NC0087947_Fact Sheet_20180316

Fact Sheet
NPDES Permit No. NCO087947
Permit Writer/Email Contact Bing Bai, [e-mail]:
Date: March 12, 2018
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 2°d 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:
Columbus County/Columbus County POTW
Applicant Address:
111 Washington Street, Whiteville, NC 28472
Facility Address:
1321 Old Road 87, Acme, North Carolina 28472
Permitted Flow:
0.05 MGD
Facility Type/Waste:
Industrial (100%) with modified pretreatment program
Facility Class:
Class 2
Pre
Pre -Equalization Tank; Carbon Addition System, SBR, Post -
Equalization Tank; Sand Filters; Activated Sludge Digester
Pretreatment Program (Y/N)
Yes
County:
Columbus
Region
Wilmington
Briefly describe the proposed permitting action and facility background: Columbus County has applied
for NPDES permit renewal, and submitted a renewal application dated June 8, 2016. This facility
receives wastewater solely from a CIU — Hexion Inc. which produces Hexamethylenetramine
(Hexamine). This CIU is subject to Pretreatment Standards for Existing Sources (PSES) and meeting all
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the required testing criteria list in PSES. This CIU is also subject to 40 CFR 414 Subpart H — Specialty
Organic Chemicals, However, these effluent guidelines specify BOD and TSS limits which are
significantly less stringent than those water -quality based limits which were included in the previous
permit and carried over into this proposed draft permit.
2. Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receiving Stream(s):
Outfall 001- Livingston Creek
Stream Segment:
18-64
Stream Classification:
C; Swamp
Drainage Area (mi2):
94.7
Summer 7Q10 (cfs)
0.6
Winter 7Q 10 (cfs):
7
30Q2 (cfs):
-
Average Flow (cfs):
85
IWC (% effluent):
12
303(d) listed/parameter:
No
Subject to TMDL/parameter:
No
Subbasin/HUC:
Cape Fear•, 03030005
USGS Topo Quad:
J26SW
3. Effluent Data Summary
Effluent data is summarized below for the period April 2012 through April 2017.
Table 3. Effluent Data Summary
Parameter
Units
Average
Max
Min
Permit Limit
Flow
MGD
0.014
0.029
0.001
0.05
BOD summer
mg/l
2.32
> 41.82
< 2
MA 5.0
WA 7.5
BOD winter
mg/l
2.17
> 42.91
< 2
WA 10.0
WA 15.0
Page 2 of 10

NH3N summer
mg/l
0.53
6.09
< 0.1
WA 2.0
WA 6.0
NH3N winter
mg/l
0.8
22.3
< 0.1
MA 4.0
WA 12.0
TSS
mg/l
2.46
44.7
< 1
MA 30.0
WA 45.0
pH
SU
8.19
8.91
6.1
6-9
Temperature
°C
20.3
32
4
Monitor only
DO
mg/l
9.16
16.34
6.04
> 6.0
Conductivity
umhos/cm
1,085.4
1,910
8.07
Monitor only
TN
mg/l
15.78
41
< 0.5
Monitor only
TP
mg/l
4.54
27.1
0
Monitor only
Fecal Coliform
#/100 ml
1.95
4,300
< 1
Not required
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: The receiving water is classified as C -Swamp water and the current permit requires
instream monitoring for dissolved oxygen, temperature and conductivity. Review of instream data from
January 2012 to April 2017 indicates that there were no significant differences between upstream and
downstream (ANOVA, p > 0.05). The average over the period analyzed indicated that upstream DO was
5.56 mg/L and downstream DO was 5.71 mg/L. During the critical summer months (April -October),
minimum values of 2.04 mg/L upstream and 1.84 mg/L downstream occurred with averages between 3.94
mg/L and 3.88 mg/L respectively. This draft permit maintains the same instream monitoring
requirements.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (Y/7V): NO
Name of Monitoring Coalition: NA
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5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): The facility reported 13 BOD
limit violations from 2013 to 2016, and 3 fecal coliform limit violations from 2013 to 2014.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed 17 of 19 quarterly chronic toxicity tests as well as all 4 second species
chronic toxicity tests.
Summarize the results from the most recent compliance inspection: The last facility inspection conducted
on August 12, 2016 reported that the facility was well maintained and operated in compliant.
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 2000 Cape Fear River Basin plan from Lock and Dam #1 to the Lower Cape Fear
River Estuary. No changes are proposed from the previous permit limits.
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/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/1) 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: Limitations for
NH3-N are based on 2000 Cape Fear River Basin plan from Lock and Dam #1 to the Lower Cape Fear
River Estuary. This facility does receive domestic wastewater so no TRC required. There are no proposed
changes.
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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/z detection limit for "less than" values; and 4) streamflows 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 collected between August 2012
and August 2016. 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: NA
• 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: NA
• 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: Total Copper, Total Lead.
• POTW Effluent Pollutant Scan Review: Three effluent pollutant scans were evaluated for
additional pollutants of concern.
o The following parameter(s) will receive a water quality -based effluent limit (WQBEL)
with monitoring, since as part of a limited data set, two samples exceeded the allowable
discharge concentration: NA
o The following parameter(s) will receive a monitor -only requirement, since as part of a
limited data set, one sample exceeded the allowable discharge concentration: NA
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.
Page 5 of 10

Describe proposed toxicity test requirement: This is a Minor POTW, and a chronic WET limit at 12%
effluent will continue on a quarterly frequency.
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/l
Table 4. Mercury Effluent Data Summary
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. This facility is < 1 MGD and no quantifiable levels of mercury (> 1 ng/1) was reported,
no mercury minimization plan (MMP) is needed.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: NA
Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs: NA
If applicable, describe any special actions (HQW or OR W) this receiving stream and classification shall
comply with in order to protect the designated waterbody: NA
If applicable, describe any compliance schedules proposed for this permit renewal in accordance with
15A NCAC 2H. 0107(c) (2) (B), 40CFR 122.4 7, and EPA May 2007 Memo: NA
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: NA
Page 6 of 10
2012
2013
2015
# of Samples
1
1
1
Annual Average Conc. n L
0.9
0.5
0.5
Maximum Conc., n /L
0.87
0.5
0.5
TBEL, n L
47
WQBEL, n L
104.9
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. This facility is < 1 MGD and no quantifiable levels of mercury (> 1 ng/1) was reported,
no mercury minimization plan (MMP) is needed.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: NA
Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs: NA
If applicable, describe any special actions (HQW or OR W) this receiving stream and classification shall
comply with in order to protect the designated waterbody: NA
If applicable, describe any compliance schedules proposed for this permit renewal in accordance with
15A NCAC 2H. 0107(c) (2) (B), 40CFR 122.4 7, and EPA May 2007 Memo: NA
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: NA
Page 6 of 10

