2020.02.12_CCO.p10_FinalOutfall003NPDES89915FactSheet

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Fact Sheet
NPDES Permit No. NC0089915

Permit Writer/Email Contact: [e-mail]
Date: February 12, 2020
Division/Branch: NC Division of Water Resources / NPDES Complex Permitting
Fact Sheet Template: Version 09Jan2017

Permitting Action:
☐ Renewal
☐ Renewal with Expansion
☒ New Discharge
☐ Modification (Fact Sheet should be tailored to mod request)

Note: A complete application should include the following:
 For New Dischargers, EPA Form 2A or 2D requirements, Engineering Alternatives Analysis, Fee
 For Existing Dischargers (POTW), EPA Form 2A, 3 effluent pollutant scans, 4 2nd species WET
tests.
 For Existing Dischargers (Non-POTW), EPA Form 2C with correct analytical requirements based
on industry category.

Complete applicable sections below. If not applicable, enter NA.

1. Basic Facility Information
Facility Information
Applicant/Facility Name: The Chemours Company / Chemours Fayetteville Works
Applicant Address: 1007 Market Street, Wilmington, DE 19899
Facility Address: 22828 NC Highway 87 W, Fayetteville, NC 28306-7332
Permitted Flow: 1.58 MGD
Facility Type/Waste: MAJOR Industrial
Facility Class: II
Treatment Units: influent oxidation, coagulation, and pH adjustment, ultrafiltration,
granular activated carbon (GAC) adsorption
Pretreatment Program (Y/N): N/A
County: Bladen
Region: Fayetteville

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Briefly describe the proposed permitting action and facility background:

A. Introduction / Permitting Action

In order to reduce PFAS loading to the Cape Fear River pursuant to the Consent Order entered by the
Bladen County Superior Court on February 25, 2019 (“Consent Order”), Chemours has requested a new
NPDES permit for the discharge of treated groundwater, stormwater, and surface water from a stream
located on the southern portion of its property.

The flow from Outfall 003 consists primarily of contaminated surface water, stormwater, and groundwater,
which must be treated to remove at least 99% of the HFPO-DA (GenX), PFMOAA, and PMPA. This
stream, often referred to as “Old Outfall 002,” was used to discharge process wastewater from the facility
prior to June 2012, when the process wastewater discharge was relocated to the current outfall location (for
permit NC0003573) above Lock and Dam #3 (also known as William O Huske Dam) in the Cape Fear
River. Pursuant to the Consent Order, Chemours is required to implement a system to capture and treat the
dry weather flow (baseflow) at Old Outfall 002 prior to discharge by September 30, 2020. The treatment
system shall meet such discharge standards as shall be set by DEQ, and shall, in addition and at a minimum,
be at least 99% effective in controlling indicator parameters, HFPO-DA, PFMOAA, and PMPA, i.e. 99%
removal of these parameters. The issuance of this permit will allow Chemours to begin this remediation to
meet the Consent Order requirement and reduce PFAS loading to the Cape Fear River.

Additionally, as part of the Consent Order, Chemours was required to conduct a Mass Loading Assessment.
The summary report was submitted to DEQ on December 6, 2019. The report assessed all known sources
of per- and polyfluoroalkyl substances (PFAS) on and around the site and their potential mass loadings to
the Cape Fear River using data from the May, June, and September 2019 sampling for the facility.
Chemours preliminarily estimated that remediating the baseflow (dry weather flow) from this channel will
reduce overall loading of Total Table 3+ PFAS compounds to the river by 26% based on an average of
these two sampling events (Cape Fear River PFAS Loading Reduction Plan – Supplemental Information
Report, November 2019).

This outfall is named Outfall 003 in this new permit to allow for the potential consolidation of Chemours’
other NPDES wastewater permit, NC0003573, in the future.

B. Proposed Treatment System

The proposed treatment system includes a dam to collect dry weather baseflow in the creek bed/channel
(estimated to be 540 gallons per minute with a maximum flow of 610 gpm) and some seeps and
groundwater, for a total flow capacity at the dam (collection system) of 670 gallons per minute (gpm).
The treatment system is designed to treat a maximum flow of 750 gallons per minute (gpm), which will
provide a treatment safety factor in the event Chemours has trouble getting the flow through the carbon
systems. The Permitted Flow allowance of 1.58 million gallons per day (MGD) is for the addition of
future flows from on-site seeps and other groundwater remediation projects expected at the site.

The system is expected to be able to remove numerous PFAS compounds, including the indicator
parameters HFPO-DA (GenX), PFMOAA, and PMPA. As described above, the Consent Order specifies
that HFPO-DA and PFMOAA are to be removed from the Old Outfall 002 channel by at least 99%. The
Consent Order required Chemours to complete, at a minimum, monthly surface water sampling in Old
Outfall 002 at designated locations, beginning no later than March 2019 to be completed by September
30, 2019 to establish baseline mass loading from Old Outfall 002. Additionally, by September 30, 2019,
Chemours was required to complete pilot scale testing of treatment equipment to determine its control
efficiency for all PFAS identified in Old Outfall 002. Pilot testing results, received by DWR on October
3, 2019, demonstrated that the proposed GAC system can remove at least 99% of the total PFAS
compounds reported per the NPDES permit application.

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From time-to-time the Middle Cape Fear River has experienced flooding conditions which are
documented to cause a significant increase in water levels below Lock and Dam #3, consistent with the
location of proposed Outfall 003. During these events a backwater condition propagates upstream in the
“Old Outfall 002 Stream”. Historical observation indicates that the Old Outfall 002 Stream levels can rise
significantly (consistent with the flooded Cape Fear River levels) and would be expected, at times, to be
equal to or significantly greater than the invert elevation of the treatment system intake dam and
associated pumping system. During these flooded backwater conditions elevated sediment load and
reduced flow velocity gradients are expected to cause significant sediment deposition within the
collection dam and pumping structure. The sediment load may cause failure of the pumping and
treatment system during the flooded backwater condition. Requirement for treatment shall be suspended
during these force majeure flooding events and be allowed 48 hours after the backwater stream level falls
below the invert of the intake collection dam to safely maintain the influent collection structure and re-
initiate collection and treatment. The triggering Cape Fear River flood elevations; event
documentation and notification requirements; and procedure for treatment cessation and safe restart shall
be included in the approved Dam Operation and Maintenance Plan.

This proposed treatment system will consist of the following components:

1) Influent Oxidation, Coagulation & pH Adjustment
This treatment system includes an influent oxidation/coagulation /pH adjustment tank for pretreatment of
the ultrafiltration (UF) feed (pH adjustment/oxidation/coagulation). The pH adjustment will be done using
sodium hydroxide. Additional iron oxidation will be done with sodium hypochlorite. Poly-aluminum
chloride (PAC) will be used for coagulation and contribute to help maintain the UF membranes. Partially
treated water will be conveyed to the UF units via dual booster pumps. Safety Data Sheets (SDSs) are
attached for the chemicals to be utilized at the wastewater treatment system.
Iron hydroxide particles precipitated in the oxidation process and total suspended solids (TSS) will be
coagulated and settled in the tank. The settled solids will be transferred by a solids transfer pump to a weir
tank (back pulse waste recycle tank) and filtered in downstream removal processes (thickener and rotary-
fan filter press).

