NC0030210_Fact Sheet_20191219

Fact Sheet
NPDES Permit No. NCO030210
Permit Writer/Email Contact Nick Coco, [e-mail]:
Date: April 25, 2019
Division/Branch: NC Division of Water Resources/NPDES Complex Permitting
Fact Sheet Template: Version 09Jan2017
Permitting Action:
❑ Renewal
® Renewal with Expansion
❑ New Discharge
❑ Modification (Fact Sheet should be tailored to mod request)
Note: A complete application should include the following:
• For New Dischargers, EPA Form 2A or 2D requirements, Engineering Alternatives Analysis, Fee
• For Existing Dischargers (POTW), EPA Form 2A, 3 effluent pollutant scans, 4 2nd species WET
tests.
• For Existing Dischargers (Non-POTW), EPA Form 2C with correct analytical requirements based
on industry category.
Complete applicable sections below. If not applicable, enter NA.
1. Basic Facility Information
Facility Information
Applicant/Facility Name:
Charlotte Water/Mallard Creek Water Reclamation Facility (WRl
Applicant Address:
5100 Brookshire Boulevard, Charlotte, NC 28216
Facility Address:
12400 US Highway 29 North, Charlotte, NC 28262
Permitted Flow:
12.0 MGD/Expansions to 13.1 MGD, 14.9 MGD and 16.0 MGD
Facility Type/Waste:
MAJOR Municipal; 98.3% domestic, 1.7% industrial
Facility Class:
Grade IV Biological Water Pollution Control System (WPCS)
Treatment Units:
Influent pump station, mechanical bar screens, two vortex grit removal
basins, two flow equalization day tanks, intermediate pumping station,
five primary clarifiers, three biological treatment trains, anoxic zones
and aeration with internal recycle, four final clarifiers, four traveling
bridge tertiary filters, UV disinfection and re -aeration, reuse
distribution, anaerobic digesters, a sludge holding tank, a waste
thickening centrifuge, sludge drying beds, three standby power
generators
Pretreatment Program (Y/l)
Y
County:
Mecklenburg
Region
Mooresville
Briefly describe the proposed permitting action and facility background: Charlotte Water applied for an
NPDES permit renewal at 12.0 MGD for the Mallard Creek WRF in June 2018. At this time, the
Permittee informed the Division of intent to expand their facility. The Permittee formally requested the
addition of an expansion limitation page to 13.1 MGD, 14.9 MGD and 16.0 MGD in February 2019. An
Engineering Alternatives Analysis was submitted to the Division for their expansion in January 2019.
Page 1 of 16

Speculative effluent limits for the proposed expansions to 14.9 MGD and 16.0 MGD were provided in
February 2019 based on Division review of receiving stream conditions and water quality modeling
results.
The facility serves a population of 195,951 residents, with 3 categorical significant industrial users (CIUs)
and a pretreatment program. Treated domestic and industrial wastewater is discharged into Mallard
Creek, a class C waterbody in the Yadkin -Pee Dee River Basin. The facility's discharge takes up
essentially all of the available assimilative capacity for oxygen consuming wastes in Mallard Creek with
an IWC of 97% at 12 MGD. Mallard Creek is not listed on the North Carolina 303(d) Impaired Waters
List. Mallard Creek has a summer 7Q 10 of 0.64 cfs and discharges into the Rocky River.
Charlotte Water currently has 33 MGD (maximum day basis) Interbasin Transfer (IBT) certificate. The
transfer is based on water withdrawals from Lake Norman and Mountain Island Lake in the source basin
(Catawba River Basin). The transfer of the water to the receiving basin (Rocky River Basin) is via
consumptive use in eastern Mecklenburg County and existing discharges at Mallard Creek Wastewater
Treatment Plant [WWTP] and Water and Sewer Authority of Cabarrus County's [WSACC] Rocky River
Regional (RRR) WWTP.
Receiving Waterbody Information:
Receiving Waterbody Information
Outfalls/Receiving Stream(s):
Outfall 001 Mallard Creek
Stream Segment:
13-17-5
Stream Classification:
C
Drainage Area (mi2):
37.5
Summer 7Q10 (cfs)
0.64
Winter 7Q10 (cfs):
2.1
30Q2 (cfs):
2.9
Average Flow (cfs):
41
IWC (% effluent):
97% at 12.0 MGD
303(d) listed/parameter:
Yes, the segment is listed in the 2018 303(d) for Copper
impairment
Subject to TMDL/parameter:
Yes- State wide Mercury TMDL implementation.
Basin/Sub-basin/HUC:
Yadkin -Pee Dee/03-07-11/03040105
USGS Topo Quad:
F15SW
Page 2 of 16

3. Effluent Data Summary
Effluent data for Outfall 001 is summarized below for the period of October 2014 through March 2019.
Table 1. Effluent Data Summary Outfall 001
Parameter
Units
Average
Max
Min
Permit
Limit
Flow
MGD
9.2
20.6
6.0
MA 12.0
CBOD summer
mg/l
2.2
4.7
2
WA 6.3
MA 4.2
CBOD winter
mg/l
2.3
9.8
2
WA 12.5
MA 8.3
NH3N summer
mg/1
0.1
0.9
0.1
WA 3.0
MA 1.0
NH3N winter
mg/l
0.2
3
0.1
WA 6.0
MA 2.0
TSS
mg/1
3.3
11.8
2.5
WA 45.0
MA 30.0
pH
SU
6.9
7.4
6.2
6.0 < pH <
9.0
(geometric)
Fecal coliform
#/100 ml
1.5
280
1
WA 400
MA 200
DO
mg/l
8.5
9.9
7.5
DA > 6.0
Temperature
° C
21.6
27.7
13.4
TN
mg/l
17.7
22.4
11.7
TP
mg/l
3.6
4.7
1.7
Total Zinc
ug/l
39.6
54
18
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 temperature and dissolved oxygen monitoring. Data
Page 3 of 16

pertaining to temperature and dissolved oxygen were provided by the Permittee. Upstream sampling was
conducted at Pavillion Boulevard and downstream sampling was conducted both at NCSR 1300 (Dl) and
NCSR 1304 (D2).
Students t-tests were run at a 95% confidence interval to analyze relationships between instream
samples. A statistically significant difference is determined when the t-test p-value result is < 0.05.
During this analysis, which utilized data ranging from April 2016 to February 2019, it was concluded that
downstream temperature ranged from 7.2 to 26.4 degrees Celsius at location D1 and from 2.6 to 26.8
degrees Celsius at location D2. Upstream temperature ranged from 0.8 to 26 degrees Celsius. The
downstream temperature did not exceed 32 degrees Celsius [per 15A NCAC 02B .0211 (18)] at either
downstream location. The temperature differential between upstream and Dl samples was greater than
2.8 degrees Celsius on 54 occasions during the period reviewed. The temperature differential between
upstream and D2 samples was greater than 2.8 degrees Celsius on 12 occasions during the period
reviewed. Upon review of the effluent on the dates that the temperature differential was high, effluent
temperature was higher than the upstream and both downstream temperatures. A statistically significant
difference exists between upstream and D1 temperature and between upstream and D2 temperature.
Effluent temperature appears to influence downstream temperature, especially during the winter months.
The Regional Office has been informed of this impact.
Downstream DO at location D1 ranged from 6.3 to 11.2 mg/L and downstream DO at location D2 ranged
from 6.1 mg/L to 13 mg/L. The upstream DO ranged from 6.0 to 13.7 mg/L. Downstream DO did not
drop below 5 mg/L [per 15A NCAC 02B .0211 (6)] during the period reviewed at either downstream
location. It was concluded that no statistically significant difference exists between upstream and
downstream DO at location D2. However, a statistically significant difference does exist between
upstream and downstream DO at location D1. Upon review of the discharge, effluent DO was
consistently higher than the upstream and both downstream temperatures. While the effluent discharge
may have a possible organic loading impact on DO in the stream, the impact would be minimal since the
average DO at both downstream locations remained above 5 mg/L.
The draft permit maintains the same instream monitoring requirements as the current permit.
Is this facility a member of a Monitoring Coalition with waived instream monitoring (YIN): NO
Name of Monitoring Coalition: l�n
5. Compliance Summary
Summarize the compliance record with permit effluent limits (past 5 years): The facility reported no limit
violations between October 2014 and March 2019.
Summarize the compliance record with aquatic toxicity test limits and any second species test results
(past 5 years): The facility passed 20 of 22 chronic toxicity tests conducted between February 2015 and
May 2019, as well as all 4 of 4 second species chronic toxicity tests conducted between August 2016 and
May 2019. The facility failed its chronic toxicity testing in both May 2015 and February 2016, but in each
case followed up the failures with two straight months of passes. In February 2015, the facility ran a split
test resulting in one report of failure and one result of passing. After further investigation by the DWR's
Aquatic Toxicology Branch, the disagreeing split was deemed a passing result.
Summarize the results from the most recent compliance inspection: The last facility inspection conducted
in February 2019 reported that the facility was compliant.
Page 4 of 16

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 1 SA 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.
Ifpermit limits are more stringent than TBELs, describe how limits were developed: In 1993, DWR
completed a calibrated QUAL2E river model focusing on a 42-mile section towards the upper end of the
Rocky River. Three major municipal discharges were considered in the model: Mooresville WWTP to
Dye Creek, Mallard Creek WWTP to Mallard Creek, and Concord WWTP to Rocky River. The following
set of effluent concentrations were obtained for the Mallard Creek WWTP: DO: 6.0 mg/l, NH3: 1.0 mg/L,
BOD5: 5.0 mg/L (4 mg/L CBOD5), and Flow: 6.0 MGD. At expanded wasteflows, the DO sag is
predicted to occur in the Rocky River. Instream DO violations were not predicted at 12 MGD. Charlotte
Water provided a correlation between BOD5 and CBOD5 at the plant to determine the CBOD5 limit of
4.2 mg/L.
Charlotte Water applied for expansion of their Mallard Creek WRF in February 2019. The expansion
request would include three additional tiers: 13.1 MGD, 14.9 MGD and 16.0 MGD. Based on Division
review of receiving stream conditions and water quality modeling results, speculative limits for the
proposed expansion to 14.9 MGD and 16.0 MGD have been provided. CBOD speculative limits are based
on a 2018 QUAL2K model. The summer monthly average and weekly average speculative limits for
CBOD are 4.2 mg/L and 6.3 mg/L, respectively, at both the 14.9 MGD and 16.0 MGD flow tiers. The
winter monthly average and weekly average speculative limits for CBOD are 8.3 mg/L and 12.5 mg/L,
respectively, at both the 14.9 MGD and 16.0 MGD flow tiers. These limits are consistent with the limits
at the 12.0 MGD flow tier and are therefore also applicable to the 13.1 MGD flow tier.
Updated winter 7Q10 flows were not provided in the initial model report. To apply the winter CBOD
limits, the model was updated with current winter flows from USGS and winter temperatures and
resubmitted to the DWR Modeling Support Branch for approval. The DWR Modeling Support Branch
reviewed and approved the revised modeling files for the winter condition analysis for the Mallard Creek
WRF on 8/6/19. The primary conclusion of the analysis is that the facility's existing winter concentration
limit for CBOD would be fully protective of DO in Mallard Creek and the Rocky River under higher
discharge rates.
Ammonia and Total Residual Chlorine Limitations
Limitations for ammonia are based on protection of aquatic life utilizing an ammonia chronic criterion of
1.0 mg/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.
Page 5 of 16

Limitations for Total Residual Chlorine (TRC) are based on the NC water quality standard for protection
of aquatic life (17 ug/1) and capped at 28 ug/l (acute impacts). Due to analytical issues, all TRC values
reported below 50 ug/l are considered compliant with their permit limit.
Describe any proposed changes to ammonia and/or TRC limits for this permit renewal: Refer to the
Oxygen Consuming Waste section for the description of the model and rationale behind the ammonia
limits. The winter monthly average and weekly average speculative limits for ammonia are 2.0 mg/L and
6.0 mg/L, respectively, at both the 14.9 MGD and 16.0 MGD flow tiers. These limits are consistent with
the limits at the 12.0 MGD flow tier and are therefore also applicable to the 13.1 MGD flow tier. After the
DWR Modeling Support Branch reviewed the revised model with updated winter 7Q 10 flows, the
primary conclusion of the analysis is that the facility's existing winter concentration limit for ammonia
would be fully protective of DO in Mallard Creek and the Rocky River under higher discharge rates. The
ammonia limits at each flow tier have been reviewed in the attached 2019 WLA and have been found to
be protective of the stream.
As the facility employs LTV disinfection and does not add chlorine to any component of the treatment
works, no TRC limit or monitoring requirement is in the permit. No changes are proposed for TRC.
Reasonable Potential Analysis (RPA) for Toxicants
If applicable, conduct RPA analysis and complete information below.
The need for toxicant limits is based upon a demonstration of reasonable potential to exceed water quality
standards, a statistical evaluation that is conducted during every permit renewal utilizing the most recent
effluent data for each outfall. The RPA is conducted in accordance with 40 CFR 122.44 (d) (i). The NC
RPA procedure utilizes the following: 1) 95% Confidence Level/95% Probability; 2) assumption of zero
background; 3) use of/z detection limit for "less than" values; and 4) streamflows used for dilution
consideration based on 15A NCAC 2B.0206. Effective April 6, 2016, NC began implementation of
dissolved metals criteria in the RPA process in accordance with guidance titled NPDES Implementation of
Instream Dissolved Metals Standards, dated June 10, 2016.
A reasonable potential analysis was conducted on effluent toxicant data collected between April 2017 and
February 2019 and on Effluent Pollutant Scan data collected between August 2014 and August
2018. 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 Monitorin . The following parameters will receive a water quality -based
effluent limit (WQBEL) since they demonstrated a reasonable potential to exceed applicable
water quality standards/criteria: NA
• Monitoring Only. The following parameters will receive a monitor -only requirement since they
did not demonstrate reasonable potential to exceed applicable water quality standards/criteria,
but the maximum predicted concentration was >50% of the allowable concentration: NA
• No Limit or Monitoring: The following parameters will not receive a limit or monitoring, since
they did not demonstrate reasonable potential to exceed applicable water quality
standards/criteria and the maximum predicted concentration was <50% of the allowable
discharge concentration: Arsenic, Cadmium, Total Chromium, Copper, Cyanide, Lead,
Molybdenum, Nickel, Selenium, Silver, Zinc
• 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
Page 6 of 16

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
o The following parameter(s) will receive no monitoring requirement, since as part of a
limited data set, no sample exceeded the allowable discharge concentration: Beryllium,
Total Phenolic Compounds
If applicable, attach a spreadsheet of the RPA results as well as a copy of the Dissolved Metals
Implementation Fact Sheet for freshwater/saltwater to this Fact Sheet. Include a printout of the RPA
Dissolved to Total Metal Calculator sheet if this is a Municipality with a Pretreatment Program.
Toxicity Testing Limitations
Permit limits and monitoring requirements for Whole Effluent Toxicity (WET) have been established in
accordance with Division guidance (per WET Memo, 8/2/1999). Per WET guidance, all NPDES permits
issued to Major facilities or any facility discharging "complex" wastewater (contains anything other than
domestic waste) will contain appropriate WET limits and monitoring requirements, with several
exceptions. The State has received prior EPA approval to use an Alternative WET Test Procedure in
NPDES permits, using single concentration screening tests, with multiple dilution follow-up upon a test
failure.
Describe proposed toxicity test requirement: This is a Major POTW, and a chronic WET limit at 90%
effluent at 12.0 MGD flow will continue on a quarterly frequency. Based on Division review of receiving
stream conditions and water quality modeling results provided in the February 2019 speculative limits,
the 14.9 MGD and 16.0 MGD flow tiers will include chronic WET testing requirement at 90% effluent
conducted on a quarterly frequency. As this limit is consistent with the WET limit at 12.0 MGD, the 13.1
MGD flow tier will also include a chronic WET testing requirement at 90% effluent conducted on a
quarterly frequency.
Mercury Statewide TMDL Evaluation
There is a statewide TMDL for mercury approved by EPA in 2012. The TMDL target was to comply
with EPA's mercury fish tissue criteria (0.3 mg/kg) for human health protection. The TMDL established a
wasteload allocation for point sources of 37 kg/year (81 lb/year), and is applicable to municipals and
industrial facilities with known mercury discharges. Given the small contribution of mercury from point
sources (^2% of total load), the TMDL emphasizes mercury minimization plans (MMPs) for point source
control. Municipal facilities > 2 MGD and discharging quantifiable levels of mercury (>1 ng/1) will
receive an MMP requirement. Industrials are evaluated on a case -by -case basis, depending if mercury is a
pollutant of concern. Effluent limits may also be added if annual average effluent concentrations exceed
the WQBEL value (based on the NC WQS of 12 ng/1) and/or if any individual value exceeds a TBEL
value of 47 ng/1
Table 2. Mercury Effluent Data Summary
2016
2017
2018
2019
# of Samples
8
13
12
2
Annual Average Conc. n L
0.6
0.7
1.1
1.2
Maximum Conc., n L
1.5
2.1
3.6
1.2
TBEL, n L
47
WQBEL, n L
12.4
Page 7 of 16

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. While the facility is >2 MGD and reported quantifiable levels of mercury (> 1 ng/lthe
mercury minimization plan requirement has been removed from the permit. As EPA promulgated the
Dental Amalgam Rule (40 CFR Part 441) on June 14, 2017 and the facility has consistently reported
effluent mercury values near 1 ng/L, the Division does not believe the plan is necessary.
Charlotte Water has created a MMP as a requirement for their current NPDES permit. The City developed
an annual report of the mercury removal rate for the Mallard Creek WRF, monitored for mercury in their
plant, surveyed industries, identified potential contributors, conducted educational community outreach,
and assessed best management strategies for handling mercury. See attached for the Mercury
Minimization Plan provided by Charlotte Water for their Mallard Creek WRF.
Other TMDL/Nutrient Management Strategy Considerations
If applicable, describe any other TMDLs/Nutrient Management Strategies and their implementation
within this permit: NA
Other WOBEL 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
1 SA MCA 2H. 0107( c)(2)(B), 40CFR 122.47, and EPA May 2007 Memo: NA
If applicable, describe any water quality standards variances proposed in accordance with NCGS 143-
215.3(e) and 1 SA NCAC 2B.0226 for this permit renewal: NA
7. Technology -Based Effluent Limitations (TBELs)
Municipals (if not applicable, delete and skip to Industrials)
Are concentration limits in the permit at least as stringent as secondary treatment requirements (30 mg1l
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 BOD51TSS included in the permit? YES
If NO, provide a justification (e.g., waste stabilization pond). NA
If any limits are based on best professional judgement (BPJ), describe development: NA
Document any TBELs that are more stringent than WQBELs: NA
Document any TBELs that are less stringent than previous permit: NA
Page 8 of 16

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: The proposed expansion is not subject to review
under the State of North Carolina Environmental Policy Act (SEPA).
An Engineer's Alternatives Analysis (EAA) was submitted by Brown and Caldwell, the consulting firm
hired by Charlotte Water, on January 24, 2019. Division staff concurred with the projected flow
justification as well as the alternatives analysis. Division staff concurred with the projected flow needs
based on a 21-year planning horizon. The Mallard Creek WRF treats wastewater for a population of
195,951 Charlotte residents in the northern part of Mecklenburg county. Between 2010 and 2018,
Charlotte has experienced a 15% population growth. In the EAA, Brown and Caldwell modeled
population growth to 2070. Division staff concurs with the modelled population growth provided by
Brown and Caldwell as it is consistent with the 2010 — 2017 North Carolina Office of State Budget and
Management population growth extrapolated out to 2070.
The following alternatives were evaluated for the expanded flow:
Alternative Description
20- ear NPV
No Action.
N/A
Expand MCWRF and Mallard Creek Surface Water Discharge b 4 MGD.
$94,960,000
Purchase 4 MGD of additional capacity from WSACC and convey wastewater from Mallard
Creek WRF to Rocky River Regional WWTP (RRRWWTP) through the Fuda Creek
$123,500,000
Interceptor.
Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of additional capacity from
WSACC and convey all Back Creek Flow to WSACC's RRRWWTP through the Fuda Creek
$107,590,000
Interceptor.
Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of additional capacity from
WSACC and convey all Back Creek Flow to WSACC's RRRWWTP through a New Back
$115,540,000
Creek Parallel Sewer.
Convey 4 MGD of wastewater from the Mallard Creek Basin to CLTWater's McDowell Creek
VW.
$110,260,000
Expand MCWRF and land apply 4 MGD of treated effluent.
$275,320,000
Expand MCWRF and reuse 4 MGD of treated effluent.
278,790,000
The most economically feasible and chosen option was the expansion of MCWRF and Mallard Creek
Surface Water Discharge by 4 MGD. The Division has reviewed the alternatives and concurs with this
decision.
9. Antibacksliding Review:
Sections 402(o)(2) and 303(d)(4) of the CWA and federal regulations at 40 CFR 122.44(1) prohibit
backsliding of effluent limitations in NPDES permits. These provisions require effluent limitations in a
reissued permit to be as stringent as those in the previous permit, with some exceptions where limitations
may be relaxed (e.g., based on new information, increases in production may warrant less stringent TBEL
limits, or WQBELs may be less stringent based on updated RPA or dilution).
Page 9 of 16

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.
Charlotte Water was granted monitoring frequency reductions for CBOD5, Total Suspended Solids, NH3-
N and Fecal Coliform in their December 2013 NPDES permit renewal based on DWR Guidance
Regarding the Reduction of Monitoring Frequencies in NPDES Permits for Exceptionally Performing
Facilities. The last three years of the facility's data for these parameters have been reviewed. No changes
are proposed to the 2/week monitoring frequency requirements for CBOD5, Total Suspended Solids,
NH3-N and Fecal Coliform.
11. Electronic Reporting Requirements
The US EPA NPDES Electronic Reporting Rule was finalized on December 21, 2015. Effective
December 21, 2016, NPDES regulated facilities are required to submit Discharge Monitoring Reports
(DMRs) electronically. Effective December 21, 2020, NPDES regulated facilities will be required to
submit additional NPDES reports electronically. This permit contains the requirements for electronic
reporting, consistent with Federal requirements.
12.Summary of Proposed Permitting Actions:
Table 3. Current Permit Conditions and Proposed Changes 12.0 MGD
Parameter
Current Permit
Proposed Change
Basis for Condition/Change
Flow
MA 12.0 MGD
MA 12.0 MGD with
15A NCAC 2B .0505; Expansion
expansion pages for
application and EAA Review;
13.1 MGD, 14.9 MGD
Results of 2018-19 QUAL2K model
and 16.0 MGD
CBOD5
Summer:
No change
WQBEL. Based on 1993 calibrated
MA 4.2 mg/1
QUAL2E model results and 2018-19
WA 6.3 mg/1
QUAL2K model results. Protection
Winter:
of DO standard 15A NCAC 02B
MA 8.3 mg/1
.0200
WA 12.5 mg/1
Page 10 of 16

NH3-N
Summer:
No change
WQBEL. Based on 1993 calibrated
MA 1 mg/l
QUAL2E model results and 2018-19
WA 3 mg/1
QUAL2K model results. Protection
Winter:
of DO standard 15A NCAC 02B
MA 2 mg/1
.0200
WA6myl
TSS
MA 30 mg/l
No change
TBEL. Secondary treatment
WA 45 mg/l
standards/40 CFR 133 / 15A NCAC
2B .0406
Fecal coliform
MA 200 /100ml
No change
WQBEL. State WQ standard, 15A
WA 400 /100m1
NCAC 2B .0200
DO
> 6 mg/1
No change
WQBEL. Based on 1993 calibrated
QUAL2E model results and 2018-19
QUAL2K model results.
Temperature
Monitor Daily
No change
15A NCAC 2B .0508 — Surface
Water Monitoring: Reporting
pH
6 — 9 SU
No change
WQBEL. State WQ standard, 15A
NCAC 2B .0200
Total Nitrogen
Monitor Monthly
No change
15A NCAC 2B .0508 — Surface
Water Monitoring: Reporting
Total Phosphorus
Monitor Monthly
No change
15A NCAC 2B .0508 — Surface
Water Monitoring: Reporting
Total Zinc
Monitor Quarterly
Requirement removed
Based on RPA Results; No RP,
Predicted Max < 50% of Allowable
Cw - No Monitoring required
Total Hardness
No requirement
Quarterly monitoring
In accordance with NPDES guidance
Upstream and in
on Implementing Instream Dissolve
Effluent
Metals Standards for Freshwater —
Pretreatment POTW sampling for
hardness -dependent metals in LTMP
Toxicity Test
Chronic limit, 90%
No change
WQBEL. No toxics in toxic
effluent
amounts. 15A NCAC 213.0200 and
15A NCAC 2B.0500
Effluent Pollutant
Three times per permit
No change
40 CFR 122
Scan
cycle
Mercury
MMP Special Condition
Condition removed
Consistent with 2012 Statewide
Minimization Plan
Mercury TMDL Implementation.
(MMP)
Electronic
Electronic Reporting
No change
In accordance with EPA Electronic
Reporting
Special Condition
Reporting Rule 2015.
MGD — Million gallons per day, MA - Monthly Average, WA — Weekly Average, DM — Daily Max
Page 11 of 16

13. Public Notice Schedule:
Permit to Public Notice: 09/04/2019
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
Nick Coco at [phone] or via email at nick.coco6ftcdenr.goy
15. Fact Sheet Addendum (if applicable):
Charlotte Water submitted the following comments on October 2, 2019:
PERMIT
1) Page 1 and Page 2 - Charlotte Mecklenburg Utility Department
The references to Charlotte Mecklenburg Utility Department on page 1 and page 2 of the permit need to
be replaced with Charlotte Water.
Response: The change has been made and will be reflected in the final permit.
2) Pages 3, 5, 6, and 7 - Footnote 2. Reference to Downstream Sampling Locations
This footnote states: "Sample locations: Upstream at Pavillion Boulevard and downstream at NCSR 1300
and at NCSR 1304." This footnote should state: "Upstream at Pavilion Boulevard and downstream at
NCSR 1300 and at Hwy 49." CLTWater requested minor modification of our permit to move our second
downstream monitoring location from NCSR 1304 to Hwy 49. This was due to safety concerns, and
NCDWR granted the request during our last permit cycle.
Response: The change has been made and will be reflected in the final permit.
3) Pages 4, 5, 6, and 7 -Footnote 6. Effluent Hardness sampling shall be performed in conjunction
with testing for hardness dependent metals.
CLTWater is requesting that this narrative requirement and its corresponding Footnote 6 be removed from
our final permit. CLTWater routinely samples hardness and metals at a frequency greater than quarterly,
usually weekly or monthly for metals and monthly for hardness. We would like to continue our current
sampling protocols and maintain the ability to obtain additional hardness and metals samples
independently of one another. This request is based on our concern about possible third -party
interpretation of this requirement as it is currently written. This requirement could be interpreted as a
monitoring requirement and it could be perceived as a monitoring violation if one of these parameters is
sampled without the other when additional sampling is performed. Additionally, our Effluent Pollutant
Page 12 of 16