7. Technology -Based Effluent Limitations (TBELs)
Municipals
Are concentration limits in the permit at least as stringent as secondary treatment requirements (30 mg1l
BODS/TSS for Monthly Average, and 45 mg/l for BODS/TSS for Weekly Average). YES
If NO, provide a justification for alternative limitations (e.g., waste stabilization pond). NA
Are 85% removal requirements for BODS/TSS included in the permit? YES
If NO, provide a justification (e.g., waste stabilization pond). NA
Industrials
Describe what this facility produces: Hexamethylenetramine (Hexamine).
List the federal effluent limitations guideline (ELG) for this facility: 40 CFR 414.Subpart H (Specialty
Organic Chemicals.
If the EL is based on production or flow, document how the average production/flow value was
calculated: This ELG is based on process wastewater pollutant concentrations listed in the following
table.
Table 5. TBEL Effluent Limits per 40 CFR 414 Subpart H (Specialty Organic Chemicals)
Effluent
characteristics
BPT limitations (mg/L)
Daily Maximum
Monthly Average
BODS
120
45
TSS
183
57
pH
6 — 9 s.u.
Both BODS and TSS specified in TBEL are less stringent than WQBEL, so limits are set based on
WQBEL (See comparison table below).
Table 6. Comparison of TBEL and WQBEL
Pollutant
TBEL (mg/L)
WQBEL
(mg/L)
Daily
Maximum
Monthly
Average
Daily
Maximum
Monthly
Average
BODS
120
45
-
5
TSS
183
57
-
30
pH
6 — 9 S.U.
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
Page 7 of 10

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(0)(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): NO
If YES, confirm that antibacksliding provisions are not violated: NA
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 213.0500; 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(0) 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.
Page 8 of 10

12. Summary of Proposed Permitting Actions:
Table 7. Current Permit Conditions and Proposed Changes
Parameter
Current Permit
Proposed Change
Basis for Condition/Change
Flow
MA 0.05 MGD
No change
15A NCAC 2B.0505
BODS
Summer:
No change
WQBEL. Based on protection of DO
MA 5 mg/l
standard. 15A NCAC 2B.0200
WA 7.5 mg/l
Winter:
MA 10 mg/l
WA 15 mg/l
NH3-N
Summer:
No change
WQBEL. Based on protection of
MA 2 mg/l
State WQ criteria. 15A NCAC
WA 6 mg/l
2B.0200
Winter:
MA 4 mg/1
WA 12 mg/l
TSS
MA 30 mg/l
No change
TBEL. Secondary treatment
WA 45 mg/l
standards/40 CFR 133 / 15A NCAC
2B .0406
DO
> 6 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
Total copper
Monitor quarterly
Remove copper
Reasonable Potential Analysis
effluent monitoring
based on no RP
Total lead
Monitor quarterly
Remove lead effluent
Reasonable Potential Analysis
monitoring based on
no RP
Conductivity
Monitor weekly
No change
WQBEL. State WQ standard, 15A
NCAC 2B.0200
Toxicity Test
Chronic limit, 12%
No change
WQBEL. No toxics in toxic
effluent
amounts. 15A NCAC 2B.0200 and
15A NCAC 2B.0500
2' Species
No requirement
Add requirement in
40 CFR 122
Toxicity Test
permit
Page 9 of 10

Fecal Coliform
No requirement
Add requirement for
NPDES Permit Renewal
permit renewal
Requirement as in 2A form
Total Hardness
No requirement
Add effluent and
Required to assess dissolved metal
upstream monitoring
limitations
based on the new 2016
dissolved metal
standards
Effluent Pollutant
Three times per permit
No change
40 CFR 122
Scan
cycle
Electronic
No requirement
Add Electronic
In accordance with EPA Electronic
Reporting
Reporting Special
Reporting Rule 2015.
Condition
MGD — Million gallons per day, MA - Monthly Average, WA — Weekly Average, DM — Daily Max
13. Public Notice Schedule:
Permit to Public Notice: 06/26/2017
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. Fact Sheet Addendum (if applicable):
Were there any changes made since the Draft Permit was public noticed (Yes/No): Yes
If Yes, list changes and their basis below:
1) The facility passed all four 2nd Species Toxicity Tests performed in August, September, October and
November 2017 as required by the permit renewal application. In addition, statement for multiple
species toxicity tests requirement was added to the cover letter per required by Part E. Toxicity
Testing Data in EPA Form 2A.
2) Statement in cover letter for fecal coliform was added per the permit renewal application requirement.
15. Fact Sheet Attachments (if applicable):
• RPA Spreadsheet Summary
• Dissolved Metals Implementation/Freshwater or Saltwater
• Instream DO Summary
• NH3-N and TRC WLA
• Mercury TMDL Evaluation
Page 10 of 10

Permit No. NCO087947
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 Q ality Standards/A uatic Life Protection
Parameter
Acute FW, gg/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
213.0200 (e.g., arsenic at 10 µg/1 for human health protection; cyanide at 5 gg/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, gg/I
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[In 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}
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}
Page 1 of 4

Permit No. NCO087947
Silver, Acute
WER*0.85 • e^{l.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/WOBELs 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, 7Q 10 (the spreadsheet automatically calculates
the 1 Q 10 using the formula I Q 10 = 0.843 (s7Q 10, cfs) 0.993
• Effluent hardness and upstream hardness, site-specific data is preferred
• Permitted flow
• 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.
Page 2 of 4

Permit No. NCO087947
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 + s7Q 10, 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 I + { [Kpo] [SS(i+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.
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 = (s7Q 10 + Qw) (Cwgs) — (s7Q 10) (Cb)
Qw
Where: Ca = allowable effluent concentration (gg/L or mg/L)
Cwqs = NC Water Quality Standard or federal criteria (gg/L or mg/L)
Cb = background concentration: assume zero for all toxicants except NH3* (gg/L or mg/L)
Qw = permitted effluent flow (cfs, match s7Q 10)
s7Q 10 = 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 s7Q 10 may be incorporated as applicable:
IQ 10 = used in the equation to protect aquatic life from acute toxicity
Page 3 of 4

Permit No. NC0087947
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.
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)
331.7
Average from three PPAs
[Total as, CaCO3 or (Ca+Mg)]
December 2012 — July 2015
Average Upstream Hardness (mg/L)
25
Default with no data
[Total as, CaCO3 or (Ca+Mg)]
7Q10 summer (cfs)
0.6
NPDES files, BIMS
1 Q 10 (cfs)
0.51
Calculated from 7Q 10 summer
Permitted Flow (MGD)
0.05
NPDES files, BIMS
Date:
Permit Writer:
Page 4 of 4

