2020.03.16_CCO.p12MassLoadingSummaryUpdateNov2019SamplingEvent

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November 2019 Mass Loading Summary Update_March 2020

Memorandum
Date: March 16, 2020
To: The Chemours Company FC, LLC
From: Geosyntec Consultants of NC, PC
Subject: Mass Loading Model Update – November 2019 Sampling Event

INTRODUCTION
Geosyntec Consultants of NC, PC (Geosyntec) has prepared this memorandum for The Chemours
Company FC, LLC (Chemours) for the Fayetteville Works facility, North Carolina (the Site). The
mass loading model was developed (Geosyntec, 2019a) to evaluate contributions of Table 3+
PFAS from various pathways to the Cape Fear River. This memorandum describes the results of
the sampling event that took place on November 12, 2019 to estimate mass loading of Table 3+
per and polyfluoroalkyl substances (PFAS) to the Cape Fear River. As requested by North Carolina
Department of Environmental Quality (NCDEQ) and Cape Fear River Watch (CFRW), the
November event was completed during a rain event. By pathway the mass loads were consistent
with previous events with the exception of Outfall 002, which had higher Table 3+ PFAS loading
due to sampling coincidence with a rain event of 0.33 inches over a 4 hour time period from about
12:20 pm to 4:25 pm. Other site activities investigating total Table 3+ PFAS contributions from
stormwater indicated that total Table 3+ PFAS loads to Outfall 002 are influenced by stormwater
(Geosyntec, 2019b).
RESULTS
During the November 2019 event, two types of Outfall 002 samples were collected: a twenty-four-
hour composite sample which collected water before, during and after the rain event and a grab
sample collected midway through the rain event (Figure 1). Prior dry events used a combination
of 84-hour composite and grab sample data to estimate loadings from Outfall 002 to the Cape Fear
River. For this November 2019 rain event, the 24-hour composite sampler collected an aliquot of
Outfall 002 water once every 30 minutes for a total of 48 aliquots over the 24 hours. Since
stormwater concentrations can be variable over short durations of time, the 24-hour composite
sample was considered to be more representative of loadings to the river during this event than the
grab sample. Accordingly, the composite sample was used to estimate the mass loads of total
Table 3+ PFAS to the river for the November 2019 event.
November 2019 Mass Loading Event Update
March 2020
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November 2019 Mass Loading Summary Update_March 2020

The data used to calculate pathway-specific loadings are described in Table 1, the mass loading
results from this event are presented in Tables 2 and 3, and the analytical data used in the
calculations are provided in Table 4. The estimated loading percentage per pathway are provided
in Table 2 and the estimated load per pathway and in the Cape Fear River are provided in Table 3.
The loads from all pathways (e.g., seeps, onsite groundwater) are generally consistent with the
range of previously reported values. The load from Outfall 002 was higher than prior loads at 8%
due to increased concentrations at Outfall 002 from stormwater (rainfall occurred during four of
the 24 hours over which the composite sample was collected).
The total estimated mass loading to the Cape Fear River on a per pathway basis were higher than
the measured load in the Cape Fear River based on a sample collected at Bladen Bluffs Intake
(Table 3). This discrepancy is likely due to the Bladen Bluffs sample collection preceding the
arrival of stormwater flows from the Site. Bladen Bluffs is approximately 5 miles downstream
from the W.O. Huske Dam (the southern edge of the Site). The Bladen Bluffs sample was taken
during the rainfall period as were most samples onsite. However, based on numerical modeling of
the Cape Fear River, water traveling from the W.O. Huske Dam to the Bladen Bluffs sampling
point is estimated to take 10 hours to arrive. Therefore, stormwater flows from the Site, including
from Outfall 002, had not reached the Bladen Bluffs sampling point when the sample was collected
(see Figure 1).
