OFFSITE SCREENING LEVELEXPOSURE ASSESSMENT OF SITEASSOCIATED PFAS - WORKPLAN

Chemours Fayetteville Works

Prepared for

The Chemours Company FC, LLC
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

Prepared by
Geosyntec Consultants of NC, PC
2501 Blue Ridge Road, Suite 430
Raleigh, NC 27607

Project Number TR0795
July 2019

TABLE OF CONTENTS
1INTRODUCTION ................................................................................................ 1
1.1 SLEA Objectives ......................................................................................... 2
1.2 Overview of HFPO-DA ............................................................................... 3
1.3 Document Organization............................................................................... 32

BACKGROUND .................................................................................................. 5
2.1 Site Description ........................................................................................... 5
2.2 Site History .................................................................................................. 5
2.3 Climate......................................................................................................... 5
2.4 Topography.................................................................................................. 6
2.5 Cape Fear River and Tributaries .................................................................. 6
2.6 Geology and Hydrogeology......................................................................... 6
2.7 Fate and Transport Considerations .............................................................. 93

CONCEPTUAL EXPOSURE MODEL ............................................................... 9
3.1 Offsite Receptor Populations ..................................................................... 10
3.2 Environmental Exposure Media and Routes ............................................. 10
3.3 Complete Exposure Pathways ................................................................... 13

4

IDENTIFICATION OF OFFSITE EXPOSURE UNITS ................................... 135ENVIRONMENTAL DATASETS .................................................................... 15
5.1 Soil ............................................................................................................. 15
5.1.1 Surface Soil ................................................................................... 15
5.1.2 Subsurface Soil ............................................................................. 16
5.2
5.3

Groundwater .............................................................................................. 16
Surface Water ............................................................................................ 18
5.3.1 Previous Surface Water Sampling ................................................ 18
5.3.2 Proposed Surface Water Sampling................................................ 19

5.4
5.5

Fish ............................................................................................................ 21
Homegrown Fruits and Vegetables ........................................................... 22

6

EXPOSURE POINT CONCENTRATIONS ...................................................... 23

7

INTAKE CHARACTERIZATION .................................................................... 25
7.1 Intake Equations and Inputs ...................................................................... 25
7.2 Intake Characterization Results ................................................................. 25

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TABLE OF CONTENTS (CONTINUED)
8

PROVISIONAL HAZARD CHARACTERIZATION....................................... 25
8.1 Reference Dose .......................................................................................... 26
8.2 Route-Specific Hazard Estimates .............................................................. 26
8.2.1 Ingestion ........................................................................................ 26
8.2.2 Dermal ........................................................................................... 26
8.3

Hazard Characterization Summary ............................................................ 27

9

UNCERTAINTY ASSESSMENT ..................................................................... 27

10

CONCLUSIONS ................................................................................................ 28

11

REFERENCES ................................................................................................... 29

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LIST OF TABLES
Table 1: Method Table 3+ SOP Analyte List
Table 2: Boundaries and lots encompassed by the Site (to be included in Final SLEA)
LIST OF FIGURES
Figure 1: Site Location
Figure 2: Conceptual Exposure Model
Figure 3: Exposure Units
Figure 4: Offsite HFPO-DA Groundwater Concentrations (2017-2019) (to be includedin Final SLEA)
Figure 5: Local Cape Fear River Surface Water Sampling Program (to be included in
Final SLEA)
Figure 6: River Sampling Diagram
Figure 7: Regional Cape Fear River Surface Water Sampling Program (to be included in
Final SLEA)
LIST OF APPENDICES [TO BE INCLUDED IN FINAL SLEA]
Appendix A: Consent OrderAppendix B: Analytical Data
Appendix C: ProUCL Output
Appendix D: ERM Air Modeling Output
Appendix E: Modeled HFPO-DA Concentrations in Homegrown Produce
Appendix F: Intake Calculations
Table F-1-1

Intake Equations and Assumptions for Residents

Table F-1-2

Intake Equations and Assumptions for Farmers

Table F-1-3

Intake Equations and Assumptions for Gardeners

Table F-1-4

Intake Equations and Assumptions for Recreationalists

Table F-1-5

Intake Equations and Assumptions for Anglers

Appendix G: Hazard Calculations
Appendix H: Fish and Produce Ingestion Studies

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LIST OF ABBREVIATIONS
ADI

Average Daily Intake

BAF

Bioaccumulation Factor

BCF

Bioconcentration Factor

bgs

Below Ground Surface

Chemours

The Chemours Company FC, LLC

CFPUA

Cape Fear Public Utility Authority

CFRW

Cape Fear River WatchCY

Calendar Year

DEQ

Department of Environmental Quality

DHHS

Department of Health and Human Services

DuPontE.I. du Pont de Nemours and Company

EPC

Exposure Point Concentration

EU

Exposure Unit°F

Degrees Fahrenheit

GI

Gastrointestinal

HDPE

High-Density Polyethylene

HFPO-DA

Hexafluoropropylene Oxide Dimer Acidkm

Kilometer

Kow

Octanol-Water Partition Coefficient

Kuraray

Kuraray America Inc.

ISM

Incremental Sampling Methodology

mg/kg-day

Milligram(s) per Kilogram of Body Weight per Day

mg/L

Milligram(s) per Liter

MSL

Mean Sea Level

NC

North Carolina

ng/LNanograms per Liter

NPDES

National Pollutant Discharge Elimination System

PFAS

Perfluoroalkyl and Polyfluoroalkyl Substances

pKa

Acid Dissociation ConstantOffsite SLEA Workplan

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LIST OF ABBREVIATIONS (CONTINUED)
PPAPolymer Processing Aid

PVF

Polyvinyl Fluoride

RfDd

Dermal Reference Dose

RfDo

Oral Reference DoseRM

River Mile

Site

Chemours Fayetteville Works Plant

SLEA

Screening Level Exposure Assessment

SOP

Standard Operating Procedure

UCL

Upper Confidence Limit on the MeanUF

Uncertainty Factor

USEPA

United States Environmental Protection Agency

USGS

United States Geological Survey

WET

Whole Effluent Toxicity

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1

INTRODUCTION

Geosyntec Consultants of NC, PC (Geosyntec) has prepared this Offsite Screening Level
Exposure Assessment (SLEA) of Site-Associated PFAS Workplan for The Chemours
Company FC, LLC (Chemours) for the Fayetteville Works facility in Bladen County,
North Carolina. The purpose of the SLEA described in this workplan is to estimate
potential offsite human exposures to historically-deposited, Site-Associatedperfluoroalkyl and polyfluoroalkyl substances (PFAS) using regional 1 concentrations ofSite-Associated PFAS compounds in environmental media (e.g., soil, groundwater,
surface water) and biota (e.g., fish) in the vicinity of the Site. The SLEA will focus on
hexafluoropropylene oxide dimer acid (HFPO-DA 2) while also estimating human
exposures to the 19 other Site-Associated PFAS presently capable of being analyzed
using the Table 3+ standard operating protocol (SOP) method. The Site-Associated PFAS
that will be considered are listed in Table 1. The SLEA will also present the results of ahazard characterization for HFPO-DA based on intakes quantified in the SLEA and theNorth Carolina Department of Health and Human Services (NC DHHS) 2017 draft oralreference dose (RfDo).
The SLEA is being performed to support the Groundwater Corrective Action Plan (CAP)
required by Paragraph 16 and components of the On and Offsite Assessment required in
Paragraph 18 of the executed Consent Order (CO) entered into court on February 25,
2019 and signed by Chemours, the North Carolina Department of Environmental Quality(NCDEQ), and the Cape Fear River Watch (CFRW).
Paragraph 16, requires the submission of a CAP by December 31, 2019 for onsite andoffsite groundwater. By estimating offsite exposures to historically-deposited, SiteAssociated PFAS, and hazard to offsite receptors associated with historically-deposited
HFPO-DA, this SLEA will inform and support corrective action selection.
The focus of the SLEA is on exposures to historically-deposited, Site-Associated PFAS
that may be present offsite, which may inform the groundwater CAP. Additionally,
historically-deposited PFAS are selected as the focus since Chemours is taking action to
reduce air emissions of PFAS from the facility, including installation of a thermaloxidizer by December 31, 2019 that will control all PFAS from routed process streams at
an efficiency of 99.99%. This is relevant since offsite, Site-Associated PFAS are believed
to primarily originate from aerial deposition stemming from site emissions, as will be

1

PFAS concentrations and exposures are characterized herein as “regional” on the basis that they do not
represent conditions at a specific point of exposure (e.g., in an individual yard or from a specific drinking
water well) nor do they represent exposure potential for a specific receptor (e.g., a resident on a specificproperty).
2
HFPO-DA is also referred to as GenX.

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analyzed in the On and Offsite Assessment report due September 30, 2019. Based on this,the present concentrations of offsite PFAS are expected to diminish over time and current
conditions should represent the highest expected concentrations in receiving media going
forward. Soils may have received historical releases from facility operations through air
deposition. In turn, Site-Associated constituents in soil may be contributed to
groundwater through infiltration of the vadose zone. With a reduction in air emissions,associated soil and groundwater concentrations will attenuate over time.
This SLEA will consider relevant exposure scenarios under future potential conditions
where Consent Order air emission reduction targets have been achieved. The SLEA will
be completed by December 31, 2019 and is presently planned to be provided
simultaneously to NCDEQ and CFRW with the Corrective Action Plan submission due
on December 31, 2019.
1.1

SLEA Objectives

The objectives of the SLEA are as follows:
1. Develop representative exposure point concentrations (EPCs) for HFPO-DA andthe 19 other Site-Associated PFAS in offsite environmental media.
2. Develop estimates of average intake of HFPO-DA and other Site-Associated
PFAS from relevant exposure pathways for potential human receptor populationsin the vicinity of the Site.
3. Develop estimated ranges of potential associated human health hazard, predicatedon intake estimates by pathway and receptor population 3.
4. Identify and evaluate uncertainties associated with limitations in environmental
data, and exposure assumptions in the context of the results of the SLEA intake
and hazard characterizations to support defensible site and risk management
decision-making.
The methodology used in this assessment is consistent with North Carolina risk
assessment practices and the United States Environmental Protection Agency’s (USEPA)
Guidelines for Exposure Assessment (USEPA, 1992) and Draft Guidelines for Human
Exposure Assessment (USEPA, 2016).

3

The SLEA Hazard Characterization will use the draft RfDo developed by the NC DHHS (2017), which
underpins the State’s provisional health goal for HFPO-DA in drinking water. The SLEA Uncertainty
Assessment will evaluate the implications for use of alternate toxicity criteria, such as the probabilistic
RfDo developed by Thompson, et al. (2019) and the USEPA’s draft RfDo (USEPA, 2018a). See Section
8.1 for further discussion.

