Response to NCDEQ Comments Dated July 3, 2019
Old Outfall 002
Remedial Options Plan (May 20, 2019)
NCDEQ Comment
General Questions and Observations
DEQ requests any monthly sampling data be provided to the agency as it isgenerated, rather than waiting until the final report in September.

Chemours Response
Data will be provided as received. The first set of data was provided in
the quarterly report dated July 15, 2019, pursuant to Consent OrderParagraph 28.

There are no potential preferential pathways identified at the site, which may
be useful for test design and developing an overall corrective‐action strategy. The identification and assessment of potential preferential pathways ispresently ongoing and will be incorporated in Chemours' planning for
Please provide any
future consent order submittals and corrective action at the Site.
identified potential preferential pathways.
There may be low hydraulic conductivity intervals in the subsurface that
Chemours acknowledges this fact and is conducting geologicalcould be important considerations with respect to test design andassessments and a pilot study to evaluate the presence of low
implementation.
permeability zones and their potential impacts on potential correctiveactions.
o Vertical gradients may be present in low conductivity intervals.
o Delivery of injectants may be limited by low conductivity intervals andoverall subsurface heterogeneity.
Site‐specific geochemical conditions may be important considerations for
Chemours is assessing the geochemistry of waters to ensure corrective
implementation and interpretation of test results. Please provide any
action approaches will be effective in achieving goals. The pre‐injection
available geochemical data for the site.
sampling data from the Regeneis Phase 1 Pilot Study Verification wells
was provided to NCDEQ on July 15, 2019. This data included hardness
along with total and disolved calcium and organic carbon. This
information is also being analyzed in post‐injection samples (datapending). Geochemical data was collected at the proposed Old Outfall
002 collection point as part of the NPDES permit application submitted
on July 11, 2019. The results for this 24‐hour composite sample areattached.
Option 1: Capture and Treat
Option 1 appears to address the perched and surficial aquifer but not theBlack Creek aquifer. How would Option 1 decrease the loading from thisaquifer to meet the requirements of the Paragraph 12.e?

Capture and treatment of the Old Outfall 002 dry weather flow willcapture any groundwater that has discharged to the Old Outfall 002
before the capture point regardless of which aquifer it comes from.

Page 1 of 4

Response to NCDEQ Comments Dated July 3, 2019
Old Outfall 002
Remedial Options Plan (May 20, 2019)
NCDEQ Comment
Chemours Response
Option 2: Regenesis PlumeStop
Chemours acknowledges this comment and is performing a pilot study toDEQ does not believe that enough information has been provided tobetter evaluate the potential for PlumeStop™ to help support corrective
determine if Option 2 would be an effective means of compliance withParagraph 12.e of the Consent Order, i.e. would it achieve results that would action at the Site.
be equivalent to or greater than treating dry weather flow at the Option B
location with a PFAS removal efficiency of 99%.
Option 2 appears to address only the perched aquifer, but does not address The PlumeStop™ pilot study is meant to evaluate application in a smaller
the surficial aquifer or the Black Creek aquifer. How would Option 2 decrease area, i.e. the Perched Zone. If PlumeStop™ is selected as part of thecorrective actions for Paragraph 12.e, it would be also applied to otherthe loading from these sources to meet the requirements of the Paragraphaquifers as needed to provide performance equivalent to Option 1.
12.e?
Option 2 should include monitoring for the full suite of PFAS in wells aroundthe PlumeStop to better understand how it interacts with these chemicals
and its efficacy.

Chemours is analyzing groundwater samples collected as part of the Pilot
study using methods Table 3+ SOP and EPA 537. In addition to PFAS,
Chemours is analyzing volatile organic compounds (VOCs), hardness,dissolved calcium, total calcium, and total organic carbon (TOC) to assess
the groundwater geochemistry and how this may affect PFAS reductions
by PlumeStop™.