Scan already requires us to sample for both hardness and the hardness -based metals in the same sampling
event at least once per year.
CLTWater does not understand the technical rationale or the statutory basis for the requirement to sample
hardness at the same time as metals. The relevant state guidance ("NPDES Implementation of lnstream
Dissolved Metals Standards - Freshwater Standards") calls for the insertion of hardness monitoring into
permits but does not specify a requirement to have these results be paired. It is our understanding that
NCDWR uses average upstream and effluent hardness and average effluent metals concentrations from
the facility data set to determine metals limits rather than calculating limits based on individual daily
results. Since only the average hardness and average metals values are used to determine metals limits
then the requirement to sample hardness in conjunction with metals on the same day is unnecessary and
creates additional opportunity for monitoring and reporting violations to occur. Without technical or
statutory justification(s) CLTWater requests that this requirement be removed from the permit.
Response: Per the 2016 NPDES Implementation of Instream Dissolved Metal Standards memo, a
footnote stating, "Effluent hardness sampling should be performed in conjunction with testing for
hardness dependent metals (cadmium, copper, lead, nickel, silver, and zinc)," should be added to permits
with effluent hardness sampling requirements. For clarification, when quarterly hardness sampling is
conducted, as required in the permit, the sampling shall be performed in conjunction with hardness -
dependent metals sampling. Should Charlotte Water sample for metals more frequently than quarterly, the
extra samples need not be sampled in conjunction with hardness.
4) Page 4, 5, 6, and 8 - Footnote 7 and Section A.(5.) Narrative - Required Months to Conduct
Chronic Toxicity.
The specific months for Chronic Toxicity Testing in Footnote 7 and in the narrative of Section A.(5.)
indicate that toxicity testing must occur in the months of March, June, September, and December.
February, May, August, and November are our required months to perform Toxicity Testing in Mallard's
current permit and a schedule has been created and dates have already been approved by our subcontract
labs for testing during these months. CLTWater is requesting that our required months for Toxicity
testing remain the same for this permit cycle. Since CLTWater has 6 facilities that require Chronic
Toxicity testing, maintaining the current schedule will help to balance this workload with our contract
labs.
Response: The change has been made and will be reflected in the final permit.
5) Pages 4, 5, 6,8 -Statement that Addresses Floating Solids and Visible Foam Discharge
The statement "There shall be no discharge of floating solids or foam visible in other than trace amounts"
is ambiguous and open to interpretation. This statement is more stringent and subjective in its use of
"trace amounts" phrasing than the language used in the Water Quality Standards for Class C Waters (15A
NCAC 02B .0211 (8)). CLTWater requests that this more stringent narrative limit be removed from this
permit. This request is based on our concern of possible third -party interpretation of this requirement as it
is currently written since "trace amounts" is not defined in the permit. The Water Quality Standard is
more appropriate and objective with regard to regulating this wastewater discharge characteristic when it
establishes that "Floating solids ... Shall not make the water unsafe or unsuitable for aquatic life and
wildlife or impair the waters for any designated uses." DWR has removed this statement at our request for
CL TWater's other recently renewed NPDES permits (Irwin, Sugar, McAlpine).
Page 13 of 16

Response: This has been standard language in NPDES permits since the program's inception and is still
used widely by state and federal permitting authorities. Because it is subjective, it is hardly suitable as the
basis for an enforcement action; instead, we would rely on the permittee's monitoring reports to establish
and quantify any limits exceedances. Part of its value is that it provides a quick measure of effluent
quality and possible water quality impacts. A DWR inspector who notices such an issue at a discharge can
address the matter while on site rather than waiting days or weeks for effluent monitoring to be reported.
The Division removed this language from other Charlotte Water permits in error and will restore it when
those permits are renewed.
6) Page 7 - A. (4) Effluent Limitations and Monitoring Requirements (16.0 MGD)
In the table and under Chronic Toxicity Effluent Limits "See Note 5." Needs to be changed to
"See Note 7."
Response: The change has been made and will be reflected in the final permit.
7) Page 11- A.(8.) Mercury Minimization Plan
CLTWater is requesting that the requirement to have a Mercury Minimization Plan be excluded from this
permit. The fact sheet states that no annual average mercury concentration exceeded the WQBEL and no
individual mercury sample exceeded the TBEL. Furthermore, with the recent implementation of the
Dental Amalgam Rule adequate protections are in place to protect water quality.
Response: As EPA promulgated the Dental Amalgam Rule (40 CFR Part 441) on June 14, 2017 and the
facility has consistently reported effluent mercury values near 1 ng/L, the Division has decided to grant
this request. The MMP Special Condition A.(8.) has been removed from the final permit.
8) Page 12 - A.(9.) Electronic Reporting Of Monitoring Reports
CLTWater requests that the following language be removed from Part I of our permit. It should be
included in Part II of our permit after formal approval and incorporation into a revision of the standard
conditions. Furthermore, this language is problematic if DWR is not ready to receive this data
electronically by this date. This language is found at the bottom of page 12 and states:
Starting on December 21, 2020, the permittee must electronically report the following compliance
monitoring data and reports, when applicable:
Sewer Overflow/Bypass Event Reports;
Pretreatment Program Annual Reports; and
Clean Water Act (CWA) Section 316(b) Annual Reports
Response: The EPA's Electronic Reporting Rule was published in the Federal Register on October 22,
2015 and laid out a 2-phase compliance schedule for implementation of the rule. The EPA plans to
propose changing the deadline for implementation of Phase 2 from December 21, 2020 to December 21,
2023 (see 40 CFR § 127.16 Table I). The EPA believes this will provide enough time for the EPA and
states to build most if not all the necessary electronic reporting tools and systems for Phase 2
implementation. However, the schedule in the existing regulation remains in effect and will continue to be
applied state- and nationwide until EPA's revisions are published as a final rule. As such, the Phase 2
requirements in Special Condition A. (9.) Electronic Reporting of Monitoring Reports will remain in the
permit.
Page 14 of 16

MAP
9) Map Title
The current title of the facility location map is "CMU - Mallard Creek WRF - NC0030210. This needs to
be updated to "Charlotte Water - Mallard Creek WRF - NC0030210.
Response: The change has been made and will be reflected in the final map.
FACTSHEET
10) Page 2 - Charlotte -Mecklenburg Utilities (CMUD)
At the beginning of the third paragraph Charlotte -Mecklenburg Utilities (CMUD) needs to be changed to
Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet.
11) Page 2 - Charlotte -Mecklenburg Utilities (CMUD)
At the beginning of the third paragraph Charlotte -Mecklenburg Utilities (CMUD) needs to be changed to
Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet
12) Page 5 - Charlotte -Mecklenburg Utilities
In the last sentence at the end of the second paragraph, under the Oxygen -Consuming Waste Limitations
section, the reference to Charlotte Mecklenburg Utilities needs to be changed to Charlotte Water.
At the beginning of the third paragraph Charlotte water needs to be changed to Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet.
13) Components to be added to Draft Permit and Fact Sheet
On page 2 of the draft permit and on page 1 of Mallard's fact sheet the following items need to be
updated:
• 5.0 MG Storm Equalization Basin is not listed and needs to be added.
• Three final clarifiers are listed but it should be four final clarifiers
• Two travelling bridge filters are listed but it should be four travelling bridge filters
Response: The change has been made and will be reflected in the final permit and fact sheet.
The draft permit was also submitted to the EPA Region 4, Mooresville Regional Office, DWR Operator
Certification Program, DWR Aquatic Toxicology Branch, Mecklenburg County Health, NCWRC and
USFWS. EPA Region 4 requested and was provided clarification of a total nitrogen typographical error in
the fact sheet. Incorrect values were entered into the effluent summary table for total nitrogen. These
errors have been corrected in the final fact sheet. The DWR Aquatic Toxicology Branch commented on
the required months to conduct chronic toxicity monitoring and the changing of the chronic toxicity
footnote in Table A. (4.) as well. The errors have been corrected in the final permit. No comments were
received from all other parties.
Page 15 of 16

Were there any changes made since the Draft Permit was public noticed (Yes/No): YES
If Yes, list changes and their basis below:
All references to Charlotte Mecklenburg Utilities Department (CMUD) in the permit have been
changed to Charlotte Water to reflect the Permittee's name change.
As EPA promulgated the Dental Amalgam Rule (40 CFR Part 441) on June 14, 2017 and the
facility has consistently reported effluent mercury values near 1 ng/L, the MMP Special
Condition A.(8.) has been removed.
The months during which chronic toxicity testing is required have been corrected.
16. Fact Sheet Attachments (if applicable):
• RPA Spreadsheet Summary
• Dissolved Metals Implementation/Freshwater
• Mercury TMDL Evaluation
• NPDES Speculative Limits Letter
• 2018-19 QUAL2K Summary
• Monitoring Frequency Reduction Evaluation
• Instream Monitoring Summary
• Aquatic Toxicity Summary
• Inspection Summary
• Mercury Minimization Plan
Page 16 of 16

CHARLOTTE
W6TER
September 26, 2019
ATTN: Mr. Nick Coco (via Federal Express and electronic mail)
NCDEQ/DWR
WQ Permitting Section
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Charlotte Water Comments on Draft NPDES Permit NCO030210
Mallard Creek Water Reclamation Facility;
Mecklenburg County, NC
SIC 4952, Grade IV Facility
Mr. Coco:
The purpose of this letter is to provide comments on the Mallard Creek NPDES draft permit NCO030210
("Draft Permit'). CLTWater is providing the following comments on the Draft Permit for your consideration
in the final permit:
1) Page 1 and Page 2 — Charlotte Mecklenburg Utility Department
The references to Charlotte Mecklenburg Utility Department on page 1 and page 2 of the permit
need to be replaced with Charlotte Water.
2) Pages 3. 5. 6. and 7 — Footnote 2. Reference to Downstream Samplin-g Locations
This footnote states: "Sample locations: Upstream at Pavillion Boulevard and downstream at
NCSR 1300 and at NCSR 1304." This footnote should state: "Upstream at Pavilion Boulevard
and downstream at NCSR 1300 and at Hwy 49." CLTWater requested minor modification of our
permit to move our second downstream monitoring location from NCSR 1304 to Hwy 49. This
was due to safety concerns, and NCDWR granted the request during our last permit cycle.
3) Pages 4, 5, 6, and 7 — Footnote 6. Effluent Hardness sampling shall be performed In
coniunction with testing for hardness dependent metals.
CLTWater is requesting that this narrative requirement and its corresponding Footnote 6 be
removed from our final permit. CLTWater routinely samples hardness and metals at a frequency
greater than quarterly, usually weekly or monthly for metals and monthly for hardness. We would
like to continue our current sampling protocols and maintain the ability to obtain additional
hardness and metals samples independently of one another. This request is based on our
concern about possible third -party interpretation of this requirement as it is currently written. This
requirement could be interpreted as a monitoring requirement and it could be perceived as a
monitoring violation if one of these parameters is sampled without the other when additional
sampling is performed. Additionally, our Effluent Pollutant Scan already requires us to sample for
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
Operated by the City of Charlotte

both hardness and the hardness -based metals in the same sampling event at least once per
year.
CLTWater does not understand the technical rationale or the statutory basis for the requirement
to sample hardness at the same time as metals. The relevant state guidance ("NPDES
Implementation of Instream Dissolved Metals Standards — Freshwater Standards") calls for the
insertion of hardness monitoring into permits but does not specify a requirement to have these
results be paired. It is our understanding that NCDWR uses average upstream and effluent
hardness and average effluent metals concentrations from the facility data set to determine
metals limits rather than calculating limits based on individual daily results. Since only the
average hardness and average metals values are used to determine metals limits then the
requirement to sample hardness in conjunction with metals on the same day is unnecessary and
creates additional opportunity for monitoring and reporting violations to occur. Without technical
or statutory justification(s) CLTWater requests that this requirement be removed from the permit.
4) Page 4 5 6 and 8 - Footnote 7 and Section A. 5. Narrative — Reclullred Months'to Conduct
Chronic Toxicity.
The specific months for Chronic Toxicity Testing in Footnote 7 and in the narrative of Section
A.(5.) indicate that toxicity testing must occur in the months of March, June, September, and
December. February, May, August, and November are our required months to perform Toxicity
Testing in Mallard's current permit and a schedule has been created and dates have already
been approved by our subcontract labs for testing during these months. CLTWater is requesting
that our required months for Toxicity testing remain the same for this permit cycle. Since
CLTWater has 6 facilities that require Chronic Toxicity testing, maintaining the current schedule
will help to balance this workload with our contract labs.
5) Pages 4 5 6 8 -Statement that Addresses Floatin_q Solids and Visible Foam Discharcle
The statement "There shall be no discharge of floating solids or foam visible in other than trace
amounts" is ambiguous and open to interpretation. This statement is more stringent and
subjective in its use of "trace amounts" phrasing than the language used in the Water Quality
Standards for Class C Waters (15A NCAC 02B .0211 (8)). CLTWater requests that this more
stringent narrative limit be removed from this permit. This request is based on our concern of
possible third -party interpretation of this requirement as it is currently written since "trace
amounts" is not defined in the permit. The Water Quality Standard is more appropriate and
objective with regard to regulating this wastewater discharge characteristic when it establishes
that "Floating solids ... Shall not make the water unsafe or unsuitable for aquatic life and wildlife or
impair the waters for any designated uses." DWR has removed this statement at our request for
CLTWater's other recently renewed NPDES permits (Irwin, Sugar, McAlpine).
6) Page 7 — A. 4 Effluent Limitations and Monitoring Requirements 16.0 MGD
In the table and under Chronic Toxicity Effluent Limits "See Note 5." Needs to be changed to
"See Note 7."
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
lb Operated by the City of Charlotte

7) Page 11 - A.(8.1 Mercury Minimization Plan
CLTWater is requesting that the requirement to have a Mercury Minimization Plan be excluded
from this permit. The fact sheet states that no annual average mercury concentration exceeded
the WQBEL and no individual mercury sample exceeded the TBEL. Furthermore, with the recent
implementation of the Dental Amalgam Rule adequate protections are in place to protect water
quality.
8) Pa a 12 - A. %) Electronic, Reporting Of Monitoring Reports
CLTWater requests that the following language be removed from Part I of our permit. It should
be included in Part II of our permit after formal approval and incorporation into a revision of the
standard conditions. Furthermore, this language is problematic if DWR is not ready to receive
this data electronically by this date. This language is found at the bottom of page 12 and states:
Starting on December 21, 2020, the permittee must electronically report the following
compliance monitoring data and reports, when applicable:
• Sewer Overflow/Bypass Event Reports;
• Pretreatment Program Annual Reports; and
• Clean Water Act (CWA) Section 316(b) Annual Reports
9) Map Title
The current title of the facility location map is "CMU — Mallard Creek WRF — NC0030210. This
needs to be updated to "Charlotte Water — Mallard Creek WRF — NC0030210.
CLTWater is also providing the following comments on the Mallard Creek NPDES Permit Fact Sheet for
your consideration:
1) Page 2 — Charlotte -Mecklenburg Utilities (CMUDi
At the beginning of the third paragraph Charlotte -Mecklenburg Utilities (CMUD) needs to be
changed to Charlotte Water.
2) Page 3 — 3. Effluent Data Summary
The Total Nitrogen (TN) results summarized in Table 1. Effluent Data Summary Outfall 001
appear to not be inclusive of our Nitrate/Nitrite results and may need to be updated.
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
I& Operated by the City of Charlotte

3) Page 5 — Charlotte -Mecklenburg Utilities
In the last sentence at the end of the second paragraph, under the Oxygen -Consuming Waste
Limitations section, the reference to Charlotte Mecklenburg Utilities needs to be changed to
Charlotte Water.
At the beginning of the third paragraph Charlotte water needs to be changed to Charlotte Water.
Charlotte Water appreciates your consideration of our comments and requests. If you have any
questions or require further information concerning this letter please feel free to contact Shannon Sypolt,
Water Quality Program Administrator, at [phone], or me at [phone].
Respectfully,
cqVeinepA. Jarrell,InterimDeuty Director, CLTWater
CC: S. Sypolt, CLTWater
H. Eudy, CLTWater
J. Lockler, CLTWater
R. Hargrove, CLTWater
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
0 Operated by the City of Charlotte

Fact Sheet Addendum
The Division received comments from Charlotte Water on October 2, 2019 and provides
the following responses:
1) Page 1 and Page 2 - Charlotte Mecklenburg Utility Department
The references to Charlotte Mecklenburg Utility Department on page 1 and page 2 of the permit need to
be replaced with Charlotte Water.
Response: The change has been made and will be reflected in the final permit.
2) Pages 3, 5, 6, and 7 - Footnote 2. Reference to Downstream Sampling Locations
This footnote states: "Sample locations: Upstream at Pavillion Boulevard and downstream at NCSR 1300
and at NCSR 1304." This footnote should state: "Upstream at Pavilion Boulevard and downstream at
NCSR 1300 and at Hwy 49." CLTWater requested minor modification of our permit to move our second
downstream monitoring location from NCSR 1304 to Hwy 49. This was due to safety concerns, and
NCDWR granted the request during our last permit cycle.
Response: The change has been made and will be reflected in the final permit.
3) Pages 4, 5, 6, and 7 - Footnote 6. Effluent Hardness sampling shall be performed in conjunction
with testing for hardness dependent metals.
CLTWater is requesting that this narrative requirement and its corresponding Footnote 6 be removed from
our final permit. CLTWater routinely samples hardness and metals at a frequency greater than quarterly,
usually weekly or monthly for metals and monthly for hardness. We would like to continue our current
sampling protocols and maintain the ability to obtain additional hardness and metals samples
independently of one another. This request is based on our concern about possible third -party
interpretation of this requirement as it is currently written. This requirement could be interpreted as a
monitoring requirement and it could be perceived as a monitoring violation if one of these parameters is
sampled without the other when additional sampling is performed. Additionally, our Effluent Pollutant
Scan already requires us to sample for both hardness and the hardness -based metals in the same sampling
event at least once per year.
CLTWater does not understand the technical rationale or the statutory basis for the requirement to sample
hardness at the same time as metals. The relevant state guidance ("NPDES Implementation of lnstream
Dissolved Metals Standards - Freshwater Standards") calls for the insertion of hardness monitoring into
permits but does not specify a requirement to have these results be paired. It is our understanding that
NCDWR uses average upstream and effluent hardness and average effluent metals concentrations from
the facility data set to determine metals limits rather than calculating limits based on individual daily
results. Since only the average hardness and average metals values are used to determine metals limits
then the requirement to sample hardness in conjunction with metals on the same day is unnecessary and
creates additional opportunity for monitoring and reporting violations to occur. Without technical or
statutory justification(s) CLTWater requests that this requirement be removed from the permit.
Response: Per the 2016 NPDES Implementation of Instream Dissolved Metal Standards memo, a
footnote stating, "Effluent hardness sampling should be performed in conjunction with testing for
hardness dependent metals (cadmium, copper, lead, nickel, silver, and zinc)," should be added to permits

with effluent hardness sampling requirements. For clarification, when quarterly hardness sampling is
conducted, as required in the permit, the sampling shall be performed in conjunction with hardness -
dependent metals sampling. Should Charlotte Water -sample for metals more frequently than quarterly, the
extra samples need not be sampled in conjunction with hardness.
4) Page 4, 5, 6, and 8 -Footnote 7 and Section A.(5.) Narrative -Required Months to Conduct
Chronic Toxicity.
The specific months for Chronic Toxicity Testing in Footnote 7 and in the narrative of Section A.(5.)
indicate that toxicity testing must occur in the months of March, June, September, and December.
February, May, August, and November are our required months to perform Toxicity Testing in Mallard's
current permit and a schedule has been created and dates have already been approved by our subcontract
labs for testing during these months. CLTWater is requesting that our required months for Toxicity
testing remain the same for this permit cycle. Since CLTWater has 6 facilities that require Chronic
Toxicity testing, maintaining the current schedule will help to balance this workload with our contract
labs.
Response: The change has been made and will be reflected in the final permit.
5) Pages 4, 5, 6, 8 - Statement that Addresses Floating Solids and Visible Foam Discharge
The statement "There shall be no discharge of floating solids or foam visible in other than trace amounts"
is ambiguous and open to interpretation. This statement is more stringent and subjective in its use of
"trace amounts" phrasing than the language used in the Water Quality Standards for Class C Waters (15A
NCAC 02B .0211 (8)). CLTWater requests that this more stringent narrative limit be removed from this
permit. This request is based on our concern of possible third -party interpretation of this requirement as it
is currently written since "trace amounts" is not defined in the permit. The Water Quality Standard is
more appropriate and objective with regard to regulating this wastewater discharge characteristic when it
establishes that "Floating solids ... Shall not make the water unsafe or unsuitable for aquatic life and
wildlife or impair the waters for any designated uses." DWR has removed this statement at our request for
CL TWater's other recently renewed NPDES permits (Irwin, Sugar, McAlpine).
Response: This has been standard language in NPDES permits since the program's inception and is still
used widely by state and federal permitting authorities. Because it is subjective, it is hardly suitable as the
basis for an enforcement action; instead, we would rely on the permittee's monitoring reports to establish
and quantify any limits exceedances. Part of its value is that it provides a quick measure of effluent
quality and possible water quality impacts. A DWR inspector who notices such an issue at a discharge can
address the matter while on site rather than waiting days or weeks for effluent monitoring to be reported.
The Division removed this language from other Charlotte Water permits in error and will restore it when
those permits are renewed.
6) Page 7 - A. (4) Effluent Limitations and Monitoring Requirements (16.0 MGD)
In the table and under Chronic Toxicity Effluent Limits "See Note 5." Needs to be changed to
"See Note 7."
Response: The change has been made and will be reflected in the final permit.

7) Page 11- A.(8.) Mercury Minimization Plan
CLTWater is requesting that the requirement to have a Mercury Minimization Plan be excluded from this
permit. The fact sheet states that no annual average mercury concentration exceeded the WQBEL and no
individual mercury sample exceeded the TBEL. Furthermore, with the recent implementation of the
Dental Amalgam Rule adequate protections are in place to protect water quality.
Response: As EPA promulgated the Dental Amalgam Rule (40 CFR Part 441) on June 14, 2017 and the
facility has consistently reported effluent mercury values near 1 ng/L, the Division has decided to grant
this request. The MMP Special Condition A.(8.) has been removed from the final permit.
8) Page 12 - A.(9.) Electronic Reporting Of Monitoring Reports
CLTWater requests that the following language be removed from Part I of our permit. It should be
included in Part II of our permit after formal approval and incorporation into a revision of the standard
conditions. Furthermore, this language is problematic if DWR is not ready to receive this data
electronically by this date. This language is found at the bottom of page 12 and states:
Starting on December 21, 2020, the permittee must electronically report the following compliance
monitoring data and reports, when applicable:
• Sewer Overflow/Bypass Event Reports;
• Pretreatment Program Annual Reports; and
• Clean Water Act (CWA) Section 316(b) Annual Reports
Response: The EPA's Electronic Reporting Rule was published in the Federal Register on October 22,
2015 and laid out a 2-phase compliance schedule for implementation of the rule. The EPA plans to
propose changing the deadline for implementation of Phase 2 from December 21, 2020 to December 21,
2023 (see 40 CFR § 127.16 Table 1). The EPA believes this will provide enough time for the EPA and
states to build most if not all the necessary electronic reporting tools and systems for Phase 2
implementation. However, the schedule in the existing regulation remains in effect and will continue to be
applied state- and nationwide until EPA's revisions are published as a final rule. As such, the Phase 2
requirements in Special Condition A. (9.) Electronic Reporting of Monitoring Reports will remain in the
permit.
9) Map Title
The current title of the facility location map is "CMU - Mallard Creek WRF - NC0030210. This needs to
be updated to "Charlotte Water - Mallard Creek WRF - NC0030210.
Response: The change has been made and will be reflected in the final map.
FACTSHEET
10) Page 2 - Charlotte -Mecklenburg Utilities (CMUD)
At the beginning of the third paragraph Charlotte -Mecklenburg Utilities (CMUD) needs to be changed to
Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet.

11) Page 2 - Charlotte -Mecklenburg Utilities (CMUD)
At the beginning of the third paragraph Charlotte -Mecklenburg Utilities (CMUD) needs to be changed to
Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet
12) Page 5 - Charlotte -Mecklenburg Utilities
In the last sentence at the end of the second paragraph, under the Oxygen -Consuming Waste Limitations
section, the reference to Charlotte Mecklenburg Utilities needs to be changed to Charlotte Water.
At the beginning of the third paragraph Charlotte water needs to be changed to Charlotte Water.
Response: The change has been made and will be reflected in the final fact sheet.
13) Components to be added to Draft Permit and Fact Sheet
On page 2 of the draft permit and on page 1 of Mallard's fact sheet the following items need to be
updated:
• 5.0 MG Storm Equalization Basin is not listed and needs to be added.
• Three final clarifiers are listed but it should be four final clarifiers
• Two travelling bridge filters are listed but it should be four travelling bridge filters
Response: The change has been made and will be reflected in the final permit and fact sheet.

a CO S74,,
'2 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
14 WASHINGTON, D.C. 20460
yt-t 1101tG,
AUG 2 2 2019
Allison Woodall
President
Association of Clean Water Administrators (ACWA)
1634 1 Street. NW. Suite 4750
Washington, D.C. 20006
Dear Ms. Woodall:
ASSISTANT ADMINISTRATOR
FOR ENFORCEMENT AND
COMPLIANCE ASSURANCE
am writing in response to your recent letter dated July 2, 2019, requesting an extension of the
implementation of Phase 2 of the NPDES Electronic Reporting rule (NPDES eRule). Phase 2 covers
NPDES general permits and program reports. The EPA shares your concerns about the need to
coordinate updates to EPA's data systems with these reporting requirements. Extending the Phase 2
deadline would give the EPA and states more time to develop Phase 2 electronic reporting tools and
systems. Additionally, a NPDES eRule extension would give the EPA and states more time to update
and implement data sharing protocols and related applications for Phase 2 data.
We appreciate all the time and effort ACWA and its members have contributed to the development and
implementation of the NPDES eRule thus far. We will continue to work closely with you to ensure the
NPDES eRule's ultimate goals of burden reduction and resource savings are realized. Therefore, I am
pleased to inform you that the EPA plans to initiate a notice and comment rulemaking to extend the
Phase' deadline and to give states more flexibility in implementing Phase 2 of the NPDES eRule.
The 1,PA plans to propose changing the deadline for implementation of Phase 2 from December 21.
2020 to December 21, 2023 (see 40 CFR § 127.16 Table 1). The EPA believes this will provide enough
time fair the EPA and states to build most if not all the necessary electronic reporting tools and systems
lbr Phase 2 implementation.
The EPA also plans to propose a new electronic reporting waiver option for states that need even more
time to implement Phase 2 of the NPDES eRule. This waiver would give states the option to request
additional time from the EPA to implement electronic reporting for one or more specific Phase 2 general
permits or program reports. These state waivers would be sent to the EPA for review and approval. For
example. under this option a state could seek approval from the EPA to delay implementation of
electronic reporting for a NPDES general permit until some agreed upon time after December 21. 2023,
This waiver might be helpful if a state has a general permit that is a lower priority for electronic
Internet Address (URL) • http;/Iwww.epa.gov
Recycled(Recycteble 0 Printed wrth Vegetable Oil Based Inks on 100% Postconsu.mer, P-ocess Cnicrine Free Recycle; Paper

reporting (e.g., the general permit provides coverage for 10 or fewer NPDES-regulated entities).
Again, the EPA will continue to work collaboratively with ACWA and all state NPDES programs to
ensure implementation of the NPDES electronic reporting. I sent the same response to the other State
officials who contacted me. Please contact me or my staff, Mr. Randy Hill, Director of the Enforcement
Targeting and Data Division (hill.randN�,iu?epa.o_), if you have any questions about this letter or if you
have any implementation needs for NPDES electronic reporting.
Thank you very much for all your efforts to implement this important modernization effort for the
NPDES program. This switch from paper to electronic reporting is not possible without a strong
collaborative working relationship between our organizations.
Sincerely,
Susan Parker Bodine
cc: David Hindin
Director
U.S. EPA Office of Compliance
.John Dombrowski
Deputy Director
U.S. EPA Office of Compliance
Randolph L. Hill
Director
IJ.S. EPA Office of Compliance, Enforcement Targeting and Data Division
Andrew Sawyers
Director
U.S. EPA Office of Wastewater Management

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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
REASONABLE POTENTIAL ANALYSIS
Use "PASTE SPECIAL
Effluent
Hardness
Vsk*V then -COPY"
. Maximum date
points - 58
Date Data
BDL=112DL
Results
5/1812016
140
140
Std Dev.
10.8697
6/1512016
130
130
Mean
127.7143
7120/2016
120
120
C.V.
0.0851
8/17/2016
130
130
n
35
9/21/2016
110
110
10th Per value
110.00 mg/L
10/19/2016
130
130
Average Value
127.71 mg/L
11/16/2016
120
120
Max. Value
150.00 mg/L
12/21 /2016
130
130
1 /25/2017
110
110
2122/2017
130
130
3/29/2017
120
120
4/19/2017
130
130
5/10/2017
130
130
5/1712017
110
110
6/21 /2017
120
120
7/19/2017
120
120
8/23/2017
130
130
9/22/2017
130
130
11121/2017
130
130
12/20/2017
140
140
1 /24/2018
130
130
2/21/2018
140
140
3121/2018
110
110
4/18/2018
140
14U
5/23/2018
140
140
6/20/2018
140
140
7/25/2018
110
110
8/8/2018
120
120
8/22/2018
130
130
9/19/2018
130
130
10/17/2018
150
150
11120/2018
110
110
12/19/2018
130
130
1/10/2019
140
140
218/2019
140
140
H2
Use "PASTE SPECIA1
Upstream Hardness
then -COPY"
v'"°axxi
mum daft
Points = 58
Date
Data
BDL=1/2DL
Results
1
5/10/2016
79
79
Std Dev.
18.7104
2
6113/2016
77
77
Mean
70.7353
3
7/11/2016
56
56
C.V.
0.2645
4
8/15/2016
120
120
n
34
5
9/19/2016
90
90
10th Per value
51.50 mg/L
6
10/10/2016
58
58
Average Value
70.74 mg/L
7
11/21/2016
100
100
Max. Value
120.00 mg/L
8
12/21/2016
84
84
9
1/18/2017
83
83
10
2/1412017
82
82
11
3/16/2017
66
66
12
4/11/2017
77
77
13
5/17/2017
77
77
14
6/14/2017
29
29
15
7/18/2017
67
67
16
8/22/2017
60
60
17
9/11/2017
64
64
18
10/18/2017
99
99
19
11/15/2017
63
63
20
12112/2017
64
64
21
1/16/2018
76
76
22
2/14/2018
69
69
23
3/19/2018
38
E5
38
85
24
25
5/7/2018
84
84
26
6/18/2018
86
86
27
7/9/2018
50
50
28
816/2018
61
61
29
9/10/2018
34
34
30
10/1/2018
65
65
31
11/1912018
62
62
32
12113/2018
55
55
33
1/2/2019
66
66
34
214/2019
79
79
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
RPA Mallard Creek WRF, data
1 _ 8/13/2019