All data
Date
Upstream
Downstream
Units
Date
Upstream
)ownstrean Units
1/5/2012
7
mg/I
9/12/2016
3.88
3.83
mg/I
2/2/2012
7.5
mg/I
9/19/2016
3.81
3.9
mg/I
3/1/2012
7.8
mg/I
9/26/2016
5.71
5.51
mg/I
4/12/2012
4.1
mg/I
10/3/2016
3.77
4.31
mg/I
5/18/2012
3.3
mg/I
10/10/2016
3.53
4.01
mg/I
6/14/2012
3
mg/I
10/17/2016
5.01
4.92
mg/I
7/12/2012
2.6
mg/I
10/24/2016
2.09
1.84
mg/I
8/9/2012
2.6
mg/I
10/31/2016
3.78
3.59
mg/I
9/6/2012
3.4
mg/I
11/7/2016
4.09
4.16
mg/I
10/9/2012
4.7
mg/I
11/14/2016
7.07
8.14
mg/I
11/1/2012
4.7
mg/I
11/21/2016
9.10
8.06
mg/I
12/13/2012
8
mg/I
11/28/2016
9.11
8.09
mg/I
1/28/2013
11.5
mg/I
12/6/2016
7.06
7.07
mg/I
2/12/2013
11.2
mg/I
12/12/2016
8.77
9.9
mg/I
3/27/2013
9.9
mg/I
12/19/2016
9.16
9.43
mg/I
4/25/2013
6.6
mg/I
12/26/2016
8.07
8.51
mg/I
5/30/2013
5.4
mg/I
1/2/2017
8.28
10.69
mg/I
6/11/2013
3.9
mg/I
1/9/2017
12.04
12.51
mg/I
7/17/2013
3.5
mg/I
1/16/2017
8.91
9.16
mg/I
8/15/2013
3.5
mg/I
1/23/2017
6.80
6.47
mg/I
9/12/2013
4.3
mg/I
1/30/2017
9.27
9.41
mg/I
10/16/2013
3.4
mg/I
2/6/2017
8.22
8.39
mg/I
11/4/2013
6.5
mg/I
2/13/2017
8.15
8.04
mg/I
12/18/2013
9.5
mg/I
2/20/2017
8.25
8.14
mg/I
2/19/2014
10.6
mg/I
2/27/2017
4.93
5.26
mg/I
5/2/2016
5.91
5.45
mg/I
3/6/2017
6.72
6.62
mg/I
5/9/2016
4.43
4.19
mg/I
3/13/2017
8.34
8.03
mg/I
5/16/2016
4.86
4.48
mg/I
3/20/2017
8.72
8.48
mg/I
5/23/2016
4.61
4.75
mg/I
3/27/2017
6.09
6.03
mg/I
5/30/2016
3.87
3.26
mg/I
4/3/2017
4.63
4.45
mg/I
6/6/2016
3.34
3.03
mg/I
4/10/2017
6.46
6.97
mg/I
6/13/2016
4.08
3.67
mg/I
4/17/2017
4.24
4.17
mg/I
6/20/2016
3.85
3.35
mg/I
4/24/2017
4.59
4.33
mg/I
6/27/2016
2.41
2.22
mg/I
7/4/2016
2.04
2.11
mg/I
7/11/2016
2.32
2.12
mg/I
Min
2.04
1.84
7/18/2016
3.64
3.62
mg/I
Mean
5.56
5.71
7/25/2016
3.56
3.66
mg/I
8/1/2016
4.00
5.08
mg/I
8/8/2016
3.45
3.5
mg/I
8/15/2016
2.78
3.07
mg/I
8/22/2016
3.47
3.18
mg/I
8/29/2016
3.06
2.95
mg/I
9/5/2016
4.84
4.7
mg/I

Anova: Single Factor
SUMMARY
Groups Count Sum 4verageriance
Column 1 52 289.17 5.561 6
Column 2 77 439.31 5.705 7
ANOVA
irce of Variate SS df MS F P -value F crit
Between Gro 0.64687 1 0.647 0 0.75253123 3.915727
Within Grour 822.77817 127 6.479
Total 823.42504 128

Critical Summer
Date
Upstream
Downstream
Units
Date Upstream )ownstrean
4/12/2012
4.1
mg/I
4/17/2017 4.24 4.17
5/18/2012
3.3
mg/I
4/24/2017 4.59 4.33
6/14/2012
3
mg/I
7/12/2012
2.6
mg/I
Min 2.04 1.84
8/9/2012
2.6
mg/I
Mean 3.94 3.88
9/6/2012
3.4
mg/I
10/9/2012
4.7
mg/I
4/25/2013
6.6
mg/I
5/30/2013
5.4
mg/I
6/11/2013
3.9
mg/I
7/17/2013
3.5
mg/I
8/15/2013
3.5
mg/I
9/12/2013
4.3
mg/I
10/16/2013
3.4
mg/I
5/2/2016
5.91
5.45
mg/I
5/9/2016
4.43
4.19
mg/I
5/16/2016
4.86
4.48
mg/I
5/23/2016
4.61
4.75
mg/I
5/30/2016
3.87
3.26
mg/I
6/6/2016
3.34
3.03
mg/I
6/13/2016
4.08
3.67
mg/I
6/20/2016
3.85
3.35
mg/I
6/27/2016
2.41
2.22
mg/I
7/4/2016
2.04
2.11
mg/I
7/11/2016
2.32
2.12
mg/I
7/18/2016
3.64
3.62
mg/I
7/25/2016
3.56
3.66
mg/I
8/1/2016
4
5.08
mg/I
8/8/2016
3.45
3.5
mg/I
8/15/2016
2.78
3.07
mg/I
8/22/2016
3.47
3.18
mg/I
8/29/2016
3.06
2.95
mg/I
9/5/2016
4.84
4.7
mg/I
9/12/2016
3.88
3.83
mg/I
9/19/2016
3.81
3.9
mg/I
9/26/2016
5.71
5.51
mg/I
10/3/2016
3.77
4.31
mg/I
10/10/2016
3.53
4.01
mg/I
10/17/2016
5.01
4.92
mg/I
10/24/2016
2.09
1.84
mg/I
10/31/2016
3.78
3.59
mg/I
4/3/2017
4.63
4.45
mg/I
4/10/2017
6.46
6.97
mg/I
Units
mg/I
mg/I

Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators
MAXIMUM DATA POINTS = 58
REQUIRED DATA ENTRY
Table 1. Proiect Information
Facility Name
WWTP/WTP Class
NPDES Permit
Outfall
Flow, Qw (MGD)
Receiving Stream
HUC Number
Stream Class
Aquactic Life
❑CHECK IF HQW OR ORW WQS
150
FW
Columbus County POTW
2
NCO087947
001
0.050
Livingston Creek
03030005
C, Sw
❑Apply WS Hardness WQC
7Q10s (cfs)
7Q10w (cfs)
30Q2 (cfs)
QA (cfs)
1Q10s (cfs)
0.60
NC
7.00
FW
65
ug/L
85.00
Aquatic Life
0.51
1.1443
Effluent Hardness
--------------------------------
Upstream Hardness
---------------------------------
Combined Hardness Chronic
.--------- -_
Combined Hardness Acute
331.67 mg/L (Avg)
25 mg/L (Avg)
_
60.08 m /L
— — — — — — — — — —
I 65.45 m 9 /L
-------------
ug/L
Data Source(s)
❑CHECK TO APPLY MODEL
NC
230
Par01
Par02
Par03
Par04
Par05
Par06E
Par07
ParOB
Par09
Par10
Par11
Par12
Par13
Par14
Par15
Par16
Par17
Par18
Par19
Par20
Par21
Par22
Par23
Par24
Table 2. Parameters of Concern
Name WQS Type Chronic Modifier Acute PQL Units
Arsenic
Aquactic Life
C
150
FW
340
ug/L
Arsenic
Human Health
Water Supply
C
10
HH/WS
N/A
ug/L
Beryllium
Aquatic Life
NC
6.5
FW
65
ug/L
Cadmium
Aquatic Life
NC
1.1443
FW
7.5022
ug/L
Chlorides
Aquatic Life
NC
230
FW
Chlorinated Phenolic Compounds
Water Supply
NC
1
A
ug/L
Total Phenolic Compounds
Aquatic Life
NC
300
A
ug/L_
Chromium III
Aquatic Life
NC
241.4144
FW
1990.7933
ug/L
Chromium VI
Aquatic Life
NC
11
FW
16
pg/L
Chromium, Total
Aquatic Life
NC
N/A
FW
N/A
pg/L
Copper
Aquatic Life
NC
16.6704
FW
25.9337
ug/L
Cyanide
Aquatic Life
NC
5
FW
22
10 ug/L
Fluoride
Aquatic Life
NC
1,800
FW
ug/L
Lead
Aquatic Life
NC
7.8256
FW
220.7278
ug/L
Mercury
Aquatic Life
NC
12
FW
0.5 ng/L
Molybdenum
Human Health
NC
2000
HH
ug/L
Nickel
Aquatic Life
NC
78.1730
FW
756.7275
pg/L
Nickel
Water Supply
NC
25.0000
WS
N/A
pg/L
Selenium
Aquatic Life
NC
5
FW
56
ug/L
Silver
Aquatic Life
NC
0.06
FW
1.5518
ug/L
Zinc
Aquatic Life
NC
266.4001
FW
284.1325
ug/L
Bis(2-etylhexyl)phthalate
Human Health
C
0.37
HH
pg/L
NCO087947 RPA, input
6/22/2017