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1.2

Overview of HFPO-DA

HFPO-DA is a man-made chemical produced at the Chemours Fayetteville Works Site.
The HFPO-DA compound is a six carbon, branched PFAS molecule that contains an etherbond (i.e., an oxygen atom linking two carbon atoms). HFPO-DA 4 is a clear, colorless
liquid completely miscible with water (i.e., infinite solubility in surface water,
groundwater, rainwater, leachate) and low octanol-water partitioning capacity (estimatedKow 1.3 – 2.0) 5. Under normal environmental conditions, HFPO-DA exists as an anionicacid (2.8 acid dissociation constant [pKa]) 6 (Hoke et al., 2016). Biodegradability test data
(DuPont-A080558; Kaplan, 2010) indicate HFPO-DA is not readily biodegradable, witha half-life in soil, water, air, and sediment greater than 6 months (USEPA, 2018a). As
such, HFPO-DA is expected to be relatively stable and persistent in the environment, andresistant to photolysis and hydrolysis (undergoing very slow hydroxyl radical catalyzed
indirect photolysis). Based on a calculated Henry’s Law Constant, partitioning from waterto air may occur as well. When released to air, HFPO-DA is stable and long-range
transport is possible, with deposition augmented by scavenging by water
droplets/precipitation.
Measured bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) suggestthat HFPO-DA has a low potential to bioaccumulate in biota. Multiple fish studies haveconfirmed BCFs of less than 3 and 30, based on exposure to 0.2 and 0.02 milligrams perliter (mg/L), and BCFs of 1 for higher concentrations (DuPont-A080560 2009; Hoke etal., 2016; Goodband, 2019). Log BAFs, calculated for carp, were 0.86 for blood, 0.5 forliver and 0.61 for muscle. Tissue values indicate a BAF of less than 10 (Pan et al., 2017).
1.3

Document Organization

This document presents the approach, data availability and needs, and interpretation
methods to be used in the forthcoming SLEA. This Workplan is organized such that it
represents an outline for the SLEA Report.
This document is organized as follows:

4
HFPO-DA is used here to refer to: 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoic
acid (CASN 13252-13-6), which has the chemical formula C6HF11O3.
5
Kow is the octanol-water partitioning coefficient, the ratio of the equilibrium concentration of a dissolved
chemical in a two-phase system of n-octanol and water. n-Octanol serves as a surrogate to biota lipids andKow values are used as an indicator of a chemical’s tendency to bioaccumulate, or to be taken-up byorganisms from the environment.
6
The pKa predicts that HFPO-DA will be in acid form (as a negative ion, or an anion) at pH levels at or
above a pH of 2.8.

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•

Section 1, Introduction, presents the objectives of the SLEA and provides an
overview of the primary constituents of interest.

•

Section 2, Background, summarizes conditions in offsite areas in the vicinity of
the Site, focusing on those that are relevant to developing a conceptual site modeland conceptual exposure model (CEM).

•

Section 3, Conceptual Exposure Model, identifies potentially complete exposure
pathways by which human receptors may come into contact with HFPO-DA andother Site-Associated PFAS compounds in the environment.

•

Section 4, Identification of Offsite Exposure Units, describes the exposure units
for evaluation in the SLEA and their rationale for identification.

•

Section 5, Environmental Datasets, summarizes the existing Site data and, whereapplicable, describes the sampling and analysis methods for additional datacollection.

•

Section 6, Exposure Point Concentrations, describes how existing data and datacollected per this Workplan will be used to quantify potential human exposure.

•

Section 7, Intake Characterization, summarizes the methods for quantifying
human exposure. In the SLEA Report, this section will be expanded to present thecalculated intakes.

•

Section 8, Provisional Hazard Characterization, will present a description of themethods and toxicological criteria used to derive the set of estimated humanhealth hazard quantitative point estimates for relevant populations and associatedcomplete exposure pathways in the SLEA.

•

Section 9, Uncertainty Assessment, preliminarily identifies key uncertainties
anticipated in the SLEA, which will be updated and expanded upon as the SLEA
proceeds.

•

Section 10, Conclusions, is beyond the scope of the Workplan but serves as place
holder for the forthcoming SLEA Report.

•

Section 11, References, presents the references used in the development of thisWorkplan.

As indicated above, several of the sections will be expanded to present the findings offield sampling and analysis and data interpretation proposed herein. It should be notedthat the Appendices listed in the Table of Contents are not included herein but will be
included in the SLEA Report.

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2

BACKGROUND

The following section describes the physical setting and operational history of the Site,
as well as fate and transport considerations for HFPO-DA.
2.1

Site Description

The Site is located within a 2,177-acre property at 22828 NC Highway 87, approximately
15 miles southeast of the city of Fayetteville, NC along the Bladen-Cumberland county
line. Figure 1 presents an overview of the Site. The Site is bounded by NC Highway 87
to the west, Cape Fear River to the east, and by undeveloped areas and farmland to thenorth and south. Willis and Georgia Branch Creeks, which are tributaries of the Cape Fear
River, are located near the northern and southern property boundaries respectively, with
the Georgia Branch Creek being offsite for its entire course (Geosyntec, 2019a).
2.2

Site History

The Site property was originally purchased by E.I. du Pont de Nemours and Company(DuPont) in 1970 and the first manufacturing area was constructed shortly thereafter. A
former manufacturing area used to produce nylon strapping and elastomeric tape was soldin 1992. DuPont sold its Butacite® and SentryGlas® manufacturing units to Kuraray
America Inc. (Kuraray) in June 2014 and subsequently spun off its specialty chemicals
business into Chemours in July 2015. Presently, the Site consists of five manufacturing
areas used to produce plastic sheeting and resin, fluorochemicals, fluoropolymer sheeting
and resin, and intermediates for plastics manufacturing (Parsons, 2014). The five
manufacturing areas shown in Figure 1 include: Chemours Monomers IXM; Chemours
Polymer Processing Aid (PPA); Kuraray Butacite®; Kuraray SentryGlas®; and DuPont
Company polyvinyl fluoride (PVF) resin manufacturing unit. In addition to the
manufacturing operations, Chemours operates two natural gas-fired boilers and awastewater treatment plant for the treatment of sanitary wastewaters from Chemours,
Kuraray, and DuPont and process wastewaters from Kuraray and DuPont (Geosyntec,
2019a). Hazardous waste generated during manufacturing activities are managed at theHazardous Container and Storage Area prior to shipment offsite for treatment, disposal,
or recycling (Parsons, 2014).
2.3

Climate

The climate in Bladen County is characterized by relatively mild winters, hot summers,
and abundant rainfall. According to the National Weather Service, average monthly
temperatures range from a high of 91 degrees Fahrenheit (°F) in July to a low of 33°F in
January. Average monthly rainfall ranges from a high of 5.92 inches in July to a low of
2.65 inches in December (Parsons, 2014).

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2.4

Topography

The developed portion (manufacturing area) of the Site is located on a relatively flat
topographic plateau at an approximate elevation of 145 feet above mean sea level (MSL)
and approximately 70 feet above the Cape Fear River floodplain. Surface topography
generally remains flat to the west with a gentle increase of about 5 feet to a topographic
divide near NC Highway 87. However, ground surface elevations decrease from thetopographic plateau at the manufacturing area towards the Cape Fear River to the east as
well as its tributaries, Willis Creek to the north and Georgia Branch Creek to the south.
Topographic relief from the main manufacturing area decreases by approximately 100
feet in elevation towards the Cape Fear River bank to the east. Inclined topographic relief
combined with overland flow and groundwater seeps have created natural drainage
networks into the Cape Fear River (Geosyntec, 2019a).
2.5

Cape Fear River and Tributaries

The Cape Fear River and its entire watershed are located in the state of North Carolina.
The Cape Fear River drains 9,164 square miles and empties into the Atlantic Ocean near
the city of Wilmington, NC. The Site is situated on the western bank of the Cape Fear
River; it draws water from the Cape Fear River and returns over 95% of this water via
Outfall 002 after being used primarily as non-contact cooling water. Two lock and dam
systems with United States Geological Survey (USGS) stream gauges are locateddownstream of the Site: (1) W.O. Huske Lock and Dam, located 0.5 river miles from theSite (USGS 02105500); and (2) Cape Fear Lock and Dam #1, located 55 river miles
downstream (USGS 02105769).
There are three perennial surface water features that are tributaries to the Cape Fear Riverat or adjacent to the Site. To the north of the Site is Willis Creek, in proximity to the water
intake for the Site. To the south of the Site is Georgia Branch Creek which discharges to
the Cape Fear River approximately 7,500 feet south of the W.O. Huske Dam. Now
discontinued, Old Outfall 002 (adjacent to the Site) discharged into the Cape Fear Riverapproximately 1,350 feet south of the W.O. Huske Dam (Geosyntec, 2019a).
Additionally, in January 2019 three groundwater seep features were identified on thehillside leading from the Site to the Cape Fear River. These seeps represent groundwater
exiting the aquifer and forming channelized flows of water to the Cape Fear River.
2.6

Geology and Hydrogeology

The Site is located within the Coastal Plain Physiographic Province of North Carolina.
The Coastal Plain Physiographic Province extends from the Fall Line, a sinuous anderosionally-defined boundary separating the metamorphic and igneous rocks of thePiedmont Province to the northwest, to the present-day coast. The Coastal Plain

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Physiographic Province is characterized by a southeastward thickening wedge of late
Cretaceous to Holocene age sediments that overlie a Paleozoic age crystalline basement.
Based on the geologic map of North Carolina, the Site is underlain by the Black Creek
Formation which ranges in age from early Campanian through early Maastrichtian of theLate Cretaceous epoch (approximately 66 to 84 million years ago). The Black Creek
Formation is divided locally into three sub-units from oldest to youngest: Tar Heel
Formation, Bladen Formation, and Donoho Creek Formation. In general, the Black Creek
Formation is characterized by lignitic clay with thin beds and laminae of fine-grained
micaceous sand as well as thick lenses of cross-bedded sand. The upper portion of theformation may also contain glauconitic, fossiliferous clayey sand lenses (Geosyntec,
2019a).
Based on the lithology logged during Site investigations (Parsons, 2014; Parsons, 2018a;
Parsons, 2019), the Site is underlain by the following hydrogeologic units, listed below
from ground surface to depth:•

A silty sand unit with thin discontinuous interbedded silt/clay lenses, referred toherein as the Perched Zone.

•

A laterally discontinuous, stiff clay lens underlying the Perched Zone. This claylens appears to be limited in lateral extent to the east, north, and south by local
topography and pinches out to the west of the manufacturing area based onlithologic logging and limited geophysical survey. The depth to the top of the claylens is approximately 15 to 18 feet below ground surface (bgs). The clay lensbecomes thinner moving west across the manufacturing area and ranges fromapproximately 1 foot to approximately 19 feet thick.

