NC0003298_Fact Sheet_20190924

Fact Sheet
NPDES Permit No. NC0003298
Permit Writer/Email Contact Sergei Chemikov, Ph.D./[e-mail]:
Date: December 5, 2017
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 2" 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:
International Paper — Riegelwood Facility
Applicant Address:
865 John L. Riegel Road, Riegelwood, NC 28456
Facility Address:
865 John L. Riegel Road, Riegelwood, NC 28456
Permitted Flow:
50.0 MGD
Facility Type/Waste:
MAJOR Industrial; 99.8% industrial, 0.2% domestic
Facility Class:
Class 4
Treatment Units:
dual bar screens and primary clarifiers, nutrient addition facilities, 173
acres of aerated lagoons with re -circulation, sludge holding lagoons,
sludge dewatering presses, oxygen injection facilities, now
measurement and recording equipment
Pretreatment Program (Y/N)
N/A
County:
Columbus
Region
Wilmington
Briefly describe the proposed permitting action and facility background: The International Paper (IP)
Company - Riegelwood Facility is located near Wilmington. IP takes the raw material (logs/chips) and
produces fluff pulp (bleached product). Facility operates three bleach plants, all of them have been
converted to process softwood (pine primarily). Facility operates one external outfall (Outfall 001) and two
internal outfalls (Outfall 004 and Outfall 005). The internal outfalls were established to implement Cluster
Rules.
This modification is being conducted to reflect the current production level at the facility. When the permit
was renewed, the facility was undergoing a major upgrade and the product output was uncharacteristically
low. Currently, the production level has risen and the TBELs must be re -calculated to reflect it.
Page 1 of 14

Outfall 001
This outfall contains wastewater associated with the all industrial operations, landfill leachate, and sanitary
sewer wastewater.
Outfall 001, the Internal Outfall 004 (combines effluent from Bleach Plant 1 and Bleach Plant 2) and
Internal Outfall 005 (effluent from Bleach Plant 3) are subject to the Cluster Rules - the modifications
expressed by 40 CFR 430, Subpart B (430.20) — Bleached Papergrade Kraft and Soda (promulgated
April 15, 1998). In accordance with the Cluster Rules each Bleach Plant should be monitored for
numerous parameters. However, due to the configuration of deep sewer lines the permittee was unable to
access effluent from Bleach Plant 1 and Bleach Plant 2 separately. EPA has granted a request from the
permittee to establish one sampling point for both plants. However, acid waste and alkaline waste will be
sampled separately. Bleach Plant 3 has a separate sampling point.
The current oxygen consuming waste limits (BODS) are water quality limited. The dioxin limit (0.9 pg/L)
is also a water quality based limit. These limits will remain in the permit.
In 1992, the facility requested a variance from the Environmental Management Commission to redefine the
summer period. The Environmental Management Commission granted a variance request, the summer for
this facility is defined as June 1 — October 31. International Paper has requested the continuation of the
variance with this renewal.
2. Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receivin Stream(s):
Outfall 001- Cape Fear River
Stream Segment:
030617/18-(63a)
Stream Classification:
C-Sw
Drainage Area (mi2):
5,301
Summer 7Q10 (cfs)
856
Winter 7Q10 (cfs):
1101
30Q2 (cfs):
Average Flow (cfs):
5330
IWC (% effluent):
8.3
303(d) listed/parameter:
Yes- this segment is listed as impaired for biological integrity.
Subject to TMDL/parameter:
No
Subbasin/HUC:
Cape Fear River; 030617
USGS To o Quad:
J26SW
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
Flow
MGD
26.5
54.6
50.0 MA
BOD summer
Lb/Day
4,214
12,262
5,000 MA
BOD winter
10,000 MA
NH3N
mg/L
2.39
6.5
N/A
TSS
Lb/Day
3,757
14,547
41,628 MA
pH
SU
8.0
7.1
6.0-9.0
Temperature
°C
32
N/A
DO
mg/L
7.1
11.3
5.1
>5.0 mg/L
TN
mg/L
5.5
14.1
N/A
Page 2 of 14

