NC0004952_Fact Sheet_20210625 (2)

Fact Sheet
NPDES Permit No. NCOOO4952
Permit Writer/Email Contact: [e-mail]
Date: October 15, 2020
Division/Branch: NC Division of Water Resources / NPDES Complex Permitting
Fact Sheet Template: Version 09Jan2017
Permitting Action:
❑X 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:
CNA Holdings
Applicant Address:
2525 Blacksburg Road, Grover, NC 28073
Facility Address:
2525 Blacksburg Road, Grover, NC 28073
Permitted Flow:
0.45 MGD
Facility Type/Waste:
MAJOR Industrial
Facility Class:
II
Treatment Units:
Bar screen & grit chamber; Three equalization basins utilizing pH
adjustment; Emergency equalization tank; Two aeration basins with
chlorine added on an as -needed basis;
Two secondary clarifiers with polymer addition; Dual media tertiary
filter; Waste activated sludge digester; Two (2) sludge ponds; and Three
(3) polishing ponds.
Pretreatment Program (Y/N):
N/A
County:
Cleveland
Region:
Mooresville
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Briefly describe the proposed permitting action and facility background:
CNA Holdings manufactures thermoplastic and elastomer polyester resins at the Shelby facility. Fibers
Innovators International is also located at the site and manufactures sewing thread. Process wastewaters
from Fibers Innovators International is treated at the Shelby Facility WWTP. The facility is classified
under SIC codes 2824 (manmade organic fibers, except cellulosic) and 2821 (synthetic resins, plastic
materials and non-vulcanizable elastometers). This facility is subject to Effluent Guidelines in 40 CFR
414 — Organic Chemicals, Plastics and Synthetic Fibers, Subparts C, D, and I.
A permit renewal application was received by the Division on February 27, 2018.
The wastewater treatment plant consists of a head works including screening and grit chamber, an
equalization basin with aeration and pH adjustment, an equalization/ mixing basin, an equalization/pre-
aeration basin, an emergency equalization tank, two activated sludge treatment trains in parallel including
aeration tanks/basins and secondary clarifiers, three polishing ponds, tertiary filtration, aerated basin for
sludge digestion, and sludge holding pond. One activated sludge train and one clarifier were taken out of
service due to reduction in process flows.
2. Receiving Waterbody Information
Receiving Waterbody Information
Outfalls/Receiving Stream(s):
Outfall 001 — Buffalo Creek
Stream Segment:
9-53-(5)
Stream Classification:
C
Drainage Area (mi2):
4852
Summer 7Q10 (cfs):
32
Winter 7Q10 (cfs):
48
30Q2 (cfs):
Average Flow (cfs):
201
IWC (% effluent):
2.13
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: 03-08-05
USGS Topo Quad:
G12 NE
3. Effluent Data Summary
Effluent data is summarized below for the last 5 years.
Table. Effluent Data Summary
Parameter
Units
Average
Max
Min
Permit
Limit
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Flow
MGD
0.335
0.449
0.45 MA
BOD
lb/Day
12.1
30.2
68.0 MA
181.0 DM
NH3N
mg/L
<0.1
N/A
TSS
lb/Day
31.6
71.3
124.0 MA
395.0 DM
pH
SU
8.4
7.7
6.0-9.0
Temperature
°C
30.6
13.6
N/A
DO
mg/L
-
-
_
N/A
TN
mg/L
1.0
1.4
N/A
TP
mg/L
0.07
0.08
N/A
Fecal Coliform
col/100 mL
13.2
85
200 MA
400 DM
MA -Monthly Average, WA -Weekly Average, DM -Daily Maximum
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/1 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: Instream Monitoring is not required by the permit.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (Y/N): N
Name of Monitoring Coalition: N/A
5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): The facility did not have any
limit violations during the last 5 years, please see attached.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed all the WET tests during the last 5 years, please see attached.
Summarize the results from the most recent compliance inspection: The latest compliance inspection
conducted on 12/10/2019 concluded that "The wastewater facility appeared to be properly operated and
well maintained".
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).
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If applicable, describe any other dilution factors considered (e.g., based on CORMIX model results):
N/A
If applicable, describe any mixing zones established in accordance with 1 SA 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/1 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: N/A.
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/1 (summer) and 1.8 mg/1 (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/1) and capped at 28 ug/1 (acute impacts). Due to analytical issues, all TRC values
reported below 50 ug/1 are considered compliant with their permit limit.
Describe any proposed changes to ammonia and/or TRC limits for this permit renewal: N/A.
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 Y2 detection limit for "less than" values; and 4) stream flows used for dilution
consideration based on 15A NCAC 2B.0206. Effective April6, 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: Bis(2-ethylhexyl) phthalate and Silver.
• 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: N/A.
• 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
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concentration: Aluminum, Arsenic, Beryllium, Cadmium, Total Phenolic Compounds, Total
Chromium, Copper, Cyanide, Fluoride, Lead, Mercury, Nickel, Selenium, Zinc,
Chlorodibromomethane, and Chloroform.
Attached are the RPA results and a copy of the guidance entitled "NPDES Implementation oflnstream
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 2.13% with quarterly frequency is established in the permit. The facility has been consistently passing
WET test during the last 5 years, please see attached.
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/1) 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/1) and/or if any individual value exceeds a TBEL
value of 47 ng/1.
Describe proposed permit actions based on mercury evaluation: The facility provided one Mercury value
with the renewal application. The RPA was conducted using this value, the predicted concentration is
more than 2 orders of magnitude below allowable concentration.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: N/A.
Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs: N/A
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.
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7. Technology -Based Effluent Limitations (TBELs)
Describe what this facility produces: This facility is subject to Effluent Guidelines in 40 CFR 414 —
Organic Chemicals, Plastics and Synthetic Fibers, Subparts C, D, and I.
List the federal effluent limitations guideline (ELG) for this facility: 40 CFR 414, Subparts C, D, and I..
If the ELG is based on production or flow, document how the average production/flow value was
calculated: This ELG is based on flow. The limits in the permit were calculated based on the 0.387 MGD
OCPSF flow. The flow did not change from the previous permit.
For ELG limits, document the calculations used to develop TBEL limits: Please see attached.
If any limits are based on best professional judgement (BPJ), describe development: N/A.
Document any TBELs that are more stringent than WQBELs: N/A.
Document any TBELs that are less stringent than previous permit: N/A.
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.
If applicable, describe the results of the antidegradation review, including the Engineering Alternatives
Analysis (EAA) and any water quality modeling results: N/A.
9. Antibacksliding Review
Sections 402(o)(2) and 303(d)(4) of the CWA and federal regulations at 40 CFR 122.44(1) 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.
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
Page 6 of 13