•Fine- to medium-grained sand interbedded with silt/clay lenses, the saturated
portion of which is herein referred to as the Surficial Aquifer. The sand extends
to a depth of approximately 65 feet bgs (elevation of +80 feet MSL).

•

Beneath the surficial unit is a 7 to 15 foot-thick, stiff, lignitic clay identified as theBlack Creek Confining Unit. This Cretaceous-aged, regionally-extensive unit isencountered at the Site at an approximate elevation of +65 to +77 feet MSL. Whilethe lateral continuity of this unit was verified north-south across the Site throughlithologic borings, the east- west extent of this unit has not been verified throughborings. However, during recent field work described in the Creeks, Old Outfall
002 and Seeps Assessment Workplan (Geosyntec, 2019b), this unit was observed
to outcrop along the bluff face adjacent to the Cape Fear River, and along anembankment near Old Outfall 002 at similar elevations.

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•

Beneath the Black Creek Confining Unit is the regionally-extensive Black Creek
Aquifer, which is approximately 8 to 20 feet thick and is encountered at depths
between 80 and 100 feet bgs (elevation of approximately +45 to +65 feet MSL).

•

Beneath the Black Creek Aquifer is a massive dense clay (with minor sandstringers) that has been identified as the Upper Cape Fear Confining Unit. This
unit has not been fully penetrated at the Site.

Hydrostratigraphic units of interest in the vicinity of the Site include a Perched Zone, theSurficial Aquifer, and the Black Creek Aquifer. While the Surficial Aquifer and Black
Creek Aquifer are regionally extensive features, the Perched Zone is limited in extent to
the top of the clay lens that underlies most of the manufacturing area. These
hydrostratigraphic units are described further below:•

Perched Zone – Groundwater in the Perched Zone appears to be controlled by the
topography and lateral limits of the clay lens that underlies most of the
manufacturing area. Historically, groundwater in the Perched Zone appears tohave mainly resulted from: (1) past seepage of water through the bottom of theNorth/South Sediment Basins that are used to settle out solids from Cape Fear
River water; (2) past infiltration of water from the cooling water channel aroundthe Monomers IXM Area; and (3) infiltration of rainfall. The sediment basins andthe cooling water channel were lined in November 2018 as part of the ongoing
Site remedial actions to reduce infiltration to the Perched Zone. Perched Zone
water likely flows in a radial pattern away from a potentiometric high near the
sedimentation basins. Where perched water is present, it is encountered fromapproximately 6 feet bgs at the basins to a depth of approximately 20 feet bgs
along the edges of the Perched Zone west of the basins.

•

Surficial Aquifer – The Surficial Aquifer is encountered at approximately 40 feetbgs and extends to a depth of approximately 65 feet bgs (elevation of
approximately +110 to +80 feet MSL). Groundwater elevations range fromapproximately 100 to 107 feet above MSL in the western areas of the Site toapproximately 93 feet above MSL in the eastern areas of the Site, indicating thatgroundwater flow is generally toward the Cape Fear River. The water level of theCape Fear River is typically near +30 feet MSL, which is lower than the baseelevation of the Surficial Aquifer. This elevation difference suggests that waterfrom the Perched Zone and the Surficial Aquifer will reach the Cape Fear River
from a potential combination of groundwater seepage on the hillslope andsubsequent flow to the Cape Fear River (observed), and potential infiltration to
the Black Creek Aquifer and subsequent discharge to the Cape Fear River.

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•

The Black Creek Aquifer – The Black Creek Aquifer is potentially under semiconfined to confined conditions at portions of the Site where it is separated fromthe overlying Surficial Aquifer by the clay Black Creek Confining unit. As noted
above, the lateral extent of the clay confining unit has not been verified towards
the eastern portion of the Site. Groundwater flow in the Black Creek Aquifer istoward the Cape Fear River. At the Site, only the Black Creek Aquifer is in directconnection to the Cape Fear River with the potential exception of the Surficial
Aquifer during extreme flood events.

Groundwater seeps were observed during recent field work being performed as part of
the Creeks, Old Outfall 002 and Seeps Assessment Workplan (Geosyntec, 2019b).
Groundwater seeps to surface where the Perched Zone, Surficial Zone, and the Black
Creek Aquifer intersect the side of the bluff slope below the Facility and flows towards
the Cape Fear River in a series of naturally-occurring erosional channels. These channels
have been observed to contain a steady flow of water where they intersect groundwater.
The three seeps observed on the eastern bluff adjacent to the Cape Fear River from northto south are named Seep A, Seep B, and Seep C (Geosyntec, 2019a).
2.7

Fate and Transport Considerations

HFPO-DA and other Site-Associated PFAS have been detected in soils onsite, ingroundwater on- and offsite, and in surface water on- and offsite. Site-Associated PFAS
are likely present in offsite soils as well. The On- and Offsite Assessment to be delivered
to satisfy the requirements of Paragraph 18 will characterize Site-Associated PFAS in theenvironment and their present environmental distribution. The SLEA will include asummary of sources, which will be used to inform the development of the CEM[conceptual exposure model].
3

CONCEPTUAL EXPOSURE MODEL

Development of a CEM [conceptual exposure model] is recommended by USEPA(USEPA, 1989) to support interpretation of environmental data and inform sitemanagement decisions. The SLEA CEM identifies potentially complete exposure
pathways by which receptors could come in contact with historically-deposited, SiteAssociated PFAS in environmental media within the offsite Study Area. For an exposure
pathway to be complete, the following five elements are necessary:•a source or release from a source;•

a mechanism of release and transport;•

an exposure medium (i.e., point of contact) for potential receptors;

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•

an exposure route (e.g., ingestion); and,•the presence of a receptor population (e.g., residential adult and child).

If an element of the CEM is missing, the exposure pathway is incomplete. For the
purposes of the SLEA, source and release/transport mechanism(s) for PFAS are presumed
to exist (see Section 2.7). As such, the SLEA will focus on characterizing exposure media,
exposure routes, and human receptors to historically-deposited, Site-Associated PFAS.
Generally, intake of Site-Associated PFAS will only be quantified for complete pathways
but, in some instances for the purpose of informing site management decisions, intake
will also be quantified for pathways that are not reasonably anticipated to be complete(e.g., due to current or planned implementation of institutional controls).
The preliminary human health CEM is diagrammatically presented in Figure 2 and its
elements are described below.
3.1

Offsite Receptor Populations

The Site contains 2,177 acres of relatively flat, undeveloped open land and woodland
bounded by the Cape Fear River on the east, NC Highway 87 on the west, Willis Creekon the north, and farmland on the south (Figure 1). Based on the current Site setting,including surrounding land uses, potential receptors for evaluation in the SLEA and therationale for their inclusion are summarized below.

3.2•

Residents. The nearest residence is approximately 1 km north of Site
manufacturing areas. North and northwest of the Site, several residential
neighborhoods occur within 5 km of the Site.

•

Farmers. Farmers were identified as potential receptors based on the
predominance of agricultural land use to the east, south, and west of the Site.

•

Gardeners. Residents and farmers may garden on their properties.

•

Offsite workers. Although residential and agricultural land uses predominate theareas surrounding the Site, some commercial businesses are also present.

•

Recreational Canoeists/Swimmers. The Cape Fear River may be used forrecreational purposes, including canoeing and swimming.

•

Recreational Anglers. The Cape Fear River may be used for recreational purposes,
including fishing.
Environmental Exposure Media and Routes

The SLEA will focus on evaluating the relative potential for intake from direct andindirect contact with Site-Associated PFAS detected in environmental media from

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historical deposition. Previous environmental investigations have detected Site
Associated PFAS in soil, groundwater, and surface water in the vicinity of the Site andbiouptake of PFAS may potentially also occur. Potential exposure media and routes forevaluation in the SLEA are summarized below. Unless otherwise noted below, these
media-specific complete exposure pathways will be quantitatively evaluated in the SLEA
for relevant receptors. It is important to note that these are hypothetical exposure
scenarios developed to evaluate the potential for exposure; in reality, some (or all) of theassumed exposure pathways may be incomplete for an actual receptor.
•

Offsite Surface Soil. Stack and fugitive emissions to ambient air have resulted inhistorically-deposited PFAS in offsite soils. The projected 99% reduction in
facility-wide air emissions of “GenX compounds” (as defined in the Consent
Order) will significantly reduce continuing contribution to Offsite surface soil andassociated concentrations are expected to attenuate over time. Offsite residents,
farmers, gardeners, and workers are assumed to be directly exposed to surface soil
via incidental ingestion and dermal contact. As described in Section 8, dermal
absorption studies with HFPO-DA indicate exposure via the dermal pathway isunlikely to be significant (DuPont-25292, 2008); as such, dermal exposure tosurface soil will be evaluated qualitatively or semi-quantitatively as part of the
SLEA Uncertainty Assessment. Soil intake by offsite commercial workers is
likely to be lower than that of other offsite populations (e.g., residents, farmers,
and gardeners); therefore, worker exposure to soil will be qualitatively or semiquantitatively evaluated based on the results of receptors with greater exposure
potential.

•

Offsite Subsurface Soil. Site-Associated PFAS present in offsite subsurface soils
originate from aerial PFAS deposition followed by downward infiltration of
PFAS through the vadose zone (unsaturated zone). For most receptors, thepotential for direct exposure to subsurface soil is incomplete and, relative tosurface soil, would likely be insignificant. Surface soil conditions will inform risk
management decisions. As such, direct contact with subsurface soil will be
qualitatively or semi-quantitatively evaluated as part of the SLEA Uncertainty
Assessment.

•

Offsite Groundwater. Site-Associated PFAS present in offsite groundwateroriginate from historically-deposited PFAS which have infiltrated from soils togroundwater. Site-Associated PFAS have been detected in groundwater used for
drinking water by private residences and farms within the vicinity of the Site.
Offsite residents, farmers, gardeners, and workers using groundwater for potablepurposes are assumed to be exposed to historically-deposited PFAS via ingestionand dermal contact. Due to their limited dermal absorption (see Section 5),

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exposure to PFAS in groundwater via dermal contact is considered an
insignificant exposure pathway and, therefore, intake will be qualitatively or
semi-quantitatively evaluated as part of the SLEA Uncertainty Assessment.
Irrigation-related contact represents a significantly lessened degree of exposure
when compared to domestic water use. Thus, irrigation-related exposures will be
qualitatively or semi-quantitatively evaluated as part of the SLEA Uncertainty
Assessment.
•

Surface Water. Site-Associated PFAS present in offsite surface water, excluding
Willis Creek and the Cape Fear River, stem from offsite groundwater transporting
historically-deposited PFAS and subsequent discharge to surface water bodies.
Willis Creek and the Cape Fear River also include contributions from onsite,
direct release sources to soil and groundwater. Recreationalists have the potential
to be exposed to Site-Associated PFAS in surface water (e.g., ponds and creeks
near the Site, Cape Fear River) via incidental ingestion and dermal contact (e.g.,swimming, canoeing). Approximately eight (8) and 55 miles downstream of theSite, respectively, surface water from the Cape Fear River is withdrawn andtreated for use as drinking water at the Bladen Bluffs and Kings Bluff water
treatment facilities. Offsite residents, farmers, gardeners, and workers are
assumed to use Cape Fear River water for potable purposes and, therefore,
assumed to be exposed to Site-Associated PFAS via ingestion and dermal contact.
As with groundwater exposure scenarios, dermal contact intakes for surface water
are insignificant and will be qualitatively or semi-quantitatively evaluated in the
SLEA Uncertainty Assessment. Offsite worker exposure to surface water as
tapwater will also be qualitatively or semi-quantitatively evaluated.

