NC0036269_Fact Sheet_20210929

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Fact Sheet
NPDES Permit No. NC0036269

Permit Writer/Email Contact Min Xiao, [e-mail]:
Date: December 9, 2020
Division/Branch: NC Division of Water Resources/NPDES Industrial Permitting Unit
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: Water and Sewer Authority of Cabarrus County/Rocky River Regional
WWTP
Applicant Address: 232 Davidson Highway, Concord, NC 28025
Facility Address: 6400 Breezy Lane, Concord, NC 28025
Permitted Flow: 26.5 MGD / 30 MGD / 34 MGD
Facility Type/Waste: Major Municipal; Domestic (67%) & Industrial (33%) Wastewater
Facility Class: Grade IV
Treatment Units: Bar Screens, primary clarifiers, first & second stage aeration,
intermediate & final clarifiers, chlorine disinfection, sludge
thickeners/conditioning/incinerator, standby generator
Pretreatment Program (Y/N) Y
County: Cabarrus
Region Mooresville

Briefly describe the proposed permitting action and facility background: Cabarrus County has applied
for an NPDES permit renewal at 26.5 MGD and 34 MGD for the Rocky River Regional WWTP in May
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2018. On 6/3/2021, WSACC submitted a request for an intermediate flow tier of 30 MGD to DWR. The
RRRWWTP triggered the 26.5 MGD flow tier limits during the last permit cycle. In 2020 - 2021, flows to
the facility increased more rapidly than in past years, partly due to growth and partly due to wet weather.
Therefore, WSACC anticipates the need to accommodate flows in the 26.5 - 30 MGD range sooner than
previously expected. Although WSACC still plans a longer-term expansion to 34 MGD, an intermediate
(30 MGD) flow tier would allow the facility to perform less extensive modifications sooner, and thereby
accommodate the increased flows while planning for the 34 MGD expansion continues. Since the NPDES
permitting unit is working on the second draft which addresses the proposed site-specific ammonia limits
and a compliance schedule for 26.5 MGD, the permit modification for the 30 MGD flow tier is combined
with this renewal.

The permittee submitted a request to USGS for updated low-flow characteristics for the Rocky River at
the discharge location on March 3, 2020. Provisional low-flow analyses completed for the 2000-2018
climatic years and the annual average discharge are as follows:
• Annual 7Q10 (7Q10 s) = 20.7 cfs (with 95% confidence intervals between 13.7 and 25.2 cfs)
• Annual 30Q2 = 44.5 cfs (with 95% confidence intervals between 37.6 and 52.3 cfs)
• Winter 7Q10 = 31.9 cfs (with 95% confidence intervals between 21.7 and 40.8 cfs)
• Annual 7Q2 = 32.9 cfs (with 95% confidence intervals between 27.5 and 38.5 cfs)
• Annual average discharge = 229 cfs (period of record 04/01/2000 through 03/09/2020
provisional)
Compared with existing summer and winter 7Q10 and average flow data, the updated numbers have
decreased. In the 1st draft permit, existing 7Q10 numbers were used for 26.5 MGD while updated 7Q10
numbers were used for 34 MGD. In the 2nd draft permit, the updated 7Q10 numbers were applied to
all the three flow tiers (26.5, 30, and 34 MGD).

Per the 6/3/2021 application for 30 MGD, this facility serves a population of 208,968 residents and
operates a pretreatment program currently with 14 Significant Industrial Users (SIUs), including 2
Categorical Industrial Users (CIUs). The facility has an Outfall 001 that discharges to Ricky River, which
is currently classified C water in Yadkin-Pee Dee River Basin.

2. Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receiving Stream(s): Outfall 001 – Rocky River
Stream Segment: 13-17b3
Stream Classification: C
Drainage Area (mi2): 278
Summer 7Q10 (cfs) 20.7
Winter 7Q10 (cfs): 31.9
30Q2 (cfs): 44.5
Average Flow (cfs): 229
IWC (% effluent): 66.5% at 26.5 MGD, 69% at 30 MGD, 71.8% at 34 MGD
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303(d) listed/parameter: Yes/Benthos, Turbidity
Subject to TMDL/parameter: Yes - State wide Mercury TMDL implementation.
Basin/Sub-basin/HUC: 03-07-12/03040105
USGS Topo Quad: Concord SE

3. Effluent Data Summary
Effluent data for Outfall 001 is summarized below for the period of September 2016 through August
2019.
Table 3. Effluent Data Summary Outfall 001
Parameter Units Average Max Min Permit
Limit
Flow MGD 18.7 59.74 13.09 MA 26.5
CBOD summer mg/l < 4.2 17.9 < 2 WA 23.1
MA 15.4
CBOD winter mg/l 4.79 30 < 2 WA 33.9
MA 22.6
NH3N summer mg/l 2.17 20 < 0.1 WA 10.8
MA 3.6
NH3N winter mg/l < 4.37 24 < 0.1 WA 27.0
MA 9.0
TSS mg/l 10.78 65 3 WA 45.0
MA 30.0
pH SU 6.38 7.3 6 6.0 ≤ pH ≤
9.0
Fecal coliform #/100 ml 27.60 > 7259 < 1
(geometric)
WA 400
MA 200
DO mg/l 8.48 12.5 6.5 DA ≥ 6.0
TRC µg/l 29.25 48 < 25
DM 27.0
(< 50
compliance)
Temperature ° C 21.66 28 13
TN mg/l 22.24 32.36 13.74
TP mg/l 2.78 3.8 1.1
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Total Copper ug/l 6.13 12.7 3.2
Total Zinc ug/l 53 78.2 34.8
Total Mercury ng/l < 1.93 3.6 < 1
Total Selenium ug/l < 5 < 5 < 5
MA-Monthly Average, WA-Weekly Average, DM-Daily Maximum, DA=Daily 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. Because the facility is a participant in the Yadkin-Pee Dee River Basin
Association, the instream monitoring requirements are waived. Data were available for review for two
instream Monitoring Coalition stations, Q7780000 (upstream) and Q8210000 (downstream), sampled
from July 2016 through June 2019.
Table 4. Instream Data Summary
Parameter Units Minimum Maximum Average Location
Dissolved Oxygen mg/l 6.5 10.2 7.75 U
6.3 10.9 7.73 D
Temperature deg c 4.1 26.9 18.89 U
4.8 27.8 19.48 D
Conductivity umhos/cm 108 251 149.39 U
117 310 148.33 D
Fecal Coliform
(geometric mean) cfu/100ml 62 6700 162.53 U
58 4700 146.68 D
Note: Instream data are summarized for the period of July 2016 through June 2019.

DO: upstream DO ranged from 6.5 to 10.2 mg/L, while the range for downstream DO was 6.3 to 10.9
mg/L. The instream DO data indicated a minimum daily average of 5.0 mg/L was maintained in the
receiving stream [per 15A NCAC 02B .0211(6)].
Temperature: downstream temperature ranged from 4.8 to 27.8 degrees Celsius. The maximum
temperatures were less than 29 degrees Celsius, which met the requirement per 15A NCAC 02B
.0211(18).
Conductivity: Based on the t-Test, it was concluded with 95% confidence that statistically significant
difference does not exist (p-value > 0.05) between upstream and downstream conductivity.
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Fecal Coliform: the geometric means of fecal coliform are 162.53/100ml for upstream and 146.68/100ml
for downstream, respective. Both of the numbers are less than 200/100ml.
This draft permit maintains the same instream monitoring requirements.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (Y/N): Y
Name of Monitoring Coalition: Yadkin-Pee Dee River Basin Association

5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): The facility reported one
Fecal Coliform limit violation in 2019, one Ammonia Nitrogen violation in 2017, and eleven Ammonia
Nitrogen violations in 2019.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed 19 of 19 quarterly chronic toxicity tests, as well as all 4 second species
chronic toxicity tests, sampled in February, May, August and November of 2017.
Summarize the results from the most recent compliance inspection: The last facility inspection conducted
on 1/21/2021 reported that at time of inspection the facility was well maintained and operated.

6. Water Quality-Based Effluent Limitations (WQBELs)
Dilution and Mixing Zones
In accordance with 15A NCAC 2B.0206, the following streamflows are used for dilution considerations
for development of WQBELs: 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/l for Municipals) may be appropriate if deemed more stringent based on dilution and
model results.
If permit limits are more stringent than TBELs, describe how limits were developed: CBOD limits at 26.5
MGD were based on freezing mass load at 24 MGD, while at 34 MGD, CBOD limits were based on
modeling. To expedite the NPDES permitting process for 30 MGD expansion, WSACC is willing to
accept the same CBOD limits for 30 MGD flow tier as DWR previously proposed for the 34 MGD flow
tier.

Ammonia and Total Residual Chlorine Limitations
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Limitations for ammonia are based on protection of aquatic life utilizing an ammonia chronic criterion of
1.0 mg/l (summer) and 1.8 mg/l (winter). Acute ammonia limits are derived from chronic criteria,
utilizing a multiplication factor of 3 for Municipals and a multiplication factor of 5 for Non-Municipals.
Limitations for Total Residual Chlorine (TRC) are based on the NC water quality standard for protection
of aquatic life (17 ug/l) 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:
In the 1st draft permit:
The NH3/TRC Wasteload Allocation (WLA) spreadsheet was used to calculate limits using the 7Q10 s of
25.2 cfs and 7Q10 w of 35.2 cfs for 26.5 MGD. The TRC allowable concentration remains the same. In
the last permit, the TRC limit was set as Daily Average, which has been corrected to Daily Maximum in
this permit.
Currently DWR uses EPA’s guidance and criteria in developing the use of 1.0 mg/L (summer) and 1.8
mg/L (winter) in wasteload allocations for all major facilities to protect against instream toxicity. As a
result, the wasteload allocation resulted in more stringent ammonia-nitrogen (NH3-N) limits at 26.5
MGD. More stringent limits were determined at 34 MGD for TRC and NH3-N based on the toxicity
criteria and updated low-flow characteristics from USGS for the Rocky River at the discharge location
(Table 5).
Table 5. Current and new Ammonia limits at 26.5 MGD and 34 MGD
Season
26.5 MGD 34 MGD
Monthly
Average
Weekly
Average
Monthly
Average
Weekly
Average*
Summer, existing (mg/L) 3.6 10.8 2.0 6.0
Summer, new (mg/L) 1.5 4.5 1.3 3.9
Winter, existing (mg/L) 9.0 27.0 4.0 12.0
Winter, new (mg/L) 3.0 9.0 2.6 7.8
*Wasteload allocation determined using updated low-flow characteristics
The Rocky River Regional WWTP experienced a plant upset starting in February 2019 and continuing
through into June 2019. That appeared to be a reaction to strong toxins coming into the WWTP that
resulted in a negative impact to microorganisms. The WWTP had difficulty in maintaining a healthy
population of biomass, which resulted in several NH3-N violations from March to June of 2019. Starting
from July 2019, the WWTP resolved the problem and made improvement to the plant performance. Since
then, most of the daily NH3-N data did not exceed 0.2 mg/L, which were much lower than the new
weekly and monthly average limits.
However, during the public comment period, WSACC submitted comments on 4/27/2020 requesting
DWR to recalculate the proposed ammonia limits using site-specific data due to substantial differences
between site-specific pH, temperature, background ammonia and the default values using in the DEQ's
1999 Ammonia Toxicity Policy (1.0 mg/L summer, and 1.8 mg/L winter). WSACC also indicated the
RRRWWTP is not capable of consistent attainment of proposed ammonia limits at its current
configuration, so a compliance schedule is needed for the proposed ammonia limits. WSACC and the
retained consulting firm spent 4 months performing an evaluation study focusing on the capability of the
existing RRRWWTP to provide treatment and comply with the proposed ammonia limits at 26.5 MGD.
The study concludes the existence of significant design factors cannot be readily corrected and impede
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compliance with the proposed ammonia limits. Based on the study and several conversations with
WSACC, DWR agreed to use site-specific data to calculate ammonia limits, and to provide a compliance
schedule for the proposed ammonia limits.
In the 2nd draft permit with 30 MGD expansion:
DWR recalculated the ammonia limits for 26.5 MGD, 30 MGD, and 34 MGD based on site-specific
ammonia targets developed from EPA’s 2013 ammonia criteria. The 90th percentiles for all the inputs
were used to the calculations, including effluent pH/temperature, instream pH/temperature, and
background ammonia concentration. A detailed site-specific ammonia WLA spreadsheet is attached. The
updated ammonia limits for all the 3 flow tiers are listed in Table 6 below.
Table 6. New Site-Specific Ammonia limits for 26.5 MGD, 30 MGD and 34 MGD
Season
26.5 MGD 30 MGD 34 MGD
Monthly
Average
Weekly
Average
Monthly
Average
Weekly
Average
Monthly
Average
Weekly
Average
Summer, new (mg/L) 1.7 4.2 1.6 4.1 1.6 4.0
Winter, new (mg/L) 3.9 9.8 3.7 9.3 3.5 8.8

Using updated USGS low-flow data and NH3/TRC WLA spreadsheet, TRC limits have been updated
from 27 ug/l daily average (DA) to 26 ug/l daily maximum (DM) at 26.5 MGD, and from DA 25 ug/l to
DM 24 ug/l at 34 MGD. The TRC limit at 30 MGD is DM 25 ug/l.