ADJUSTMENTS TO FUTURE EVENTS AND REPORTING
In future events two adjustments will be made to improve the representativeness of samples
collected. First, composite samplers will be used to collect 24-hour integrated samples from Willis
Creek, all four seeps, Outfall 002, Old Outfall 002 and from the downstream river location at Tar
Heel Ferry Road bridge. The Tar Heel Ferry Road bridge location is approximately 2.1 miles
downstream from the Bladen Bluffs sampling location, i.e. 7 miles downriver from the Site. This
sampling location is suitably far enough downstream of the Site for the water to be well mixed
(see transect sampling reported in the Assessment of the Chemical and Spatial Distribution of
PFAS in the Cape Fear River report [Geosyntec, 2018]). The composite samplers will collect
sample aliquots once per hour. Collecting composite samples from these locations will allow for a
more accurate assessment of loads reaching the river compared to grab samples; composite
samples smooth out potential variability in data when sampling heterogenous and dynamic natural
systems.
The second adjustment will be to use the results of a numerical model of the Cape Fear River to
estimate the arrival times of water passing the Site at the downstream Tar Heel Ferry Road bridge
location. As such, the composite sample at the Tar Heel Ferry Road bridge location will be
collected during a representative interval, to the extent feasible, to account for the arrival times.
November 2019 Mass Loading Event Update
March 2020
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November 2019 Mass Loading Summary Update_March 2020

For example, sample collection at Tar Heel Ferry Road bridge may begin 10 hours later to
sequence collection with when water that left the Site is reaching the downriver sampling location.
Additionally, as described in a response to NCDEQ comments on Paragraph 12 (Geosyntec, 2020),
composite samples will be collected continuously, to the extent practicable, at the Tar Heel Ferry
Road bridge. These composite samples will provide a more continuous record of river total Table
3+ PFAS concentrations and loadings to the Cape Fear River. Using an autosampler will also allow
for an evaluation of seasonal or shorter temporal trends (e.g., wet weather).
The adjustments described above will result in modifications to the presentation of the mass
loading results. Specifically, the total mass load in the Cape Fear River will be assessed using only
the downstream Cape Fear River composite samples. The estimated pathway-specific loads will
continue to be presented to provide an assessment of the relative loads to the measured total Table
3+ PFAS load to the Cape Fear River. Finally, additional descriptions of groundwater
concentrations adjacent to the Cape Fear River will be provided.
REFERENCES
Geosyntec, 2018. Assessment of the Chemical and Spatial Distribution of PFAS in the Cape Fear
River. Chemours Fayetteville Works. September 17, 2018.
Geosyntec, 2019a. Cape Rear River PFAS Mass Loading Model Assessment and Paragraph 11.1
Characterization of PFAS at Intakes. Chemours Fayetteville Works. August 26, 2019.
Geosyntec, 2019b. Assessment of HFPO-DA and PFMOAA in Outfall 002 Discharge and Evaluation
of Potential Control Options. Chemours Fayetteville Works. August 26, 2019.
Geosyntec, 2020. Response to North Carolina Department of Environmental Quality Comments -
Dated December 19, 2019. Chemours Fayetteville Works. January 31, 2020.