2) Ultrafiltration
This design includes UF pretreatment before the GAC stage. The UF will perform the role of solids removal
upstream of the GAC units. The UF will provide an absolute barrier to solids at 0.04 - 0.1 µm range. Per
the manufacturing vendor, the UF membrane will provide additional TOC removal as well.
The UF back pulse waste recycle will be captured in a weir tank to allow solids to settle and then will be
recycled through the system after being pumped back to the influent oxidation/coagulation /pH adjustment
tank. The settled solids in the weir tank (the back-pulse waste recycle tank) will be drawn off by a sludge
pump and filtered in downstream removal processes (thickener and rotary-fan filter press).
The UF units will intermittently need to be cleaned with a low concentration of citric acid. The cleaning
solution will be captured in a Clean-In Place (CIP) tank and neutralized in it. Following neutralization, the
CIP water will be recycled through the treatment system after being pumped back by CIP neutralization
pumps to the influent oxidation/coagulation /pH adjustment tank.
3) Granular Activated Carbon (GAC) Adsorption
Based on GAC adsorption studies, the PFAS removal required to meet discharge requirements (per the
Consent Order), is expected to be accomplished using GAC adsorption. The system design for this
application includes a total of six (6) 12’ diameter x 5’ diameter straight side vessels in a three (3) pass
configuration capable of swapping lead/middle/lag. Each GAC vessel can hold up to 20,000 lbs. of GAC.
The GAC beds will be sluiced out upon exhaustion and the new bed sluiced back into the vessel. The GAC
vessels have backwashing capability. Sizing, quantities and configuration may be modified during process
optimization.

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Chemours’ initial process control sampling plan consists of sampling the influent to the GAC system once
per week, sampling the lead, middle, and lag units twice a month, and additional sampling as needed when
nearing GAC unit replacement criteria. These samples will be analyzed by Chemours inhouse laboratory.
The lead GAC bed will be changed out when PFMOAA in the lead GAC unit equals PFMOAA out of the
lead GAC unit. This will ensure full utilization of the carbon bed. Chemours will test for PFMOAA between
each GAC unit to determine when units need to be rotated or disposed because this compound’s affinity to
carbon is a bit less than HFPO-DA. This was tested out during Chemours’ pilot scale study and a 99%
reduction was maintained for both compounds in the lag (or third) GAC bed effluent.

4) Solids Handling and Treatment
The treatment system includes a containerized sludge handling system with sludge pump, polymer make
down/injection system, in-line mixer and a thickener unit and rotary fan press skid. The rotary fan press
will be mounted on a sump with a pump to return filtrate from the process to the head of the plant into the
influent oxidation/coagulation /pH adjustment tank. Additionally, the solids handling system will include
a screw conveyor to move the sludge out of the container/press and into a roll off for storage, until the
sludge accumulates enough to be hauled off site. Solid waste is to be shipped to an approved waste
management facility for disposal per Federal and State Regulations.

5) Discharge
The treated water will be discharged and reintroduced to Outfall 003. The discharge location will be
downstream of the capture dam, and will flow from the channel into the Cape Fear River. On October 16,
2019, the division issued a 401 Certification for the construction of a weir to create a small in-stream
reservoir, DWR Project #2019-1146. The purpose of the project was to create a pool from which to
withdraw water, treat it in an upland facility and discharge below the weir. The permanent impacts for the
project were 270 Linear Feet of stream (Old Outfall 002). Most of the impacts were associated with the
stabilization of the stream bed and bank with rip-rap behind the weir. No mitigation was triggered as the
project did not exceed the state threshold of 300 LF of stream. The Army Corps of Engineers issued a 404
(NWP 38) for the project on October 29, 2019.

C. Facility Background

Currently, no process wastewater from Chemours is discharged. The only process wastewater discharged
comes from Chemours’ tenants DuPont and Kuraray. That wastewater is covered under the NPDES
discharge permit #NC0003573. This permit #NC0089915 is for the collection and treatment of the
contaminated dry weather flow (groundwater and surface water) in Chemours Old Outfall 002 channel.
Renewal of Chemours’permit NC0003573 will be addressed separately from this permit.

2. Receiving Waterbody Information
Receiving Waterbody Information
Outfalls/Receiving Stream(s): Outfall 003 – Cape Fear River
Stream Segment: 18-(26.25)
Stream Classification: WS-IV
Drainage Area (mi2): 4852

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Summer 7Q10 (cfs): 467 (17.14 – used in limit calculations to account for dilution,
the number is based on the modeling)
Winter 7Q10 (cfs): 603
30Q2 (cfs): 900
Average Flow (cfs): 4220
IWC (% effluent): 12.5% (based on the model, see item 6)
303(d) listed/parameter: No, the segment is not listed on the 2018 303(d) list
Subject to TMDL/parameter: Yes – State-wide Mercury TMDL implementation.
Sub-basin/HUC: Outfall 002: 03-06-16 /
USGS Topo Quad: Duart

3. Effluent Data Summary
N/A – New Discharge
This is a new permit for the collection and treatment of contaminated dry weather flow in a channel leading to
the Cape Fear River. Previously, DuPont used this channel to discharge process wastewater and referred to it
as “Old Outfall 002”.

4. Instream Data Summary
Instream monitoring may be required in certain situations, for example: 1) to verify model predictions
when model results for instream DO are within 1 mg/l of instream standard at full permitted flow; 2) to
verify model predictions for outfall diffuser; 3) to provide data for future TMDL; 4) based on other
instream concerns. Instream monitoring may be conducted by the Permittee, and there are also
Monitoring Coalitions established in several basins that conduct instream sampling for the Permittee (in
which case instream monitoring is waived in the permit as long as coalition membership is maintained).
If applicable, summarize any instream data and what instream monitoring will be proposed for this
permit action: As part of the Consent Order (Paragraph 11(d)), Chemours is required to sample its intake,
discharge (Outfall 002), and a multitude of additional on-site locations for PFAS compounds. These
sampling efforts are detailed in the Updated PFAS Characterization Plan, dated May 1, 2019. This plan
and the sampling locations were conditionally approved by DWR on June 19, 2019.
Chemours’ existing NPDES permit, NC0003573, has instream monitoring requirements for temperature,
dissolved oxygen, and conductivity on a weekly basis to evaluate the effects of its discharge on the
receiving stream. Chemours is a member of the Middle Cape Fear Basin Association, with upstream
coalition station B8290000 (approximately 1 mile upstream of Outfall 002) and downstream coalition
station B8302000 (approximately 4 miles downstream of Outfall 002). As part of this permit, instream
monitoring for PFAS compounds will be required.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (Y/N): Y

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Name of Monitoring Coalition: Middle Cape Fear Basin Association

5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): This is a new permit.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): This is a new permit.
Summarize the results from the most recent compliance inspection: This is a new permit.

6. Water Quality-Based Effluent Limitations (WQBELs)
Dilution and Mixing Zones
In accordance with 15A NCAC 2B.0206, the following stream flows are used for dilution considerations
for development of WQBELs: 1Q10 streamflow (acute Aquatic Life); 7Q10 streamflow (chronic Aquatic
Life; non-carcinogen HH); 30Q2 streamflow (aesthetics); annual average flow (carcinogen, HH).
If applicable, describe any other dilution factors considered (e.g., based on CORMIX model results):
Geosyntec Consultants of NC has submitted CORMIX model results on behalf of The Chemours
Company FC, LLC for the primary discharge Outfall 002 of their Fayetteville Works site discharging to
the Cape Fear River, classified WS-IV, approximately 1,500 feet above the William O Huskie Dam aka
Lock and Dam 3 in Bladen County. The discharge was modeled because of concerns over incomplete
mixing due to the presence of the lock and dam system and background concentrations from site runoff,
aerial deposition, seepage, and groundwater flow containing per-and polyfluoralkyl substances (PFAS)
into the river.
The CORMIX model river schematization used The Army Corps of Engineers 2016 bathymetric survey
data which showed a consistent river cross-section profile from the point of discharge to just above Lock
and Dam 3. Critical river flows were obtained from the USGS in June 2019, which showed a marked
decrease in critical flow statistics from those used in prior permits. The lower flows reflect changes in the
B. Everett Jordan Lake Drought Contingency Plan formally approved in 2008 and operationally in effect
since 2007. Water levels in the model were determined from the continuous record USGS stream gage
(Station 02105500) located at the lock and dam. Outfall parameters in the model were based on the
existing outfall configuration.
The model showed continued mixing up to 21.2 m from the outfall where the plume begins to exhibit
passive ambient diffusion with little additional dilution. At this point the effluent plume dilution is 8:1
until model end. The 8:1 dilution is used to establish dilution based effluent limitations for parameters
with little to no background concentrations. The 8:1 dilution is both more conservative than and
supported over instream waste concentration (IWC) based limitations normally performed under 15A
NCAC 2B. The IWC from using standard procedures under 7Q10 flow conditions of 467 cubic feet per
second (cfs) would be 9% versus 12.5% at an 8:1 dilution. The 8:1 dilution factor, modeled and
established for Chemours’ upstream discharge at Outfall 002 was used as a conservative estimate to
assess effluent limits and monitoring requirements for the discharge (Outfall 003) regulated in this permit.