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 ½ 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 March 2015
and August 2019. Pollutants of concern included toxicants with positive detections and associated water
quality standards/criteria. Based on this analysis, the following permitting actions are proposed for this
permit:
• Effluent Limit with Monitoring. The following parameters will receive a water quality-based
effluent limit (WQBEL) since they demonstrated a reasonable potential to exceed applicable
water quality standards/criteria: NA
• Monitoring Only. The following parameters will receive a monitor-only requirement since they
did not demonstrate reasonable potential to exceed applicable water quality standards/criteria,
but the maximum predicted concentration was >50% of the allowable concentration; or a target
PQL was not achieved for the past several years: Silver at all three flow tiers. Silver was
reported below detection at 2.5 ug/L. Future sampling should analyze down to 1 ug/L (PQL).
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• 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, Beryllium, Cadmium, Total Chromium, Copper, Cyanide, Lead, Nickel,
Selenium and Zinc at all three flow tiers
 Arsenic was reported below detection at 2.5 ug/L. Future sampling should analyze down
to 2 ug/L (PQL).
 Cadmium was reported below detection at 2.5 ug/L. Future sampling should analyze
down to 0.5 ug/L (PQL).
 Lead was reported below detection at 2.5 ug/L. Future sampling should analyze down to
2 ug/L (PQL).
 Selenium was reported below detection at 5 ug/L. Future sampling should analyze down
to 1 ug/L (PQL).
• POTW Effluent Pollutant Scan Review: Three effluent pollutant scans were evaluated for
additional pollutants of concern.
o The following parameter(s) will receive a water quality-based effluent limit (WQBEL)
with monitoring, since as part of a limited data set, two samples exceeded the allowable
discharge concentration: NA
o The following parameter(s) will receive a monitor-only requirement, since as part of a
limited data set, one sample exceeded the allowable discharge concentration: NA
Attached are the RPA results, as well as a copy of the guidance entitled “NPDES Implementation of
Instream Dissolved Metals Standards – Freshwater Standards”.

Toxicity Testing Limitations
Permit limits and monitoring requirements for Whole Effluent Toxicity (WET) have been established in
accordance with Division guidance (per WET Memo, 8/2/1999). Per WET guidance, all NPDES permits
issued to Major facilities or any facility discharging “complex” wastewater (contains anything other than
domestic waste) will contain appropriate WET limits and monitoring requirements, with several
exceptions. The State has received prior EPA approval to use an Alternative WET Test Procedure in
NPDES permits, using single concentration screening tests, with multiple dilution follow-up upon a test
failure.
Describe proposed toxicity test requirement: This is a Major POTW, and a chronic WET limit of 66.5%
at 26.5 MGD, 69% at 30 MGD, and 71.8% at 34 MGD will continue on a quarterly frequency.

Mercury Statewide TMDL Evaluation
There is a statewide TMDL for mercury approved by EPA in 2012. The TMDL target was to comply
with EPA’s mercury fish tissue criteria (0.3 mg/kg) for human health protection. The TMDL established a
wasteload allocation for point sources of 37 kg/year (81 lb/year), and is applicable to municipals and
industrial facilities with known mercury discharges. Given the small contribution of mercury from point
sources (~2% of total load), the TMDL emphasizes mercury minimization plans (MMPs) for point source
control. Municipal facilities > 2 MGD and discharging quantifiable levels of mercury (>1 ng/l) will
receive an MMP requirement. Industrials are evaluated on a case-by-case basis, depending if mercury is a
pollutant of concern. Effluent limits may also be added if annual average effluent concentrations exceed
the WQBEL value (based on the NC WQS of 12 ng/l) and/or if any individual value exceeds a TBEL
value of 47 ng/l
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Table 6. Mercury Effluent Data Summary
2015 2016 2017 2018 2019
# of Samples 5 4 4 4 3
Annual Average, ng/L 13.1 8.8 1.8 0.9 2.8
Maximum Value, ng/L 17.50 30.00 2.60 1.40 3.60
TBEL, ng/L 47
WQBEL, ng/L 18.0 (26.5 MGD) / 17.3 (30 MGD) / 16.7 (34 MGD)

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. However, since the facility is >2 MGD and reported quantifiable levels of mercury (> 1
ng/l), a 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: NA

Other WQBEL Considerations
If applicable, describe any other parameters of concern evaluated for WQBELs: NA
If applicable, describe any special actions (HQW or ORW) this receiving stream and classification shall
comply with in order to protect the designated waterbody: 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: A 4-year schedule of
compliance (listed below) has been added to the permit [A. (6) Schedule of Compliance for Ammonia-
Nitrogen at 26.5 MGD].
1. By October 31, 2021, the Permittee shall complete pilot study of Nitrification Enhanced Facility,
30% design, and have selected the design-builder for these improvements. A report summarizing
the results of the pilot study and a Preliminary Engineering Report shall be submitted for review.
2. By May 31, 2022, the Permittee shall complete 90% design and submit a progress report for
review.
3. By August 31, 2022, the Permittee shall complete 100% design and submit a progress report and
an application for Authorization to Construct for plant modification.
4. By December 31, 2022, the Permittee shall send out Notice to Proceed and commence
construction. A progress report shall be submitted for review.
5. By December 31, 2023, and December 31, 2024, the Permittee shall submit annual progress
reports summarizing the status of the construction and identify the percentage of construction
completed.
6. By October 31, 2025, achieve compliance with ammonia limits specified in Section A. (1).

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

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7. Technology-Based Effluent Limitations (TBELs)
Municipals
Are concentration limits in the permit at least as stringent as secondary treatment requirements (30 mg/l
BOD5/TSS for Monthly Average, and 45 mg/l for BOD5/TSS for Weekly Average). YES
If NO, provide a justification for alternative limitations (e.g., waste stabilization pond). NA

Are 85% removal requirements for BOD5/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
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. An EAA is not required for an interim flow
tier since there is an existing 34 MGD flow page.

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 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.

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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:
Permit conditions, limits and their proposed changes for 26.5 MGD and 34 MGD are summarized in
Table 7 and 9, respectively. Table 8 shows the limits at the intermediate flow tier of 30 MGD, which is
not available in the current permit.
Table 7. Current Permit Conditions and Proposed Changes at 26.5 MGD
Parameter Current Permit Proposed Change Basis for Condition/Change
Flow MA 26.5 MGD No change 15A NCAC 2B .0505
CBOD5 Summer:
MA 15.4 mg/l
WA 23.1 mg/l
Winter:
MA 22.6 mg/l
WA 33.9 mg/l
No change Based on freezing mass load at 24
MGD
NH3-N Summer:
MA 3.6 mg/l
WA 10.8 mg/l
Winter:
MA 9 mg/l
WA 27 mg/l
Summer:
MA 1.7 mg/l
WA 4.2 mg/l
Winter:
MA 3.9 mg/l
WA 9.8 mg/l
Based on site-specific ammonia
targets developed from EPA’s
2013 ammonia criteria.
Added a 4-yr compliance schedule
TSS MA 30 mg/l
WA 45 mg/l
No change TBEL. Secondary treatment
standards/40 CFR 133 / 15A NCAC
2B .0406
Fecal coliform MA 200 /100ml
WA 400 /100ml
No change WQBEL. State WQ standard, 15A
NCAC 2B .0200
DO ≥ 6 mg/l No change Modeling results to prevent
violations of DO WQS in Rocky
River (1994 fact sheet)
Total Residual
Chlorine
DA 27 ug/L DM 26 ug/L WQBEL. WLA Calculations
spreadsheet with revised low-flow
characteristics
TN Monthly monitoring No change 15A NCAC 02B .0508
TP Monthly monitoring No change 15A NCAC 02B .0508
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Chronic Toxicity Chronic limit, 62% at
26.5 MGD
No change WQBEL. No toxics in toxic
amounts. 15A NCAC 2B.0200 and
15A NCAC 2B.0500
Temperature, ℃ Daily monitoring No change 15A NCAC 2B .0500
pH 6 – 9 standard units No change WQBEL. State WQ standard, 15A
NCAC 2B .0200
Total Silver No requirement Add quarterly
monitoring
Reviewed data non-detect at levels >
target PQL of 1 ug/L; allowable Cw
(chronic)=0.09 ug/L
Total Copper Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Zinc Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Mercury Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Selenium Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Mercury
Minimization Plan
(MMP)
MMP required No change Accordance with 2012 statewide
Mercury TMDL implementation, per
facility size and monitoring data
Total Hardness No requirement Add effluent and
upstream monitoring
Based on adoption of hardness-
dependent metals
MGD – Million gallons per day, MA - Monthly Average, WA – Weekly Average, DM – Daily Max

Table 8. Proposed Limits at 30 MGD
Parameter Proposed Limits Basis for Condition/Change
Flow MA 30 MGD 15A NCAC 2B .0505. Permittee requested a 30
MGD flow tier.
CBOD5 Summer:
MA 10 mg/l
WA 25 mg/l
Winter:
MA 20 mg/l
WA 35 mg/l
Same as the CBOD5 limits at 34 MGD flow
tier.
Page 13 of 16