DEQ requests that Chemours explain how Chemours will monitor for
movement of PlumeStop in soils at the site over time to ensure that
PlumeStop constituents are not migrating into surface waters.

PlumeStop™ is a colloidal suspension of activated carbon that adheres tosoil particles after injection. After injection, when the likelihood of
mobilized colloids is highest, monitoring is performed in downgradientperformance monitoring wells to assess if PlumeStop™ colloids arepresent. Should colloid be present, Regenisis will add a product which
immobilizes and terminates the colloidal suspension of PlumeStop™.
Should Chemours propose PlumeStop™ as part of corrective actions at
the Site, more detailed information regarding this topic will be provided.

Page 2 of 4

Response to NCDEQ Comments Dated July 3, 2019
Old Outfall 002
Remedial Options Plan (May 20, 2019)
NCDEQ CommentOption 2 would require an Injection Permit Application. A complete
application would need to be submitted 60‐90 days before implementation
with the following information:• Injection zone
• Hydrogeologic Evaluation• Injectant Information• Injection Procedure• Fracturing plan (if applicable)• Well Construction Details• Monitoring Plan
• Well Data Tabulation• Maps and Cross section
Option 3: Hydraulic Control

Chemours Response
Chemours appreciates DEQ noting this information.

Chemours acknowledges this comment and is completing an additional
DEQ does not believe that enough information has been provided togeological investigation at the Site. Chemours is also preparing adetermine if Option 3 would be an effective means of compliance withnumerical groundwater model, which is being constructed consistent
Paragraph 12.e of the Consent Order, i.e. would it achieve results that would with the North Carolina Department of Environmental Quality’s (NCDEQ)
be equivalent to or greater than treating dry weather flow at the Option B
2007 Groundwater Modeling Policy.
location with a PFAS removal efficiency of 99%.
Option 3 appears to address the perched and surficial aquifer but not theAny potential hydraulic control option performed as part of ParagraphBlack Creek aquifer. How would Option 3 decrease the loading from this12.e will be designed to be as effective as capture and treatment of dry
aquifer to meet the requirements of the Paragraph 12.e?
weather flow at the capture location. If this requires reductions in theloading of Black Creek Aquifer flow, then this will be part of any
potentially proposed action.
Chemours acknowledges this comment. As noted earlier, Chemours isOption 3 would require a non‐discharge groundwater remediation permit
application that includes information on hydraulic control and hydrogeology preparing a numerical groundwater model to help quantitatively assessthat helps determine if the aquifer will accommodate the volumes of injected this consideration should re‐injection of groundwater be proposed aspart of corrective actions at the Site.
water.

Page 3 of 4

Response to NCDEQ Comments Dated July 3, 2019
Old Outfall 002
Remedial Options Plan (May 20, 2019)
NCDEQ Comment
Chemours Response
Chemours acknowledges this comment. If this options is proposed asAs Option 3 is considered, it should be noted that a slurry wall with treatedpart of corrective actions at Site, this consideration will be addressed inwater injected into the aquifer at too high a volume and pressure could
results in well integrity failure, injected water breaching into upper and lower detailed design phases of the project.
aquifers, or injected water daylighting to the surface.
What levels of PFAS are proposed to be reinjected as part of the pump andtreat system?

Chemours acknowledges this is an important consideration in a detailed
design of this type of system. Should this type of approach be proposed
as part of corrective actions at the Site, Chemours will include theconsideration in the design to make sure the corrective action meetsoverall goals.