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It should be noted that the model produced an effective summer 7Q10 (7Q10s) value of 17.14 cfs. This is
a very conservative assumption, as it is substantially lower than the USGS estimate of 467.0 cfs for the
7Q10s. Because the CORMIX model provides a very high level of protection for the receiving stream and
the downstream water users, the effective 7Q10s was be used in the Reasonable Potential Analysis (RPA)
for Outfall 003.

If applicable, describe any mixing zones established in accordance with 15A NCAC 2B.0204(b): N/A.
Oxygen-Consuming Waste Limitations
Limitations for oxygen-consuming waste (e.g., BOD) are generally based on water quality modeling to
ensure protection of the instream dissolved oxygen (DO) water quality standard. Secondary TBEL limits
(e.g., BOD= 30 mg/l for Municipals) may be appropriate if deemed more stringent based on dilution and
model results.
If permit limits are more stringent than TBELs, describe how limits were developed: See “Dilution and
Mixing Zones” Section above.
Ammonia and Total Residual Chlorine Limitations
Limitations for ammonia are based on protection of aquatic life utilizing an ammonia chronic criterion of
1.0 mg/l (summer) and 1.8 mg/l (winter). Acute ammonia limits are derived from chronic criteria,
utilizing a multiplication factor of 3 for Municipals and a multiplication factor of 5 for Non-Municipals.
Limitations for Total Residual Chlorine (TRC) are based on the NC water quality standard for protection
of aquatic life (17 ug/l) and capped at 28 ug/l (acute impacts). Due to analytical issues, all TRC values
reported below 50 ug/l are considered compliant with their permit limit.
Describe any proposed changes to ammonia and/or TRC limits for this permit renewal: The facility
conducted a comprehensive evaluation of the dry weather flow in the creek bed (channel) and submitted
results on the EPA Form 2D to the Division. The analysis indicates that there is no ammonia or TRC.

Reasonable Potential Analysis (RPA) for Toxicants
If applicable, conduct RPA analysis and complete information below.
The need for toxicant limits is based upon a demonstration of reasonable potential to exceed water quality
standards, a statistical evaluation that is conducted during every permit renewal utilizing the most recent
effluent data for each outfall. The RPA is conducted in accordance with 40 CFR 122.44 (d) (i). The NC
RPA procedure utilizes the following: 1) 95% Confidence Level/95% Probability; 2) assumption of zero
background; 3) use of ½ detection limit for “less than” values; and 4) stream flows used for dilution
consideration based on 15A NCAC 2B.0206. Effective April 6, 2016, NC began implementation of
dissolved metals criteria in the RPA process in accordance with guidance titled NPDES Implementation of
Instream Dissolved Metals Standards, dated June 10, 2016.
A reasonable potential analysis was conducted on effluent toxicant data provided by the facility in the
permit application. Pollutants of concern included toxicants with positive detections and associated water
quality standards/criteria. Based on this analysis, the following permitting actions are proposed for this
permit:
 Effluent Limit with Monitoring. The following parameters will receive a water quality-based
effluent limit (WQBEL) since they demonstrated a reasonable potential to exceed applicable
water quality standards/criteria: Silver and Cobalt.

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 Monitoring Only. The following parameters will receive a monitor-only requirement since they
did not demonstrate reasonable potential to exceed applicable water quality standards/criteria,
but the maximum predicted concentration was >50% of the allowable concentration: Cadmium,
Copper, Cyanide, Lead, Thallium, Selenium, Mercury.
 No Limit or Monitoring: The following parameters will not receive a limit or monitoring, since
they did not demonstrate reasonable potential to exceed applicable water quality
standards/criteria and the maximum predicted concentration was <50% of the allowable
concentration: Aluminum, Arsenic, Barium, Beryllium, Total Phenolic Compounds, Total
Chromium, Fluoride, Molybdenum, Nickel, Sulfate, Zinc, Nitrate/nitrite.

Attached are the RPA results and a copy of the guidance entitled “NPDES Implementation of Instream
Dissolved Metals Standards – Freshwater Standards.”
Toxicity Testing Limitations
Permit limits and monitoring requirements for Whole Effluent Toxicity (WET) have been established in
accordance with Division guidance (per WET Memo, 8/2/1999). Per WET guidance, all NPDES permits
issued to Major facilities or any facility discharging “complex” wastewater (contains anything other than
domestic waste) will contain appropriate WET limits and monitoring requirements, with several
exceptions. The State has received prior EPA approval to use an Alternative WET Test Procedure in
NPDES permits, using single concentration screening tests, with multiple dilution follow-up upon a test
failure.
Describe proposed toxicity test requirement: This is a Major Industrial facility, and a chronic WET limit
at 12.5% with quarterly frequency is established in the permit.

Mercury Statewide TMDL Evaluation
There is a statewide TMDL for mercury approved by EPA in 2012. The TMDL target was to comply
with EPA’s mercury fish tissue criteria (0.3 mg/kg) for human health protection. The TMDL established a
wasteload allocation for point sources of 37 kg/year (81 lb/year), and is applicable to municipals and
industrial facilities with known mercury discharges. Given the small contribution of mercury from point
sources (~2% of total load), the TMDL emphasizes mercury minimization plans (MMPs) for point source
control. Municipal facilities > 2 MGD and discharging quantifiable levels of mercury (>1 ng/l) will
receive an MMP requirement. Industrials are evaluated on a case-by-case basis, depending if mercury is a
pollutant of concern. Effluent limits may also be added if annual average effluent concentrations exceed
the WQBEL value (based on the NC WQS of 12 ng/l) and/or if any individual value exceeds a TBEL
value of 47 ng/l.
Describe proposed permit actions based on mercury evaluation: This is a new permit and the Division
has no historic data to conduct a comprehensive evaluation. The RPA does not indicate the need for a
limit and the effluent demonstrated compliance with the annual average Technology Based Effluent Limit
for mercury of 47.0 ng/L. No limit is required but quarterly monitoring is recommended to characterize
any groundwater and soil contamination that may exist from prior industrial activities at the site in
accordance with NPDES implementation of the mercury TMDL for industrial activities on a case-by-case
basis.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: N/A.