NH3-N Summer:
MA 1.6 mg/l
WA 4.1 mg/l
Winter:
MA 3.7 mg/l
WA 9.3 mg/l
Based on site-specific ammonia targets
developed from EPA’s 2013 ammonia criteria.
TSS MA 30 mg/l
WA 45 mg/l
TBEL. Secondary treatment standards/40 CFR
133 / 15A NCAC 2B .0406
Fecal coliform MA 200 /100ml
WA 400 /100ml
WQBEL. State WQ standard, 15A NCAC 2B
.0200
DO ≥ 6 mg/l Same as the DO limit at 34 MGD flow tier.
Temperature Daily monitoring 15A NCAC 02B .0500
pH 6 – 9 standard units WQBEL. State WQ standard, 15A NCAC 2B
.0200
Total Residual
Chlorine
DM 25 ug/L WQBEL. WLA Calculations spreadsheet
TN Monthly monitoring 15A NCAC 02B .0508
TP Monthly monitoring 15A NCAC 02B .0508
Total Silver Quarterly monitoring Reviewed data non-detect at levels > target
PQL of 1 ug/L; allowable Cw (chronic)=0.09
ug/L
Chronic Toxicity Chronic limit, 69% at
30 MGD
WQBEL. No toxics in toxic amounts. 15A
NCAC 2B.0200 and 15A NCAC 2B.0500
Mercury
Minimization Plan
(MMP)
MMP required Accordance with 2012 statewide Mercury
TMDL implementation, per facility size and
monitoring data
Total Hardness Add effluent and
upstream monitoring
Based on adoption of hardness-dependent
metals
MGD – Million gallons per day, MA - Monthly Average, WA – Weekly Average, DM – Daily Max
Table 9. Current Permit Conditions and Proposed Changes at 34 MGD
Parameter Current Permit Proposed Change Basis for Condition/Change
Flow MA 34 MGD No change 15A NCAC 2B .0505
CBOD5 Summer:
MA 10 mg/l
WA 25 mg/l
Winter:
MA 20 mg/l
WA 35 mg/l
No change Based on modeling results for
protection of DO standard
Page 14 of 16

NH3-N Summer:
MA 2 mg/l
WA 6 mg/l
Winter:
MA 4 mg/l
WA 12 mg/l
Summer:
MA 1.6 mg/l
WA 4.0 mg/l
Winter:
MA 3.5 mg/l
WA 8.8 mg/l
Based on site-specific ammonia
targets developed from EPA’s
2013 ammonia criteria.
TSS MA 30 mg/l
WA 45 mg/l
No change TBEL. Secondary treatment
standards/40 CFR 133 / 15A NCAC
2B .0406
Fecal coliform MA 200 /100ml
WA 400 /100ml
No change WQBEL. State WQ standard, 15A
NCAC 2B .0200
DO ≥ 6 mg/l No change Modeling results to prevent
violations of DO WQS in Rocky
River (1994 fact sheet)
Temperature Daily monitoring No change 15A NCAC 02B .0500
pH 6 – 9 standard units No change WQBEL. State WQ standard, 15A
NCAC 2B .0200
Total Residual
Chlorine
DA 25 ug/L DM 24 ug/L WQBEL. WLA Calculations
spreadsheet with revised low-flow
characteristics
TN Monthly monitoring No change 15A NCAC 02B .0508
TP Monthly monitoring No change 15A NCAC 02B .0508
Total Silver No requirement Add quarterly
monitoring
Reviewed data non-detect at levels >
target PQL of 1 ug/L; allowable Cw
(chronic)=0.09 ug/L
Total Copper Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Zinc Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Mercury Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Total Selenium Quarterly monitoring Remove monitoring
requirement
No reasonable potential to exceed
allowable Cw found
Chronic Toxicity Chronic limit, 71.8% at
34 MGD
Chronic limit, 71.8%
at 34 MGD
Revised IWC based on updated
7Q10 from USGS. WQBEL. No
toxics in toxic amounts. 15A NCAC
2B.0200 and 15A NCAC 2B.0500
Mercury
Minimization Plan
(MMP)
MMP required No change Accordance with 2012 statewide
Mercury TMDL implementation, per
facility size and monitoring data
Page 15 of 16

Total Hardness No requirement Add effluent and
upstream monitoring
Based on adoption of hardness-
dependent metals
MGD – Million gallons per day, MA - Monthly Average, WA – Weekly Average, DM – Daily Max

13. Public Notice Schedule:

Permit to Public Notice: 08/11/2021

Per 15A NCAC 2H .0109 & .0111, The Division will receive comments for a period of 30 days following
the publication date of the public notice. Any request for a public hearing shall be submitted to the
Director within the 30 days comment period indicating the interest of the party filing such request and the
reasons why a hearing is warranted.

14. NPDES Division Contact:
If you have questions regarding any of the above information or on the attached permit, please contact
Min Xiao at [phone] or via email at min.xiao@ncdenr.

15. Fact Sheet Addendum (if applicable):

Were there any changes made since the Draft Permit was public noticed (Yes/No): Yes
If Yes, list changes and their basis below: The dates for NH3 as N (winter) have been corrected.

16. Fact Sheet Attachments (if applicable):
• NPDES Pretreatment POCs Review Form
• 2018 NC 303(d) List, page 259
• Monitoring Report Violations Summary
• Whole Effluent Toxicity Testing and Self Monitoring Summary
• WWTP Compliance Inspection Report
• Site-specific NH3/TRC WLA for all three flow tiers
• RPA Sheets for all flow tiers
o Data Analysis
o Input Information
o Results Summary
o Dissolved to Total Metal Calculation
• NPDES Implementation of Instream Dissolved Metals Standards – Freshwater Standards
Page 16 of 16

• Mercury TMDL Calculations (26.4 MGD using previous flow data, 34 MGD using updated flow
data)
• BOD & TSS Removal Rate Calculations

municipal renewal X
new industries
WWTP expansion X
Speculative limits
stream reclass.
outfall relocation
7Q10 change
other
other
check applicable PT staff:
BRD, CPF, CTB, FRB, TAR CHO, HIW, LTN, LUM, NES, NEW, ROA,
Keyes, Yitbarek, Litzenberger Keyes, Yitbarek, Litzenberger
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
3) facility has SIUs and DWQ approved Pretreatment Program (list "DEV" if program still under development)
X 3a) Full Program with LTMP
3b) Modified Program with STMP
4) additional conditions regarding Pretreatment attached or listed below
Permitted
Last
Reported
Time
period for
last
reported Actual
Time
period
for
actual LTMP, 3/5/2019
8.849 4.33 2014-2017 2021 Most recent:3/5/2019
NA 12.637 2/13/2018 2021 Next Cycle: 3/3/2024
From LTMP, mg/l Comments
X BOD XX4/month 2
X TSS XXDaily 2.5
X NH3 XX2/week 0.1
X Arsenic Q 0.001
X Cadmium*X X Q 0.001
X Chromium*X X Q 0.001
X Copper*X X X Q 0.001
Cyanide X
X Lead*X X Q 0.001
X Mercury X Q 1 ng/L
Molybdenum
X Nickel*X X Q 0.001
Silver X
X Selenium X Q 0.002
X Zinc*X X X Q 0.002
X Tin 3/5 Years 0.01
X Berryllium Q 0.001
X Cobalt 3/5 Years 0.05
X COD XX1/month 10
TP X
TN X
Footnotes:
*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
Updated by pw
POCs that need to be added to STMP
Yes No
NPDES Permit Public Notice Date: Effective date:180 days after effective (date):
Yes No
NPDES/PT POCs Review Form Version: 2021.00
Check all that apply
L/STMP, approval
date:
Region
7/13/2021
Min Xiao
Rocky River Regional WWTP
NC0036269
Mooresville
Wes Bell
Beverly Metcalf
1/3/2019
Yadkin‐Pee Dee
C
PW: Find S/LTMP document for next section.
NPDES PERMIT WRITER (PW) COMPLETES when drafting NPDES permit:
Uncontrollable Flow, MGD
Industrial Flow, MGD
Regional PT Staff
Facility PT Staff
IWS approval date
Basin
Stream Class
Date of Review
Permit Writer
Facility Name
Permit Number
REGIONAL OFFICE PRETREATMENT STAFF COMPLETES THIS PART:
Is all data required on STMP on DMRs?
Is all data required on STMP in spreadsheets with HWA/AT submittal?
CENTRAL OFFICE PRETREATMENT STAFF COMPLETES THIS PART:
Confirmed that currently the facility has 14 SIUs including 2 CIUs.
This 26.5 MGD facility submitted a renewal applicaiton in April, 2018. The 
renewal is ongoing and the facility requested a 30 MGD flow tier for the NPDES 
permit on 6/3/2021. The permittee indicates the SIUs have increased from 12 
to 14. The CIUs remain to be 2.   
PQLs review
POC in LTMP/ STMPParameter of
Concern (POC)
Check List
POC due to
New effluent
limit or
monitoring in
NPDES permit
POC due to
previous
NPDES/ Non-
Disch Permit
Limit or
monitoring
Required by
EPA*
Required
by 503
Sludge**
POC due
to SIU***
POTW
POC
(Explain
below)***
*
STMP
Effluent
Freq
LTMP
Effluent
Freq
NPDES PERMIT WRITER (PW) COMPLETES when issuing NPDES permit:
PW, please:
- Notify PT in comment section below if you deem necessary to keep
a specific POC in LTMP/STMP
- Email PT staff in central office, regional office, and Facility: draft
permit package.
- Email PT staff in central office, regional office, and Facility: final
permit package. (Note effective date and 180 days after at the
bottom of this form) - Email this
form to PT staff in central office and regional office and add it to the
respective SharePoint PT_Town Folder (04. PT_Towns>
NC00XXXXX>NPDES Permit)
- PQL review note (coming up)
- Notification about DMRs (coming up)
Comments from NPDES pw to PT staff (Central, RO, Facility):
Comments from PT central to NPDES pw, PT staff Facility, and PT staff region ((ex., explanation of any POCs;  info you have on IU related investigations into NPDES problems)::
PT staff central office contact: Kristin Litzenberger
Comments from PT RO Staff to NPDES pw, PT staff Facility, and PT staff central (ex. issues noted missed above, updates on the actions required above)
Facility Summary and NPDES regulatory action:
Updated PERCS Form_NC0036269_NPDES_PT POCs review
Revised: July 24, 2007
2018 NC Category 5 Assessments "303(d) List" Final
St
u
0
CC
Yadkin -Pee Dee River Basi
S2
From Mallard Creek to Reedy Creek
N
0
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U
Classification
Parameter of Interest
Reason for Rating
Assessment Criteria Status
Copper (7 µg/I, AL, FW)
> 10% and >90 conf
Exceeding Criteria
41
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0
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Previous AU Number 13-17b
4-0
m
ength or Area
U
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ent Criteria Status
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w
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Length or Area
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> 10% and >90 conf
Exceeding Criteria
Turbidity (50 NTU, AL, FW miles)
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Exceeding Criteria
From Hamby Branch to Anderson Creek
Previous AU Number 13-17c
Length or Area
Classification C
0
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Parameter of Interest
Reason for Rating
Assessment Criteria Status
Ln
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Exceeding Criteria
Page 259 of 262

O)
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MONITORING REPORT(MR) VIOLATIONS for:
Program Category:
Violation Category:%
MRs Between 9 - 2014 and 8 - 201 y
Permit: NC0036269
Violation Action: %
Param Name %
Facility Name:
Major Minor: %
Mooresville
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FACILITY: Water and Sewer Authority of Cabarrus County - Rocky
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Page 27 of 124