Page 4 of 4

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 15

Attachment 1
24-Hour Influent Characterization Results
Old Outfall 002 Option B Location (ProposedDam)

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 16

24‐Hour Influent Characterization Results
Old Outfall 002 Option B Location (Proposed Dam)
Attachment 1
Parameter

Units

ResultTable 3+ PFAS
Byproduct 1 (PFESA BP 1)

µg/L

0.38

Byproduct 2 (PFESA BP 2)

µg/L

0.31

Byproduct 4 (PFESA BP 4)

µg/L

0.38

Byproduct 5 (PFESA BP 5)

µg/L

0.82

Byproduct 6 (PFESA BP 6)µg/L< 0.015

DFSA

µg/L

Note (1)EVE Acid

µg/L

0.034

Hydro‐EVE Acid

µg/L

0.19

MeFOSA

µg/L< 0.035

M‐MeFOSE‐Mµg/L< 0.11

MMPµg/L

Note (1)

MTP

µg/L

Note (1)NEtFOSAMµg/L< 0.037

N‐EtFOSE‐Mµg/L< 0.060

NVHOS

µg/L

0.78

2,3,3,3‐Tetrafluoro‐2‐(pentafluoroethoxy)propanoic acid (PEPA)µg/L

1.9PESµg/L< 0.046PFECA B

µg/L

< 0.060PFECA G

µg/L

< 0.041

Perfluoro‐2‐methoxyacetic acid (PFMOAA)

µg/L

85

Perfluoro(3,5‐dioxahexanoic) acid (PFO2HxA)

µg/L

17

Perfluoro(3,5,7‐trioxaoctanoic) acid (PFO3OA)

µg/L

5.1

Perfluoro(3,5,7,9‐tetraoxadecanoic) acid (PFO4DA)

µg/L

1.6

Perfluoro(3,5,7,9,11‐pentadodecanoic) acid (PFO5DA)

µg/L

0.58

Perfluoro‐2‐methoxypropanoic acid (PMPA)

µg/L

5.4

PPF Acidµg/L

Note (1)

R‐EVE

µg/L

0.12

10:2 fluorotelomer sulfonate (10:2 FTS)

µg/L

< 0.0026

4:2 fluorotelomer sulfonate (4:2 FTS)

µg/L

< 0.0026

6:2 fluorotelomer sulfonate (6:2 FTS)

µg/L

< 0.0017

EPA Mod 537 MAX PFAS

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 17

24‐Hour Influent Characterization Results
Old Outfall 002 Option B Location (Proposed Dam)
Attachment 1‐Contd.
ParameterUnits

Result

8:2 fluorotelomer sulfonate (8:2 FTS)

µg/L

< 0.0052

Perfluoro‐2‐propoxypropanoic acid (HFPO‐DA; “Dimer Acid”)

µg/L

6.0

N‐ethylperfluorooctanesulfonamidoacetic acid (NEtFOSAA)µg/L< 0.0026

N‐ethylperfluoro‐1‐octanesulfonamide (NEtPFOSA)µg/L< 0.0079

2‐(N‐ethylperfluoro‐1‐octanesulfonamido) ethanol (NEtPFOSAE)µg/L< 0.0026

N‐methylperfluorooctanesulfonamidoacetic acid (NMeFOSAA)µg/L< 0.0026

N‐methylperfluoro‐1‐octanesulfonamide (NMePFOSA)µg/L< 0.0079

2‐(N‐methylperfluoro‐1‐octanesulfonamido) ethanol (NMePFOSAE)µg/L< 0.0026

Perfluorobutane Sulfonic Acid (PFBS)µg/L

0.0013

Perfluorobutanoic Acid (PFBA)

µg/L

0.072

Perfluorodecane Sulfonic Acid (PFDS)µg/L< 0.0017

Perfluorodecanoic Acid (PFDA)µg/L< 0.0017

Perfluorododecane Sulfonic Acid (PFDoS)µg/L< 0.00087

Perfluorododecanoic Acid (PFDoA)µg/L< 0.0017

Perfluoroheptane Sulfonic Acid (PFHpS)µg/L< 0.0017

Perfluoroheptanoic Acid (PFHpA)

µg/L

0.024

Perfluorohexadecanoic Acid (PFHxDA)µg/L< 0.00087

Perfluorohexane Sulfonic Acid (PFHxS)µg/L< 0.0017

Perfluorohexanoic Acid (PFHxA)