NCO087947 RPA, input
6/22/2017

Columbus County POTW -
NC0087947 Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators
MAXIMUM
Qw (MGD) = 0.05
1Q10S (cfs) = 0.51
7Q10S (cfs) = 0.60
7Q10W (cfs) = 7.00
30Q2 (cfs) = NO 30Q2 DATA
Avg. Stream Flow, QA (cfs) = 85.00
Receiving Stream: Livingston Creek HUC 03030005
DATA POINTS = 58
WWTP/WTP Class: 2
IWC% @ 1Q10S =
13.19148936
1WC% @ 7Q10S =
11.43911439
IWC% @ 7Q10W =
1.095019428
1WC% @ 30Q2 =
N/A
IW%C @ QA =
0.091093415
Stream Class: C, Sw
Outfall 001
Qw = 0.05 MGD
COMBINED HARDNESS (m¢/L)
Acute = 65.45 mg/L
Chronic = 60.08 mg/L
PARAMETER
TYPE
NC STANDARDS OR EPA CRITERIA
y
REASONABLE POTENTIAL RESULTS
RECOMMENDED ACTION
(1)Applied
C7
(L
�
z
Chronic Acute
n # Det. Max Pred Cw Allowable Cw
Standard
Acute (FW): 2,577.4
Arsenic
C
150 FW(7QlOs) 340
ug/L
3 1 15.0
Chronic (FW): 1,311.3
No RP, Predicted Max < 50% of Allowable Cw - No
Default C.V.
No value Allowable Cw
Monitoring required
Arsenic
C
10 HH/WS(Qavg)
ug/L
Note: n 5 9
_>
Chronic (HH): 10,977.7
Limited data set
No value > Allowable Cw
Acute: 492.74
Beryllium
NC
6.5 FW(7QIOs) 65
ug/L
3 0 NO DETECTS
_ _
Note: n:5 9
Chronic: 56.82
No RP, Predicted Max < 50% of Allowable Cw - No
Limited data set
Max MDL = 10
Monitoring required
Acute: 56.871
Cadmium
NC
1.1443 FW(7QIOs) 7.5022
ug/L
3 0 NO DETECTS
Note: n < 9
..............................................
Chronic: 10.003
No RP, Predicted Max < 50of Allowable Cw - No
Limited data set
Max MDL = 10
Monitoring required
Acute: NO WQS
Total Phenolic Compounds
NC
300 A(30Q2)
ug/L
3 1 141.0
1
Note: n 5 9 Default C.V.
Chronic: IWC?
Limited data set
Acute: 121.3
Chromium VI
NC
11 FW(7QIOs) 16
µg/L
0 0
N/A
_
-- Chronic: ----96.2--
-------------------------
Chromium, Total
NC
gg/L
3 0 NO DETECTS
a. No Monitoring required if all Total Chromium
Note: n < 9
samples are < the Chromium VI Allowable Cw
Limited data set
Max MDL = 10
Acute: 196.59
Copper
NC
16.6704 FW(7QlOs) 25.9337
ug/L
20 11
21.28
Chronic: 145.73
No RP, Predicted Max < 50% of Allowable Cw - No
No value > Allowable Cw
Monitoring required
Acute: 166.8
Cyanide
NC
5 FW(7QlOs) 22
10
ug/L
3 0 NO DETECTS
Note: n:5 9
Chronic: 43.7
No RP, Predicted Max < 50% of Allowable Cw - No
Limited data set
Max MDL = 10
Monitoring required
Acute: 1,673.259
Lead
NC
7.8256 FW(7QlOs) 220.7278
ug/L
20 0
NO DETECTS
----------------------------------------------
___________________Chronic: 68.411
Chronic:
No RP, Predicted Max < 50% of Allowable Cw - No
Max MDL = 15
Monitoring required
NCO087947 RPA, rpa
Page 1 of 2 6/22/2017

Columbus County POTW - Outfall 001
NCO087947 Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators Qw = 0.05 MGD
NCO087947 RPA, rpa
Page 2 of 2 6/22/2017
Acute: NO WQS
Molybdenum
NC
2000 HH(7Q10s)
u,/L
0 0
N/A
Chronic: 17,483.9
No RP, Predicted Max < 50% of Allowable Cw - No
Monitoring required
Acute (FW): 5,736.5
Nickel
NC
78.1730 FW(7Q10s) 756.7275
gg/L
3 1
15.0
Chronic (FW): 683.4
No RP, Predicted Max < 50% of Allowable Cw - No
Note: n:5 9
Default C.V.
No value Allowable Cw
Monitoring required
Nickel
NC
25.0000 WS(7Q10s)
gg/L
Limited data set
_>
Chronic (WS): 218.5
No value > Allowable Cw
Acute: 424.5
Selenium
NC
5 FW(7Q10s) 56
ug/L
3 1
15.0
Note: n < 9
Default C.V.
----------------------------------------------
____________________Note:
Chronic: 43.7
No RP, Predicted Max < 50% of Allowable Cw - No
Limited data sel
No value > Allowable Cw
Monitoring required
Acute: 11.763
Silver
NC
0.06 FW(7Q10s) 1.5518
ug/L
3 0 NO DETECTS
Note: n:5 9
Chronic: 0.525
All samples are less than detect. Permittee should
Limited data set
Max MDL = 10
lower reporting level to PQL=1.0
Acute: 2,153.9
Zinc
NC
266.4001 FW(7Q10s) 284.1325
ug/L
3 0 NO DETECTS
1
Note: n < 9
..............................................
Chronic: 2,328.9
No RP, Predicted Max < 50% of Allowable Cw - No
Limited data set
Max MDL = 10
Monitoring required
Acute: NO WQS
Bis(2-etylhexyl)phthalate
c
0.37 HH(Qavg)
gg/L
3 1 33.60000
_ _
Note: n:5 9 Default C.V.
Chronic: 406.17645
No RP, Predicted Max < 50% of Allowable Cw - No
Limited data set
No value > Allowable Cw
IMonitoring required
NCO087947 RPA, rpa
Page 2 of 2 6/22/2017

