NC0089630_Fact Sheet_20241112

Fact Sheet
NPDES Permit No. NCO089630
Permit Writer/Email Contact:Nick Coco,[e-mail]
Date: September 25, 2024
Division/Branch:NC Division of Water Resources/NPDES Municipal Permitting
Fact Sheet Template: Version 09Jan2017
Permitting Action:
® Renewal
❑ Renewal with Expansion
❑ New Discharge
❑ Modification(Fact Sheet should be tailored to mod request)
Note: A complete application should include the following:
• For New Dischargers,EPA Form 2A or 2D requirements,Engineering Alternatives Analysis,Fee
• For Existing Dischargers (POTW),EPA Form 2A, 3 effluent pollutant scans,4 2nd species WET
tests.
• For Existing Dischargers (Non-POTW),EPA Form 2C with correct analytical requirements based
on industry category.
Complete applicable sections below. If not applicable, enter NA.
1. Basic Facility Information
Facility Information
Applicant/Facility Name: Charlotte Water/Joe C. Stowe Regional Water Resource Recovery Facility
(WRRF)
Applicant Address: 5100 Brookshire Blvd., Charlotte,NC 28216
Facility Address: 1200 Belmeade Drive, Charlotte,NC 28214
Permitted Flow: 15.0 MGD&25.0 MGD
Facility Type/Waste: MAJOR Municipal; Domestic and Industrial*
Facility Class: Grade IV Biological Water Pollution Control System
Pretreatment Program(Y/N) Y,LTMP upon completion of construction and acceptance of SIUs
County: Mecklenburg
Region Mooresville
*Charlotte Water has a pretreatment program and intends to receive industrial flow at this facility after
construction.
Briefly describe the proposed permitting action and facility background: Charlotte Water has applied for
an NPDES permit renewal at 15.0 MGD with maintenance of a 25.0 MGD future expansion flow tier for
the Joe C. Stowe Regional WRRF. As part of their renewal application, Charlotte Water requested that
the facility address be updated. This change has been made in the cover page of the permit.
The Stowe Regional Water Resource Recovery Facility(WRRF) is currently under construction and is
anticipated to be completed at the earliest in the first quarter of 2027 and the latest by the third quarter of
2027 pending weather or other unforeseen circumstances. Charlotte has entered into agreements with the
Cities of Mount Holly and Belmont for the treatment of their waste flows. The agreements and the EIS for
the new facility specify that the two cities must connect their collection systems to the new plant and
close their treatment plants. Mount Holly will achieve this prior to the Stowe Regional WRRF startup.
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Design of a new Mount Holly pump station and force main is underway. The system will carry Mount
Holly's flows to the existing Long Creek Storage and Pump Station and, initially,to the McAlpine Creek
WWTP. When the Stowe Regional WRRF is completed,the flows will be redirected to the new regional
facility.A similar connection for Belmont is also planned. If it is completed before the new facility is
operational,Belmont's flows will be pumped to the Paw Creek Lift Station and from there to Charlotte's
McAlpine Creek WWTP until the new facility starts up.
The Phase 2 expansion to 25.0 MGD will be triggered either by growth in the Phase 1 service areas or by
the need to transfer flows from Charlotte's Irwin or McAlpine Creek WWTPs, since the facilities have the
capability to transfer flow to and from one another. In the latter case, flows would likely be routed from
the Paw Creek Lift Station to the expanded Stowe Regional WRRF. Treated domestic and industrial
wastewater will be discharged via Outfall 001 into the Catawba River(Lake Wylie), a class WS-IV, CA
waterbody in the Catawba River Basin.
Sludge disposal: Biosolids residuals will be temporarily held on-site and then conveyed to the McAlpine
Creek WRRF for centralized dewatering and class B biosolids production. Biosolids residuals will be
permitted,managed, and disposed under a contract with Synagro. Land application and land filling are the
means for ultimate use of the residuals. This is managed under permit WQ0000057 (ND0080900 in South
Carolina).
2. Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receiving Stream(s): Outfall 001 —Catawba River(Lake Wylie)
Stream Segment: l l-(117)
Stream Classification: WS-IV, CA
Drainage Area(mi): below Mountain Island Dam: 150
(above dam: 1,860)
Summer 7Q10(cfs) 95 (control release)
Winter 7Q10(cfs): 95 (control release)
30Q2 (cfs): 95 (control release)
Average Flow(cfs): 320
IWC (%effluent): 19.7 @ 15.0 MGD and 29.0 @ 25.0 MGD
2022 303(d) listed/parameter: Yes; listed as exceeding criteria for PCB Fish Tissue Advisory
Subject to TMDL/parameter: Yes- State wide Mercury TMDL implementation
Basin/HUC: Catawba River/03050101
3. Effluent Data Summary
As this new facility has yet to complete construction,no effluent data are available. However,the
following limitations, from the current permit have been maintained:
EFFLUENT LIMITATIONS
PARAMETER BASIS
Parameter Code Monthly Weekly Daily
Average Average Maximum
Flow 50050 15.0/25.0 15A NCAC 02B .0505
Total Monthly Flow(MG) 82220 Monitor and Report Used to calculate monthly mass loads
CBOD5 (Summer)' 80082 4.2 mg/L 6.3 mg/L BPJ,equivalent to 5.0 mg/L BOD5
C130135 (Winter)' 800821 8.3 mg/L 12.5 mg/L BPJ,equivalent to 10.0 mg/L 130135
Total Suspended Solids' C05301 30 mg/L 45 mg/L 15A NCAC 02B.0406,40 CFR Part 133
N113-N C06101 1.0 mg/L 3.0 mg/L 15A NCAC 02B .0505
Page 2 of 13

EFFLUENT LIMITATIONS
PARAMETER BASIS
Parameter Code Monthly Weekly Daily
Average Average Maximum
Dissolved Oxygen 00300 Daily avg.>6.0 mg/L 15A NCAC 02B .0505
Fecal Coliform(geo.mean) 31616 200/100 mL 400/100 mL I 15A NCAC 02B .0505
Total Residual Chlorine 50060 1 28 µg/L 15A NCAC 02B .0505
pH 00400 >6.0 and<9.0 standard units 15A NCAC 02B .0200& .0406
Temperature(°C) 00100 Monitor and Report 15A NCAC 02B .0505
TKN(mg/L) 00625 Monitor and Report Component species of TN
NO3-N+NO2-N(mg/L) 00630 Monitor and Report Component species of TN
Total Nitrogen(mg/L) C0600 Monitor and Report
2 QM600 Monitor and Report(lb/mo) Lake Wylie Nutrient TMDL(1995)
TN Load QS600 Seasonal Limits2 &
QS600
Total Phosphorus(mg/L) C0665 Monitor and Report DWR policy for setting nutrient limits
for affected Lake Wylie dischargers
TP Load 2 QM665 Monitor and Report(lb/mo)
QY665 Annual Limit2
Total Hardness(mg/L as CaCO3) Monitor and Report Necessary to evaluate hardness-
00900 dependent metals
Chronic Toxicity TGP3B P/F at 19.7%/29.0% 15A NCAC 02B .0208
Effluent Pollutant Scan NC01 Monitor and Report Per 40 CFR 122.210)(4)