•

Terrestrial Biota. Invertebrates, and other terrestrial biota may potentiallyassimilate PFAS from soil or, in the case of plants, from soil, pore water, and wet
and dry deposited particulates. As such, farmers and gardeners are assumed to beindirectly exposed to Site-Associated PFAS via consumption of plants andlivestock. The SLEA will quantitatively evaluate plant intake using biouptake
models from administrative authority guidance or the primary literature; otherconsumable terrestrial biota will be qualitatively or semi-quantitatively evaluatedas part of the SLEA Uncertainty Assessment.

•

Fish Tissue. Aquatic species in the Cape Fear River and surrounding surface
water bodies (e.g., local ponds and lakes) may assimilate PFAS from sediment or
surface water. As such, recreational anglers are assumed to be indirectly exposed
to Site-Associated PFAS via consumption of fish.

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3.3

Complete Exposure Pathways

Hypothetical receptor-exposure scenarios developed for the SLEA to quantitatively
evaluate intake of historically-deposited, Site-Associated PFAS are summarized below.
As noted above, these exposure pathways are assumed to be complete for the purposes of
the SLEA but some or all exposure pathways may be incomplete for an actual Offsite
receptor.
•

Residents (Adult and Child): Surface soil via incidental ingestion andgroundwater and surface water 7 as tapwater via ingestion.

•

Farmers (Adult and Child): Surface soil via incidental ingestion; groundwater as
tapwater via ingestion; and, aboveground leafy vegetables (e.g., lettuce),
aboveground fruits (e.g., tomatoes), and belowground vegetables (e.g., carrots)
via ingestion.

•

Gardeners (Adult and Child): Surface soil via incidental ingestion; groundwater
as tap water via ingestion; and, aboveground leafy vegetables (e.g., lettuce),
aboveground fruits (e.g., tomatoes), and belowground vegetables (e.g., carrots)
via ingestion.

•

Recreational Canoeists/Swimmers (Adult and Child): Surface water via incidental
ingestion.

•

Recreational Anglers (Adult and Child): Fish tissue fillets via ingestion.

Additionally, the SLEA Uncertainty Assessment will include a qualitative or semiquantitative evaluation of Site-Associated PFAS intake for: (i) direct contact with
subsurface soil by residents, farmers, and gardeners; (ii) use of groundwater as irrigationwater by farmers and gardeners; (iii) consumption of livestock by farmers; (iv) directcontact with surface soil and use of groundwater and treated surface water as tapwater by
offsite workers; and (v) dermal contact with soil, groundwater, and surface water by
relevant receptors.
4

IDENTIFICATION OF OFFSITE EXPOSURE UNITS

The selection of exposure units (EUs) for evaluation in the SLEA is premised on theconcept that concentrations in environmental media are likely to attenuate with distancefrom the Site, particularly for groundwater and soil which are the primary offsite exposure
media. As such, the offsite study area was conceptualized as three concentric circles
surrounding the Site that correspond to radial distances of 2.5, 5, and 10 km. These

7

Stemming from Bladen and Kings Bluff Cape Fear River intakes and water treatment facilities.

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concentric circles were then bisected north-to-south and east-to-west to subdivide theoffsite study area into northeast, southeast, southwest, and northwest quadrants.
Additionally, the northeast direction quadrant corresponds to the dominant wind direction(ERM, 2018) and the EU that comprise this quadrant (EUs 1, 5, and 9) capture the areasof likely highest historical aerial deposition to soil. Therefore, as shown in Figure 3, theupland EUs for evaluation in the SLEA are:•EU1: 2.5-km radius, northeast;•

EU2: 2.5-km radius, southeast;•

EU3: 2.5-km radius, southwest;•

EU4: 2.5-km radius, northwest;•

EU5: 5-km radius, northeast;•

EU6: 5-km radius, southeast;•

EU7: 5-km radius, southwest;•

EU8: 5-km radius, northwest;•

EU9: 10-km radius, northeast;•

EU10: 10-km radius, southeast;•

EU11: 10-km radius, southwest; and•EU12: 10-km radius, northwest.

The Cape Fear River was also subdivided into several EUs, where:•

EU13: upstream locations;•EU14: Site-adjacent locations;•EU15: downstream location at Bladen Bluffs; and•EU16: downstream location at Kings Bluff.

Depending on the outcomes of access agreements currently being negotiated, two lakes /ponds located in the vicinity of the Site may be designated as additional SLEA EUs.
For each upland EU (EU1 through EU12), exposure to surface soil, groundwater (astapwater), and produce will be quantitatively evaluated. For each Cape Fear River EU
and the two Lake EUs (as yet undefined), exposure to surface water will be quantitatively
evaluated. Fish tissue consumption will be quantitatively evaluated at EU13, EU14, andEU15. Fish tissue consumption at EU16 (55 miles downstream) will be qualitatively or
semi-quantitatively evaluated based on the findings at EU15 (8 miles downstream).

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Additionally, treated surface water at EU15 and EU16 will be quantitatively evaluated as
tapwater.
5

ENVIRONMENTAL DATASETSThis section describes existing datasets and additional data to be collected in the summerof 2019 to support derivation of EPCs for the SLEA. Analytical datasets for evaluationin the SLEA will be presented in Appendix B of the SLEA.
5.1

Soil

The SLEA will characterize Site-Associated PFAS intake from soil using data collected
as described in this section. Chemours’ contractors will conduct the offsite soil sampling.
The goal of the soil sampling investigation is to characterize regional soil conditions insurficial and subsurface depth intervals for each of the 12 EUs, defined in Section 4(Figure 3). The EUs are arrayed by quadrant and proximity, extending to a distance of
10 km from the Site such that they range in size and include units that are very large (e.g.,
EUs 9, 10, 11, and 12).
5.1.1

Surface Soil

Surface soil is defined as 0 to 6 inches below ground surface (bgs). Surface soil sampling
will be conducted according to an incremental sampling methodology (ISM) that is inaccordance with NCDEQ’s recommendations for collecting composite soil samples fromlarge areas without visible contamination. (see Appendix A of the Registered
Environmental Consultant Program, Implementation Guidance (NCDEQ, 2015)). The
ISM employs a systematic composite sampling method and will thereby enable a more
complete assessment of the large study area where discrete sampling is impractical (e.g.,
representativeness, coverage, schedule). The approach will result in EPCs that arecharacteristic of regional conditions and exposures.
The investigation will be organized by EU. Prior to field mobilization, each ISM-based
EU will be gridded via ordinary or area-of-influence kriging to define 30 random
sampling locations, or nodes. Areas that the project team knows to be inaccessible will
be excluded from the grid. Individual sample aliquots will be collected from each of the
30 nodes in a given EU. Aliquots will be collected from the 0 to 6-inches bgs soil depth
using stainless steel bowls and spoons. These aliquots will be homogenized in the fieldand composited into a single sample for laboratory analysis, for a total of 12 surface soil
samples. Sampling locations will be recorded via global positioning system. If samples
are to be collected from a location on private property, the field team will first gain verbal
access consent from the resident or owner of the property. To the best of their ability,
field personnel will collect samples from each of the random nodes identified in theOffsite SLEA Workplan

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planning documents; however, sampling locations may be modified due to accessibility
issues or hazards encountered in the field. Repositioning of planned sample locations will
be marked in the field and recorded via Global Positioning System (GPS) coordinates.
Field personnel will collect quality assurance/quality control samples (i.e., duplicates,
matrix spikes/matrix spike duplicates, and equipment blanks); however, in the interestsof performing this SLEA in a timeframe capable of supporting the development of a CAP
by December 31, 2019 replicate samples will not be collected.
Composited samples will be shipped under chain of custody to a TestAmerica analyticallaboratory for analysis of HFPO-DA and Site-Associated PFAS per the Table 3/3+ SOP.
Where analytical data do not indicate significant variability between EUs, multiple EUs
may be pooled to derive an ancillary line of evidence for exposure.
5.1.2

Subsurface Soil

Subsurface soil is defined as 0 to 4 feet bgs. One subsurface sample (targeting the 3-4 ft
bgs soil horizon) will be collected from each EU to characterize the unsaturated,subsurface soil, for a total of 12 subsurface soil samples. For each EU, the subsurface
sampling location will be selected at random from one of the 30 surface sampling
locations identified in Section 5.1.1. Using a hand auger, field personnel will collect the
samples from approximately 4 feet bgs. Samples will be shipped via chain of custody toa TestAmerica analytical laboratory for analysis of HFPO-DA and Site-Associated PFAS
per the Table 3/3+ SOP (Workplan Table 1). Subsurface soil data may be pooled byquadrant, or in their entirety, to provide a secondary line of evidence to assess leachingpotential for the greater region, and to corroborate trend analyses in the groundwater
empirical dataset.
5.2

Groundwater

The SLEA will use existing offsite groundwater data collected from private residences tocharacterize the spectrum of domestic drinking water intake and use in each of the 12
upland EUs. Offsite groundwater samples have been collected from private residences
prior to the Consent Order and are now also to be collected as part of implementation ofConsent Order Paragraph 21. PFAS analytical groundwater data will be compiled fromthe Environmental Information Management system for raw drinking water samples (i.e.,
mid- and post- filtration results will be excluded) collected from offsite residential private
drinking water wells from 2017 to 2019. Offsite private drinking water wells are screenedin both the Surficial and Black Creek Aquifers, based on a review of resident-reported
well depths and offsite geological well records retrieved from www.ncwater.org. There
were 55 wells with lithology and geophysical data available in the vicinity of the Site.
Offsite well data distributions will be examined and reported in the Paragraph 18 On andOffsite Assessment Report submitted by 30 September 2019.