µg/L

0.015

Perfluorononane Sulfonic Acid (PFNS)µg/L< 0.0017

Perfluorononanoic Acid (PFNA)µg/L

0.0069Perfluorooctadecanoic Acid (PFODA)µg/L< 0.0017

Perfluorooctane Sulfonamide (FOSA)µg/L< 0.0026

Perfluorooctane Sulfonic Acid (PFOS)µg/L

0.0018Perfluorooctanoic Acid (PFOA)

µg/L

0.028

Perfluoropentane Sulfonic Acid (PFPeS)µg/L< 0.0017

Perfluoropentanoic Acid (PFPeA)

µg/L

0.15

Perfluorotetradecanoic Acid (PFTeA)µg/L< 0.00087

Perfluorotridecanoic Acid (PFTriA)µg/L< 0.00087

Perfluoroundecanoic Acid (PFUnA)µg/L< 0.0017

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 18

24‐Hour Influent Characterization Results
Old Outfall 002 Option B Location (Proposed Dam)
Attachment 1‐Contd.
Parameter

Units

ResultConventional and Nonconventional Parameters
Biochemical Oxygen Demand (BOD5)

mg/L

<2

Chemical Oxygen Demand (COD)

mg/L< 12.8

Total Organic Carbon (TOC)

mg/L

1.1Total Suspended Solids (TSS)

mg/L

10.4

mg/L as N< 0.05Bromide

mg/L

< 1.3

Chlorine, total residual

mg/L

Not Measured(1)CP Units<5Fecal ColiformUNITS

Not Measured(1)Fluoride

mg/L< 0.25

Nitrate‐nitrite

mg/L

0.29

mg/L as N

Not Measured(1)

mg/L

< 1.4

mg/L as P< 0.050

Sulfatemg/L as SO471

Sulfidemg/L as S< 0.70Sulfitemg/L as SO3<2

Surfactants (MBAS)

mg/L< 0.040

Aluminum, Total

mg/L

8.1

Barium, Total

mg/L

0.052

Boron, Total

mg/L

0.14

Cobalt, Total

mg/L

0.17

Iron, Total

mg/L

11.7

Magnesium, Total

mg/L

1.95

Molybdenum, Total

mg/L< 0.0020

Manganese, Total

mg/L

0.195

Tin, Total

mg/L< 0.0070

Titanium, Total

mg/L< 0.0020

Ammonia (NH3‐N)
Certain Conventional and Nonconventional Pollutants

Color

Nitrogen, Total Organic
Oil and Grease
Phosphorus, Total

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 19

24‐Hour Influent Characterization Results
OOF2 Option B Location (Proposed Dam)
Attachment 1‐Contd.
ParameterUnits

ResultCertain Conventional and Nonconventional Pollutants (Continued)
Radioactivity
Alpha, Total

PCi/L

7.38

Beta, Total

PCi/L

6.79

Radium, Total

PCi/L

3.44

Radium 226, Total

PCi/L< 0.373

Antimony, Total

mg/L< 0.0100

Arsenic, Total

mg/L< 0.0160

Beryllium, Total

mg/L

0.0018

Cadmium, Total

mg/L< 0.0010

Chromium, Total

mg/L

0.0094

Copper, Total

mg/L

0.0064

Lead, Total

mg/L< 0.0060

Mercury, Totalµg/L< 0.050

Nickel, Total

mg/L

0.0020

Selenium, Total

mg/L< 0.0210

Silver, Total

mg/L< 0.0050

Thallium, Totalmg/L< 0.0140

Zinc, Total

mg/L

0.0368Cyanide, Total

mg/L< 0.0050

Phenols, Total

mg/L< 0.010Acroleinµg/L<3Acrylonitrile

µg/L

< 0.5

Benzeneµg/L< 0.2Bromoform

µg/L

< 0.5

Carbon Tetrachloride

µg/L

< 0.2

Toxic Metals, Total Cyanide, and Total Phenols

Toxic Metals, Total Cyanide, and Total Phenols (Continued)

Organic Toxic Pollutants (GC/MS Fraction – Volatile Compounds)

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 20

24‐Hour Influent Characterization Results
OOF2 Option B Location (Proposed Dam)
Attachment 1‐Contd.

