NC0055786_Fact Sheet_20201217

Fact Sheet
NPDES Permit No. NCOO55786
Permit Writer/Email Contact Nick Coco, [e-mail]:
Date: July 30, 2020
Division/Branch: NC Division of Water Resources/NPDES Complex Permitting
Fact Sheet Template: Version 09Jan2017
Permitting Action:
❑X Renewal
❑ Renewal with Expansion
❑ New Discharge
❑ Modification (Fact Sheet should be tailored to mod request)
Note: A complete application should include the following:
• For New Dischargers, EPA Form 2A or 2D requirements, Engineering Alternatives Analysis, Fee
• For Existing Dischargers (POTW), EPA Form 2A, 3 effluent pollutant scans, 4 2nd species WET
tests.
• For Existing Dischargers (Non-POTW), EPA Form 2C with correct analytical requirements based
on industry category.
Complete applicable sections below. If not applicable, enter NA.
1. Basic Facility Information
Facility Information
Applicant/Facility Name:
City of Lexington/Lexington Regional Wastewater Treatment Plant
(WWTP)
Applicant Address:
28 West Center Street, Lexington, NC 27292
Facility Address:
500 Glendale Road, Lexington, NC 27292
Permitted Flow:
6.5 MGD
Facility Type/Waste:
MAJOR Municipal; 98.3% domestic, 1.7% industrial*
Facility Class:
Grade IV Biological Water Pollution Control System
Treatment Units:
Two influent pump stations, influent flow measurement and recording,
a fine bar screen, grit separator, two primary clarifiers (not in use),
biological nutrient removal (BNR) system, two final clarifiers, two
polishing ponds, chlorine contact chamber, post aeration, anaerobic
digesters, diffused air flotation (DAF) unit
Pretreatment Program (Y/N)
Y
County:
Davidson
Region
Winston-Salem
*Based on permitted flows
Briefly describe the proposed permitting action and facility background.- The City of Lexington has
applied for an NPDES permit renewal at 6.5 MGD for the Lexington Regional WWTP. This facility
serves a population of 30,000 residents, with 1 non -categorical significant industrial user (SIU) and 4
categorical industrial users (CIUs) and a pretreatment program. Treated wastewater is discharged into
Abbotts Creek, a class WS-V;B water in the Yadkin -Pee Dee River Basin. The facility has a primary
Outfall 001.
Page 1 of 11

Pretreatment: The latest Headworks Analysis was submitted on January 30, 2020 and approved on June
16, 2020. The latest Industrial Waste Survey was initially submitted on August 28, 2020, with a revised
version submitted on November 18, 2020 and approved on December 2, 2020.
2. Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receiving Stream(s):
Outfall 001 - Abbotts Creek
Stream Index:
12-118.5
Stream Classification:
WS-V, B
Drainage Area (m12):
182
Summer 7Q10 (cfs)
6.7
Winter 7Q10 (cfs):
15
30Q2 (cfs):
18
Average Flow (cfs):
167
IWC (% effluent):
60
303(d) listed/parameter:
Yes- Exceeding criteria for chlorophyll -a and PCB fish tissue
Subject to TMDL/parameter:
Yes- State wide Mercury TMDL implementation.
Subbasin/HUC:
03-07-07/03040103
USGS Topo Quad:
D18SW Lexington, NC
3. Effluent Data Summary
Effluent data for Outfall 001 is summarized below for the period of January 2016 through June 2020.
Table 1. Effluent Data Summary Outfall 001
Permit
Parameter
Units
Average
Max
Min
Limit
Flow
MGD
2.98
14.2
0.9
MA 6.5
WA 7.5
BOD summer
mg/1
3.1
16.53
L i4
MA 5.0
WA 15.0
BOD winter
mg/1
2.7
9.69
2
MA 10.0
WA 45.0
TSS
mg/1
3.7
72
(1z
MA 30.0
WA 2.0
NH3N summer
mg/1
0.65
10.02
0.1
MA 1.0
WA 6.0
NH3N winter
mg/1
0.46
4.2
0.1
MA 3.0
DO
mg/1
8.4
11.5
6.5
DA > 6 mg/1
(geometric)
(ge an)
Fecal coliform
4/100 ml
48029
1
WA 400
3.1
MA 200
Temperature
° C
19.3
30
7
Total Residual Chlorine
ug/1
17.8
94
2
DM 28
Conductivity
µmhos/cm
389
605.3
131.1
Page 2 of 11

pH
SU
7.2
10.12
6
6.0 < pH <
9.0
Total Zinc
ug/l
52.9
92
5
Total Copper
ug/l
11.3
34.7
2
Total Silver
ug/l
5.1
45
1
Bromodichloromethane
ug/l
5.9
15
5
TN
mg/l
5.5
10.25
0.1
TP summer
mg/l
0.73
3.91
0.12
TP Load summer
lb
3303
4780
1978
4910
TP winter
mg/l
0.77
3.3
0.04
TP Load winter
lb
2608
4239
1593
6930
MA -Monthly Average, WA -Weekly Average, DM -Daily Maximum, DA-Daily Average, QA-
Quarterly Average
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, temperature,
conductivity and fecal coliform upstream of the outfall at I-85 and downstream at Highway 47. The City
is a member of the Yadkin -Pee Dee River Basin Association (YPDRBA) and their instream requirements
are provisionally waived as long as they maintain membership. The YPDRBA has a monitoring station
Q5930000 just upstream of the facility. However, the nearest downstream monitoring station is 13.5 miles
downstream of the facility (YPDRBA station Q6120000) in the Yadkin River at the edge of High Rock
Lake. The downstream station is also downstream of other facilities and would not provide sufficient
insight into the impacts of the facility. As such, only upstream data from January 2015 through December
2019 were observed from YPDRBA monitoring station Q5930000. The data has been summarized in
Table 2 below.
Table 2. Instream Monitoring Coalition Data Summary
Parameter
Units
Q5930000 Upstream
Average
Max
Min
Conductivity
µmhos/cm
147
314
90
Fecal Coliform
#/100 ml
3g 5 mean)
6000
60
DO
mg/1
7.9
11.6
5.9
Temperature
° C
18.6
26.8
4.2
The draft permit maintains the same instream monitoring requirements as the current permit.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (YIN): Y
Name of Monitoring Coalition: Yadkin -Pee Dee River Basin Association (YPDRBA)
Page 3 of 11

5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): In 2017, the facility reported
3 ammonia limit violations and 4 TRC limit violations. The facility reported 1 fecal coliform limit
violation in 2018. In 2019, the facility reported 1 pH limit violation, 4 ammonia limit violations and 1
TRC limit violation.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed 17 of 17 quarterly chronic toxicity tests from February 2016 to May
2020. The facility reported no flow for their August 2019 test. At the time the City had submitted its
NPDES renewal application (November 8, 2018), the facility had only completed one of the required
second species testing. The City has submitted results from four second species tests which have been
attached to this fact sheet. The City passed 4 of 4 second species tests conducted from September 2018 to
May 2019.
Summarize the results from the most recent compliance inspection: The last facility inspection conducted
in July 2019 reported that the facility was compliant.
6. Water Quality -Based Effluent Limitations (WQBELs)
Dilution and Mixina Zones
In accordance with 15A NCAC 213.0206, the following streamflows are used for dilution considerations
for development of WQBELs: 1Q10 streamflow (acute Aquatic Life); 7Q10 streamflow (chronic Aquatic
Life; non -carcinogen HH); 30Q2 streamflow (aesthetics); annual average flow (carcinogen, HH).
If applicable, describe any other dilution factors considered (e.g., based on CORMIX model results): NA
If applicable, describe any mixing zones established in accordance with I5A 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/1 for Municipals) may be appropriate if deemed more stringent based on dilution and
model results.
Ifpermit limits are more stringent than TBELs, describe how limits were developed.- Limitations for
summer and winter BOD5 are based on the results of a 1989 Level C model, when the facility was rated
at 5.5 MGD. These limits were confirmed in a later 1993 Qual2E model and were maintained in 2004
when the City requested an expanded flow tier at 6.5 MGD. No changes are proposed.
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.
Page 4 of 11

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/1 are considered compliant with their permit limit.
Describe any proposed changes to ammonia and/or TRC limits for this permit renewal: The current
permit sets a daily maximum limit of 28 ug/L. TRC limits have been reviewed in the attached WLA and
have been found to be consistent with the results. There are no proposed changes for TRC.
Limitations for summer and winter ammonia are based on 2004 Speculative Limits provided when the
Permittee originally requested to expand to 6.5 MGD. The current permit sets monthly average and
weekly average limits for ammonia in summer of 1 mg/L and 3 mg/L, respectively. The current permit
sets monthly average and weekly average limits for ammonia in winter of 2 mg/L and 6 mg/L,
respectively. The ammonia limits have been reviewed in the attached WLA and have been found to be
consistent with the results. There are no proposed changes for ammonia limits.
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 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 February 2016
through May 2020. 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: Cadmium, Copper, Silver, Bromodichloromethane
• 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: Lead
• 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: Arsenic, Cyanide, Total Chromium, Molybdenum, Nickel, Selenium, Zinc
• POTW Effluent Pollutant Scan Review: Three effluent pollutant scans were evaluated for
additional pollutants of concern. (PPAs from 2016, 2017 and 2018)
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: N/A
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: N/A
o 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
Page 5 of 11

the maximum predicted concentration was <50% of the allowable concentration: Total
Phenolic Compounds, Beryllium
Nitrate nitrogen was reviewed based on nitrate/nitrite samples reported . All values were less than 10
mg/L, the WS water quality standard. Chlorinated phenolic compounds were not detected in the PPA
scans submitted by the City. Chloroform was detected once in the PPAs reported by the City, but was at
levels significantly less than 60 ug/L, the EPA Nationally Recommended Water Quality Criteria for WS
waters.
Note: The laboratory employed analysis methods with insufficiently sensitive detection levels for total
lead data reported on 1/12/16, 1/19/16, 1/26/16, and 5/7/19. The data reported on each of these dates was
non -detect for total lead at < 20 ug/L. Including these in the RPA would skew the conclusions of the
analysis, so they were omitted. The Permittee shall report total lead using a Practical Quantification Level
(PQL) of at most 10 ug/L.
The City did not request a compliance schedule for the proposed total cadmium, total copper, total silver
or bromodichloromethane limits.
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.
Toxici , 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: The permit requires quarterly chronic toxicity testing at
60% effluent concentration. No changes are proposed.
Mercury Statewide TMDL Evaluation
There is a statewide TMDL for mercury approved by EPA in 2012. The TMDL target was to comply
with EPA's mercury fish tissue criteria (0.3 mg/kg) for human health protection. The TMDL established a
wasteload allocation for point sources of 37 kg/year (81 lb/year), and is applicable to municipals and
industrial facilities with known mercury discharges. Given the small contribution of mercury from point
sources (-2% of total load), the TMDL emphasizes mercury minimization plans (MMPs) for point source
control. Municipal facilities > 2 MGD and discharging quantifiable levels of mercury (>1 ng/1) will
receive an MMP requirement. Industrials are evaluated on a case -by -case basis, depending if mercury is a
pollutant of concern. Effluent limits may also be added if annual average effluent concentrations exceed
the WQBEL value (based on the NC WQS of 12 ng/1) and/or if any individual value exceeds a TBEL
value of 47 ng/1.
Page 6 of 11

Table 3. Mercury Effluent Data Summary (6.5 MGD)
2016
2017
2018
2019
2020
# of Samples
6
4
11
5
1
Annual Average Conc. n /L
2.3
0.7
1.2
1.48
0.5
Maximum Conc., n /L
3.90
1.40
2.90
2.90
0.5
TBEL, n /L
47
WQBEL, n /L
20.0
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. A mercury minimization plan (MMP) was implemented in the current permit. Since the
facility is > 2 MGD in design capacity and reported multiple quantifiable levels of mercury (> 1 ng/1), the
mercury minimization plan (MMP) will remain in the permit.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit:
In 1993, the Division developed a field -calibrated QUAL2E model of Hamby Creek and Abbotts Creek
below Thomasville. The model indicated that these streams have little capacity for oxygen -consuming
wastes. Nutrients, particularly phosphorus, heavily impact the Abbotts Creek Arm of High Rock Lake.
The Division updated its management strategy for the watershed in 1997 (Yadkin -Pee Dee River
Basinwide Water Quality Management Plan, May 1998). It recommended that (1) no new dischargers of
oxygen -consuming wastes be permitted in the watershed, (2) existing point source dischargers in this
drainage must significantly reduce nutrient discharges, and (3) the dischargers must within one year
conduct an operations optimization study for nutrient reduction.
In a 9/23/97 memo, the Division proposed a nutrient control strategy for the major dischargers into the
Abbotts Creek Arm of High Rock Lake (Lexington, Thomasville, and High Point). The Division notified
the City of this strategy when the permit was modified in 1998 and in several other discussions in recent
years.
A stakeholder group has been formed to determine a Nutrient Management Strategy for High Rock Lake
which will impact this discharge. As such, A Nutrient Reopener for High Rock Lake condition remains in
the permit.
7. Technology -Based Effluent Limitations (TBELs)
Municipals (if not applicable, delete and skip to Industrials)
Are concentration limits in the permit at least as stringent as secondary treatment requirements (30 mg11
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
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
Page 7 of 11