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There are over 1,000 wells represented in the existing dataset and groundwater samplingis ongoing per the requirements of the CO. Additionally, more recent data made available
will be considered within the context of the SLEA; however, no additional groundwater
data collection effort is proposed in this Workplan. Wells were sampled for up to 48
PFAS compounds using various analytical laboratories and methods (note, not all
analytes were sampled at each well). The locations of all offsite groundwater wells withposted HFPO-DA concentrations are presented on Figure 4. HFPO-DA results were
mapped for presentation because this analyte was analyzed most frequently.
Only the most recent sampling data collected from each well will be used in the exposure
assessment. Data will be censored for the most recent date sampled for each location/SiteAssociated PFAS analyte pair. Where duplicate data exists for a well/analyte pair (e.g.,both primary and field duplicate sample collected), the highest concentration result will
be retained for analysis. Where both 2017 and 2019 data exist for an analyte/well pair,the values may be compared to assess temporal changes in concentration.
The sampling data from individual wells will be pooled for each EU to derive EU-specific
EPCs for each Site-Associated PFAS constituent. ProUCL Version 5.1 (USEPA, 2015a)
will be used to calculate the mean, maximum, and 95% UCLs for use as EPCs for eachupland EU. Where datasets for an EU contain enough 2018 and 2019 data points tocalculate the UCLs, 2017 data may be eliminated from the dataset so the EPCs represent
most recent conditions. Only analytes included in the Table 3+ SOP (Table 1) will be
evaluated. Where applicable, multiple EUs may be combined to provide ancillary lines
of evidence to characterize groundwater conditions from a greater regional perspective.
Groundwater-as-drinking water, via the spectrum of domestic water usage, will beassessed based on available data. As part of the CO implementation, Chemours is required
to offer permanent replacement drinking water (in the form of public water or wholebuilding filtration systems) when private wells have HFPO-DA detected above 140
nanograms per liter (ng/L). When any individual PFAS listed in CO Attachment C,
exceeds 10 ng/L or when total PFAS listed in CO Attachment C exceed 70 ng/L,
Chemours is required to offer residents up to three under-the-sink reverse osmosis
drinking water systems. Chemours is required to offer temporary replacement watersupplies (i.e., bottled water) to residents qualifying for a filtration or reverse osmosis
system until these systems have been provided. The expected order-of-magnitudeconcentration reductions as a result of filtration or reverse osmosis will be addressed
under an assessment of expected future conditions and presented within the context of the
SLEA Hazard Characterization, Uncertainty Assessment, and report conclusions to aid insite and risk management decision criteria.

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5.3

Surface Water

The SLEA will characterize PFAS intake using existing surface water data and additional
samples collected at select locations, as described below. Surface water data will be used
to calculate EPCs for recreational swimming exposure conditions for the Cape Fear Riverand up to two lakes/ponds in the surrounding area. Geosyntec will develop Cape Fear
River EPCs for upstream, Site adjacent, and downstream surface water exposure points
to evaluate recreational exposure and EPCs for post-treatment downstream surface waterto evaluate potable use exposure at Bladen and Kings Bluffs. EPCs representative of local
lakes/ponds (as yet undefined/identified) will be based on new sampling data to becollected by Chemours’ contractors for this SLEA (if access to conduct sampling can beobtained); only recreational exposures (e.g., fishing, swimming) will be evaluated for thelakes/ponds.
5.3.1

Previous Surface Water Sampling

Geosyntec will compile existing surface water data collected from the Cape Fear Riverduring five (5) previous sampling events:•

Local Program surface water sampling (September 2017);•

Local Program surface water sampling (May 2018);•

Regional Program surface water sampling (June 2018);•

Post-Florence surface water sampling (October-December 2018); and•Spring 2019 surface water sampling (February 2019).

Sampling methods for these events are described in detail in the following reports: Cape
Fear River Surface Water Sampling Plan (Parsons, 2017a); Additional Cape Fear River
Surface Water Sampling Plan (Geosyntec, 2018a); Addendum to Additional Cape Fear
River Surface Water Sampling Plan (Geosyntec, 2018b); Post Hurricane Florence
Sampling Plan (Geosyntec, 2018c); and Creeks, Old Outfall 002 and Seeps Assessment
Workplan (Geosyntec, 2019b). Results of these sampling events were reported in: Cape
Fear River Surface Water Sampling Memorandum (Parsons, 2017b); Assessment of the
Chemical and Spatial Distribution of PFAS in the Cape Fear River (Geosyntec, 2018d);
and Post Hurricane Florence PFAS Characterization Report (Geosyntec, 2018e). Thesesurface water sampling events are summarized below.
Local sampling programs conducted by Parsons in September 2017 and May 2018
focused on areas directly upstream, adjacent to, and downstream of the Site (Geosyntec,
2018d). The associated surface water sampling locations along the Cape Fear River
include Cape Fear River-01 (CFR-01) through CFR-09 (Figure 5). At each surface water
sampling location, four samples were collected along a transect to assess the lateral andOffsite SLEA Workplan

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vertical concentration distributions in the river (Figure 6). Samples collected in the
September 2017 and May 2018 events were analyzed for perfluorinated carboxylic acids,
perfluorosulfonic acids, and HFPO-DA (Geosyntec, 2018d).
A regional sampling program was established to characterize PFAS distribution from theconfluence of the Deep and Haw Rivers [River Mile (RM)-0] to the Kings Bluff Intake
Canal, where the City of Wilmington and the Counties of Pender and Brunswick draw
water (RM-132) (Figure 7). A sampling event was conducted under this program by
Parsons in June 2018. A total of 16 surface water samples were collected from discrete
locations along the Cape Fear River. To the greatest extent practicable, samples werecollected from the middle depth of the water column at the thalweg, i.e., the deepest
portion of the river channel (Figure 6). The associated sample names indicate the miles
from the start of the Cape Fear River and are denoted by RM-X. Samples were analyzed
according to Method 8321, Method 537, and Method Table 3 SOP. Some Regional
Program sampling locations are co-located with those from the Local Program sampling
locations, for example RM-66/CFR-01 and RM-76/CFR-05 (Geosyntec, 2018d).
An assessment was conducted in October and December of CY2018 to assess the effectof Hurricane Florence on the distribution of PFAS in the river (Geosyntec, 2018c). As
part of the assessment, the following five (5) surface water samples were collected fromthe middle of the thalweg of the Cape Fear River: three upstream locations (RM-60, CFR03, RM-76) and two downstream locations (RM-83 and RM-132) of the Site. Samples
were analyzed according to Method 537, Method Table 3 SOP, as well as Method Table
3+ SOP at the Chemours Fluoroproduct Analytical Group.
In the spring of CY2019, five (5) additional samples were collected from the middle ofthe thalweg of the Cape Fear River at RM-56, RM-68, RM-76, RM-84 and RM-132 (thelast two locations correspond to the intakes for Bladen and Kings Bluffs, respectively).
Samples were analyzed according to Method 537 Modified and Method Table 3+ SOP.
Finally, additional data from surface/drinking water intakes located at Kings Bluff andBladen Bluffs were obtained from a NCDEQ website 8 and from the Cape Fear Public
Utility Authority (CFPUA) website 9, respectively.
5.3.2

Proposed Surface Water Sampling

The collection of additional surface water samples at locations CFR-04 and CFR-07 is
proposed to expand the dataset for the area adjacent to the Site and, in the case of CFR-07,89https://deq.nc.gov/news/key-issues/genx-investigation
https://www.cfpua.org/692/Drinking-Water-Quality

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to evaluate temporal trends from CY2017 through CY2019 (Figure 5). Four (4) samples
will be collected along an east-west transect as described below (Figure 6):
•

•
•
•

West Sample – located 25% of the distance across the channel from the west shore
at a depth of 1-foot below water surface. This location is closest to the Site because
the Site is on the west side of the Cape Fear River.
Center Top Sample – located in the middle of the channel at depth of 1-foot below
surface.
Center Middle Sample – located in the middle of the channel, halfway between
surface and river bottom.
East – located 25% of the distance across the channel from the east shore at a
depth of 1-foot below surface.

Chemours’ contractors will collect the samples using a peristaltic pump, new dedicatedhigh-density polyethylene (HDPE) tubing, and dedicated silicone tubing for the pumphead at each location. The tubing will be lowered to the specified sampling depth below
the water surface using an anchor weight and the tubing positioned to point upwards.
Surface water will be pumped directly from submerged tubing through a Horiba water
quality meter until turbidity measurements are below 20 nephelometric turbidity units
and all other field parameters (pH, temperature, specific conductivity, dissolved oxygen,oxidation-reduction potential) are stabilized within ±10% over a 5-minute interval. Oncewater passing through the pump head and the readings appear stable, the Horiba will be
disconnected, the tubing cut to provide a new, clean end, and grab samples collected fromthe discharge of the peristaltic pump in new 250-milliliter HDPE bottles. Samples will beshipped on ice via chain of custody for analytical analysis via Method Table 3+ SOP(Table 1).
The above existing and additional surface water data will be compiled into upstream, Siteadjacent, and downstream surface water datasets. Geosyntec will pool data from sampling
locations RM-66/CFR-01 and RM-68 by year to represent upstream conditions.
Similarly, Geosyntec will pool data from CFR-04, CFR-05, CFR-06/RM-76, and CFR07 by year to generate Site adjacent datasets for CY2017, CY2018, and CY2019.
Geosyntec will analyze each Site adjacent dataset for seasonal reductions in PFAS
concentrations as a result of increased flow in the spring, as well as overall trends in PFAS
concentrations. Lastly, Geosyntec will evaluate data from sampling locations RM-84 andRM-132, which correspond to drinking water intakes at Bladen Bluffs and Kings Bluff
respectively, to generate two downstream datasets. Data collected from additional
downstream locations in CY2019 will be excluded from the dataset while publicly
available data from the CFPUA will be incorporated into the corresponding datasets. The
data will be segregated by year and pre- or post-treatment. The pre-treatment dataset will

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be used to assess recreational exposure concentrations. (Post-treatment data will be used
to assess drinking water exposures.) The upstream, Site-adjacent, and downstream pretreatment datasets will be used to assess recreational swimming exposure concentrations
at various points along Cape Fear River.
Geosyntec proposes the collection of surface water samples from two local lakes/ponds
based on gaining access agreements from the owners of the lakes/ponds. If they are
granted access to the lakes/ponds, Chemours’ contractors will collect three (3) randomlylocated surface water samples in each lake/pond. Lake/pond surface water samples will
be collected by lowering the tubing to the approximate middle depth of the surface watercolumn. Samples will be shipped on ice via chain of custody for analysis via Method
Table 3+ SOP (Table 1). The three (3) samples from each lake/pond sets will be pooled
and two sets of EPCs (i.e., one per lake/pond) will be developed representative of the
maximum detected and mean concentrations. Furthermore, these data will be consideredin light of tissue concentrations in fish collected from these same water bodies (described
below).
5.4