1. And 85%removal.
2. Please see Other TMDL/Nutrient Management Strategy Considerations for additional information regarding TN and TP load limits.
The 2013 speculative limits included a D.O. limit of 7.0 mg/L. The limit was based on the March 2008
Water Quality Modeling Report,which used an effluent concentration of 7.0 mg/L as input to the model,
based on performance of the McDowell Creek WWTP. The City later determined that this was
unnecessarily conservative and retained HDR to re-evaluate the impact of discharging at a lower D.O.
limit. The analysis showed that, at a flow of 15.0 MGD with a D.O.limit of 6.0 mg/L,the instream D.O.
would be reduced by a maximum of 0.2 mg/L and would not drop below the 5.0 mg/L standard. The
Division's Modeling staff found the analysis to be acceptable, and a limit of 6.0 mg/L was applied at the
15.0 MGD flow tier.
However,the limit at 25 MGD remained at 7.0 mg/L. Charlotte Water employed HDR to conduct
additional modeling to evaluate whether 7.0 mg/L DO was necessary at the 25.0 MGD flow tier. As a
result,HDR submitted results from a QUAL2KW to the Division,who approved the results on March 12,
2024.As part of this renewal, Charlotte Water is requesting that the DO limit at 25.0 MGD be dropped
from 7.0 mg/L to 6.0 mg/L,per the approved model results. As such,the limits have been revised.
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 proposed discharge location is across the river from the existing Mount Holly WWTP
and approximately '/z mile upstream of the U.S.National Whitewater Center. The Mount Holly WWTP
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(NC0021156)was last issued in April 2024. Per that renewal's fact sheet, "The current permit requires
instream monitoring for Dissolved Oxygen(DO),Temperature, Conductivity, and Hardness(upstream
only). Hardness is monitored for calculation of hardness-dependent metal stream standards and is treated
in Section 6.4 Reasonable Potential Analysis below. Instream monitoring locations are at the NC Hwy 27
bridge(upstream) and just below the NC Hwy 29/NC Hwy 74 bridge (downstream).
"Permittee-submitted data from May 2019 through October 2023 reviewed and checked against
applicable stream standards as well as for effluent impacts,the latter via statistical testing of downstream
averages against the upstream average of each parameter using t-test with the level of significance(p-
value) set at 0.05. The data are summarized in Table 2 and discussed below.
"Table 1. Instream Data Summary: averages with ranges in parentheses.
*Statistically significantly different from Upstream.
Table 1. Current Nutrient Allocations
Parameter,units Upstream Downstream Standard
DO,mg/L Avg=8.24 Avg= 8.30 5.0
(4.60— 14.80) (4.42— 16.40)
Temperature, °C Avg=23.4 Avg=23.9 32.0
(7.8—32.0) (7.5—33.8)
Conductivity, µmhos/cm Avg=62.5 Avg=59.9 NA
(45.6— 165) (44.6—96.5)
"Dissolved Oxygen (DO)—DO is in the permit as a parameter of concern for aquatic life. The average
DO at both stations was above the stream standard of 5.0 mg/L. On no occasion during the period
reviewed did DO drop below 4.0 mg/L at either station.No statistically significant difference was found
between upstream and downstream.
"Temperature—Temperature is in the permit as a parameter of concern for aquatic life. The summer
maximum upstream is at the 32°C standard for lower piedmont and coastal plain waters, and the
downstream maximum is above it.No statistically significant differences were found between the
upstream and downstream stations. Seven instances of downstream temperatures were greater than the
2.8°C increase standard(15A NCAC 02B .0208). Concurrent effluent temperatures appear lower on
average;thus,the effluent does not appear to be impacting the receiving stream.
"Conductivity—Conductivity is in the permit as an indicator of industrial sources. The Town has an
active pretreatment program with three SIUs.A statistically significant difference was found between the
upstream and downstream stations with downstream average reporting lower. Effluent conductivity
monitoring is not required in the permit, and based on this difference, is likely not impacting the stream.
Nevertheless,because the facility is receiving industrial waste via a pretreatment program, effluent
conductivity monitoring will be added to the permit at daily frequency in accordance with 15A NCAC
02B .0500.