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 (YESINO): 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 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. While NPDES regulated facilities would initially be required to submit additional
NPDES reports electronically effective December 21, 2020, EPA extended this deadline from December
21, 2020, to December 21, 2025. The current compliance date, effective January 4, 2021, was extended as
a final regulation change published in the November 2, 2020 Federal Register This permit contains the
requirements for electronic reporting, consistent with Federal requirements.
Page 8 of 11

12.Summary of Proposed Permitting Actions:
Table 7. Current Permit Conditions and Proposed Changes 6.5 MGD
Parameter
Current Permit
Proposed Change
Basis for Condition/Change
Flow
MA 6.5 MGD
No change
15A NCAC 2B .0505
BOD5
Summer:
No change
WQBEL. 1989 Level C model,
MA 5.0 mg/1
1993 Qua12E model, 2004
WA 7.5 mg/1
Speculative Limits. 15A NCAC
Winter:
2B, protection of DO standard
MA 10.0 mg/1
WA 15.0 mg/1
NH3-N
Summer:
No change
WQBEL. 2004 Speculative Limits
MA 1.0 mg/1
and 2020 WLA review. 15A
WA 3.0 mg/1
NCAC 2B, protection of DO
Winter:
standard
MA 2.0 mg/l
WA 6.0 m /l
TSS
MA 30 mg/1
No change
TBEL. Secondary treatment
WA 45 mg/1
standards/40 CFR 133 / 15A
NCAC 2B .0406
Fecal coliform
MA 200 /100ml
No change
WQBEL. State WQ standard, 15A
WA 400 /100ml
NCAC 2B
DO
DA > 6 mg/1
No change
WQBEL. State WQ standard, 15A
NCAC 2B .0200
Temperature
Monitor and
No change
Surface Water Monitoring, 15A
Report Daily
NCAC 2B. 0500
pH
6 — 9 SU
No change
WQBEL. State WQ standard, 15A
NCAC 2B
Conductivity
Monitor and
No change
Surface Water Monitoring, 15A
Report Daily
NCAC 2B. 0500
Total Residual Chlorine
DM 28 ug/L
No change
WQBEL. 2004 Speculative Limits
and 2020 WLA review. State WQS
15A NCAC 2B
Total Nitrogen
Monitor and
No change
Surface Water Monitoring, 15A
Report Monthly
NCAC 2B. 0500
Total Phosphorous
Monitor and
No change
Surface Water Monitoring, 1997
Report Weekly
Memo of Nutrient Limits for Major
Dischargers to Abbotts Creek Arm
of High Rock Lake
TP Load
Summer:
No change
WQBEL. 1997 Memo of Nutrient
4,910 lbs
Limits for Major Dischargers to
Winter:
Abbotts Creek Arm of High Rock
6,930 lbs
Lake. For protection of chlorophyll
a standard, 15A NCAC 2B
Total Lead
No requirement
Monitor and Report
Based on results of Reasonable
Quarterly
Potential Analysis (RPA); No RP,
Predicted Max > 50% of
Allowable Cw - apply Quarterly
Page 9 of 11

Monitoring. State WQS 15A
NCAC 2B
Total Cadmium
No requirement
MA 1.8 ug/1
WQBEL. Based on results of
DM 10.8 ug/1
Reasonable Potential Analysis
(RPA); RP shown - apply Monthly
Monitor and Report
Monitoring with Limit. State WQS
Monthly
15A NCAC 2B
Total Copper
Monitor and
MA 27.4 ug/1
WQBEL. Based on results of
Report Quarterly
DM 37.1 ug/1
Reasonable Potential Analysis
(RPA); RP shown - apply Monthly
Monitor and Report
Monitoring with Limit. State WQS
Monthly
15A NCAC 2B
Total Zinc
Monitor and
Remove monitoring
Based on results of Reasonable
Report Quarterly
requirement
Potential Analysis (RPA); No RP,
Predicted Max < 50% of Allowable
Cw - No Monitoring required.
State WQS 15A NCAC 2B
Total Silver
Monitor and
MA 0.1 ug/1
WQBEL. Based on results of
Report Quarterly
DM 2.0 ug/1
Reasonable Potential Analysis
(RPA); RP shown - apply Monthly
Monitor and Report
Monitoring with Limit. State WQS
Monthly
15A NCAC 2B
Bromodichloromethane
Monitor and
MA 16.6 ug/1
WQBEL. Based on results of
Report Quarterly
Reasonable Potential Analysis
Monitor and Report
(RPA); RP shown - apply Monthly
Monthly
Monitoring with Limit. EPA
National Recommended Water
Quality Criteria
Total Hardness
No requirement
Quarterly monitoring
Hardness -dependent dissolved
Upstream and in
metals water quality standards
Effluent
approved in 2016
Chronic Toxicity
Chronic limit,
No change
WQBEL. No toxics in toxic
60% effluent
amounts. 15A NCAC 2B
Effluent Pollutant Scan
Three times per
No change; conducted
40 CFR 122
permit cycle
in 2022, 2023, 2024
Mercury Minimization
MMP Special
No change
WQBEL. Consistent with 2012
Plan (MMP)
Condition
Statewide Mercury TMDL
Implementation; Municipality with
Q > 2 MGD and with multiple
detects > 1 ng/L. State WQS 15A
NCAC 2B
Electronic Reporting
Electronic
No change
In accordance with EPA Electronic
Reporting Special
Reporting Rule 2015.
Condition
MGD — Million gallons per day, MA - Monthly Average, WA — Weekly Average, DM — Daily Max, QA
— Quarterly Average, DA — Daily Average
Page 10 of 11

13. Public Notice Schedule:
Permit to Public Notice: September 11, 2020
Per 15A NCAC 2H .0109 & .0111, The Division will receive comments for a period of 30 days following
the publication date of the public notice. Any request for a public hearing shall be submitted to the
Director within the 30 days comment period indicating the interest of the party filing such request and the
reasons why a hearing is warranted.
14. Fact Sheet Addendum (if applicable):
The draft permit was submitted to the City of Lexington, EPA Region IV, the Winston-Salem Regional
Office, and the Division's Operator Certification Program, Aquatic Toxicology Branch, Ecosystems
Branch and Public Water Supply Regional Officer. The Aquatic Toxicology Branch submitted a comment
to correct the mailing address specified in Special Condition A.(3.). No comments were received from
any of the other parties.
The Public Water Supply Regional Officer submitted a memo concurring with the issuance of the permit.
This memo has been attached to the fact sheet.
Were there any changes made since the Draft Permit was public noticed (Yes/No): YES
If Yes, list changes and their basis below:
Footnote numbering was corrected to accurately associate parameters with applicable footnotes
[See A.(1.)].
A notation was made concerning the Electronic Reporting Rule — Phase 2 Extension. extended
the Phase 2 deadline from December 21, 2020, to December 21, 2025, effective January 4, 2021.
The current compliance date has been extended to reflect this change.
The DWR Aquatic Toxicology Branch mailing address has been corrected [See A.(3.)].
15. Fact Sheet Attachments (if applicable):
• RPA Spreadsheet Summary
• BOD and TSS Removal
• Dissolved Metals Implementation/Freshwater
• Waste Load Allocation Spreadsheet
• Mercury TMDL Spreadsheet
• Limit Violations Summary
• Toxicity Summary
• Pretreatment Summary
Page 11 of 11

42008346
J000666839
AFFIDAVIT OF PUBLICATION
STATE OF NORTH CAROLINA LEXINGTON, NC September 11, 2020
DAVIDSON COUNTY
1, Lynn Bowers OF THE DISPATCH, A NEWSPAPER PUBLISHED IN THE CITY OF LEXINGTON, COUNTYAND STATE
AFORESAID, BEING DULY SWORN, SAYS THE FOREGOING LEGAL OF WHICH THE ATTACHED IS A TRUE COPY,
WAS PUBLISHED IN SAID NEWSPAPER ONCE, BEGINNING THE 11th DAY OF September, 2020.
PUBLICATION FEE: $ 97.87
(SEAL)
SWA610 ANDSUBSCReE HIS // DAYOF—,A�
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MY COMMISSION EXPIRES-
Ad Copy:
Public Notice
North Carolina Environmental
Management
Commission/NPDES Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
Notice of latent to Issue a
NPDES Wastewater Permit
NC0055786 City of Lexington
The North Carolina
Environmental Management
Commission proposes to issue
a NPDES wastewater
discharge permit to the
person(s) listed below. Written
comments regarding the
proposed permit will be
accepted until 30 days after the
Publish date of this notice. The
Director of the NC Division of
Water Resources (DWR) may
hold a public hearing should
there be a significant degree of
public interest. Please mail
comments and/or information
requests to DWR at the above
address. Interested persons
may visit the DWR at 512 N.
Salisbury Street, Raleigh, NC
to review information on file.
Additional information on
NPDES permits and this notice
may be found on our website:
htt ://de .nc. ov/abouUdivision
slwater-resou rceslwater-
resources- ermitslwastewater-
branchln des -
wastewater) ublic-notices, or
by calling [phone]. The
City of Lexington has
requested renewal of permit
NCO055786 for its Lexington
Regional WWTP in Davidson
County; this permitted
discharge is treated municipal
and industrial wastewater to
Abbotts Creek, in the Yadkin -
Pee Dee River Basin.
September 11, 2020
P F�'P
Notary Public
Dovrdson County
Mym sie�ti

ROY COOPER
Govelwoi�
MICHAEL S. REGAN
Secretary
S. DANIEL SMITH
Dilvclol�
September 11, 2020
MEMORANDUM
To: Jeff Bryan
NC DEQ / DWR / Public Water Supply Regional Engineer
Winston-Salem Regional Office
From: Nick Coco
919-707-3609
NPDES Unit
Subject: Review of Draft NPDES Permit NCO055786
Lexington Regional WWTP
Davidson County
Please indicate below your agency's position or viewpoint on the draft permit and return this form by October 12,
2020. If you have any questions on the draft permit, please feel free to contact me at the telephone number shown
above.
RESPONSE: (Check one)
Concur with the issuance of this pen -nit provided the facility is operated and maintained properly, the stated
effluent limits are met prior to discharge, and the discharge does not contravene the designated water quality
standards.
1-1 Concurs with issuance of the above permit, provided the following conditions are met:
F-1 Opposes the issuance of the above permit, based on reasons stated below, or attached:
gO�—
ned
UJ S7,
10 H I -ZO 'Lo ,
N(,,Ahing
State ot'North Carolina I Environmental Quality
1611 Mail Service Center I Raleigh, North Carolina 27699-1611
919-707-9000

Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators
MAXIMUM DATA POINTS = 58
REQUIRED DATA ENTRY CHECK WQS
Table 1. Project Information
❑ CHECK IF HQW OR ORW WQS
Facility Name
Lexington Regional WWTP
WWTP/WTP Class
IV
NPDES Permit
NCO055786
Outfall
001
Flow, Qw (MGD)
6.500
Receiving Stream
Abbotts Creek
HUC Number
03040103
Stream Class
❑� Apply WS Hardness WQC
WS-V; B
7Q10s (cfs)
6.700
15.00
7Q10w (cfs)
18.00
30Q2 (cfs)
167.00
QA (cfs)
5.57
1Q10s (cfs)
I 67.67 mg/L (Avg)
Effluent Hardness
Upstream Hardness
I 46.5 mg/L (Avg)
Combined Hardness Chronic
I 59.21 mg/L
Combined Hardness Acute
I 60.13 mg/L
Data Source(s)
Bromodichloromethane based on EPA Nationally
Recommended Water Quality Criteria
❑ CHECK TO APPLY MODEL
Par01
Par02
Par03
Par04
Par05
Par0611111
Par07
Par08
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
1.1318
FW
6.9675
ug/L
Chlorides
Aquatic Life
NC
230
FW
mg/L
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
238.5563
FW
1857.1864
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
16.4645
FW
23.9417
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
7.7009
FW
201.0070
ug/L
Mercury
Aquatic Life
NC
12
FW
0.5
ri
Molybdenum
Human Health
NC
2000
HH
ug/L
Nickel
Aquatic Life
NC
77.2172
FW
704.3268
pg/L
Nickel
Water Supply
NC
25.0000
WS
N/A
pg/L
Selenium
Aquatic Life
NCI
5
FW
1 56
ug/L
Silver
Aquatic Life
NC
0.06
FW
1.3411
ug/L
Zinc
Aquatic Life
NC
263.1379
FW
264.4282
ug/L
Bromodichloromethane
Water Supply
C
0.95
WS
pg/L
55786 RPA, input
8/10/2020