& Par02
Arsenic
Date
Data
BDL=1/2DL
1
4/12/2017
<
5
2.5
2 4/13/2017
<
5
2.5
3 4/19/2017
<
5
2.5
4 4/26/2017
<
5
2.5
5
5/3/2017
<
5
2.5
6
5/4/2017
<
5
2.5
7
5/10/2017
<
5
2.5
8
5/17/2017
<
5
2.5
9
5/24/2017
<
5
2.5
10
5/31/2017
<
5
2.5
11
6/7/2017
<
5
2.5
12
6/9/2017
<
5
2.5
13
6/14/2017
<
5
2.5
14
6/21/2017
<
5
2.5
15
6/28/2017
<
5
2.5
16
7/5/2017
<
5
2.5
17
7/8/2017
<
5
2.5
18
7/12/2017
<
5
2.5
19
7/19/2017
<
5
2.5
20
7/2612017
<
5
2.5
21
8/2/2017
<
5
2.5
22
8/6/2017
<
5
2.5
23
8/9/2017
<
5
2.5
24
8/16/2017
<
5
2.5
25
8/23/2017
<
5
2.5
26
8/30/2017
<
5
2.5
27
9/6/2017
<
5
2.5
28
9/11/2017
<
5
2.5
29
9/20/2017
<
5
2.5
30
9/27/2017
<
5
2.5
31
10/4/2017
<
5
2.5
32
10/10/2017
<
5
2.5
33
10/18/2017
<
5
2.5
34
10/25/2017
<
5
P.5
35
11/1/2017
<
5
2.5
36
11/8/2017
<
5
2.5
37
11/15/2017
<
5
2.5
38
11/21/2017
<
5
2.5
39
11/2912017
<
5
2.5
40
12/6/2017
<
5
2.5
41
12/7/2017
<
5
2.5
42
12/13/2017
<
5
2.5
43
12/20/2017
<
5
2.5
44
12/27/2017
<
5
2.5
45
1/6/2018
<
5
2.5
46
2/4/2018
<
5
2.5
47
3/5/2018
<
5
2.5
48
4/3/2018
<
5
2.5
49
5/9/2018
<
5
2.5
50
6/7/2018
<
5
2.5
51
7/13/2018
<
5
Y.5
52
8/8/2018
<
5
2.5
53
8/11/2018
<
5
2.5
54
9/9/2018
<
5
2.5
55
10/8/2018
<
5
2.5
56
11/6/2018
<
5
2.5
57
12/5/2018
<
5
2.5
58
1/10/2019
<
5
2.5
REASONABLE POTENTIAL ANALYSIS
U%9 "PASTE SP ECiAL
Val yi •- 1:m r 'i:.;"I
U-M.
, na<a
W.! , sn
Results
Std Dev.
Mean
2.5000
C.V.
0.0000
n
58
Mutt Factor = 1.00
Max. Value 2.5 ug/L
Max. Fred Cw 2.5 ug/L
RPA Mallard Creek WRF, data
2 8/13/2019

Date Data
1 8/5/2014 <
2 11/1112015 <
3 2/10/2016 <
4 5/10/2017 <
5 8/8/2018 <
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
REASONABLE POTENTIAL ANALYSIS
Beryllium
BDL=1/2DL
Results
5 2.5
Std Dev.
5 2.5
Mean
5 2.5
C.V. (defauR)
2 1
n
5 2.5
Mult Factor =
Max. Value
Max. Pred Cw
Use"PASTESPEUAL
vames" then "Corn"
. Maximum date
Poi ', M
2.2000
0.6000
5
2.32
2.50 ug/L
5.80 ug/L
Cadmium
Date
Data
BDL=1/2DL
Results
1
4/13/2017
<
1
0.5
Std Dev.
2
4119/2017
<
1
0.5
Mean
3
4/26/2017
<
1
0.5
C.V.
4
5/3/2017
<
1
0.5
n
5
5/4/2017
<
1
0.5
6
5/10/2017
<
1
0.5
MultFactor=
7
5/17/2017
<
1
0.5
Max. Value
8
5/24/2017
<
1
0.5
Max. Pred Cw
9
5/31/2017
<
1
0.5
10
6/7/2017
<
1
0.5
11
6/9/2017
<
1
0.5
12
6/14/2017
<
1
0.5
13
6/21/2017
<
1
0.5
14
6/28/2017
<
1
0.5
15
7/5/2017
<
1
0.5
16
7/812017
<
1
0.5
17
7/12/2017
<
1
0.5
18
7119/2017
<
1
0.5
19
7/26/2017
<
1
0.5
20
8/212017
<
1
0.5
21
816/2017
<
1
0.5
22
8/9/2017
<
1
0.5
23
8/16/2017
<
1
0.5
24
8/23/2017
<
1
0.5
25
8130/2017
<
1
0.5
26
9/6/2017
<
1
0.5
27
9/11/2017
<
1
0.5
28
9/20/2017
<
1
0.5
29
9/27/2017
<
1
0.5
30
10/4/2017
<
1
0.5
31
10/10/2017
<
1
0.5
32
10/18/2017
<
1
0.5
33
10/25/2017
<
1
0.5
34
11/1/2017
<
1
0.5
35
11/8/2017
<
1
0.5
36
11/15/2017
<
1
0.5
37
11 /21 /2017
<
1
0.5
38
11 /29/2017
<
1
0.5
39
1216/2017
<
1
0.5
40
12/7/2017
<
1
0.5
41
12/13/2017
<
1
0.5
42
12120/2017
<
1
0.5
43
12/27/2017
<
1
0.5
44
1/6/2018
<
1
0.5
45
214/2018
<
1
0.5
46
3/5/2018
<
1
0.5
47
4/3/2018
<
1
0.5
48
5/9/2018
<
1
0.5
49
6/7/2018
<
1
0.5
50
7/13/2018
<
1
0.5
51
8/8/2018
<
1
0.5
52
8/11/2018
<
1
0.5
53
9/9/2018
<
1
0.5
54
10/8/2018
<
1
0.5
55
11/6/2018
<
1
0.5
56
1215/2018
<
1 0.5
57
1110/2019
<
1 0.5
58
218/2019
<
1 0.5
Use"PASTE SPECIAL
VabjW then VW Y"
. Maximum data
points - 56
0.5000
0.0000
58
1.00
0.500 ug/L
0.500 ug/L
RPA Mallard Creek WRF, data
-3- 8/13/2019

Par07
REASONABLE POTENTIAL ANALYSIS
Total Phenolic Compounds
Date Data
1 8/5/2014
2 11/11/2015 <
3 2/10/2016 <
4 5/10/2017 <
5 8/8/2018 <
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
BDL=1/2DL
Results
39 39
Sid Dev.
5 2.5
Mean
50 25
C.V.(default)
50 25
n
50 25
Mult Factor =
Max. Value
Max. Fred Cw
LOU PA57C
SFMAL-Yal�s-
trwn'CCrPr-.
mftxj rm dada
po"s a 59
�3 1 i30
23.3000
0.6000
5
2.32
39.0 ug/L
90.5 ug/L
Parl0
Chromium, Total
Date
Data
BDL=1/2DL
Results
1
4/13/2017
<
5
2.5
Std Dev.
2
4/19/2017
<
5
2.5
Mean
3
4/26/2017
<
5
2.5
C.V.
4
5/3/2017
<
5
2.5
n
5
5/4/2017
<
5
2.5
6
5/10/2017
<
5
2.5
Mu@ Factor =
7
5/17/2017
<
5
2.5
Max. Value
8
5/24/2017
<
5
2.5
Max. Pred Cw
9
5/31/2017
<
5
2.5
10
6/7/2017
<
5
2.5
11
6/9/2017
<
5
2.5
12
6/14/2017
<
5
2.5
13
6/21/2017
<
5
2.5
14
6/28/2017
<
5
2.5
15
7/5/2017
<
5
2.5
16
7/8/2017
<
5
2.5
17
7/12/2017
<
5
2.5
18
7/19/2017
<
5
2.5
19
7/26/2017
<
5
2.5
20
8/2/2017
<
5
2.5
21
8/6/2017
<
5
2.5
22
8/9/2017
<
5
2.5
23
8/16/2017
<
5
2.5
24
8/23/2017
<
5
2.5
25
8/30/2017
<
5
2.5
26
9/6/2017
<
5
2.5
27
9111/2017
<
5
2.5
28
9/20/2017
<
5
2.5
29
9/27/2017
<
5
2.5
30
10/4/2017
<
5
2.5
31
10/10/2017
<
5
2.5
32
10/18/2017
<
5
2.5
33
10/25/2017
<
5
2.5
34
11/1/2017
<
5
2.5
35
11/8/2017
<
5
2.5
36
11/15/2017
<
5
2.5
37
11/21/2017
<
5
2.5
38
11/29/2017
<
5
2.5
39
12/6/2017
<
5
2.5
40
12/7/2017
<
5
2.5
41
12/13/2017
<
5
2.6
42
12/20/2017
<
5
2.5
43
12/27/2017
<
5
2.5
44
1/6/2018
<
5
2.5
45
2/4/2018
<
5
2.5
46
3/5/2018
<
5
2.5
47
4/3/2018
<
5
2.5
48
5/9/2018
<
5
2.5
49
617/2018
<
5
2.5
50
7/13/2018
<
5
2.5
51
8/8/2018
<
5
2.5
52
8/11/2018
<
5
2.5
53
9/9/2018
<
5
2.5
54
10/8/2018
<
5
2.5
55
11/6/2018
<
5
2.5
56
1215/2018
<
5
2.5
57
1/10/2019
<
5
2.5
58
2/8/2019
<
5
2.5
U" "PASTE SPECIAL
Vaiw 6" VMn'CO¢r
htmkvh mCaz
palm& - 56
2.5000 2
0.0000 3
58 4
5
1.00 6
2.5 Ng/L 7
2.5 Ng/L 8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
RPA Mallard Creek WRF, data
4 8/13/2019

REASONABLE POTENTIAL ANALYSIS
Copper
Date
Data BDL=1/2DL
Results
4/13/2017
2.3
2.3
Std Dev.
4/19/2017
2.2
2.2
Mean
4/26/2017
< 2
1
C.V.
5/312017
2.9
2.9
n
514/2017
2.8
2.8
5/1012017
3.8
3.8
Mult Factor =
5/17/2017
3.9
3.9
Max. Value
5124/2017
3.9
3.9
Max. Pred Cw
5/31/2017
3.6
3.6
6/712017
2.7
2.7
6/9/2017
3.1
3.1
6/14/2017
3.6
3.6
6/21/2017
3.9
3.9
6/28/2017
3.6
3.6
7/5/2017
3.3
3.3
7/8/2017
3.5
3.5
7112/2017
4
4
7/19/2017
3.4
3.4
7/26/2017
4.6
4.6
8/2/2017
4.2
4.2
816/2017
4.2
4.2
819/2017
4.2
4.2
8/1612017
4
4
8123/2017
4.6
4.6
8/30/2017
3.7
3.7
9/6/2017
3.1
3.1
9/11/2017
4.2
4.2
9/20/2017
4.4
4.4
9/27/2017
4.1
4.1
10/4/2017
4.3
4.3
10110/2017
3.7
3.7
10/18/2017
4
4
10/25/2017
3
3
1111/2017
2.6
2.6
1118/2017
8.8
8.8
11/15/2017
6.6
6.6
11/21/2017
4.7
4.7
11129/2017
3.5
3.5
12/6/2017
2.9
2.9
12/712017
2.9
2.9
12/13/2017
2.8
2.8
12/2012017
2.4
2.4
12/27/2017
2.3
2.3
1/612018
2.3
2.3
2/4/2018
2.3
2.3
3/5/2018
2.8
2.8
41312018
2.9
2.9
5/9/2018
2.9
2.9
617/2018
2.8
2.8
7/13/2018
5.4
5.4
8/8/2018
3.8
3.8
8/11/2018
4
4
9/912018
3.9
3.9
10/8/2018
3.9
3.9
11/612018
3.9
3.9
12/5/2018
2.7
2.7
1/10/2019
6.6
6.6
218/2019
< 2
1
Par12
um* "PASTE SPECIAL
vdluee" then "COPY"
ttnxin um data
polls - 58
1.2419
3.5948
0.3455
58
1.00
8.80 ug/L
8.80 ug/L
Date
Data
1
1/18/2017
<
10
2
216/2017
<
10
3
2/22/2017
<
10
4
3/7/2017
<
10
5
3/29/2017
<
10
6
4/512017
<
10
7
4/19/2017
<
10
8
5/4/2017
<
10
9
5/10/2017
<
10
10
5/1712017
<
10
11
6/9/2017
<
10
12
6/21/2017
<
10
13
7/7/2017
<
10
14
7/812017
<
10
15
7119/2017
<
10
16
8/6/2017
<
10
17
8/7/2017
<
10
18
8/2312017
<
10
19
9/11/2017
<
10
20
9/22/2017
<
10
21
10/10/2017
<
10
22
11/15/2017
<
10
23
11121 /2017
<
10
24
12/7/2017
<
10
25
1212012017
<
10
26
115/2018
<
10
27
1/6/2018
<
10
28
1/24/2018
<
10
29
2/412018
<
10
30
2/5/2018
<
10
31
2/21/2018
<
10
32
315/2018
<
10
33
3/21/2018
<
10
34
4/3/2018
<
10
35
4/18/2018
<
10
36
5/9/2018
<
10
37
5123/2018
<
10
38
6/7/2018
<
10
39
6/20/2018
<
10
40
7/1312018
<
10
41
7/2512018
<
10
42
8/8/2018
<
10
43
8/10/2018
<
10
44
8/11/2018
<
10
45
8/22/2018
<
10
46
9/9/2018
<
10
47
9/10/2018
<
10
48
9/1912018
<
10
49
10/812018
<
10
50
10/17/2018
<
10
51
11/6/2018
<
10
52
11/20/2018
<
10
53
1215/2018
<
10
54
12/19/2018
<
1
55
1/10/2019
<
1
56
1/2312019
<
1
57
218/2019
<
1
58
2/20/2019
<
1
-5-
Cyanide
BDL=1/2DL
0
0
0
0
0
Results
5
Std Dev.
5
Mean
5
C.V.
5
n
5
5
Mult Factor =
5
Max. Value
5
Max. Fred Cw
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
Um"PASTE SPECIAL
valuecown "COPY"
. Maxim -date
Pointe =ss 7
5.00
0.0000
58
1.00
5.0 ug/L
5.0 ug1L
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
RPA Mallard Creek WRF, data
8113/2019

Date
4/1312017 < 5
4/1912017 < 5
4/26/2017 < 5
5/312017 < 5
5/4/2017 < 5
5/10/2017 < 5
5/17/2017 < 5
5/24/2017 < 5
513112017 < 5
6/7/2017 < 5
6/9/2017 < 5
6/14/2017 < 5
6/21/2017 < 5
6/28/2017 < 5
7/5/2017 < 5
7/8/2017 < 5
7/12/2017 < 5
7/19/2017 < 5
7/26/2017 < 5
8/2/2017 < 5
8/6/2017 < 5
8/9/2017 < 5
8/16/2017 < 5
8/23/2017 < 5
8/3012017 < 5
9/6/2017 < 5
9/11/2017 < 5
9/20/2017 < 5
9/27/2017 < 5
10/412017 < 5
10/10/2017 < 5
10/18/2017 < 5
10/25/2017 < 5
11/1/2017 < 5
11/8/2017 < 5
11/15/2017 < 5
11/21/2017 < 5
1112912017 < 5
1216/2017 < 5
12/712017 < 5
12/13/2017 < 5
12/2012017 < 5
12/27/2017 < 5
1/6/2018 < 5
2/4/2018 < 5
3/5/2018 < 5
4/312018 < 5
5/9/2018 < 5
6/7/2018 < 5
7/13/2018 < 5
8/8/2018 < 5
8/11/2018 < 5
9/9/2018 < 5
10/8/2018 < 5
11/612018 < 5
12/5/2018 < 5
1/10/2019 < 5
2/8/2019 < 5
REASONABLE POTENTIAL ANALYSIS
Lead
BDL=1/2DL
Results
2.5
Std Dev.
2.5
Mean
2.5
C.V.
2.5
n
2.5
2.5
Mutt Factor=
2.5
Max. Value
2.5
Max. Fred Cw
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
use"PASTE SPECI^L Par18
V91006" then "COPY-
Maalm¢m data
Palms - ST
2.5000
0.0000
58
1.00
2.500 ug/
2.500 ug/
L
L
Date
Data
1
4/13/2017
<
5
2
4/19/2017
<
5
3
4/26/2017
<
5
4
5/3/2017
<
5
5
5/4/2017
<
5
6
5/10/2017
<
5
7
5/17/2017
<
5
8
5/24/2017
<
5
9
5/31/2017
<
5
10
6/7/2017
<
5
11
6/9/2017
<
5
12
6/14/2017
<
5
13
6/21/2017
<
5
14
6/28/2017
<
5
15
7/5/2017
<
16
7/8/2017
<
17
7/12/2017
<
18
7/19/2017
<
19
7/26/2017
<
20
8/2/2017
<
21
8/6/2017
<
22
8/9/2017
<
23
8/16/2017
<
5
24
8/23/2017
<
5
25
8/30/2017
<
5
26
9/612017
<
5
27
9/11/2017
<
5
28
9/20/2017
<
5
29
9/27/2017
<
5
30
10/4/2017
<
5
31
10/10/2017
5
32
10/18/2017
<
5
33
10/25/2017
<
5
34
11/1/2017
<
5
35
11/8/2017
<
5
36
11/15/2017
<
5
37
11/21/2017
<
5
38
11/29/2017
<
5
39
12/6/2017
<
5
40
12/7/2017
<
5
41
12113/2017
<
5
42
12/20/2017
<
5
43
12/27/2017
<
5
44
1/6/2018
<
5
45
2/4/2018
<
5
46
315/2018
<
5
47
4/3/2018
<
5
48
5/9/2018
<
5
49
6/7/2018
<
5
50
7/13/2018
<
5
51
8/8/2018
<
5
52
8/11/2018
<
5
53
9/9/2018
<
5
54
10/8/2018
<
5
55
11/6/2018
<
5
56
12/5/2018
<
5
57
1/10/2019
<
5
58
2/8/2019
<
5
Molybdenum
5
5
5
5
5
5
5
5
BDL=1/2DL
Results
2.5
Std Dev.
2.5
Mean
2.5
C.V.
2.5
n
2.5
2.5
Mutt Factor =
2.5
Max. Value
2.5
Max. Fred Cw
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.6
2.5
2.5
2.5
2.5
2.5
2.5
2.5
uq 'PASTE 5"CIAL'IPar7;
Values' than "C 6Pr"
WMAJMUM Cata
Pointe - U
0 3283
1
2.5431
2
0.1291
3
58
4
5
1.00
6
5.0 ug/L
7
5.0 ug/L
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
RPA Mallard Creek WRF, data
6 8/13/2019

7 & Par18
Date Data
4/13/2017 < 2
4/19/2017 2.6
4/26/2017 < 2
5/3/2017 2.4
5/4/2017 2.4
5/10/2017 < 2
5/17/2017 2.3
5/24/2017 2.3
513112017 < 2
6/7/2017 < 2
619/2017 < 2
6/14/2017 2.2
6/2112017 < 2
6/28/2017 2.1
715/2017 2.1
7/8/2017 < 2
7/12/2017 2.1
7/1912017 < 2
7/26/2017 2.5
8/2/2017 2.1
8/6/2017 2.1
8/9/2017 2.2
8/16/2017 2.2
8/23/2017 2.3
8/30/2017 < 2
9/612017 < 2
9111/2017 2.2
9/20/2017 2.4
9/27/2017 2.2
1014/2017 2.3
10/10/2017 2.1
10/18/2017 < 2
10/25/2017 2.3
11/1/2017 2.1
11/812017 < 2
11/15/2017 < 2
11/21/2017 < 2
11129/2017 < 2
12/612017 < 2
12/712017 < 2
12113/2017 < 2
12120/2017 < 2
12127/2017 < 2
116/2018 < 2
214/2018 < 2
3/5/2018 < 2
4/3/2018 < 2
5/9/2018 2.6
617/2018 2.5
7/13/2018 < 2
8/8/2018 < 2
8/11/2018 2.4
9/9/2018 3.1
10/8/2018 4.1
11/6/2018 2.1
12/5/2018 < 2
1110/2019 2.1
2/812019 2.5
REASONABLE POTENTIAL ANALYSIS
Nickel
BDL=112DL
Results
1
Std Dev.
2.6
Mean
1
C.V.
2.4
n
2.4
1
Mult Factor =
2.3
Max. Value
2.3
Max. Pred Cw
1
1
1
2.2
1
2.1
2.1
1
2.1
1
2.5
2.1
2.1
2.2
2.2
2.3
1
1
2.2
2.4
2.2
2.3
2.1
1
2.3
2.1
1
1
1
1
1
1
1
1
1
1
1
1
1
2.6
2.5
1
1
3.1
4.1
2.1
1
2.1
2.5
tJse"PASTE Par19
EPLCIALL
valuts" then
"COPY"
Maximum data
pants - Sa
1.6930
0.4390
57
1.00
4.1 Ng/L
4.1 pg/L
Date
Data
1
4/13/2017
<
5
2
4/19/2017
<
5
3
4/26/2017
<
5
4
5/3/2017
<
5
5
5/4/2017
<
5
6
5/1012017
<
5
7
5/17/2017
<
5
8
5/2412017
<
5
9
5/3112017
<
5
10
617/2017
<
5
11
619/2017
<
5
12
6/14/2017
<
5
13
6/21/2017
<
5
14
6/28/2017
<
5
15
7/5/2017
<
5
16
7/8/2017
<
5
17
7/12/2017
<
5
18
7/19/2017
<
5
19
7/26/2017
<
5
20
8/212017
<
5
21
8/612017
<
5
22
8/9/2017
<
5
23
8116/2017
<
5
24
8123/2017
<
5
25
8130/2017
<
5
26
9/6/2017
<
5
27
9/11/2017
<
5
28
9/20/2017
<
5
29
9/27/2017
<
5
30
10/4/2017
<
5
31
10/10/2017
<
5
32
10/18/2017
<
5
33
10/25/2017
<
5
34
11/112017
<
5
35
11/812017
<
5
36
11115/2017
<
5
37
11 /21/2017
<
5
38
11/2912017
<
5
39
12/6/2017
<
5
40
1217/2017
<
5
41
12/1312017
<
5
42
12/2012017
<
5
43
12/2712017
<
5
44
1/6/2018
<
5
45
2/4/2018
<
5
46
3/512018
<
5
47
4/312018
<
5
48
5/912018
<
5
49
6/712018
<
5
50
7/13/2018
<
5
51
8/8/2018
<
5
52
8111/2018
<
5
53
9/9/2018
<
5
54
10/8/2018
<
5
55
11/612018
<
5
56
12/5/2018
<
5
57
1/10/2019
<
5
58
2/8/2019
<
5
Selenium
BDL=1/2DL
Results
2.5
Std Dev.
2.5
Mean
2.5
C.V.
2.5
n
2.5
2.5
MultFactor=
2.5
Max. Value
2.5
Max. Fred Cw
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
We "PA8TE
PEC1AL-vakrm
there 'COPY' .
dmam data -Pa
= 5'a
2.5000
0.0000
58
1.00
2.5 ug/L
2.5 ug/L
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
RPA Mallard Creek WRF, data
-7- 8/13/2019

REASONABLE POTENTIAL ANALYSIS
0
Silver
u+a"PMTE SKCuu-
valulm " 1'mn "COS
Mwumu�s aau paErRa
= 58
Par21
Zinc
Date
Data
BDL=1/2DL
Results
Date
Data
BDL=1/2DL
Results
4/13/2017
<
5
2.5
Std Dev.
0.9017
1
4/13/2017
28
28
Std Dev.
4/19/2017
<
5
2.5
Mean
1.0517
2
4/19/2017
31
31
Mean
4/26/2017
<
5
2.5
C.V.
0.8574
3
4/26/2017
18
18
C.V.
5/3/2017
<
5
2.5
n
58
4
5/3/2017
32
32
n
5/4/2017
<
5
2.5
5
5/4/2017
33
33
5/10/2017
<
5
2.5
Mult Factor =
1.00
6
5/10/2017
40
40
Mult Factor =
5/17/2017
<
5
2.5
Max. Value
2.500 ug/L
7
5/17/2017
41
41
Max. Value
5/24/2017
<
5
2.5
Max. Pred Cw
2.500 ug/L
8
5/24/2017
35
35
Max. Pred Cw
5/31 /2017
<
5
2.5
9
5/31/2017
34
34
617/2017
<
5
2.5
10
6/7/2017
23
23
6/9/2017
<
5
2.5
11
6/9/2017
34
34
6/14/2017
<
5
2.5
12
6/14/2017
39
39
6/21/2017
<
5
2.5
13
6/2112017
36
36
6/28/2017
<
5
2.5
14
6/2812017
37
37
7/5/2017
<
5
2.5
15
715/2017
36
36
7/8/2017
<
1
0.5
16
7/8/2017
36
36
7/1212017
<
1
0.5
17
7/12/2017
38
38
7/1912017
<
1
0.5
18
7/19/2017
36
36
7/26/2017
<
1
0.5
19
7/26/2017
39
39
8/2/2017
<
1
0.5
20
8/2/2017
37
37
8/6/2017
<
1
0.5
21
8/6/2017
39
39
8/9/2017
<
1
0.5
22
8/9/2017
38
38
8/16/2017
<
1
0.5
23
8116/2017
34
34
8123/2017
<
1
0.5
24
8/23/2017
41
41
8130/2017
<
1
0.5
25
8/30/2017
43
43
9/6/2017
<
1
0.5
26
9/6/2017
39
39
9/11/2017
<
1
0.5
27
9/11/2017
48
48
9/20/2017
<
1
0.5
28
9120/2017
46
46
9/27/2017
<
1
0.5
29
9/27/2017
43
43
101412017
<
1
0.5
30
10/4/2017
46
46
1011012017
<
1
0.5
31
10/10/2017
49
49
10/18/2017
<
1
0.5
32
10/18/2017
40
40
10/25/2017
<
1
0.5
33
10/25/2017
45
45
111112017
<
1
0.5
34
11/1/2017
40
40
11/8/2017
<
1
0.5
35
11/8/2017
40
40
11/15/2017
<
1
0.5
36
11/15/2017
41
41
11/21/2017
<
1
0.5
37
11121/2017
45
45
11129/2017
<
1
0.5
38
11129/2017
44
44
12/612017
<
5
2.5
39
12/612017
41
41
12M2017
<
1
0.5
40
12/712017
40
40
12/13/2017
<
1
0.5
41
12113/2017
43
43
12/20/2017
<
1
0.5
42
12/20/2017
44
44
12/27/2017
<
1
0.5
43
12/27/2017
35
35
1/6/2018
<
1
0.5
44
1/6/2018
43
43
2/4/2018
<
1
0.5
45
2/4/2018
40
40
3/5/2018
<
1
0.5
46
3/5/2018
43
43
4/3/2018
<
1
0.5
47
4/3/2018
41
41
5/9/2018
<
1
0.5
48
5/9/2018
35
35
6/712018
<
1
0.5
49
6/7/2018
41
41
7/13/2018
<
1
0.5
50
7/13/2018
45
45
8/8/2018
<
1
0.5
51
8/8/2018
28
28
8111/2018
<
1
0.5
52
8/11/2018
33
33
9/9/2018
<
1
0.5
53
9/912018
49
49
10/8/2018
<
1
0.5
54
10/8/2018
47
47
11/6/2018
<
1
0.5
55
11/6/2018
44
44
12/5/2018
<
1
0.5
56
12/5/2018
33
33
1/10/2019
<
1
0.5
I
57
1/10/2019
36
36
2/8/2019
<
1
0.5
58
2/8/2019
31
31
usa "P+49'r@ sprCIAL
v,Mn 11" then'TaPr^
. Maximum da[a
pprnsf = SH
38.5517
0.1584
58
1.00
49.0 ug/L
49.0 ug/L
RPA Mallard Creek WRF, data
- 8 8/13/2019

