire Black Creek Aquifer will be used to determine the
hydraulic conductivity. In both cases, the minimum hydraulic conductivity and the
geometric mean hydraulic conductivity will be used to calculate a range of mass flux
values. Table C1 provides the results of the slug tests and the minimum and geometric
mean hydraulic conductivities for each segment.
5. The total PFAS concentration for each segment will be determined based on grab samples
collected from monitoring wells within a given monitoring period. For segments with two
wells, the average PFAS concentration will be used.
6. Mass flux for each segment, representing the PFAS mass loading to the river from
groundwater, will be determined as follows:
𝑄 = 𝑙ℎ𝐾𝑖𝐶𝑓
where Q is the mass flux [mg/s];
l is the segment length [ft];
h is the Black Creek Aquifer thickness [ft];
K is the hydraulic conductivity of the aquifer [ft/s];
i is the hydraulic gradient [ft/ft];
C is the total PFAS concentration [ng/L]; and
Appendix C

3 August 2020
f is the conversion factor between cubic feet and liters and between ng and mg.
7.The total mass flux for the groundwater pathway will be calculated as the sum of the
individual mass flux results for the 8 segments.
POTENTIAL FUTURE METHODOLOGY MODIFCATIONS
Periodically, adjustments to this calculation methodology may be required based on changes in
conditions or refinement of Site knowledge.
REFERENCES
Geosyntec, 2019. Corrective Action Plan. Chemours Fayetteville Works. December 2019.
PPPPPPPPPPPPPPPP
!'A
!'A
!'A
!'A
!'A
!'A
!'A
!'A
!'A
!'A
CapeFear
RiverSeep D
Old Outfall 002
Seep C
Seep B
Seep A
Willis Creek
PIW-1D
LTW-03
PIW-1S
PIW-7S
LTW-02
LTW-05
PIW-7D
PW-11
PZ-22
PIW-3D
Segment 1
Segment 2
Segment 3
Segment 4
Segment 5
Segment 6
Segment 7
Segment 8
³Path: P:\PRJ\Projects\TR0795\Database and GIS\GIS\Baseline Monitoring Workplan\TR0795_Black CreekAquiferSegmentsforGroundwaterPathway.mxd Last Revised: 7/29/2020 Author: jkasunicProjection: NAD 1983 StatePlane North Carolina FIPS 3200 Feet; Units in Foot US
Black Creek Aquifer Segmentsfor Groundwater Pathway
Chemours Fayetteville Works, North Carolina
Figure
C1RaleighAugust 2020
1,000 0 1,000500 Feet
Notes:
1. Due to the scale of the map, pairs of wells that are in close proximity have been offset for visibility. Therefore, the placement of these wells on this map do not
reflect their true geographic coordinates.2. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of Environmental QualityOnline GIS.3. Basemap source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.