1
2
3
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
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
REASONABLE POTENTIAL ANALYSIS
H2
Use"PASTE SPECIAL Use"PASTE SPECIAL
Effluent Hardness Values" then "COPY" Upstream Hardness Values" then "COPY"
. Maximum data . Maximum data
points = 58 1 points = 58
Date Data
BDL=1/2DL
Results
Date
Data
BDL=1/2DL
Results
5/14/2019
83
83
Std Dev.
7.5561
1
2/21/2020
37
37
Std Dev.
7.5565
9/6/2019
69
69
Mean
67.6667
2
3/6/2020
42
42
Mean
46.5000
9/13/2019
66
66
C.V.
0.1117
3
4/9/2020
55
55
C.V. (default)
0.6000
9/20/2019
71
71
n
15
4
5/8/2020
56
56
n
6
9/27/2019
64
64
10th Per value
60.80 mg/L
5
6/5/2020
43
43
10th Per value
39.50 mg/L
10/3/2019
69
69
Average Value
67.67 mg/L
6
7/10/2020
46
46
Average Value
46.50 mg/L
10/11/2019
71
71
Max. Value
83.00 mg/L
7
Max. Value
56.00 mg/L
10/18/2019
71
71
8
10/25/2019
62
62
9
11/1/2019
69
69
10
11/8/2019
69
69
11
11/15/2019
72
72
12
11/22/2019
71
71
13
11/27/2019
60
60
14
2/13/2020
48
48
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
55786 RPA, data
1 8/10/2020

REASONABLE POTENTIAL ANALYSIS
1
2
3
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
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
& Par02
Arsenic
Date
Data
BDL=1/2DL
1/5/2016
<
10
5
6/7/2016
<
10
5
8/2/2016
<
10
5
11/8/2016
<
5
2.5
2/7/2017
<
5
2.5
5/2/2017
<
5
2.5
8/1/2017
<
5
2.5
11/7/2017
<
5
2.5
2/5/2018
<
5
2.5
3/6/2018
<
5
2.5
4/10/2018
<
5
2.5
5/1/2018
<
5
2.5
6/5/2018
<
5
2.5
7/10/2018
<
5
2.5
8/7/2018
<
5
2.5
8/28/2018
<
3
1.5
9/11/2018
<
5
2.5
9/24/2018
<
5
2.5
10/9/2018
<
3
1.5
12/4/2018
<
3
1.5
5/7/2019
<
3
1.5
8/6/2019
<
3
1.5
11/5/2019
<
3
1.5
2/4/2020
<
2
1
5/5/2020
<
2
1
Use"PASTE SPECIAL
Values" then "COPY"
. Maximum data
points = 58
Results
Std Dev.
1.1023
Mean
2.4400
C.V.
0.4518
n
25
Mult Factor = 1.21
Max. Value 5.0 ug/L
Max. Pred Cw 6.1 ug/L
-2-
55786 RPA, data
8/10/2020

REASONABLE POTENTIAL ANALYSIS
Beryllium
Date
Data
BDL=1/2DL
Results
1
9/24/2018
< 1
0.5
Std Dev.
2
5/7/2019
< 1
0.5
Mean
3
2/5/2016
< 1
0.5
C.V. (default)
4
5/9/2017
< 1
0.5
n
5
6
Mult Factor =
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
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Use"PASTE SPECIAL Paf04
Values" then "COPY"
. Maximum data
points = 58
0.5000
0.6000
4
2.59
0.50 ug/L
1.30 ug/L
Date Data
1 1/5/2016 <
2 1/12/2016 <
3 1/19/2016 <
4 1/26/2016 <
5 2/2/2016 <
6 6/7/2016 <
7 8/2/2016 <
8 11/8/2016 <
9 2/7/2017 <
10 5/2/2017 <
11 8/1/2017 <
12 11/7/2017 <
13 2/5/2018 <
14 3/6/2018 <
15 4/10/2018 <
16 5/1/2018 <
17 6/5/2018 <
18 7/10/2018 <
19 8/7/2018 <
20 8/28/2018 <
21 9/11/2018
22 9/24/2018 <
23 10/9/2018 <
24 11/6/2018 <
25 12/4/2018 <
26 1/8/2019 <
27 5/7/2019 <
28 8/6/2019 <
29 11 /5/2019
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Cadmium
BDL=1/2DL
Results
2
1
Std Dev.
2
1
Mean
2
1
C.V.
2
1
n
1
0.5
0.5
0.25
Mult Factor =
0.5
0.25
Max. Value
0.5
0.25
Max. Pred Cw
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
1.85
1.85
1
0.5
0.5
0.25
0.5
0.25
0.5
0.25
0.5
0.25
5
2.5
0.5
0.25
0.9
0.9
Use"PASTE SPECIAL
Values" then "COPY"
.Maximum data
points = 58
0.5259
1.0299
29
1.35
2.500 ug/L
3.375 ug/L
-3-
55786 RPA, data
8/10/2020

REASONABLE POTENTIAL ANALYSIS
If07
Total Phenolic Compounds
Use"PASTE SPECIAL
Values" then "COPY"
Par10
. Maximum data
points = 58
Date
Data BDL=1/2DL
Results
Date
Data
1
2/12/2016
< 10 5
Std Dev.
0.0000
1
1/5/2016
<
2
5/15/2017
< 10 5
Mean
5.0000
2
2/2/2016
<
3
9/25/2018
< 10 5
C.V. (default)
0.6000
3
6/7/2016
<
4
n
3
4
8/2/2016
<
5
5
11/8/2016
<
6
Mult Factor =
3.00
6
2/7/2017
<
7
Max. Value
5.0 ug/L
7
5/2/2017
<
8
Max. Pred Cw
15.0 ug/L
8
8/1/2017
<
9
9
11/7/2017
<
10
10
2/5/2018
<
11
11
3/6/2018
<
12
12
4/10/2018
<
13
13
5/1/2018
<
14
14
7/10/2018
<
15
15
8/7/2018
<
16
16
8/28/2018
<
17
17
9/11/2018
<
18
18
9/24/2018
<
19
19
10/9/2018
<
20
20
5/7/2019
<
21
21
8/6/2019
<
22
22
11/5/2019
<
23
23
2/4/2020
<
24
24
5/5/2020
<
25
25
26
26
27
27
28
28
29
29
30
30
31
31
32
32
33
33
34
34
35
35
36
36
37
37
38
38
39
39
40
40
41
41
42
42
43
43
44
44
45
45
46
46
47
47
48
48
49
49
50
50
51
51
52
52
53
53
54
54
55
55
56
56
57
57
58
58
Chromium, Total
BDL=1/2DL
Results
5
2.5
Std Dev.
5
2.5
Mean
5
2.5
C.V.
5
2.5
n
5
2.5
5
2.5
Mult Factor =
5
2.5
Max. Value
5
2.5
Max. Pred Cw
5
2.5
2
1
5
2.5
5
2.5
5
2.5
5
2.5
5
2.5
2
1
5
2.5
5
2.5
2
1
2
1
2
1
2
1
2
1
2
1
Use"PASTE SPECIAL
Values" then "COPY"
.Maximum data
points = 58
2.0000
0.3612
24
1.17
2.5 Ng/L
2.9 Ng/L
55786 RPA, data
-4- 8/10/2020

REASONABLE POTENTIAL ANALYSIS
0
Copper
Date
Data
BDL=1/2DL
Results
1
1/5/2016
10.2
10.2
Std Dev.
2
2/2/2016
<
10
5
Mean
3
3/1/2016
<
20
10
C.V.
4
4/5/2016
<
20
10
n
5
5/3/2016
<
20
10
6
6/7/2016
6.72
6.72
Mult Factor =
7
8/2/2016
34.7
34.7
Max. Value
8
9/6/2016
<
20
10
Max. Pred Cw
9
10/4/2016
<
20
10
10
11/8/2016
10.5
10.5
11
12/6/2016
<
20
10
12
1/3/2017
<
20
10
13
2/7/2017
9.81
9.81
14
3/7/2017
<
20
10
15
4/4/2017
<
20
10
16
5/2/2017
12.7
12.7
17
6/6/2017
22.4
22.4
18
7/5/2017
23.7
23.7
19
8/1/2017
11.7
11.7
20
9/5/2017
<
20
10
21
10/3/2017
<
20
10
22
11/7/2017
8.49
8.49
23
12/5/2017
<
20
10
24
1/2/2018
<
20
10
25
2/5/2018
7.55
7.55
26
3/6/2018
<
2
1
27
4/10/2018
<
2
1
28
5/1/2018
2.15
2.15
29
6/5/2018
5.25
5.25
30
7/10/2018
4
4
31
8/7/2018
<
2
1
32
8/28/2018
5
5
33
10/9/2018
3
3
34
11/6/2018
2
2
35
12/4/2018
4
4
36
1/8/2019
5
5
37
2/5/2019
<
10
5
38
3/5/2019
<
10
5
39
4/2/2019
<
10
5
40
5/7/2019
2
2
41
6/4/2019
<
10
5
42
7/2/2019
<
10
5
43
8/6/2019
3
3
44
9/4/2019
<
10
5
45
10/1/2019
<
10
5
46
11/5/2019
4
4
47
12/3/2019
<
10
5
48
1/7/2020
<
10
5
49
2/4/2020
3
3
50
3/3/2020
<
10
5
51
4/7/2020
<
10
5
52
5/5/2020
3
3
53
54
55
56
57
58
Use"PASTE SPECIAL
Values" then "COPY"
. Maximum data
points = 58 fr12
7.6321
0.7781
52
1.04
34.70 ug/L
36.09 ug/L
Date Data
1 1/5/2016 <
2 2/2/2016 <
3 6/7/2016 <
4 8/2/2016 <
5 11/8/2016 <
6 2/7/2017 <
7 5/2/2017 <
8 11/7/2017 <
9 2/5/2018 <
10 3/6/2018 <
11 4/10/2018 <
12 5/1/2018 <
13 6/5/2018 <
14 7/10/2018 <
15 8/28/2018 <
16 9/11/2018 <
17 9/25/2018 <
18 10/9/2018 <
19 11/6/2018 <
20 12/4/2018 <
21 1/8/2019 <
22 5/7/2019 <
23 8/6/2019 <
24 11/5/2019 <
25 1/5/2016 <
26 2/2/2016 <
27 6/7/2016 <
28 8/2/2016 <
29 11/8/2016 <
30 2/7/2017 <
31 5/2/2017 <
32 8/1/2017 <
33 11/7/2017 <
34 2/6/2018 <
35 3/6/2018 <
36 4/10/2018
37 5/1/2018 <
38 6/5/2018 <
39 7/10/2018 <
40 8/28/2018 <
41 9/11/2018
42 10/9/2018 <
43 11/6/2018 <
44 12/4/2018 <
45 1/8/2019 <
46 5/7/2019 <
47 8/6/2019 <
48 11/5/2019 <
49
50
51
52
53
54
55
56
57
58
Cyanide
BDL=1/2DL
Results
5 5
Std Dev.
5 5
Mean
5 5
C.V.
5 5
n
5 5
5 5
Mult Factor =
5 5
Max. Value
5 5
Max. Pred Cw
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
5 5
Use"PASTE SPECIAL
Values" then "COPY"
.Maximum data
points = 58
5.00
0.0000
48
1.00
5.0 ug/L
5.0 ug/L
55786 RPA, data
-5- 8/10/2020