Fish

The SLEA will characterize PFAS intake from recreational fish consumption using tissue
samples collected per this Workplan. Chemours’ contractor will conduct the fish tissue
sampling. Fish tissue samples have not previously been collected for the Site. Fish will
be collected from four (4) sampling points within the Cape Fear River: one location
upstream from the Site (RM-68), two locations adjacent to the Site (CFR-06 and CFR07), and one location downstream from the Site (RM-84/Bladen Bluffs). RM-68 is
located approximately 10 miles north of the Site and far exceeds the expected home range
for recreational sport fish targeted by anglers in the Site vicinity (Lewis and Flickinger,1967). CFR-06 and CFR-07 represent points below the Site outfalls, above and below
Huske Dam, respectively (effectively separating sportfish populations). RM-84 is locatedapproximately eight (8) miles downstream of the Site and will be used to assess
attenuation in relation to Site adjacent samples. Two additional water bodies(lakes/ponds, as yet unidentified/undefined), in the vicinity of the Site will be considered
as potential recreational exposure points.
At each sampling location, Chemours’ contractors will attempt to collect enough fish of
the same species, representative of a common recreational species (e.g., large- or
smallmouth bass) and size (consistent with State of North Carolina recreational fishingregulations), to comprise three (3) samples for laboratory analysis. Fish will be collectedby either electrofishing or traditional rod-and-reel methods, depending on local
conditions. During electrofishing, an electric current is transmitted from a submerged
anode to cathode, causing fish that cross the electric field to either be stunned or swim

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toward the anode where they can be caught using a dip net. The efficacy of electrofishingis limited by the extent of the electric field (generally depth), and this method may fail tocapture fish that tend to live below the reach of the electric current. Where this is the case,a rod-and reel method may be necessary to catch deeper-dwelling fish. Fish fillets (i.e.,
muscle tissue) will be preserved on ice and submitted to TestAmerica under chain ofcustody for analysis of HFPO-DA and Site-Associated PFAS per the Table 3/3+ SOP.
Where necessary, fish tissue samples from multiple species (e.g., bass, catfish, panfish)
may be pooled to generate required sample volumes. Fish tissue samples will be used toassess potential intake associated with recreational angler ingestion, thus only
recreational sport fish, per State of NC fishing regulations, will be targeted.
Fish tissue concentrations from the four (4) Cape Fear River sampling locations will becompared to assess location-specific intake potential and system attenuation withincreased distance from source(s). These 12 sample results will also be pooled, and
ProUCL Version 5.1 will be used to derive constituent-specific 95% UCLs for the greater
Cape Fear River.
Fish tissue concentrations from the lakes/ponds will be compared to assess locationspecific intake potential and system attenuation with increased distance from source(s).
The three (3) samples from each lake/pond will also be pooled to develop mean EPCs foreach pond/lake.
Fish tissue concentrations from the Cape Fear River and local lakes/ponds will support
assessment of recreational angler intake.
5.5

Homegrown Fruits and Vegetables

The SLEA will characterize Site-Associated PFAS intake from homegrown produce
using existing air data and soil data collected per this Workplan (see Section 5.2).
Geosyntec will assess the potential exposure from ingestion of homegrown produce bymodeling HFPO-DA concentrations in aboveground leafy vegetables (e.g., lettuce),
aboveground fruits (e.g., tomatoes), and belowground vegetables (e.g., carrots).
Chemours’ contractors will provide wet and dry deposition data as a function of air
modeling output from Site emissions.
Chemours created a regional deposition model for emissions of HFPO-DA from both
point and fugitive sources identified at the Site. The eight (8) sources include the Vinyl
Ethers North Division, Vinyl Ethers South, and PPA Process Stacks and associatedfugitive emissions, as well as the Polymers Process and Semi-Works Process Stacks.
Chemours used the latest version of the regulatory dispersion model and supporting
programs: AERMOD (version 1621r), AERMAP (version 11103), and BPIP (version

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04274), and local meteorological data collected from 2012 through 2016 that was preprocessed for AERMOD by the NCDEQ.
Chemours previously presented the deposition modeling results in the 2018 document,
Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater
Effects, Fayetteville Works Facility, Fayetteville, NC (ERM, 2018). To assist Geosyntec’s
SLEA, this modeling effort was refined to account for further emissions control measures,
including the thermal oxidizer, to achieve a 99% reduction in stack emissions.
Depositional and soil data (Section 5.1.1) will be used to support modeled plantbiouptake, utilizing methodologies presented in USEPA’s Human Health Risk
Assessment Protocol for Hazardous Waste Combustion Facilities (USEPA, 2005a). The
produce exposure assessment is limited to HFPO-DA based on its reliance on thedeposition model. Empirical soil characterization data will also be used to derive othermodel input parameters.

6

EXPOSURE POINT CONCENTRATIONSEPCs will be calculated on an EU-specific basis. When possible, EPCs based on themean, 95% UCL, and maximum detected concentration will be evaluated in the SLEA toprovide a range of potential intake estimates. Mean and UCL concentrations will becalculated using the ProUCL Version 5.1. ProUCL outputs will be provided as
Appendix C to the SLEA Report. The bullets, listed below, discuss media-specificconsiderations for EPC calculation:•

Soil. One surface soil sample comprised of 30 increments will be collected fromeach upland EU. Hence, surface soil EPCs will be equivalent to single sample,
maximum detected concentrations (that functionally represent an EU-wide
average). An assessment of post-abatement, attenuated soil conditions will also
be advanced.

•

Groundwater as Potable Water. There is a large database of groundwater datafrom the offsite study area (over 1,000 wells), particularly for downgradient wells
located north of the Site. Existing groundwater data will be segregated by EU andthe most recent data from each EU will be given preference for inclusion in thedataset to underpin the EPC calculation. A mean, UCL, and maximum EPC will
be developed for each upland EU. An assessment of post-abatement, attenuatedgroundwater conditions will also be advanced.

•

Surface Water for Recreational Use. Surface water EPCs for recreational use
exposure scenarios will be developed for the four (4) Cape Fear River EUs. For

Offsite SLEA Workplan

23

2019.07.19

the one upstream and two downstream EUs, recreational EPCs will be developed
using existing surface water data; pretreatment data will be used for thedownstream recreational use EPCs. Recreational EPCs for the Site-adjacent EU
will be developed from existing data and data collected upstream and downstreamof the Huske Dam in support of the SLEA. Mean, 95% UCL, and maximum EPCs
(where supported by the datasets) will be developed for each surface water EU.
Surface water conditions in two additional surface water bodies (lakes/ponds) will
be assessed for recreational exposure as well. Mean, maximum, and UCL EPCs
will be developed, where defensible (i.e., with sufficient data) in assessment ofthese exposure conditions.
•Surface Water as Potable Water. Surface water intakes for potable use are locatedat the two downstream EUs (RM-84/Bladen Bluffs and RM-132/Kings Bluff).
Existing post-treatment surface water data will be used to develop mean, UCL,
and maximum EPCs for each downstream EU.

•

Fish Tissue. Fish fillet sampling is proposed in support of the SLEA at EU13
(upstream), EU14 (Site-adjacent, with two sample locations), and EU15 (Bladen
Bluffs). Three fish are proposed to be collected at each location. This sample size(n=3) precludes UCL calculation at individual EUs; however, mean andmaximum EPCs will be developed for each sampling location for use in the
SLEA. Note that at the Site-adjacent EU14 locations, fish will be collected fromabove and below the Huske Dam for the purposes of evaluating biouptake andpotentially calculating a Site-adjacent UCL from the proposed six (6) samples.
Fish tissue concentrations (EPCs represented by the maximum detected and mean
concentrations) in two additional lake/pond surface water bodies (as yet
unidentified/undefined) will be characterized and support recreational angler
complete exposure pathways (i.e., ingestion of fish).

•

Produce (e.g., Lettuce, Tomatoes, Carrots). Local, homegrown fruit and vegetablesampling is not proposed at this time. Concentrations of HFPO-DA in lettuce,
tomatoes, and carrots will be modeled from soil EPCs and modeled wet and dry
air depositional rates on an EU-basis. EPCs for aboveground fruits, abovegroundleafy vegetables and belowground vegetables (tubers) will be developed torepresent mean, 95% UCL and maximum projected concentrations for eachupland EU (EUs 1though 12). Modeling inputs and outputs related to the produce
pathway will be presented in Appendix E of the SLEA Report. The SLEA
Uncertainty Assessment will include a discussion of available, localized wet anddry deposition as a secondary line of evidence to characterize homegrownproduce. The Uncertainty Assessment will also address the effects of the model

Offsite SLEA Workplan

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2019.07.19

selection/assumptions and EPC calculation on the overall estimates of intake andhazard.
Pending the results of the EU-specific analysis, additional aggregation of data (i.e., multiEU approach) to reflect larger regional phenomena may be considered in the SLEA.
7INTAKE CHARACTERIZATION

For the SLEA, intake of PFAS will be quantified as an average daily intake (ADI),
expressed in units of milligrams of constituent per kilogram of body weight per day(mg/kg-day). Intake will be calculated for each route and then summed by exposure
medium (e.g., soil, groundwater). Total intake for each receptor from relevant exposure
media identified in this Workplan will also be calculated. For residents, farmers,
gardeners, and recreationalists, two age groups will be considered: a child age 0 to 6 years
and an aggregated, age-adjusted child/adult receptor, reflective of 0 to 26 years of age.
7.1

Intake Equations and Inputs

The equations used to calculate intake are based on USEPA guidance, including the Risk
Assessment Guidance for Superfund (USEPA, 1989); and the Regional Screening Levels
User’s Guide (USEPA, 2019a). Intake assumptions were developed based on USEPA
guidance, including the Human Health Evaluation Manual, Supplemental Guidance:
Update of Standard Default Exposure Factors and associated updates (USEPA, 2014;2015b) and the Exposure Factors Handbook and associated updates (USEPA, 2011;2017; 2018a, b, c; 2019b). Inputs and equations are presented in Appendix F, which will
also be included in the SLEA Report.
7.2

Intake Characterization Results

The SLEA will compare intake estimates across receptors and media and provide a
relative ranking of intake.
8

PROVISIONAL HAZARD CHARACTERIZATION

The intended purpose of the SLEA is to help foster an understanding of which complete
exposure pathways of historically-deposited Site Associated PFAS are likely to be themost significant contributors of overall human exposure on a regional basis. The relative
ranking of exposures resulting from the SLEA will be used to focus future evaluations of
those pathways that will be relevant to informing risk management decisions andexcluding pathways that, albeit potentially complete, are insignificant relative to overall
exposure potential.