TP mg/L I I 8.8 I N/A
Fecal Coliform col/100 mL <10 N/A
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/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: The current permit requires instream monitoring for dissolved oxygen and salinity.
Stream sampling is conducted 3/week during June — September and 1/week during the remainder of the
year. As a participant in the Lower Cape Fear Monitoring Coalition, the instream monitoring is not
required. Should the membership in the Coalition be terminated, the facility must notify Division
immediately and begin instream monitoring as specified in this permit.
Due to the significant number of dischargers in that segment of Cape Fear River it is difficult to separate
influence of IP discharge on water quality in the receiving stream.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (YIN): Y
Name of Monitoring Coalition: Lower Cape Fear Monitoring Coalition
5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): The facility reported no limit
violations.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed 19 of 19 quarterly chronic toxicity tests.
Summarize the results from the most recent compliance inspection: The last facility inspection conducted
in 2016 recommended re -issuance of the permit.
6. Water Quality -Based Effluent Limitations (WQBELs)
Dilution and Mixing Zones
In accordance with 15A NCAC 2B.0206, the following streamflows are used for dilution considerations
for development of WQBELs: 1 Q 10 streamflow (acute Aquatic Life); 7Q 10 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): NA
If applicable, describe any mixing zones established in accordance with 15A NCAC 2B.0204(b): NA
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: Limitations for
BOD are based on a model for instream DO protection. No changes are proposed from the previous
permit limits.
Page 3 of 14

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/L) and capped at 28 ug/1(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: 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/2 detection limit for "less than" values; and 4) streamflows used for dilution
consideration based on 15A NCAC 213.0206. 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 collected between during the last
5 years. 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: Dioxin, based on a historic limit.
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
concentration: As, Be, Cd, Total Phenolic Compounds, Cr, Cu, CN, F, Pb, Mo, Ni, Se, Ag, Zn,
Chlorophorm, 2,4,6 — Trichlorophenol, Pentachlorophenol.
If applicable, attach a spreadsheet of the RPA results as well as a copy of the Dissolved Metals
Implementation Fact Sheet for freshwater/saltwater to this Fact Sheet. Include a printout of the RPA
Dissolved to Total Metal Calculator sheet if this is a Municipality with a Pretreatment Program.
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 8% effluent will continue on a quarterly frequency.
Page 4 of 14

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/L) and/or if any individual value exceeds a TBEL
value of 47 ng/L
Table. Mercury Effluent Data Summary
2012
2013
# of Samples
6
11
Annual Average Conc., ng/L
4.08
7.15
Maximum Conc., ng/L
6.8
13.8
TBEL, ng/L
47
WQBEL, ng/L
14.5
Describe proposed permit actions based on mercury evaluation: Since no annual average mercury
concentration exceeded the WQBEL, and no individual mercury sample exceeded the TBEL, no mercury
limit is required.
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: NA
If applicable, describe any special actions (HQW or ORW) this receiving stream and classification shall
comply with in order to protect the designated waterbody: N/A.
If applicable, describe any compliance schedules proposed for this permit renewal in accordance with
1 SA NCAC 2H. 0107(c) (2) (B), 40CFR 122.47, and EPA May 2007 Memo: N/A.
If applicable, describe any water quality standards variances proposed in accordance with NCGS 143-
215.3(e) and 1 SA NCAC 2B.0226 for this permit renewal: NA
7. Technology -Based Effluent Limitations (TBELs)
Industrials (if not applicable, delete and skip to next Section)
Describe what this facility produces: fluff pulp (bleached product)
List the federal effluent limitations guideline (ELG) for this facility: 40 CFR 430 Subpart B (430.20)
Bleached Papergrade Kraft and Soda.
If the ELG is based on production or flow, document how the average production/flow value was
calculated: This ELG is based on production. The annual average production (lbs/day) for the past 1 year
(since the facility coverted to fluff pulp only) was reported as 3,507,000 lb/day.
Attached please find the limit calculations.
If any limits are based on best professional judgement (BPJ), describe development: NA
Document any TBELs that are more stringent than WQBELs: NA
Document any TBELs that are less stringent than previous permit: NA
Page 5 of 14

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: NA
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): YES
If YES, confirm that antibacksliding provisions are not violated: The TBELs for some parameters have
been raised, but they are within the range that the facility had previously and antibacksliding provision are
not being violated. All the water quality standards in the receiving stream will be met.
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.
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:
Table. Current Permit Conditions and Proposed Changes
Parameter
Current Permit
Proposed Change
Basis for Condition/Change
Flow
MA 50.0 MGD
No change
15A NCAC 2B .0505
BOD5
Summer:
No change
WQBEL. Based on protection of DO
MA 5,000 lb/day
standard. 15A NCAC 2B.0200
DM 10,000 lb/day
Winter:
MA 10,000lb/day
DM 20,000 lb/day
Page 6 of 14