"Fecal Coliform—Fecal Coliform is not in the current permit as it was removed in 2002 based on
permitting guidance and instream data review,wherein similar counts between upstream and downstream
samples showed little or no correlation to the discharge. Effluent coliform count from May 2019 through
October 2023 were mostly below limits with a geometric mean of 21/100 mL and four reported
exceedances (see Section 5 Compliance Summary below). Because the receiving stream is neither a
Class B nor impaired for Fecal Coliform, instream Fecal Coliform is not required and was not added to
the permit."
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The current instream monitoring requirements for the Stowe Regional WRRF include DO,temperature,
conductivity,pH,TN,TP and upstream hardness. Instream samples shall be grab samples taken 3/week
(June-September)and 1/week(October-May). Upstream is defined as above the discharge at the NC
Highway 27 bridge. Downstream is defined as below the discharge at I-85. Reporting of TKN and
NO2+NO3 has been added to the permit at the same frequency as TN for calculation of TN.
Is this facility a member of a Monitoring Coalition with waived instream monitoring(YIN):NO
Name of Monitoring Coalition: NA
5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): NA
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): NA
Summarize the results from the most recent compliance inspection: NA
6. Water Quality-Based Effluent Limitations (WQBELs)
Dilution and Mixin Zg ones
In accordance with 15A NCAC 2B.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 15A NCAC 2B.0204(b): NA
Oxygen-Consuming Waste Limitations
Limitations for oxygen-consuming waste(e.g.,BOD) are generally based on water quality modeling to
ensure protection of the instream dissolved oxygen(DO)water quality standard. Secondary TBEL limits
(e.g., BOD=30 mg/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: The current limits
for CBOD5 and NH3-N and were based on best professional judgment for the protection of instream
dissolved oxygen through the assignment of tertiary treatment limits. The CBOD5 limits of 4.2 mg/L
(summer)and 8.3 mg/L(winter) are effectively equivalent to BOD5 limits of 5 mg/L(summer) and 10
mg/L(winter). The year-round 1.0 mg/L NH3-N limit was based on instream protection for ammonia
toxicity.
The March 2008 Water Quality Modeling Report,prepared by Black&Veatch,verified that the
discharge would not cause a violation of water quality standards at these limits. This was further
corroborated with the 2023 QUAL2KW model performed by HDR.No changes were proposed based on
recent modeling.
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.
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Limitations for Total Residual Chlorine(TRC) are based on the NC water quality standard for protection
of aquatic life(17 ug/1)and capped at 28 ug/l(acute impacts). Due to analytical issues,all TRC values
reported below 50 ug/l are considered compliant with their permit limit.
Describe any proposed changes to ammonia and/or TRC limits for this permit renewal: The current
permit limits for TRC are based on toxicity. The limits have been reviewed in the attached WLA and have
been found to be protective.No changes are proposed. Please note that TRC monitoring is only required
in the event that chlorine is used at the plant and as part of the regular Effluent Pollutant Scans.
Refer to the Oxygen Consuming Waste section for the description of the model and rationale behind the
ammonia limits. The ammonia limits at each flow tier have been reviewed in the attached WLA and have
been found to be protective of the stream.
Reasonable Potential Analysis(RPA)for Toxicants
If applicable, conduct RPA analysis and complete information below.
The need for toxicant limits is based upon a demonstration of reasonable potential to exceed water quality
standards, a statistical evaluation that is conducted during every permit renewal utilizing the most recent
effluent data for each outfall. The RPA is conducted in accordance with 40 CFR 122.44(d) (i). The NC
RPA procedure utilizes the following: 1)95% Confidence Level/95%Probability; 2)assumption of zero
background; 3)use of/z detection limit for"less than"values; and 4) streamflows used for dilution
consideration based on 15A NCAC 2B.0206. Effective April 6,2016,NC began implementation of
dissolved metals criteria in the RPA process in accordance with guidance titled NPDES Implementation of
Instream Dissolved Metals Standards, dated June 10,2016.
As this new facility has yet to complete construction,no effluent data are available and no reasonable
potential analysis could be conducted.
Per 40 CFR 122.210)(4), for POTWs applying prior to commencement of discharge,priority pollutant
testing data shall be submitted no later than 24 months after the commencement of discharge.As such,
three effluent pollutant scans must be performed in the first 24 months of discharge from this facility.
Toxicity Testing Limitations
Permit limits and monitoring requirements for Whole Effluent Toxicity(WET)have been established in
accordance with Division guidance(per WET Memo, 8/2/1999). Per WET guidance, all NPDES permits
issued to Major facilities or any facility discharging"complex"wastewater(contains anything other than
domestic waste)will contain appropriate WET limits and monitoring requirements,with several
exceptions. The State has received prior EPA approval to use an Alternative WET Test Procedure in
NPDES permits,using single concentration screening tests,with multiple dilution follow-up upon a test
failure.
Describe proposed toxicity test requirement: This is a Major POTW, and a chronic WET limit at 19.7%
effluent @ 15.0 MGD and 29.0%effluent @ 25.0 MGD will continue on a quarterly frequency. WET
testing requirements are based on the Instream Waste Concentration.
Per 40 CFR 122.210)(5), for POTWs applying prior to commencement of discharge, WET testing data
shall be submitted no later than 24 months after the commencement of discharge. As the facility is
required to conduct quarterly chronic toxicity testing,this requirement is mostly satisfied. However, it is
also required that the facility conduct the toxicity testing on multiple species. As such,the 2nd species
toxicity tests shall be conducted once per quarter in a single 12-month period(four samples)during either
the first or second year following commencement of discharge from the facility;the sample for each 2nd
species test shall coincide with the primary species quarterly samples collected.