Parameter

Units

ResultOrganic Toxic Pollutants (GC/MS Fraction – Volatile Compounds) (Continued)
Chlorobenzene

µg/L

< 0.2

Chromodibromomethane

µg/L

< 0.3

Chloroethane

µg/L

< 0.3

2‐Chloroethylvinyl ether

µg/L

< 0.1

Chloroform

µg/L

< 0.2

Dichlorobromomethane

µg/L

< 0.3

1,1‐Dichloroethane

µg/L

< 0.2

1,2‐Dichloroethane

µg/L

< 0.2

1,1‐Dichloroethylene

µg/L

< 0.2

1,2‐Dichloropropane

µg/L

< 0.2

1,3‐Dichloropropylene

µg/L

< 0.2

Ethylbenzeneµg/L< 0.1

Methyl bromide

µg/L

< 0.4

Methyl chlorideµg/L< 0.3

Methylene chloride

µg/L

< 0.3

1,1,2,2‐Tetrachloroethane

µg/L

< 0.2

Tetrachloroethyleneµg/L< 0.2Toluene

µg/L

< 0.1

1,2‐trans‐dichloroethylene

µg/L

< 0.2

1,1,1‐Trichloroethane

µg/L

< 0.2

1,1,2‐Trichloroethane

µg/L

< 0.2

Trichloroethylene

µg/L

< 0.1

Vinyl Chloride

µg/L

< 0.4

2‐Chlorophenol

µg/L

< 0.3

2,4‐Dichlorophenol

µg/L

< 0.3

2,4‐Dimethylphenol

µg/L

< 0.3

4,6‐Dinitro‐o‐Cresolµg/L<4Organic Toxic Pollutants (GC/MS Fraction – Acid Fraction)

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 21

24‐Hour Influent Characterization Results
OOF2 Option B Location (Proposed Dam)
Attachment 1‐Contd.
ParameterUnits

ResultOrganic Toxic Pollutants (GC/MS Fraction – Acid Fraction) (Continued)
2,4‐Dinitrophenol

µg/L

< 10

2‐Nitrophenol

µg/L

< 0.4

4‐Nitrophenol

µg/L

<5

p‐Chloro‐m‐cresol

µg/L

< 0.3

Pentachlorophenolµg/L<3Phenol

µg/L

< 0.4

2,4‐6‐Trichlorophenolµg/L< 0.7Acenaphthene

µg/L

< 0.3

Acenaphthylene

µg/L

< 0.3

Anthracene

µg/L

< 0.2

Benzideneµg/L< 20Benzo(a)anthracene

µg/L

< 0.2

Benzo(a)pyrene

µg/L

< 0.3

3,4‐Benzofluoranthene

µg/L

< 0.3

Benzo(g,h,i)perylene

µg/L

< 0.2

Benzo(k)fluoranthene

µg/L

< 0.3

Bis (2‐chloroethoxy)methane

µg/L

< 0.5

Bis (2‐chloroethyl)ether

µg/L

< 0.4

Bis (2‐chloroisopropyl)ether

µg/L

< 0.3

Bis (2‐ethylhexyl)phthalateµg/L<14‐Bromophenyl phenyl ether

µg/L

< 0.3

Butyl Benzyl Phthalateµg/L< 0.82‐Chloronaphthalene

µg/L

< 0.6

4‐Chlorophenyl Phenyl Etherµg/L< 0.3Chrysene

µg/L

< 0.2

Dibenzo(a,h)anthracene

µg/L

< 0.4

1,2‐Dichlorobenzene

µg/L

< 0.5

1,3‐Dichlorobenzene

µg/L

< 0.5

Organic Toxic Pollutants (GC/MS Fraction – Base/Neutral Compounds)