H1
REASONABLE POTENTIAL ANALYSIS
H2
Effluent Hardness
Use"PASTE SPECIAL
Date
Data BDL=1/2DL
Results
1
1210/12
125 125
Std Dev.
2
11/12/2013
520 520
Mean
3
7/28/2015
350 350
C.V. (default)
4
25 25 Std Dev.
331.6667
n
5
0.6000
3
10th Per value
6
4
n
Average Value
7
10th Per value
331.67 mg/L
Max. Value
8
520.00 mg/L
7
Max. Value
9
8
7/28/2015
< 10 5
10
1
4
10
11
n
11
5
12
12
25.00 mg/L
13
14
14
7
15
15
16
8
16
Max. Pred Cw
18
17
19
18
20
19
11
22
20
23
21
24
13
22
26
23
27
24
28
25
16
30
26
31
17
27
32
28
34
29
19
35
30
20
31
21
32
33
34
23
35
24
REASONABLE POTENTIAL ANALYSIS
FE
H2
Use"PASTE SPECIAL
Use"PASTE SPECIAL
"COPY"
Values"Maximum
Upstream Hardness
.Maximum data
points = 58
. Maximum data
Date Data BDL=1/2DL Results
198.1372
1
25 25 Std Dev.
331.6667
2
Mean
0.6000
3
C.V.
3
4
n
170.00 mg/L
5
10th Per value
331.67 mg/L
6
Average Value
520.00 mg/L
7
Max. Value
0.0000
8
7/28/2015
< 10 5
9
1
4
10
n
11
5
12
25.00 mg/L
13
14
25.00 mg/L
7
15
Max. Value
16
8
17
Max. Pred Cw
18
19
10
20
21
11
22
23
24
13
25
26
14
27
28
29
16
30
31
17
32
33
34
19
35
FE
Use "PASTE SPECIAL
Values" then "COPY"
. Maximum data
points = 58
4.0333
0.6000
3
3.00
5.0 ug/L
15.0 ug/L
NCO087947 RPA, data
6/22/2017
Pdr01 & Pdr02
Use"PASTE SPECIAL
Values" then "COPY"
Arsenic
. Maximum data
points = 58
Date
Data BDL=1/2DL
Results
N/A
1
12/11/2012
< 10 5
Std Dev.
25.0000
2
11/12/2013
2.1 2.1
Mean
0.0000
3
7/28/2015
< 10 5
C.V. (default)
1
4
n
25.00 mg/L
5
25.00 mg/L
6
Mult Factor =
25.00 mg/L
7
Max. Value
8
Max. Pred Cw
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Use "PASTE SPECIAL
Values" then "COPY"
. Maximum data
points = 58
4.0333
0.6000
3
3.00
5.0 ug/L
15.0 ug/L
NCO087947 RPA, data
6/22/2017

Par03
REASONABLE POTENTIAL ANALYSIS
Use"PAE SPECIAL Par04
ST
Use "PASTE SPECIAL Par07
Values then COPY Values" then "COPY"
Beryllium I Cadmium Total Phenolic Compounds
.Maximum data . Maximum data
NCO087947 RPA, data
2- 6/22/2017
points = 58
points = 58
Date
Data BDL=1/2DL Results
Date
Data BDL=1/2DL
Results
Date Data
BDL=1/2DL
Results
1
12/11/2012
< 10 5 Std Dev.
2.5981
1
12/11/2012
< 10 5
Std Dev.
2.5981
1
12/13/2012
47 47
Std Dev.
2
11/12/2013
< 1 0.5 Mean
3.5000
2
11/12/2013
< 1 0.5
Mean
3.5000
2
11/12/2013 <
5 2.5
Mean
3
7/28/2015
< 10 5 C.V. (default)
0.6000
3
7/28/2015
< 10 5
C.V. (default)
0.6000
3
7/28/2015 <
8 4
C.V. (default)
4
n
3
4
n
3
4
n
5
5
5
6
Mult Factor =
3.00
6
Mult Factor =
3.00
6
Mult Factor =
7
Max. Value
5.00 ug/L
7
Max. Value
5.000 ug/L
7
Max. Value
8
Max. Pred Cw O
DETECTS ug/L
8
Max. Pred Cw O
DETECTS ug/L
8
Max. Pred Cw
9
9
9
10
10
10
11
11
11
12
12
12
13
13
13
14
14
14
15
15
15
16
16
16
17
17
17
18
18
18
19
19
19
20
20
20
21
21
21
22
22
22
23
23
23
24
24
24
25
25
25
26
26
26
27
27
27
28
28
28
29
29
29
30
30
30
31
31
31
32
32
32
33
33
33
34
34
34
35
35
35
NCO087947 RPA, data
2- 6/22/2017

REASONABLE POTENTIAL ANALYSIS
Use"PASTE SPECIAL Par10 Use "PASTE SPECIAL Pall
Values"then"COPY" Chromium, Total Values" then "COPY" Copper
. Maximum data . Maximum data
points = 58 points = 58
17.8333
0.6000
3
3.00
47.0 ug/L
141.0 ug/L
Use "PASTE SPECIALPar12
Values" then "COPY"
. Maximum data
points = 58
r-
6.4800
0.5384
20
1.33
16.00 ug/L
21.28 ug/L
Cyanide
Date
Data BDL=1/2DL Results
BDL=1/2DL Results
1
12/11/2012
< 10 5 Std Dev.
2.3094
2
11/12/2013
< 2 1 Mean
3.6667
3
7/28/2015
< 10 5 C.V. (default)
0.6000
4
16
n
3
5
<
10
5 n
6
6/25/2013
Mult Factor =
3.00
7
6
Max. Value
5.0 Ng/L
8
4.7 Mult Factor =
Max. Pred Cw O
DETECTS Ng/L
9
8.9
8.9 Max. Value
8
10
9.6
9.6 Max. Pred Cw
11
2/24/2014
3.6
12
10
5/12/2014
17
13
9.6
11
8/3/2014
14
6.3
6.3
12
15
5.9
5.9
16
2/9/2015
<
10
17
14
5/18/2015
<
18
2.5
15
7/28/2015
19
10
5
16
20
<
10
5
21
11/16/2015
<
7
22
18
2/15/2016
<
23
2.5
19
5/16/2016
24
10
10
20
25
<
7
3.5
26
35
27
22
28
23
29
24
30
31
32
26
33
27
34
28
35
Use "PASTE SPECIALPar12
Values" then "COPY"
. Maximum data
points = 58
r-
6.4800
0.5384
20
1.33
16.00 ug/L
21.28 ug/L
Cyanide
Date
Data
BDL=1/2DL Results
1
8/27/2012
2
12
12 Std Dev.
2
11/20/2012
< 5 5
6
6 Mean
3
11/29/2012
16
16 C.V.
4
2/11/2013
<
10
5 n
5
6/25/2013
<
10
5
6
8/16/2013
4.7
4.7 Mult Factor =
7
11/4/2013
12
8.9
8.9 Max. Value
8
11/12/2013
9.6
9.6 Max. Pred Cw
9
2/24/2014
3.6
3.6
10
5/12/2014
17
9.6
9.6
11
8/3/2014
6.3
6.3
12
11/10/2014
5.9
5.9
13
2/9/2015
<
10
5
14
5/18/2015
<
5
2.5
15
7/28/2015
<
10
5
16
8/17/2015
<
10
5
17
11/16/2015
<
7
3.5
18
2/15/2016
<
5
2.5
19
5/16/2016
32
10
10
20
8/15/2016
<
7
3.5
21
35
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Use "PASTE SPECIALPar12
Values" then "COPY"
. Maximum data
points = 58
r-
6.4800
0.5384
20
1.33
16.00 ug/L
21.28 ug/L
Cyanide
NCO087947 RPA, data
3- 6/22/2017
Date
Data BDL=1/2DL
1
12/10/2012
< 5 5
2
11/12/2013
< 5 5
3
7/28/2015
< 5 5
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
NCO087947 RPA, data
3- 6/22/2017