TABLE 1 PFAS MASS LOADING MODEL POTENTIAL PATHWAYS Chemours Fayetteville Works, North CarolinaGeosyntec Consultants NC P.C.Transport Pathway NumberPotential PFAS Transport PathwayAnalytical Data Source for Mass Loading Model1Flow Data Source for Mass Loading Model11 Upstream River and GroundwaterMeasured from Cape Fear River samples CFR-MILE-76 collected on November 12, 2019 directly upstream of Site.Measured flow rates from USGS gauging station at W.O. Huske Dam2.2 Willis Creek Measured from Willis Creek samples collected on November 12, 2019.Measured flow rate through point velocity flow gauging on November 12, 2019.3 Aerial Deposition on River4 Outfall 002Measured from a 24-hour composite sample from Outfall 002 collected in November 2019.Measured daily Outfall 002 flow rates.5 Onsite Groundwater Measured from LTW well samples collected in December 2019.Estimated from calculated hydraulic gradients based on November 2019 water levels and hydraulic conductivities of LTW wells from slug tests performed in 2019.6 Seeps Measured from Seeps A, B, C, and D samples collected on November 12, 2019.Measured flow rates through flumes in Seeps A, B and C and salt dilution gauging at Seep D on November 12, 2019.7 Old Outfall 002 Measured from an Old Outfall 002 sample collected on November 12, 2019. Measured flow rates through flume on November 12, 2019.8 Adjacent and Downstream Groundwater9 Georgia Branch Creek Measured from Georgia Branch Creek sample collected on November 12, 2019.Measured flow rate through point velocity flow gauging on November 12, 2019.Notes:1. Flow and concentration data are multiplied together to estimate the PFAS mass load in the Cape Fear River originating from each pathway.2. Cape Fear River flow rates measured at USGS gauging station #02105500 located at William O Huske Lock & Dam accessed from https://waterdata.usgs.gov on 2019-07-12 23:42:42 EDT.References:Geosyntec, 2019. Cape Rear River PFAS Mass Loading Model Assessment and Paragraph 11.1 Characterization of PFAS at Intakes. Chemours Fayetteville Works. 26 August 2019.ERM, 2018. Modeling Report: HFPO-DA Atmospheric Deposition and Screening Groundwater Effects. 27 April 2018.Estimated from air deposition modeling as described in the Mass Loading Model Report and the ERM Air Deposition Modeling Report.Estimated from residential well data as described in the Mass Loading Model Report.TR0795Page 1 of 1March 2020
TABLE 2
CAPE FEAR RIVER TOTAL TABLE 3+ PFAS
MASS LOADING MODEL PATHWAY APPORTIONMENT UPDATE
ESTIMATED LOADING PERCENTAGE PER PATHWAY
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC P.C.
22-May-19 07-Jun-19 18-Sep-19
Event Event Event
[1] Upstream River Water and Groundwater 4% 15% 8% 7%
[2] Willis Creek 10% 4% 3% 5%
[3] Aerial Deposition on Water Features < 2% < 2% < 2% < 2%
[4] Outfall 002 4% 7% 4% 8%
[5] Onsite Groundwater 2 22% 17% 14% 14%
[6] Seeps 32% 24% 41% 43%
[7] Old Outfall 002 23% 29% 27% 22%
[8] Offsite Adjacent and Downstream Groundwater < 2% < 2% < 2% < 2%
[9] Georgia Branch Creek 4% 3% 2% 1%
Notes:
Acronyms:
cfs - cubic feet per second
mg/s - milligrams per second
ng/L - nanograms per liter
PFAS - per- and polyfluoroalkyl substances
Estimated Loading Percentage
per Pathway per Event
1 - The mass loading sampling conducted on November 12, 2019 occurred during a rainfall of 0.33 inches as measured at
the Site meterological station.
12-Nov-2019
Event 1
2 - The onsite groundwater term is calculated for all events using the analytical solution presented in the mass loading
model report (Geosyntec, 2019).
Pathway
Total Table 3+ PFAS
TR0795 Page 1 of 1 March 2020
TABLE 3
CAPE FEAR RIVER TOTAL TABLE 3+ PFAS
MASS LOADING MODEL PATHWAY APPORTIONMENT UPDATE
ESTIMATED LOADING PER PATHWAY
Chemours Fayetteville Works, North Carolina
Geosyntec Consultants of NC P.C.