The Chemours Company
Engineering Report on Wastewater Treatability
July 2019
Page 22

24‐Hour Influent Characterization Results
OOF2 Option B Location (Proposed Dam)
Attachment 1‐Contd.
ParameterUnits

ResultOrganic Toxic Pollutants (GC/MS Fraction – Base/Neutral Compounds) (Continued)
1,4‐Dichlorobenzene

µg/L

< 0.5

3,3’‐Dichlorobenzidene

µg/L

< 0.8

Diethyl Phthalate

µg/L

< 0.3

Dimethyl Phthalate

µg/L

<1

Di‐n‐butyl Phthalate

µg/L

< 0.5

2,4‐Dinitrotoluene

µg/L

< 0.4

2,6‐Dinitrotoluene

µg/L

< 0.3

Di‐n‐octyl‐phthalate

µg/L

< 0.5

1,2‐Diphenylhydrazine

µg/L

< 0.2

Fluoranthene

µg/L

< 0.3

Fluorene

µg/L

< 0.3

Fluorene

µg/L

< 0.3

Hexachlorobenzene

µg/L

<1

Hexachlorobutadieneµg/L< 0.8

Hexachlorocyclopentadiene

µg/L

<2

Hexachloroethane

µg/L

< 0.4

Indeno(1,2,3‐cd)pyrene

µg/L

< 0.3

Isophorone

µg/L

< 0.3

Naphthalene

µg/L

< 0.2

Nitrobenzene

µg/L

< 0.5

N‐nitrosodimethylamine

µg/L

<2

N‐nitrosodi‐n‐propylamine

µg/L

< 0.4

N‐nitrosodiphenylamine

µg/L

< 0.3

Phenanthrene

µg/L

< 0.2

Pyrene

µg/L

< 0.2

1,2‐4‐Trichlorobenzene

µg/L

< 0.3

The Chemours CompanyEngineering Report on Wastewater Treatability
July 2019
Page 23

24‐Hour Influent Characterization ResultsOOF2 Option B Location (Proposed Dam)
Attachment 1‐Contd.

Parameter

Units

ResultOrganic Toxic Pollutants (GC/MS Fraction – Pesticides)
Aldrinµg/L< 0.00504

α‐BHC

µg/L

< 0.0121

β‐BHC

µg/L

< 0.0464

γ‐BHC (Lindane)µg/L< 0.00524

δ‐BHC

µg/L

< 0.0111

Chlordaneµg/L< 0.234

4,4’‐DDTµg/L< 0.0101

4,4’‐DDEµg/L< 0.02024,4’‐DDDµg/L< 0.00907

Dieldrinµg/L< 0.00807

α‐Endosulfanµg/L< 0.00302

β‐Endosulfanµg/L< 0.00988

Endosulfan Sulfateµg/L< 0.0101

Endrinµg/L< 0.00907

Endrin Aldehydeµg/L< 0.00917

Heptachlorµg/L< 0.00807

Heptachlor Epoxideµg/L< 0.00504

PCB‐1242µg/L< 0.0746

PCB‐1254µg/L< 0.0746

PCB‐1221µg/L< 0.0746

PCB‐1232µg/L< 0.0746

PCB‐1248µg/L< 0.0746

PCB‐1260µg/L< 0.0746

PCB‐1016µg/L< 0.0746

Toxapheneµg/L< 0.358

pg/L< 0.24

Dioxins
2,3,7,8‐TCDD

Note 1 – PFAS compounds PPF Acid, DFSA, MMF and MTP are presently undergoing analytical methods
development and therefore data for these compounds are not reported here.