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Mercury Statewide TMDL Evaluation
There is a statewide TMDL for mercury approved by EPA in 2012. The TMDL target was to comply
with EPA's mercury fish tissue criteria(0.3 mg/kg) for human health protection. The TMDL established a
wasteload allocation for point sources of 37 kg/year(81 lb/year), and is applicable to municipals and
industrial facilities with known mercury discharges. Given the small contribution of mercury from point
sources(-2%of total load),the TMDL emphasizes mercury minimization plans (MMPs)for point source
control. Municipal facilities>2 MGD and discharging quantifiable levels of mercury(>1 ng/1)will
receive an MMP requirement. Industrials are evaluated on a case-by-case basis, depending if mercury is a
pollutant of concern. Effluent limits may also be added if annual average effluent concentrations exceed
the WQBEL value(based on the NC WQS of 12 ng/1) and/or if any individual value exceeds a TBEL
value of 47 ng/l.
As this new facility has yet to complete construction,no effluent data are available and mercury TMDL
evaluation could not be conducted. Because this is a new facility, it has yet to be determined how mercury
should be regulated. In addition,the Dental Amalgam Rule (40 CFR Part 441)promulgated by the EPA
on June 14, 2017, should result in some reduction of mercury to the plant. The permit's Effluent Pollutant
Scan condition already requires annual monitoring of mercury for the first three years of discharge,which
will provide data as the facility begins discharging.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: This portion of the Lake Wylie watershed is subject to the 1995 Nutrients TMDL. The
TMDL assigned limits to the existing major dischargers in the watershed, including the Cities of Mount
Holly,Belmont, and others.
In 2013, Charlotte purchased TN and TP allocation for a new regional plant from the Clariant Corporation
(NC0004375). (It also purchased land from the company,near the Long Creek Pump Station, on which to
construct the new facility.)
Charlotte recognized that it would need additional allocations for the new discharge. It entered into
agreements with Mount Holly and Belmont that will eventually result in the transfer of their nutrient
allocations to Charlotte. First,while the Stowe Regional WRRF is designed and constructed, Charlotte
will transfer its allocations to the other cities. The transfers ensure that Mount Holly and Belmont can
meet their nutrients limits until they connect to the regional plant,without having to unnecessarily
upgrade their plants in the interim period. When the Stowe Regional WRRF is operational,Mount Holly's
and Belmont's collection systems will connect to the new plant, close their treatment facilities, and
transfer their allocations and Charlotte's allocation back to Charlotte for the regional discharge.
All three permits will be issued at the same to enact the first transfers.
The three dischargers' initial allocations are shown in Table 1. These are the basis for the nutrient
allocations and limits that follow.
Table 1. Current Nutrient Allocations
Summer TN Winter TN Annual TP
Facility
(lb/day) (lb/S) (lb/day) (lb/W) (lb/day) (lb/year)
Mount Holly WWTP 300.2 64,251 50.0 18,265
Belmont WWTP 350.3 74,960 - 58.4 21,309
Joe Stowe Jr.Regional WRRF 287.0 61,418 287.0 43.3,- 36.0 13,140
NOTE: Summer is defined as April-October(214 days)and winter is November-March(151 days).
Page 7 of 13

The permit establishes nutrient allocations and limits for five scenarios in the development of the Stowe
wastewater system:
• Stowe Regional plant under construction:no allocations,no discharge; Charlotte's allocations are
transferred to Mount Holly and Belmont plants(Table 2)
• Mount Holly connects to Stowe Regional WRRF first(Table 3)
• Belmont connects first(Table 4)
• Mount Holly and Belmont are both connected- 15.0 MGD (Table 5)
• Mount Holly and Belmont are both connected-25.0 MGD (Table 5)
The initial allocations and limits for each facility(Scenario 1) are shown in Table 2.
Table 2. Interim Nutrient Allocations/Limits-Scenario 1
Summer TN Winter TN Annual TP
Facility
(lb/day) (lb/S) (lb/day) (lb/w) (lb/day) (lb/year)
Mount Holly WWTP 523.2 111,973 823.5 124,345 86.0 31,405
Belmont WWTP 414.3 88,656 764.6 115,449 58.4 21,309
Joe Stowe Jr.Regional WRRF 0 0 0 0 0 0
Total 937.5 j 200,629 1,588.1 j 239,794 144.4 52,713
Charlotte will have no allocations in this interim period, so the Stowe Regional WRRF will not be
allowed to discharge; however, it will be under construction at this time and will not yet have any need to
discharge.
Prior to connecting to Charlotte's system,Mount Holly and Belmont will each notify DWR and request
rescission of its permit. The Division will rescind the connecting city's permit upon connection and issue
an Authorization to Operate to Charlotte. The three permits are written so that the cities' allocations can
be transferred automatically and no modifications are necessary. The ATO triggers the transfer of
allocations to Charlotte and activation of the appropriate TN and TP limits.
The distributions for Scenarios 2 and 3 are shown in Tables 4 and 5.
Table 3. Nutrient Allocations/Limits-Scenario 2-Mount H ly Connection
Summer TN Winter TN Annual TP
Facility
(lb/day) (lb/S) (lb/day) (lb/W) (lb/day) (lb/year)
Mount Holly WWTP 0 0 0 0 0 0
Belmont WWTP 414.3 88,656 764.6 115,449 58.4 21,309
Joe Stowe Jr.Regional WRRF 523.2 111,973 823.5 124,345 86.0 31,405
Table 4. Nutrient Allocations/Limits-Scenario 3-Belmont Connection
Summer TN Winter TN Annual TP
Facility
(lb/day) (lb/S) (lb/day) (lb/R') (lb/day) (lb/year)
Mount Holly WWTP 523.2 111,973 823.5 124,345 86.0 31,405
Belmont WWTP 0 0 0 0 0 0
Joe Stowe Jr.Regional WRRF 414.3 88,656 764.6 115,449 58.4 21,309
Reserve Allocation at 15.0 MGD. Charlotte currently plans to build the Stowe Regional WRRF in two
phases: 15.0 MGD and,when needed, 25.0 MGD. When the plant first discharges, Charlotte will hold
allocations equivalent to 937.5 lb/day TN summer, 1,588 lb/day TN winter, and 144.4 lb/day TP.