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Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs:
The Technology Based Effluent Limits were the guiding criteria used to develop permit limitations for
HFPO-DA, PFMOAA, and PMPA.
When EPA develops PFAS criteria or the State adopts standards for any of the compounds generated by
Chemours, the Division will conduct a reasonable potential analysis and reopen the permit to include the
new limits, if they are more stringent than the TBELs.
If applicable, describe any special actions (HQW or ORW) this receiving stream and classification shall
comply with in order to protect the designated waterbody.
If applicable, describe any compliance schedules proposed for this permit renewal in accordance with
15A NCAC 2H.0107(c)(2)(B), 40CFR 122.47, and EPA May 2007 Memo.
If applicable, describe any water quality standards variances proposed in accordance with NCGS 143-
215.3(e) and 15A NCAC 2B.0226 for this permit renewal: N/A.
7. Technology-Based Effluent Limitations (TBELs)
Describe what this facility produces: This is a surface/groundwater remediation permit for the Chemours
facility that produces organic chemicals.
List the federal effluent limitations guideline (ELG) for this facility: N/A.
If the ELG is based on production or flow, document how the average production/flow value was
calculated: N/A.
For ELG limits, document the calculations used to develop TBEL limits: N/A.
If any limits are based on best professional judgement (BPJ), describe development: N/A.
Document any TBELs that are more stringent than WQBELs: Initially, HFPO-DA and PFMOAA were
chosen as the two PFAS compounds that would be used to indicate reductions of Total PFAS in the
remediated surface water. As additional studies have been performed since the Consent Order, PMPA
has been added as an indicator parameter since the laboratory experiments demonstrated its low affinity
for GAC absorption. Therefore, TBELs for HFPO-DA, PFMOAA, and PMPA were calculated while
recognizing the Consent Order’s requirement that the treatment system removes at least 99% of HFPO-
DA and PFMOAA.

The 99% removal is also consistent with the NPDES permitting procedure for establishing BAT for waste
streams that don’t have promulgated Effluent Guidelines.

The facility provided an Engineering Report on Wastewater Treatability. The Report demonstrated that
the proposed GAC system is able to remove 99% of the total Table 3+ PFAS compounds (as listed in
NPDES permit application) present in the wastewater based on current analytical reporting limits and
influent concentrations. The GAC system showed that when indicator compounds PFMOAA, PMPA, and
HFPO-DA are removed at the rate of 99%, the Total Table 3+ compounds (as listed in NPDES
application) were also removed at the rate of 99% based on current analytical detection levels.

Data provided in the application showed dry weather baseflow to have influent concentrations for the two
indicator parameters at 6.0 µg/L for HFPA-DA, 85 µg/L for PFMOAA, and 5.4 µg/L for PMPA. This
was based on a single 24-hour composite influent sample. The dry weather flow (baseflow) will be treated

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utilizing three GAC units in series versus the typical two GAC unit in series to assure compliance with
permit limitations. The lead GAC bed will be changed out when PFMOAA in the influent to the lead
GAC unit equals PFMOAA effluent of the lead GAC unit. This will ensure full utilization of the carbon
bed. Chemours will test for PFMOAA between each GAC unit to determine when units need to be rotated
or disposed because this compound’s affinity to carbon is a bit less than HFPO-DA. This was tested out
during Chemours’ pilot scale study and a 99% reduction was maintained for all three compounds in the
lag (or third) GAC bed effluent. In accordance with the Engineering Report, the expected effluent at 99%
removal would be as follows:

HFPO-DA = (6.0 µg/L/100%) * 1% = 0.06 µg/L
PFMOAA = (85.0 µg/L/100%) * 1% = 0.85 µg/L
PMPA = (5.4 µg/L/100%) * 1% = 0.054 µg/L

Therefore, three limits will be placed on the PFAS indicator parameters in the new permit. First, HFPO-
DA, PFMOAA, and PMPA TBELs of 0.06 µg/L, 0.85 µg/L, and 0.054 µg/L respectively. This is based
on Chemours data provided in the application and pilot study.

In addition, and as required by the Consent Order, the treatment system will have to demonstrate 99%
removal for HFPO-DA, PFMOAA, and PMPA based on monthly average concentration data.

% 𝑅𝑒𝑙𝑙𝑡𝑎𝑙= 𝐼𝑙𝑒𝑙𝑡𝑒𝑙𝑡−𝐸𝑒𝑒𝑙𝑡𝑒𝑙𝑡
𝐼𝑙𝑒𝑙𝑡𝑒𝑙𝑡

Where: Influent = monthly average influent concentration
Effluent = monthly average effluent concentration

This percent removal will be reported monthly with Chemours electronic Discharge Monitoring Report
(eDMR) data. If the influent HFPO-DA or PFMOAA concentrations to the water treatment system are
equal to or less than 200 ng/L and 500 ng/L, respectively, then the water treatment system effluent
concentrations of less than the current reporting limits (2 ng/L and 5 ng/L, respectively) shall be
considered as achieving 99% removal.
The addition of PMPA as an indicator parameter may require additional carbon treatment units and
Chemours has committed to making the necessary improvements to the treatment system and complying
with the PMPA technology based effluent permit limits by Jan. 31, 2021. All other limits are effective
upon commencement of discharge. Furthermore, since these are technology based effluent limits, if
appropriate, after 3 years of treatment system operation the division will evaluate effluent limits and
adjust the limits if the analysis indicates an improved performance.

Document any TBELs that are less stringent than previous permit: N/A. This is a new permit.

8. Antidegradation Review (New/Expanding Discharge)
The objective of an antidegradation review is to ensure that a new or increased pollutant loading will not
degrade water quality. Permitting actions for new or expanding discharges require an antidegradation
review in accordance with 15A NCAC 2B.0201. Each applicant for a new/expanding NPDES permit
must document an effort to consider non-discharge alternatives per 15A NCAC 2H.0105(c)(2). In all
cases, existing instream water uses and the level of water quality necessary to protect the existing use is
maintained and protected.

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If applicable, describe the results of the antidegradation review, including the Engineering Alternatives
Analysis (EAA) and any water quality modeling results: The facility provided an EAA to justify the
chosen disposal alternative for this new discharge; the complete EAA document can be found within the
application in DWR’s Laserfiche files.

The facility reviewed the following available alternatives: Connection to the Existing Publicly Owned
Treatment Works (POTW), Land Application, Wastewater Reuse in the Facility, Trucking Offsite, and
Direct Discharge.

Connection to the existing POTW was not available since the nearest Rockfish Creek Water Reclamation
Facility refused to accept this wastewater. Reuse is currently not a feasible option, because, including but
not limited to, - the Consent Order requires Chemours to accelerated reduction of PFAS contamination in
the Cape Fear River and downstream water intakes within a two-year period, and it would be difficult for
Chemours to implement this in an accelerated manner. Chemours may evaluate this alternative more
closely in the future.

The Present Value Costs for the next 20 years was calculated for the following alternatives using an EPA
discount factor of 3.5%; the Costs are presented below:

Land Application – $86,000,000
Wastewater Reuse in the Facility - $69,600,000 (includes riparian restoration; Concerns with this
alternative include the riparian damage and distance from the capture dam to the facility)
Trucking Offsite - $8,710,000,000
Direct Discharge- $67,000,000

As compared to other alternatives, and in accordance with 15A NCAC 2H .0105(c)(2), the Engineering
Alternatives Analysis provided justification for a direct discharge to surface water alternative and
indicated that the direct discharge is the most environmentally sound alternative selected from all
reasonably cost-effective options.

9. Antibacksliding Review
Sections 402(o)(2) and 303(d)(4) of the CWA and federal regulations at 40 CFR 122.44(l) prohibit
backsliding of effluent limitations in NPDES permits. These provisions require effluent limitations in a
reissued permit to be as stringent as those in the previous permit, with some exceptions where limitations
may be relaxed (e.g., based on new information, increases in production may warrant less stringent TBEL
limits, or WQBELs may be less stringent based on updated RPA or dilution).
Are any effluent limitations less stringent than previous permit (YES/NO): N/A. This is a new permit.
If YES, confirm that antibacksliding provisions are not violated: N/A.