REASONABLE POTENTIAL ANALYSIS
4
Lead
Date
BDL=1/2DL
Results
1
1/5/2016
<
10
5
Std Dev.
2
2/2/2016
<
5
2.5
Mean
3
6/7/2016
<
2
1
C.V.
4
8/2/2016
4.49
4.49
n
5
11/8/2016
3.1
3.1
6
2/7/2017
3.36
3.36
Mult Factor =
7
5/2/2017
<
2
1
Max. Value
8
8/1/2017
3.94
3.94
Max. Pred Cw
9
11/7/2017
5.13
5.13
10
2/5/2018
4.8
4.8
11
3/6/2018
2.42
2.42
12
4/10/2018
3.63
3.63
13
5/1/2018
2.9
2.9
14
6/5/2018
2.74
2.74
15
7/10/2018
<
2
1
16
8/7/2018
<
2
1
17
8/28/2018
<
2
1
18
9/11/2018
<
5
2.5
19
9/24/2018
<
5
2.5
20
10/9/2018
<
2
1
21
11/6/2018
<
2
1
22
12/4/2018
<
2
1
23
1/8/2019
<
2
1
24
8/6/2019
<
2
1
25
11/5/2019
<
2
1
26
2/4/2020
<
2
1
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Par16
Use"PASTE SPECIAL Use"PASTE SPECIAL
Values" then "COPY" Molybdenum Values" then "COPY"
. Maximum data . Maximum data
points = 58 points = 58
2.3465
0.6233
26
1.27
5.130 ug/L
6.515 ug/L
Date
Data
BDL=1/2DL
Results
1
1/5/2016
<
10
5
Std Dev.
2
6/7/2016
<
10
5
Mean
3
8/2/2016
<
10
5
C.V.
4
11/8/2016
<
5
2.5
n
5
2/7/2017
<
5
2.5
6
5/2/2017
<
5
2.5
Mult Factor =
7
8/1/2017
6.98
6.98
Max. Value
8
11/7/2017
<
5
2.5
Max. Pred Cw
9
2/5/2018
<
5
2.5
10
3/6/2018
13.2
13.2
11
4/10/2018
10.2
10.2
12
5/1/2018
<
5
2.5
13
6/5/2018
<
5
2.5
14
7/10/2018
6
6
15
8/7/2018
<
5
2.5
16
8/28/2018
<
5
2.5
17
9/11/2018
<
5
2.5
18
10/9/2018
<
5
2.5
19
12/4/2018
<
5
2.5
20
1/8/2019
<
5
2.5
21
5/7/2019
<
5
2.5
22
8/6/2019
<
5
2.5
23
11/5/2019
<
5
2.5
24
2/4/2020
<
5
2.5
25
5/5/2020
<
5
2.5
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
3.8552
0.7083
25
1.32
13.2 ug/L
17.4 ug/L
55786 RPA, data
-6- 8/10/2020

REASONABLE POTENTIAL ANALYSIS
7 & Par18
Nickel
Date
Data
BDL=1/2DL
Results
1
1/5/2016
<
10
5
Std Dev.
2
1/19/2016
<
20
10
Mean
3
2/2/2016
<
10
5
C.V.
4
6/7/2016
<
2
1
n
5
8/2/2016
<
2
1
6
11/8/2016
<
2
1
Mult Factor =
7
2/7/2017
<
2
1
Max. Value
8
5/2/2017
<
2
1
Max. Pred Cw
9
8/1/2017
<
2
1
10
11/7/2017
2.34
2.34
11
2/5/2018
<
2
1
12
3/6/2018
2.23
2.23
13
4/10/2018
2.19
2.19
14
5/1/2018
5.1
5.1
15
6/5/2018
6.83
6.83
16
7/10/2018
3.16
3.16
17
8/7/2018
2.25
2.25
18
8/28/2018
2.02
2.02
19
9/11/2018
2.51
2.51
20
9/24/2018
<
10
5
21
10/9/2018
6.27
6.27
22
11/6/2018
2.51
2.51
23
12/4/2018
<
2
1
24
1/8/2019
<
2
1
25
5/7/2019
2.47
2.47
26
8/6/2019
2.72
2.72
27
11/5/2019
4.65
4.65
28
2/4/2020
<
2
1
29
5/5/2020
<
2
1
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Use "PASTE SPECIAL
Values" then "COPY"
. Maximum data
points = 58 Par19
2.8707
0.7819
29
1.28
10.0 Ng/L
12.8 Ng/L
Date Data
1 1/5/2016 <
2 1/12/2016 <
3 1/19/2016 <
4 1/26/2016 <
5 2/2/2016 <
6 6/7/2016 <
7 8/2/2016 <
8 11/8/2016 <
9 2/7/2017 <
10 5/2/2017 <
11 8/1/2017 <
12 11/7/2017 <
13 2/5/2018 <
14 3/6/2018 <
15 4/10/2018 <
16 5/1/2018 <
17 6/5/2018 <
18 7/10/2018 <
19 8/7/2018 <
20 8/28/2018 <
21 9/11/2018 <
22 9/24/2018 <
23 10/9/2018 <
24 11/6/2018 <
25 12/4/2018 <
26 1/8/2019 <
27 5/7/2019 <
28 8/6/2019 <
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Selenium
BDL=1/2DL
Results
5 2.5
Std Dev.
5 2.5
Mean
5 2.5
C.V.
5 2.5
n
10 5
5 2.5
Mult Factor =
5 2.5
Max. Value
5 2.5
Max. Pred Cw
5 2.5
5 2.5
5 2.5
5 2.5
5 2.5
5 2.5
5 2.5
5 2.5
5 2.5
3 1.5
3 1.5
3 1.5
3 1.5
10 5
3 1.5
3 1.5
3 1.5
3 1.5
3 1.5
3 1.5
Use"PASTE
SPECIAL -Values"
then "COPY".
Maximum data
points = 58
2.3214
0.3854
28
1.15
5.0 ug/L
5.8 ug/L
55786 RPA, data
-7- 8/10/2020

REASONABLE POTENTIAL ANALYSIS
Silver
Date
Data
BDL=1/2DL
Results
1
1/5/2016
<
5
2.5
Std Dev.
2
2/2/2016
<
5
2.5
Mean
3
3/1/2016
<
5
2.5
C.V.
4
4/5/2016
<
5
2.5
n
5
5/3/2016
<
5
2.5
6
6/7/2016
<
5
2.5
Mult Factor =
7
8/2/2016
<
5
2.5
Max. Value
8
9/6/2016
<
5
2.5
Max. Pred Cw
9
10/4/2016
<
5
2.5
10
11/8/2016
<
5
2.5
11
12/6/2016
<
5
2.5
12
1/3/2017
<
5
2.5
13
2/7/2017
<
5
2.5
14
3/7/2017
<
5
2.5
15
4/4/2017
<
5
2.5
16
5/2/2017
<
5
2.5
17
6/6/2017
<
5
2.5
18
7/5/2017
<
5
2.5
19
8/1/2017
<
5
2.5
20
9/5/2017
<
5
2.5
21
10/3/2017
<
5
2.5
22
11/7/2017
<
5
2.5
23
12/5/2017
<
5
2.5
24
1/2/2018
<
5
2.5
25
2/5/2018
<
5
2.5
26
3/6/2018
<
5
2.5
27
4/10/2018
<
5
2.5
28
5/1/2018
<
5
2.5
29
6/5/2018
<
5
2.5
30
7/10/2018
<
5
2.5
31
8/7/2018
<
5
2.5
32
8/28/2018
<
1
0.5
33
9/11/2018
<
5
2.5
34
9/24/2018
<
5
2.5
35
10/9/2018
<
1
0.5
36
11/6/2018
<
1
0.5
37
12/4/2018
<
1
0.5
38
1/8/2019
<
1
0.5
39
2/5/2019
<
5
2.5
40
3/5/2019
<
5
2.5
41
4/2/2019
<
5
2.5
42
5/7/2019
<
1
0.5
43
6/4/2019
<
5
2.5
44
7/2/2019
<
5
2.5
45
8/6/2019
<
5
2.5
46
9/4/2019
<
5
2.5
47
10/1/2019
<
5
2.5
48
11/1/2019
<
5
2.5
49
11/5/2019
<
1
0.5
50
12/3/2019
<
5
2.5
51
1/7/2020
<
5
2.5
52
2/4/2020
1
1
53
3/3/2020
<
5
2.5
54
4/7/2020
<
5
2.5
55
5/5/2020
<
1
0.5
56
57
58
Use "PASTE SPECIAL Par21
Values" then "COPY"
. Maximum data
points = 58
2.1818
0.3340
55
1.01
2.500 ug/L
2.525 ug/L
Date
1 1/5/2016
2 2/2/2016
3 3/1/2016
4 4/5/2016
5 5/3/2016
6 6/7/2016
7 8/2/2016
8 9/6/2016
9 10/4/2016
10 11/8/2016
11 12/6/2016
12 1/3/2017
13 2/7/2017
14 3/7/2017
15 4/4/2017
16 5/2/2017
17 6/6/2017
18 8/1/2017
19 9/5/2017
20 10/3/2017
21 11/7/2017
22 12/5/2017
23 1 /2/2018
24 2/5/2018
25 3/6/2018
26 4/10/2018
27 5/1/2018
28 6/5/2018
29 7/10/2018
30 8/7/2018
31 8/28/2018
32 9/11/2018
33 9/24/2018
34 10/9/2018
35 11 /6/2018
36 12/4/2018
37 1 /8/2019
38 2/5/2019
39 3/5/2019
40 4/2/2019
41 5/7/2019
42 6/4/2019
43 7/2/2019
44 8/6/2019
45 9/4/2019
46 10/1 /2019
47 11 /1 /2019
48 11 /5/2019
49 12/3/2019
50 2/4/2020
51 3/3/2020
52 5/5/2020
53
54
55
56
57
58
Zinc
Data
BDL=1/2DL
Results
38
38
Std Dev.
65
65
Mean
51.2
51.2
C.V.
46.6
46.6
n
52.8
52.8
41.6
41.6
Mult Factor =
35.1
35.1
Max. Value
64.3
64.3
Max. Pred Cw
62.95
62.95
77.3
77.3
62.7
62.7
89.3
89.3
77.5
77.5
45.8
45.8
49.5
49.5
27.7
27.7
36.2
36.2
66.1
66.1
24.5
24.5
51.8
51.8
55.4
55.4
67.3
67.3
61
61
30
30
28
28
55.9
55.9
48.2
48.2
33.77
33.77
54
54
28
28
77
77
57
57
49
49
92
92
89
89
66
66
47
47
75
75
45
45
70
70
38
38
44
44
48
48
42
42
63
63
65
65
65
65
63
63
59
59
38
38
44
44
26
26
Use"PASTE SPECIAL
Values" then "COPY"
.Maximum data
points = 58
53.6446
0.3151
52
1.02
92.0 ug/L
93.8 ug/L
-8-
55786 RPA, data
8/10/2020

REASONABLE POTENTIAL ANALYSIS
1
2
3
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
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Use"PASTE SPECIAL
Bromodichloromethane Values"then "COPY"
.Maximum data
points = 58
Date Data
BDL=1/2DL
2/2/2016 <
5
2.5
6/7/2016 <
5
2.5
8/2/2016 <
5
2.5
11/8/2016
8
8
2/2/2017
12.7
12.7
5/2/2017
7.4
7.4
8/1/2017
15
15
11/7/2017
5.2
5.2
2/6/2018 <
5
2.5
3/7/2018 <
5
2.5
4/10/2018 <
5
2.5
5/1/2018 <
5
2.5
6/5/2018 <
5
2.5
7/3/2018 <
5
2.5
8/28/2018 <
5
2.5
9/25/2018 <
5
2.5
10/9/2018 <
5
2.5
11/6/2018 <
5
2.5
12/4/2018 <
5
2.5
1/8/2019 <
5
2.5
5/14/2019 <
5
2.5
8/6/2019 <
5
2.5
11/5/2019 <
5
2.5
2/4/2020 <
5
2.5
5/5/2020 <
5
2.5
Results
Std Dev.
3.3577
Mean
3.9320
C.V.
0.8539
n
25
Mult Factor = 1.38
Max. Value 15.000000 Ng/L
Max. Pred Cw 20.700000 Ng/L
-9-
55786 RPA, data
8/10/2020