EPA
United States Environmental Protection Agency
Washington, D.C. 20460
Water Compliance Inspection Report
Form Approved.
OMB No. 2040-0057
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 N 52 NC0036269 21/01/21 C S31112171819 20
21 66
Inspection Work Days Facility Self-Monitoring Evaluation Rating B1 QA ----------------------Reserved-------------------
3 N67707172 73 74 75 80
Section B: Facility Data
Name and Location of Facility Inspected (For Industrial Users discharging to POTW, also include
POTW name and NPDES permit Number)
Rocky River WWTP
6400 Breezy Ln
Concord NC 28025
Entry Time/Date Permit Effective Date
Exit Time/Date Permit Expiration Date
09:55AM 21/01/21 13/12/01
Name(s) of Onsite Representative(s)/Titles(s)/Phone and Fax Number(s)
///
James Christian Sims/ORC/704-788-4164/
Other Facility Data
11:51AM 21/01/21 18/10/31
Name, Address of Responsible Official/Title/Phone and Fax Number
Travis M Fowler,232 Davidson Hwy Concord NC 280270428//704-788-4164/Contacted
No
Section C: Areas Evaluated During Inspection (Check only those areas evaluated)
Permit Flow Measurement Operations & Maintenance Records/Reports
Self-Monitoring Program Sludge Handling Disposal Facility Site Review Effluent/Receiving Waters
Laboratory
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
Roberto Scheller DWR/MRO WQ/252-946-6481/
Signature of Management Q A Reviewer Agency/Office/Phone and Fax Numbers Date
W. Corey Basinger DWR/Division of Water Quality/704-235-2194/
EPA Form 3560-3 (Rev 9-94) Previous editions are obsolete.
Page#1
1/28/2021
for WCB 1.28.21
NPDES yr/mo/day
21/01/21
Inspection Type
C3111218
1
Section D: Summary of Finding/Comments (Attach additional sheets of narrative and checklists as necessary)
The subject facility is a 26.5 MGD pure oxygen two stage WWTP. Solids are handled by an onsite
sludge incinerator. The following items were noted during the subject inspection:
- Review of eDMRs for a 12 month period in 2020 indicate that the subject facility is at 82% of
permitted flow.
In accordance with 15A NCAC 02T .0118 DEMONSTRATION OF FUTURE WASTEWATER
TREATMENT CAPACITIES
No permits for sewer line extensions shall be issued to wastewater treatment systems owned or
operated by municipalities, counties, sanitary districts, or public utilities unless they meet the following
requirements: (1) Prior to exceeding 80 percent of the system's permitted hydraulic capacity (based on
the average flow during the last calender year), the permittee shall submit an engineering evaluation...
A copy of "Rocky River Regional Wastewater Treatment Plant Expansion Study" was received in the
Mooresville Regional Office on October 29, 2020.
- Serial number of meter being calibrated should be indicated on calibration sheet.
Deficiency was corrected at time of inspection.
- Effluent from #4 secondary clarifier was flowing under gaps in weir and not over top in v-notch weir
resulting in short-circuiting.
In accordance with your NPDES Permit #NC0036269, Part II, Section C, 2. Proper Operation and
Maintenance; The permittee shall at all times properly operate and maintain all facilities and systems of
treatment and control (and related appurtenances) which are installed or used by the Permittee to
achieve compliance with permit conditions.
- During records review it was noted that the scrubber blowdown flow stream from the sludge
incinerator contains cyanide. Scrubber water and furnance side stream cyanide ranged from 0.712
to 14.81 mg/l with and average of 5.4 mg/l.
In a comment letter for Ammonia Treatment Evaluation Study Comments, dated December 9, 2020, it
is reported that when the WWTP is operated in series mode 70 - 90% of primary effluent is sent to
Step 1 where cyanide is pretreated and removed before combining with remaining primary effluent sent
to Step 2.
NC0036269 17 (Cont.)
Page#2
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Permit Yes No NA NE
(If the present permit expires in 6 months or less). Has the permittee submitted a new
application?
Is the facility as described in the permit?
# Are there any special conditions for the permit?
Is access to the plant site restricted to the general public?
Is the inspector granted access to all areas for inspection?
Copy of draft permit was sent permittee dated March 23, 2020 for review.Comment:
Record Keeping Yes No NA NE
Are records kept and maintained as required by the permit?
Is all required information readily available, complete and current?
Are all records maintained for 3 years (lab. reg. required 5 years)?
Are analytical results consistent with data reported on DMRs?
Is the chain-of-custody complete?
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 operator
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?
Facility has copy of previous year's Annual Report on file for review?
Comment:
Laboratory Yes No NA NE
Are field parameters performed by certified personnel or laboratory?
Are all other parameters(excluding field parameters) performed by a certified lab?
Page#3
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Laboratory Yes No NA NE
# Is the facility using a contract lab?
# Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees
Celsius)?
Incubator (Fecal Coliform) set to 44.5 degrees Celsius+/- 0.2 degrees?
Incubator (BOD) set to 20.0 degrees Celsius +/- 1.0 degrees?
Serial number for meter being calibrated should be indicated on calibration sheet linking
sheet back to a specific meter.
Comment:
Operations & Maintenance Yes No NA NE
Is the plant generally clean with acceptable housekeeping?
Does the facility analyze process control parameters, for ex: MLSS, MCRT, Settleable
Solids, pH, DO, Sludge Judge, and other that are applicable?
At time of inspection facility appeared to be well maintained and operated.Comment:
Bar Screens Yes No NA NE
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:
Grit Removal Yes No NA NE
Type of grit removal
a.Manual
b.Mechanical
Is the grit free of excessive organic matter?
Is the grit free of excessive odor?
# Is disposal of grit in compliance?
Comment:
Influent Sampling Yes No NA NE
Page#4
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Influent Sampling Yes No NA NE
# Is composite sampling flow proportional?
Is sample collected above side streams?
Is proper volume collected?
Is the tubing clean?
# Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees
Celsius)?
Is sampling performed according to the permit?
At time of inspection influent sampler was recorded at 2.9 degrees Celsius.Comment:
Primary Clarifier Yes No NA NE
Is the clarifier free of black and odorous wastewater?
Is the site free of excessive buildup of solids in center well of circular 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?
Is the sludge blanket level acceptable?
Is the sludge blanket level acceptable? (Approximately ¼ of the sidewall depth)
Comment:
Pure Oxygen Yes No NA NE
Type of pure oxygen system Generated on-site
Is there a back-up source for the system?
Are mixers operational?
Are samples port/points easily accessible?
Treatment consist of first stage aeration (pure oxygen); four (4) intermediate clarifiers;
second stage aeration (pure oxygen) with four (4) final clarifiers.
Comment:
Secondary Clarifier Yes No NA NE
Is the clarifier free of black and odorous wastewater?
Is the site free of excessive buildup of solids in center well of circular clarifier?
Are weirs level?
Page#5
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Secondary Clarifier Yes No NA NE
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?
Is the return rate acceptable (low turbulence)?
Is the overflow clear of excessive solids/pin floc?
Is the sludge blanket level acceptable? (Approximately ¼ of the sidewall depth)
At time of inspection it was noted that flow in #4 calrifier was passing from under weir plate
and not over v-notch weirs. Weirs had short-circuited in several places. It is necessary to
temporarily repair weirs until secondary clarifier can be refurbished.
Comment:
Chemical Feed Yes No NA NE
Is containment adequate?
Is storage adequate?
Are backup pumps available?
Is the site free of excessive leaking?
Comment:
Pumps-RAS-WAS Yes No NA NE
Are pumps in place?
Are pumps operational?
Are there adequate spare parts and supplies on site?
Comment:
Effluent Sampling Yes No NA NE
Is composite sampling flow proportional?
Is sample collected below all treatment units?
Is proper volume collected?
Is the tubing clean?
# Is proper temperature set for sample storage (kept at less than or equal to 6.0 degrees
Celsius)?
Is the facility sampling performed as required by the permit (frequency, sampling type
representative)?
At time of inspection effluent sampler was recorded at 3.0 degrees Celsius.Comment:
Page#6
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Effluent Sampling Yes No NA NE
Disinfection-Liquid Yes No NA NE
Is there adequate reserve supply of disinfectant?
(Sodium Hypochlorite) Is pump feed system operational?
Is bulk storage tank containment area adequate? (free of leaks/open drains)
Is the level of chlorine residual acceptable?
Is the contact chamber free of growth, or sludge buildup?
Is there chlorine residual prior to de-chlorination?
Comment:
De-chlorination Yes No NA NE
Type of system ?Liquid
Is the feed ratio proportional to chlorine amount (1 to 1)?
Is storage appropriate for cylinders?
# Is de-chlorination substance stored away from chlorine containers?
Are the tablets the proper size and type?
Sodium Bisulfite used for dechlorination.Comment:
Are tablet de-chlorinators operational?
Number of tubes in use?
Comment:
Flow Measurement - Effluent Yes No NA NE
# Is flow meter used for reporting?
Is flow meter calibrated annually?
Is the flow meter operational?
(If units are separated) Does the chart recorder match the flow meter?
Flow meter last calibrated on 1/15/2021.Comment:
Standby Power Yes No NA NE
Is automatically activated standby power available?
Is the generator tested by interrupting primary power source?
Is the generator tested under load?
Was generator tested & operational during the inspection?
Page#7
Permit:NC0036269
Inspection Date:01/21/2021
Owner - Facility:
Inspection Type:
Rocky River WWTP
Compliance Evaluation
Standby Power Yes No NA NE
Do the generator(s) have adequate capacity to operate the entire wastewater site?
Is there an emergency agreement with a fuel vendor for extended run on back-up power?
Is the generator fuel level monitored?
Comment:
Effluent Pipe Yes No NA NE
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?
At time of inspection the point of discharge into Rocky River was reviewed and a small
amount of very fine foam was being generated. Foam dissipated 50 - 60 feet downstream of
discharge point..
Comment:
Solids Handling Equipment Yes No NA NE
Is the equipment operational?
Is the chemical feed equipment operational?
Is storage adequate?
Is the site free of high level of solids in filtrate from filter presses or vacuum filters?
Is the site free of sludge buildup on belts and/or rollers of filter press?
Is the site free of excessive moisture in belt filter press sludge cake?
The facility has an approved sludge management plan?
Facility has two gravity-flow sludge thickners, sludge conditioning (plolymer addition), two (2)
centrifuges, sludge incinerator, and sludge-ash settling basin.
Comment:
Page#8
Site-Specific NH3/TRC WLA Calculations
Facility: Rocky River Regional WWTP Receiving water pH(upstream-summer)7.6
Permit No. NC0036269 Receiving water pH (upstream-winter)7.4
Prepared By: M.Montebello
Temperature (upstream-summer)25.75
Use Site Specific (FW, SW)Yes Temperature (upstream-winter)13.54
Receiving Water Class FW If SW or FW-SW,salinity (ppt-summer)
Supplemental Class If SW or FW-SW,salinity (ppt-winter)
WS Classification (if needed) Use Site Specific upstream ammonia
Location (no site spec temp.)Bkgd ammonia (upstream-summer)0.232
Use Site Specific pH Yes Bkgd ammonia (upstream-winter)0.210
Is Class PNA/HQW
Effluent Temperature (Summer)27 pH (mixed-summer)7.07
Effluent Temperature (Winter)20 # pH (mixed-winter)6.80
Effluent pH (Summer)6.8 Temperature (mixed-summer)26.58
Effluent pH (Winter)6.5 Temperature (mixed-winter)17.84
Enter Design Flow (MGD):26.5
Enter s7Q10 (cfs):20.7
Enter w7Q10 (cfs):31.9
Total Residual Chlorine (TRC) Ammonia (Summer)
Daily Maximum Limit (ug/l) Monthly Average Limit (mg NH3-N/l)
s7Q10 (CFS) 20.7 s7Q10 (CFS)20.7
DESIGN FLOW (MGD) 26.5 DESIGN FLOW (MGD)26.5
DESIGN FLOW (CFS) 41.075 DESIGN FLOW (CFS)41.075
STREAM STD (UG/L) 17.0 INSTREAM STD (MG/L)1.2
Upstream Bkgd (ug/l) 0 Upstream Bkgd (mg/l)0.22
IWC (%) 66.49 IWC (%)66.49
Allowable Conc. (ug/l) 26 Allowable Monthly Conc. (mg/l)1.7
Allowable Weekly Con. (mg/l)4.2 2.5 X
Fecal Coliform Ammonia (Winter)
Monthly Average Limit:200/100ml Monthly Average Limit (mg NH3-N/l)
(If DF >331; Monitor)
(If DF<331; Limit) w7Q10 (CFS) 31.9
Dilution Factor (DF) 1.50 DESIGN FLOW (MGD) 26.5
DESIGN FLOW (CFS) 41.075
INSTREAM STD (MG/L) 2.3
Upstream Bkgd (mg/l) 0.220
IWC (%) 56.29
Allowable Monthly Conc. (mg/l) 3.9
Allowable Weekly Conc. (mg/l) 9.8 2.5 X
If ammonia toxicity is limiting, winter ammonia (NH3-N) limits cannot exceed twice summer (15A NCAC 2B .0404(c)):
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/l to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/l, Monitor Only
2. For site specific, Monthly Avg limit x 2.5 3 = Weekly Avg limit (Municipals); otherwise 3X, capped at 35 mg/l
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis); capped at 35 mg/l
4. Winter limits (if ammonia toxicity is limiting) cannot exceed twice the summer limits, 15A NCAC 02B .0404
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non-Muni)