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NH3/TRC WLA Calculations
Facility: Mallard Creek WRF
PermitNo. NCO030210
Prepared By: Nick Coco
Enter Design Flow (MGD): 12
Enter s7Q10 (cfs): 0.64
Enter w7Q10 i cfs): 2.1
Total Residual Chlorine (TRC)
Daily Maximum Limit (ug11)
Ammonia (Summer)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.64
s7Q10 (CFS)
0.64
DESIGN FLOW (MGD)
12
DESIGN FLOW (MGD)
12
DESIGN FLOW (CFS)
18.6
DESIGN FLOW (CFS)
18.6
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
96.67
IWC (%)
96.67
Allowable Conc. (ug/1)
18
Allowable Conc. (mg/1)
1.0
No Chlorine Used; N/A
Same as in current permit. Limit used
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/I)
Fecal Coliform
w7Q10 (CFS)
2.1
Monthly Average Limit:
2001100.mi DESIGN FLOW (MGD)
12
(If DF >331; Monitor)
DESIGN FLOW (CFS)
18.6
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
1.03 Upstream Bkgd (mg/1)
0.22
IWC (%)
89.86
Allowable Conc. (mg/l)
2.0
Same as in current permit. Limit used
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia (as NH3-N
1. If Allowable Conc > 35 mg/I, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

NH3/TRC WLA Calculations
Facility: Mallard Creek WRF
PermitNo. NC0030210
Prepared By: Nick Coco
Enter Design Flow (MGD): 13.1
Enter s7Q10 (cfs): 0.64
Enter w7Q10 cfs): 2.1
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.64
s7Q10 (CFS)
0.64
DESIGN FLOW (MGD)
13.1
DESIGN FLOW (MGD)
13.1
DESIGN FLOW (CFS)
20.305
DESIGN FLOW (CFS)
20.305
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/1)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
96.94
IWC (%)
96.94
Allowable Conc. (ug/l)
18
Allowable Conc. (mg/1)
1.0
No Chlorine Used; N/A
Some as in current permit. Limit used
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
2.1
Monthly Average Limit:
200/100-,
DESIGN FLOW (MGD)
13.1
(If DF >331; Monitor)
DESIGN FLOW (CFS)
20.305
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
1.03
Upstream Bkgd (mg/1)
0.22
IWC (%)
90.63
Allowable Conc. (mg/1)
2.0
Same as in current permit. Limit used
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia las NH3-N
1. If Allowable Conc > 35 mg/I, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

NH3/TRC WLA Calculations
Facility: Mallard Creek W RF
PermitNo. NC0030210
Prepared By: Nick Coco
Enter Design Flow (MGD): 14.9
Enter s7Q10 (cfs): 0.64
Enter w7Q10 (cfs): 2.1
Total Residual Chlorine (TRC)
Ammonia (Summer)
Daily Maximum Limit (ug/1)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.64
s7Q10 (CFS)
0.64
DESIGN FLOW (MGD)
14.9
DESIGN FLOW (MGD)
14.9
DESIGN FLOW (CFS)
23.095
DESIGN FLOW (CFS)
23.095
STREAM STD (UG/L)
17.0
STREAM STD (MG/L)
1.0
Upstream Bkgd (ug/l)
0
Upstream Bkgd (mg/1)
0.22
IWC (%)
97.30
IWC (%)
97.30
Allowable Conc. (ug/I)
17
Allowable Conc. (mg/1)
1.0
No Chlorine Used; N/A
Same as in current permit. limit used
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
2.1
Monthly Average Limit:
200/100m, DESIGN FLOW (MGD)
14.9
(If DF >331; Monitor)
DESIGN FLOW (CFS)
23.095
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
1.03 Upstream Bkgd (mg/1)
0.22
IWC (%)
91.67
Allowable Conc. (mg/1)
1.9
Some as in current permit. Limit used
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia as NH3-
1. If Allowable Conc > 35 mg/l, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

NH3/TRC WLA Calculations
Facility: Mallard Creek WRF
PermitNo. NC0030210
Prepared By: Nick Coco
Enter Design Flow (MGD): 16
Enter s7Q10 (cfs): 0.64
Enter w7Q10 cfs): 2.1
Total Residual Chlorine (TRC)
Daily Maximum Limit (ug/1)
s7Q10 (CFS)
0.64
DESIGN FLOW (MGD)
16
DESIGN FLOW (CFS)
24.8
STREAM STD (UG/L)
17.0
Upstream Bkgd (ug/1)
0
IWC (%)
97.48
Allowable Conc. (ug/1)
17
No Chlorine Used; N/A
Ammonia (Summer)
Monthly Average Limit (mg NH3-N/1)
s7Q10 (CFS)
0.64
DESIGN FLOW (MGD)
16
DESIGN FLOW (CFS)
24.8
STREAM STD (MG/L)
1.0
Upstream Bkgd (mg/1)
0.22
IWC (%)
97.48
Allowable Conc. (mg/1)
1.0
Some as in current permit. Limit used
Ammonia (Winter)
Monthly Average Limit (mg NH3-N/1)
Fecal Coliform
w7Q10 (CFS)
2.1
Monthly Average Limit:
2001100-1 DESIGN FLOW (MGD)
16
(If DF >331; Monitor)
DESIGN FLOW (CFS)
24.8
(If DF<331; Limit)
STREAM STD (MG/L)
1.8
Dilution Factor (DF)
1.03 Upstream Bkgd (mg/1)
0.22
IWC (%)
92.19
Allowable Conc. (mg/l)
1.9
Same as in current permit. Limit used
Total Residual Chlorine
1. Cap Daily Max limit at 28 ug/I to protect for acute toxicity
Ammonia t as NH3-N,
1. If Allowable Conc > 35 mg/l, Monitor Only
2. Monthly Avg limit x 3 = Weekly Avg limit (Municipals)
3. Monthly Avg limit x 5 = Daily Max limit (Non-Munis)
If the allowable ammonia concentration is > 35 mg/L, no limit shall be imposed
Fecal Coliform
1. Monthly Avg limit x 2 = 400/100 ml = Weekly Avg limit (Municipals) = Daily Max limit (Non -Muni)

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Permit: NC0030210
Instream Monitoring Summary
Date
Upstream
DO [mg/L]
Temp [degC]
5/5/2016
8.6
16.1
5/10/2016
8.3
19.4
5/16/2016
9
15.4
5/24/2016
9
16.4
5/31 /2016
8.2
21.1
6/l/2016
7.9
21.6
6/2/2016
8
21.7
6/3/2016
7.5
21.8
6/6/2016
7.5
22.8
6/7/2016
7.6
22.6
6/8/2016
7.9
20.2
6/13/2016
7.8
22.9
6/14/2016
7.9
22.1
6/15/2016
7
23.1
6/20/2016
7.9
20.3
6/21 /2016
8
21.7
6/22/2016
7.5
23.1
6/27/2016
7.3
22.6
6/28/2016
6.5
23.6
6/29/2016
7
22.3
7/5/2016
7.3
25.2
7/6/2016
7.1
24.8
7/7/2016
6.9
23.9
7/11 /2016
7
24.3
7/12/2016
7.4
24
7/13/2016
7
24.8
7/18/2016
7.4
24.3
7/19/2016
7.1
24.7
7/20/2016
7
24.3
7/25/2016
6.8
25.7
7/26/2016
6.5
25.7
7/27/2016
6.6
26
8/l/2016
6.6
25.2
8/2/2016
6.8
24.7
8/3/2016
6.8
24.4
8/9/2016
7.3
24.5
8/10/2016
7.4
24.6
8/11/2016
7.3
24.7
8/15/2016
7.2
25.4
8/17/2016
7.3
25.5
8/18/2016
7.1
24.8
8/22/2016
7.4
24.3
8/23/2016
7.4
22.4
8/24/2016
7.2
22.3
8/29/2016
7
23.4
8/30/2016
7.1
22.9
8/31 /2016
6.8
23.8
9/6/2016
7.6
21
9/7/2016
7.4
21.5
9/8/2016
7.2
21.7
9/12/2016
7
22.4
Downstream D1
DO [mg/L]
Temp [degC]
8
17.9
7.5
20.7
8
17.9
8.4
18.1
7.4
22.1
7.3
22.6
7.4
22.8
7.3
22.6
7.3
23.5
7.4
23.2
7.5
21.5
7.2
23.7
7.2
23.3
7.3
24.1
7.4
21.9
7.2
23
7
23.9
6.9
23.7
6.6
24.2
7
23.7
6.8
25.6
6.8
25.2
6.9
24.8
7
25.1
7.2
24.8
7
25.5
7
25.1
6.9
25.5
6.9
25.2
6.6
26.2
6.6
26.2
6.5
26.4
6.6
25.7
6.7
25.1
6.9
25.1
6.9
24.9
7
25.6
7.1
25.7
6.7
26.3
6.8
26.4
6.8
25.6
6.9
25.8
7.1
24.4
6.9
24.5
6.8
25.3
6.8
24.9
6.6
25.5
7.1
23.6
7
24
7
23.8
6.5
24.7
Downstream D2
DO [mg/L]
Temp [degC]
8.4
17.6
7.9
20.1
8.6
17
8.7
17.5
7.8
21.8
7.6
22.6
7.6
23
7.1
22.9
7.3
23.7
7.2
23.4
7.6
21.9
7.4
24.1
7.3
23.9
7.2
24.5
7.7
21.9
7.5
23.2
7.3
24.2
7.2
24.1
6.8
24.7
7.3
23.6
7.1
25.8
6.7
25.5
7
25.3
7.1
25.3
7.1
25
7.1
25.6
7.3
25
7
25.7
7
25.5
6.9
26.1
6.7
26.6
6.5
26.7
6.7
26.5
6.5
25.5
6.9
25.3
6.8
25.1
7
25.7
7
25.8
6.8
26.5
6.9
26.8
6.7
26
6.9
25.9
7.1
24.1
7.2
24.1
7
25
7
24.8
6.9
25.4
7.4
22.9
7.3
23.4
7.1
23.4
6.8
24.4

Date
9/13/2016
9/14/2016
9/19/2016
9/20/2016
9/21 /2016
9/28/2016
9/29/2016
9/30/2016
10/3/2016
10/10/2016
10/17/2016
10/26/2016
10/31 /2016
11 /7/2016
11 /14/2016
11/21/2016
11 /28/2016
12/5/2016
12/15/2016
12121 /2016
12/28/2016
1 /5/2017
1/12/2017
1 /18/2017
1 /25/2017
2/l /2017
2/6/2017
2/14/2017
2/21 /2017
2/28/2017
3/6/2017
3/16/2017
3/21 /2017
3/29/2017
4/3/2017
4/11 /2017
4/17/2017
4/26/2017
5/l /2017
5/8/2017
5/17/2017
5/24/2017
5/31 /2017
6/5/2017
6/6/2017
6/7/2017
6/12/2017
6/ 13/2017
6/14/2017
6/19/2017
6/20/2017
6/21 /2017
6/26/2017
Upstream
DO [mg/L] Temp [degC]
6.7
22.4
7
22.2
6.4
23.3
6.6
22.3
6.5
21.8
7.7
21.8
7.5
21.7
7.6
21.5
8
19.2
9
16.3
8.4
18
9.1
12.2
7.9
16.3
9
11.9
10.2
9.6
10.4
7.2
10.3
8.2
10.4
10.1
11.6
5.7
12.1
5
10.2
10.9
11
7.6
11.5
7.6
9.8
13.8
10.7
9.4
11.2
8.1
11.8
6.5
11
8.6
10.6
11.7
10.1
10.7
11.1
9.8
12.4
4.5
10.6
13.3
8.9
16.2
9.1
15.9
9.4
16
8.6
18.5
9.2
15.8
7.8
21
9.4
14.6
8
20.3
8.2
20.2
8
21.1
7.7
21.9
8
21.2
8.1
20.1
8.1
21.1
8.2
22
7.5
22
7.4
23.7
7.4
23.7
7.8
22.3
7.5
21.1
Downstream D1
DO [mg/L]
Temp [degC]
6.5
24.5
6.6
24.4
6.3
25.6
6.4
24.4
6.4
24.1
7.3
23.1
7.2
22.5
7.4
22
7.4
21.8
8.3
18.1
7
21.2
7.4
17.4
6.7
19.9
7.2
17.4
7.5
16.8
7.8
14.9
7.7
14.6
10
10.8
9.2
12
9.8
10.7
8.9
15.2
10
10.4
10.4
10.6
8.5
16.9
9.8
12
9.6
12.6
9.8
12.5
9.6
13.3
9.4
15.4
8.9
14.6
9.5
14
10.4
10.3
9.1
17.2
8.2
18.2
7.8
18.2
8.4
18.4
7.7
20.5
8.8
17
7.3
21.6
8.3
17.7
7.3
22.2
7.8
20.8
7.7
21.9
7.5
22
7.6
21.7
7.8
21.2
7.6
22.8
7.4
23.5
7.3
22.8
7.1
24.4
7.1
24.1
7.5
22.9
7.5
22.6
Downstream D2
DO [mg/L]
Temp [degC]
6.8
24
7
24
6.9
25
6.7
24.1
6.9
23.5
7.4
22.9
7.2
22.5
7
22.2
7.9
20.9
8.4
17.8
8
19.5
8.5
15.1
7.7
18.2
8.6
14.7
9.2
13.3
9.4
11.2
9.5
10.7
10.2
10
10.5
8.9
11.1
7.4
9.3
13.6
10.4
9.4
11.4
8
9.3
14.9
9.9
11.1
10.8
9.4
10.9
9.2
10.2
11.9
10
13.6
9.7
13
10.6
11.2
11.9
7.3
10.2
14.6
8.3
18.4
8.6
17.2
8.9
17.4
7.9
20.4
8.4
16.8
7.6
21.9
9
16.3
7.8
22.1
7.7
20.4
7.7
22
7.4
21.8
6.7
22
7.5
21.8
7.8
22.6
7.7
23.3
7.1
22.9
7.2
24.6
7
24.5
7.6
23
7.8
22.4

Date
6/27/2017
6/28/2017
7/3/2017
7/5/2017
7/6/2017
7/10/2017
7/11 /2017
7/12/2017
7/17/2017
7/18/2017
7/19/2017
7/25/2017
7/26/2017
7/27/2017
8/l/2017
8/2/2017
8/3/2017
8/7/2017
8/8/2017
8/9/2017
8/14/2017
8/15/2017
8/16/2017
8/21/2017
8/22/2017
8/23/2017
8/28/2017
8/29/2017
8/30/2017
9/5/2017
9/6/2017
9/7/2017
9/11/2017
9/12/2017
9/13/2017
9/18/2017
9/19/2017
9/21 /2017
9/25/2017
9/2612017
9/27/2017
10/2/2017
10/9/2017
10/18/2017
10/23/2017
10/30/2017
11 /6/2017
11/15/2017
11 /20/2017
11 /27/2017
12/4/2017
12/12/2017
12/18/2017
Upstream
DO [mg/L] Temp [degC]
7.6
20.9
8.1
19.6
7.7
23.5
7.5
23.4
7.4
23.4
7.6
23.3
7.5
23.6
7.5
24.7
7.6
23.2
7.4
23.5
7.4
23.4
6.8
24.8
6.8
24.4
7.1
24.4
7.7
20.9
7.3
21.8
7.3
22.2
7.2
23.8
7.4
23.6
7.6
22.1
7.5
23.7
7.3
24.2
7.5
24
6.1
25
6.8
24.6
6.8
24.9
7.6
20.8
7.4
20.6
7.7
19.8
7.8
20.6
7.5
21.1
8.5
18.4
8.5
16.9
8.9
18.3
8.6
18.4
7.7
20.9
7.5
20.9
7.6
21.6
7.6
21
7.3
21.1
6.8
21.9
7.8
15.8
6
22.3
8.9
14.3
7.6
18.2
9.3
10.3
7.9
16.7
10.4
8.5
10.5
7.6
11.3
6.4
10.8
8.9
12
6.4
11.5
7.5
Downstream D1
DO [mg/L]
Temp [degC]
7.4
22.7
7.6
21.7
7.2
25
7.3
24.7
7.3
24.5
7.2
24.9
7.2
25
7.1
26.1
7.3
24.8
7.1
25.4
7.3
25.3
7
25.9
7
25.4
7
26
7.1
23.7
7.1
24.2
7
24.4
6.9
23.9
7.2
24.2
7.3
23.6
7.1
25
6.3
24.4
7.1
25
6.6
25.7
6.7
26.1
6.6
26.3
6.8
23.6
6.8
23.3
6.9
22.9
7.1
23.7
6.8
23.7
8.1
20.1
7.4
20.8
8.6
18.6
8.2
20.1
7.2
23.5
7.2
23.3
7
23.6
6.9
23.6
6.8
23.7
6.7
24
7.2
20.6
6.4
24.5
8
18.1
7
22
7.9
15.7
7.4
20.8
8.6
14.4
8.4
14.6
8.7
13.9
8.7
15.1
9.7
12.7
9.2
13.8
Downstream D2
DO [mg/L]
Temp [degC]
7.7
22.5
7.9
21.5
7.4
24.8
7.3
24.8
7.4
24.6
7.4
24.6
7.3
25
7.3
26.1
7.4
25.3
7.1
25.1
7.4
25
7
26.2
7
26
7.2
26
7.6
23.3
7.4
23.8
7.4
23.9
7.2
24.6
7.1
24.2
7.5
23.3
7.2
24.9
6.3
24.6
7
25.1
7.1
26.1
7
26.2
7
26.4
7.5
22.9
7.3
22.6
7.5
21.8
7.9
22.1
7.6
22.7
8
19.5
8.4
18.7
8.4
18.2
8.2
19.4
7.8
22.4
7.7
22.6
7.5
23
7.6
22.6
7.4
22.9
7.2
23.2
8.3
18.4
7.3
23
8.8
15.9
7.9
19.3
9.2
13.4
8.3
18.1
10.2
10.8
10
11.2
10.7
9.8
10.2
12
11.9
7.9
11.2
9.4

Date
12/27/2017
1 /2/2018
1 /1012018
1 /16/2018
1 /22/2018
1/31/2018
2/7/2018
2/14/2018
2/21 /2018
2/27/2018
3/6/2018
3/14/2018
3/19/2018
3/26/2018
4/4/2018
4/9/2018
4/17/2018
4/23/2018
5/2/2018
5/7/2018
5/14/2018
5/21 /2018
5/29/2018
6/4/2018
6/5/2018
6/6/2018
6/11 /2018
6/12/2018
6/13/2018
6/18/2018
6/19/2018
6/20/2018
6/25/2018
6/26/2018
6/27/2018
7/2/2018
7/3/2018
7/5/2018
7/9/2018
7/10/2018
7/11 /2018
7/16/2018
7/17/2018
7/19/2018
7/23/2018
7/24/2018
7/25/2018
7/30/2018
7/31 /2018
8/l /2018
8/6/2018
8/7/2018
8/8/2018
Upstream
DO [mg/L]
Temp [degC]
12.1
5.3
13.4
0.9
13.4
2.4
13.7
0.8
12.3
5.3
12.5
4
11.3
8.5
10.8
9.4
9.4
16
10.6
11.4
10.5
10.8
11.5
7.3
10
12.7
11.2
8.4
8.9
17.5
10.2
10.6
10.1
10.5
9.2
14.2
9.2
15.6
8.9
17.8
7.6
21.3
7.7
21.4
7.8
21.8
7.7
21.7
8
20.3
8
20.1
7.5
23.8
7.1
21.5
7.9
21.3
7.6
24.5
7.3
24.6
7.2
25.3
6.7
24.3
7.1
23.3
6.9
23.2
6.6
25.2
6.5
24.7
6.1
24.6
7.7
20.6
7.5
21.3
7.3
22.7
6.8
24.1
6.9
24.2
6.8
23.3
7.2
22.3
8
22.9
7.4
22.9
7.1
23.6
7.2
23.9
7.5
23.6
7.5
24.1
7.5
23.2
7.4
23.7
Downstream D1
DO [mg/L]
Temp [degC]
9.8
11.5
10.5
7.7
10.7
10.6
10.7
8.7
10
11.2
11
8.2
10.2
11.5
9.7
12.4
8.6
18.3
9.5
14.4
9.8
12.6
10.5
10.3
9
15.3
10.3
10.9
8.7
19
9.2
13.9
9.2
13.7
8.1
16.8
8.4
18
7.9
20.1
7.2
22.6
7.4
21.9
7.6
22
7.4
22.8
7.6
22.3
7.6
22.2
7.2
24.5
7.4
22.4
7.6
22.9
7.2
25.2
7.2
25.4
7.2
25.7
7.3
25.2
7.4
24.4
7.5
24.3
7.2
26.1
7
25.6
6.9
25.8
7.4
22.6
7.3
23.5
7.1
24.3
6.6
25.1
6.9
25.3
7
24.5
7.2
24.1
7
23.2
7.2
23.6
7.1
25.2
7.2
24.8
7.2
24.1
7.2
25.4
6.9
23.5
7.1
24.1
Downstream D2
DO [mg/L]
Temp [degC]
11.4
7.5
13
2.6
12.6
5
12.8
4.1
11.8
7.4
11.5
6.9
11.3
8.8
10.5
10.9
9.2
16.2
9.8
13.7
10.3
11.4
10.8
9.2
9.5
14.4
10.4
10.6
9
18.2
10.2
12.2
9.4
13.4
8.7
15.6
9
16.7
8.3
19.7
7.6
22.7
6.8
21.6
7.5
22.3
7.6
23.2
7.8
22.2
7.9
21.9
7.3
25
7.3
23.2
7.7
22.5
6.9
25.7
7.1
26.2
7
26.8
7
26.2
7.2
25
7.6
24.3
7
26.7
6.8
26.6
6.9
26.4
7.5
22.6
7.4
23.4
7.2
24.6
7.1
25.4
7
25.6
7.1
25.3
7.3
24
7
23.3
7.1
23.5
7.3
25.3
7
24.9
7.1
24.2
7.4
25.4
6.1
23.8
7
24.5

Date
Upstream
Downstream D1
Downstream D2
DO [mg/L]
Temp [degC]
DO [mg/L]
Temp [degC]
DO [mg/L]
Temp [degC]
8/13/2018
7.5.
22.9
7.5
23.6
7.5
24
8/14/2018
7.6
22.8
7.4
24.2
7.6
24.1
8/15/2018
7.5
22.5
7.4
24.1
7.6
24.1
8/20/2018
7.1
23.8
7.1
25
7.2
24.9
8/21 /2018
7.1
23.9
6.9
25
6.9
24.5
8/22/2018
7
23.4
6.9
25
7.4
24.4
8/27/2018
7.1
22.5
6.8
24.7
7.6
23.5
8/28/2018
6.6
22.8
7
24.6
7.5
23.9
8/29/2018
6.6
23.4
7
24.8
7.4
24.4
9/4/2018
6.3
23.6
6.7
25.2
7.3
24.7
9/5/2018
6.2
23.7
6.7
25.3
7.2
24.8
9/6/2018
6.4
23.6
6.9
25
7.2
24.8
9/10/2018
7.1
22.7
6.9
23.3
6.8
23.5
9/11/2018
7.1
23.3
6.9
24.3
7.3
23.5
9/12/2018
6.5
23.3
6.7
24.8
7.2
24
9/19/2018
7.8
21.9
7.2
23.4
7.2
23.3
9/20/2018
7.8
22
7.3
23.6
7.4
23.2
9/21/2018
7.4
22.4
7.2
23.9
7.4
23.4
9/24/2018
7.2
21.3
6.9
23.3
7.4
22.6
9/25/2018
7.4
21.3
7
23.3
7.6
22.3
9/26/2018
7.4
20.9
7.1
23.1
7.6
22.2
10/l/2018
7.6
20.3
7.3
22.3
7.8
21.7
10/8/2018
7.1
22.1
7
23.6
7.5
23.2
10/15/2018
8.8
16.9
8
19.8
8.6
18.2
10/22/2018
9.5
12.1
8.2
16.7
9.2
14.6
10/29/2018
9.7
12.9
8.9
15.6
9.4
14.1
11 /5/2018
9.5
13.9
9
15.1
9
14.8
11 /16/2018
10.7
9.4
10
10
10.3
8.8
11 /19/2018
10.5
10.2
9.6
13.2
10.2
11.2
11 /26/2018
10.4
10.7
9.4
13.9
10.1
11.9
12/3/2018
9.9
12.3
9.2
14.2
9.6
13.1
12/13/2018
11.7
6.6
11.1
8.1
11.5
6.6
12/17/2018
11.2
8.6
10.4
10.2
10.4
9.7
12/26/2018
11.8
5.8
10.8
8.6
11.2
7.3
1 /2/2019
10
12.6
9.4
14.3
9.6
13.8
1 /7/2019
10.8
9.9
10.1
12.1
10.3
11.1
1/14/2019
11.7
6.6
10.8
8.8
11.3
7
1/22/2019
12.5
3.5
11.2
7.2
11.7
5.7
1/28/2019
11.4
7.1
10.4
9.9
11.2
8.1
2/4/2019
11.5
7.5
10
11.4
10.9
9.8
2/11/2019
11.4
8.1
10.5
11.8
11.2
9.6
2/18/2019
11.2
8.7
10.9
9.4
10.8
8.9
2/25/2019
10.9
8.8
10.3
10.5
10.2
10
Average
18.664567
8.361264822
20.789764
7.775494071
20.092913
8.158893281
Max
26
13.7
26.4
11.2
26.8
13
Min
0.8
6
7.2
6.3
2.6
6.1

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d

NPDES/Aquifer Protection Perm
PERMIT WRITER COMPLETES THIS PART:
Date of Request 8/13/2019
Re uestor Nicholas Cocc
Facility Name Mallard Creek
Permit Number NC0030210
Region Mooresville
Basin Yadkin Pee Df
Unit Pretreatment
Information Request Form
PERMIT WRITERS - AFTER you net this form back
Check all that apply
from PERCS:
- Notify PERCS if LTMP/STMP data we said should
be on DMRs is not really there, so we can get it for
you (or NOV POT".
- Notify PERCS if you want us to keep a specific POC
in LTMP/STMP so you will have data for next permit
renewal.
-Email PERCS draft permit, fact sheet, RPA.
- Send PERCS paper copy of permit (w/o NPDES
boilerplate), cover letter, final fact sheet. Email RPA if
changes.
municipal renewall
X
new industries
WWTP expansion
X
Speculative limits
stream reclass.
outfall relocation
7Q10 change
nfh.ri
k applicable PERCS staff: Oth2r Comments to PERCS:
BRD, CPF, CTB, FRB, TAR - Vivian Zhong (807-6310)
Facility is rated 12.0 MGD wtih 3 CIUs listed in its application. The facility
-HO, HIW, LTN, LUM, NES, NEW, ROA, YAD has applied for a multi -tiered expansion with tiers of 13.1 MGD, 14.9 MGD
Monti Hassan (607 6314} and 16.0 MGD. Water quality modeling has been submitted and reviewed
and speculative limits have been provided.
i
PERCS PRETREATMENT STAFF COMPLETES THIS PART:
Status of Pretreatment Program (check all that apply)
1) facility has no SIU's, does have Division approved Pretreatment Program that is INACTIVE
2) facility has no SIU's, does not have Division approved Pretreatment Program
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
Flow, MGD
Permitted
Actual
Timeperiod for Actual
Industrial
0.1998
0.085
2016-2017
Most recent:
Uncontrollable
n/a
9.145
2016-2017
Next Cycle:
4
a
a
Parameter of
Concern (POC)
POC due to
NPDESI Non-
Required by
Required
POC due
POTW POC
STMP
LTMP
V
°a
Check List
Disch Permit
Limit
EPA*
b 503
Y
Sludge*"
to SIU"*`
(Explain
below)'*"
Effluent
Freq
Effluent
Freq
BOD
M
TSS
M
NH3
M
Arsenic
M
Cadmium
M
Chromium
M
Copper
M
Cyanide
M
Lead
M
Mercury
M
Molybdenum
M
Nickel
M
Silver
M
Selenium
M
Zinc
M
Total Nitrogen I
M
Phosphorus
M
COD
M
O&G
M
M
M
STMP time frame:
= Quarterly
0 = Monthly
Is all data on DMRs?
YES
NO (attach data)
Is data in spreadsheet
YES email to writer)
NO
nmaya ni uie L I rvtrra t tvtr " 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
ments to Permit Writer (ex., explanation of any Pi
only sample at influent and primary clarifier effluent.
Copy of PERCS_NPDES_Pretreatment.request.form.Apri@019
Revised: July 24, 2007