Lexington Regional WWTP
NCO055786 Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators
MAXIMUM DATA POINTS = 58
Qw (MGD) =
6.5000
WWTP/WTP Class: IV
1Q10S (cfs) =
5.57
IWC% @ 1Q10S = 64.39757111
7Q10S (cfs) =
6.70
IWC% @ 7Q10S = 60.05961252
7Q10W (cfs) =
15.00
IWC% @ 7Q10W = 40.17946162
30Q2 (cfs) =
18.00
IWC% @ 30Q2 = 35.88601959
Avg. Stream Flow, QA (cfs) =
167.00
IW°/uC @ QA = 5.689679514
Receiving Stream:
Abbotts Creek HUC 03040103
Stream Class: WS-V;B
Outfall 001
Qw = 6.5 MGD
COMBINED HARDNESS (mg/L)
Acute = 60.13 mg/L
Chronic = 59.21 mg/L
YOU HAVE DESIGNATED THIS RECEIVING
STREAM AS WATER SUPPLY
Effluent Hard: 0 value > 100 mg/L
Effluent Hard Avg = 67.67 mg/L
PARAMETER
NC STANDARDS OR EPA CRITERIA
J
In
REASONABLE POTENTIAL RESULTS
RECOMMENDED ACTION
TYPE
IL
�
Applied
Chronic Acute
n # Det. Max Pred Cw Allowable Cw
Standard
Acute (FW): 528.0
Arsenic
C
150 FW(7Q10s) 340
ua/L
25 0
6.1
Chronic (F--- 249.8------------------------------
W):
Mai M_DL=10---------------
Arsenic
C
10 HHIWS(Qavg)
ua L
NO DETECTS
Chronic (HH): 175.8
_ --------------------
No RP, Predicted Max < 50 % of Allowable Cw - No
Max MDL = 10
Monitoring required
Acute: 100.94
Beryllium
NC
6.5 FW(7Q10s) 65
ug/L
4 0
1.30
Note: n S 9
C.V. (default)
Chronic: 10.82
No RP, Predicted Max < 50 % of Allowable Cw - No
Limited data set
NO DETECTS
Max MDL = I
Monitoring required
Acute: 10.819
Cadmium
NC
1.1318 FW(7Q10s) 6.9675
ug/L
29 2
3.375
_ _ _ _ _ _
Chronic: 1.884
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
RP shown apply Monthly Monitoring with Limit
1 values > Allowable Cw
Acute: NO WQS
Total Phenolic Compounds
NC
300 A(30Q2)
ug/L
3 0
15.0
_ _ _ _ ___ _ _
_ _ _ _ _ ------------------
Note: n S 9
C.V. (default)
Chronic: 836.0
No RP, Predicted Max < 50 % of Allowable Cw - No
Limited data set
NO DETECTS
Max MDL = 10
Monitoring required
Acute: 2,883.9
Chromium III
NC
238.5563 FW(7Q10s) 1857.1864
µg/L
0 0
N/A
_ _ _397._
C1170nic:----- 2--
---------------------------
Acute: 24.8
Chromium VI
NC
11 FW(7Q10s) 16
µg'L
0 0
N/A
_ _ _ _ _
Chronic:----- 18.3 --
---------------------------
Chromium, Total
NC
µg/L
24 0
2.9
Max reported value = 2.5
a: No monitoring required if all Total Chromium
samples are < 5 pg/L or Pred. max for Total Cr is <
allowable Cw for Cr VI.
NO DETECTS
Max MDL = 5
Acute: 37.18
Copper
NC
16.4645 FW(7Q10s) 23.9417
ue/L
52 24
36.09
_ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Chronic:
_
RP shown apply Monthly Monitoring with Limit
le C
1 values > Allowable Cw
Acute: 34.2
Cyanide
NC
5 FW(7Q10s) 22
10
ug/L
48 2
5.0
_ _ _ _ _ _ _
Chronic: 8.3
___
All values reported < 10 ug/L No monitoring
No value > Allowable Cw
required
55786 RPA, rpa
Page 1 of 2 8/10/2020

Lexington Regional WWTP I Outfall 001
NCO055786 Freshwater RPA - 95% Probability/95% Confidence Using Metal Translators Qw = 6.5 MGD
Acute: 312.134
Lead
INC
7.7009 FW(7Q10s) 201.0070
ug/L
26 10
6.515
Chronic: 12.822
_ _
No RP, Predicted Max >_ 50 % of Allowable Cw
No value > Allowable Cw
apply Quarterly Monitoring
Acute: NO WQS
Molybdenum
INC
2000 HH(7Q10s)
ug/L
25 4
17.4
Chronic: 3,330.0
No RP, Predicted Max < 50 % of Allowable Cw - No
No value > Allowable Cw
Monitoring required
Acute (FW): 1,093.7
Nickel
INC
77.2172 FW(7Q10s) 704.3268
µg/L
— —
— — — — — — — — — — — — — —
29 14
12.8
Chronic(FW): 128.6
No value > Allowable Cw
Nickel
INC
25.0000 WS(7Q10s)
µg/L
Chronic(WS): 41.6
No RP, Predicted Max <50%ofAllowable Cw-No
No value > Allowable Cw
Monitoring required
Acute: 87.0
Selenium
INC
5 FW(7Q10s) 56
ug/L
28 0
5.8
Chronic:----- 8.3 --
---------------------------
All values non -detect < 10 ug/L, 5 ug/L and 3 ug/L.
No monitoring required. Permittee shall report to PQL
NO DETECTS
Maas MDL = 10
of at most 5 ug/L.
Acute: 2.083
Silver
INC
0.06 FW(7Q10s) 1.3411
ug/L
55 1
2.525
__ _ _ _ ___
Chronic: 0.100
_ _ _ _ _ _ _ _ _ _ _ _ ___
RP shown - apply Monthly Monitoring with Limit
55 values > Allowable Cw
Acute: 410.6
Zinc
INC
263.1379 FW(7QlOs) 264.4282
ug/L
52 52
93.8
Chronic: 438.1
No RP, Predicted Max < 50 % of Allowable Cw - No
No value > Allowable Cw
Monitoring required
NO WQS
Bromodichloromethane
C
0.95 WS(Qavg)
µg'L
25 5
20.70000
16.697
Lale
_
RP shown apply Monthly Monitoring with Limit
llowable Cw
55786 RPA, rpa
Page 2 of 2 8/10/2020

Permit No. NC0055786
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, µg/l
(Dissolved)
Chronic FW, µg/1
(Dissolved)
Acute SW, µg/1
(Dissolved)
Chronic SW, µg/l
(Dissolved)
Arsenic
340
150
69
36
Beryllium
65
6.5
---
---
Cadmium
Calculation
Calculation
40
8.8
Chromium III
Calculation
Calculation
---
---
Chromium VI
16
11
1100
50
Copper
Calculation
Calculation
4.8
3.1
Lead
Calculation
Calculation
210
8.1
Nickel
Calculation
Calculation
74
8.2
Silver
Calculation
0.06
1.9
0.1
Zinc
Calculation
Calculation
90
81
Table 1 Notes:
FW= Freshwater, SW= Saltwater
Calculation = Hardness dependent standard
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/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/I
Cadmium, Acute
WER* 11.136672-[ln hardness](0.041838)} eA10.9151 [In hardness]-3.1485}
Cadmium, Acute Trout waters
WER* {1.136672-[ln hardness](0.041838)} of 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]-1.7001
Copper, Chronic
WER*0.960 e^{0.8545[In hardness]-1.7021
Lead, Acute
WER*{1.46203-[ln hardness](0.145712)1 • of 1.273[ln hardness]-1.4601
Lead, Chronic
WER* {1.46203-[ln hardness](0.145712)1 • of 1.273[ln hardness]-4.705}
Nickel, Acute
WER*0.998 e^{0.8460[ln hardness]+2.255}
Nickel, Chronic
WER*0.997 e-10.8460[ln hardness]+0.0584}
Page 1 of 4

Permit No. NCO055786
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]+0.8841
Zinc, Chronic
WER*0.986 e-10.8473[ln hardness]+0.8841
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, 7Q10 (the spreadsheet automatically calculates
the 1 Q 10 using the formula 1 Q 10 = 0.843 (s7Q 10, cfs) 0.993
• 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.
Page 2 of 4

Permit No. NCO055786
The overall hardness value used in the water quality calculations is calculated as follows:
Combined Hardness (chronic)
_ (Permitted Flow, cfs *Avg. Effluent Hardness, mg/L) + (s7Q10, cfs *Avg. Upstream Hardness, mg/L)
(Permitted Flow, cfs + s7Q10, cfs)
The Combined Hardness for acute is the same but the calculation uses the 1Q10 flow.
3. The permit writer converts the numeric standard for each metal of concern to a total recoverable
metal, using the EPA Default Partition Coefficients (DPCs) or site -specific translators, if any
have been developed using federally approved methodology.
EPA default partition coefficients or the "Fraction Dissolved" converts the value for
dissolved metal at laboratory conditions to total recoverable metal at in -stream
ambient conditions. This factor is calculated using the linear partition coefficients
found in The Metals Translator: Guidance for Calculating a Total Recoverable
Permit Limit from a Dissolved Criterion (EPA 823-B-96-007, June 1996) and the
equation:
_Cdiss - I
Ctotal I + f [Kpo] [ss(i+a)] [10 6]
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.
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 (le. silver), the
dissolved numeric standard for each metal of concern is divided by the EPA conversion factor to
obtain a Total Recoverable Metal at ambient conditions. This method presumes that the metal is
dissolved to the same extent as it was during EPA's criteria development for metals. For more
information on conversion factors see the June, 1996 EPA Translator Guidance Document.
5. The RPA spreadsheet uses a mass balance equation to determine the total allowable concentration
(permit limits) for each pollutant using the following equation:
Ca = (s7Q10 + Qw) (Cwgs) - (s7Q10) (Cb)
Qw
Where: Ca = allowable effluent concentration (µg/L or mg/L)
Cwqs = NC Water Quality Standard or federal criteria (µg/L or mg/L)
Cb = background concentration: assume zero for all toxicants except NH3* (µg/L or mg/L)
Qw = permitted effluent flow (cfs, match s7Q10)
s7Q10 = summer low flow used to protect aquatic life from chronic toxicity and human
health through the consumption of water, fish, and shellfish from noncarcinogens (cfs)
* Discussions are on -going with EPA on how best to address background concentrations
Flows other than s7Q10 may be incorporated as applicable:
IQ10 = used in the equation to protect aquatic life from acute toxicity
Page 3 of 4

Permit No. NC0055786
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 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)
[Total as, CaCO3 or (Ca+Mg)]
61.67
Average from May 2019 to
February 2020 samples
Average Upstream Hardness (mg/L)
[Total as, CaCO3 or (Ca+Mg)]
46.5
Average from February 2020 to
July 2020 samples
7Q 10 summer (cfs)
6.7
NPDES Files
1Q10 (cfs)
5.57
Calculated in RPA
Permitted Flow (MGD)
6.5
NPDES Files
Date: 8/10/2020
Permit Writer: Nick Coco
Page 4 of 4

NH3/TRC WLA Calculations
Facility: Lexington Regional WWTP
PermitNo. NC0055786
Prepared By: Nick Coco
Enter Design Flow (MGD): 6.5
Enter s7Q10 (cfs): 6.7
Enter w7Q10 (cfs): 15
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
6.7
s7Q10 (CFS)
6.7
DESIGN FLOW (MGD)
6.5
DESIGN FLOW (MGD)
6.5
DESIGN FLOW (CFS)
10.075
DESIGN FLOW (CFS)
10.075
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
60.06
IWC (%)
60.06
Allowable Conc. (ug/1)
28
Allowable Conc. (mg/1)
1.5
Consistent with current permit limit.
Maintain limit.
Less stringent than current permit limit. Maintain
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
15
Monthly Average Limit:
2001100-
DESIGN FLOW (MGD)
6.5
(If DF >331; Monitor)
DESIGN FLOW (CFS)
10.075
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
1.67
Upstream Bkgd (mg/1)
0.22
IWC (%)
40.18
Allowable Conc. (mg/1)
4.2
Less stringent than current permit limit. Maintain
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/l, 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)

NCO055786 Lexington Regional WWTP
BOD monthly removal
rate
Month
RR (%)
Month
RR (%)
January-16
99.50
July-18
99.56
February-16
99.45
August-18
99.56
March-16
99.47
September-18
99.70
April-16
99.48
October-18
99.58
May-16
99.50
November-18
99.09
June-16
99.54
December-18
99.06
July-16
99.54
January-19
99.67
August-16
99.52
February-19
99.61
September-16
99.55
March-19
98.86
October-16
99.52
April-19
99.31
November-16
99.55
May-19
99.40
December-16
99.47
June-19
99.39
January-17
99.43
July-19
99.54
February-17
99.50
August-19
99.25
March-17
99.60
September-19
99.05
April-17
99.29
October-19
98.72
May-17
99.23
November-19
98.77
June-17
99.21
December-19
99.19
July-17
99.46
January-20
99.44
August-17
99.51
February-20
99.08
September-17
99.49
March-20
99.39
October-17
99.44
April-20
98.55
November-17
99.59
May-20
98.22
December-17
99.51
June-20
January-18
99.53
July-20
February-18
99.73
August-20
March-18
99.67
September-20
April-18
99.68
October-20
May-18
99.60
November-20
June-18
99.33
December-20
Overall BOD removal
rate
99.38
8/10/2020
TSS
monthly
removal rate
Month
RR (%)
Month
RR (%)
January-16
99.29
July-18
99.54
February-16
99.20
August-18
99.21
March-16
99.36
September-18
99.29
April-16
98.99
October-18
98.97
May-16
98.97
November-18
98.39
June-16
98.74
December-18
96.82
July-16
98.90
January-19
99.12
August-16
98.84
February-19
98.86
September-16
98.54
March-19
98.50
October-16
98.74
April-19
99.40
November-16
98.76
May-19
99.62
December-16
99.19
June-19
99.56
January-17
98.46
July-19
99.73
February-17
98.49
August-19
99.18
March-17
99.75
September-19
99.34
April-17
99.49
October-19
99.05
May-17
99.78
November-19
98.78
June-17
99.59
December-19
99.06
July-17
99.62
January-20
99.52
August-17
99.67
February-20
99.37
September-17
99.72
March-20
99.53
October-17
99.67
April-20
99.48
November-17
99.55
May-20
99.07
December-17
99.65
June-20
January-18
99.63
July-20
February-18
99.72
August-20
March-18
99.78
September-20
April-18
99.59
October-20
May-18
99.63
November-20
June-18
99.44
December-20
Overall TSSD removal rate
99.21