REASONABLE POTENTIAL ANALYSIS
Par14 Par17 & Par18
Use"PASTESPECIAL Use"PASTE SPECIAL
Values" then "COPY., Lead Values" then "COPY" Nickel
. Maximum data . Maximum data
points = 58 points = 58
Results
Date
Std Dev.
0.0000
Mean
5.00
C.V.
0.0000
n
3
Mult Factor =
1.00
Max. Value
5.0 ug/L
Max. Pred Cw O DETECTS ug/L
4-
Use"PASTE Ya Ply
SPECIAL -Values"
then "COPY".
Maximum data
points = 58
4.6667
0.6000
3
3.00
5.0 Ng/L
15.0 Ng/L
Date
Data
1
BDL=1/2DL Results
10 5 Std Dev.
1
8/27/2012
<
10
5 Std Dev.
2.4284
2
11/29/2012
<
10
5 Mean
3.1500
3
12/11/2012
<
10
5 C.V.
0.7709
4
2/11/2013
<
10
5 n
20
5
6/25/2013
<
1
0.5
6
8/16/2013
<
1
0.5 Mult Factor =
1.47
7
11/4/2013
<
1
0.5 Max. Value
7.500 ug/L
8
11/12/2013
<
1
0.5 Max. Pred Cw O
DETECTS ug/L
9
2/24/2014
<
1
0.5
10
5/12/2014
<
1
0.5
11
8/3/2014
<
1
0.5
12
11/10/2014
<
1
0.5
13
2/9/2015
<
3
1.5
14
5/18/2015
<
15
7.5
15
7/28/2015
<
10
5
16
8/17/2015
<
10
5
17
11/16/2015
<
10
5
18
2/15/2016
<
10
5
19
5/16/2016
<
10
5
20
8/15/2016
<
10
5
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
4-
Use"PASTE Ya Ply
SPECIAL -Values"
then "COPY".
Maximum data
points = 58
4.6667
0.6000
3
3.00
5.0 Ng/L
15.0 Ng/L
Date Data
BDL=1/2DL Results
1
12/11/2012 <
10 5 Std Dev.
2
11/12/2013
4 4 Mean
3
7/8/2015 <
10 5 C.V. (default)
4
n
5
8
6
Mult Factor =
7
11
Max. Value
8
Max. Pred Cw
9
14
10
16
11
17
12
19
13
20
14
22
15
23
16
25
17
26
18
28
19
29
20
31
21
32
22
34
23
35
24
25
26
27
28
29
30
31
32
33
34
35
4-
Use"PASTE Ya Ply
SPECIAL -Values"
then "COPY".
Maximum data
points = 58
4.6667
0.6000
3
3.00
5.0 Ng/L
15.0 Ng/L
NCO087947 RPA, data
6/22/2017
Date Data
1
12/20/2012 < 5
2
11/12/2013 1.1
3
7/8/2015 < 10
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
NCO087947 RPA, data
6/22/2017

REASONABLE POTENTIAL ANALYSIS
Selenium
Use "PASTE SPECIAL
Values" then "COPY"
Par20
Silver
Use "PASTE SPECIAL
Values" then "COPY"
Par21
Zinc
Use "PASTE SPECIAL
Values" then "COPY"
Part;
. Maximum data
. Maximum data
. Maximum data
points = 58
points = 58
points = 58
BDL=1/2DL Results
Date
Data BDL=1/2DL Results
Date Data
BDL=1/2DL Results
2.5 Std Dev.
1.9757
1
12/11/2012
< 10 5 Std Dev.
2.5981
1
12/11/2012 <
10 5 Std Dev.
0.0000
1
1.1 Mean
2.8667
2
11/12/2013
< 1 0.5 Mean
3.5000
2
11/12/2013 <
10 5 Mean
5.0000
2
5 C.V. (default)
0.6000
3
7/8/2015
< 10 5 C.V. (default)
0.6000
3
7/28/2015 <
10 5 C.V.
0.0000
3
n
3
4
n
3
4
n
3
4
5
5
5
Mult Factor =
3.00
6
Mult Factor =
3.00
6
Mult Factor =
1.00
6
Max. Value
5.0 ug/L
7
Max. Value
5.000 ug/L
7
Max. Value
5.0 ug/L
7
Max. Pred Cw
15.0 ug/L
8
Max. Pred Cw
O DETECTS ug/L
8
Max. Pred Cw
O DETECTS ug/L
8
9
9
9
10
10
10
11
11
11
12
12
12
13
13
13
14
14
14
15
15
15
16
16
16
17
17
17
18
18
18
19
19
19
20
20
20
21
21
21
22
22
22
23
23
23
24
24
24
25
25
25
26
26
26
27
27
27
28
28
28
29
29
29
30
30
30
31
31
31
32
32
32
33
33
33
34
34
34
35
35
35
NCO087947 RPA, data
5- 6/22/2017

REASONABLE POTENTIAL ANALYSIS
Max. Fred Cw 33.600000 gg/L
NCO087947 RPA, data
6- 6/22/2017
Use"PASTE SPECIAL
Bis(2-etylhexyl) phthalate
Values" then "COPY"
. Maximum data
points = 58
Date
Data BDL=1/2DL
Results
12/11/2012
< 5 2.5
Std Dev.
4.4792
11/12/2013
< 10 5
Mean
6.2333
7/28/2015
11.2 11.2
C.V. (default)
0.6000
n
3
Mult Factor =
3.00
Max. Value
11.200000 gg/L
Max. Fred Cw 33.600000 gg/L
NCO087947 RPA, data
6- 6/22/2017

NH3/TRC WLA Calculations
Facility: Columbus County POTW
PermitNo. NC0087947
Prepared By: Bing Bai
Enter Design Flow (MGD): 0.05
Enter s7Q10 (cfs): 0.6
Enter w7Q10 cfs : 7
Total Residual Chlorine (TRC)
Daily Maximum Limit (ug/1)
Ammonia (Summer)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.6
s7Q10 (CFS)
0.6
DESIGN FLOW (MGD)
0.05
DESIGN FLOW (MGD)
0.05
DESIGN FLOW (CFS)
0.0775
DESIGN FLOW (CFS)
0.0775
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
11.44
IWC (%)
11.44
Allowable Conc. (ug/1)
149
Allowable Conc. (mg/1)
7.0
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
7
Monthly Average Limit:
200/100ml DESIGN FLOW (MGD)
0.05
(If DF >331; Monitor)
DESIGN FLOW (CFS)
0.0775
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
8.74 Upstream Bkgd (mg/1)
0.22
IWC (%)
1.10
Allowable Conc. (mg/1)
144.5
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/I, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