United States Environmental Protection Agency Form Approved.
EPA
Ar/`1 Washington, D.C. 20460 OMB No. 2040-0057
Water Compliance Inspection Report Approval expires8-31-98
Section A: National Data System Coding (i.e., PCS)
Transaction Code NPDES yr/mo/day Inspection Type Inspector Fac Type
1 2 15 I 3 NC0030210 .11 12 19/02/11 117 18 I S I 19 I s i 201
211II1II IIIIIII1IIIIIIIIIIIIIIIII IIIIIIIIIII r6
Inspection Work Days Facility Self -Monitoring Evaluation Rating B1 QA Reserved------
67 2.0
70 Ia I 71 i„ I 72 i ti j
Section B: Facility Data
73 I I 174
711 I I I I I U80
Name and Location of Facility Inspected (For Industrial Users discharging to POTW, also include
Entry Time/Date
Permit Effective Date
POTW name and NPDES permit Number)
09:25AM 19/02/11
14/01/01
Mallard Creek WWTP
Exit Time/Date
Permit Expiration Date
12400 US Hwy 29 N
01:O5PM 19/02111
18/11l30
Charlotte NC 28262
Name(s) of Onsite Representative(s)/Titles(s)/Phone and Fax Number(s)
Other Facility Data
Henry Harrison Eudy/ORC/980-214-59771
Name, Address of Responsible Official/Title/Phone and Fax Number
Contacted
Jacqueline A Jarrell,5100 Brookshire Blvd Charlotte NC 282163371/Operations
No
Chief/704-336-5433/
Section C: Areas Evaluated During Inspection (Check only those areas evaluated)
Permit E Flow Measurement operations & Maintenance Records/Reports
Self -Monitoring Program E 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
Wes Bell MRO W0004-663-1699 Ext.2192/
Signature of Management Q A Reviewer Agency/Office/Phone and Fax Numbers Date
W. Corey Basinger Division of Water Quality/R04-2;
EPA Form 3560-3 (Rev 9-94) Previous editions are obsolete.
Page#

NPDES yr/mo/day Inspection Type
31 NCO030210 J11 12 19/02/11 17 18 I' I
(Cont.)
Section D: Summary of Finding/Comments (Attach additional sheets of narrative and checklists as necessary)
On -site Representatives:
The following Charlotte Water personnel were in attendance during the inspection: Joseph
Lockler/Operations Manager; Henry Eudy/ORC; Tara Romine/Backup ORC; and Doug Wise/Water
Quality Program Specialist.
WWTP PCB Decontamination Progress:
PCB decontamination activities were completed in the Fall of 2017. The WWTP consistently achieved
compliance with effluent permit limits and maintained non -detectable PCB effluent levels during the
decontamination activities and following months until the end of September 2018 (sampling was
stopped).
Page#

Permit: NCO030210
Inspection Date: 02/11/2019
Owner - Facility: Mallard Creek VWVrP
Inspection Type: 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? 0 ❑ ❑ ❑
# Are there any special conditions for the permit? M ❑ ❑ ❑
Is access to the plant site restricted to the general public? ■ ❑ ❑ ❑
Is the inspector granted access to all areas for inspection? M ❑ ❑ ❑
Comment: The Division received the permit renewal acka a on 6/7/18
Overall, the facility is adequately described however. the facility has an additional
equalization basin (5 MG). four final clarifiers four traveling bridge tertiary filters. two
thickening centrifuges and two dewatering centrifuges.
Charlotte Water implements an approved Industrial Pretreatment Program.
The last compliance evaluation inspection performed by DWR staff was on 2/24/17.
Record Keeping
Yes No NA NE
Are records kept and maintained as required by the permit?
M
❑
❑
❑
Is all required information readily available, complete and current?
0
❑
❑
❑
Are all records maintained for 3 years (lab. reg. required 5 years)?
M
❑
❑
❑
Are analytical results consistent with data reported on DMRs?
M
❑
❑
❑
Is the chain -of -custody complete?
M
❑
❑
❑
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?
0
❑
❑
❑
(If the facility is = or > 5 MGD permitted flow) Do they operate 24/7 with a certified operator
0
❑
❑
❑
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?
M
❑
❑
❑
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?
0
❑
❑
❑
Page# 3

Permit: NCO030210 Owner - Facility: Mallard Creek WWTP
Inspection Date: 02/11/2019 Inspection Type: Compliance Evaluation
Record Keeping
Yes No NA NE
Comment: The records reviewed durinn the inspection were or anized and well maintained.
Discha
e
Monitoring Re orts eDMRs were reviewed for the Period Janua 2018 throw h December
2018. No effluent limit violations were reported and all monitorin frequencies were correct.
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?
❑ ❑
❑
# 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?
❑ ❑
❑
Comment: Influent and effluent analyses are verformed bv Charlotte Water's Environmental Services
Laboratory Certification #192 . ETT Environmental Inc. toxici and R&A Labs
toxicity)
have also been contracted to rovide anal tical su ort.
Influent Sam lin
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?
■
❑
❑
❑
Comment: The subject Permit re uires influent BOD and TSS Composite sam les. The com osite
sampler was collecting 175 ml. aliquots and the internal sampler temperature was two
degrees Celsius at the time of the ins ection. The facili staff perform monthly
aliquot
calibrations at a minimum on the sampler.
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
El
❑
ElCelsius)?
Is the facility sampling performed as required by the permit (frequency, sampling type
Ilk
❑
❑
❑
representative)?
Page# 4

Permit: NCO030210
Inspection Date: 02/11/2019
Effluent Sam Ip inq
Owner - Facility: Mallard Creek WWTP
Inspection Type: Compliance Evaluation
Yes No NA NE
Comment: The subject permit requires composite and grab effluent samples. The composite sampler
was collectin 150 mi. aliquots and the internal sampler temperature was one degree
Celsius at the time of the inspection The facility staff perform monthly aliquot calibrations_
at a minimum on the sampler.
Upstream I Downstream Sampling, Yes No NA NE
Is the facility sampling performed as required by the permit (frequency, sampling type, and 0 ❑ ❑ ❑
sampling location)?
Comment:
Operations & Maintenance Yes No NA NE
Is the plant generally clean with acceptable housekeeping? 0 ❑ ❑ ❑
Does the facility analyze process control parameters, for ex: MLSS, MCRT, Settleable E ❑ ❑ ❑
Solids, pH, DO, Sludge Judge, and other that are applicable?
Comment: The wastewater treatment facility appeared to be Droperly operated and well maintained.
The ORC and staff implement a comprehensive orocess control program with all
measurements being ro erl documented and maintained on -site.
The facility is equipped with a SCADA system to assist the wastewater staff with the
facility's operations. There are approximately seven SCADA stations located throughout the
WWTP site.
Flow Measurement - Influent Yes No NA NE
# Is flow meter used for reporting? ❑ E ❑ ❑
Is flow meter calibrated annually? N ❑ ❑ ❑
Is the flow meter operational? M ❑ ❑ ❑
(If units are separated) Does the chart recorder match the flow meter? ❑ ❑ ® ❑
Comment: The flow meter is calibrated annually and was last calibrated on 7/16/18 by Expert Services
International LLC.
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?
0
❑
❑
❑
Is disposal of screening in compliance?
N
❑
❑
❑
Is the unit in good condition?
N
❑
❑
❑
Page# 5

Permit: NC0030210 Owner - Facility: Mallard Creek WWTP
Inspection Date: 02/11/2019
Inspection Type: Compliance Evaluation
Bar Screens Yes No NA NE
Comment: Both mechanical bar screens were or ,erational and in service.
Pump Station - Influent
Yes No NA NE
Is the pump wet well free of bypass lines or structures?
❑
❑
❑
Is the wet well free of excessive grease?
❑
❑
❑
■
Are all pumps present?
■
❑
❑
❑
Are all pumps operable?
■
❑
❑
❑
Are float controls operable?
■
❑
❑
❑
Is SCADA telemetry available and operational?
.
❑
❑
❑
Is audible and visual alarm available and operational?
❑
❑
N
❑
Comment: The facility is p_quipped with an influent puMp
station and intermediate Pump station
e ualization day tanks .
Grit Removal
Type of grit removal
Yes No NA NE
a.Manual El
b.Mechanical .
Is the grit free of excessive organic matter? . ❑ El ❑
Is the grit free of excessive odor? ❑ ❑ ❑
# Is disposal of grit in compliance? . ❑ 11
❑
Comment: Both grit removals stems were operational and in service. Screenin sand ❑rit are
disposed at the Republic Services Landfill former BFI Landfill)_
Equalization Basins
Yes
No NA NE
Is the basin aerated?
❑
❑
.
❑
Is the basin free of bypass lines or structures to the natural environment?
0❑
El
❑
Is the basin free of excessive grease?
■
❑
❑
❑
Are all pumps present?
■
❑
❑
❑
Are all pumps operable?
❑
❑
❑
Are float controls operable?
.
❑
❑
❑
Are audible and visual alarms operable?
❑
❑
■
❑
# Is basin size/volume adequate?
■
❑
❑
❑
Comment: Both day tanks and 5 MG equalization basin were o erational.
The 5 MG -equalization
basin
is primarily used during high flow/storm events. All three equalization basins are connected
to the SCADA system.
Page# 6

Permit: NCO030210
Inspection Date: 02111/2019
Equalization Basins
Primary Clarifier
Is the clarifier free of black and odorous wastewater?
Owner - Facility: Mallard Creek WWTP
Inspection Type: Compliance Evaluation
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'/4 of the sidewall depth)
Comment: All five primaries were ooprational;..however_ only three were in service.
Yes No NA NE
Yes No NA NE
® ❑ ❑ ❑
• ❑ ❑ ❑
❑ ❑ ❑
■ ❑ ❑ ❑
❑ ❑ ❑
❑ ❑ ❑
• ❑ ❑ ❑
• ❑ ❑ ❑
• ❑ ❑ ❑
• ❑ ❑ ❑
Aeration Basins
Yes No NA NE
Mode of operation
Ext. Air
Type of aeration system
Diffused
Is the basin free of dead spots?
N
❑
❑
❑
Are surface aerators and mixers operational?
0
❑
❑
El
Are the diffusers operational?
N
❑
❑
❑
Is the foam the proper color for the treatment process?
❑
❑
❑
Does the foam cover less than 25% of the basin's surface?
❑
❑
❑
Is the DO level acceptable?
❑
❑
❑
Is the DO level acceptable?(1.0 to 3.0 mg/1)
❑
❑
®
❑
Comment: The facility is eauipped with three anoxic/aeration basin trains all o erationah. All of
aeration train #3 and half of aeration trains #1 and #2 one of two rectangular aeration basins
per train were currently.in service.
Magnesium hydroxide is added to maintain appropriate alkalinity/PH levels. Cola syrup
is
also added as a carbon source.
Foam covered more than 25% of the aeration basin surfaces: however. no operational
issues were observed in the downstream treatment units/processes.
Chemical Feed
Is containment adequate?
Is storage adequate?
Yes No NA NE
❑ ❑ ❑
❑ ❑ ❑
Page# 7

Permit: NC0030210
Inspection Date: 02/11/2019
Chemical Feed
Are backup pumps available?
Is the site free of excessive leaking?
Comment:
Second r—Clarifier
Is the clarifier free of black and odorous wastewater?
Owner - Facility: Mallard Creek WWrP
Inspection Type: Compliance Evaluation
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 return rate acceptable (low turbulence)?
Is the overflow clear of excessive solids/pin floc?
Is the sludge blanket level acceptable? (Approximately'/4 of the sidewall depth)
Comment: All four secondary clarifiers were operational and in service.
Pum s-RAS-WAS
Are pumps in place?
Are pumps operational?
Are there adequate spare parts and supplies on site?
Comment:
Filtration (High Rate Tertiary)
Type of operation:
Is the filter media present?
Is the filter surface free of clogging?
Is the filter free of growth?
Is the air scour operational?
Is the scouring acceptable?
Is the clear well free of excessive solids and filter media?
Comment: All four traveling, brid a tertiary filters were operational and in service.
Yes No NA NE
❑ ❑ ❑
Yes No NA NE
■ ❑ ❑ ❑
❑ ❑ ❑
■❑❑❑
❑ ❑ ❑
❑ ❑ ❑
❑ ❑ ❑
■ ❑ ❑ ❑
■ ❑ ❑ ❑
❑ ❑ ❑
❑ ❑ ❑
■ ❑ ❑ ❑
Yes No NA NE
■ ❑ ❑ ❑
■❑[In
■ ❑ ❑ ❑
Yes No NA NE
Down flow
❑ ❑ ❑
❑ ❑ ❑
❑ ❑ ❑
❑ ❑ Ei. ❑
■ ❑ ❑ ❑
LF ❑ ❑ ❑
Page# 8

Permit: NCO030210
Inspection Date: 02/11/2019
Owner - Facility: Mallard Creek wwrP
Inspection Type: Compliance Evaluation
Flow Measurement - Effluent
Yes No NA NE
# Is flow meter used for reporting?
i
❑
❑
❑
Is flow meter calibrated annually?
0
❑
❑
❑
Is the flow meter operational?
■
❑
❑
❑
(If units are separated) Does the chart recorder match the flow meter?
❑
❑
❑
Comment: The flow meter is calibrated annually and was last calibrated on 7/16/188 bv Ex;
ert Services
International LLC.
Disinfection - UV
Yes No NA NE
Are extra UV bulbs available on site?
®
❑
❑
❑
Are UV bulbs clean?
i
❑
❑
❑
Is UV intensity adequate?
S
❑
❑
❑
Is transmittance at or above designed level?
M
❑
❑
❑
Is there a backup system on site?
❑
❑
E
❑
Is effluent clear and free of solids?
E
❑
❑
❑
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? N ❑ ❑ ❑
If effluent (diffuser pipes are required) are they operating properly? ❑ ❑ ❑
Comment: The effluent appeared clear with no floatable solids and foam entrained air . The foam
dissipated less than 100 yards downstream of the discharge outfall. The receiving. stream
did not appear to be negatively impacted.
Anaerobic Di ester
Yes No NA NE
Type of operation:
Fixed cover
Is the capacity adequate?
M
❑
❑
❑
# Is gas stored on site?
M
❑
❑
❑
Is the digester(s) free of tilting covers?
M
❑
❑
❑
Is the gas burner operational?
M
❑
❑
❑
Is the digester heated?
❑
❑
❑
Is the temperature maintained constantly?
■
❑
❑
❑
Is tankage available for properly waste sludge?
M
❑
❑
❑
Page# 9

Permit: NCO030210
Inspection Date: 02/11/2019
Anaerobic Digester
Owner - Facility: Mallard Creek WwrP
Inspection Type: Compliance Evaluation
Yes No NA NE
Comment: The facility is equip ed with five di esters 4 — primary/fixed cover and 1 —
secondary/floating cover). The facility is currently using four di esters 3 —
Primary and 1 —
secondarvl.
Solids Handling Equipment
Yes
No NA NE
Is the equipment operational?
■
El
El
❑
Is the chemical feed equipment operational?
Is storage adequate?11
.
El
❑
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?
Comment: The fa -ility is ea uipped with four centrifuges 2-thickeningand 2-dewaterin
and a covered
bio-solids storage Pad. Most )l the ilt,iii:lgle dryinci beds are not in service but
a few beds
may be used durinq maintenance activities such as scum 12it cleaning (prima
Y clarifier).
etc.
Dewatered bio-solids are land apolied by a contracted comp—,S na ro under the
authority of Permit No. W00000057.
Standby Power
"
Yes No NA NE
Is automatically activated standby power available?
11
❑
Is the generator tested by interrupting primary power source?
❑
Is the generator tested under load?
■
❑
Was generator tested & operational during the inspection?
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: The facilityhas one enerator in service and two enerators that have been taken out of
service. The enerator is (21 ()[ficl:illv tested under load serviced b 1
a contracted company
Carolina CAT twice Per year.
Page# 10

CHARLOTTE
W(,TER
MERCURY MINIMIZATION PLAN
Charlotte Water (CLTWater) serves approximately 260,578 households and businesses in Mecklenburg
County that discharge wastewater directly to the sanitary sewer (Wastewater Performance Report, 2018).
Customers are categorized as either commercial or residential in the billing system. Dentists, once
considered the only major contributor of mercury to the wastewater collection system, have the potential
to pollute the sanitary sewer with waste from the installation or removal of dental amalgam. However,
other industries are also potential contributors of this pollutant. This Mercury Minimization Plan is an
outline to facilitate a minimization in the levels of mercury entering the sanitary sewer system. In the data
analysis for the wastewater system, the goal is to target areas of concern as the basin -specific data
experiences an upward trend in relation to the Baseline Study.
METHODOLOGY
The MMP focus is on the individual basin trends. The five wastewater plants operated by CLTWater are
Mallard Creek, McDowell Creek, Irwin Creek, Sugar Creek and McAlpine Creek wastewater treatment
plants. Additional monitoring sites are located strategically throughout the collection system. When
upward trends of five percent above the baseline influent data for the basin occur, further action may be
taken to minimize the potential impact of the pollutant on the ecosystem. The baseline was determined by
averaging three calendar years' data for each plant. Some other industries, such as laboratories,
hospitals, schools and factories could affect the wastewater collection system with mercury. Although
they may not hold an SIU permit, an annual chemical inventory may be required if upward trends warrant
increased action.
THE PLAN
Mercury comes from a variety of sources. Identifying these sources is the key to a successful
minimization plan. Depending upon the data trends in each wastewater basin, an annual review of the
following steps will determine the level of action for the upcoming year:
1. The Assessment — Annual Report generated by CLTWater, including the removal rates for the
wastewater treatment plants.
2. Monitoring — Periodic wastewater data review for the wastewater treatment plants, continuous
industrial waste survey process, sampling and increased inspection frequencies as trends dictate.
3. Potential contributors — identification of the different users located in each.basin.
4. Educational Outreach - Oral and written communication to the community about findings and
increased efforts to reduce mercury pollution.
5. Internal Assessments — including, but not limited to, review of Spill Control Plans, Chemical Hygiene
Plans and safety for employees periodically in Laboratory Services.
For more information about mercury, please refer to the 2018 Mercury Assessment.
1 MERCURY MINIMIZATION PLAN

CHARLOTTE
W,..-:,TER
THE ASSESSMENT
Annually, CLTWater performs an assessment of the potential contributors of mercury to the collection
system and publishes the findings. The assessment includes newly identified potential contributors, as
well as known contributors of any level of mercury to the wastewater collection system. Known
contributors that have a Significant Industrial User (SIU) permit limit should take the necessary actions
outlined in their permit if their discharge exceeds the permit limit for mercury. These facilities are
inspected once annually and the Compliance Specialist assigned to that industry should be notified if
changes in the chemical inventory or process have the potential to affect the wastewater effluent of the
facility. From the reported information, it can be determined if any changes need to be made to the permit
limits. Industries that hold an SIU permit should also respond to the wastewater survey provided them by
their designated Compliance Specialist once every five years and keep track of any chemicals that
contain mercury by performing a comprehensive chemical inventory, using Material Safety Data Sheets
housed onsite. The annual inspection sheet has one new question concerning mercury to keep the
industry mindful of the potential impact the pollutant could have on the collection system.
MONITORING
Based on data from 2018, CLTWater's five wastewater plants currently average a 98.94% removal rate
for mercury from the influent stage of treatment to the effluent stage. The data from each wastewater
basin will be reviewed periodically for trending. If the data is in an upward trend for any of the five basins,
additional measures may be activated to curb those trends. These measures may include additional
inspections or sampling in the collection system to determine the contributors. Once it is determined the
level of contribution by the industries, then a plan of action may include methods of reducing the mercury
levels leaving the facility, implementation of Best Management Practices to prevent reoccurrence of the
pollutant discharge and monitoring onsite at the expense of the industry, as needed. To verify that the
efforts are working, a routine sampling program may be required for the facilities found to have elevated
levels of mercury in their wastewater effluent.
POLLUTION PREVENTION
For pollution control, an inventory of items listed as pollutants can aid residents in reducing their negative
environmental impact on the collection system. Keeping in mind that the sanitary sewer system collects
waste from all wastewater users in Mecklenburg County that are connected to the City sewer, every little
bit of minimization helps with the overall health of the system. Any household items found to contain
mercury need to go to the nearest drop-off location for disposal. Never discharge these items to the
sanitary sewer system.
2 MERCURY MINIMIZATION PLAN

CHARLOTTE
W(,TER
COMMON SOURCES OF MERCURY
Looking around the house, one would not think mercury is a potential hazard that is a source of concern.
Yet, there is an increase in the number of manufactured items that contain mercury. Below is a list of
common household items that contain mercury:
-Button Cell batteries- coin shaped, small electronic batteries
-Light Bulbs: Fluorescent, compact fluorescent (CFL), high intensity discharge (HID), and UV
-Thermometers
-Old Thermostats
-Some car parts
-Old appliances: chest freezers, hot water tanks, heat pumps, space heaters, washers and dryers
EDUCATIONAL OUTREACH
Keep Mecklenburg Beautiful hosts an annual recycling day each November 15. At this event Mecklenburg
citizens engage in recycling activities that result in improving their community environments. On the
charmeck.org website CLTWater customers can find drop-off locations for common household items
containing mercury, such as: compact fluorescent lights (CFLs), old thermostats, and house appliances.
The website also provides information not only for residential CLTWater customers, but also provides
education on Mercury minimization efforts for the area's commercial customers. There are four Recycling
Centers across Mecklenburg County. Items such as household appliances, compact fluorescent lights,
herbicides, and yard debris can be brought to the recycling centers. CLTWater customers may also find
information concerning the proper disposal of items by visiting the link:
htt)s://www.mecknc. ovILUESAISol!dWastelDis osal-Rec clin IPa es/Household-Hazardous-
Waste.aspx
INTERNAL ASSESSMENT
CLTWater has several checks and balances in place to ensure it is doing all it can to prevent the
introduction of Mercury into our collection system. Four of the five Wastewater treatment plants disinfect
the wastewater with Ultraviolet light. When the UV bulbs are replaced, and if they are still under
manufacturer warranty they are returned to the manufacture (Xylem). If the bulbs are spent or no longer
under manufacturer warranty the bulbs are packaged, and taken one of the four Recycling Centers
located in Mecklenburg County. Any fluorescent or CFL bulbs used by the plants are also taken to the
Recycling Center. The Wastewater plants have transitioned from using thermometers and manometers
that contain Mercury. Property Management and Lab Services assisted the plants in the equipment
changeover. Each Plant has.an Approved Spill Control Plan and Chemical Hygiene Plan in place.
Charlotte Water Laboratory Services Division analyzes over 200,000 wastewater and drinking water
samples annually. Lab Services has a contract with CHEMTRON Corporation. CHEMTRON is contacted
by Lab Services to collect and dispose of chemical hazards. Different areas within the lab use chemicals
for sample preservation and in instrumentation calibration standards. Once the samples have been
properly analyzed and validated, the samples containing Mercury are disposed via laboratory sinks. Lab
analysts will continually run water while "dumping' samples down the drain. The sample bottles are
rinsed with water, and placed in the proper Recycling Containers. All heavy metals calibration standards
are picked up by CHEMTRON.
31 MERCURY MINIMIZATION PLAN

CHARLOTTE
iN .TER
Lab Services has begun using rechargeable Lithium batteries for select pieces of analytical equipment.
There has been a Recycling Program set in place for the spent rechargeable and spent alkaline batteries.
The batteries will be stored in a marked container, and stored until a drop - off date has been chosen. A
member of the Laboratory Services field staff will drop the batteries off for recycling at a Batteries Plus
location within the Charlotte area.
41 MERCURY MINIMIZATION PLAN

NPDES/A uifer Protection Permittins Unit Pretreatment Information Request Form
PERMIT WRITER COMPLETES THIS PART:
PERMIT WRITERS -AFTER you get this form back'
Check all that apply from PERCS:
- Notify PERCS if LTMP/STMP data we said should be
Date of Reg uest 4/26/2019
municipal renewal X on DMRs is not really there, so we can get it for you
Requestor Nicholas Coco
new industries (or NOV POTW).
Facility Name Mallard Creek WRF
WWTP expansion X - Notify PERCS if you want us to keep a specific POC
Permit Number NCO030210
Speculative limits in LTMP/STMP so you will have data for next permit
R ion Mooresville
renewal.
stream reclass. - Email PERCS draft permit, fact sheet, RPA
Basin Yadkin Pee Dee
outfall relocation - Send PERCS paper copy of permit (w/o NPDES
7Q10 change boilerplate), cover letter, final fact sheet. Email RPA if
other changes.
other
check applicable PERCS staff:
Other Comments to PERCS:
y BIRD, CPF, CTB, FRB, TAR - Vivian Zhong (807-6310
Facility is rated 12.0 MGD wtih 3 CIUs listed in its application. The facility
has applied for a multi -tiered expansion with tiers of 13.1 MGD, 14.9 MGD
CHO, HIW, LTN, LUM, NES, NEW, ROA, YAD
and 16.0 MGD _Water quality modeling has been submitted and reviewed
- Monti Hassan (807-6314)
and speculative limits have been provided.
PERCS PRETREATMENT STAFF COMPLETES THIS PART:
Status of Pretreatment Program (check all that apply)
1) facility has no SIU's, does have Division approved Pretreatment Program that is INACTIVE
2) facility has no SIU's, does not have Division approved Pretreatment Program
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
Flow, MGD
Permitted
Actual
Time period for Actual
STMP time frame:
Industrial
0.1998
0.085
2016-2017
Most recent:
Uncontrollable
n/a
9.145
2016-2017
Next Cycle:
d
IL
Parameter of
POC due to
NPDES/ Non-
Required by
Required
POC due
POTW POC
STMP
LTMP
f
Concern (POC)
Disch Permit
EPA*
by 503
to SIU
(Explain
Effluent
EffluentCheck
List
Limit
Sludge**
below)**-
Freq
Freq
Q = Quarterly
M = Monthly
'
BOD
TSS
v
M
M
NH3
M
Arsenic
V
M
d
Cadmium
M
�!
Chromium
M
Copper
ti
M
4
C anide
M
Is all data on DMRs?
Lead
M
YES
IX
d
Mercury
7
M
NO (attach data)
Molybdenum
M
J
Nickel
M
Silver
M
Selenium
M
Zinc
M
Is data in spreadsheet.
Total Nitrogen
M
YES email to writer
Phosphorus
M
NO
IX
COD
M
O&G
i M
M
M
*Always in the LTMP/STMP
** Only in LTMP/STMP if sludge land app or composte (dif POCs for incinerators)
*** Only in LTMP/STMP while SIU still discharges to POTW **** Only in LTMP/STMP when pollutant is still of concern to POTW
Comments to Permit Writer (ex., explanation of any
POCs: info You have on IU related investigations into NPDES problems):
O&G only sample at influent and primary clarifier effluent.
PERCS_NPDES_Pretreatment.request.lbrm.Apfl20l9 (002)
Revised: July 24, 2007