8/10/20 WQS = 12 ng/L
Facility Name
Lexington Regional WWTP/NC0055786
/Permit No.
Total Mercury 1631E PQL = 0.5 ng/L
Date Modifier Data Entry Value
MERCURY WQBEL/TBEL EVALUATION V:2013-6
No Limit Required
MMP Required
7Q10s = 6.700 cfs WQBEL = 19.98 ng/L
Permitted Flow = 6.500 47 ng/L
1/5/16
3.9
3.9
1/19/16
2.7
2.7
2/2/16
2.7
2.7
6/7/16
<
1
0.5
8/3/16
1.1
1.1
11/8/16
2.6
2.6
2.3 ng/L
- Annual Average for 2016
2/7/17
<
1
0.5
5/2/17
<
1
0.5
8/1/17
1.4
1.4
11/8/17
<
1
0.5
0.7 ng/L
- Annual Average for 2017
2/8/18
2.9
2.9
3/7/18
2.8
2.8
4/10/18
<
1
0.5
5/1/18
<
1
0.5
6/5/18
<
1
0.5
7/10/18
<
1
0.5
8/7/18
1.5
1.5
9/11/18
1.1
1.1
10/9/18
<
1
0.5
11/6/18
2.3
2.3
12/4/18
<
1
0.5
1.2 ng/L
- Annual Average for 2018
1/8/19
1.8
1.8
5/7/19
1.1
1.1
8/6/19
1.1
1.1
11/5/19
<
0.2
0.5
11/22/19
2.9
2.9
1.5 ng/L
- Annual Average for 2019
2/4/20
<
1
0.5
0.5 ng/L
- Annual Average for 2020

Lexington Regional WWTP/NC0055786
Mercury Data Statistics (Method 1631E)
2016
2017
2018
2019
# of Samples
6
4
11
5
Annual Average, ng/L
2.3
0.7
1.2
1.48
Maximum Value, ng/L
3.90
1.40
2.90
2.9
TBEL, ng/L
47
WQBEL, ng/L
20.0
2020
0.5
0.5

MONITORING REPORT(MR) VIOLATIONS for:
Report Date:
07/30/2C Page
1 of 5
Permit:
NCO055786
MRS Betweel 7 - 2015 and 7 - 2020
Region:
%
Violation Category:%
Program Category: NPDES
VVW
Facility Name: %
Param Name%
County:
%
Subbasin:%
Violation Action:
Major Minor:
%
PERMIT: NCO055786
FACILITY: City of Lexington -Lexington Regional WWTP
COUNTY: Davidson
REGION: Winston-Salem
Limit Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED
%
REPORT
OUTFALL
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
06 -2018
001
Effluent
BOD, 5-Day (20 Deg. C) -
06/30/18
5 X week
mg/I
5
5.01
0.2
Monthly Average
No Action, BPJ
Concentration
Exceeded
10-2019
001
Effluent
BOD, 5-Day (20 Deg. C) -
10/31/19
5 X week
mg/I
5
5.04
0.9
Monthly Average
No Action, BPJ
Concentration
Exceeded
04 -2020
001
Effluent
BOD, 5-Day (20 Deg. C) -
04/18/20
5 X week
mg/I
7.5
8.34
11.2
Weekly Average
None
Concentration
Exceeded
04 -2020
001
Effluent
BOD, 5-Day (20 Deg. C) -
04/30/20
5 X week
mg/I
5
6.32
26.4
Monthly Average
None
Concentration
Exceeded
05 -2020
001
Effluent
BOD, 5-Day (20 Deg. C) -
05/31/20
5 X week
mg/I
5
5.25
5.0
Monthly Average
None
Concentration
Exceeded
03 -2017
001
Effluent
Chlorine, Total Residual
03/29/17
5 X week
ug/I
28
34
21.4
Daily Maximum
No Action, BPJ
Exceeded
04 -2017
001
Effluent
Chlorine, Total Residual
04/03/17
5 X week
ug/I
28
49
75
Daily Maximum
No Action, BPJ
Exceeded
04 -2017
001
Effluent
Chlorine, Total Residual
04/04/17
5 X week
ug/I
28
31
10.7
Daily Maximum
No Action, BPJ
Exceeded
04-2017
001
Effluent
Chlorine, Total Residual
04/06/17
5 X week
ug/I
28
57
103.6
Daily Maximum
Proceed to NOV
Exceeded
04 -2017
001
Effluent
Chlorine, Total Residual
04/10/17
5 X week
ug/I
28
42
50
Daily Maximum
No Action, BPJ
Exceeded
04-2017
001
Effluent
Chlorine, Total Residual
04/11/17
5 X week
ug/I
28
40
42.9
Daily Maximum
No Action, BPJ
Exceeded
04 -2017
001
Effluent
Chlorine, Total Residual
04/12/17
5 X week
ug/I
28
32
14.3
Daily Maximum
No Action, BPJ
Exceeded
04 -2017
001
Effluent
Chlorine, Total Residual
04/24/17
5 X week
ug/I
28
29
3.6
Daily Maximum
No Action, BPJ
Exceeded
04-2017
001
Effluent
Chlorine, Total Residual
04/25/17
5 X week
ug/I
28
94
235.7
Daily Maximum
Proceed to NOV
Exceeded
04-2017
001
Effluent
Chlorine, Total Residual
04/26/17
5 X week
ug/I
28
66
135.7
Daily Maximum
Proceed to NOV
Exceeded
06 -2017
001
Effluent
Chlorine, Total Residual
06/06/17
5 X week
ug/I
28
31
10.7
Daily Maximum
No Action, BPJ
Exceeded

MONITORING REPORT(MR) VIOLATIONS for:
Report Date:
07/30/2C Page
2 of 5
Permit:
NCO055786
MRS Betweel 7
- 2015 and 7 - 2020
Region:
%
Violation Category:%
Program Category: NPDES
VVW
Facility Name: %
Param Name%
County:
%
Subbasin:%
Violation Action:
Major Minor:
%
PERMIT: NCO055786
FACILITY: City of Lexington -Lexington Regional WWTP
COUNTY: Davidson
REGION: Winston-Salem
Limit Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED
%
REPORT
OUTFALL
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
06-2017
001
Effluent
Chlorine, Total Residual
06/19/17
5 X week
ug/I
28
70.5
151.8
Daily Maximum
Proceed to NOV
Exceeded
06 -2017
001
Effluent
Chlorine, Total Residual
06/20/17
5 X week
ug/I
28
41
46.4
Daily Maximum
No Action, BPJ
Exceeded
06 -2017
001
Effluent
Chlorine, Total Residual
06/21/17
5 X week
ug/I
28
34
21.4
Daily Maximum
No Action, BPJ
Exceeded
06 -2017
001
Effluent
Chlorine, Total Residual
06/22/17
5 X week
ug/I
28
36.5
30.4
Daily Maximum
No Action, BPJ
Exceeded
09 -2017
001
Effluent
Chlorine, Total Residual
09/05/17
5 X week
ug/I
28
30.5
8.9
Daily Maximum
No Action, BPJ
Exceeded
09 -2017
001
Effluent
Chlorine, Total Residual
09/26/17
5 X week
ug/I
28
33.5
19.6
Daily Maximum
No Action, BPJ
Exceeded
04 -2018
001
Effluent
Chlorine, Total Residual
04/23/18
5 X week
ug/I
28
32
14.3
Daily Maximum
No Action, BPJ
Exceeded
05 -2018
001
Effluent
Chlorine, Total Residual
05/23/18
5 X week
ug/I
28
34
21.4
Daily Maximum
No Action, BPJ
Exceeded
06 -2018
001
Effluent
Chlorine, Total Residual
06/08/18
5 X week
ug/I
28
32
14.3
Daily Maximum
No Action, BPJ
Exceeded
06 -2018
001
Effluent
Chlorine, Total Residual
06/12/18
5 X week
ug/I
28
33
17.9
Daily Maximum
No Action, BPJ
Exceeded
06 -2018
001
Effluent
Chlorine, Total Residual
06/13/18
5 X week
ug/I
28
32
14.3
Daily Maximum
No Action, BPJ
Exceeded
06 -2018
001
Effluent
Chlorine, Total Residual
06/26/18
5 X week
ug/I
28
37
32.1
Daily Maximum
No Action, BPJ
Exceeded
10 -2018
001
Effluent
Chlorine, Total Residual
10/10/18
5 X week
ug/I
28
29
3.6
Daily Maximum
No Action, BPJ
Exceeded
10-2018
001
Effluent
Chlorine, Total Residual
10/11/18
5 X week
ug/I
28
31
10.7
Daily Maximum
No Action, BPJ
Exceeded
10 -2018
001
Effluent
Chlorine, Total Residual
10/19/18
5 X week
ug/I
28
33
17.9
Daily Maximum
No Action, BPJ
Exceeded
12 -2018
001
Effluent
Chlorine, Total Residual
12/19/18
5 X week
ug/I
28
30
7.1
Daily Maximum
No Action, BPJ
Exceeded

MONITORING REPORT(MR) VIOLATIONS for:
Report Date:
07/30/2C Page
3 of 5
Permit:
NCO055786
MRS Betweel 7 - 2015 and 7 - 2020
Region:
%
Violation Category:%
Program Category: NPDES
VVW
Facility Name: %
Param Name%
County:
%
Subbasin:%
Violation Action:
Major Minor:
%
PERMIT: NCO055786
FACILITY: City of Lexington -Lexington Regional WWTP
COUNTY: Davidson
REGION: Winston-Salem
Limit Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED
%
REPORT
OUTFALL
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT
VALUE
Over
VIOLATION TYPE
VIOLATION ACTION
06 -2019
001
Effluent
Chlorine, Total Residual
06/18/19
5 X week
ug/I
28
30
7.1
Daily Maximum
No Action, BPJ
Exceeded
07 -2019
001
Effluent
Chlorine, Total Residual
07/16/19
5 X week
ug/I
28
30
7.1
Daily Maximum
No Action, BPJ
Exceeded
08 -2019
001
Effluent
Chlorine, Total Residual
08/07/19
5 X week
ug/I
28
30
7.1
Daily Maximum
No Action, BPJ
Exceeded
08 -2019
001
Effluent
Chlorine, Total Residual
08/19/19
5 X week
ug/I
28
30
7.1
Daily Maximum
No Action, BPJ
Exceeded
11 -2019
001
Effluent
Chlorine, Total Residual
11/12/19
5 X week
ug/I
28
90
221.4
Daily Maximum
Proceed to NOV
Exceeded
11 -2019
001
Effluent
Chlorine, Total Residual
11/13/19
5 X week
ug/I
28
31
10.7
Daily Maximum
No Action, BPJ
Exceeded
02-2018
001
Effluent
Coliform, Fecal MF, MFC
02/10/18
5 X week
#/100ml
400
5,540.23
1,285.1
Weekly Geometric Mean
Proceed to NOV
Broth, 44.5 C
Exceeded
06 -2017
001
Effluent
Nitrogen, Ammonia Total (as
06/17/17
5 X week
mg/I
3
5.51
83.8
Weekly Average
Proceed to NOV
N) - Concentration
Exceeded
06 -2017
001
Effluent
Nitrogen, Ammonia Total (as
06/24/17
5 X week
mg/I
3
6.04
101.3
Weekly Average
Proceed to NOV
N) - Concentration
Exceeded
06 -2017
001
Effluent
Nitrogen, Ammonia Total (as
06/30/17
5 X week
mg/I
1
3.81
281.0
Monthly Average
Proceed to NOV
N) - Concentration
Exceeded
07 -2017
001
Effluent
Nitrogen, Ammonia Total (as
07/01/17
5 X week
mg/I
3
3.85
28.4
Weekly Average
No Action, BPJ
N) - Concentration
Exceeded
06 -2019
001
Effluent
Nitrogen, Ammonia Total (as
06/29/19
5 X week
mg/I
3
3.04
1.2
Weekly Average
Proceed to NOD
N) - Concentration
Exceeded
06 -2019
001
Effluent
Nitrogen, Ammonia Total (as
06/30/19
5 X week
mg/I
1
1.99
99.1
Monthly Average
Proceed to NOD
N) - Concentration
Exceeded
07 -2019
001
Effluent
Nitrogen, Ammonia Total (as
07/31/19
5 X week
mg/I
1
1.01
0.7
Monthly Average
No Action, BPJ
N) - Concentration
Exceeded
09-2019
001
Effluent
Nitrogen, Ammonia Total (as
09/14/19
5 X week
mg/I
3
3.11
3.7
Weekly Average
Proceed to NOV
N) - Concentration
Exceeded
09 -2019
001
Effluent
Nitrogen, Ammonia Total (as
09/30/19
5 X week
mg/I
1
1.12
11.5
Monthly Average
Proceed to NOV
N) - Concentration
Exceeded