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.
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, 2025, 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
0.45 MGD
No change
15A NCAC 2B .0505
BODS
MA 68 lb/day
DM 181 lb/day
No change
TBEL. Based on the 40 CFR 414.
TSS
MA 124 lb/day
DM 395 lb/day
No change
TBEL. Based on the 40 CFR 414.
pH
6.0 — 9.0 SU
No change
WQBEL. State WQ standard, 15A
NCAC 2B .0200
Total Phosphorus
N/A
Semi -Annually
Effluent Monitoring
Only
State WQ Rule, 15A NCAC 2B
.0500
Total Nitrogen
N/A
Semi -Annually
Effluent Monitoring
Only
State WQ Rule, 15A NCAC 2B
.0500
Toxicity Test
Chronic limit, 2.13%
effluent
No change
WQBEL. No toxics in toxic
amounts. 15A NCAC 2B.0200 and
15A NCAC 2B.0500
Total Hardness
N/A
Quarterly Effluent
Monitoring Only
State WQ standard, 15A NCAC 2B
.0200
Total Silver
N/A
MA 2.81 µg/L
DM 11.48 µg/L
State WQ standard, 15A NCAC 2B
.0200
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Fecal Coliform
(Geometric Mean)
MA 200/100 mL
DM 400/100 mL
No change
State WQ standard, 15A NCAC 2B
.0200
OCPSF limits
40 CFR 414
See Section A. (2.)
See Section A. (2.)
TBEL. Based on the 40 CFR 414.
Electronic
Reporting
N/A
Required
In accordance with EPA Electronic
Reporting Rule 2015.
MGD — Million gallons per day, MA — Monthly Average, DM — Daily Max
13. Public Notice Schedule
Permit to Public Notice: 11/10/2020
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
• NPDES Implementation of Instream Dissolved Metals Standards — Freshwater Standards
• OCPSF Excel Calculator
• OCPSF BOD and TSS Calculator
• WET Test Summary
16. Changes in the Final Permit
The NC WRC asked the DWR to implement measures to eliminate phthalates from the effluent.
Review of the renewal application indicates that during four separate sampling events conducted by
the facility phthalates were not detected in the effluent.
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
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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/1
(Dissolved)
Chronic FW, µg/1
(Dissolved)
Acute SW, µg/1
(Dissolved)
Chronic SW, µg/1
(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/1 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/1
Cadmium, Acute
WER*{1.136672-[In hardness](0.041838)} • e^{0.9151 [In hardness] -
3.1485}
Cadmium, Acute Trout
waters
WER* {1.136672- [ln hardness](0.041838)} • e^{0.9151[ln hardness] -
3.62361
Cadmium, Chronic
WER*{1.101672-[In 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}
Copper, Chronic
WER*0.960 • e^{0.8545[ln hardness]-1.702}
Page 9 of 13

Lead, Acute
WER* {1.46203- [In hardness] (0.145712) } • e^ {1.273 [In hardness] -
1.460}
Lead, Chronic
WER* {1.46203- [In hardness] (0.145712) } • e^ {1.273 [In hardness] -
4.705 }
Nickel, Acute
WER*0.998 • e^{0.8460[in hardness]+2.255}
Nickel, Chronic
WER*0.997 • e^{0.8460[in 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
• Receiving stream classification
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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
Where:
1 + { [Kpo] [ss(1+a)] [10-6] }
ss = in -stream suspended solids concentration [mg/I], minimum of 10 mg/L used,
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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:ldilution
1Q10 (cfs)
14.16
RPA calculation
Permitted Flow (MGD)
1.58
Design flow of treatment system
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