CHARLOTTE
WLTER
February 13, 2019
Julie Grzyb, Supervisor
NPDES Complex Permitting Unit
Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Request for NPDES Permit Renewal and Future Expansion
Mallard Creek Water Reclamation Facility (MCWRF) - NCO030210
Dear Ms. Grzyb:
Please let this letter serve as CLTWater's formal request to renew the above referenced permit at the
existing monthly average flow of 12 MGD. We are also requesting approval for the expansion of MCWRF
to a monthly average flow of 16 MGD while maintaining the existing effluent concentration limits for
CBOD and ammonia. This is based on the recently completed water quality modeling analysis that
concluded that MCWRF's existing concentration limits would be fully protective of dissolved oxygen
(DO) in Mallard Creek and the Rocky River under these higher discharge rates.
Because of schedule and competing funding priorities we would like to phase this expansion and have
the applicable permit limit pages issued at the flows listed in Table 1. Table 1 also identifies the projects
CLTWater should undertake to reach the expanded flow limits.
Table 1. Phased Expansion Flows and Associated Projects for Mallard Creek WRF
Monthly Average
Flow, MGD
Necessary Projects for Requested Capacity
• Modify biological treatment train 3 diffuser grids
13.1(Phase 1A)
Construct new blower building with new blowers to serve
train 3
14.9 (Phase 1)
• Build new Influent Pump Station (IPS) with new screens
Build a new offline flow equalization (EQ) basin and
decommission existing EQ
• Implement advanced aeration control strategies
Construct additional alkalinity storage and feed facilities
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
Operated by the City of Charlotte

16 (Phase 2) I • Upgrade the existing blowers, their electrical gear, and
replace/refurbish existing underground air piping
• Construct Primary Clarifier 6 and Final Clarifier 4
• Perform effluent piping improvements
The speculative limits request (Sept. 26, 2018), the subsequent water quality modeling analysis (Jan. 14,
2019), and the Engineering Alternatives Analysis (EAA, Jan. 24, 2019) discussed flow increments of 14.9
MGD and 16 MGD. Because of growth in the basin and wetter than usual conditions, the MCWRF has
experienced monthly average flows approaching the currently permitted monthly average flow limit of
12 MGD. As a result, the Phase 1A flow of 13.1 MGD as a monthly average flow listed in Table 1 was
added to the other two flow values as a capacity that can be met by implementing a near term project
with a relatively small scope and short schedule.
We look forward to receiving Mallard's speculative effluent limits, and we stand ready to
provide any additional information that may be needed to process our request for renewal and
expansion. If you have any questions concerning this request, or if you need any additional
information, please feel free to call Shannon Sypolt, Water Quality Program Administrator, at
704/634-6984 or me at 704/336-5433. Thank you for your assistance with Mallard's permit
renewal.
Respectfully,
a q eline A. Jarrel E.
operations Chief, Environmental Management
Charlotte Water
Cc: S. Sypolt, J. Lockler, H. Eudy
Charlotte Water 5100 Brookshire Blvd, Charlotte, NC 28216 charlottewater.org
Vb operated by the City of Charlotte

-t�r � f.
ROY COOPER
Governor
MICHAEI, S. REGAN
Secretary
Environmentai
Quality
June 15, 2018
George Anipsitakis, PE, Project Manager
Brown and Caldwell, Charlotte Office
309 East Morehead Street; Suite 160
Charlotte, NC 28202
Subject: Charlotte Water Mallard Creek Water Reclamation Facility Expansion
State Environmental Policy Act (SEPA)
DEQ Response
Dear Mr. Anipsitakis,
I have received your letter dated June 12, 2018 requesting written concurrence from the North Carolina
Department of Environmental Quality (NCDEQ) if an Environmental Assessment (EA) or other
environmental information document is required for a future wastewater treatment plant (WWTP)
expansion project at the Mallard Creek WWTP.
As you are fully aware, State Environmental Policy Act (SEPA) Session Law 2015-90 was passed in June
2015. In summary, the law reads that any project that has an expenditure of > $10,000,000 of state
funds or land disturbance of > 10 acres of public lands, could be subject to SEPA. DEQ's minimum
criteria is the final decision maker to determine if SEPA applies and identifies who will be the lead
agency.
Based on the information provided, we agree with your summation. The project as described does not
meet the new SEPA criteria and an environmental document is not required.
If the projects should change, please reach out to us again to discuss the changes and determine if the
SEPA requirements have been triggered. You can reach me at 252-948-3842 or
[e-mail].
Thank you for the opportunity to respond.
Respectfully,
Lyn Hardison
Environmental Assistance and SEPA Coordinator
Division of Environmental Assistance and Customer Service
Cc: Irene (Tesha) Okioga, Charlotte Water
Julie Grzyb, NC DEQ NPDES
David Wainwright, DWR SEPA Coordinator
State of North Carolina I Environmental Quality
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Washington Regional Office 1943 Washington Square Mail I Washington, North Carolina 27889

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Project Title: Mallard Creek WRF Expansion
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Description
1
Engineering Alternatives Analysis for Mallard Creek WRF Expansion
Remarks:
cc: Prepared by: Kristin Smith
Title: Admin Coordinator
Lam[ 0 '�- JOL-R I-z"

RECEIVED/DENR/DWR
JAN 2 9 2019
Water Resources
Permitting Section
Engineering Alternatives Analysis for
the Expansion of Mallard Creek WRF
Prepared for
Charlotte Water
Charlotte, North Carolina
December 20, 2018

Engineering Alternatives Analysis for
the Expansion of Mallard Creek WR1=
Prepared for
Charlotte Water, Charlotte, North Carolina
December 20, 2018
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Brown-wCeldwell

Table of Contents
Listof Figures........................................................................................................................................................... iii
List. of Tables................................................................................................................................................................iv
Listof Abbreviations................................................................................................................................................. v
ExecutiveSummary ..................................................................................................................................................A
1. Overview of Mallard Creek Basin Wastewater Treatment...........................................................................1-1
1.1 Mallard Creek Water Reclamation Facility.........................................................................................1-1
1.1.1 Treatment Processes and Capacity......................................................................................1-1
1.1.2 Current Permit Requirements...............................................................................................1-2
1..2 Wastewater Treatment by WSACC......................................................................................................1-3
1.3 Inter -Basin Transfers ... .............. .................................................. .......................................................... 1-4
2. Speculative Effluent Limits...................:...........................................................................................................2-1
3. Justification of Need .................... ......................... ....... ...................... ........................ ..................................... 3-1
3.1 Population Projections.........................................................................................................................3-1
3.2 Flow Projections...................................................................................................................................3-2
4. Alternatives Analysis......................................................................................................................................4-1
4.1 Alternative 1 - No Action Alternative..................................................................................................4-2
4.2 Alternative 2 -- Expand MCWRF and Mallard Creek Surface Water Discharge to 16 MGD ............ 4-2
4.3 Alternative 3 Purchase 4 MGD of Additional capacity from WSACC and Convey Wastewater from
Mallard Creek WRF to RRRWWTP through the Fuda Creek Interceptor ............ ............................... 4-5
4.4 Alternative 4a - Partially Expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of Additional Capacity
from WSACC and Convey All Back Creek Flow to WSACC's RRRWWTP through the Fuda Creek
Interceptor............................................................................................................................................4-8
4.5 Alternative 4b - Partially Expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of Additional capacity
from WSACC and Convey all Back Creek Flow to WSACC's RRRWWTP through a New Back Creek
ParallelSewer...................................................................................................................................4-10
4.6 Alternative 5 - Convey 4 MGD of Wastewater from the Mallard Creek Basin to CLTWater's McDowell
CreekWRF......................................................................................................................................... 4-13
4.7 Alternative 6 - Expand MCWRF and Land Apply 4 MGD of Treated Effluent...............................4-15
4.8 Alternative 7 - Expand MCWRF and Reuse 4 MGD of Treated Effluent (Non -conjunctive Reuse)4-16
5., Present Worth Analysis..................................................................................................................................5-1
6. Conclusions....................................................................................................................................................6.1
7. Limitations .................................... ......... ........................................................................ ,.................................. 7-1
List of Figures
Figure 1-1. Aerial of MCWRF Identifying Major Existing Unit Processes............................................................1-2
Brown m caldwell

Table of Contents
Figure 1-2. Sewer Transfer Locations from CLTWater to WSACC......................................................................1-5
Figure 3-1. Mallard Creek Basin Population Projection as Equivalent Residential Population (ERP)..............3-2
Figure 3-2. Historical and Projected Flows for the Mallard Creek WRF.............................................................3-3
Figure 4-1. Alternative 2, Aerial View of Proposed Expansion at MCWRF..........................................................4-3
Figure 4-2. Alternative 3, Improvements to Convey Flow from MCWRF to WSACC's Fuda Creek Interceptor4-6
Figure 4-3. Alternative 4a, New Infrastructure Conveying Back Creek Basin Flow to WSACC's Fuda Creek
Interceptor.......................................................................................................................................................4-8
Figure 4-4. Alternative 4, New Infrastructure Conveying Back Creek Basin Flow to WSACC......................... 4-11
Figure 4-5. Alternative 5, New Infrastructure Conveying Mallard Creek Basin Flow to McDowell Creek WRF.4-13
Figure 4-6. Existing and Proposed Water Reuse Distribution Network Originating from MCWRF................. 4-17
List of Tables
Table ES-1. Summary of Alternatives.....................................................................................................................vi
Table ES-2. Summary of Cost and NPV of Evaluated Alternalives........................................................................vii
Table 1-1. Mallard Creek WRF Effluent Quality Discharge Standards...............................................................1-2
Table 1-2. Mallard Creek WRF Reclaimed Water Standards ................ ................................................... ...........
1-3
Table3-1. Typical Unit Flow Rates........................................................................................................................3-2
Table 3-2. Wastewater Demand and Treatment Capacity Triggers........... . ............. ...........................................
3-3
Table4-1. Summary of Alternatives..................................................................................................................4-1
Table4-2. Assumed Capital Cost Factors.............................................................................................................4-1
Table 4-3. Alternative 2 Capital Cost Summary ..................................................................................................4-4
Table 4-4. Alternative 3 Capital Cost Summary ...................................................................................................4-7
Table 4-5. Alternative 4a Capital Cost Summary .................................................................................................4-9
Table 4-6. Alternative 4b Capital Cost Summary ..............................................................................................
4-11
Table 4-7. Alternative 5 Capital Cost Summary .......... ......................................................................................
4-14
Table 4-8. Land Application Design Criteria (Monthly Average)......................................................................4-15
Table 4-9. Alternative 6 Capital Cost Summary ...............................................................................................
4-16
Table 4-10, Alternative 7 Capital Cost Summary .............................................................................................. 4-18
Table 5-1. Summary of Costs and NPVs of the Alternatives Evaluated..............................................................5-1
BrownAwCaldwell
R

List of Abbreviations
AADF Annual Average Daily Flow
AB
Aeration Basin
ABW
Automated Backwash
AX
Anoxic
BOD5
5-day Biological Oxygen Demand
CIP
Capital Improvements Plan
CLTWater
Charlotte Water
DEQ
Department of Environmental Quality
DO
Dissolved Oxygen
EA
Environmental Assessment
EAA
Engineering Alternatives Analysis
EQ
Equalization
ERP
Equivalent Residential Population
FC
Final Clarifier
FY
Fiscal Year
IBT
Interbasin Transfer
IPS
Influent Pump Station
LF
Linear feet
MGD
million gallons per day
MMF
Maximum Monthly Flow
NCAC
North Carolina Administrative Code
NPDES
National Pollution Discharge Elimination
System
NPV
Net Present Value
NTU
Nephelometric Turbidity Unit
0/H
Overhead
O&M
Operation & Maintenance
PC
Primary Ciarifier
PCB
Poychlorinated Biphenyls
PHF
Peak Hourly Flow
RAS
Return Activated Sludge
RRRWWTP Rocky River Regional Wastewater
Treatment Plant
SEPA
State Environmental Policy Act
TAN
Total Ammonia Nitrogen
TAZ
Transportation Analysis Zone
TSS
Total Suspended Solids
UV
Ultraviolet
WRF
Water Reclamation Facility
Table of Contents
WSACC Water and Sewer Authority of Cabarrus
County
BrowwwcaWwelt
4

Executive Summary
The Mallard Creek Water Reclamation Facility (MCWRF) treats wastewater from a growing area in the
northern part of Mecklenburg County. The MCWRF service area includes wastewater generated within the
Mallard Creek and Back Creek sewer basins. Treated wastewater is discharged to Mallard Creek under
NPDES Permit NC0030210. Maximum Monthly Flows (MMF) are expected to exceed the permit limit of 12
Million Gallons per Day (MGD) by 2021 and reach 16 MGD by 2030.
This Engineering Alternatives Analysis (EAA) was prepared to support CLTWater's NPDES application for
expanding the MCWRF discharge. This document was prepared in accordance with North Carolina (NC)
Department of Environmental Quality (DEQ) guidelines. revised April 20141.
Population and flow projections were developed and evMuaxed in conjunction with historical flow trends in
the MCWRF service area. The projected wastewater flow analyses demonstrate the need to increase the
MCWRF treatment capacity to 16 MGD on a maximum monthly flow (MMF) basis (15A NCAC 21-1.105 (c)(1)).
This EAA for the expansion of Mallard Creek WRF provides justification for expanding the effluent discharge
to Mallard Creek by 4 MGD, from 12 to 16 MGD. The assessment demonstrates that expanding the
Mallard Creek direct discharge is the most environmentally sound and cost-effective alternative (15A NCAC
21-1.105 (c)(2)). Table ES-1 summarizes the alternative wastewater treatment and disposal options that
were assessed.
Alternative 1 No Action Alternative
Alternative 2 1 Expand MCWRF and Mallard Creek surface water discharge by 4 MGD (selected alternative)
Alternative 3 Purchase 4 MGD of additional capacity from WSACC and convey wastewaterfrom Mallard Creek
WRF to RRRWWTP through the Fuda Creek Interceptor
Alternative 4a Partially expand MCWRF by 2.9 MGD. Purchase 1.2 MGD of additional capacity from WSACC and
convey all Back Creek Flow to WSACC's R1111YA rp through the Fuda Creek Interceptor
Alternative 0 Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of additional capacity from WSACC and
convey all Back Creek Flow to WSACC's RRRWWTP through a New Back Creek Parallel Sewer
Alternative 5 Convey 4 MGD ofwastewaterfrom the Mallard Creek. Basin to'CL1Watets McDowell Creek WRF
Alternative 6 Expand MCWRF and land apply 4 MGD of treated effluent
Alternative T Expand MCWRF and reuse 4 MGD of treated effluent.
Alternative 1, the No Action Alternative, will not provide treatment capacity to keep pace with growth in the
basin and is not an environmentally sound, sustainable solution,
Alternative 2 is the selected alternative and forms the basis for increasing the permitted discharge for
MCWRF to 16 MGD. Alternative 2 presents the lowest capital and operation and maintenance (0&M) costs,
and most favorable net present value (NPV) compared to Alternatives 3 through 7. The NPV analysis is
summarized in Table ES-2. Alternatives 3 through 7 do not require a 4 MGD MMF increase in the MCWRF
permitted surface water discharge. These alternatives require significant conveyance infrastructure that
involves major property acquisitions, land disturbance. 'and/or potential environmental impacts.
tt• 1 .• •1 \�� t' 11 �.1. IraI I • . • t••' ••i
Brownm Caldweil

EAA for the Expansion of Mallard Creek WRF
Executive Summary
Alternative 2 includes a two -phased expansion of MCWRF to 16 MGD MMF, with continued surface water
discharge through an expanded NPDES permit. Required improvements to MCWRF can be constructed on
the existing site, with minimal land disturbance or environmental impact as compared to other alternatives.
Altemative I Destxiption
Capital Costs
0 20-year 0&M Costs
20-year NPV
1 No Action Alternative
NA
NA
NA
2 Expand MCWRF and Mallard Creek surface water discharge by 4
i $78,120,000
$16,700,000
$(94,960,000)
MGD (selected alternative)
Purchase 4 MGD of additional capacity from WSACC and convey
3 wastewater from Mallard Creek WRF to RRRWWTP through the
$88.670,000
$28,390,000
S(123,500,000)
Fuda Creek Interceptor
Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of
4a additional capacity from WSACC and convey all Back Creek Fiow
$85,510,000
$19,915,000
$(107,590,000)
(1,1 MGD) to WSACC's RRRWWTP through the Fuda Creek
Interceptor
Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of
0 additional capacity from WSACC and convey all Bads Creek Flaw
$96,150,000
$18,996,000
$(115,540,000)
(1.1 MGD) to WSACC°s RRRWWTP through a New Back Creek
Parallel Sewer
5 Convey 4 MGD of wastewater from The Mal'kard Creek Basin to
583,240,000
$24,215,000
$(110,260,000)
CLIWatees McDowell Creek WRF
6 Expand MCWRF and land apply 4 MGD oflreated effluent
, $266,680,000
$20,040.000
$(275,320,000)
7 Expand MCWRF and reuse 4 MGD of treated euent.
$277,250,000
$16,700,000
$(278,790,000)
NA: The No Action Alternative was not considered to be technically feasible and no NPV was calculated.
The proposed MCWRF expansion is not subject to State Environmental
Policy Act (SEPA) review. As such,
this EEA is a standalone document and does not include a
SEPA Environmental Assessment (EA) study.
BrownAwCaldwell

Section I
Overview of Mallard Creek Basin
Wastewater Treatment
1A Mallard Creek Water Reclamation Facility
CLTWater owns and operates the Mallard Creek Water Reclamation Facility (MCWRF) located at
12400 US Highway 29 North, Charlotte, NC 28262. The current facility is permitted to treat 12
million gallons per day (MGD) of wastewater generated on a monthly average basis and a peak day
flow of 24 MGD, Treated water is discharged into Mallard Creek, a class C water in the Yadkin -Pee
Dee River Basin.
1.1.1 Treatment Processes and Capacity
The original facility consisted of primary sedimentation, and roughing filters followed by a two -stage
activated sludge process with intermediate and final clarifiers. The final effluent was polished in a
lagoon followed by disinfected with chlorine gas prior to discharge. Solids were anaerobically
digested and then dewatered on sludge drying beds. The roughing filters have since been
demolished and the chlorine contact tanks abandoned. In 1990, the two -stage process was
converted into parallel treatment trains that included the addition of pre -anoxic reactors and oxic
recycle. The intermediate clarifiers and the original final clarifiers were converted into additional
aerobic capacity and new final clarifiers were built. In 1999, a third treatment train with pre -anoxic
zones and oxic recycle with dedicated primary and final clarifiers were added to increase the rated
capacity to 12 MGD. The most recent upgrades (2014) included interconnecting all the treatment
trains so that they receive common influent and return activated sludge (RAS). An aerial of the
MCWRF is provided in Figure 1-1. Major upgrades to the MCWRF have been as follows:
1979: Mallard Creek WRF commissioned.
1990: Primary clarifier added, two -stage process converted in parallel treatment trains,
intermediate and final clarifiers converted to aeration tanks, new final clarifiers built, and final
effluent filters added with ultraviolet (UV) disinfection and post aeration. Capacity expanded to 6
MGD.
1992: Anoxic selectors and oxic recycle added to biological treatment trains, polishing lagoon
converted to offline equalization (EQ) basin, and centrifuge sludge dewatering and covered
sludge storage added.
1998: Capacity expanded to 8 MGD by the addition of a primary clarifier.
1999: Capacity expanded to 12 MGD by the addition of Train 3 and dedicated primary and
secondary clarifiers, new headworks built that included coarse and fine bar screens, influent
pumping station (IPS), EQ day tanks, and transfer pumping, anaerobic digester added, and final
effluent filters added.
2014: Secondary clarifier added, all biological treatment trains interconnected, and oxic recycle
capacity added to Trains 1 and 2.
BrownmwCaldwell
1-1

EAA for the Expansion of Mallard Creek V4RF Section 1
Figure 1-1. Aerial of MCWRF Identifying Major Existing Unit Processes
1.1.2 Current Permit Requirements
The MCWRF is currently permitted for a rated capacity of 12 MGD average monthly flow. Operation of
MCWRF is subject to state and federal regulations as stated in the State of North Carolina
Department of Environmental and Natural Resources Division of Water Resources National Pollution
Discharge Elimination System (NPDES) permit NC0030210. This permit went into effect on January
1, 2014 and expired November 30, 2018. Table 1- summarizes the effluent quality standards as
stated in the existing permit.
Effluent Umbdons
Parameter
—
-
Monthly Average
Weekly Average
Flow
12 MGD
CBODs, (20°C) [April 1- October3l]
4.2 mg/L
6.3 mg/L
CBOD5, (20°C) [November 1-- March 31]
_ 8.3 mg/L
12.5 mg/L
TSs
30 mg/L
45 mg/L
BrownAwCaldwell ,••
1_7

EAA for the Expansion of Mallard Creek WRF
1-1. Mallard Creek WRF Eff luent
Quality Discharge
StandardsTable
Effluent L1mRations
Parameter
Monthly Average t Weekly Average
Total Ammonia Nitrogen (I•AN) [April 1- October 31]
1.0 mg/L 3.0 mg/L
Total Ammonia Nitrogen (rAN) [November 1- March 31)
2.0 mg/L 6.0 mg/L
Dissolved Oxygen (DO)
Daily Average > 6.0 mg/L
Fecal Coliform
200/100 ml. 400/100 mL
pH
Between 6 and 9 Standard Units
Section 1
MCWRF also has a non -discharge system permit WQ0013252 for 4 MGD MMF of type 1 reclaimed
water, which is suitable for irrigation of golf courses, sports fields, and crops for animal feed. The
existing reclaimed water users have a combined total peak instantaneous demand of 3.6 MGD.
Table 1- lists the effluent quality standards as stated in the existing non -discharge permit. The
effluent TSS, fecal coliform, and pH parameters are more stringent in the non -discharge reclaimed
water permit versus the values in the discharge permit. The TSS limit is met by secondary
clarification and tertiary filtration, the pH limit is met by alkalinity addition upstream of the aeration
basins. Fecal coliform reduction (disinfection) is accomplished by a combination of UV radiation and
chlorination.
Table 1-2. Mallard Creek WRF Reclaimed Water Standards
Parameter Effluent Litrittations
MonthlyAverage D.
Flow 4 MGD
TSS 5 mg/L 10 mg/L
Turbidity - 10 NTU
TAN 4.0 mg/d. 6.0 mg/L
Fecal Coliform
pH
14/ 100 ml. 25/ 100 ml.
6.5 - 8.5 8.5
1.2 Wastewater Treatment by WSACC
In addition to treatment at the MCWRF, a portion of the wastewater generated in the Mallard Creek
basin is currently conveyed eastward to the Rocky River basin for treatment at the Rocky River
Regional Wastewater Treatment Plant (RRRWWTP) operated by the Water and Sewer Authority of
Cabarrus County (WSACC). This conveyance occurs through eight locations listed below and depicted
on Figure 1-2. These locations are.
• Highland Creek (HC3)
• Highland Creek (HC4)
• Clark Creek
• QRPS Rocky River
• URR1 Rocky River
• Reedy Creek
• Crozier Branch
• McKee Creek.
Brown►mcedwell
1-3

EAA for the Expansion of Mallard Creek wRF
Section 1
There is an agreement between CLTWater and WSACC covering these flow transfers. Per the
agreement, the City of Charlotte (CLTWater) is authorized to discharge up to 6 MGD of wastewater to
the RRRWWTP on a monthly average basis. Per the agreement, CLTWater has up to 12 MGD of
secured capacity at the RRRWWTP and can obtain authorization to discharge up to this flow limit in
the future after a payment is negotiated. Flow meters are installed at the transfer locations. Flow
transfer occurs by gravity at most locations, and although flows are monitored, there are no flow
controls. Currently. approximately 3.6 MGD of flow is sent to RRRWWTP leaving 2.4 MGD of
available contracted capacity.
1.3 Inter -Basin Transfers
Both the Mallard Creek and Back Creek sewers convey wastewater to the MCWRF for treatment.
Water supply for both the Mallard Creek and Back Creek basins comes from the Catawba River.
Wastewater is discharged from Mallard Creek WRF into the Yadkin -Pee Dee River Basin In
accordance with an Inter -Basin Transfer (IBT) Agreement. The IBT Agreement limits the amount of
water supplied from the Catawba River to sewer basins that discharge into the Yadkin -Pee Dee River
Basin to 33 MGD max day water demand. which corresponds to approximately 20 MGD maximum
monthly discharge limit at the MCWRF. For pinnnirg purposes, it was assumed that the IBT limit
would be reached by 2040 under current growth scenarios. Treatment and conveyance solutions to
address wastewater demand in the Mallard and Back Creek Basins include impacts relative to the
IBT Agreement. However, the NPDES permit expansion to 16 MGD will not exceed the IBT limit.
BrownAwCaldwell
1-4

EAA for the Expansion of Mallard Creek WRF
Section 4
Rgure 12. Sewer Transfer Locations from CLTWater to WSACC
Brown—Caldwett
1-5

Section 2
Speculative Effluent Limits
BC submitted a water quality modeling approach to NCDEQ in March 2018 and received a no
comment response in May 2018, NCDEQ approved a phased modeling approach, which includes
updating the model parameters and conducting a sensitivity analysis to demonstrate that existing
effluent limits are acceptable, The water quality model includes Mallard Creek, as well as flows from
over 20 other tributaries along the Rocky River. Water quality modeling, concluded in August 2018,
demonstrated that MCWRF's existing permit limits for CBOD5 and ammonia would be fully protective
of dissolved oxygen (DO) in Mallard Creek and the Rocky River under higher discharge rates (15
MGD MMF).
Speculative effluent limits were requested from NCDEQ in September 2018.
BrownAwCatdwetl
2-1

Justification of Need
MCWRF treats wastewater from a growing area in the northern part of Mecklenburg County. The
MCWRF service area includes wastewater generated within the Mallard Creek and Back Creek sewer
basins. Maximum monthly flows are expected to exceed the permit limit of 12 MGD by 2021 and
reach 16 MGD by 2030.
3.1 Population Projections
In May 2017, BC developed population and flow projections as part of the Mallard Creek Sewer
Basin Study commissioned by CLTWater to evaluate area growth and plan the timing and scope of
future system improvements. Various master planning studies have been performed for areas within
the Mallard Creek Basin and have been maintained by Charlotte Planning Department. The following
studies were reviewed to better understand the timing and densities associated with future
development:
• University Research Park Area Plan
• University 0ty Area Plan
• University of North Carolina - Charlotte (UNCC) Master Plan
• Applied Innovation Corridor Community Investment Plan
• Blue Line Extension Study
Meetings were held with the City of Charlotte Planning Department and UNCC to discuss study
details and relevant planning information. Based on these discussions, growth near UNCC in Mallard
Creek Basin including the University City Area, University Research Park and along the Blue Line
Extension of the flight rail is expected. Growth projection forecasts were provided for each
Transportation Analysis Zone (TAZ) in the Mallard Creek Basin in 5-year increments up to the year
2040 and 10-year increments up to the year 2070. Given that growth and development vary with
the economy and other external factors, a range of population and flow projections were developed:
• Build -Out Population at Maximum Development Density. The estimated basin population if the
entire basin were developed to the maximum future -land use density is 646,000 persons.
Future Land Use Population Projections. This is the population growth curve from current
population to reaching the Maximum Development' Density by 2070. Steeper growth was
assumed in early planning years (through 2040) for areas near UNCC and alongthe Blue Line
extension.
• TAZ Population Projections. These are the projected populations derived from TAZ. For years
beyond 2040, the population is extrapolated based or the projected growth from 2015 and
2040.
• 75% Future Land Use or TAZ Projections. This is an intermediate population trend that assumed
the maximum of either 75% Future Land Use based projection or TAZ projection for each year.
BC developed an Equivalent Residential Population (ERP) value that allows variations in flow
produced by different population types to be expressed as a common input for wastewater flow
estimation. The range of projected populations were converted into ERP. The conversion was
accomplished by multiplying the units of population by type times an equivalent residential per
BrownAwCaldwell
3-1

EAA for the Expansion of Mallard Creek WRF
Section 3
capita flow rate. Per Charlotte Water's Hydraulic Modeling Standards, the population classifications
were assigned a per capita flow rate shown in Table 3-1. The conversion was accomplished by
multiplying the units of population by type times a typical equivalent residential per capita flow rate,
shown in Table 2.
Populaton Type
uommerciai
Institutional
Industrial (non-pmcess)
7ypleal Per Capita Wastewater
Unit Flow Rates, GPCD
60
35
25
45
The resulting population projections in ERP are depicted on Figure 34,
700,000
600,000
c
° 500,000
m
a
a° 400,000
M
c
300,000
R
v
c 200,000
v
m
Cr 100,000
W
0
2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070
Future Land Use Population Projections TAZ Population Projections
Build -Out Population at Maximum Density — — 75% Future Land Use or TAZ Projections
Figure 3-1. Mallard Creek Basin Population Projection as Equivalent Residential Population (ERP)
3.2 Flow Projections
For estimating projected flows at the MCWRF—. current plant flows were extrapolated based on the
project population growth trend corresponding to "750/, Future Land Use or TAZ". This provides a
more accelerated population growth than TAZ, but less aggressive than build -out of the basin by
2070.
Brown wCaldwell s
3-2