In the 15.0 MGD phase,these allocations exceed the 6.0 mg/L TN and 1.0 mg/L TP standards established
in the TMDL, as well as the 12.0 mg/L value now set for winter TN. Therefore,the plant's nutrient limits
Page 8 of 13

will be held to the mass loads equivalent to the set concentrations at the 15.0 MGD design flow. The
remainder of each allocation will be held in reserve.
Once the plant expands to 25.0 MGD,the allocations will be equivalent to 4.5 mg/L TN summer, 7.6
mg/L TN winter, and 0.7 mg/L TP at the higher design flow. Thus,the reserve allocations can be restored,
and the plant will have the full benefit of its allocations.
The allocations and allowable limits for Scenarios 4 and 5 are shown in Table 6.
Table 5. Nutrient Allocations/Limits—Scenarios 4&5—Mount Holly and Belmont Connections
Summer TN Winter TN Annual TP
Phase
(mg/L) I (lb/day) (Ib/S) (mg/L) (lb/day) (lb/W) (mg/L) (lb/day) (lb/year)
Mount Holly WWTP 0 0 0 0 0 0
Belmont WWTP 0 0 0 0 0 0
Stowe Regional WRRF Holdings - 937.5 200,629 1,588 239,794 144.4 52,713
Phase 1:Limits @ 15.0 MGD 6.0 750.6 160,628 12.0 1,501 226,681 125.1 45,662
Phase I Reserve 186.9 40,001 - 86.8 13,113 19.3 7,052
Phase 2:Limits @ 25.0 MGD 4.5 937.5 200,629 7.6 1,588 239,794 0.69 144.4 52,713
Phase 2 Reserve 0 0 0 0 0 0
Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs: As required by Session
Law 2018-5, Senate Bill 99, Section 13.1(r), every applicant shall submit documentation of any additional
pollutants for which there are certified methods with the permit application if their discharge is
anticipated. The list of pollutants may be found in 40 CFR Part 136,which is incorporated by
reference. However, as this new facility has yet to complete construction,no effluent sampling could be
conducted and no chemical addendum is necessary.
If applicable, describe any special actions (HQW or ORW) this receiving stream and classification shall
comply with in order to protect the designated waterbody:NA
If applicable, describe any compliance schedules proposed for this permit renewal in accordance with
15A NCAC 2H.0107(c)(2)(B), 40CFR 122.47, and EPA May 2007 Memo:NA
If applicable, describe any water quality standards variances proposed in accordance with NCGS 143-
215.3(e) and 15A NCAC 2B.0226 for this permit renewal:NA
7. Technology-Based Effluent Limitations (TBELs)
Municipals
Are concentration limits in the permit at least as stringent as secondary treatment requirements (30 mg/1
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 CBOD51TSS 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
review in accordance with 15A NCAC 2B.0201. Each applicant for a new/expanding NPDES permit
must document an effort to consider non-discharge alternatives per 15A NCAC 2H.0105(c)(2). In all
cases, existing instream water uses and the level of water quality necessary to protect the existing use is
maintained and protected.
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If applicable, describe the results of the antidegradation review, including the Engineering Alternatives
Analysis (EAA) and any water quality modeling results:NA
9. Antibacksliding Review:
Sections 402(o)(2) and 303(d)(4)of the CWA and federal regulations at 40 CFR 122.44(l)prohibit
backsliding of effluent limitations in NPDES permits. These provisions require effluent limitations in a
reissued permit to be as stringent as those in the previous permit,with some exceptions where limitations
may be relaxed(e.g.,based on new information,increases in production may warrant less stringent TBEL
limits, or WQBELs may be less stringent based on updated RPA or dilution).
Are any effluent limitations less stringent than previous permit(YES/NO): NO
If YES, confirm that antibacksliding provisions are not violated:NA
10. Monitoring Requirements
Monitoring frequencies for NPDES permitting are established in accordance with the following
regulations and guidance: 1) State Regulation for Surface Water Monitoring, 15A NCAC 213.0500;2)
NPDES Guidance,Monitoring Frequency for Toxic Substances (7/15/2010 Memo); 3)NPDES Guidance,
Reduced Monitoring Frequencies for Facilities with Superior Compliance(10/22/2012 Memo); 4)Best
Professional Judgement(BPJ). Per US EPA(Interim Guidance, 1996),monitoring requirements are not
considered effluent limitations under Section 402(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.
To identify PFAS concentrations in waters across the State,monitoring requirements are to be
implemented in permits with pretreatment programs that discharge to or above WS waters.
As the Stowe Regional WRRF:
• will discharge to WS waters designated by the Division upon completion of construction and
activation of discharge,
• has a pretreatment program associated with it and will receive industrial wastewater,
• will be receiving wastewater from the City of Mount Holly and City of Belmont who receive
wastewater from industries recognized as potential sources of PFAS via an existing pretreatment
program and is required to monitor for PFAS per the 2024 permit,
monitoring of PFAS chemicals has been added to the permit,to be effective 6 months after
commencement of discharge. Currently, EPA Method 1633 is in its final form and not yet published in
the Federal Register as an approved methodology. Since an EPA method for sampling and analyzing
PFAS in wastewater is not currently available, influent and post-filtration PFAS monitoring has been
added to the permit at a quarterly frequency using the Method 1633.Upon evaluation of laboratory
availability and capability to perform the draft analytical method, it was determined that the sampling
may be conducted using the 3rd draft method 1633 or more recent. Sampling using the draft method shall
take effect the first full calendar quarter following 6 months after the commencement of discharge to
provide Charlotte Water time to select a laboratory, develop a contract, and begin collecting samples.