Legend
!'A Surficial Aquifer
!'A Floodplain Deposits
!'A Black Creek Aquifer
Observed Seep
Nearby Tributary
Site Boundary
Transect Line
0.5 0 0.50.25 Miles
³
FigureC2Cross-Sections Along Cape Fear River Transect LineChemours Fayetteville Works, North CarolinaRaleighAugust 2020Elevation (feet NAVD88)50403020100PIW-1S/D-1002505007501,000Elevation (feet NAVD88)50403020100-100250500750PIW-3DLTW-01Elevation (feet NAVD88)50403020100-100250500750LTW-02Segment 1Elevation (feet NAVD88)50403020100-100250500750LTW-03Elevation (feet NAVD88)50403020100-100250500LTW-04PZ-22Elevation (feet NAVD88)50403020100-100250500PIW7S/DElevation (feet NAVD88)50403020100-100250500750Elevation (feet NAVD88)50403020100PW-11-1002505007501,000 1,2501,5001,7502,000Segment 2Segment 3Segment 4Segment 5Segment 6Segment 7Segment 8Units(2)Floodplain DepositsBlack Creek Confining UnitBlack Creek AquiferUpper Cape Fear Confining UnitLegendWell screen(1)Notes:NAVD88 – feet North America Datum of 1988 Vertical Exaggeration = 10x1. Wells are projected onto the cross-section.Segment 1Segment 3Segment 2Segment 4Segment 5Segment 6Segment 7Segment 8Distance Along Transect Line (feet)Distance Along Transect Line (feet)Distance Along Transect Line (feet)Distance Along Transect Line (feet)Distance Along Transect Line (feet) Distance Along Transect Line (feet)Distance Along Transect Line (feet)Distance Along Transect Line (feet)NorthSouthNorthSouthNorthSouthNorthSouthNorthSouthNorthSouthNorthSouthLTW-05NorthSouthCape Fear River
\\projectsitesb.geosyntec.com@SSL\DavWWWRoot\5\FWConsentOrder\Shared Documents\34 - P16 Quarterly Reports\2020 Q1\Report\Appendices\Appendix H - Onsite Groundwater Gradients\[Figure H-4 - Hydrographs.xlsx]FigureH4Hydrograph for Select Onsite Groundwater Monitoring
Wells and W.O Huske Dam
Chemours Fayetteville Works, North Carolina
Figure
C3
Raleigh August 2020
0
10
20
30
40
50
60
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
27-Nov-201828-Dec-201828-Jan-201928-Feb-201931-Mar-20191-May-20191-Jun-20192-Jul-20192-Aug-20192-Sep-20193-Oct-20193-Nov-20194-Dec-20194-Jan-20204-Feb-20206-Mar-20206-Apr-20207-May-20207-Jun-2020W.O Huske Dam River Elevation (ft NAVD88)Groundwater Elevation (ft NAVD88)Date
LTW-01 LTW-02 LTW-05 PIW-1D PIW-2D PIW-3D PIW-4D PIW-7D PIW-7S PIW-8D W.O. Huske Dam
Notes:
ft - feet
NAVD88 - North American Vertical Datum of 1988 NAVD88 - North American Vertical Datum of
1988
TABLE C1HYDRAULIC CONDUCTIVITY RESULTS
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC P.C.
Segment Well Slug Test
Observed
Hydraulic
Conductivity
(ft/sec)
Minimum
Hydraulic
Conductivity
(ft/sec)
Geometric Mean
Hydraulic
Conductivity
(ft/sec)
--BCA-01 T1 2.1E-04 2.1E-04 2.8E-04
T1*3.7E-04
T2 2.2E-04
T2*3.7E-04
T3 2.1E-04
T3*3.6E-04
T4 2.2E-04
T4*3.9E-04
--BCA-02 T1 4.6E-04 3.1E-04 5.4E-04
T1*1.0E-03
T2 4.2E-04
T2*9.1E-04
T3 3.4E-04
T3*7.4E-04
T4 3.3E-04
T4*7.4E-04
T5 3.1E-04
T5*6.8E-04
--BCA-04 T1 1.1E-03 1.1E-03 1.4E-03
T1*1.6E-03
T2 1.1E-03
T2*1.7E-03
T3 1.1E-03
T3*1.6E-03
T4 1.1E-03
T4*1.7E-03
T5 1.2E-03
T5*2.3E-03
3 LTW-02 T1 3.0E-04 3.0E-04 4.0E-04T1*4.8E-04
T2 3.2E-04
T2*4.9E-04T33.1E-04
T3*4.7E-04
T4 3.9E-04
T4*5.5E-04
T5 3.0E-04
T5*4.5E-04
4 LTW-03 T1 6.5E-05 2.00E-05 4.6E-05
T2 2.4E-05
T3 2.6E-05
T4 2.6E-04
T5 2.0E-05
7 LTW-05 T1 2.4E-05 1.8E-05 4.8E-05
T1*8.0E-05
T2 1.8E-05
T2*3.5E-05
T4 7.4E-05
T4*1.3E-04
Remaining
Segments (1, 2, 5, 6,
and 8)
All BCA Wells ----1.8E-05 3.2E-04
Notes
* - Screen length used for aquifer thickness
BCA - Black Creek Aquifer
ft/sec - feet per second
TR0795 Page 1 of 1 August 2020
APPENDIX D
Supporting Calculations –Adjacent and
Downstream Offsite Groundwater
Appendix D
1 August 2020
APPENDIX D
ADJACENT AND DOWNSTREAM OFFSITE GROUNDWATER
This appendix presents the methodology for calculating the PFAS mass discharge from adjacent
and downstream offsite groundwater to the Cape Fear River. PFAS detected in offsite groundwater
originate from aerial deposition which has occurred in all directions from the Site (CAP Geosyntec,
2019g). These aerially deposited PFAS have subsequently infiltrated to groundwater and migrate
towards the Cape Fear River where they lead to upstream, adjacent and downstream offsite
groundwater PFAS mass. The upstream offsite groundwater mass discharge is estimated relatively
simply by using measured river flows and concentrations at River Mile 76 upstream of the Site.