NH3-N
Monitor only
No change
WQBEL. Based on protection of
State WQ criteria. 15A NCAC
2B.0200
TSS
MA 41,628.8 lb/day
MA 49,618.3 lb/day
TBEL, changed due to the icreases
DM 77,785.6 lb/day
DM 92,356.7 lb/day
in production. 40 CFR 430 Subpart
B.
Temperature
Monitor only
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
DO
> 5 mg/L
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
pH
6 — 9 SU
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
Total Nitrogen
Monitor Only
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
Total Phosphorus
Monitor Only
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
Dioxin
DM 0.9 pg/L
No change
Based on water quality criteria.
Toxicity Test
Chronic limit, 8%
No change
WQBEL. No toxics in toxic
effluent
amounts. 15A NCAC 2B.0200 and
15A NCAC 2B.0500
AOX
MA 2,179.4 lb/day
MA 2,597.7 lb/day
TBEL, changed due to the increases
in production. 40 CFR 430 Subpart
DM 3,326.8 lb/day
DM 3,965.2 lb/day
B.
Trichlorophenol
DM 30.8 lb/day
DM 36.6 lb/day
TBEL, changed due to the decreases
in production. 40 CFR 430 Subpart
B.
Pentachlorophenol
DM 4.89 lb/day
DM 5.84 lb/day
TBEL, changed due to the decreases
in production. 40 CFR 430 Subpart
B.
Total Hardness
Monitor effluent and
No change
WQBEL. State WQ standard, 15A
upstream
NCAC 2B.0200
Chloroform
MA 8.62 lb/day
MA 8.93 lb/day
TBEL, changed due to the increases
in production. 40 CFR 430 Subpart
Internal Outfall
DM 14.41b/day
DM 14.91b/day
B
004
Chloroform
MA 5.84 lb/day
MA 8.33 lb/day
TBEL, changed due to the increases
in production. 40 CFR 430 Subpart
Internal Outfall
DM 9.81 lb/day
DM 13.91b/day
B
005
Page 7 of 14

Electronic
Electronic Reporting
No change
In accordance with EPA Electronic
Reporting
Special Condition
Reporting Rule 2015.
MGD — Million gallons per day, MA - Monthly Average, WA — Weekly Average, DM — Daily Max
13. Fact Sheet Addendum (if applicable):
Were there any changes made since the Draft Permit was public noticed (Yes/No): NO
If Yes, list changes and their basis below: NA
14. Fact Sheet Attachments (if applicable):
• RPA Spreadsheet Summary
• Effluent limit calculation
15. 316(b) Status
During the years 2012 through 2014 the average water withdrawal by the facility was 34.2 MGD.
Approximately 13% of the total intake was used for cooling purposes. Therefore, the facility is not subject
to 316(b) rule.
Page 8 of 14

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 I11
Calculation
Calculation
---
---
Chromium VI
16
11
1100
50
Copper
Calculation
Calculation
4.8
3.1
Lead
I 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/1
Cadmium, Acute
WER*{1.136672-[ln hardness](0.041838)} e^10.9151 [In hardness]-
3.1485}
Cadmium, Acute Trout
WER*{1.136672-[ln hardness](0.041838)} e^{0.9151[ln hardness] -
waters
3.62361
Page 9 of 14

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]-1.7001
Copper, Chronic
WER*0.960 e^{0.8545[ln hardness]-1.7021
Lead, Acute
WER* { 1.46203- [ln hardness] (0.145712)1 • e^ { 1.273 [ln hardness] -
1.460 }
Lead, Chronic
WER* { 1.46203- [/n hardness] (0.145712)1 • 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[In 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.
Page 10 of 14

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 "
• Effluent hardness and upstream hardness, site -specific data is preferred
• Permitted flow
• Receiving stream classification
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/4 + (s7Q10, cfs *Avg. Upstream Hardness, mg/L�
(Permitted Flow, cfs + s7Q10, cfs)
Page 11 of 14

The Combined Hardness for acute is the same but the calculation uses the 1Q10 flow.
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
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("'] [10-G] l
Where:
ss = in -stream suspended solids concentration [mg/1], 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.
translators, if any have been developed using federally approved methodology.
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.
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) (Cwas) — (s7Q10) (Cb)
Qv'
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)
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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
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 , e�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 otal allowable concentration) is included in the permit in accordance with the U.S.
EPA Technical SuI212ort Document for Water Quality -Based Toxics Control published in
1991.
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.
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)
25.0
Default value
[Total as, CaCO3 or (Ca+M ]
Average Upstream Hardness
(mg/L)
25.0
Default value
[Total as, CaCO3 or Ca+M )]
7Q10 summer (cfs)
0
Lake or Tidal
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1Q10 cfs
0
Lake or Tidal
Permitted Flow (MGD)
2.1
For dewaterin
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