Site-Specific NH3/TRC WLA Calculations
Facility: Rocky River Regional WWTP Receiving water pH(upstream-summer)7.6
Permit No. NC0036269 Receiving water pH (upstream-winter)7.4
Prepared By: M.Montebello
Temperature (upstream-summer)25.75
Use Site Specific (FW, SW)Yes Temperature (upstream-winter)13.54
Receiving Water Class FW If SW or FW-SW,salinity (ppt-summer)
Supplemental Class If SW or FW-SW,salinity (ppt-winter)
WS Classification (if needed) Use Site Specific upstream ammonia
Location (no site spec temp.)Bkgd ammonia (upstream-summer)0.232
Use Site Specific pH Yes Bkgd ammonia (upstream-winter)0.210
Is Class PNA/HQW
Effluent Temperature (Summer)27 pH (mixed-summer)7.05
Effluent Temperature (Winter)20 # pH (mixed-winter)6.78
Effluent pH (Summer)6.8 Temperature (mixed-summer)26.61
Effluent pH (Winter)6.5 Temperature (mixed-winter)18.01
Enter Design Flow (MGD):30
Enter s7Q10 (cfs):20.7
Enter w7Q10 (cfs):31.9
Total Residual Chlorine (TRC) Ammonia (Summer)
Daily Maximum Limit (ug/l) Monthly Average Limit (mg NH3-N/l)
s7Q10 (CFS) 20.7 s7Q10 (CFS)20.7
DESIGN FLOW (MGD) 30 DESIGN FLOW (MGD)30
DESIGN FLOW (CFS) 46.5 DESIGN FLOW (CFS)46.5
STREAM STD (UG/L) 17.0 INSTREAM STD (MG/L)1.2
Upstream Bkgd (ug/l) 0 Upstream Bkgd (mg/l)0.22
IWC (%) 69.20 IWC (%)69.20
Allowable Conc. (ug/l) 25 Allowable Monthly Conc. (mg/l)1.6
Allowable Weekly Con. (mg/l)4.1 2.5 X
Fecal Coliform Ammonia (Winter)
Monthly Average Limit:200/100ml Monthly Average Limit (mg NH3-N/l)
(If DF >331; Monitor)
(If DF<331; Limit) w7Q10 (CFS) 31.9
Dilution Factor (DF) 1.45 DESIGN FLOW (MGD) 30
DESIGN FLOW (CFS) 46.5
INSTREAM STD (MG/L) 2.3
Upstream Bkgd (mg/l) 0.220
IWC (%) 59.31
Allowable Monthly Conc. (mg/l) 3.7
Allowable Weekly Conc. (mg/l) 9.3 2.5 X
If ammonia toxicity is limiting, winter ammonia (NH3-N) limits cannot exceed twice summer (15A NCAC 2B .0404(c)):
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/l to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/l, Monitor Only
2. For site specific, Monthly Avg limit x 2.5 3 = Weekly Avg limit (Municipals); otherwise 3X, capped at 35 mg/l
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis); capped at 35 mg/l
4. Winter limits (if ammonia toxicity is limiting) cannot exceed twice the summer limits, 15A NCAC 02B .0404
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non-Muni)

Site-Specific NH3/TRC WLA Calculations
Facility: Rocky River Regional WWTP Receiving water pH(upstream-summer)7.6
Permit No. NC0036269 Receiving water pH (upstream-winter)7.4
Prepared By: M.Montebello
Temperature (upstream-summer)25.75
Use Site Specific (FW, SW)Yes Temperature (upstream-winter)13.54
Receiving Water Class FW If SW or FW-SW,salinity (ppt-summer)
Supplemental Class If SW or FW-SW,salinity (ppt-winter)
WS Classification (if needed) Use Site Specific upstream ammonia
Location (no site spec temp.)Bkgd ammonia (upstream-summer)0.232
Use Site Specific pH Yes Bkgd ammonia (upstream-winter)0.210
Is Class PNA/HQW
Effluent Temperature (Summer)27 pH (mixed-summer)7.03
Effluent Temperature (Winter)20 # pH (mixed-winter)6.75
Effluent pH (Summer)6.8 Temperature (mixed-summer)26.65
Effluent pH (Winter)6.5 Temperature (mixed-winter)18.18
Enter Design Flow (MGD):34
Enter s7Q10 (cfs):20.7
Enter w7Q10 (cfs):31.9
Total Residual Chlorine (TRC) Ammonia (Summer)
Daily Maximum Limit (ug/l) Monthly Average Limit (mg NH3-N/l)
s7Q10 (CFS) 20.7 s7Q10 (CFS)20.7
DESIGN FLOW (MGD) 34 DESIGN FLOW (MGD)34
DESIGN FLOW (CFS) 52.7 DESIGN FLOW (CFS)52.7
STREAM STD (UG/L) 17.0 INSTREAM STD (MG/L)1.2
Upstream Bkgd (ug/l) 0 Upstream Bkgd (mg/l)0.22
IWC (%) 71.80 IWC (%)71.80
Allowable Conc. (ug/l) 24 Allowable Monthly Conc. (mg/l)1.6
Allowable Weekly Con. (mg/l)4.0 2.5 X
Fecal Coliform Ammonia (Winter)
Monthly Average Limit:200/100ml Monthly Average Limit (mg NH3-N/l)
(If DF >331; Monitor)
(If DF<331; Limit) w7Q10 (CFS) 31.9
Dilution Factor (DF) 1.39 DESIGN FLOW (MGD) 34
DESIGN FLOW (CFS) 52.7
INSTREAM STD (MG/L) 2.3
Upstream Bkgd (mg/l) 0.220
IWC (%) 62.29
Allowable Monthly Conc. (mg/l) 3.5
Allowable Weekly Conc. (mg/l) 8.8 2.5 X
If ammonia toxicity is limiting, winter ammonia (NH3-N) limits cannot exceed twice summer (15A NCAC 2B .0404(c))
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/l to protect for acute toxicity
Ammonia (as NH3-N)
1. If Allowable Conc > 35 mg/l, Monitor Only
2. For site specific, Monthly Avg limit x 2.5 3 = Weekly Avg limit (Municipals); otherwise 3X, capped at 35 mg/l
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis); capped at 35 mg/l
4. Winter limits (if ammonia toxicity is limiting) cannot exceed twice the summer limits, 15A NCAC 02B .0404
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non-Muni)