Effective 6 months after EPA has an approved wastewater method in 40 CFR136 published in the
Federal Register, Charlotte Water shall conduct effluent monitoring using the Final Method 1633 and is
no longer required to conduct influent and post-filtration monitoring.
In addition to monitoring at the wastewater management facility, Charlotte Water shall identify and
monitor SIUs suspected of discharging PFAS compounds, including the Cities of Mounty Holly and
Belmont as they plan to maintain their own pretreatment programs,upon receipt of industrial waste after
commencement of discharge by the Stowe Regional WRRF. For a detailed outline of the specific PFAS
Page 10 of 13

requirements, see Special Condition A.(10.)PFAS Monitoring Requirements. Depending on how
Charlotte Water intends to implement requirements of Special Condition A.(10.), it may be necessary for
Charlotte Water to revise the Inter-Jurisdictional Agreements made with the Cities of Mount Holly and
Belmont.
Similarly, as the facility will be receiving wastewater from the City of Mount Holly who receives
wastewater from industries recognized as potential sources of 1,4-dioxane via an existing pretreatment
program and is required to monitor for 1,4-dioxane per the 2024 permit, and as the facility will discharge
to WS waters designated by the Division upon completion of construction and activation of discharge,
quarterly monitoring for 1,4-dioxane has been added to the permit. After a 24-month sampling period,the
Permittee may request the Division conduct a review of submitted data for assessment and approval of a
1,4-dioxane monitoring frequency reduction from quarterly to 2/year.
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.
12.Summary of Proposed Permitting Actions:
Table 7. Current Permit Conditions and Proposed Changes Outfal1001
Parameter Current Permit Proposed Change Basis for Condition/Change
Flow MA 15.0 MGD with No change 15A NCAC 2B .0505
expansion flow tier 25.0
MGD
Total Monthly Monitor and Report No change For calculation of TN and TP loadings
Flow Monthly Same for both flow tiers.
CBOD5 Summer: No change WQBEL. BPJ, equivalent to 5.0 mg/L
MA 4.2 mg/1 (summer) and 10 mg/L(winter)BOD5,
WA 6.3 mg/1 supported by 2008 modeling report and
Winter: 2023 Qua12KW model,Monitoring—
MA 8.3 mg/1 15A NCAC 02B .0508
WA 12.5 mg/1 Same for both flow tiers.
Monitor and report Dail
NH3-N MA 1.0 mg/1 No change WQBEL. BPJ,supported by 2008
WA 3.0 mg/1 modeling report,2023 Qual2KW model
Monitor and report Daily and 2024 WLA review,Monitoring—
15A NCAC 02B .0508
Same for both flow tiers.
TSS MA 30.0 mg/1 No change TBEL. Secondary treatment standards/40
WA 45.0 mg/1 CFR 133 / 15A NCAC 2B .0406,
Monitor and report Daily Monitoring— 15A NCAC 02B .0508
Same for both flow tiers.
Fecal coliform MA 200/100ml No change WQBEL. State WQ standard, 15A
WA 400/100ml NCAC 2B .0200; Monitoring— 15A
Monitor and report Daily NCAC 02B .0508
Page 11 of 13

Same for both flow tiers.
DO >6.0 mg/l& 15.0 MGD >6.0 mg/l at both WQBEL. supported by 2008 modeling
>7.0 mg/1&25.0 MGD flow tiers report and 2023 Qual2KW model;
Monitor and report Daily Monitoring— 15A NCAC 02B .0508
Same for both flow tiers.
pH 6—9 SU No change WQBEL. State WQ standard, 15A
Monitor and report Daily NCAC 2B .0200; Monitoring— 15A
NCAC 02B .0508
Same for both flow tiers.
Conductivity No requirement Monitor and Monitoring— 15A NCAC 02B .0508;
report Daily facility will receive industrial waste.
Same for both flow tiers.
Temperature Monitor and report Daily No change Monitoring— 15A NCAC 02B .0508
Same for both flow tiers.
Total Residual DM 18 ug/L No change WQBEL. 2024 WLA review. Monitoring
Chlorine Monitor and report Daily — 15A NCAC 02B .0508
Same for both flow tiers.
Total Nitrogen Monitor and report Weekly No change Lake Wylie Nutrient TMDL(1995)
TKN Monitor and report Weekly No change For calculation of Total Nitrogen
NO3+NO2 Monitor and report Weekly No change For calculation of Total Nitrogen
Total Monitor and report Weekly No change Lake Wylie Nutrient TMDL(1995)
Phosphorus
TN Load Monitor and Report(lb/mo) No change Lake Wylie Nutrient TMDL(1995) &
Seasonal Limits DWR policy for setting nutrient limits
See Other TMDL/Nutrient for affected Lake Wylie dischargers
Management Strategy
Considerations for
information about future
allocations
TP Load Monitor and Report(lb/mo) No change Lake Wylie Nutrient TMDL(1995) &
Annual Limit DWR policy for setting nutrient limits
See Other TMDL/Nutrient for affected Lake Wylie dischargers
Management Strategy
Considerations for
information about future
allocations
Total Hardness Quarterly monitoring No change Hardness-dependent dissolved metals
Upstream and in Effluent water quality standards approved in
2016.
Same for both flow tiers.