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MONITORING REPORT(MR) VIOLATIONS for:
Permit: NCO087947 MRs Between 1 - 2012 and 6 - 2017 Region: %
Facility Name: % Param Name % County: %
Major Minor: %
Report Date: 06/05/17
Violation Category% Program Category:
Subbasin:% 14 Violation Action: %
Page: 1 of 3
PERMIT: NCO087947 FACILITY: Columbus County -Columbus County WWTP COUNTY: Columbus REGION: Wilmington
Limit Violation
MONITORING OUTFALU VIOLATION UNIT OF CALCULATED %
REPORT PPI LOCATION PARAMETER DATE FREQUENCY MEASURE LIMIT VALUE Over VIOLATION TYPE VIOLATION ACTION
04-2013
001
Effluent
04-2013
001
Effluent
05-2013
001
Effluent
05-2013
001
Effluent
05-2013
001
Effluent
06-2013
001
Effluent
09-2013
001
Effluent
09-2013
001
Effluent
09-2013
001
Effluent
10-2013
001
Effluent
07-2014
001
Effluent
05-2016
001
Effluent
08-2016
001
Effluent
06-2013
001
Effluent
08-2013
001
Effluent
BOD, 5 -Day (20 Deg. C) -
04/06/13
Weekly
mg/I
7.5
15
100
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
04/30/13
Weekly
mg/I
5
5.4
8
Monthly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
05/18/13
Weekly
mg/I
7.5
8
6.7
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
05/25/13
Weekly
mg/I
7.5
23
206.7
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
05/31/13
Weekly
mg/I
5
11.25
125
Monthly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
06/01/13
Weekly
mg/I
7.5
8
6.7
Weekly Average
Proceed to NOV
Concentration
Exceeded
BOD, 5 -Day (20 Deg. C) -
09/07/13
Weekly
mg/I
7.5
41.82
457.6
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
09/28/13
Weekly
mg/I
7.5
9
20
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
09/30/13
Weekly
mg/I
5
13.2
164.1
Monthly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
10/05/13
Weekly
mg/I
7.5
11
46.7
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
07/05/14
Weekly
mg/I
7.5
20
166.7
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
05/14/16
Weekly
mg/I
7.5
17
126.7
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
BOD, 5 -Day (20 Deg. C) -
08/13/16
Weekly
mg/I
7.5
12
60
Weekly Average
Proceed to
Concentration
Exceeded
Enforcement Case
Coliform, Fecal MF, MFC
06/01/13
Weekly
#/100ml
400
4,300
975
Weekly Geometric Mean
Proceed to NOV
Broth, 44.5 C
Exceeded
Coliform, Fecal MF, MFC
08/10/13
Weekly
#/100ml
400
4,300
975
Weekly Geometric Mean
Proceed to NOV
Broth, 44.5 C
Exceeded

MONITORING REPORT(MR) VIOLATIONS for:
Permit: NCO087947I MRs Between 1 - 2012 and 6 - 2017 Region: %
Facility Name: % Param Name % County: %
Major Minor: %
Report Date: 06/05/17 Page: 2 of 3
V7MWiolation Category:% Program Category: %
Subbasin:% Violation Action: %
PERMIT: NCO087947
FACILITY: Columbus County -Columbus County WWTP
COUNTY: Columbus
REGION: Wilmington
Limit Violation
MONITORING
OUTFALL/
VIOLATION
UNIT OF
CALCULATED
%
REPORT
PPI
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
07-2014
001
Effluent
Coliform, Fecal MF, MFC
07/12/14
Weekly
#/100ml
400
450
12.5
Weekly Geometric Mean
Proceed to
Broth, 44.5 C
Exceeded
Enforcement Case
Monitoring Violation
MONITORING
OUTFALL/
VIOLATION
UNIT OF
CALCULATED
%
REPORT
PPI
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
12-2016
001
Effluent
Annual Pollutant Scan [126
12/31/16
Annually
yes=1 no=0
Frequency Violation
No Action, Invalid
parameters]
Permit
08-2013
001
Effluent
Coliform, Fecal MF, MFC
08/17/13
Weekly
#/100ml
Frequency Violation
Proceed to NOV
Broth, 44.5 C
10-2013
001
Effluent
Coliform, Fecal MF, MFC
10/12/13
Weekly
#/100ml
Frequency Violation
Proceed to
Broth, 44.5 C
Enforcement Case
06-2012
001
Effluent
Copper, Total (as Cu)
06/30/12
Quarterly
ug/I
Frequency Violation
No Action, Facility
Reporting Error
02-2012
001
Effluent
Flow, in conduit or thru
02/29/12
Continuous
mgd
Frequency Violation
No Action, Facility
treatment plant
Reporting Error
06-2012
001
Effluent
Lead, Total (as Pb)
06/30/12
Quarterly
ug/I
Frequency Violation
No Action, Facility
Reporting Error
02-2012
001
Effluent
Nitrogen, Ammonia Total (as
02/18/12
Weekly
mg/I
Frequency Violation
No Action, Facility
N) - Concentration
Reporting Error
Other Violation
MONITORING
OUTFALL/
VIOLATION
UNIT OF
CALCULATED
%
REPORT
PPI
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
11-2012
11/12/12
Aquatic toxicity permit
Proceed to NOV
limit violation
12-2012
12/03/12
Aquatic toxicity permit
Proceed to NOV
limit violation
11-2013
11/04/13
Aquatic toxicity permit
Proceed to NOV
limit violation
12-2013
12/09/13
Aquatic toxicity permit
Proceed to NOV
limit violation

MONITORING REPORT(MR) VIOLATIONS for:
Permit: NCO087947I MRs Between 1 - 2012 and 6 - 2017 Region: %
Facility Name: % Param Name % County: %
Major Minor: %
Report Date: 06/05/17 Page: 3 of 3
V7MWiolation Category:% Program Category: %
Subbasin:% Violation Action: %
PERMIT: NCO087947
FACILITY: Columbus County -Columbus County WWTP
COUNTY: Columbus
REGION: Wilmington
Other Violation
MONITORING OUTFALL/
VIOLATION
UNIT OF
CALCULATED
%
REPORT PPI
LOCATION PARAMETER DATE FREQUENCY
MEASURE
LIMIT VALUE
Over
VIOLATION TYPE VIOLATION ACTION
01-2014
01/20/14
Aquatic toxicity permit Proceed to
limit violation Enforcement Case
Reporting Violation
MONITORING OUTFALL/
VIOLATION
UNIT OF
CALCULATED
%
REPORT PPI
LOCATION PARAMETER DATE FREQUENCY
MEASURE
LIMIT VALUE
Over
VIOLATION TYPE VIOLATION ACTION
12-2016
01/31/17
Late/Missing DMR None

6/22/17 WQS = 12 ng/L
Facility Name Columbus County POTW/NC0087947
/Permit No. :
Total Mercury 1631E PQL = 0.5 ng/L
Date
Modifier Data Entry
Value
12/10/12
0.866
0.866
11/19/13
< 0.5
0.5
8/5/15
< 0.5
0.5
MERCURY WQBEL/TBEL EVALUATION V:2013-6
No Limit Required
No MMP Required
7Q10s = 0.600 cfs WQBEL = 104.90 ng/L
Permitted Flow = 0.050 47 ng/L
0.9 ng/L - Annual Average for 2012
0.5 ng/L - Annual Average for 2013
0.5 ng/L - Annual Average for 2015