MONITORING REPORT(MR) VIOLATIONS for:
Report Date:
07/30/2C Page
4 of 5
Permit:
NCO055786
MRS Betweel 7 - 2015 and 7 - 2020
Region:
%
Violation
Category:%
Program Category: NPDES
VVW
Facility Name: %
Param Name%
County:
%
Subbasin:%
Violation Action:
Major Minor:
%
PERMIT: NCO055786
FACILITY: City of Lexington -Lexington Regional WWTP
COUNTY: Davidson
REGION: Winston-Salem
Limit Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED %
REPORT
OUTFALL
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT VALUE Over
VIOLATION TYPE
VIOLATION ACTION
04-2020
001
Effluent
Nitrogen, Ammonia Total (as
04/11/20
5 X week
mg/I
3 4.05 35.1
Weekly Average
None
N) - Concentration
Exceeded
04-2020
001
Effluent
Nitrogen, Ammonia Total (as
04/30/20
5 X week
mg/I
1 1.69 69.0
Monthly Average
None
N) - Concentration
Exceeded
01 -2019
001
Effluent
pH
01/24/19
5 X week
su
9 10.12 12.4
Daily Maximum
Proceed to NOD
Exceeded
Monitoring Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED %
REPORT
OUTFALL
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, Facility
parameters]
Reporting Error
12-2019
001
Effluent
Annual Pollutant Scan [126
12/31/19
Annually
yes=1 no=0
Frequency Violation
None
parameters]
03-2018
001
Effluent
BOD, 5-Day (20 Deg. C) -
03/31/18
5 X week
mg/I
Frequency Violation
No Action, Facility
Concentration
Reporting Error
06-2016
001
Effluent
Bromod ichloromethane,
06/30/16
Quarterly
ug/I
Frequency Violation
Proceed to NOD
effluent
03-2020
001
Effluent
Bromod ichloromethane,
03/31/20
Quarterly
ug/I
Frequency Violation
No Action, Facility
effluent
Reporting Error
03-2018
001
Effluent
Chlorine, Total Residual
03/31/18
5 X week
ug/I
Frequency Violation
No Action, Facility
Reporting Error
05 -2018
001
Effluent
Chlorine, Total Residual
05/05/18
5 X week
ug/I
Frequency Violation
No Action, BPJ
12 -2018
001
Effluent
Chlorine, Total Residual
12/15/18
5 X week
ug/I
Frequency Violation
No Action, BPJ
12-2015
001
Effluent
Coliform, Fecal MF, MFC
12/26/15
5 X week
#/100ml
Frequency Violation
No Action, BPJ
Broth, 44.5 C
02-2018
001
Effluent
Coliform, Fecal MF, MFC
02/10/18
5 X week
#/100ml
Frequency Violation
No Action, BPJ
Broth, 44.5 C
03-2018
001
Effluent
Coliform, Fecal MF, MFC
03/31/18
5 X week
#/100ml
Frequency Violation
No Action, Facility
Broth, 44.5 C
Reporting Error
05-2018
001
Effluent
Coliform, Fecal MF, MFC
05/05/18
5 X week
#/100ml
Frequency Violation
No Action, BPJ
Broth, 44.5 C

MONITORING REPORT(MR) VIOLATIONS for:
Permit: NCO055786 MRS Betweel 7 - 2015 and 7 - 2020 Region: %
Facility Name: % Param Name% County: %
Major Minor: %
Report Date: 07/30/2C Page 5 of 5
Violation Category:% Program Category: NPDES WW
Subbasin:% Violation Action:
PERMIT: NCO055786 FACILITY: City of Lexington -Lexington Regional WWTP COUNTY: Davidson REGION: Winston-Salem
Monitoring Violation
MONITORING VIOLATION UNIT OF CALCULATED %
REPORT OUTFALL LOCATION PARAMETER DATE FREQUENCY MEASURE LIMIT VALUE Over VIOLATION TYPE VIOLATION ACTION
09-2018
001
Effluent
Coliform, Fecal MF, MFC
09/08/18
5 X week
#/100ml
Frequency Violation
No Action, Facility
Broth, 44.5 C
Reporting Error
12-2018
001
Effluent
Coliform, Fecal MF, MFC
12/15/18
5 X week
#/100ml
Frequency Violation
No Action, BPJ
Broth, 44.5 C
12 -2016
001
Effluent
Conductivity
12/24/16
5 X week
umhos/cm
Frequency Violation
No Action, BPJ
12 -2016
001
Effluent
Conductivity
12/31/16
5 X week
umhos/cm
Frequency Violation
No Action, BPJ
06 -2017
001
Effluent
Conductivity
06/03/17
5 X week
umhos/cm
Frequency Violation
No Action, BPJ
03-2018
001
Effluent
Conductivity
03/31/18
5 X week
umhos/cm
Frequency Violation
No Action, Facility
Reporting Error
07-2018
001
Effluent
Conductivity
07/07/18
5 X week
umhos/cm
Frequency Violation
No Action, Facility
Reporting Error
12 -2018
001
Effluent
Conductivity
12/15/18
5 X week
umhos/cm
Frequency Violation
No Action, BPJ
02 -2019
001
Effluent
Conductivity
02/02/19
5 X week
umhos/cm
Frequency Violation
No Action, BPJ
03-2018
001
Effluent
Nitrogen, Ammonia Total (as
03/31/18
5 X week
mg/I
Frequency Violation
No Action, Facility
N) - Concentration
Reporting Error
08 -2018
001
Effluent
Nitrogen, Ammonia Total (as
08/04/18
5 X week
mg/I
Frequency Violation
No Action, BIMS
N) - Concentration
Calculation Error
03-2018
001
Effluent
Solids, Total Suspended -
03/31/18
5 X week
mg/I
Frequency Violation
No Action, Facility
Concentration
Reporting Error
Reporting Violation
MONITORING
VIOLATION
UNIT OF
CALCULATED %
REPORT
OUTFALL
LOCATION
PARAMETER
DATE
FREQUENCY
MEASURE
LIMIT VALUE Over VIOLATION TYPE
VIOLATION ACTION
07-2019
001
Effluent
Phosphorus, Total (as P) -
07/31/19
See Permit
lb/season
Parameter reported with
No Action, Invalid
Quantity Seasonal
invalid Unit of Measure
Permit

United States Environmental Protection Agency
Form Approved.
EPA Washington, D.C. 20460
OMB No. 2040-0057
Water Compliance Inspection Report
Approval expires 8-31-98
Section A: National Data System Coding (i.e., PCS)
Transaction Code NPDES yr/mo/day Inspection Type Inspector Fac Type
1 IN 1 2 15 1 3 I NC0055786 I11 121 19/07/31 I17 18 n 19 L G j 201
2111111�-1111111111111111111111111111111111111 f6
Inspection
Work Days Facility Self -Monitoring Evaluation Rating B1 CA ---------------------- Reserved -------------------
67
I 71 I I 72 L n, � 73 LLI74 71 I I I I I I I80
70 Iu ty LJ
Section B: Facility Data
Name and Location of Facility Inspected (For Industrial Users discharging to POTW, also include
Entry Time/Date
Permit Effective Date
POTW name and NPDES permit Number)
09:30AM 19/07/31
16/02/01
Lexington Regional WWTP
500 Glendale Rd
Exit Time/Date
Permit Expiration Date
Lexington NC 27292
12:OOPM 19/07/31
19/04/30
Name(s) of Onsite Representative(s)/Titles(s)/Phone and Fax Number(s)
Other Facility Data
Name, Address of Responsible Official/Title/Phone and Fax Number
Contacted
Joseph Shaffer,28 W Center St Lexington NC 27292/Utility Plant
Supervisor/336-357-5090/3363577369 No
Section C: Areas Evaluated During Inspection (Check only those areas evaluated)
Permit 0 Flow Measurement Operations & Maintenar Records/Reports
Self -Monitoring Progran 0 Sludge Handling Dispos Facility Site Review Effluent/Receiving Wate
Section D: Summary of Finding/Comments (Attach additional sheets of narrative and checklists as necessary)
(See attachment summary)
Name(s) and Signature(s) of Inspector(s) Agency/Office/Phone and Fax Numbers Date
Gary Hudson DWR/Division of Water Quality/336-776-9694/
Signature of Management Q A Reviewer Agency/Office/Phone and Fax Numbers Date
EPA Form 3560-3 (Rev 9-94) Previous editions are obsolete.
Page#

NPDES yr/mo/day Inspection Type
31 NCO055786 I11 121 19/07/31 117 18 ICI
Section D: Summary of Finding/Comments (Attach additional sheets of narrative and checklists as necessary)
Page#

Permit: NCO055786 Owner - Facility:
Inspection Date: 07/31/2019 Inspection Type:
Lexington Regional WWTP
Compliance Evaluation
Permit
Yes
No
NA
NE
(If the present permit expires in 6 months or less). Has the permittee submitted a new 0
❑
❑
❑
application?
Is the facility as described in the permit?
0
❑
❑
❑
# Are there any special conditions for the permit?
❑
0
❑
❑
Is access to the plant site restricted to the general public?
0
❑
❑
❑
Is the inspector granted access to all areas for inspection?
0
❑
❑
❑
Comment: .
Record Keeping
Yes
No
NA
NE
Are records kept and maintained as required by the permit?
0
❑
❑
❑
Is all required information readily available, complete and current?
0
❑
❑
❑
Are all records maintained for 3 years (lab. reg. required 5 years)?
0
❑
❑
❑
Are analytical results consistent with data reported on DMRs?
0
❑
❑
❑
Is the chain -of -custody complete?
0
❑
❑
❑
Dates, times and location of sampling
Name of individual performing the sampling
Results of analysis and calibration
Dates of analysis
Name of person performing analyses
Transported COCs
Are DMRs complete: do they include all permit parameters?
❑
❑
❑
Has the facility submitted its annual compliance report to users and DWQ?
❑
❑
❑
(If the facility is = or > 5 MGD permitted flow) Do they operate 24/7 with a certified operatc
❑
❑
❑
on each shift?
Is the ORC visitation log available and current?
❑
❑
❑
Is the ORC certified at grade equal to or higher than the facility classification?
❑
❑
❑
Is the backup operator certified at one grade less or greater than the facility classification'
❑
❑
❑
Is a copy of the current NPDES permit available on site?
0
❑
❑
❑
Facility has copy of previous year's Annual Report on file for review?
0
❑
❑
❑
Comment: .
Influent Sampling Yes No NA NE
# Is composite sampling flow proportional? 0 ❑ ❑ ❑
Is sample collected above side streams? 0 ❑ ❑ ❑
Page# 3

Permit: NCO055786 Owner - Facility: Lexington Regional WWTP
Inspection Date: 07/31/2019 Inspection Type: Compliance Evaluation
Influent Sampling Yes No NA NE
Is proper volume collected?
0
❑
❑
❑
Is the tubing clean?
0
❑
❑
❑
# Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees
0
❑
❑
❑
Celsius)?
Is sampling performed according to the permit?
0
❑
❑
❑
Comment: .
Effluent Sampling
Yes
No
NA
NE
Is composite sampling flow proportional?
0
❑
❑
❑
Is sample collected below all treatment units?
0
❑
❑
❑
Is proper volume collected?
0
❑
❑
❑
Is the tubing clean?
0
❑
❑
❑
# Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees
0
❑
❑
❑
Celsius)?
Is the facility sampling performed as required by the permit (frequency, sampling type
0
❑
❑
❑
representative)?
Comment: .
Flow Measurement - Effluent
Yes
No
NA
NE
# Is flow meter used for reporting?
0
❑
❑
❑
Is flow meter calibrated annually?
0
❑
❑
❑
Is the flow meter operational?
0
❑
❑
❑
(If units are separated) Does the chart recorder match the flow meter?
❑
❑
0
❑
Comment: .
Operations & Maintenance Yes No NA NE
Is the plant generally clean with acceptable housekeeping? 0 ❑ ❑ ❑
Does the facility analyze process control parameters, for ex: MLSS, MCRT, Settleable ❑ ❑ ❑
Solids, pH, DO, Sludge Judge, and other that are applicable?
Comment: .
Secondary Clarifier
Yes
No
NA
NE
Is the clarifier free of black and odorous wastewater?
0
❑
❑
❑
Is the site free of excessive buildup of solids in center well of circular clarifier?
0
❑
❑
❑
Page# 4