10. Monitoring Requirements
Monitoring frequencies for NPDES permitting are established in accordance with the following
regulations and guidance: 1) State Regulation for Surface Water Monitoring, 15A NCAC 2B.0500; 2)
NPDES Guidance, Monitoring Frequency for Toxic Substances (7/15/2010 Memo); 3) NPDES Guidance,
Reduced Monitoring Frequencies for Facilities with Superior Compliance (10/22/2012 Memo); 4) Best
Professional Judgement (BPJ). Per US EPA (Interim Guidance, 1996), monitoring requirements are not
considered effluent limitations under Section 402(o) of the Clean Water Act, and therefore anti-
backsliding prohibitions would not be triggered by reductions in monitoring frequencies.

Page 12 of 25

For instream monitoring, refer to Section 4.

11. Electronic Reporting Requirements
The US EPA NPDES Electronic Reporting Rule was finalized on December 21, 2015. Effective
December 21, 2016, NPDES regulated facilities are required to submit Discharge Monitoring Reports
(DMRs) electronically. Effective December 21, 2020, NPDES regulated facilities will be required to
submit additional NPDES reports electronically. This permit contains the requirements for electronic
reporting, consistent with Federal requirements.

12. Summary of Proposed Permitting Actions

Parameter Current Permit Proposed Change Basis for Condition/Change
Flow N/A (new permit) MA 1.58 MGD 15A NCAC 2B .0505
BOD5 N/A (new permit) MA 30.0 mg/L
DM 45.0 mg/L

WQBEL. Based on protection of DO
standard. 15A NCAC 2B.0200

TSS N/A (new permit) MA 30.0 mg/L
WA 45.0 mg/L
TBEL. Best Professional Judgement.
Temperature N/A (new permit) The ambient water
temperature to exceed
32°C
WQBEL. State WQ standard, 15A
NCAC 2B .0200
DO N/A (new permit) Weekly
upstream/downstream
Monitoring Only
WQBEL. State WQ standard, 15A
NCAC 2B .0200
HFPO-DA (GenX) N/A (new permit) MA 0.06 µg/L
DM 0.06 µg/L
TBEL, based on the Consent Order
and BPJ/BAT
PFMOAA N/A (new permit) MA 0.85 µg/L
DM 0.85 µg/L
TBEL, based on the Consent Order
and BPJ/BAT
PMPA N/A (new permit) MA 0.054 µg/L
DM 0.054 µg/L
TBEL, based on the Consent Order
and BPJ/BAT
PFAS compounds
(Table 3+ and/or
EPA Method 357
mod)
N/A (new permit) Effluent and Intake
Monitoring Only
(variable frequencies)
Based on the Consent Order
pH N/A (new permit) 6.0 – 9.0 SU WQBEL. State WQ standard, 15A
NCAC 2B .0200

Page 13 of 25

Parameter Current Permit Proposed Change Basis for Condition/Change
Total Phosphorus N/A (new permit) Monthly Effluent
Monitoring Only
State WQ Rule, 15A NCAC 2B
.0500
Conductivity N/A (new permit) Monthly
upstream/downstream
Monitoring Only
State WQ Rule, 15A NCAC 2B
.0500
Toxicity Test N/A (new permit) Chronic limit, 12.5%
effluent
WQBEL. No toxics in toxic
amounts. 15A NCAC 2B.0200 and
15A NCAC 2B.0500
Total Hardness N/A (new permit) Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Selenium N/A (new permit)

Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Silver N/A (new permit)

MA 0.48 µg/L
DM 2.01 µg/L
State WQ standard, 15A NCAC 2B
.0200
Total Cobalt N/A (new permit)

MA 23.9 µg/L
DM 23.9 µg/L
State WQ standard, 15A NCAC 2B
.0200
Total Cadmium N/A (new permit)

Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Copper N/A (new permit)

Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Cyanide N/A (new permit)

Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Lead N/A (new permit Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Thallium N/A (new permit) Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Mercury N/A (new permit) Quarterly Effluent
Monitoring Only
2012 State TMDL and NPDES
Implementation Guidance.
Electronic
Reporting
N/A (new permit) Required In accordance with EPA Electronic
Reporting Rule 2015.
MGD – Million gallons per day, MA – Monthly Average, DM – Daily Max

Page 14 of 25

13. Public Notice Schedule
Permit to Public Notice: 07/06/2020

Per 15A NCAC 2H .0109 & .0111, The Division will receive comments for a period of 30 days following
the publication date of the public notice. Any request for a public hearing shall be submitted to the
Director within the 30 days comment period indicating the interest of the party filing such request and the
reasons why a hearing is warranted.

14. NPDES Division Contact
If you have questions regarding any of the above information or on the attached permit, please contact
Sergei Chernikov at [phone] or via email at [e-mail].

15. Fact Sheet Attachments (if applicable)
 RPA Sheets
o Input Sheet
o Data Sheets
o RPA Sheet
o Dissolved to Total Metal Calculator Sheet
 NPDES Implementation of Instream Dissolved Metals Standards – Freshwater Standards
 Safety Data Sheets (SDSs) for the chemicals to be utilized at the wastewater treatment system
 Responses to Comments

16. Changes in the Final Permit
 The filter backwash was added to the list of waste streams on the Supplement to Permit Cover
Sheet.
 The document entitled “Responses to Comments” was developed and attached to the Fact Sheet.
 A provision was added to the Permit that suspends monitoring for DFSA, MMF, MTP, and PPF
Acid until an appropriate testing methodology is established.

Page 15 of 25

Responses to the Comments

Chemours Permit NC0089915

September 11, 2020

In order to reduce PFAS loading to the Cape Fear River, this Permit requires the treatment of dry weather base flow
from a contaminated stream. This stream, often referred to as “Old Outfall 002,” was used to discharge process
wastewater from the facility prior to June 2012, when the process wastewater discharge was relocated to the current
outfall location (permit NC0003573) above Lock and Dam #3 in the Cape Fear River. The treated stream base flow,
covered in this permit, will be discharged from Outfall 003 which will be located downstream of the capture dam,
and will flow from the channel into the Cape Fear River below Lock and Dam #3. The flow from Outfall 003 must
be treated to remove at least 99% of the PFAS in the stream. This removal efficiency will be demonstrated through
measurements of indicator parameters HFPO-DA (GenX), PFMOAA, and PMPA. The issuance of this permit will
allow Chemours to begin remediation of the stream and without the permit, the contaminated surface water will
continue to discharge to the Cape Fear River untreated.

SELC Comments

Comment:
Technology-based effluent limits must be based on the reductions achievable by the
technology.

Response:
The DEQ has used professional judgement and experience in establishing Technology Based
Effluent Limits for GenX, PMPA, and PFMOAA after evaluation of all data presented in the
engineering report.

1). Review of the Engineering Report and Addendum to the Report indicates that the effluent
concentrations of indicator PFAS compounds (PFMOAA and HFPO-DA) are highly variable
depending on the type of the GAC used and other factors. PFMOAA concentration varies from
<10.6 ng/L to 31,059 ng/L and HFPO-DA varies from <11.7 ng/L to 4,622 ng/L. Such a
significant variation shows that even under tightly controlled laboratory conditions the
treatment technology must be optimized for the facility to meet the permit limits, which are
much closer to the lower end of the identified range of the effluent concentrations (60 ng/L for
HFPO-DA and 850 ng/L for PFMOAA). Moreover, these numeric standards serve as a backstop
to the requirement that Chemours control PFAS indicator parameters at an overall efficiency of
99%.

2). The study performed by the consultants was conducted under predictable and controlled
laboratory conditions on a small scale during a short time period. When this technology is
implemented in the field, there will be additional complications that could have a negative
impact on the performance, including: variation in temperature (daily and seasonal); variations
in the influent pH, volume, TSS, oxidation-reduction potential, additional chemical compounds
impacting GAC, etc. Additional difficulties might be encountered during scaling-up the
technology from the lab to the field.