EAAfor the Expansion of Mallard Creek WRF
Section 3
Projected average annual and maximum monthly flows were developed for MCWRF. The MCWRF
AADF was 7.6 MGD in 2015, with an estimated tributary population of 176,400 for the same year,
yielding an overall wastewater contribution of approximately 43 gallons per capita per day (GCPD).
Projected maximum month wastewater flows were calculated using a maximum month to annual
average peaking factor of 1.25, which was derived from historical plant data. Projected average
annual and maximum month flows are shown on Figure 3-2.
35
30
do OV
OW
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do
25
i+'!
OV
so do so OP
c
OP
go do
+do
0
10
OP
do
c
Q?
5
—'
o
o L
o In
N N
a in
L'n n7
o Ln o Ln o LO o
d [} In In W
O O
N N
O O
N N
O 3
N N
O O O O O G C
N N N N N N N
—Historical Influent MMF Projected Influent MMF
—Permitted MMFHistorical Influent AADF
— — • Projected Influent AADF
Figure 3-2. Historical and Projected Flows for the Mallard Creek WRF
The projected flows and planning scenarios used in the Engineering Alternatives Evaluation are
summarized in Table 3-2.
Table 3-2. Wastewater Demand and Treatment Capacity Triggers
PmJected MCWRF
Year Influent Flow (MIVIF), PlanningTrigger
IVIGD
2021
2027
2030
2040
12.0 MCWRF permitted treatment capacity
14.9 Capacity of identified MCWRF Phase 1 expansion
16.0 Capacity of identified MCWRF Phase i and 2 expansion and planning
horizon for this EngineeringAltematives Evaluation
20.0
Estimated IBT Limit
Brown"Caldwell
3-3

Sectinn 4
Alternatives Analysis
This section describes the alternatives evaluated to provide treatment of projected wastewater flows
generated within the MCWRF service area, which are summarized in Table 1. For planning purposes,
it was assumed that maximum monthly treatment demand of 16 MGD would be reached within the
MCWRF service area by 2030.
Alternative 1 No Action Alternative
Alternative 2 Expand MCWRF and Mallard Creek surface water_ discharge by 4 MGD (selected alternative)
Alternative 3 Purchase 4 MGD of additional capacity from WSACC and convey wastewater from Mallard Creek
WRF to RRRWWrP through the Fuda Creek Interceptor
Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of additional capacity from WSACC and
Alternative 4a convey all Back Creek Flow to WSACC's RRRWWTP through the Fuda Creek Interceptor
Altemattve 4b Partially expand MCWRF by 2.9 MGD. Purchase 1.1 MGD of additional capacity from WSACC and
convey all Back Creek Flaw to WSACC's RRRWWTP through a Now Back Creek Parallel Sewer
Alternative 5 Convey 4 MGD of wastewater from the Mallard Creek Basin to CLTWatees McDowell Creek WRF
Alternative G Expand MCWRF and land apply 4 MGD of treated effluent
Alternative 7 Expand MCWRFand reuse 4 MGD of treated effluent
A planning level scope of work was developed for each alternative that identifies infrastructure
improvements needed to meet wastewater conveyance and treatment demands. Capital costs were
developed for each alternative, as applicable. The total capital cost was determined by applying
percentages to the direct construction cost as shown in Table 4-2.
Incremental Construction Cost Item incremental Coat FaclorAppiied to Cumulative
Construction Cost
Direct Construction Cost 100%
Sales Tax
General Conditions, 0/H, Profit
Bonding & Insurance
Contingency
Escalated Construction Cost
Engineering for Design
Engineer's Construction Services
7.25%
12%
3.50%
30%
Assumed 3 percent escalation rate peryear.
Escalation factors were calculated for each
alternative to mid -point of construction
10%
8%
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EAA for the Expansion of Mallard Creek WRF
Section 4
Each of the Alternatives 2 through 7 require improvements to the existing Mallard Creek Basin trunk
sewer to convey projected future flows to the MCWRF. Because improvements to the trunk line are
common to all alternatives they were excluded from the cost estimates for comparative purposes.
4.1 Alternative 1- No Action Alternative
This alternative assumes that no action will be taken Lo provide expanded treatment capacity for
wastewater generated within the Mallard Creek Sewer basin. MCWRF would continue to operate at
its current permitted capacity of 12 MGD. Improvements to the MCWRF would be focused on
rehabilitation or replacement in kind.
Projected wastewater demand in the Mallard Creek Basin exceeds 12 MGD around 2021. Growth in
the sewer subcatchments that are tributary to one of the eight WSACC conveyance points, can be
managed up to the existing allocation of 6 MGD. This flow transfer currently averages 3.6 MGD, with
2.4 MGD remaining flow allocation. The conveyance of flow to WSACC through the existing
infrastructure will primarily address flows in the Back and Clark Creek sewer basins on the east side
of the MCWRF service area.
The most significant growth in the Mallard Creek Basin is anticipated along the Blue Line Extension
of the light rail in the University City area. Existing treatment capacity at MCWRF will not support this
growth, and the significant development areas do not have existing access to the WSACC
conveyance and treatment systems. This will significantly affect growth as limited new connections
would be allowed to the Mallard Basin collection and treatment system if no action were taken to
expand capacity.
Based on input from Charlotte Planning Department and UNCC. the most significant growth in
Mallard Creek Basin is expected within the University City Area, University Research Park and along
the Blue Line Extension of the light rail. Growth from these areas will exceed the MCWRF capacity
and the majority of these areas are not served by existing conveyance infrastructure to WSACC.
When flows to MCWRF reach 12 MGD, new development will be restricted, or will require an onsite
septic system or package wastewater treatment plant. Historically, private systems are not properly
maintained and have a higher risk of failure than publicly -owned treatment systems. Public utilities
often step in and assume ownership and operation of SLIch systems.
The No Action Alternative will not meet wastewater treatment demands beyond 2021. This will
result in a moratorium on new sewer connections in the MCWRF service area, with new development
requiring on site private wastewater treatment. Significant investments have been made to the
Mallard Creek Basin to support growth including the Blue Line Extension of the light rail, and by
UNCC and private developers. Failure to provide wastewater service to support this planned growth
would have significant economic and policy consequences. Provision of private onsite treatment
systems is not sustainable. As such, this alternative has a fatal flaw and did not receive further
consideration.
4.2 Alternative 2 - Expand MCWRF and Mallard Creek Surface
Water Discharge to 16 MGD
This alternative includes expansion of MCWRF by 4 MGD to 16 MGD MMF. The required MCWRF
improvements wouid be limited to the existing plant property. Speculative limits for a 16 MGD
effluent discharge to Mallard Creek are presented in Section 2. Improvements to the MCWRF
identified to treat 16 MGD and meet the speculative limits include:
1. Construct anew Influent Pump Station (IPS) with new screens to connect to the future relief
sewer
Brown AwCaldwell
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EAA for the Expans+on of Mallard Creek W tiF
2. Construct a new offline flow equalization (EQ) basin
3. Construct a new Primary Ciarifier 6
Section 4
4. upgrade the existing blowers and associated electrical gear, replace the existing leaking
underground air piping with new above ground stainless steel piping to Supply air to the existing
Biological Treatment Trains 1 and 2
5. Construct a new blower building and install new blowers to supply air to the existing Biological
Treatment Train 3
6. Modify the diffuser grids in Biological Treatment Train 3 to improve dissolved oxygen control and
distribution
7. Implement advanced aeration control strategies in the activated sludge process
8. Construct anew Final Clarifier 4
9. Construct additional alkalinity storage and feed facilities
10. Perform yard piping improvements.
These improvements are depicted on an aerial view of the site on Figure 4-1.
Figure 4-L Alternative 2, Aerial View of Proposed Expansion at MCWRF
Brown Aw Catdwett
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FAA for the Expansion of Mallard Creek WRF
Section 4
This alternative was assumed to be constructed in two phases. Phase 1 improvements will increase
treatment capacity at MCWRF to 14.9 MGD and can be constructed by 2023. Phase 2
improvements will provide another 1.1 MGD of capacity to a total MCWRF treatment capacity of 16
MGD MMF. The scope and cost for each phase is summarized in Table 4-3. Construction costs have
been escalated to midpoint of construction using a 3 percent escalation rate per year. Other
assumptions and markups are outlined in Table 4-2.
Table 4-3. Alternative 2 Capital Cost Summary
Description
EstimeW Cost
Phase i MCWRF Expansion to 14.9 MGD
Train 3 Diffusers
$200,000
New Screens, Channels, Flumes
$5,170,000
New IPS
$14,010,000
EQ Basin
$2,670,000
New Blowers & Blower Bldg.
$2,380,000
Alkalinity Facilities
$800,000
Misc. Improvements
$3,000,000
Direct Construction Costs
$28,230,000
Subtotal Including Sales Tax, General Conditions, 0/H, Profit,
Bonding & Insurance, Contingency
$45,290,000
(Refer to Table 4-2)
Assumed Constriction Perind (Years)
2020-2023
Escalated Construction Cost,12.96%
$51,160,000
Engineering for Design and Construction,18%
$9,220,000
Total Estimated Capital Cost
$60,380,000
Phase 2 MCWRF Expansion to 16.0 MGD
4
Ex. Blowers, Air Pipe, Train i & 2 Diffusers
$1,850,000
Primary Clarifier #6 & Piping
$2,100,000
Final Clarifier#4 & Piping
$3,200,000
Effluent Piping Improvements
$300,000
Direct Construction Costs
$7,450.000
Subtotal including Sales Tax, General Conditions, 0/H, Profit,
Bonding & Insurance, Contingency
$11,970,000
(Refer to Table 4-2)
Assumed Construction Period (Years)
Escalated Construction Cost, 25.45%
Engineering for Design and Construction,18%
Total Estimated Capital Cost
Total Alternative 2, Expansion to 16 MGD
2024-2026
$15,020,000
$2,720,000
$17,740,000
$78,120,000
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44

EAAfor the Expansion of Mallard Creek WRF
Section 4
Alternative 2 provides the following benefits:
Provides adequate treatment capacity to support economic development and meet projected
2030 wastewater demand of 1.6 MGD MMF
• Phasing allows time to monitor demand and verify timing of Phase 2 expansion
• Phasing spreads funding over 8 years
• CLTWater maintains control of wastewater treatment within the Mallard Creek Basin ensuring
reliable treatment is provided
• Technically feasible alternative
• Improvements fit within existing properly boundaries and minimize land disturbance
• Treatment process improvements rninirnize water quality impacts to Mallard Creek.
4.3 Alternative 3 - Purchase 4 MGD of Additional capacity from
WSACC and Convey Wastewater from Mallard Creek WRF to
RRRWWTP through the Fuda Creek Interceptor
This alternative assumes that the City of Charlotte/CLTWater will purchase additional flow allocation
from WSACC to treat projected wastewater flows generated in the Mallard Creek Basin in excess of
the 6 MGD MCWRF permitted capacity. Alternative 3 expands on the existing agreement between
CLTWater and WSACC. This alternative assumes that at the projected 2030 MMF of 16 MGD, 4 MGD
MMF of untreated wastewater received at the MCWRF will be conveyed to WSACC's RRRWWT'P for
treatment, and the treatment capacity at MCWRF will not be expanded. This alternative assumes
that WSACC RRRWWTP has available treatment capacity to accept the 4 MGD MMF.
The existing points of connection to convey flows from the Mallard Creek Basin to the RRRWTP are
not centralized, and additional conveyance infrastructure would be needed to service anticipated
growth areas. Capital improvements identified to implement Alternative 3 include:
• Construct a new PS at the MCWRF site discharging to a new 21,000-linear-foot, 24-inch in
diameter force main that conveys flow south toward CLTWater's Back Creek Pump Station
• Coordinate conveyance improvements with WSACC to discharge flows to WSACC's Fuda Creek
Interceptor (Figure 4-2). The existing Fuda Creek interceptor has a design capacity of 6 MGD
and is currently flowing at only 10% of its design capacity.
8rownAwCaldwell s
4-5

EAA for the Expansion of Mallard Creek WRF
Mallard Creek WRF
ie New 24-inch Force
Musk Pavilion
Section 4
3 � ,
•
Hickory Ridge
High School Q
WSACC's Fuda Im
Creek Interceptor r,.s
Figure 4-2. Alternative 3, Improvements to Convey Flow from MCWRF to WSACC's Fuda Creek Interceptor
There is currently 2.4 MGD flow allocation available from the existing agreement. Under Alternative
3, CLTWater would not rely on the existing available flow allocation to meet the projected 2030
aernand of 16 MGD in the Mallard Creek Basin. Purchasing an additional 4 MGD MMF will allow the
2.4 MGD balance on the current agreement to provide a buffer to mitigate risks associated with the
uncertainty and range of growth projections, and unforeseen conditions that can affect the timing of
proposed improvements.
CLTWater paid $18 million for 3 MGD of capacity in 2001 or $6 per gallon. In 2018 dollars. the cost
of additional treatment capacity allocation was assumed to be $15 per gallon, based on current
wastewater treatment construction costs. The capacity fee that would be charged by WSACC for an
additional 4 MGD would be $60 M.
CLTWater would have to pay the capital cost for constructing the necessary conveyance
infrastructure. For a new pump station and a 21,000-LF force main. The improvements and costs
associated with Alternative 3 are summarized in Table 4-4. Other assumptions and markups are
outlined in Table 4-2.
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EAA for the Expansion of Mallard Creek WRF
Description
Conveyance from MCWRF to WSACC's Fuda Creek
IntenxptorforTreatment at RRRWWrP
Pump station (4 MMF/ 11 MGD PHF)
Force Main (240)
Trenchless Road Crossings
Estimated Cost
$6,600,000
$6,300,000
$680.000
Direct Construction Costs $13,5W,000
Subtotal including Sales Tax, General Conditions, 0/H,
Profit, Bonding & Insurance, Contingency $21,800,000
(Refer to Table 4-2)
Assumed Construction Period (Years) 2020-2022
kVI
\ (�D Engineering for Design and Construction,18% $4,380,000
�A Land Acquisition $30,000
Capacity Fee $60,000,000
Total Estimated Capital Cost S88,670,000
In addition to the capital costs, WSACC will charge annual sewer fees for service. Currently annual
fees are approximately $1.40 per 1,000 gallons. For planning purposes annual sewer fees of
$1.50/1,000 gallons were assumed. These recurring costs are accounted for in the Net Present
Value (NPV) Analysis presented in Section 5.
Section 4
Escalated Construction Cost,11.28% $24,260,000
Alternative 3 provides the following benefits:
• Provides wastewater treatment capacity of 16 MGD MMF to meet. 2030 demand
• Expansion at MCWRF is deferred beyond 20--30 and NPDES expansion permitting would not be
needed
• Existing surplus capacity at RRRWWTP is used
• New conveyance infrastructure can use the existing Back Creek force main easement for
approximately one half of the route (Figure 4-2)
• It is estimated that about 2700 linear feet of new easement is required
The risks associated with Alternative 3 include:
• There is cost uncertainty in the additional conveyance requirements associated with typical
linear project risks such as railroad, road, and stream crossings as well as community
disturbance
• There is uncertainty in the cost to procure additional treatment capacity from WSACC
• CLTWater is not in complete control of treatment for customers in the Mallard Creek service area
This alternative is technically feasible. However, due to the complexities associated with constructing
the required conveyance, expanded treatment service would not be viable by 2021 when flows are
expected to exceed the permitted flow of 12 MGD MMF at MCWRF. The inability to meet treatment
demand by 2021 was considered a fatal flaw for Alternative 3.
BrownwCaldwell
4-7

EAA for the Expansio,i of Mallard Creek WRF
Section 4
4.4 Alternative 4a - Partially Expand MCWRF by 2.9 MGD. Purchase
Ll MGD of Additional Capacity from WSACC and Convey All
Back Creek Flow to WSACC's RRRWWTP through the Fuda
Creek Interceptor
Alternative 4a assumes that approximately 1.1 MGD MMF of wastewater generated in the Back
Creek Basin than is currently pumped to MCWRF would be sent to WSACC through a new force main
discharging to WSACC's Fuda Creek Interceptor. MCWRF would also be expanded to 14.9 MGD MMF
by implementing the Phase 1 improvements outlined in Alternative 2. These two projects combined
will provide wastewater treatment for projected 2030 flows of 16 MGD MMF. Alternative 4a includes
the following components:
• Construct Phase 1 expansion of MCWRF to 14.9 MGD MMF
• Purchase an additional 1.1 MGD of treatment capacity at RRRWWTP
• Construct a 9,500-linear-foot, 20-inch diameter force main that conveys flow southeast from the
Back Creek PS to discharge in WSACC's Fuda Creek Interceptor
• Coordinate conveyance improvements with WSACC to discharge flows to WSACC's Fuda Creek
Interceptor (Figure 4-3). The existing Fuda Creek interceptor has a design capacity of 6 MGD
and is current.iy flowing at only 10% of its design capacity.
Abandon existing Back Creek Pump Station force main to MCWRRF.
Mallard
Creek WRF
Figure 4-3. Alternative 4a, New Infrastructure Conveying Back Creek Basin Flow to WSACC's Fuda Creek
Interceptor
Brown Aw Caldwell
M

EAA for the Expansion of Mallard Creek fiJRF
Section 4
As described in Alternative 3, the cost for treatment capacity from WSACC is expected to be $15 per
gallon, so purchasing 1.1 MGD of capacity will cost $16.5M. Additional capital improvements and
costs for Alternative 4s are summarized in Table 4-5.
Description
Phase 1 MCWRF Expansion to 14.9 MGD
Estimated
Cost
Train 3 Diffusers $200,000
New Screens, Channels, Flumes
$5,170,000
New IPS
$14,010,000
EQ Basin
$2,670,000
New Blowers & Mower Bldg.
$2,380,ODO
Alkalinity Facilities
$800,000
Misc. Improvements
$3,000,000
Direct Construction Costs $28,230,000
Subtotal including Sales Tax, General Conditions, O/H, Profit, Bonding & Insurance,
Contingency $45,290,000
(Refer to Table 4-2)
Assumed Construction Period (Years) 2020-2023
Escalated Construction Cost,12.96% $51,160,000
Engineering for Design and Construction,18% $9,220,000
Total Estimated Capital Cost $60,380,000
Phase 2 Transfer of 1.1 MGD to RRRWWTP (Back Creek to Fuds Creek)
Pump Station Improvements
$1,000,000
Force Main (20")
$2,380.000
Trenchless Road Crossings
$680,000
Direct Construction Costs
$4,060,000
Subtotal including Sales Tax, General Conditions, 0/H, Profit, Bonding & Insurance,
Contingency
$6,540,000
(Refer to Table 4-2)
Assumed Construction Period (Years)
2020-2022
Escalated Construction Cost,11.28%
$7,280.000
En gineeringfor Design and Construction, 18% $1,320,000
Land Acquisition $30,000
Capacity Fee $16,500,000
Total Estimated Capital Cost $25,130,000
Total Alternative 4a Both Phases $85,510,ODO
BrownAwCaldwell
4-9

EAA for the Expansion of Mallard Creek WRF
Section 4
In addition to the capital costs, WSAAC will charge annual sewer fees for service. Currently annual
fees are approximately $1.40 per 1,000 gallons. For planning purposes annual sewer fees of
$1.50/1,000 gallons were assumed. These recurring costs are accounted for in the Net Present
Value (NPV) Analysis presented in Section 5.
Alternative 4a provides the following benefits:
• Provides wastewater treatment capacity of 16 MGD MMF to meet 2030 demand
• Defers the Phase 2 MCWRF expansion of 1.1 MGD which under Alternative 2 would be
constructed by 2027
Represents a diversified, flexible option, which has a common first phase with Alternative 2
• The $16.5 M WSACC Capacity Fee cost could be deferred until the additional 1.1 MGD MMF
capacity is needed since there is currently 2.4 MGD of capacity available under CLTWater's
current contract
• Works in collaboration with WSACC's sewer development plan
The risks of this option include the following:
• Uncertain costs in modifying and upgrading the Back Creek PS, so it continues to operate
• Uncertain cost, for additional unforeseen conveyance and treatment improvements at WSACC
• There is uncertainty in the cost to procure additional treatment capacity from WSACC
• CLTWater not in complete control of wastewater service for customers in the Back Creek sewer
basin
• Linear project risks (railroad, road, and stream crossings, community disturbance)
4.5 Alternative 4b - Partially Expand MCWRF by 2.9 MGD. Purchase
1.1 MGD of Additional capacity from WSACC and Convey all
Back Creek Flow to WSACC's RRRWWTP through a New Back
Creek Parallel Sewer
Alternative 4b assumes that approximately 1.1 MGD MMF of wastewater generated in the Back
Creek Basin that is currently pumped to MCWRF would be sent to WSACC. MCWRF would also be
expanded to 14.9 MGD MMF by implementing the Phase 1 improvements outlined in Alternative 2.
These two projects combined will provide wastewater treatment for projected 2030 flows of 16 MGD
MMF. Alternative 4 includes the following components:
• Construct Phase 1 expansion of MCWRF to 14.9 MGD MMF
• Purchase an additional 1.1 MGD of treatment capacity at RRRWWTP
• Construct 20,000 LF of a new 24-inch sewer to transfer flow from the Back Creek Basin to a
existing WSACC interceptor east of the Hickory Ridge High School (Figure 4-4). The proposed 24-
inch sewer is currently in WSACC's CIP to accommodate anticipated growth along the interceptor
route. Based on this alternative the cost to construct this new 24-inch will be passed on to
CLTWater.
• Abandon existing Back Creek Pump Station force main to MCWRRF.
BrownAwCa(dwell
4-10

EAA for the Expansion of Mallard Creek WRF
Mallard Creek WRF
L9
r•
Abandon Existing Back Creek �� r
Pump Station Force Main .
Hickory R.dpee,
ih9h SOW
INew 24-inch Gravity Sewer Conveys I
from Back Creek Basin to WSACC
Section 4
Figure 4-4. Alternative 4, New Infrastructure Conveying Back Creek Basin Flow to WSACC
As described in Alternative 3, the cost for treatment capacity from WSACC is expected to be $15 per
gallon, so purchasing 1.1 MGD of capacity will cost $16.5M.
Capital improvements and costs for Alternative 4 are summarized in Table 4-6.
Description Estimated Cost
Phase 1 MCWRF Bpansion to 14 9 MGD
Train 3 Diffusers $200,000
New Screens, Channels, Flumes $5,170,000
New IPS $14,010,000
EQ Basin $2,670,000
New Blowers & Blower Bldg. $2,380,000
Alkalinity Facilities $800,000
Misc.lmprovements
$1000,000
Direct Constriction Costs
$28,230,000
Subtotal Including SalesTax, General Conditions.O/H, Profit,
Bonding & Insurance, Contingency
$45,290,000
(Refer to'Table 4-2)
Assumed Construction Period (Years)
2020-2023
Escalated Constructon Cost 12.96%
$51,160,000
BrownAwCaldwett
4.11

EAA for the Expansion cf Mallard Creek WRF
Table 4-6. Alternative 4b Capital Cost Summary
Engineering for Design and Construction,18%
Total Estimated Capital Cost
Phase 2 Transfer of 1.1 MGD to RRRWWTP (Back Creek Sewer)
$9,220,000
$60,380,000
Sewer (24") $7,000,000
Trenchless Road Crossings $680,000
Manholes $250,000
Direct Construction Costs $9,540,000
Subtotal including Sales Tax, General Conditions, 0/H, Profit,
Bonding & Insurance, Contingency $12,750,000
(Refer to Table 4-2)
Assumed Construction Period (Years)
2024-2026
Escalated Construction Cost, 25.45%
$16,000,000
Engineering for Design and Construction,18%
$2,880,000
Land Acquisition
$360,000
Capacity Fee
$16,500,000
Total Estimated Capital Cost
$35,740,000
Total Alternative 4 Both Phases
$96,150.000
Section 4
In addition to the capital costs, WSAAC will charge annual sewer fees for service. Currently annual
fees are approximately $1.40 per 1,000 gallons. For planning purposes annual sewer fees of
$1.50/1,000 gallons were assumed. These recurring costs are accounted for in the Net Present
Value (NPV) Analysis presented in Section 5.
Alternative 4b provides the following benefits:
• Provides wastewater treatment capacity of 16 MGD MMF to meet 2030 demand
• Defers the Phase 2 MCWRF expansion of 1.1 MGD which under Alternative 2 would be
constructed by 2027
• Diversified, flexible option, which has a common first phase with Alternative 2
• The $16.5 M WSACC Capacity Fee cost could be deferred until the additional 1.1 MGD MMF
capacity is needed since there is currently 2.4 MGD of capacity available under CLTWater's
current contract
• Decommissioning of Back Creek PS eliminates 0&M costs and cost of needed upgrades at that
pump station
• Works in collaboration with WSACC's sewer development plan
The risks of this option include the following:
• Uncertain costs for additional unforeseen conveyance and treatment improvements at WSACC
• There is uncertainty in the cost to procure additional treatment capacity from WSACC
• CLTWater not in complete control of wastewater service for customers in the Back Creek sewer
basin
• Linear project risks (railroad, road, and stream crossings, community disturbance)
Brown Aw Caldwell
4-12

EAA for the Expansion of Mallard Creek WRF
Section 4
4.6 Alternative 5 — Convey 4 MGD of Wastewater from the !Mallard
Creek Basin to CLTWater's McDowell Creek WRF
Alternative 5 assumes that MCWRF would remain at the current permitted capacity and wastewater
flows beyond 12 MGD would be diverted from the Mallard Creek Basin to CLTWater's McDowell
Creek WRF. The McDowell Creek WRF was expanded in 2007 to its current permitted treatment
capacity of 12 MGD and currently treats approximately 5 MGD MMF. Therefore, treatment capacity is
potentially available to accept a 4 MGD MMF transfer from the Mallard Creek Sewer Basin, assuming
very limited growth is expected in the McDowell Creek Sewer Basin. Diverting flow to McDowell Creek
WRF may provide a means to meet future wastewater treatment demand without increasing the
Inter -Basin Transfer (IBT), because the McDowell Creek WRF discharges to the Catawba River Basin
which is also the drinking water source serving the Mallard Creek Basin.
Capital improvements identified to implement Alternative 5 include:
Construction of a new 4 MGD MMF/ 11 MGD PHF Pump Station
• Construction of 50,000-1-F, 24-inch force main in the McDowell Creek Sewer Basin (Figure 4-5).
The proposed PS is shown in the middle of Figure 4-5 with the proposed force main to the
McDowell Creek Basin colored pink
Improvements in the McDowell Creek Sewer Basin
A recent condition assessment commissioned by CLTWater identified significant improvements
at McDowell Creek WRF needed to reliably treat the additional 4 MGD MMF, including
rehabilitation of the currently empty and older biological treatment trains.
CREEK
E CREEK
w, — -r m,
W40O LF N lr-W
ORM0,CREEK
all
LOWER
CL.AX)
CR&mX
RV
se
urns
N
awoLFo rr
N*d" .
�qe, C�Yk Tkanef� �
a to LF a HACK CREEK
AfALLAR PLEA
UPPER
LITTLE SUGAR.
CREEK
coo)"r
REEOYCREEK
A
Figure 4-5. Alternative 5, New Infrastructure Conveying Mallard Creek Basin Flow to McDowell Creek WRF.
BrownAwCatdwell
4-13