Ammonia NotepH Temp pH TempSummer WinterEffluent 90th6.80 27.0 6.50 20.0 Data from DMR (Jan. 2017‐Dec.2019)Upstream 90th7.60 25.75 7.40 13.5 0.232 0.21 Data from YPDRBA (Jan. 2017‐Dec.2019)Summer Winter
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REQUIRED DATA ENTRYNameWQSTypeChronicModifierAcute PQL UnitsFacility NameRocky River Regional WWTPPar01ArsenicAquactic LifeC 150 FW 340 ug/LWWTP/WTP ClassClass IVPar02ArsenicHuman Health Water SupplyC 10 HH/WS N/A ug/LNPDES PermitNC0036269Par03BerylliumAquatic LifeNC 6.5 FW 65 ug/LOutfall001Par04CadmiumAquatic LifeNC 1.7704 FW 11.6307 ug/LFlow, Qw (MGD)26.500Par05ChloridesAquatic LifeNC 230 FWmg/LReceiving StreamRocky RiverPar06 Chlorinated Phenolic CompoundsWater SupplyNC 1 A ug/LHUC Number030401050305Par07Total Phenolic CompoundsAquatic LifeNC 300 A ug/LStream ClassPar08Chromium IIIAquatic LifeNC 387.7933 FW 3006.4464 ug/LPar09Chromium VIAquatic LifeNC 11 FW 16 µg/L7Q10s (cfs)20.70Par10Chromium, TotalAquatic LifeNC N/A FW N/A µg/L7Q10w (cfs)31.90Par11CopperAquatic LifeNC 27.3341 FW 41.6699 ug/L30Q2 (cfs)44.50Par12CyanideAquatic LifeNC 5 FW 22 10 ug/LQA (cfs)229.00Par13FluorideAquatic LifeNC 1,800 FW ug/L1Q10s (cfs)17.08Par14LeadAquatic LifeNC 14.7546 FW 382.8859 ug/LEffluent Hardness116.14 mg/L (Avg)Par15MercuryAquatic LifeNC 12 FW 0.5ng/LUpstream Hardness89.35 mg/L (Avg)Par16MolybdenumHuman HealthNC 2000 HH ug/LCombined Hardness Chronic107.17 mg/LPar17NickelAquatic LifeNC 127.5497 FW 1158.4273 µg/LCombined Hardness Acute108.27 mg/LPar18NickelWater SupplyNC 25.0000 WS N/A µg/LData Source(s)Par19SeleniumAquatic LifeNC 5 FW 56 ug/LPar20SilverAquatic LifeNC 0.06 FW 3.6881 ug/LPar21ZincAquatic LifeNC 434.9947 FW 435.2456 ug/LPar22Par23Par24To appy a Model IWC %: Once the Table 1. Project Information Table 2. Parameters of ConcernFreshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsMAXIMUM DATA POINTS = 58CCHECK IF HQW OR ORW WQSCHECK TO APPLY MODELApply WS Hardness WQC26.5 MGD RPA, input7/9/2021
Rocky River Regional WWTP≥Outfall 001NC0036269Freshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsQw = 26.5 MGDMAXIMUM DATA POINTS = 58Qw (MGD) = 26.50WWTP/WTP Class:Class IVCOMBINED HARDNESS (mg/L)1Q10S (cfs) = 17.08IWC% @ 1Q10S = 70.63021236Acute = 108.27 mg/L7Q10S (cfs) = 20.70 IWC% @ 7Q10S = 66.49129907Chronic = 107.17 mg/L7Q10W (cfs) = 31.90 IWC% @ 7Q10W = 56.2863994530Q2 (cfs) = 44.50IWC% @ 30Q2 = 47.99883143Avg. Stream Flow, QA (cfs) = 229.00IW%C @ QA = 15.20873831Receiving Stream:Stream Class:CPARAMETERRECOMMENDED ACTIONChronicApplied StandardAcuten# Det. Max Pred CwAcute (FW): 481.4Arsenic C150 FW(7Q10s) 340 ug/L218 2 3.8 Chronic (FW): 225.6No value > Allowable CwArsenic C10HH/WS(Qavg) ug/L Chronic (HH): 65.8No value > Allowable CwAcute: 92.03Beryllium NC6.5 FW(7Q10s) 655ug/L 18 0 2.95Chronic: 9.78NO DETECTSMax MDL = 5Acute: 16.467Cadmium NC1.7704 FW(7Q10s) 11.6307 ug/L 18 0 1.4130.5Chronic: 2.663NO DETECTSMax MDL = 2.5Chromium, Total NC5µg/L 18 0 1.3NO DETECTSMax MDL = 2.5Acute: 59.00Copper NC27.3341 FW(7Q10s) 41.66992ug/L 19 19 15.37Chronic: 41.11No value > Allowable CwAcute: 31.1Cyanide NC5 FW(7Q10s) 22 10 ug/L 3 0 15.0Note: n ≤ 9C.V. (default)Chronic: 7.5Limited data setNO DETECTSMax MDL = 10Acute: 542.099Lead NC14.7546 FW(7Q10s) 382.88592ug/L 18 0 1.288Chronic: 22.190NO DETECTSMax MDL = 2.5Acute (FW): 1,640.1Nickel NC127.5497 FW(7Q10s) 1158.4273 µg/L218 17 6.1 Chronic (FW): 191.8No value > Allowable CwNickel NC25.0000 WS(7Q10s) µg/L Chronic (WS): 37.6PQLUNITSTYPEAllowable CwREASONABLE POTENTIAL RESULTSNC STANDARDS OR EPA CRITERIA Rocky River HUC 030401050305No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredNo detects, no monitoring required.No detectes, all values less than 2.5 ug/L. No Monitoring required. However, the DWR's PQL is 0.5 ug/L. Future sampling should analyze down to 0.5 ug/L.No detectes, all values less than 2.5 ug/L. No Monitoring required. However, the DWR's PQL is 2 ug/L. Future sampling should analyze down to 2 ug/L.No detectes, all values less than 5 ug/L. No Monitoring required. Max reported value = 1.25No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requireda: No monitoring required if all Total Chromium samples are < 5 µg/L or Pred. max for Total Cr is < allowable Cw for Cr VI.No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredPage 1 of 226.5 MGD RPA, rpa7/9/2021
Rocky River Regional WWTP≥Outfall 001NC0036269Freshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsQw = 26.5 MGDNo value > Allowable CwAcute: 79.3Selenium NC5 FW(7Q10s) 561ug/L 19 1 2.7Chronic: 7.5No value > Allowable CwAcute: 5.222Silver NC0.06 FW(7Q10s) 3.68811ug/L 8 0 2.375Note: n ≤ 9C.V. (default)Chronic: 0.090Limited data setNO DETECTSMax MDL = 2.5Acute: 616.2Zinc NC434.9947 FW(7Q10s) 435.245610ug/L 19 19 86.8Chronic: 654.2No value > Allowable CwNo RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredNo RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredApply Quarterly Monitoring. Permittee should use sensitive test methods with a target PQL of 1 ug/L. Page 2 of 226.5 MGD RPA, rpa7/9/2021
Date: 7/9/2021FACILITY: Rocky River Regional WWTP Outfall 001NPDES PERMIT: NC0036269 Rec. Stream NPDES 1Q10 Flow Limit [MGD] [MGD] 20.7000 13.3548 11.0194 26.5000 10107.166108.275 66.4913 70.630289.35 116.1444Upstream Hard Avg (mg/L) = 89.35ACAH 108.275EFF Hard Avg (mg/L) = 116.1444ACCH 107.166 Chronic AcuteChronicAcute[ug/l] [ug/l][ug/l] [ug/l]Cadmium (d) 0.45 2.940.2521.77 11.63 Cd -Trout streams0.45 1.830.2521.77 7.23Chromium III (d)(h)78 6080.202387.79 3006.45Chromium VI (d)11 161.00011.00 16.00Chromium, Total (t)N/A N/ACopper (d)(h)9.5 14.50.34827.33 41.67Lead (d)(h)2.71 700.18414.75 382.89Nickel (d)(h)55 5010.432127.55 1158.43Ni - WS streams (t)25 N/ASilver (d)(h,acute)0.06 3.691.0000.06 3.69Zinc (d)(h)125 1250.288434.99 435.25Beryllium 6.5 65 1.0006.5 65Arsenic (d)150 340 1.000150 340 (d) = dissolved metal standard. See 15A NCAC 02B .0211 for more information.(h) = hardness-dependent dissolved metal standard. See 15A NCAC 02B .0211 for more information.(t) = based upon measurement of total recoveable metal. See 15A NCAC 02B .0211 for more information.Dissolved to Total Metal Calculator The Human Health standard for Nickel in Water Supply Streams is 25 mg/L which is Total Recoverable metal standard. In accordance with Federal Regulations, permit limitations must be written as Total Metals per 40 CFR 122.45(c) The Human Health standard for Arsenic is 10 µg/L which is Total Recoverable metal standard.Upstream Hardness Average (mg/L)PARAMETEREffluent Hardness Average (mg/L)Dissolved Metals Criteria after applying hardness equationUS EPA Translators- using Default Partition Coefficients (streams)Total Metal Criteria Total Metal = Dissolved Metal ÷ TranslatorCOMMENTS (identify parameters to PERCS Branch to maintain in facility's LTMP/STMP):Receiving Stream summer 7Q10 (CFS)Receiving Stream summer 7Q10 (MGD)Total Suspended Solids -Fixed Value-(mg/L)Combined Hardness chronic (mg/L)Combined Hardness Acute (mg/L)Instream Wastewater Concentration (Chronic)Instream Wastewater Concentration (Acute)Dissolved to Total Metal CalculatorDo NOT enter any data directly into this spreadsheet.Enter data onto “Table 1” under the Input Sheet and enter “Effluent Hardness” under the Data Sheet.In accordance with 40 CFR 122.45 (c ), permits are, have and must be written as total metals.This calculator has been inserted into the RPA to calculate Total Metal allowable allocations once Table 1 has been completed (Input Sheet) and Effluent hardness has been entered (Data Sheet). 1) Following the spreadsheet from left to right.                  First the allowable allocations for the dissolved metals will appear for all the metals listed once Table 1 is complete and effluent hardness entered. Use a default value of 25 mg/L if no hardness data is available.                          Second, the Dissolved Metal allocations are divided by the Translators to determine the Total Metals that can be allocated to the Permittee. These Total Metals values are automatically inserted into Table 2 and are the allowable Total Metal allocations determined for the Permittee prior to allowing for dilution. See Input sheet Table 2. The final acute and chronic values shown under the RPA sheet are the Total Metal values listed in Table 2 divided by the acute and chronic IWC, respectively.       2) The Translatorsused in the freshwater RPA are the Partition Coefficients published by US EPA in 1984. They are TSS dependent equations and can be found listed with the WQS hardness dependent equations under the sheet labeled Equations. A fixed TSS value of 10 mg/L is used to calculate the Translator values.3)Pretreatment Facilities–PERCS will need a copy of the Dissolved to Total Metal Calculator spreadsheet and the RPA sheet along with the Final Permit.Pretreatment Facilities are required to renew their Headwords Analysis after renewal of their permits. Since all their metal allocations are likely to change PERCS needs to see any new metal permit limits and the allowable allocations for the dissolved metals to assess Maximum Allowable Headworks Loading (MAHL) numbers for each metal based on the Combined Hardness values used in the permit writers RPA calculations.4) For Cadmium, Lead, Nickel, Chromium and Beryllium, if all the effluent sampling data for the last three to five years shows the pollutant at concentrations less than the Practical Quantitative Level (PQL), it is not likely a limit or monitoring will be put in the permit.  However, if the estimated NPDES permit limit is less than the Practical Quantitative Limit (particularly, Cadmium and Lead) and the pollutant is believed to be present, to assess compliance with the new standards and for future permit limit development, monitoring for the pollutant will be required. If the facility is monitoring for the pollutant in its Pretreatment LTMP, no monitoring is needed in the permit.5) For monitoring and compliance purposes if Total 
REQUIRED DATA ENTRYNameWQSTypeChronicModifierAcute PQL UnitsFacility NameRocky River Regional WWTPPar01ArsenicAquactic LifeC 150 FW 340 ug/LWWTP/WTP ClassClass IVPar02ArsenicHuman Health Water SupplyC 10 HH/WS N/A ug/LNPDES PermitNC0036269Par03BerylliumAquatic LifeNC 6.5 FW 65 ug/LOutfall001Par04CadmiumAquatic LifeNC 1.7795 FW 11.6935 ug/LFlow, Qw (MGD)30.000Par05ChloridesAquatic LifeNC 230 FWmg/LReceiving StreamRocky RiverPar06 Chlorinated Phenolic CompoundsWater SupplyNC 1 A ug/LHUC Number030401050305Par07Total Phenolic CompoundsAquatic LifeNC 300 A ug/LStream ClassPar08Chromium IIIAquatic LifeNC 389.9401 FW 3021.7076 ug/LPar09Chromium VIAquatic LifeNC 11 FW 16 µg/L7Q10s (cfs)20.70Par10Chromium, TotalAquatic LifeNC N/A FW N/A µg/L7Q10w (cfs)31.90Par11CopperAquatic LifeNC 27.4920 FW 41.9134 ug/L30Q2 (cfs)44.50Par12CyanideAquatic LifeNC 5 FW 22 10 ug/LQA (cfs)229.00Par13FluorideAquatic LifeNC 1,800 FW ug/L1Q10s (cfs)17.08Par14LeadAquatic LifeNC 14.8630 FW 385.4651 ug/LEffluent Hardness116.14 mg/L (Avg)Par15MercuryAquatic LifeNC 12 FW 0.5ng/LUpstream Hardness89.35 mg/L (Avg)Par16MolybdenumHuman HealthNC 2000 HH ug/LCombined Hardness Chronic107.89 mg/LPar17NickelAquatic LifeNC 128.2792 FW 1164.5021 µg/LCombined Hardness Acute108.95 mg/LPar18NickelWater SupplyNC 25.0000 WS N/A µg/LData Source(s)Par19SeleniumAquatic LifeNC 5 FW 56 ug/LPar20SilverAquatic LifeNC 0.06 FW 3.7276 ug/LPar21ZincAquatic LifeNC 437.4863 FW 437.5315 ug/LPar22Par23Par24To appy a Model IWC %: Once the Table 1. Project Information Table 2. Parameters of ConcernFreshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsMAXIMUM DATA POINTS = 58CCHECK IF HQW OR ORW WQSCHECK TO APPLY MODELApply WS Hardness WQC30 MGD RPA, input7/9/2021
Rocky River Regional WWTP≥Outfall 001NC0036269Freshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsQw = 30 MGDMAXIMUM DATA POINTS = 58Qw (MGD) = 30.00WWTP/WTP Class:Class IVCOMBINED HARDNESS (mg/L)1Q10S (cfs) = 17.08IWC% @ 1Q10S = 73.13620635Acute = 108.95 mg/L7Q10S (cfs) = 20.70 IWC% @ 7Q10S = 69.19642857Chronic = 107.89 mg/L7Q10W (cfs) = 31.90 IWC% @ 7Q10W = 59.3112244930Q2 (cfs) = 44.50IWC% @ 30Q2 = 51.0989011Avg. Stream Flow, QA (cfs) = 229.00IW%C @ QA = 16.8784029Receiving Stream:Stream Class:CPARAMETERRECOMMENDED ACTIONChronicApplied StandardAcuten# Det. Max Pred CwAcute (FW): 464.9Arsenic C150 FW(7Q10s) 340 ug/L218 2 3.8 Chronic (FW): 216.8No value > Allowable CwArsenic C10HH/WS(Qavg) ug/L Chronic (HH): 59.2No value > Allowable CwAcute: 88.88Beryllium NC6.5 FW(7Q10s) 655ug/L 18 0 2.95Chronic: 9.39NO DETECTSMax MDL = 5Acute: 15.989Cadmium NC1.7795 FW(7Q10s) 11.6935 ug/L 18 0 1.4130.5Chronic: 2.572NO DETECTSMax MDL = 2.5Chromium, Total NC5µg/L 18 0 1.3NO DETECTSMax MDL = 2.5Acute: 57.31Copper NC27.4920 FW(7Q10s) 41.91342ug/L 19 19 15.37Chronic: 39.73No value > Allowable CwAcute: 30.1Cyanide NC5 FW(7Q10s) 22 10 ug/L 3 0 15.0Note: n ≤ 9C.V. (default)Chronic: 7.2Limited data setNO DETECTSMax MDL = 10Acute: 527.051Lead NC14.8630 FW(7Q10s) 385.46512ug/L 18 0 1.288Chronic: 21.479NO DETECTSMax MDL = 2.5Acute (FW): 1,592.2Nickel NC128.2792 FW(7Q10s) 1164.5021 µg/L218 17 6.1 Chronic (FW): 185.4No value > Allowable CwNickel NC25.0000 WS(7Q10s) µg/L Chronic (WS): 36.1Max reported value = 1.25No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requireda: No monitoring required if all Total Chromium samples are < 5 µg/L or Pred. max for Total Cr is < allowable Cw for Cr VI.No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredNo detectes, all values less than 2.5 ug/L. No Monitoring required. However, the DWR's PQL is 2 ug/L. Future sampling should analyze down to 2 ug/L.No detectes, all values less than 5 ug/L. No Monitoring required. No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredNo detects, no monitoring required.No detectes, all values less than 2.5 ug/L. No Monitoring required. However, the DWR's PQL is 0.5 ug/L. Future sampling should analyze down to 0.5 ug/L.PQLUNITSTYPEAllowable CwREASONABLE POTENTIAL RESULTSNC STANDARDS OR EPA CRITERIA Rocky River HUC 030401050305Page 1 of 230 MGD RPA, rpa7/9/2021
Rocky River Regional WWTP≥Outfall 001NC0036269Freshwater RPA - 95% Probability/95% Confidence Using Metal TranslatorsQw = 30 MGDNo value > Allowable CwAcute: 76.6Selenium NC5 FW(7Q10s) 561ug/L 19 1 2.7Chronic: 7.2No value > Allowable CwAcute: 5.097Silver NC0.06 FW(7Q10s) 3.72761ug/L 8 0 2.375Note: n ≤ 9C.V. (default)Chronic: 0.087Limited data setNO DETECTSMax MDL = 2.5Acute: 598.2Zinc NC437.4863 FW(7Q10s) 437.531510ug/L 19 19 86.8Chronic: 632.2No value > Allowable CwNo RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredApply Quarterly Monitoring. Permittee should use sensitive test methods with a target PQL of 1 ug/L. No RP, Predicted Max < 50% of Allowable Cw - No Monitoring requiredPage 2 of 230 MGD RPA, rpa7/9/2021
Date: 7/9/2021FACILITY: Rocky River Regional WWTP Outfall 001NPDES PERMIT: NC0036269 Rec. Stream NPDES 1Q10 Flow Limit [MGD] [MGD] 20.7000 13.3548 11.0194 30.0000 10107.891108.946 69.1964 73.136289.35 116.1444Upstream Hard Avg (mg/L) = 89.35ACAH 108.9464EFF Hard Avg (mg/L) = 116.1444ACCH 107.8908 Chronic AcuteChronicAcute[ug/l] [ug/l][ug/l] [ug/l]Cadmium (d) 0.45 2.950.2521.78 11.69 Cd -Trout streams0.45 1.840.2521.78 7.27Chromium III (d)(h)79 6110.202389.94 3021.71Chromium VI (d)11 161.00011.00 16.00Chromium, Total (t)N/A N/ACopper (d)(h)9.6 14.60.34827.49 41.91Lead (d)(h)2.73 710.18414.86 385.47Nickel (d)(h)55 5030.432128.28 1164.50Ni - WS streams (t)25 N/ASilver (d)(h,acute)0.06 3.731.0000.06 3.73Zinc (d)(h)126 1260.288437.49 437.53Beryllium 6.5 65 1.0006.5 65Arsenic (d)150 340 1.000150 340 (d) = dissolved metal standard. See 15A NCAC 02B .0211 for more information.(h) = hardness-dependent dissolved metal standard. See 15A NCAC 02B .0211 for more information.(t) = based upon measurement of total recoveable metal. See 15A NCAC 02B .0211 for more information.Effluent Hardness Average (mg/L)Dissolved Metals Criteria after applying hardness equationUS EPA Translators- using Default Partition Coefficients (streams)Total Metal Criteria Total Metal = Dissolved Metal ÷ TranslatorCOMMENTS (identify parameters to PERCS Branch to maintain in facility's LTMP/STMP):Receiving Stream summer 7Q10 (CFS)Receiving Stream summer 7Q10 (MGD)Total Suspended Solids -Fixed Value-(mg/L)Combined Hardness chronic (mg/L)Combined Hardness Acute (mg/L)Instream Wastewater Concentration (Chronic)Instream Wastewater Concentration (Acute)Dissolved to Total Metal Calculator The Human Health standard for Nickel in Water Supply Streams is 25 mg/L which is Total Recoverable metal standard. In accordance with Federal Regulations, permit limitations must be written as Total Metals per 40 CFR 122.45(c) The Human Health standard for Arsenic is 10 µg/L which is Total Recoverable metal standard.Upstream Hardness Average (mg/L)PARAMETERDissolved to Total Metal CalculatorDo NOT enter any data directly into this spreadsheet.Enter data onto “Table 1” under the Input Sheet and enter “Effluent Hardness” under the Data Sheet.In accordance with 40 CFR 122.45 (c ), permits are, have and must be written as total metals.This calculator has been inserted into the RPA to calculate Total Metal allowable allocations once Table 1 has been completed (Input Sheet) and Effluent hardness has been entered (Data Sheet). 1) Following the spreadsheet from left to right.                  First the allowable allocations for the dissolved metals will appear for all the metals listed once Table 1 is complete and effluent hardness entered. Use a default value of 25 mg/L if no hardness data is available.                          Second, the Dissolved Metal allocations are divided by the Translators to determine the Total Metals that can be allocated to the Permittee. These Total Metals values are automatically inserted into Table 2 and are the allowable Total Metal allocations determined for the Permittee prior to allowing for dilution. See Input sheet Table 2. The final acute and chronic values shown under the RPA sheet are the Total Metal values listed in Table 2 divided by the acute and chronic IWC, respectively.       2) The Translatorsused in the freshwater RPA are the Partition Coefficients published by US EPA in 1984. They are TSS dependent equations and can be found listed with the WQS hardness dependent equations under the sheet labeled Equations. A fixed TSS value of 10 mg/L is used to calculate the Translator values.3)Pretreatment Facilities–PERCS will need a copy of the Dissolved to Total Metal Calculator spreadsheet and the RPA sheet along with the Final Permit.Pretreatment Facilities are required to renew their Headwords Analysis after renewal of their permits. Since all their metal allocations are likely to change PERCS needs to see any new metal permit limits and the allowable allocations for the dissolved metals to assess Maximum Allowable Headworks Loading (MAHL) numbers for each metal based on the Combined Hardness values used in the permit writers RPA calculations.4) For Cadmium, Lead, Nickel, Chromium and Beryllium, if all the effluent sampling data for the last three to five years shows the pollutant at concentrations less than the Practical Quantitative Level (PQL), it is not likely a limit or monitoring will be put in the permit.  However, if the estimated NPDES permit limit is less than the Practical Quantitative Limit (particularly, Cadmium and Lead) and the pollutant is believed to be present, to assess compliance with the new standards and for future permit limit development, monitoring for the pollutant will be required. If the facility is monitoring for the pollutant in its Pretreatment LTMP, no monitoring is needed in the permit.5) For monitoring and compliance purposes if Total 
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MAXIMUM DATA POINTS = 58
REQUIRED DATA ENTRY
Table 2. Parameters of Concern
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RECOMMENDED ACTION
No RP, Predicted Max < 50% of Allowable Cw - No
Monitoring required
No - detects, no monitoring required.
No detectes, all values less than 2.5 ug/L. No
Monitoring required. However, the DWR's POL is 0.5
ug/L. Future sampling should analyze down to 0.5
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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 RP, Predicted Max < 50% of Allowable Cw - No
Monitoring required
No detectes, all values less than 5 ug/L. No
Monitoring required.
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No - RP, Predicted Max < 50% of Allowable Cw - No
Monitoring required
REASONABLE POTENTIAL RESULTS
n # Det, Max Pred Cw Allowable Cw
II Acute (FW): 450.2
Chronic (FW): 208.9
Chronic (HH): 53.5
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Chronic: 7.0
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Chronic: 20.846
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Permit No. NC0036269
Page 1 of 4