Offsite SLEA Workplan

25

2019.07.19

Although the intended objective of the SLEA is to provide a relative ranking of exposure
pathways, the SLEA will provide perspective on the quantitative point estimates ofhazard. There are presently neither federal nor state regulatory standards for HFPO-DA
in water, soil, air, or food. However, a draft RfDo has been developed by the NC DHHS
(DHHS 2017) and this value underpins development of the State’s provisional health goalfor HFPO-DA in drinking water of 140 ng/L (NCDEQ and DHHS, 2018). The DHHSderived RfDo will underpin the quantitative estimates of regional hazard potential
associated with relevant complete human health exposure pathways in the context of the
SLEA.
8.1

Reference DoseA provisional Hazard Characterization will be included in the SLEA. The Hazard
Characterization will be predicated on the current RfDo developed by the NC DHHS,
0.0001 mg/kg-day, which underpins the State’s provisional HFPO-DA health goal of 140
ng/L for drinking water (DHHS, 2017; NCDEQ and NC DHHS, 2018).
A recent study of GenX (Thompson, et al., 2019) has proposed an additional, provisional
RfDo predicated on benchmark dose modeling, considering deterministic andprobabilistic developmental techniques. The probabilistic RfDo of 0.01 mg/kg-day,represents the more conservative value from this study and will be considered within thecontext of the Uncertainty Assessment as a basis for bounding values in critical reviewof the Hazard Characterization.
A draft RfDo for HFPO-DA of 8E-05 mg/kg/day has also been issued by USEPA for
public comment (USEPA, 2018a). The SLEA Uncertainty Assessment will evaluate theimplications for this toxicity criterion, if adopted at the federal level in the future andassess its use to bound risk management decisions.
8.2

Route-Specific Hazard Estimates

8.2.1

Ingestion

The 1E-04 mg/kg-day chronic RfDo, developed by NC DHHS (NCDEQ and NC DHHS,
2018) will be used in the SLEA to assess ingestion-based pathways (soil, drinking water,
surface water, fish, and homegrown fruits and vegetables) to derive a range of hazard
quotients (HQs).
8.2.2

DermalNo dermal toxicity criteria have been developed at the federal or state level. As such, thedermal reference dose (RfDd) necessitate route-to-route extrapolation from the RfDo,
which requires information on gastrointestinal absorption efficiency. Absorption

Offsite SLEA Workplan

26

2019.07.19

efficiency following oral administration is expected to be above 90%. Consistent withUSEPA (2004) dermal risk assessment guidance, based on this high absorption
efficiency, no absorption-based adjustment is used for route-to-route extrapolation.
Therefore, a provisional RfDd is assumed to be equivalent to the NC DHHS RfDo of 1E04 mg/kg-day (DHHS, 2017).
Exposure studies indicate dermal uptake in animals is undetectable at low doses typicalof environmental exposure and human uptake is more than order of magnitude lower than
animal uptake. For human exposures, dermal exposure is expected to be insignificant
relative to ingestion exposure. Therefore, dermal intake will not be quantified as part of
the SLEA. However, the dermal pathway may be further evaluated as part of the SLEA
Uncertainty Assessment.
8.3

Hazard Characterization Summary

In the forthcoming SLEA, this section will present a discussion of relevant estimates ofhuman health hazard, limited to HFPO-DA, by receptor type and pathway (i.e., media
and exposure route). Hazard calculations will be presented in tabular format in Appendix
G of the SLEA Report, with summary tables included as part of the main body of thereport. Hazard estimates for additional Site-Associated PFAS will not be advanced basedon the absence of administrative authority-promulgated toxicological criteria.
Hazard estimates for HFPO-DA will be quantified by dividing the ADI (mg/kg-day) by
the NC DHHS RfDo (mg/kg-day). Hazard estimates will be calculated for each exposure
route and then summed by exposure medium (e.g., soil, tapwater). Total hazards for each
receptor from all relevant exposure media will also be calculated.
9

UNCERTAINTY ASSESSMENTThe SLEA Uncertainty Assessment will discuss uncertainties which are expected to havea material impact on understanding of exposure, the estimates of intake, and quantitative
point estimates of hazard. Uncertainties are inherent in the process of quantifying
theoretical exposure (and hazard) due to the use of environmental sampling results,
assumptions regarding exposure, and the quantitative representation of chemical toxicity.
Analysis of the critical areas of uncertainty in an assessment provides a better
understanding of the quantitative results through the identification of the uncertainties
that most significantly affect the results.
Examples of this source of uncertainty that could affect the results and conclusions of the
SLEA are related to:•Laboratory analytical results and detection capabilities;

Offsite SLEA Workplan

27

2019.07.19

10•

Environmental variability and use of ISM to characterize soil over broad exposureareas;•

EPC calculation methods, including use of modeled values in the absence of
empirical data (e.g., for vegetable EPCs);•

Inclusion/exclusion of insignificant exposure pathways;•

An assessment of upper-bound estimates of contact and intake;•

Future potential exposures given that the current condition is conservative andthat attenuation of concentrations in all contact media is expected over time;•

An assessment of additional lines of evidence in the absence of empirical data
(e.g., using a surface water/fish tissue scaling exercise to estimate fish tissue
concentrations in local lakes/ponds);•

Evaluation of sediment exposures;•

Use of default intake parameters; and•Anthropogenic background contributions.
CONCLUSIONSThe SLEA will present a summary of findings to support defensible risk management
decision making.

Offsite SLEA Workplan

28

2019.07.19

11

REFERENCES

DuPont-25292: E.I. du Pont de Nemours and Company, 2008. Determination of a
Permeability Coefficient (Kp) for H-28308 Using Human and Rat Skin Mounted in an In
Vitro Static Diffusion Cell. Study Completion Date: February 27, 2008.
DuPont-A080558: Du Pont-Mitsui Fluorochemicals Company, Ltd. 2009. Ready
Biodegradability Test of FRD903. Test guideline not identified. Study conducted by
Mitsubishi Chemical Medience Corporation, Yokohama Laboratory, Yokohama, Japan.
Study Completion Date: May 25, 2009.
DuPont-A080560: Du Pont-Mitsui Fluorochemicals Company, Ltd, 2009.
Bioconcentration Study of FRD903 with Carp. Study conducted by Mitsubishi Chemical
Medience Corporation, Yokohama Laboratory, Yokohama, Japan. Study Completion
Date: June 26, 2009.
DHHS (North Carolina Department of Health and Human Services) (2017). DHHS
Drinking Water Advisory Decision Matrix. Presented to the NC SAB December 4, 2017.
Available at: https://deq.nc.gov/news/hot-topics/genx-investigation/secretaries-scienceadvisory-board
ERM, 2018. Modeling Report: HFPO-DA Atmospheric Deposition and Screening
Groundwater Effects. April 27, 2018.
Geosyntec, 2018a. Additional Cape Fear River Surface Water Sampling Plan, Chemours
Fayetteville Works, North Carolina.
Geosyntec, 2018b. Addendum to Additional Cape Fear River Surface Water SamplingPlan, Chemours Fayetteville Works, North Carolina.
Geosyntec, 2018c. Revised- Post Hurricane Florence Sampling Plan, Chemours Facility
Fayetteville Works, North Carolina. October 11, 2018.
Geosyntec, 2018d. Assessment of the Chemical and Spatial Distribution of PFAS in theCape Fear River. September 17, 2018.
Geosyntec, 2018e. Post Hurricane Florence PFAS Characterization. Onsite/Offsite
Surface Water, Groundwater and Soil. April 2019.
Geosyntec, 2019a. Chemours Fayetteville Works Cape Fear River PFAS Mass Loading
Model Scope of Work. April 2019.
Geosyntec, 2019b. Creeks, Old Outfall 002 and Seeps Assessment Workplan. February
12, 2019.

Offsite SLEA Workplan

29

2019.07.19

Goodband, T, 2019. Final Report: 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propionicacid: Bioaccumulation in Common Carp (Cyprinus carpio): Aqueous Exposure.
Chemours Belgium BVBA. March, 2019.
Hoke, R.A., Ferrell, B.D., Sloman, T.L., Buck, R.C., Buxton, L.W., (2016). Aquatic
hazard, bioaccumulation and screening risk assessment for ammonium 2,3,3,3tetrafluoro-2-(heptafluoropropoxy)-propanoate. Chemosphere, 149, 336-342.
Kaplan, M.A., 2010. Letter to the USEPA Office of Pollution Prevention and Toxics re:
TSCA Review. 8EHQ-06-16436/8EHQ-06-16478. 2010.
Lewis, W.M. and Flickinger, S. (1967). Home Range Tendency of the Largemouth Bass
(Micropterus salmoides). Ecology, 48(6). 1020-3.
NCDEQ (North Carolina Department of Environmental Quality), 2015. Registered
Environmental Consultant Program, Implementation Guidance. October 2015.
NCDEQ and NC DHHS, 2018. Secretaries’ Science Advisory Board Review of the North
Carolina Drinking Water Provisional Health Goal for GenX, DRAFT. August 29, 2018.
Pan, Y., Zhang, H., Cui, Q., Sheng, N., Yeung, L., Guo, Y., Sun, Y., and Dai, J. (2017).
First Report on the Occurrence and Bioaccumulation of Hexafluoropropylene Oxide
Trimer Acid: An Emerging Concern. Environmental Science & Technology. August 7
2017.
Parsons, 2014. Final RCRA Facility Investigation Report (Rev. 1). February 2014;
Revised August 2014.
Parsons, 2017a. Technical Memorandum. Cape Fear River Surface Water Sampling Plan.
22 September 2017.
Parsons, 2017b. Technical Memorandum. Cape Fear River Surface Water Sampling
Memorandum. 3 November 2017.
Parsons, 2018a. Focused Feasibility Study Report- PFAS Remediation. February 2018.
Parsons, 2018b. Technical Memorandum. Groundwater Sampling Memorandum. May
2018.
Parsons, 2019. Southeast Perched Zone Investigation Report. March 2019.
Thompson, C., S. Fitch, C. Ring, W. Rish, J. Cullen, and L. Haws. (2019). Developmentof an oral reference dose for the perfluorinated compounds GenX. Journal of Applied
Toxicology. June 18, 2019.
USEPA (United States Environmental Protection Agency), 1989. Risk Assessment
Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part A), Interim

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Final. Office of Emergency
EPA/540/1-89/002, December.

andRemedial

Response,

Washington,

DC.