22-May-19 07-Jun-19 18-Sep-19
Event Event Event
[1] Upstream River Water and Groundwater 0.43 1.87 0.94 0.73
[2] Willis Creek 1.06 0.49 0.31 0.53
[3] Aerial Deposition on Water Features <0.01 <0.01 <0.01 <0.01
[4] Outfall 002 0.37 0.92 0.52 0.89
[5] Onsite Groundwater 2 2.01 1.87 1.70 1.47
[6] Seeps 3.36 3.11 5.00 4.68
[7] Old Outfall 002 2.42 3.75 3.32 2.32
[8] Offsite Adjacent and Downstream Groundwater 0.05 0.05 0.05 0.05
[9] Georgia Branch Creek 0.39 0.41 0.29 0.09
Calculated Total Table 3+ Loading (mg/s) at Bladen Bluffs3 10.1 12.5 12.1 10.8
Measured Total Table 3+ Loading (mg/s) at Bladen Bluffs3,4 13.6 16.4 11.4
Cape Fear River Flow Rate at W.O. Huske Dam (cfs) 1,640 1,180 992
Measured Total Table 3+ at Bladen Bluffs (ng/L) 293 492 405
Measured Rainfall During Bladen Bluff Sampling Day (in) 0.00 0.00 0.00
Notes:
Acronyms:
cfs - cubic feet per second
in - inches
mg/s - milligrams per second
ng/L - nanograms per liter
PFAS - per- and polyfluoroalkyl substances
Pathway
Total Table 3+ PFAS
Estimated Mass Loading in mg/s
per Pathway per Event
12-Nov-2019
Event 1
4 - The November 12, 2019 Bladen Bluffs sample was collected before stormwater flows from the Site reached Bladen
Bluffs, thus potentially contributing to the difference between the calculated and measured Total Table 3+ PFAS loadings.
0.33
7.1
1,140
221
1 - The mass loading sampling conducted on November 12, 2019 occurred during a 0.33 inch rainfall event as measured at
the Site meterological station.
2 - The onsite groundwater term is calculated for all events using the analytical solution presented in the mass loading
model report (Geosyntec, 2019).
3 - Calculated loadings from the pathways are compared to the measured loadings in the Cape Fear River at Bladen Bluffs,
approximately 5 miles downstream from the W.O. Huske Dam. Measured loadings at Bladen Bluffs are estimated by
multiplying measured river concentrations at Bladen Bluffs by the flow rate of the river at the W.O. Huske Dam.
TR0795 Page 1 of 1 March 2020
TABLE 4NOVEMBER 2019 MASS LOADING EVENT ANALYTICAL RESULTSChemours Fayetteville Works, North CarolinaGeosyntec Consultants of NC P.C.Potential PFAS Transport Pathway 1 2 4 4 5 5 5Location ID CFR-MILE-76 WC-1 OUTFALL 002 OUTFALL 002 LTW-01 LTW-02 LTW-03Field Sample ID CFR-RM-76-111219 WC-1-111219 OUTFALL 002-111219 SE91112 P16BLQ419-LTW-01-120619 P16BLQ419-LTW-02-120519 P16BLQ419-LTW-03-120619Sample Date 11/12/2019 11/12/2019 11/12/2019 11/12/2019 12/6/2019 12/5/2019 12/6/2019QA/QCSample Type Grab Grab Grab Composite Grab Grab GrabSDG 320-56253-1 320-56275-1 320-56275-1 NA 320-56874-1 320-56876-1 320-56874-1Lab Sample ID 320-56253-4 320-56275-2 320-56275-3 Onsite Lab 320-56874-6 320-56876-8 320-56874-1Table 3+ Lab SOP (ng/L)HFPO-DA4.8 440 1,600 357 24,000 7,200 11,000PFMOAA <5 UJ710 160 J 277 50,000 23,000 150,000PFO2HxA <2450 260 396 32,000 9,700 31,000PFO3OA <280 J 130 J 320 7,000 2,000 4,700PFO4DA <219 J 88 J 171 1,200 160 150PFO5DA <22.8 71 103 150<34 <34PMPA11 570 110 118 21,000 3,700 8,900PEPA <20150 56<5007,300 1,200 2,200PFESA-BP1 <2 <2630 J 188<27 <27 <27PFESA-BP2 <213 120 105 180<30 <30Byproduct 43.1 J 34 J 230 J<100860 220 510Byproduct 5 <2180 J 520 J 136 700 460 