Permit: NCO055786
Inspection Date: 07/31/2019
Secondary Clarifier
Are weirs level?
Is the site free of weir blockage?
Is the site free of evidence of short-circuiting?
Is scum removal adequate?
Is the site free of excessive floating sludge?
Is the drive unit operational?
Owner - Facility: Lexington Regional WWTP
Inspection Type: Compliance Evaluation
Is the return rate acceptable (low turbulence)?
Is the overflow clear of excessive solids/pin floc?
Is the sludge blanket level acceptable? (Approximately'/4 of the sidewall depth)
Comment: .
Aeration Basins
Mode of operation
Type of aeration system
Is the basin free of dead spots?
Are surface aerators and mixers operational?
Are the diffusers operational?
Is the foam the proper color for the treatment process?
Does the foam cover less than 25% of the basin's surface?
Is the DO level acceptable?
Is the DO level acceptable?(1.0 to 3.0 mg/1)
Comment: .
Bar Screens
Type of bar screen
a.Manual
b.Mechanical
Are the bars adequately screening debris?
Is the screen free of excessive debris?
Is disposal of screening in compliance?
Is the unit in good condition?
Comment: .
Yes
No
NA
NE
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
•
❑
❑
❑
•
❑
❑
❑
•
❑
❑
❑
■
❑
❑
❑
Yes No NA NE
Plug flow
Diffused
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
■
❑
❑
❑
Yes No NA NE
■ ❑ ❑ ❑
■ ❑ ❑ ❑
■ ❑ ❑ ❑
■ ❑ ❑ ❑
Page# 5

Permit: NC0055786
Inspection Date: 07/31/2019
Owner - Facility: Lexington Regional WWTP
Inspection Type: Compliance Evaluation
Pump Station - Influent
Yes
No
NA
NE
Is the pump wet well free of bypass lines or structures?
0
❑
❑
❑
Is the wet well free of excessive grease?
0
❑
❑
❑
Are all pumps present?
0
❑
❑
❑
Are all pumps operable?
0
❑
❑
❑
Are float controls operable?
0
❑
❑
❑
Is SCADA telemetry available and operational?
❑
❑
0
❑
Is audible and visual alarm available and operational?
❑
❑
❑
Comment: .
Grit Removal
Yes
No
NA
NE
Type of grit removal
a.Manual
❑
b.Mechanical
Is the grit free of excessive organic matter?
0
❑
❑
❑
Is the grit free of excessive odor?
0
❑
❑
❑
# Is disposal of grit in compliance?
0
❑
❑
❑
Comment: .
Disinfection -Liquid
Yes
No
NA
NE
Is there adequate reserve supply of disinfectant?
0
❑
❑
❑
(Sodium Hypochlorite) Is pump feed system operational?
0
❑
❑
❑
Is bulk storage tank containment area adequate? (free of leaks/open drains)
0
❑
❑
❑
Is the level of chlorine residual acceptable?
0
❑
❑
❑
Is the contact chamber free of growth, or sludge buildup?
0
❑
❑
❑
Is there chlorine residual prior to de -chlorination?
0
❑
❑
❑
Comment: .
De -chlorination
Yes No
NA
NE
Type of system ?
Liquid
Is the feed ratio proportional to chlorine amount (1 to 1)?
0 ❑
❑
❑
Is storage appropriate for cylinders?
0 ❑
❑
❑
# Is de -chlorination substance stored away from chlorine containers?
0 ❑
❑
❑
Comment: .
Page# 6

Permit: NC0055786
Inspection Date: 07/31/2019
De -chlorination
Are the tablets the proper size and type?
Are tablet de -chlorinators operational?
Number of tubes in use?
Comment: .
Owner - Facility: Lexington Regional WWTP
Inspection Type: Compliance Evaluation
Effluent Pipe
Is right of way to the outfall properly maintained?
Are the receiving water free of foam other than trace amounts and other debris?
If effluent (diffuser pipes are required) are they operating properly?
Comment: .
Yes
No
NA
NE
❑
❑
■
❑
❑
❑
■
❑
Yes
No
NA
NE
■
❑
❑
❑
■
❑
❑
❑
❑
❑
■
❑
Page# 7

2018 NC Category 5 Assessments "303(d) List" Final �.DE
Iw a:r 4 1 :. :: pw
Yadkin -Pee Dee River Basin Lower Yadkin Subbasin 03040103 awnrAK
—�
12-118.5a I Abbotts Creek Arm of High Rock Lake
From source at 1-85 to NC 47
Classification WS-V,B Length or Area 4 Units FW Miles Previous AU Number
Assessment Criteria Status
Reason for Rating
Parameter of Inter
Category
Exceeding Criteria
Fish Consumption Advisory
PCB Fish Tissue Advisory (Advisory, FC, NC)
F
Exceeding Criteria
> 10% and >90 conf
Chlorophyll a (40 µg/I, AL, NC)
12-118.5b Abbotts Creek Arm of High Rock Lake
From NC 47 to Davidson County SR 2294
Classification WS-V,B Length or Area 6 Units FW Miles Previous AU Number
12-119-7-4b
4ssessment Criteria Status Reason for Rating Parameter of Interest Category
Exceeding Criteria Chlorophyll a (40 µg/I, AL, NC) 0
Exceeding Criteria T�dity (25 NTU, AL, FW acres & SW) I5
(Hamby Creek
From North Hamby Creek to Rich Fork
Classification C Length or Area 6 Units FW Miles Previous AU Number 12-119-7-4
ImessOrnt Criteria Status ReTson for Rating rameter of Interest Category
Exceeding Criteria > 10% and >90 conf Copper (7 jig/I, AL, FW)
12-119-7-3 1 (Hunts Fork
From source to Rich Fork
Classification C Length or Area L 7 Units FW Miles Previous AU Number
Assessment Criteria Status
Reason for Rating
Parameter of Inter
Category
Exceeding Criteria
Fair
Benthos (Nar, AL, FW)
6/3/2019 2018 NC Category 5 Assessments "303(d) List" Approved by EPA May 22,2019 Page 244 of 262

Whole Effluent Toxicity Testing and Self Monitoring Summary
Lenoir -Lake Rhodhiss WTP
NCO044164/001 County:
Caldwell
Region: ARO
Basin:
CTB32
Jan Apr Jul Oct
SOC JOC:
Ceri7dPF Begin:
6/1/2011 Chr Monit: 90%-Ann
NonComp:
7Q10:
PF:
IWC:
Freq: A
J
F M
A
M
J J
A
5 O
N D
2016 Fail
- -
Pass
-
- -
-
- -
- -
2017 -
- -
-
Pass
- -
-
- -
- -
2018 -
- -
-
Pass
- -
-
- -
- -
Lexington Regional WWTP
NCO055786/001 County:
Davidson
Region: WSRO
Basin:
YAD07
Feb May Aug Nov
SOC JOC:
Ceri7dPF Begin:
2/1/2016 Chr lim: 60%
NonComp:
SINGLE
70.10: 6.7
PF: 6.5
IWC:
60.06 Freq: Q
J
F M
A
M
J J
A
5 O
N D
2016 -
Pass -
-
Pass
- -
Pass
- -
Pass -
2017 -
Pass -
-
Pass
- -
Pass
- -
Pass -
2018 -
Pass -
-
Pass
- -
H
- -
Pass -
2019 -
Pass -
-
Pass
- -
Pass
- -
Pass -
2020 -
Pass -
-
Pass
- -
-
- -
- -
Lexington WTP #1 & #2 NCO028037 County: Davidson
Ceri7dPF Begin: 4/1/2015 Chr Monit: 21% NonComp:
J F M A M
2016 - Pass - - Pass
2017 - Pass - - Pass
2018 - Pass - - Pass
2019 - Pass - - Pass
2020 - Pass - - Pass
Lincoln County WTP
NCO084573/001 County:
Lincoln
Fthd24PF
Begin:
4/1/2017 Acu Fthd 24PF Monit:
NonComp:
J
F M
A M
2016
-
- Fail
- -
2017
-
- Fail
- -
2018
-
- Pass
- -
2019
-
- Pass
- -
2020
-
- Pass
- -
Lincolnton WTP
NCO085588/001 County:
Lincoln
Ceri7dPF
Begin:
6/1/2017 Chr Monit: 4.5%
NonComp:
J
F M
A M
2016
-
- Pass
- -
2017
-
- Pass
- -
2018
-
- Pass
- -
2019
-
- Pass
- -
Region:
WSRO
Basin:
YAD07
Feb May Aug Nov
70.10: 2.9
PF: 0.467 IWC:
20 Freq: Q
J J
A
5 O
Pass
-
Pass
Pass
Pass
Region:
MRO
Basin:
CTB32
Mar Jun Sep Dec
7Q10:
PF:
IWC:
Freq: Q
J J
A
5 O
Fail -
-
Fail -
Pass -
-
Pass -
Pass -
-
Pass -
Fail -
-
Pass -
Pass
-
Region:
MRO
Basin:
CTB35
Mar Jun Sep Dec
7Q10: 13
PF:
IWC:
1.41 Freq: Q
J J
A
5 O
Pass -
-
Pass -
Pass -
-
Pass -
Pass -
-
Pass -
Pass -
-
Pass -
SOC JOC:
N
Pass
Pass
Pass
Pass
SOC JOC:
N
SOC JOC:
N
D
D
Fail
Pass
Pass
Pass
D
Pass
Pass
Pass
Pass
Legend: P= Fathead minnow (Pimphales promelas), H=No Flow (facility is active), s = Split test between Certified Labs Page 68 of 122

NPDES/Aquifer Protection Permitting Unit Pretreatment Information Request Form
PERMIT WRITER COMPLETES THIS PART:
Check all that
PERMIT WRITERS -AFTER you get this form back
apply
frorn PERCS:
Notify 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.
Date of Request
8/6/2020
municipal renewal
X
Requestor
Nicholas Coco
new industries
Facility Name
Lexington Regional WWTP
WWTP expansion
Permit Number
NCO055786
Speculative limits
Region
Winston Salem
stream reclass.
Basin
Yadkin -Pee Dee
outfall relocation
7Q10 change
otherl
other
check applicable PERCS staff:
Other Comments to PERCS:
Facility is rated 6.5 MGD wtih 5 SIUs, including 4 CIUs listed in its
application.
BRD, CPF, CTB, FRB, TAR
CHO, HIW, LTN, LUM, NES, NEW, ROA, YAD
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
ti 3) facility has SIUs and DWQ approved Pretreatment Program (list "DEV" if program still under development)
y 3a) Full Program with LTMP
3b) Modified Program with STMP
4) additional conditions regarding Pretreatment attached or listed below
Flow, MGD
Permitted
Actual
Time period for Actual
STMP time frame:
Industrial
0.116
0.0308
2018 - 2019
Most recent:
Uncontrollable
n/a
3.273
2018 - 2019
Next Cycle:
a
a
N
o
a
Parameter of
Concern (POC)
Check List
POC due to
NPDES/ Non-
Disch Permit
Limit
Required by EPA"
Required
by 503
Sludge""
POC due
to SIU"""
POTW POC
(Explain
below)""""
STMP
Effluent
Freq
LTMP
Effluent
Freq
Q = Quarterly
M = Monthly
BOD
ti
ti
Q
TSS
ti
ti
Q
NH3
I
Q
Arsenic
Q
Cadmium
1
Q
Chromium
1
Q
Copper
ti
Q
Cyanide
ti
Q
Is all data on DMRs?
Lead
1
Q
YES
1
Mercury
ti
Q
NO (attach data)
Molybdenum
Q
Nickel
1
Q
Silver
ti
Q
Selenium
Q
Zinc
1
1
Q
Is data in spreadsheet'?
% solids
ti
Q
YES email to writer
Total Phosphorus
ti
Q
NO
IN'
NO2 Q
TKN Q
NO3 I I Q
Q
"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
Comments to Permit W riter (ex., explanation of any POCs: info you have on IU related investigations into NPDES problems):
Quarterly sampling was performed for all Long Term Monitoring Plan pollutants of concern each year and monthly
sampling was performed from February 2018 through January 2019 at the LRWWTP
PERC NPDES_Pretreatment.request.form.may20l6
Revised: July 24, 2007