USEPA, 1992. Guidelines for Exposure Assessment. Risk Assessment Forum,
Washington, DC. EPA/600/Z-92/001, May.
USEPA, 2004. Risk Assessment Guidance for Superfund, Volume I: Human Health
Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment), Final.
Office of Superfund Remediation and Technology Innovation, Washington, DC.
EPA/540/R/99/005, OSWER 9285.7-02EP, PB99-963312. July.
USEPA, 2005a. Human Health Risk Assessment Protocol for Hazardous Waste
Combustion Facilities. September.
USEPA, 2011. Exposure Factors Handbook: 2011 Edition. National Center for
Environmental Assessment, Office of Research and Development, Washington, DC.
EPA/600/R09/052F, September.
USEPA, 2014. Human Health Evaluation Manual, Supplemental Guidance: Update ofStandard Default Exposure Factors. Office of Solid Waste and Emergency Response.
OSWER Directive 9200.1-120, February.
USEPA, 2015a. ProUCL Version 5.1 Technical Guide. Statistical Software forEnvironmental Applications for Data Sets with and without Nondetect Observations.
Prepared by Singh, A. and A.K. Singh. EPA/600/R-07/041, October.
USEPA, 2015b. Frequently Asked Questions (FAQs) About Update of Standard Default
Exposure Factors. OSWER Directive 9285.6-03, February 24, 2015.
USEPA, 2016. Guidelines for Human Exposure Assessment, Peer Review Draft. Risk
Assessment Forum. Washington, DC, January 7.
USEPA, 2017. Update for Chapter 5 of the Exposure Factors Handbook, Soil and Dust
Ingestion. National Center for Environmental Assessment, Office of Research andDevelopment, Washington, DC. EPA/600/R-17/384F, September.
USEPA, 2018a. Public Comment Draft, Human Health Toxicity Values for
Hexafluoropropylene Oxide (HFPO) Dimer Acid and Its Ammonium Salt (CASRN 1325213-6 and CASRN 62037-80-3). Office of Water, Washington, DC. EPA-823-P-18-001,
November.
USEPA, 2018b. Update for Chapter 9 of the Exposure Factors Handbook, Intake of
Fruits and Vegetables. National Center for Environmental Assessment, Office of
Research and Development, Washington, DC. EPA/600/R-18/098F, August.

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312019.07.19

USEPA, 2018c. Update for Chapter 11 of the Exposure Factors Handbook, Intake of
Meats, Dairy Products, and Fats. National Center for Environmental Assessment, Officeof Research and Development, Washington, DC. EPA/600/R-17/485F, April.
EPA, 2019a. Regional Screening Levels (RSLs) for Chemical Contaminants at Superfund
Sites, May. Available at: https://www.epa.gov/risk/regional-screening-levels-rslsgeneric-tables
USEPA, 2019b. Update for Chapter 3 of the Exposure Factors Handbook, Ingestion of
Water and Other Select Liquids. National Center for Environmental Assessment, Officeof Research and Development, Washington, DC. EPA/600/R-18/259F, February.
Sun, M., Arevalo, E., Strynar, M., Lindstrom, A., Richardson, M., Kearns, B., Pickett,A., Smith, C., Knappe, D.R., et al., 2016. Legacy and Emerging Perfluoroalkyl
Substances Are Important Drinking Water Contaminants in the Cape Fear River
Watershed of North Carolina. Environmental Science & Technology Letters, 3(12), 415419.

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32

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TABLESTABLE 1 - Method Table 3+ SOP Analyte List
Chemours Fayetteville Works, North Carolina
Analytical Method

Common Name

Table 3+ SOP

HFPO-DAPEPAPFECA-GPFMOAAPFO2HxAPFO3OAPFO4DA
PMPA
Hydro-EVE Acid
EVE Acid
PFECA B
R-EVE
PFO5DA
Byproduct 4
Byproduct 6
Byproduct 5
NVHOS
PES
PFESA-BP1
PFESA-BP2

Chemical Name
Hexafluoropropylene oxide dimer acid
Perfluoroethoxypropyl carboxylic acid
Perfluoro-4-isopropoxybutanoic acid
Perfluoro-2-methoxyaceticacid
Perfluoro(3,5-dioxahexanoic) acid
Perfluoro(3,5,7-trioxaoctanoic) acid
Perfluoro(3,5,7,9-tetraoxadecanoic) acid
Perfluoromethoxypropyl carboxylic acid
Perfluoroethoxsypropanoic acid
Perflouroethoxypropionic acid
Perfluoro-3,6-dioxaheptanoic acid
R-EVE
Perfluoro-3,5,7,9,11-pentaoxadodecanoic acid
Byproduct 4
Byproduct 6
Byproduct 5
Perflouroethoxysulfonic acid
Perfluoroethoxyethanesulfonic acid
Byproduct 1
Byproduct 2

CASN13252-13-6
267239-61-2
801212-59-9
674-13-539492-88-1
39492-89-2
39492-90-5
13140-29-9773804-62-9
69087-46-3
151772-58-6
N/A
39492-91-6
N/A
N/A
N/A
1132933-86-8
113507-82-7
29311-67-9749836-20-2

Chemical FormulaC6HF11O3
C5HF9O3
C12H9F9O3S
C3HF5O3C4HF7O4C5HF9O5C6HF11O6
C4HF7O3
C8H2F14O4
C8HF13O4
C5HF9O4
C8H2F12O5
C7HF13O7
C7H2F12O6S
C6H2F12O4S
C7H3F11O7S
C4H2F8O4S
C4HF9O4SC7HF13O5S
C7H2F14O5S

Geosyntec Consultants of NC, PC

PQL (ng/L)
TestAmerica
Eurofins Lancaster
2.0
2.0
20
20
2.0
2.0
5.0
5.0
2.0
2.0
2.0
2.0
2.0
2.0
10
10
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0

Notes:
SOP - Standard Operating Protocol
PQL - practical quantitation limit
ng/L - nanograms per liter
Common PFAS MMF, MTP, DFSA, and PPF were excluded from this list due to issues with analytical methods.

2019.07.19

FIGURES

Cape Fear River

Willis Creek Mouth
Site River Water Intake

Seep A

Seep BNC Highway 87
Outfall 002

Seep C

W.O. Huske Dam

Old Outfall Channel Mouth

Path: E:\TR0726\CapeFear_Report_2019\TR0726_SiteFeatures.mxd; JK; 04/10/2019

Georgia Branch Creek Mouth

LegendAreas at Site

Site Features

Chemours Monomers IXMCape Fear River

Chemours PPA

Nearby Tributaries

Dupont / Dow Leased

Observed Seep (Natural Drainage)
Site Drainage Network
Site Boundary

Kuraray America Leased

2,000

1,000

0

2,000 Feet

Site Location
Chemours Fayetteville Works, North Carolina

Former DuPont PMDF Production Area
Wastewater Treatment Plant

Notes:
Basemap Sources: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID,
IGN, and the GIS User Community

FigureRaleigh

July 20191

Manufacturing
Facility
Historical
Emissions &Releases

OffsiteParticulate
Deposition
Infiltration withRain

Surface
Soil [2](0 to 6" bgs)

Volatilization
Dust Emission
BiouptakeSurface Water [6]Dermal Contact [3]P

Outdoor Air

Inhalation [4]--Vegetation [5]Consumption

PM

Consumption--

Consumption(Drinking Water)E

Dermal Contact

E

Inhalation--

Incidental Ingestion

E/P

Dermal Contact [3]E/PConsumptionP

Consumption(Drinking Water)E

Dermal Contact

E

Inhalation--

Indoor Air

Direct Exposure
Bioaccumulation

Aquatic Biota

Water Treatment [7]Volatilization

Indoor Air

Notes:[1] Data Types: E (Existing); P (Proposed); M (Modeled); "--" (Not Applicable)[2] Subsurface soil will be qualitatively/semi-quantitatively evaluated in the SLEA.
[3] Dermal exposure pathways will be qualitatively evaluated in the SLEA. If the ingestion-based results indicate the dermal pathway may affect risk management decisions, a quantitative analysis may be considered.
[4] Soil particulates and vapors in ambient air will not be evaluated in the SLEA as this pathway is unlikely to be significant.
[5] Produce concentrations will be estimated from soil data and deposition rate data.
[6] Based on the chemical characteristics of PFAS, investigation of sediment is not included as part of the SLEA.
[7] Pathway is applicable to downstream surface water sampling stations only (i.e., Bladen and Kings Bluffs).
Complete exposure pathway proposed for quantitative evaluation of potential intake.
Potentially complete pathway with limited potential for intake. Proposed for semi-quantitative/qualitative assessment.

Conceptual Exposure Modelto PFAS Historically Deposited Offsite
Chemours Fayetteville Works, North Carolina

Potentially complete pathway evaluated using a higher-exposure receptor, where:• Worker exposure to soil and tapwater is excluded from quantitative evaluation on the basis that risk management based on residents will be protective of the receptor group.
• Recreationalist exposure to soil is excluded from quantitative evaluation on the basis that risk management based on residents will be protective of the receptor group.
• Angler exposure to surface water is excluded from quantitative evaluation on the basis that risk management based on swimmers and residents, respectively, will be protective of the receptor group.
• Resident, farmer, and gardener fish consumption is excluded from quantitative evaluation on the basis that risk management based on recreational anglers will be protective of these receptor groups.
Incomplete or insignificant exposure pathway; no evaluation or management action is necessary.

Data TypeP

Direct Exposure

Volatilization

Off-site Angler(Adult and Child)

Incidental Ingestion

Homegrown Meat &Dairy
Groundwater[1]

Potential Exposed Human Receptors

Exposure RouteOff-site Recreator(Adult and Child)

Secondary ImpactedMedia

Off-site Commercial
Worker (Adult)

Transport
Mechanism

Off-site Gardener(Adult and Child)

Impacted Media

Off-site Farmer(Adult and Child)Transport
Mechanism

Off-site Resident(Adult and Child)Primary Chemical
SourceFigure2

Raleigh

July 2019

N

10 km

EU12

EU9

5 km
EU5
EU8

2.5 km
EU4

EU1

W

E
EU2

EU3

EU7

EU6

EU11
EU10

S

2

1

2 Miles

Exposure Units

Site Boundary
Notes:
1. Black lines represent cardinal directions(N, E, S, W)
2. EU = Exposure Unit
3. SLEA = Screening Level Exposure Assessment
4. Aerial Photograph provided by ESRI Basemaps 20180

Chemours Fayetteville Works, North Carolina

FigureRaleigh

July 20193

Local River Programs & Additional Sampling

Regional River Program

CenterMiddleWest

CenterTop

Thalweg*,
Middle depth

East

West
(Site side)East

25 % of river width
Sampling Location Selection Rationale:
Assess how concentrations differ across cross-section,
particularly close to Site

East

West
(Site side)*Thalweg: Deepest part of the channel cross section

Sampling Location Selection Rationale:
Assess how concentrations vary along the length of the river. The
majority of flow occurs at the thalweg, which is typically the mostmixed part of river and expected to be representative of average
concentrations.

River Sampling Diagram
Chemours Fayetteville Works, North Carolina

FigureRaleigh

July 20196