See Special Evaluation of PFAS contribution:
PFAS No requirement Condition A.(10.) pretreatment facility; Discharge into WS
PFAS Monitoring waters&PT industries linked to PFAS
Requirements
Monitor and
1,4-Dioxane No requirement Report Quarterly; Receipt of industrial wastewater from
24-month Mount Holly
sam lin
Page 12 of 13

reassessment
option
Monitor instream for DO Add instream
Instream monitoring for New discharge; 15A NCAC 02B .0508,
Monitoring temperature, conductivity, TKN and Lake Wylie Nutrient TMDL(1995)
pH,TN, and TP NO2+NO3
Toxicity Test Chronic limit, 19.7% No change WQBEL. No toxics in toxic amounts.
effluent @ 15.0 MGD and 15A NCAC 213.0200 and 15A NCAC
29.0%effluent @ 25.0 213.0500
MGD
Effluent Three times per permit conducted within 40 CFR 122
Pollutant Scan cycle first 24 months of
discharge
Electronic Electronic Reporting No change In accordance with EPA Electronic
Reporting Special Condition Reporting Rule 2015.
MGD—Million gallons per day,MA- Monthly Average, WA—Weekly Average,DM—Daily Max
13. Public Notice Schedule:
Permit to Public Notice: xx/xx/xxxx
Per 15A NCAC 2H .0109 & .0111, The Division will receive comments for a period of 30 days following
the publication date of the public notice.Any request for a public hearing shall be submitted to the
Director within the 30 days comment period indicating the interest of the party filing such request and the
reasons why a hearing is warranted.
14. NPDES Division Contact
If you have any questions regarding any of the above information or on the attached permit,please
contact Nick Coco at(919) 707-3609 or via email at [e-mail].
15. Fact Sheet Addendum (if applicable):
Were there any changes made since the Draft Permit was public noticed(Yes/No):NO
If Yes, list changes and their basis below:NA
16. Fact Sheet Attachments (if applicable):
• NH3/TRC WLA Calculations
• March 2024 Modeling Approval Letter
• 2022 Integrated Report
Page 13 of 13

NORTH CAROLINA 2022 INTEGRATED REPORT
Upper Catawba Catawba River Basin
AU Name AU Number Classification AU LengthArea AU Units
AU ID Description
CATAWBA RIVER(Lake Wylie below elevation 570) 11-(117) WS-IV;CA 375.4 FW Acres
312 From Mountain Island Dam to Interstate Highway 85 Bridge at Belmont
2022 Water Quality Assessments
PARAMETER IR CATEGORY CRITERIA STATUS
Water Temperature (322C, AL, LP&CP) 1 Meeting Criteria
Dissolved Oxygen (4 mg/I, AL, FW) 1 Meeting Criteria
pH (6 su, AL, FW) 1 Meeting Criteria
pH (9.0, AL, FW) 1 Meeting Criteria
NO2+NO3-N (10 mg/I, WS, WS) 1 Meeting Criteria
Hardness (100 mg/L, WS, WS) 1 Meeting Criteria
Chlorophyll a (40 µg/l, AL, NC) 1 Meeting Criteria
Turbidity (25 NTU, AL, FW acres & SW) 1 Meeting Criteria
PCB Fish Tissue Advisory (Advisory, FC, NC) 5 Exceeding Criteria
Fecal Coliform (GM 200/400, REC, FW) 1 Meeting Criteria
Sulfate (250 mg/l, WS, WS) 3a Data Inconclusive
Chloride (230 mg/I, AL, FW) 3a Data Inconclusive
Flouride (1.8 mg/I, AL, FW) 3a Data Inconclusive
6/7/2022 NC 2022 INTEGRATED REPORT-Category 5 Approved by EPA 4/30/2022 Page 256 of 1346

DocuSign Envelope ID: FEC24750-C37A-48D8-9555-F6BF71B4BOE1
,mac STATE qt
yV y�
ROY COOPER � o
Governor
ELIZABETH S.BISER `
secretary
RICHARD E.ROGERS,JR. NORTH CAROLINA
Director Environmental Quality
March 12,2024
Ms.Nicole Bartlett P.E., Senior Project Manager
Charlotte Water
5100 Brookshire Blvd.
Charlotte,NC 28216
Subject: Review of Catawba River DO Modeling Report
Stowe Regional WRRF
NPDES Permit No.NCO089630
Mecklenburg County
Catawba River Basin
Dear Ms. Bartlett:
The Division of Water Resources (DWR)Modeling and Assessment Branch reviewed the modeling files and
report submitted on December 8,2023 by HDR, Inc on behalf of Charlotte Water. The purpose of this
modeling project was to evaluate the impact of changing the dissolved oxygen(DO)limit for Phase 11 of
Stowe Regional WWRF change from 7 mg/L to 6 mg/L. Although the original modeling plan was to use a
steady-state model QUAL2K, flow releases from the Mountain Island Dam approximately 4 miles upstream
of the discharge location were observed to be causing large diel fluctuations in streamflow. To account for the
hydrology of study area,the reported assessment was made using a dynamic version of the model
QUAL2KW.
The submitted calibration and scenario runs were reproduced and it was verified that they were consistent
with the modeling report.Model inputs for the scenario runs were examined to verify that the only inputs that
were changed were permitted DO concentration limits of the Stowe Regional WRRF from 7 mg/L to 6 mg/L.
Simulated stream DO was decreased to a varying degree as the result of changing the DO limit, and the
maximum DO decrease was 0.11 mg/L as reported. All simulated hourly stream DO values were greater than
4 mg/L with daily averages above 5 mg/L. The impact of DO limit change was mostly limited to the
immediate discharge location(reach 8). These findings appear reasonable and in support of the proposed
effluent DO limit change.