3). In addition, the facility will encounter substantial treatment difficulties as the influent
concentration of the PFAS compounds decreases. Consistent removal of 99% of the compounds
in the influent becomes more difficult as the wastewater coming to the treatment system
becomes less polluted. The DEQ has observed these difficulties with numerous facilities and
parameters.

Page 16 of 25

4). When EPA develops Effluent Guidelines, they rely on the data obtained from implemented
and successfully operating technologies. For example, the latest update for the 40 CFR 423
(Power Plants) was based on the multiyear data collection from existing facilities in North
Carolina and in other states and countries. In this case, the application of the treatment
system is new and DEQ does not have reliable field data from any other similar facility, which
significantly increases uncertainty, and diminishes our ability to reliably predict the PFAS
effluent concentrations.

5). In addition, EPA recommends using the 95th percentile for Monthly Average limits that are
based on the performance when the Effluent Guidelines are not available. The proposed limits
are even tighter since Monthly Average and Daily Maximum limits in this permit are based on
the 99th percentile.

6). The DEQ proposes to re-evaluate the data after 3 years of the GAC treatment system
operations. The DEQ will reduce the limits if the facility demonstrates ability to consistently
achieve levels that are lower than the proposed limits. It is necessary to emphasize that the
wastewater treatment operations need time to optimize their performance. It is especially
important for a new technology with a very limited application history.

7). The permit requires the facility to meet the permit limits and other terms and conditions
regardless of the maintenance and replacement schedules. The facility is authorized to make
decisions regarding wastewater treatment that will result in achieving full compliance with the
permit limits.

The fact sheet is not an enforceable document. It simply describes operation of the treatment
system and provides the rationale for the permitting decisions.

Comment:
The draft permit limits allow for inadequate pollution control.

Response:
Please see responses to the first comment.

Comment:
The Draft Permit Limits Are Too High, Particularly Considering the Historic Exposure of
Downstream Communities.

Response:
The DEQ established the limits based on the ability of the existing technology to treat the
wastewater. Furthermore, the numeric limits serve as a backstop to the Consent Order
requirement that Chemours remove PFAS at an efficiency of 99%. Please see responses to the
first comment.

Comment:
The Permit Must Include a Condition to Control Other PFAS if Monitoring Reveals That
Reductions in the PFMOAA, GenX, and PMPA Do Not Represent Reductions in the Full Suite of
PFAS.

Response:
The Engineering Report provided by the facility clearly demonstrates that the chosen indicator
parameters represent the most difficult PFAS compounds to be treated because they are the
short-chained molecules and if they are removed at 99% rate the other PFAS compounds will
also be removed at a 99% rate or higher.

The permit contains provision that allows DEQ to re-evaluate performance of the facility and
make necessary changes to the permit.

Page 17 of 25

Comment:
The Permit Cannot Allow for Less Than 99 Percent Removal of PFAS.

Response:
The Permit does not currently allow for less than 99% removal of PFAS. As the concentration of
the PFAS compounds in the influent decreases, the ability of the treatment system to remove
contaminants also decreases. This statement is true for the vast majority of the contaminants.
Therefore, the permit provides the facility an opportunity to request revisions to the permit
condition that require 99% removal efficiency. The DEQ will evaluate such a request and make
a decision based on the available data. Even if such a request is granted, the numeric effluent
limits will be maintained. These numeric limitations represent Technology Based Effluent
Limits and they will not be violated by changing removal efficiency requirements.

Comment:
DEQ Must Do More.

Response:
This comment is outside of the issues related to the subject permit.

CFPUA and Brooks Pierce Comments

Comment:
Chemours' draft NPDES Permit would allow the discharge of 1.5 million gallons per day of
wastewater resulting from a proposed treatment system for old Outfall 002 with a total
concentration of 954 ppt of GenX, PFMOAA, and PMPA. There is no limit on the total mass of
these compounds that can be discharged. CFPUA objects to excessive concentration of these
compounds that can be discharged and failure to limit the mass that can be discharged.

Response:
The DEQ is not authorizing the discharge of any additional wastewater into the Cape Fear
River. Rather, this permit requires the removal of PFAS from a contaminated stream that is
already discharging into the Cape Fear River.

The DEQ established permit limits that are based on the engineering evaluation of the
treatment system that controls PFAS pollutants. The Clean Water Act requires that DEQ
protects the receiving stream from the toxic impacts of the effluent. The toxic impact evaluation
relies on the concentration-based water quality standard promulgated by the state and
concentration-based water quality criteria promulgated by the EPA. To achieve this goal, the
Draft Permit contains concentration-based limits. The mass-based limits are typically
implemented when the Federal Effluent Guidelines exist for a particular industry or as a result
of the TMDL. There are no applicable Federal Effluent Guidelines or TMDLs here.

Comment:
CFPUA objects to the high limits set for the three compound listed and the absence of limits on
the remaining Full Suite of PFAS compounds.

Response:
The Engineering Report provided by the facility clearly demonstrates that chosen indicator
parameters represent the most difficult PFAS compounds to be treated because they are the
short-chained molecules and if they are removed at 99% rate the other PFAS compounds will
also be removed at 99% rate or higher.

Hence, by imposing 99% removal efficiency on these indicator parameters the DEQ also
imposes 99% removal efficiency on all PFAS compounds contained in the effluent.

Page 18 of 25

Comment:
Why did DEQ decide not to establish limits for the other 17 PFAS compounds in Table 3+?
Response:
The DEQ has chosen three indicator parameters that have short-chained molecules that are
present in high concentrations and are the most difficult to remove. Experiments indicate that
if they are removed at 99% rate the other PFAS compounds will also be removed at 99% rate or
higher.

Comment:
The proposed treatment system is to be completed by September 30, 2020. Yet Chemours
already is admitting that it cannot meet the effluent limits by that time for PMPA, one of the
three compounds that have effluent limits in the permit. Instead, Chemours is asking for more
time, until January 31, 2021.
Response:
The additional time is needed for installation of a sufficient capacity to the treatment system to
ensure 99% removal efficiency for all PFAS compounds. However, this delay will not have a
significant impact on the overall PFAS load reduction. Also, even the existing system will be
removing PMPA from the effluent with approximately 98% efficiency during the additional time
needed to meet the 99% target.
Comment:
CFPUA objects to the inadequate baseline used to develop this permit.

Design of the treatment system was based on a "single 24-hour composite influent sample,"
which hardly gives confidence in the potential effectiveness.
Response:
Despite the limited data set, the facility is still obligated to meet numeric limits and 99%
removal efficiency requirements for three indicator parameters. The implementation of this
permit would result in removal of approximately 20% of the overall PFAS load from the
Chemours facility to the Cape Fear River.

The DEQ will re-evaluate the effluent limits after collecting long-term data.

Comment:
CFPUA objects to the issuance of this permit without clarity on how backwash water will be
handled.

Response:
The Supplement to the Permit Cover Sheet (page 2 of the permit) has been expanded to state
that only treated backwash can be discharged from Outfall 003.

The Fact Sheet explains that the treatment design includes Ultrafiltration (UF) pretreatment
before the Granular Activated Carbon (GAC) stage. The UF will perform the role of solids
removal upstream of the GAC units. The UF back pulse waste recycle will be captured in a
weir tank to allow solids to settle and then will be recycled through the system after being
pumped back to the influent oxidation/coagulation /pH adjustment tank. The settled solids in
the weir tank (the back-pulse waste recycle tank) will be drawn off by a sludge pump and
filtered in downstream removal processes (thickener and rotary-fan filter press).