Here, only the upstream offsite groundwater mass discharge is present in the river at this location.
Conversely, the adjacent and downstream offsite groundwater PFAS mass discharge is difficult
to measure directly since many PFAS mass discharges from all other pathways are present in the
river where these offsite groundwater contributions join the river. Additionally, downstream
offsite groundwater has a relatively small component of the Total PFAS mass discharge making
its additional contributions to the total discharge difficult to distinguish from other discharges
already present.
Therefore, since PFAS mass discharge from offsite groundwater upstream, adjacent, and
downstream of the Site follow the same dynamics (deposition, infiltration, migration, discharge)
the adjacent and downstream PFAS mass discharge is scaled from the upstream offsite
groundwater mass discharge estimate. The downstream offsite groundwater loadings are scaled to
the upstream offsite groundwater loadings based on the length of river adjacent and downstream
of the Site known to be in contact with offsite groundwater containing PFAS compared to the
length of the river upstream also in contact with offsite groundwater containing PFAS. The volume
of river flow is assumed to be constant immediately upstream and downstream of the Site for the
purposes of this calculation. This adjacent and downstream offsite mass discharge will be
calculated using Equation 1 below:
Equation 1: Total PFAS Mass Discharge Adjacent and Downstream Offsite Groundwater
𝑀𝐷௔ௗ௝ିௗି௚௪ = ෍൫𝐶௨௣ି௚௪,௜ × 𝑄஼ிோ൯ × 𝑓௔ௗ௝ିௗ
ூ
௜ୀଵ
where,
𝑀𝐷௔ௗ௝ିௗି௚௪ = represents the Total PFAS discharge from adjacent and downstream offsite
groundwater to the Cape Fear River, units in mass per unit volume [ML-3], typically
milligram per second;
i = represents each of the PFAS constituents being evaluated;
Appendix D
2 August 2020
I = represents total number of PFAS constituents included in the summation of Total PFAS
concentrations;
𝐶௨௣ି௚௪,௜ = represents the upstream concentration of each PFAS constituent i from measured
units in mass per unit volume [ML-3], typically nanograms per liter;
𝑄஼ிோ = represents the volumetric flow in the Cape Fear River as reported by the United States
Geological Survey gage at the W.O. Huske Dam, station ID 02105500 with units used in
the equation expressed as volume per time [L3T-1], typically liters per second; and
𝑓௔ௗ௝ିௗ = represents the unitless scaling factor to adjust offsite upstream groundwater mass
discharge to offsite adjacent and downstream mass discharge. Where 𝑓௨௣ି௔ௗ௝ିௗ is
calculated following Equation 2 below:
Equation 2: Offsite Upstream Groundwater to Adjacent and Downstream Offsite Groundwater
Mass Discharge Scaling Factor
𝑓௔ௗ௝ିௗ = 𝑙஼ிோି௔ௗ௝ + 2𝑙஼ிோିௗ
2𝑙஼ிோି
where,
𝑙஼ிோି௔ௗ௝ = represents the length of the Cape Fear River adjacent to the Site (i.e., the east bank
of the Cape Fear River opposite the Site) where PFAS have been detected in offsite
groundwater within one mile of the river.