NPDES Implementation of Instream Dissolved Metals Standards – Freshwater Standards
The NC 2007-2015 Water Quality Standard (WQS) Triennial Review was approved by the NC
Environmental Management Commission (EMC) on November 13, 2014. The US EPA subsequently
approved the WQS revisions on April 6, 2016, with some exceptions. Therefore, metal limits in draft
permits out to public notice after April 6, 2016 must be calculated to protect the new standards - as
approved.
Table 1. NC Dissolved Metals Water Quality Standards/Aquatic Life Protection
Parameter Acute FW, µg/l
(Dissolved)
Chronic FW, µg/l
(Dissolved)
Acute SW, µg/l
(Dissolved)
Chronic SW, µg/l
(Dissolved)

Arsenic 340 150 69 36
Beryllium 65 6.5 --- ---
Cadmium Calculation Calculation 40 8.8
Chromium III Calculation Calculation --- ---
Chromium VI 16 11 1100 50
Copper Calculation Calculation 4.8 3.1
Lead Calculation Calculation 210 8.1
Nickel Calculation Calculation 74 8.2
Silver Calculation 0.06 1.9 0.1
Zinc Calculation Calculation 90 81

Table 1 Notes:
1. FW= Freshwater, SW= Saltwater
2. Calculation = Hardness dependent standard
3. Only the aquatic life standards listed above are expressed in dissolved form. Aquatic life
standards for Mercury and selenium are still expressed as Total Recoverable Metals due to
bioaccumulative concerns (as are all human health standards for all metals). It is still necessary
to evaluate total recoverable aquatic life and human health standards listed in 15A NCAC
2B.0200 (e.g., arsenic at 10 µg/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/l
Cadmium, Acute WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151 [ln hardness]-3.1485}
Cadmium, Acute Trout waters WER*{1.136672-[ln hardness](0.041838)} ∙ e^{0.9151[ln hardness]-3.6236}
Cadmium, Chronic WER*{1.101672-[ln hardness](0.041838)} ∙ e^{0.7998[ln hardness]-4.4451}
Chromium III, Acute WER*0.316 ∙ e^{0.8190[ln hardness]+3.7256}
Chromium III, Chronic WER*0.860 ∙ e^{0.8190[ln hardness]+0.6848}
Copper, Acute WER*0.960 ∙ e^{0.9422[ln hardness]-1.700}
Copper, Chronic WER*0.960 ∙ e^{0.8545[ln hardness]-1.702}
Lead, Acute WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]-1.460}
Lead, Chronic WER*{1.46203-[ln hardness](0.145712)} ∙ e^{1.273[ln hardness]-4.705}
Nickel, Acute WER*0.998 ∙ e^{0.8460[ln hardness]+2.255}
Nickel, Chronic WER*0.997 ∙ e^{0.8460[ln hardness]+0.0584}
Permit No. NC0036269
Page 2 of 4

Silver, Acute WER*0.85 ∙ e^{1.72[ln hardness]-6.59}
Silver, Chronic Not applicable
Zinc, Acute WER*0.978 ∙ e^{0.8473[ln hardness]+0.884}
Zinc, Chronic WER*0.986 ∙ e^{0.8473[ln hardness]+0.884}

General Information on the Reasonable Potential Analysis (RPA)
The RPA process itself did not change as the result of the new metals standards. However, application of
the dissolved and hardness-dependent standards requires additional consideration in order to establish the
numeric standard for each metal of concern of each individual discharge.
The hardness-based standards require some knowledge of the effluent and instream (upstream) hardness
and so must be calculated case-by-case for each discharge.
Metals limits must be expressed as ‘total recoverable’ metals in accordance with 40 CFR 122.45(c). The
discharge-specific standards must be converted to the equivalent total values for use in the RPA
calculations. We will generally rely on default translator values developed for each metal (more on that
below), but it is also possible to consider case-specific translators developed in accordance with
established methodology.