In addition, while the Fact Sheet recognizes that the GAC units have backwashing capability,
Chemours only plans to backwash a GAC unit when installing virgin carbon during the change

Page 19 of 25

out, about once every 3-6 months. This backwash water will be discharged to the weir tank to
allow solids to settle as described above.

The permit allows the facility to discharge wastewater only after treatment and when it meets
effluent limits. These conditions apply to the backwash.

Comment:
The removal efficiency is to be calculated only monthly, even though samples are collected
twice per month. CFPUA objects to this permit only requiring calculation of removal efficiency
once per month.

Response:
The removal efficiency calculation is based on the long-standing implementation structure of
the Clean Water Act that requires monthly submission of the Discharge Monitoring Reports. It
allows for the time needed for sample shipment and analysis.

Comment:
CFPUA believes the discharge to the Cape Fear River should be limited to the same 70/10
analysis that applies to what is considered safe water that is being withdrawn by neighboring
groundwater users.

Response:
Effluent limits and other conditions in the permit are based on the federal and state NPDES
regulations and surface water standards.

Environment North Carolina Comment

Comment:
NCDEQ should consider including conditions with more stringent limits.
Response:
The DEQ believes that the proposed limits adequately represent the ability of the treatment
system to remove PFAS compounds. This conclusion is based on limited available data. DEQ
will re-evaluate these limits after the long-term performance data are collected.

Chemours Comments

Comment:
The effluent limits and 99% removal efficiency requirement for PMPA are arbitrary and not
provided for in the Consent Order.

Response:
The Consent Order identifies PFMOAA and GenX as “indicator parameters” that are intended
to be reflective of reductions in all PFAS at the facility. In addition, the Renewal Application
submitted by Chemours clearly stated that “Treatment testing demonstrated that other PFAS
compounds in the Table 3+ and EPA Mod 537 Max analyses were removable by at least 99%
when PFMOAA and HFPO-DA are removed by 99%”. Furthermore, to the extent the permit
imposes requirements in addition to those set forth in the Consent Order, the DEQ has the
legal authority to go above and beyond the terms of the Order

Comment:
The daily maximum effluent limits for PFAS indicator parameters should not be set equal to the
monthly average effluent limits.

Response:

Page 20 of 25

The DEQ is required by 40 CFR 122.45 (d) to establish daily maximum limitations. The facility
recommends for DEQ to use long-term data. However, this information is not available since
this is a new treatment system. In the absence of the long-term data, the DEQ must use the
same number for Daily Maximum and Monthly Average limits.

Comment:
The effluent limits for PFAS indicator parameters should not be adjusted to become more
stringent after three years.

Response:
The decision to modify effluent limits has not been made. It is contingent upon comprehensive
evaluation of the long-term performance data. It is premature to speculate about potential
future decisions.

The limits established in this permit are based on the limited data set and future modifications
might be needed to reflect the true operational efficiency of the treatment system.

Comment:
The PFAS monitoring requirements in Permit section A.(5.) should be revised.

Response:
The monitoring frequency in the permit is established to fully evaluate impact of the facility on
the receiving stream, efficiency of the treatment system, and facility’s compliance. The
frequency is consistent with other facilities in similar circumstances and cannot be reduced
until the long-term data is obtained.

If the permit conditions are redundant to the Consent Order, the facility does not have to
repeat sampling. It can report the same results to satisfy sampling requirements of both
documents. In addition, the permit for the facility is issued for 5 years and the Consent Order
might be terminated prior to that date. Therefore, instream sampling requirements shall
remain in the permit.

In regard to the four compounds (DFSA, MMF, MTP, and PPF Acid) that are difficult to
accurately measure, the permit can be modified with the appropriate condition.

Comment:
Chemours requests that DEQ add a provision to the Permit allowing Chemours to apply to
DEQ for modifications of the PFAS monitoring requirements, based on monitoring results or
analytical method changes.

Response:
The facility already has the right to apply for modifications under the existing rules and
regulations. Incorporating such statement in the permit is redundant and unnecessary.

Public Comments

We also received 28 comments from individual citizens or families; 26 letters oppose the permit
and 2 support the permit. Most of the opposition is absolute; they don’t want permit to allow
any discharge. However, there are a few comments that want to reduce permit limits to 20 ppt,
although this number is not explained.

Many comments are not directly related to the permit. They request installation of in-house
filters, establishment of a compensation fund, addressing general water quality issues, etc.
These comments have been counted as opposing the permit.

Page 21 of 25

NPDES Implementation of Instream Dissolved Metals Standards – Freshwater Standards
The NC 2007-2015 Water Quality Standard (WQS) Triennial Review was approved by the NC
Environmental Management Commission (EMC) on November 13, 2014. The US EPA subsequently
approved the WQS revisions on April 6, 2016, with some exceptions. Therefore, metal limits in draft permits
out to public notice after April 6, 2016 must be calculated to protect the new standards - as approved.
Table 1. NC Dissolved Metals Water Quality Standards/Aquatic Life Protection
Parameter Acute FW, µg/l
(Dissolved)
Chronic FW, µg/l
(Dissolved)
Acute SW, µg/l
(Dissolved)
Chronic SW, µg/l
(Dissolved)

Arsenic 340 150 69 36
Beryllium 65 6.5 --- ---
Cadmium Calculation Calculation 40 8.8
Chromium III Calculation Calculation --- ---
Chromium VI 16 11 1100 50
Copper Calculation Calculation 4.8 3.1
Lead Calculation Calculation 210 8.1
Nickel Calculation Calculation 74 8.2
Silver Calculation 0.06 1.9 0.1
Zinc Calculation Calculation 90 81

Table 1 Notes:
1. FW= Freshwater, SW= Saltwater
2. Calculation = Hardness dependent standard
3. Only the aquatic life standards listed above are expressed in dissolved form. Aquatic life
standards for Mercury and selenium are still expressed as Total Recoverable Metals due to
bioaccumulative concerns (as are all human health standards for all metals). It is still
necessary to evaluate total recoverable aquatic life and human health standards listed in 15A
NCAC 2B.0200 (e.g., arsenic at 10 µg/l for human health protection; cyanide at 5 µg/L and
fluoride at 1.8 mg/L for aquatic life protection).

Table 2. Dissolved Freshwater Standards for Hardness-Dependent Metals
The Water Effects Ratio (WER) is equal to one unless determined otherwise under
15A NCAC 02B .0211 Subparagraph (11)(d)

Metal NC Dissolved Standard, µg/l
Cadmium, Acute WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151 [ln hardness]-
3.1485}
Cadmium, Acute Trout
waters
WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151[ln hardness]-
3.6236}
Cadmium, Chronic WER*{1.101672-[ln hardness](0.041838)} ∙ e^{0.7998[ln hardness]-
4.4451}
Chromium III, Acute WER*0.316 ∙ e^{0.8190[ln hardness]+3.7256}
Chromium III, Chronic WER*0.860 ∙ e^{0.8190[ln hardness]+0.6848}
Copper, Acute WER*0.960 ∙ e^{0.9422[ln hardness]-1.700}

Page 22 of 25

Copper, Chronic WER*0.960 ∙ e^{0.8545[ln hardness]-1.702}
Lead, Acute WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]-
1.460}
Lead, Chronic WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]-
4.705}
Nickel, Acute WER*0.998 ∙ e^{0.8460[ln hardness]+2.255}
Nickel, Chronic WER*0.997 ∙ e^{0.8460[ln hardness]+0.0584}
Silver, Acute WER*0.85 ∙ e^{1.72[ln hardness]-6.59}
Silver, Chronic Not applicable
Zinc, Acute WER*0.978 ∙ e^{0.8473[ln hardness]+0.884}
Zinc, Chronic WER*0.986 ∙ e^{0.8473[ln hardness]+0.884}

General Information on the Reasonable Potential Analysis (RPA)
The RPA process itself did not change as the result of the new metals standards. However,
application of the dissolved and hardness-dependent standards requires additional consideration in
order to establish the numeric standard for each metal of concern of each individual discharge.
The hardness-based standards require some knowledge of the effluent and instream (upstream)
hardness and so must be calculated case-by-case for each discharge.
Metals limits must be expressed as ‘total recoverable’ metals in accordance with 40 CFR 122.45(c).
The discharge-specific standards must be converted to the equivalent total values for use in the RPA
calculations. We will generally rely on default translator values developed for each metal (more on
that below), but it is also possible to consider case-specific translators developed in accordance with
established methodology.