Removal Rate Calculations
Removal -rate Calculation
Removal Rates
Page 1 of 1 pages
6/13/2017, 8:27 AM
Revision: August 1999
AMMONIA
<
Influent
mg/L
Used in
Calculation <
Effluent
mg/L
Used in
Calculation
Influent
< mg/L
Used in
Calculation <
Effluent
mg/L
Used in
Calculation
Sample Date
Mar -17
Spreadsheet
1782.5
1782.5
1.5
1.5
< 2.6
1.3 <
2.6
1.3
Instructions:
1) Data
Heavyd only in
Bordered cells.
Rest of
worksheet is
1567.5
1182.4
1577.5
1450.6
1567.5 <
1182.4 <
1577.5 <
1450.6 <
2.0
2.0
2.0
3.0
1
1
1
1.5
< 2.6
< 2.6
< 2.6
< 2.6
1.3 <
1.3
1.3 <
1.3
2.6
4.3
2.60
2.86
1.3
4.28
1.3
2.86
Feb -17
Jan -17
Dec -16
Nov -16
protected, password is
T.
2) For below
2584.0
1358.0
1246.0
2584.0
1358.0 <
1246.0
0.6
2.0
1.7
0.6
1.0
1.7
< 2.6
5.3
2.9
1.3
5.3 <
2.9 <
2.10
2.50
2.50
2.1
1.25
1.25
Oct -16
Sep -16
Aug -16
detection data,
Jul -16
enter "<" in "<"
column, and
enter detection
level in Influent
or Effluent
mg/I columns.
1493.0
1293.0
1740.0
1422.0
1493.0 <
1293.0
1740.0
1422.0 <
2.0
1.5
3.2
2.0
1.0
1.5
3.2
1.0
< 2.7
< 2.7
3.3
< 2.7
1.4 <
1.4 <
3.3
1.4
2.60
2.60
3.00
5.60
1.3
1.3
3
5.6
Jun -16
May -16
Apr -16
Spreadsheet
will auto-
a
1258.0
1488.0
1258.0
1488.0 <
1.8
2.0
1.8
1.0
< 2.7
< 2.7
1.4
1.4
3.00
1.30
3
1.3
Mar -16
Feb -16
c
calcculateulate
averages and
removal rates
using 1/2
1793.0
1640.0
1793.0 <
1640.0
2.0
1.8
1.0
1.8
< 2.8
< 2.8
1.4
1.4 <
1.80
2.70
1.8
1.35
Jan-16
Dec -15
value entered.
3) Document
removal Rate
choice
4) Formulas in
Compre- hensive Guide
HwAcnapter,
Section E,
1463.0
1825.0
1740.0
1382.0
1294.0
1463.0 <
1825.0
1740.0 <
1382.0 <1
1294.0 <1
1551.405
2.0
2.3
2.0
2.0
2.0
1.0
2.3
1.0
1.0
1.0
1.33
< 2.7
3.6
< 2.8
< 2.8
3.3
1.4 <
3.6 <
1.4 <
1.4 <
3.3 1<1
1.90
2.70
2.70
2.70
2.70
2.70
1.35
1.35
1.35
1.35
1.35
1.95
Nov -15
Oct -15
Sep -15
Aug -15
Jul -15
Column Avera g es =>
page 1.
Unpaired Site Specific
RR =>
99.91 %
Unpaired Site Specific
RR
NC0087947
Literature/Default
RR =>
85.00 %
Literature/Default
RR =>
85.00
Columbus County POTW
31 % of data is BDL
69 % of data is BDL
6/13/2017
Removal -rate Calculation
Removal Rates
Page 1 of 1 pages
6/13/2017, 8:27 AM
Revision: August 1999
AMMONIA

NPDES/Aquifer Protection Permitting
Unit Pretreatment Information Request Form
PERMIT WRITER COMPLETES THIS PART:
Check all that apply
PERMIT WRITERS - AFTER you pet this form back
from PERCS:
Notifyy PERCS if LTMP/STMP data we said should be
on DMRs is not really there, so we can get it for you
(or NOV POTW).
- Notify PERCS if you want us to keep a specific POC
in LTMP/STMP so you will have data for next permit
renewal.
- Email PERCS draft permit, fact sheet, RPA.
- Send PERCS paper copy of permit (w/o NPDES
boilerplate), cover letter, final fact sheet. Email RPA if
changes.
n/a 0
Date of Request 6/8/2017 municipal renewal X
2017
Requestor Bing Bai new industries
Facility Name Columbus County POTW WWTP expansion
Permit Number NCO087947 Speculative limits
Region Wilmington stream reclass.
Basin Cape Fear outfall relocation
7Q10 change I
otherl
other
check applicable PERCS staff:
10ther Comments to
PERCS:
RRn (:PF (:TR FRR TAR - Sarah Racc (Rn7-R31 n1
CHO, HW, LTN, LUM, NES, NEW, ROA, YAD
Monit Hassan (807-6314)
Facility is permited for 0.05 MGD, with Hexion Inc. as the
sole user. The facility does not receive or treat any domestic
wastewater, and is running a pretreatment program.
PERCS PRETREATMENT STAFF COMPLETES THIS PART:
Status of Pretreatment Program (check all that apply)
1) facility has no SIU's, does have Division approved Pretreatment Program that is INACTIVE
2) facility has no SIU's, does not have Division approved Pretreatment Program
X 3) facility has SIUs and DWQ approved Pretreatment Program (list "DEV" if program still under development)
3a) Full Program with LTMP
X 3b) Modified Program with STMP
4) additional conditions regarding Pretreatment attached or listed below
Flow, MGD
Industrial
Uncontrollable
a
a Parameter of
Concern (POC)
L)
y Check List
a
BOD
TSS
NH3
Arsenic
Cadmium
Chromium
Lead
Molybden
Nickel
Silver
Selenium
Zinc
Total Nitn
Phosphor
Permitted Actual ITime period for Actual
I
I STMP time frame:
0.029 0.013 1/1/2016 - 12/31/2016
Most recent:
2012
n/a 0
Next Cycle:
2017
POC due to Required
NPDES/ Non- Required by
503
Disch Permit EPA* Sludge—
dge**
Limit
POC due
to SIU***
POTW POC STMP
(Explain Effluent
below)**** Freq
LTMP
Effluent
Freq
4 = quarterly sampling
one year before HWA is
due
X
4
N/A
X
4
X
4
X
4
X
4
4
X
4
X
4
Is all data on DMRs?
X
4
YES
X
4
NO (attach data)
X
4
X
4
4
X
4
X
4
Is data in spreadsheet
YES email to writer
NO
*Always in the LTMP/STMP ** Only in LTMP/STMP if sludge land app or composte (dif POCs for incinerators)
*** Only in LTMP/STMP while SIU still discharges to POTW **** Only in LTMP/STMP when pollutant is still of concern to POTW
:omments to Permit Writer (ex., explanation of any POCs; info you have on IU related investigations into NPDES problems):
emoval rate data from 2012 attached. Sampling for next HWA should have begun 2017 and should be recorded on DMRs. SIU flow from
)retreatment annual report. All flow into POTW is from SIU; no uncontrollable.
Columbus County NCO087947
Revised: July 24, 2007