RPA Permitting Guidance/WQBELs for Hardness-Dependent Metals - Freshwater
The RPA is designed to predict the maximum likely effluent concentrations for each metal of concern,
based on recent effluent data, and calculate the allowable effluent concentrations, based on applicable
standards and the critical low-flow values for the receiving stream.
If the maximum predicted value is greater than the maximum allowed value (chronic or acute), the
discharge has reasonable potential to exceed the standard, which warrants a permit limit in most cases. If
monitoring for a particular pollutant indicates that the pollutant is not present (i.e. consistently below
detection level), then the Division may remove the monitoring requirement in the reissued permit.
1. To perform a RPA on the Freshwater hardness-dependent metals the Permit Writer compiles the
following information:
• Critical low flow of the receiving stream, 7Q10 (the spreadsheet automatically calculates
the 1Q10 using the formula 1Q10 = 0.843 (s7Q10, cfs) 0.993
• Effluent hardness and upstream hardness, site-specific data is preferred
• Permitted flow
• Receiving stream classification

2. In order to establish the numeric standard for each hardness-dependent metal of concern and for
each individual discharge, the Permit Writer must first determine what effluent and instream
(upstream) hardness values to use in the equations.

The permit writer reviews DMR’s, Effluent Pollutant Scans, and Toxicity Test results for any
hardness data and contacts the Permittee to see if any additional data is available for instream
hardness values, upstream of the discharge.

If no hardness data is available, the permit writer may choose to do an initial evaluation using a
default hardness of 25 mg/L (CaCO3 or (Ca + Mg)). Minimum and maximum limits on the
hardness value used for water quality calculations are 25 mg/L and 400 mg/L, respectively.

If the use of a default hardness value results in a hardness-dependent metal showing reasonable
potential, the permit writer contacts the Permittee and requests 5 site-specific effluent and
upstream hardness samples over a period of one week. The RPA is rerun using the new data.

Permit No. NC0036269
Page 3 of 4

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.

4. The numeric standard for each metal of concern is divided by the default partition coefficient (or
site-specific translator) to obtain a Total Recoverable Metal at ambient conditions.

In some cases, where an EPA default partition coefficient translator does not exist (ie. silver), the
dissolved numeric standard for each metal of concern is divided by the EPA conversion factor to
obtain a Total Recoverable Metal at ambient conditions. This method presumes that the metal is
dissolved to the same extent as it was during EPA’s criteria development for metals. For more
information on conversion factors see the June, 1996 EPA Translator Guidance Document.

5. The RPA spreadsheet uses a mass balance equation to determine the total allowable concentration
(permit limits) for each pollutant using the following equation:

Ca = (s7Q10 + Qw) (Cwqs) – (s7Q10) (Cb)
Qw
Where: Ca = allowable effluent concentration (µg/L or mg/L)
Cwqs = NC Water Quality Standard or federal criteria (µg/L or mg/L)
Cb = background concentration: assume zero for all toxicants except NH3* (µg/L or mg/L)
Qw = permitted effluent flow (cfs, match s7Q10)
s7Q10 = summer low flow used to protect aquatic life from chronic toxicity and human
health through the consumption of water, fish, and shellfish from noncarcinogens (cfs)
* Discussions are on-going with EPA on how best to address background concentrations

Flows other than s7Q10 may be incorporated as applicable:
1Q10 = used in the equation to protect aquatic life from acute toxicity
EPA default partition coefficients or the “Fraction Dissolved” converts the value for
dissolved metal at laboratory conditions to total recoverable metal at in-stream
ambient conditions. This factor is calculated using the linear partition coefficients
found in The Metals Translator: Guidance for Calculating a Total Recoverable
Permit Limit from a Dissolved Criterion (EPA 823-B-96-007, June 1996) and the
equation:

_Cdiss__ = _______1_______________
Ctotal 1 + { [Kpo] [ss(1+a)] [10-6] }

Where:
ss = in-stream suspended solids concentration [mg/l], minimum of 10 mg/L used,
and
Kpo and a = constants that express the equilibrium relationship between dissolved
and adsorbed forms of metals. A list of constants used for each hardness-dependent
metal can also be found in the RPA program under a sheet labeled DPCs.

Permit No. NC0036269
Page 4 of 4

QA = used in the equation to protect human health through the consumption of water,
fish, and shellfish from carcinogens
30Q2 = used in the equation to protect aesthetic quality

6. The permit writer enters the most recent 2-3 years of effluent data for each pollutant of concern.
Data entered must have been taken within four and one-half years prior to the date of the permit
application (40 CFR 122.21). The RPA spreadsheet estimates the 95th percentile upper
concentration of each pollutant. The Predicted Max concentrations are compared to the Total
allowable concentrations to determine if a permit limit is necessary. If the predicted max exceeds
the acute or chronic Total allowable concentrations, the discharge is considered to show
reasonable potential to violate the water quality standard, and a permit limit (Total allowable
concentration) is included in the permit in accordance with the U.S. EPA Technical Support
Document for Water Quality-Based Toxics Control published in 1991.

7. When appropriate, permit writers develop facility specific compliance schedules in accordance
with the EPA Headquarters Memo dated May 10, 2007 from James Hanlon to Alexis Strauss on
40 CFR 122.47 Compliance Schedule Requirements.

8. The Total Chromium NC WQS was removed and replaced with trivalent chromium and
hexavalent chromium Water Quality Standards. As a cost savings measure, total chromium data
results may be used as a conservative surrogate in cases where there are no analytical results
based on chromium III or VI. In these cases, the projected maximum concentration (95th %) for
total chromium will be compared against water quality standards for chromium III and
chromium VI.

9. Effluent hardness sampling and instream hardness sampling, upstream of the discharge, are
inserted into all permits with facilities monitoring for hardness-dependent metals to ensure the
accuracy of the permit limits and to build a more robust hardness dataset.

10. Hardness and flow values used in the Reasonable Potential Analysis for this permit included:

Parameter Value Comments (Data Source)
Average Effluent Hardness (mg/L)
[Total as, CaCO3 or (Ca+Mg)] 139.47 DMRs
Average Upstream Hardness (mg/L)
[Total as, CaCO3 or (Ca+Mg)] 50.33 DMRs
7Q10 summer (cfs) 1.80 BIMS
1Q10 (cfs) 1.51 Calculated from 7Q10
Permitted Flow (MGD) 12.0 BIMS

Date: 7/9/2021

Permit Writer: Min Xiao
7/9/21WQS = 12 ng/LV:2017‐1Facility Name: Total Mercury 1631E PQL = 0.5 ng/L7Q10s = 20.700 cfs WQBEL = 18.05 ng/LDate Modifier Data Entry Value Permitted Flow = 26.500 47 ng/L02/12/15 13.413.405/14/15 17.517.508/06/15 15.315.309/03/15 12.512.511/17/15 6.76.7 13.1 ng/L ‐ Annual Average for 201502/02/16 2.12.105/03/16 303008/02/16 < 10.511/01/16 2.62.6 8.8 ng/L ‐ Annual Average for 201602/21/17 2.32.305/03/17 1.71.708/01/17 < 10.511/07/17 2.62.6 1.8 ng/L ‐ Annual Average for 201702/13/18 1.11.105/08/18 1.41.408/08/18 < 10.511/20/18 < 10.5 0.9 ng/L ‐ Annual Average for 201803/19/19 2.32.305/21/19 2.52.508/07/19 3.63.6 2.8 ng/L ‐ Annual Average for 2019Rocky River Regional WWTP No Limit RequiredMERCURY WQBEL/TBEL EVALUATIONMMP Required
7/9/21WQS = 12 ng/LV:2017‐1Facility Name: Total Mercury 1631E PQL = 0.5 ng/L7Q10s = 20.700 cfs WQBEL = 17.34 ng/LDate Modifier Data Entry Value Permitted Flow = 30.000 47 ng/L02/12/15 13.413.405/14/15 17.517.508/06/15 15.315.309/03/15 12.512.511/17/15 6.76.7 13.1 ng/L ‐ Annual Average for 201502/02/16 2.12.105/03/16 303008/02/16 < 10.511/01/16 2.62.6 8.8 ng/L ‐ Annual Average for 201602/21/17 2.32.305/03/17 1.71.708/01/17 < 10.511/07/17 2.62.6 1.8 ng/L ‐ Annual Average for 201702/13/18 1.11.105/08/18 1.41.408/08/18 < 10.511/20/18 < 10.5 0.9 ng/L ‐ Annual Average for 201803/19/19 2.32.305/21/19 2.52.508/07/19 3.63.6 2.8 ng/L ‐ Annual Average for 2019Rocky River Regional WWTP No Limit RequiredMERCURY WQBEL/TBEL EVALUATIONMMP Required
7/9/21WQS = 12 ng/LV:2017‐1Facility Name: Total Mercury 1631E PQL = 0.5 ng/L7Q10s = 20.700 cfs WQBEL = 16.71 ng/LDate Modifier Data Entry Value Permitted Flow = 34.000 47 ng/L02/12/15 13.413.405/14/15 17.517.508/06/15 15.315.309/03/15 12.512.511/17/15 6.76.7 13.1 ng/L ‐ Annual Average for 201502/02/16 2.12.105/03/16 303008/02/16 < 10.511/01/16 2.62.6 8.8 ng/L ‐ Annual Average for 201602/21/17 2.32.305/03/17 1.71.708/01/17 < 10.511/07/17 2.62.6 1.8 ng/L ‐ Annual Average for 201702/13/18 1.11.105/08/18 1.41.408/08/18 < 10.511/20/18 < 10.5 0.9 ng/L ‐ Annual Average for 201803/19/19 2.32.305/21/19 2.52.508/07/19 3.63.6 2.8 ng/L ‐ Annual Average for 2019Rocky River Regional WWTP No Limit RequiredMERCURY WQBEL/TBEL EVALUATIONMMP Required
Rocky River Regional WWTPMercury Data Statistics (Method 1631E)2015 2016 2017 2018 2019# of Samples 5 4 4 4 3Annual Average, ng/L 13.1 8.8 1.8 0.9 2.8Maximum Value, ng/L 17.50 30.00 2.60 1.40 3.60TBEL, ng/LWQBEL, ng/L 18.0 (26.5 MGD) / 17.3 (30 MGD) / 16.7 (34 MGD)47
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