RPA Permitting Guidance/WQBELs for Hardness-Dependent Metals - Freshwater
The RPA is designed to predict the maximum likely effluent concentrations for each metal of concern, based
on recent effluent data, and calculate the allowable effluent concentrations, based on applicable standards and
the critical low-flow values for the receiving stream.
If the maximum predicted value is greater than the maximum allowed value (chronic or acute), the
discharge has reasonable potential to exceed the standard, which warrants a permit limit in most
cases. If monitoring for a particular pollutant indicates that the pollutant is not present (i.e.
consistently below detection level), then the Division may remove the monitoring requirement in the
reissued permit.
1. To perform a RPA on the Freshwater hardness-dependent metals the Permit Writer
compiles the following information:
 Critical low flow of the receiving stream, 7Q10 (the spreadsheet automatically
calculates the 1Q10 using the formula 1Q10 = 0.843 (s7Q10, cfs) 0.993
 Effluent hardness and upstream hardness, site-specific data is preferred
 Permitted flow

Page 23 of 25

 Receiving stream classification

2. In order to establish the numeric standard for each hardness-dependent metal of concern
and for each individual discharge, the Permit Writer must first determine what effluent and
instream (upstream) hardness values to use in the equations.

The permit writer reviews DMR’s, Effluent Pollutant Scans, and Toxicity Test results for any
hardness data and contacts the Permittee to see if any additional data is available for
instream hardness values, upstream of the discharge.

If no hardness data is available, the permit writer may choose to do an initial evaluation
using a default hardness of 25 mg/L (CaCO3 or (Ca + Mg)). Minimum and maximum limits
on the hardness value used for water quality calculations are 25 mg/L and 400 mg/L,
respectively.

If the use of a default hardness value results in a hardness-dependent metal showing
reasonable potential, the permit writer contacts the Permittee and requests 5 site-specific
effluent and upstream hardness samples over a period of one week. The RPA is rerun using
the new data.

The overall hardness value used in the water quality calculations is calculated as follows:
Combined Hardness (chronic)
= (Permitted Flow, cfs *Avg. Effluent Hardness, mg/L) + (s7Q10, cfs *Avg. Upstream Hardness, mg/L)
(Permitted Flow, cfs + s7Q10, cfs)
The Combined Hardness for acute is the same but the calculation uses the 1Q10 flow.
3. The permit writer converts the numeric standard for each metal of concern to a total
recoverable metal, using the EPA Default Partition Coefficients (DPCs) or site-specific
translators, if any have been developed using federally approved methodology.

EPA default partition coefficients or the “Fraction Dissolved” converts the value for
dissolved metal at laboratory conditions to total recoverable metal at in-stream
ambient conditions. This factor is calculated using the linear partition coefficients
found in The Metals Translator: Guidance for Calculating a Total Recoverable
Permit Limit from a Dissolved Criterion (EPA 823-B-96-007, June 1996) and the
equation:

_Cdiss__ = _______1_______________
Ctotal 1 + { [Kpo] [ss(1+a)] [10-6] }

Where:
ss = in-stream suspended solids concentration [mg/l], minimum of 10 mg/L used,
and
Kpo and a = constants that express the equilibrium relationship between dissolved
and adsorbed forms of metals. A list of constants used for each hardness-
dependent metal can also be found in the RPA program under a sheet labeled
DPCs.

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4. The numeric standard for each metal of concern is divided by the default partition
coefficient (or site-specific translator) to obtain a Total Recoverable Metal at ambient
conditions.

In some cases, where an EPA default partition coefficient translator does not exist (ie.
silver), the dissolved numeric standard for each metal of concern is divided by the EPA
conversion factor to obtain a Total Recoverable Metal at ambient conditions. This method
presumes that the metal is dissolved to the same extent as it was during EPA’s criteria
development for metals. For more information on conversion factors see the June, 1996
EPA Translator Guidance Document.

5. The RPA spreadsheet uses a mass balance equation to determine the total allowable
concentration (permit limits) for each pollutant using the following equation:

Ca = (s7Q10 + Qw) (Cwqs) – (s7Q10) (Cb)
Qw
Where: Ca = allowable effluent concentration (µg/L or mg/L)
Cwqs = NC Water Quality Standard or federal criteria (µg/L or mg/L)
Cb = background concentration: assume zero for all toxicants except NH3* (µg/L or mg/L)
Qw = permitted effluent flow (cfs, match s7Q10)
s7Q10 = summer low flow used to protect aquatic life from chronic toxicity and human health
through the consumption of water, fish, and shellfish from noncarcinogens (cfs)
* Discussions are on-going with EPA on how best to address background concentrations

Flows other than s7Q10 may be incorporated as applicable:
1Q10 = used in the equation to protect aquatic life from acute toxicity
QA = used in the equation to protect human health through the consumption of water, fish,
and shellfish from carcinogens
30Q2 = used in the equation to protect aesthetic quality

6. The permit writer enters the most recent 2-3 years of effluent data for each pollutant of
concern. Data entered must have been taken within four and one-half years prior to the date
of the permit application (40 CFR 122.21). The RPA spreadsheet estimates the 95th
percentile upper concentration of each pollutant. The Predicted Max concentrations are
compared to the Total allowable concentrations to determine if a permit limit is necessary. If
the predicted max exceeds the acute or chronic Total allowable concentrations, the discharge
is considered to show reasonable potential to violate the water quality standard, and a permit
limit (Total allowable concentration) is included in the permit in accordance with the U.S.
EPA Technical Support Document for Water Quality-Based Toxics Control
published in 1991.

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7. When appropriate, permit writers develop facility specific compliance schedules in
accordance with the EPA Headquarters Memo dated May 10, 2007 from James Hanlon to
Alexis Strauss on 40 CFR 122.47 Compliance Schedule Requirements.

8. The Total Chromium NC WQS was removed and replaced with trivalent chromium and
hexavalent chromium Water Quality Standards. As a cost savings measure, total chromium
data results may be used as a conservative surrogate in cases where there are no analytical
results based on chromium III or VI. In these cases, the projected maximum concentration
(95th %) for total chromium will be compared against water quality standards for chromium
III and chromium VI.

9. Effluent hardness sampling and instream hardness sampling, upstream of the discharge, are
inserted into all permits with facilities monitoring for hardness-dependent metals to ensure
the accuracy of the permit limits and to build a more robust hardness dataset.

10. Hardness and flow values used in the Reasonable Potential Analysis for this permit included:
Parameter Value Comments (Data Source)
Average Effluent Hardness (mg/L)
[Total as, CaCO3 or (Ca+Mg)] 25.0 Default value
Average Upstream Hardness
(mg/L)
[Total as, CaCO3 or (Ca+Mg)]
25.0 Default value
7Q10 summer (cfs) 17.14 CORMIX model, 8:1dilution
1Q10 (cfs) 14.16 RPA calculation
Permitted Flow (MGD) 1.58 Design flow of treatment system