1,900Byproduct 6 <2 <25.3<100 <15 <15 <15NVHOS3.8 14 36<100460 210 880EVE Acid <2 <2640<100 <24 <24 <24Hydro-EVE Acid <27.3 54<100140 34 40R-EVE <219 J 76 J<100700 220 400 JPES <2 <2 <2 <100 <46 <46 <46PFECA B <2 <2 <2 <100 <60 <60 <60PFECA-G <2 <2 <2 <100 <41 <41 <41Notes:Bold - Analyte detected above associated reporting limitJ - Analyte detected. Reported value may not be accurate or preciseNA - not applicaleng/L - nanograms per literQA/QC - Quality assurance/ quality controlSOP - standard operating procedureUJ – Analyte not detected. Reporting limit may not be accurate or precise. < - Analyte not detected above associated reporting limit. TR0795Page 1 of 3March 2020
TABLE 4NOVEMBER 2019 MASS LOADING EVENT ANALYTICAL RESULTSChemours Fayetteville Works, North CarolinaGeosyntec Consultants of NC P.C.Potential PFAS Transport PathwayLocation IDField Sample IDSample DateQA/QCSample TypeSDGLab Sample IDTable 3+ Lab SOP (ng/L)HFPO-DAPFMOAAPFO2HxAPFO3OAPFO4DAPFO5DAPMPAPEPAPFESA-BP1PFESA-BP2Byproduct 4Byproduct 5Byproduct 6NVHOSEVE AcidHydro-EVE AcidR-EVEPESPFECA BPFECA-GNotes:Bold - Analyte detected above associated reporting limitJ - Analyte detected. Reported value may not be accurate or preciseNA - not applicaleng/L - nanograms per literQA/QC - Quality assurance/ quality controlSOP - standard operating procedureUJ – Analyte not detected. Reporting limit may not be accurate or precise. < - Analyte not detected above associated reporting limit. 55666667LTW-04 LTW-05 SEEP-A-1 SEEP-A-1 SEEP-B-1 SEEP-C-1 SEEP-D-1 OLDOF-1P16BLQ419-LTW-04-120619 P16BLQ419-LTW-05-120519 SEEP-A-1-111219 SEEP-A-1-111219-D SEEP-B-1-111219 SEEP-C-111219 SEEP-D-1-111219 OLDOF-1-11121912/6/2019 12/5/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019Field DuplicateGrab Grab Grab Grab Grab Grab Grab Grab320-56874-1 320-56876-1 320-56313-1 320-56313-1 320-56273-1 320-56273-1 320-56275-1 320-56313-1320-56874-4 320-56876-4 320-56313-1 320-56313-2 320-56273-4 320-56273-8 320-56275-1 320-56313-330,000 5 18,000 J 28,000 J 25,000 27,000 9,100 5,10087,000 190,000 84,000 95,000 200,000 220,000 120,000 81,00030,000 52,000 37,000 41,000 49,000 62,000 28,000 17,0006,000 17,000 13,000 15,000 12,000 20,000 7,900 J 4,800800 2,600 6,300 7,800 1,800 5,600 2,100 J 1,70039<672,800 3,600 140<6798 J 87022,000 4,700 20,000 20,000 35,000 13,000 7,500 5,0008,400 400 7,100 7,300 15,000 4,000 2,400 1,600<27 <533,700 4,500 1,100<53 <27400160 220 950 1,100 620 620 300 3401,900 960 1,700 J 2,000 J 3,700 J 1,200 J 600 J 380 J3,400 1,500 14,000 J 18,000 J 30,000 J 2,400 J 1,700 J 1,200 J17 36 40 J 60 J 54 41 20<151,600 1,300 890 980 2,600 1,700 890 730<24 <49720 J 980 J 1,400<49 <2436610 1,000 1,100 1,300 2,000 2,600 1,300 2102,300 1,200 1,100 J 1,300 J 2,500 J 2,200 J 850 230 J<46 <92 <46 <46 <46 <92 <46 <46<60 <120 <60 <60 <60 <120 <60 <60<41 <82 <41 <41 <41 <82 <41 <41TR0795Page 2 of 3March 2020