As a cautionary note,the submitted QUAL2KW model has several shortcomings and limitations that prevent
its application beyond this study's goal(testing the impact of effluent DO change for the Stowe WRRF):
• The river sampling data collected for this study indicate that vertical temperature and DO
stratification may start developing near downstream of the proposed Stowe WRRF outfall location
during the summer periods,likely due to the backwater effects from Lake Wylie. The observed
stratification became more pronounced in the downstream portions of the modeling domain. The
QUAL2KW is a one-dimensional model and limited in its ability to represent vertically stratified
waters.
• Surface water samples collected during the summer periods in the downstream areas show signs of
DO supersaturation, suggesting elevated algal activities, large diel DO swings and significant
sediment oxygen demand. Currently only factors affecting dissolved oxygen in the model are
North Carolina Department of Environmental Quality I Division of Water Resources
D 512 North Salisbury Street 1 1617 Mail Service Center I Raleigh,North Carolina 27699-1617
NCRTHCARCLINA
.P oamawao .un­W 919.707.9000

DocuSign Envelope ID:FEC24750-C37A-48D8-9555-F6BF7lB4BOE1
biological oxygen demand(BOD) degradation,nitrification and reaeration without algal processes
and sediment oxygen demand.
• Although hourly values of temperature and water quality variables are specified for the headwater,
meteorological inputs(e.g., atmospheric temperature)have no diel variation.As a result,diel
variation in simulated DO diminishes as the water moves downstream, and the model does not appear
to be doing well in reproducing the observed pattern of DO in the downstream portion of the modeled
domain.
Despite these shortcomings,the submitted model appears appropriate for assessing the impact of DO limit
change for the Stowe WRRF, considering that the impact is mostly limited to the immediate discharge
location in the relatively upstream area. The modeling results appear to support the proposed change in the
Stowe WRRF effluent DO limit from 7 mg/L to 6 mg/L at the discharge flow of 25 MGD. The modeling
results should be interpreted with care, considering the limitations outlined earlier. It is essential not to extend
their use beyond evaluating the impact of effluent dissolved oxygen(DO) changes for the Stowe WRRF.
To proceed with the NPDES permitting process, Charlotte Water can choose to either submit a modification
request package and corresponding fee at this time to the Municipal Permitting Branch OR include the
modification request in the permit renewal package and avoid a second fee.
Please let us know if you have any questions regarding these comments and recommendations and we will
schedule a meeting to discuss.
Respectfully,
Do'c'Iu,Siigne'Id byy:k A`, L ,WAA
C464531431644FE...
Michael Montebello
NPDES Program Branch Chief
ec: NPDES Files[Laserfiche]
Charlotte Water/Nicole Bartlett[[e-mail]]
HDR Inc./Barry Shearin[[e-mail]]
DWR/Pam Behm[[e-mail]];Kristin Litzenberger[[e-mail]];Nick Coco
[[e-mail]];Bongghi Hong[[e-mail]];Adugna Kebede[[e-mail]];Derek
Denard[[e-mail]]
Mooresville Regional Office/Andrew Pitner[andrew.pitner@ deq.nc.gov]
D � � North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh,North Carolina 27699-1611
NCarHCnaouNn 919.707.9000
Deo.k-m m D..Z�

EPA Identification Number NPDES Permit Number Facility Name Form Approved 03/05/19
110070666903 NCO089630 Joe C.Stowe,Jr.Regional WRRF OMB No.2040-0004
Form U.S.Environmental Protection Agency
2A V8jEPA Application for NPDES Permit to Discharge Wastewater
NPDES NEW AND EXISTING PUBLICLY OWNED TREATMENT WORKS
SECTION •N INFORMATION FOR i
1.1 Facility name
Joe C.Stowe,Jr.Regional Water Resources Recovery Facility
Mailing address(street or P.O.box)
5100 Brookshire BLVD.
City or town State ZIP code
o Charlotte NC 28216
EContact name(first and last) Title Phone number Email address
Joseph Lockler Operation Chief [phone] Joseph.Lockler@charlottenc.g,
Location address(street,route number,or other specific identifier) ❑ Same as mailing address
@ 1200 Belmeade Dr.
City or town State ZIP code
Charlotte NC 28214
1.2 Is this application for a facility that has yet to commence discharge?
0 Yes -* See instructions on data submission ❑ No
requirements for new dischargers.
1.3 Is applicant different from entity listed under Item 1.1 above?
0 Yes ❑ No SKIP to Item 1.4.
Applicant name
Charlotte Water
Applicant address(street or P.O. box)
5100 Brookshire BLVD.
E City or town State ZIP code
w
Charlotte NC 28216
Contact name(first and last) Title Phone number Email address
Q Joseph Lockler Operation Chief [phone] [e-mail]
a 1.4 Is the applicant the facility's owner,operator,or both?(Check only one response.)
❑ Owner ❑ Operator 0 Both
1.5 To which entity should the NPDES permitting authority send correspondence?(Check only one response.)
❑ Facility 0 Applicant ❑ Facility and applicant
(they are one and the same)
1.6 Indicate below any existing environmental permits. (Check all that apply and print or type the corresponding permit
number for each.
Existing Environmental Permits
a NPDES(discharges to surface RCRA hazardous waste UIC(underground injection
R ❑ ( 9 ❑ ( ) ❑ ( 9 1
water) control)
E NCO089630 N/A N/A
c
❑ PSD(air emissions) ❑ Nonattainment program(CAA) ❑ NESHAPs(CAA)
UJ
N/A N/A N/A
y ❑ Ocean dumping(MPRSA) ❑ Dredge or fill(CWA Section ❑ Other(specify)
w 404)
N/A N/A N/A
EPA Form 3510-2A(Revised 3-19) Pagel