2𝑙஼ிோିௗ = represents the length of the Cape Fear River downstream of the Site where PFAS
have been detected in offsite groundwater within one mile of the river. This quantity is
multiplied by two (2) as the river has two downstream sides (east and west) from which
groundwater discharge can reach the Cape Fear River (adjacent only has one side, east).
2𝑙஼ிோି௨௣ = represents the length of the Cape Fear River upstream of the Site where PFAS have
been detected in offsite groundwater within one mile of the river. This quantity is
multiplied by two (2) as the river has two upstream sides (east and west) from which
groundwater discharge can reach the Cape Fear River (adjacent only has one side, east).
Figure D1 displays the quantities used in calculating the scaling factor 𝑓𝑎𝑑𝑗−𝑑 on a map of the
Cape Fear River and Table D1 provides a calculation of 𝑓𝑎𝑑𝑗−𝑑.
!5
!5
!5
ChemoursFayettevilleWorks
Tar Heel
Ferry Road
Bridge
CFR-BLADEN
Mile 76
4.5 Miles Downstream of Old Outfall
14.2 Miles Upstream of Site
1.6 Miles Adjacent of Site
Estimated Extents of Offsite Groundwater Contributions to Cape Fear River PFAS Mass Loads
Chemours Fayetteville Works, North Carolina
Figure
D1Raleigh
Path: P:\PRJ\Projects\TR0795\Database and GIS\GIS\Baseline Monitoring Workplan\TR0795_1MileResidentialDetects.mxd; jkasunic; 07/27/2020August 2020
³
2 0 21 Miles
Notes:Basemap sources: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID,
IGN, and the GIS User Community.
Projection: WGS 1984 Web Mercator Auxiliary Sphere; Units in Meter
Legend
Offsite Groundwater Sampling Location with Detected Result
!5 Selected Prior Cape Fear River Sampling Locations
Detected Results within 1 mile of Cape Fear River
Chemours Fayetteville Works
Cape Fear River
TABLE D1
ADJACENT AND DOWNSTREAM OFFSITE GROUNDWATER MASS DISCHARGE SCALING FACTOR
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC, PC
Item Value Unit
𝑙_(𝐶𝐹𝑅−𝑢𝑝) 14.2 miles
𝑙_(𝐶𝐹𝑅−𝑎𝑑𝑗) 1.7 miles
𝑙_(𝐶𝐹𝑅−𝑑) 4.5 miles
𝑓_(a𝑑𝑗−𝑑) 0.38 --
Calculation Notes for Offsite Upstream Groundwater to Adjacent and Downstream Offsite Groundwater Mass Discharge Scaling Factor
𝑓௔ௗ௝ିௗ = 𝑙஼ிோି௔ௗ௝ + 2𝑙஼ிோିௗ
2𝑙஼ிோି௨௣
where,
𝑓௔ௗ௝ିௗ =represents the unitless scaling factor to adjust offsite upstream groundwater mass discharge to adjacent and downstream offsite
groundwater mass discharge.
𝑙஼ிோି௔ = represents the length of the Cape Fear River adjacent to the Site (i.e. the east bank of the Cape Fear River opposite the Site) where
PFAS have been detected in offsite groundwater within one mile of the river.
2𝑙஼ிோିௗ = represents the length of the Cape Fear River downstream of the Site where PFAS have been detected in offsite groundwater within one
mile of the river. This quantity is multiplied by two (2) as the river has two downstream sides (east and west) from which groundwater discharge
can reach the Cape Fear River (adjacent only has one side, east).
2𝑙஼ிோି௨௣ = represents the length of the Cape Fear River upstream of the Site where PFAS have been detected in offsite groundwater within one
mile of the river. This quantity is multiplied by two (2) as the river has two upstream sides (east and west) from which groundwater discharge can
reach the Cape Fear River (adjacent only has one side, east).
TR0795 Page 1 of 1 August 2020