TABLE 4NOVEMBER 2019 MASS LOADING EVENT ANALYTICAL RESULTSChemours Fayetteville Works, North CarolinaGeosyntec Consultants of NC P.C.Potential PFAS Transport PathwayLocation IDField Sample IDSample DateQA/QCSample TypeSDGLab Sample IDTable 3+ Lab SOP (ng/L)HFPO-DAPFMOAAPFO2HxAPFO3OAPFO4DAPFO5DAPMPAPEPAPFESA-BP1PFESA-BP2Byproduct 4Byproduct 5Byproduct 6NVHOSEVE AcidHydro-EVE AcidR-EVEPESPFECA BPFECA-GNotes:Bold - Analyte detected above associated reporting limitJ - Analyte detected. Reported value may not be accurate or preciseNA - not applicaleng/L - nanograms per literQA/QC - Quality assurance/ quality controlSOP - standard operating procedureUJ – Analyte not detected. Reporting limit may not be accurate or precise. < - Analyte not detected above associated reporting limit. 7 9 Bladen Bluffs Kings Bluff Intake NA NA NAOLDOF-1 GBC-1 CFR-BLADEN CFR-KINGS EB EB FBLKOLDOF-1-111219-D GBC-1-111219 CFR-BLADEN-111219 CFR-KINGS-111219 EQBLK-01-111219 EQBLK-02-111219 FBLK-01-11121911/12/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019 11/12/2019Field DuplicateEquipment Blank Equipment Blank Field BlankGrab Grab Grab Liquid LIQUID LIQUID LIQUID320-56313-1 320-56275-1 320-56253-1 320-56253-1 320-56275-1 320-56275-1 320-56253-1320-56313-4 320-56275-5 320-56253-5 320-56253-6 320-56275-6 320-56275-7 320-56253-76,100 530 68 19<4 <4 <486,000 67 J 74 J 46 J<5 <5 <518,000 310 43 26<2 <2 <25,100 48 J 11 J 6.5 J<2 <2 <21,800 15 J 3.9 J 2.2 J<2 <2 <2870<2 <2 <2 <2 <2 <25,300 760 25 24<10 <10 <101,700 240<20 <20 <20 <20 <20400<2 <2 <2 <2 <2 <2360 17<2 <2 <2 <2 <2350 J 29 J 5.1 J 7.9 J<2 <2 <21,100 J<215 J 12 J<2 <2 <2<15 <2 <2 <2 <2 <2 <2740 3.5 3.7 6.1<2 <2 <243<2 <2 <2 <2 <2 <2210<2 <2 <2 <2 <2 <295 J 11 J 2.7 J 3.2 J<2 <2 <2<46 <2 <2 <2 <2 <2 <2<60 <2 <2 <2 <2 <2 <2<41 <2 <2 <2 <2 <2 <2TR0795Page 3 of 3March 2020
LegendNotes\\projectsitesb.geosyntec.com@SSL\DavWWWRoot\5\FWConsentOrder\Shared Documents\12 - AOC Paragraph 12\08 - Mass Loading Model Assessment\08 - November 2019 UpdaNovember Mass Loading Sampling TimesChemours Fayetteville Works, North CarolinaFigure1Raleigh March 20201 - not used in mass loading model calculations.This plot shows when Cape Fear River water was passing by the Site on November 12, 2019 and when it was estimated to reach the downstream sampling point at Bladen Bluffs (approximately 5 miles downstream from the Site). Samples collected at Bladen Bluffs are used to compare against the estimated mass loading from the model because PFAS loading is expected to be well mixed in the river by this point. During the November 12, 2019 sampling event, water passing W.O. Huske Dam was estimated to take 10 hours to reach Bladen Bluffs based on historical modeled travel time results generated from a numerical model of the Cape Fear River (corresponding with the river gage height reported as 1.42 feet at the W.O. Huske Dam per the United States Geological Survey). Travel times were calculated based on pathway-specific distances from the Bladen Bluffs sampling location. This plot demonstrates that samples collected at Bladen Bluffs should be collected later in time to correspond to arrival times of samples collected from the various mass loading pathways at the Site.Hours since 0:00 November 12, 2019Period of RainfallSample TimeEstimated Arrival Time at Bladen BluffsBladen Bluffs Sample TimeRepresentative Sampling Interval at Bladen BluffsBladen BluffsUpstream RiverOutfall 002 Grab Sample1Outfall 002 24‐hr CompositeWillis and Georgia Branch CreeksOld Outfall 002Seeps