EAA for the Expansion of Mallard Creek WRF
The scope and associated capital costs for Alternative 5 are summarized in Table 4-7.
Cost Summary
Description
Estimated Cost
Conveyance from Mallard Creek Basin to McDowell Creek
Basin forTreatment at McDowell Creek WRF
Pump station (4 MMF/ 11 MGD PHF)
$6,600,000
Force Main (248)
$15,000,000
Trenchless Road Crossings
$1,350,000
Subtotal Direct Construction Costs
$22,950,000
Subtotal including Sales Tax, General Conditions, 0/H, Profit,
Bonding & Insurance, Contingency
$36,830,000
(Refer to Table 4-2
McDowell Basin Sewer Improvements
$3,200,000
McDowell Creek WRF upgrades
$22,000,000I
Total Estimated Construction Cost
$62,030,000
Assumed Construction Period (Yeaxs)
2020-2023
Escalated Construction Cost 12.96%
$70,070,000
EngineedngforDesign and Construction, 18%
$12,620,000
land Acquisition
$550,000
Total Estimated Capital Cost
$83,240,000
Section 4
Alternative 5 offers the following benefits:
• Deferred expansion at Mallard Creek WRF beyond 2030 and associated NPDES permitting
• Does not contribute to IBT, and can therefore provide for treatment beyond the anticipated 2040
IBT horizon at MCWRF
• Uses surplus capacity at McDowell Creek WRF
• Provides diversification in treatment
The risks of this option include the following:
• Significant property acquisition requirements
• Environmental impacts of the conveyance system improvements have not been evaluated
• 0&M costs of treatment are higher at McDowell WRF than MCWRF because McDowell Creek
WRF NPDES permit has nutrient limits
Linear project risks (railroad, road, and stream crossings, community disturbance).
Alternatives 5 is technically feasible and provides long-term benefits in terms of mitigating potential
future IBT impacts. However. due to the complexities associated with constructing the required
conveyance, expanded treatment service would not be viable by 2021 when flows are expected to
exceed the permitted flow of 12 MGD MMF at MCWRF The inability to meet treatment demand by
2021 was considered a fatal flaw for Alternative 5.
1 Personal communication with the ORC of McDowell Creek WRF
BrawnmCaldwell s
4-1a

EAA for the Expansion of Mallard Creek WRF Section 4
4.7 Alternative 6 - Expand MCWRF and Land Apply 4 MGD of
Treated Effluent
Alternative 6 assumes that wastewater flows above the 12 MGD MCWRF permitted capacity would
be treated on the MCWRF site to standards suitable for land application of the treated wastewater
and not discharged as MCWRF effluent to Mallard Creek. Land application systems can be in the
form of subsurface systems, drip irrigation or spray irrigation, and must meet the effluent limits
defined in the North Carolina Administrative Code (NCAC) 15A O2T Section 0500 which are
summarized in Table 4-8.
Parameter BODS TSS Ammonia I Fecal Coliform
Effluent Limitations 30 mg/L 30 mg/L 15.0 mg/L 200 colonies /100 mL
Some level of secondary treatment would be required to achieve the land application limits,
including carbonaceous oxidation and partial nitrification. As such, all the improvements identified
in Alterative 2 are required for Alternative 6 because the treatment plant must be expanded to be
able to treat the additional 4 MGD MMF to land application standards.
The EPA manual on Land Treatment of Municipal Wastewater Effluents (EPA 2006) lists a typical
loading rate of 1.9 to 6.5 cm (0.75 to 2.6 inches) /acre -week for land application systems. One inch
per acre per week loading rate is assumed for the purposes of this alternative. This loading rate
equals 27,150 gallons per acre per week, which corresponds to approximately 1,030 acres of land
for 4 MGD of spray irrigation without accounting for any buffers. A 500 foot buffer would add
approximately 350 acres for a total area of 1380 acreslt will be challenging to find suitable,
sustainable land application sites given the real estate development occurring in the region. For the
alternatives analysis it was assumed that a site is available within 5 miles from the Mallard Creek
WRF. Assume a purchase price of $20,000 per acre, the cost to acquire a land application site with
buffers was estimated at $27.6 million.
In addition to the land application site, a new effluent PS and force main as well as storage are
needed to convey the treated effluent to the land application site. The new effluent PS will be
constructed at the Mallard Creek WRF. The required effluent storage is determined by a water
balance analysis and will be based upon the most limiting factor of the hydraulic loading based on
either the most restrictive horizon or groundwater mounding analysis; or nutrient management
based on either agronomic rates for the specified cover crop or crop management. It is assumed that
a 3O-day storage (4 MGD x 30 days = 120 MG) will be required to hold the effluent for periods when
land application is not feasible due to hydraulic limitations. Assuming a 6-foot-deep pond,
approximately 70 acres are needed for the pond and its buffers. Charlotte owns 87 acres at the
Mallard Creek WRF site, 73 of which aren't in a flood plain or stream buffer. Only 38 acres are
available after removing the wooded areas, buildings and pavement. Therefore, it is infeasible to site
a 120-MG storage pond at the Mallard Creek WRF. The 3O-day storage pond would need to be
located off -site, preferably near the land application site.
The scope of improvements and associated capital costs for this alternative are summarized in Table
4-9.
Brown w Caldwell
4-15

EAA for the Expansion of Mallard Creek WRF
Table 4-9. Alternative 6 Capital Cost Summary
Desa(ptlon
Cost
Land Application of 4 MGD of Treated Effluent from MCWRF
Effluent Pump Station (4 MMF/ 8 MGD PHr)
$1,600,000
Force Main from WWIP to Sprayfield (24")
$7,920,000
Trenchless Road Crossings
$720,000
30-day offsite storage
$60,000,000
Subtotal Direct Construction Costs
$70,240,000
Subtotal Including Sales Tax, General Conditions, O/H, Profit,
Banding & Insurance, Contingency
$112,670,000
(Refer to Table 4-2
Assumed Construction Period (Years)
2021-2026
Escalated Construction Cost 19.94%
$135,140,000
Engineering for Design and Construction,18%
$24,340,000
Land Acquisition for Offsite Storage
$1,400,000
Land Acquisition for Spray Irrigation
$27,600,000
Land Acquisition for pipeline
$80,000
Alternative 2 Costs
$78,120,000
Total Estimated Capital Cost
$266,680,000
Section 4
The total capital cost for this alternative is approximately $267 million, which is higher than any
other alternative evaluated in this study so far by a factor of almost 3. Additionally, this alternative
would require the siting and acquisition of over 1,000 acres of land near the Mallard Creek WRF by
2021. Availability of such a large site is highly unlikely. Like Alternatives 3 and 5, Alternative 6 is
considered to have a fatal flaw that could prevent it from achieving the treatment objectives. Due to
the complexities associated with securing a large land application site and the overall magnitude of
the project, expanded treatment would not be viable by 2021 when flows are expected to exceed the
permitted flow of 12 MGD MMF at the Mallard Creek Sewer Basin. For these reasons. this alternative
was not considered further.
4.8 Alternative 7 - Expand MCWRF and Reuse 4 MGD of Treated
Effluent (Non -conjunctive Reuse)
Alternative 7 ass,jmes reuse of 4 MGD MMF of treated wastewater from Mallard Creek WRF as a
non -conjunctive reclaimed water in lieu of increasing the permitted effluent flows from MCWRF. A
non -conjunctive system is a system that relies on the year -:round availability of reclaimed water use
customers to accept up to 4 MGD MMF of treated effluent. In contrast, a conjunctive system has the
capacity to discharge all the generated wastewater by ,other means, typically a National Pollutant
Discharge Elimination System or non -discharge permit, if the treated wastewater does not meet
reclaimed water quality criteria or the reclaimed water users are unable to utilize the volume of
reclaimed water generated. Mallard Creek WRF has a conjunctive reuse system since it has a NPDES
permit and a non -discharge system permit for type 1 reclaimed water; which is suitable for irrigation
of golf courses, sports fields, and crops for animal feed. The MCWRF conjunctive reuse system is
currently permitted for 4 MGD and includes an off -site reuse pipeline to the Tradition Golf Club
(connection at Polk and White Road) and Mallard Creek Community Park (connection at Johnston
BrownAm Caldwell
4-16

EAA for the Expansion of Mallard Creek WRF
Section 4
Oehler Road). Off -site reuse has not occurred since 2014 due to ongoing decontamination of the
MCWRF from a third -party illegal PCB dumping event. The decontamination effort is almost
complete, and off -site reuse is expected to resume shortly. Currently, a pipeline is under construction
to convey up to 1.1 MGD of reclaimed water from MCWRF to the University of North Carolina
Charlotte (UNCC) campus. The Tradition Golf Course can receive up to 2.0 MGD, and MCWRF can
use up to 0.5 MGD on site. The current reclaimed water demand totals 3.6 MGD of overall peak
demand, which is less than the 4.0 MGD MMF required by 2030.
For this alternative to be a technically feasible solution, the existing conjunctive reuse system would
need to be converted into a non -conjunctive reuse system, and additional reclaimed water users
need to be identified. Once the pipeline to UNCC is complete, another 5.5-mile-long reuse pipeline
could be constructed to connect the termination of the UNCC pipeline to the termination of the
Traditions Golf Club pipeline to create a reclaimed water distribution loop and provide enhanced
system pressure (Figure 4-6). This loop would create opportunities to add additional reclaimed water
users, which are needed to meet the 4 MGD MMF demand.
Figure 4-6. Existing and Proposed Water Reuse (Distribution Network Originating from MCWRF
A non -conjunctive reuse system requires additional disinfection and a minimum of 30 days storage
per 15A NCAC 02U.0402(n), which equates to approximately 370 acre-feet (120 MG) of storage.
Assuming a 6-foot-deep pond, approximately 70 acres are needed for the pond and its buffers. There
is insufficient land available at the Mallard Creek WRF site to construct a 120 MG storage pond. The
30-day storage pond would need to be located off -site, preferably within or near any existing or
future reclaimed water users. The Tradition Golf Club, Mallard Creek Community Park and UNCC are
possible locations for multiple offsite storage ponds that would add up to the overall storage volume
BrownAWCaldwell
HFIF/

EAA for the Expansion of Mallard Creek WRF
Section 4
needed. A non -conjunctive reuse system also requires a 5-day side -stream detention pond (a.k.a.
reject pond) for when the turbidity exceeds 10 NTUs or the permitted pathogen levels in the
reclaimed water cannot be met. This 5-day additional storage corresponds to 20 MG of storage
volume and requires another 7 acres of land to be developed.
The Phase 1 and Phase 2 MCWRF expansion improvements, identified in Alterative 2, are also
required for Alternative 7 because the treatment plant must be expanded to produce the additional
4 MGD MMF of additional reclaimed water.
The scope of work and associated capital costs for Alternative 7 are summarized in Table 4-10.
Table 4-10. Alternative 7 Capital Cost Summary
Desalptlon
Cost
Non -conjuncture Reuse of 4 MGD of Effluent from MCWRF
5-day detention pond for reject
$15,000,000
Additional Disinfection & Effluent PS (4 MMF/ 8 MGD PHF)
.Force Main (240)
Trenchless Road Crossings
30-day offsite storage
$2,400,000
$8,910,000
$680,000
$60,000,000
Subtotal Direct Construction Costs
$86,990,000
Subtotal including Sales Tax, General Conditions, O/H, Profit.,
Bonding & Insurance, Contingency
(Refer to Table 4-2
$139,510,000
Assumed Construction Period (Years)
2021-2026
Escalated Construction Cost 19.94%
$167,330,000
Engineering for Design and Construction,18%
$30,130,000
Land Acquisition for Onsite Storage
$180,000
Land Acquisition for OffsiteStorage
$1,400,000
Land Acquisition for pipeline
$90,000
Alternative 2 Costs
$78,120,000
Total Estimated Capital Cost
$277,250,000
The total capitai cost for this alternative is approximately $277 million. This cost is in the same order
of magnitude as -Alternative 6 and higher than Alternatives 2 through 5 by a factor of almost 3. This
alternative does not have the unrealistically large land requirements of Alternative 6 but requires
identification and sign up of additional reclaimed water users who would represent a sufficient and
reliable water demand to meet the requirements of a 4 MGD MMF non -conjunctive reuse system.
Even with the addition of the proposed 5.5-mile long pipeline for the creation of a looped reclaimed
water network, it is unlikely that the necessary number of reclaimed water users will be secured.
Current and perspective users rely heavily on landscaping irrigation, which has a seasonal demand
and is incompatible with a year-round non -conjunctive reuse system. Like Alternatives 3, 5 and 6,
Alternative 7 is considered to have a fatal flaw that could prevent it from achieving the treatment
objectives. Due to the complexities associated with securing sufficient and reliable reclaimed water
users and the overall magnitude of the project, expanded treatment would not be viable by 2021.
when flows are expected to exceed the permitted flow of 12 MGD MMF in the Mallard Creek Sewer
Basin. For these reasons, this alternative was not considered further.
Brown m Caldwell
4-18

Section 5
Present Worth Analysis
Net Present Value (NPV) Analysis was performed to compare the technologically feasible wastewater
treatment alternatives. The NPV analysis; summarized in Table 5-1, includes capital and 0&M costs
recurring over a 20-year period.
Alternathre Description
1 I No Action Altemative NA NA NA Y
Expand MCWRF and Mallard Creek surface water discharge by
4 MOD (selected alternative)
i Purchase 4 MOD of additional capacity from WSACC and
3 eomrey wastewaterfrom Mallard Creek WRFto RRRWWTP
through the Fuda Creek interceptor
Partially expand MCWRF by 2.9 MOD. Purchase 1.1 MOD of
4a additional capacity from WSACC and convey all Back Creek
Flow (.1.1 MOD) to WSACC's RRRWwfP through the Fuda reek,
Interceptor
Partially expand MCWRF by 2.9 MGD, Purchase 1.1 MOD of
4b additional capacity from WSACC and convey all Back Creek
Flow (1.1 MOD) to WSACC's RRRWWFP through a New Back
Creek Parallel Sewer
$78,120.000
$16,700,000
$(94,960,000) N
$88,670.,000
$28,390,000
$(123,500,000) Y
$85,510,000
$19,915,000
$(107,590,000) N
$96,150,000
$18,996,000
$(115,540,000) N
5 I Convey 4 MOD of wastewater from the Mallard Creek Basin to , $83,240,000 $24,215,000 $(110,260,000) Y
CUINater s McDowell Creek WRF
6 Expand MCWRF and land apply 4 MOD of treated effluent $266,680,000 $20,040.000 $(275,320,000) Y
7 Expand MCWRF and reuse 4 MOD of treated effluent. $277,250,000 { $16,700,000 $(278,790,000) I Y
NA: The No Action Altemative was not considered to be technically feasible and no NPV was calculated.
Capital costs were developed based on the following assumptions:
• Capital costs include cost for land acquisition, equipment, labor, installation, engineering design
cost and construction assistance
• A construction cost contingency of 30 percent was assumed
• The month of analysis was December 2017 and construction costs were escalated to the mid-
point of construction by using a 3 percent annual escalation rate
• Costs for land acquisition and capacity fees to WSACC were not escalated beyond 2018, as
applicable to each alternative.
0&M costs include power, chemicals, personnel, laboratory; maintenance, contract/skilled services,
parts & supplies, minor capital improvements, other departments, equipment/vehicles,
office/training/safety, natural gas, oil/gas, biosolids disposal, and insurance. 0&M costs were
developed using the following assumptions:
Brown,+► Caldwell

EAA for the Expansion of Mallard Creek WRF
Section 5
• MCWRF 0&M costs were derived from actual plant 0&M costs for the fiscal years 2016 and
2017 and assumed equal to $1.00/1,000 gallons per day treated
• McDowell Creels WRF 0&M costs were assumed equal to $1.25/1,000 gallons per day because
of stricter efflluent limitations pursuant to nutrient removal
• 0&M cost of a transfer pump station was assumed equal to $0.2/1,000 gallons per day
• Revenue from reclaimed water sales was assumed equal to $0.2/ 1000 gallons per day for
Alternative 7., which is approximately one half the cost of irrigation water for certain CLTWater
customers
• WSAAC will charge annual sewer fees for service under Alternatives 3 and 4. For planning
purposes annual sewer fees of $1.50/1,000 gallons were assumed.
The NPV analysis was developed based on the following assumptions:
• The year of analysis is 2018
• All construction. engineering and 0&M costs were escalated using a 2 percent annual escalation
rate and a 0..2 percent discount rate'
• Costs for land acquisition were not escalated beyond 2018, as applicable to each alternative.
' These are the current rates for use in benefit -cost and other types of economic analysis with a 20-year horizon according
to the White House's Office of Management and Budget httosi//www.whitehouse.gaVm on nUuoloads/20l7/l i/M-
18-09-revised.ndf.
Brown-wCaldwell s

Section 6
Conclusions
Alternative 2 presents the lowest capital and operation and maintenance (0&M) costs, and most
favorable net present value (NPV) compared to Alternatives 3 through 7. Alternative 2 includes a
two -phased expansion of MCWRF to 16 MGD MMF, with continued surface water discharge through
an expanded NPDES permit. Required improvements to MCWRF can be constructed on the existing
site, with minimal land disturbance or environmental impact as compared to other alternatives.
Alternative 2 requires NPDES permitting for MCWRF. Increasing the direct surface water discharge
to Mallard Creek will impact the IBT; but flows are not projected to reach the IBT limit within a 20-
year planning horizon. Alternative .2 is the selected alternative to meet the projected wastewater
treatment demand within the Mallard Creek Sewer Basin through 2030.
Alternative 1, the No -Action Alternative, is not an environmentally sound or sustainable solutior ana
has not been evaluated regarding its economics. However, failure to provide wastewater
infrastructure to support economic development in the Mallard Creek Basin would have significant
economic impacts in the region. This alternative has this fatal flaw.
Alternative 3 includes conveyance of wastewater flows within the Mallard Creek Basin to MCWRF
and subsequent transfer of 4 MGD MMF to WSACC's RRRWWTP for treatment. No expansion of the
MCWRF is assumed. Alternative 3 is technically feasible. However, costs are higher than Alternative
2 and there is more risk associated with costs for construction of additional conveyance, availability
of treatment capacity at WSACC RRRWTP, and other typical risks a linear project (i.e., railroad, road,
and stream crossings, community disturbance). The required projects under Alternative 3 could not
be constructed by 2021 as needed to achieve the projected 16 MGD MMF demand treatment
objectives, which is a fatal flaw. Alternative 3 was not selected because due to the complexities of
constructing the required conveyance expanded treatment would not be viable by 2021, when flows
are expected to exceed the permitted flow of 12 MGD MMF at the Mallard Creek WRF.
Alternative 4 (a and b) includes a Phase 1 expansion of MCWRF to 14.9 MGD MMF combined with
transfer of 1.1 MGD of wastewater generated in the Back Creek Basin to WSACC's RRRWTP. This
alternative provides treatment flexibility; however, the overall capital cost and 20-year NPV for this
alternative is still higher than Alternative 2. Risks of Alternative 4 include uncertainty in the available
treatment capacity at RRRWTP, and typical risks of a linear project (i.e., railroad, road, and stream
crossings, community disturbance).
Alternatives 3 and 4 both involve leveraging treatment capacity at WSACC's RRRWTP. Given the
uncertainty and range of potential growth scenarios in the Mallard Creek Basin, it is important for
CLTWater to explore flexible treatment options and continue the partnership with WSACC.
Alternative 5 includes transferring 4 MGD of wastewater to CLTWater's McDowell Creek WRF for
treatment. This is a technically feasible solution that provides the benefit of meeting 2030
treatment demand without IBT impacts. Alternative 5 has seven percent higher capital costs than
Alternative 2. However, because of the length of the proposed force main, significant property
acquisition is required. There are also schedule and costs risks of constructing the conveyance
infrastructure (i.e., railroad, road, and stream crossings, community disturbance). Due to the
complexities associated with constructing the required conveyance, expanded treatment would not
be viable by 2021 when flows are expected to exceed the permitted flow of 12 MGD MMF at the
Mallard Creek Sewer Basin, which is a fatal flaw for meeting 2030 treatment objectives.
Brown wCaldwell s
6-1

EAA for the Expansion of Mallard Creek WRF Section 6
Alternative 6 includes expanding MCWRF treatment capacity to 16 MGD and land applying 4 MGD of
treated effluent at a new land application site. Although Alternative 6 meets 2030 treatment
objectives without IBT impacts, the costs are over $180 M more than Alternative 2. The alternative
relies on securing a large land application site (over 1,000 acres) near MCWRF, which is not feasible
and considered to be a fatal flaw. Additionally, due to the overall magnitude of the project, expanded
effluent disposal would not be viable by 2021 when flows are expected to exceed the permitted flow
of 12 MGD MMF at the Mallard Creek Sewer Basin. This is another fatal flaw for this alternative.
Alternative 7 includes expanding MCWRF to 16 MGD MMF and reusing 4 MGD of treated effluent
through a non -conjunctive reclaimed water system. This alternative is technically feasible and
provides the benefit of having no IBT impact. However. costs for Alternative 7 are nearly $200M
greater than Alternative 2, excluding Alternative 7 from further consideration. Furthermore,
sufficient and reiiabie reclaimed water users have not been identified to utilize 4 MGD MMF. These
are considered fatal flaws forthis alternative.
BrownAmCaldwell
6-2

Section 7
Limitations
This document was prepared solely for CLTWater in accordance with professional standards at the
time the services were performed and in accordance with the contract between CLTWater and Brown
and Caldwell dated July 24, 2017. This document is governed by the specific scope of work
authorized by CLTWater; it is not intended to be relied upon by any other party except for regulatory
authorities contemplated by the scope of work. We have relied on information or instructions
provided by CLTWater and other parties and, unless otherwise expressly indicated, have made no
independent investigation as to the validity, completeness, or accuracy of such information.
Brown Caldwell
7-1

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Jaquehne Jarrell, P.E.
Operations Chief
City of Charlotte
5100 Brookshire Blvd.
Charlotte, North Carolina 28216
Dear Ms. Jarrell:
NORTH CAROLINA
Environmental Quality
February 22, 2019
Subject:
Speculative Effluent Limits
Mallard Creek WRF
Permit No. NCO030210
Mecklenburg County
Yadkin River Basin
This letter provides speculative effluent limits for 14.9 MGD and 16 MGD at the Mallard Creek
WRF. Please recognize that speculative limits may change based on future water quality
initiatives, and it is highly recommended that the applicant verify the speculative limits with the
Divisions NPDES Unit prior to any engineering design work.
Receiving Stream. Mallard Creek is located within the Yadkin River Basin. Mallard Creek
has a stream classification of C, and waters with this classification have a best usage for
aquatic life propagation and maintenance of biological integrity, wildlife, secondary
recreation and agriculture. Mallard Creek has a summer 7Q10 flow of 0.35 cfs. Updated
winter 7Q10 and average flows were not provided at this time.
Mallard Creek is currently listed as an impaired waterbody on the 2016 North Carolina 303(d)
Impaired Waters List for copper. There are no specific permitting strategies for Mallard Creek
in the Yadkin River Basinwide Water Quality Plan. Mallard Creek ultimately drains into the
Rocky River which is impaired for copper and turbidity on the same Impaired Waters List.
Based upon a review of information available from the North Carolina Natural Heritage
Program Online Map Viewer, there are no Federally Listed threatened or endangered aquatic
species identified within a 5 mile radius of the proposed discharge location. If there are any
identified threatened/endangered species, it is recommended that the applicant discuss the
proposed project with the US Fish and Wildlife Service to determine whether the proposed
discharge location might impact such species.
North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
ten,
"ate q-w r 919.707.9000

Speculative Effluent Limits. Based on Division review of receiving stream conditions and
water quality modeling results, speculative limits for the proposed expansion to 14.9 MGD
and 16 MGD are presented in Table 1. A complete evaluation of these limits and monitoring
requirements for metals and other toxicants, as well as potential instream monitoring
requirements, will be addressed upon receipt of a formal NPDES permit application. Some
features of the speculative limit development include the following:
BOD/NH3 Limits. These limits are based on a 2018 QUAL2K model, if the model is
found to be in error in design, then these speculative limits will be rescinded. Updated
winter 7Q10 flows were not provided in the model report. To apply the winter CBOD
and ammonia limits in Table 1, the model will need to be updated with current winter
flows from USGS and winter temperatures, otherwise summer limits will apply year-
round. By rule 15A NCAC 02B .0404, winter limits cannot be more than twice the
summer seasonal limits.
TABLE 1. Speculative Limits for City of Charlotte Mallard Creek WRF (Proposed
Expansion to 14.9 & 16 MGD)
Effluent Characteristic
Effluent
Limitations
Monthly
Average
Weekly
Average
Daily
Maximum
Flow
14.9/ 16.0 MGD
CBOD5 (Apr. 1-Oct.31
4.2 m/ L
6.3 m/ L
CBOD5 Nov. 1-Mar. 31 1
8.3 m . / L
12.5 m / L
NH3 as N (Apr. 1-Oct.31
1.0 m /L
3.0 m /L
NH3 as N (Nov. 1-Mar. 31 1
2.0 m /L
6.0 m /L
Dissolved Oxygen
minimum
6.0 mg/ L
TSS
30 m / L
45 m / L
TRC2
17 u 1
Fecal coliform (geometric
mean
200/100 ml
400/100 ml
Chronic Toxicity Pass/Fail
Quarterlv test)
90%
1. Tentative limits after model verifies these limits at updated winter 7Q10 flow and
temperatures.
2. Only applies when the facility uses chlorine for disinfection.
En&eer'n_g Alternatives Analysis (EAA). Please note that the Division cannot guarantee that
an NPDES permit for a new or expanding discharge will be issued with these speculative
limits. Final decisions can only be made after the Division receives and evaluates a formal
permit application for the new/expanded discharge. In accordance with North Carolina
Administrative Code 15A NCAC 2H.0105( c), the most environmentally sound alternative
should be selected from all reasonably cost effective options. Therefore, as a component of
all NPDES permit applications for new or expanding flow, a detailed engineering alternatives
analysis (EAA) must be prepared. The EAA must justify requested flows and provide an

analysis of potential wastewater treatment alternatives. A copy of the Division guidance for
preparing EAA documents is attached.
State Environmental Policy Act (SEPA) EA/EIS Requirements. A SEPA EA/EIS document
may be required for projects that: 1) involve $10 Million or more of state funds; or 2) will
significantly and permanently impact 10 or more acres of public lands. Please check with the
DWR SEPA coordinator (David Wainwright, 919-807-6442) as to whether your project
requires SEPA review. For projects that are subject to SEPA, the EAA requirements discussed
above will need to be folded into the SEPA document. Additionally, if subject to SEPA, the
NPDES Unit will not accept an NPDES permit application for a new/ discharge
until the Division has approved the SEPA document and sent a Finding of No Significant
Impact (FONSI) to the State Clearinghouse for review and comment.
Updated winter 7Q10 and average flows from the USGS will also need to be provided
before the application can be processed.
Should you have any questions about these speculative limits or NPDES permitting
requirements, please feel free to contact David Hill at [phone] or Julie Grzyb at (919)
707-3605.
Respectfully,
she Grzyb
upervisor, NPDES Complex Permitting Unit
Attachment: EAA Guidance Document
Hardcopy:
Central Files
NPDES Permit File
Electronic Copy:
NC WRC, Inland Fisheries, shannon.deaton®ncwildlife.org
US Fish and Wildlife Service, Sarah_mcrae®fws.gov
DWR/Mooresville Regional Office/Water Quality Regional Operations
DWR/SEPA, David Wainwright
DWR/Modeling, Pam Behm
DWR/Basinwide Planning, Ian McMillan
DWR/NPDES Server>Specs

From: Behm. Pamela
To: Coco, Nick A; Hill. David A; Banihani, Cals
Cc: Grzvb. Julie; Hong. Bonaahi
Subject: FW: [External] Revised Mallard Winter Model
Date: Tuesday, August 6, 2019 1:52:31 PM
Attachments: Mallard Creek TM -Winter 23 July 2019.odf
Hi Nick,
We have reviewed the revised modeling files for the winter condition analysis for Mallard Creek
WWTP. Compared to the earlier version (May 2019), changes occurred in three places:
- effluent CBOD concentrations, correctly set at winter limits (instead of summer limits)
- effluent temperature, now based on the DMR data (average March values used)
- Mooresville WWTP DO concentration, from 5 mg/L to 6 mg/L
Details of these changes can be found in below email and the revised report, consistent with the
modeling files. The typos in Table 3-2 of the report are also fixed. DWR now has final versions of the
Mallard Creek model simulating both the summer and winter conditions.
The primary conclusion of the analysis is that the facility's existing winter concentration limits for
CBOD5 and ammonia would be fully protective of DO in Mallard Creek and the Rocky River under
higher discharge rates.
Please let us know if you have any other questions.
Thanks,
Pam
From: Clifton Bell <[e-mail]>
Sent: Friday, July 26, 2019 8:41 AM
To: Behm, Pamela <[e-mail]>
Cc: Grzyb, Julie <[e-mail]>; Deaton, Shannon L. <[e-mail]>;
[e-mail]; Mcmillan, Ian <[e-mail]>; Wainwright, David
<[e-mail]>; Basinger, Corey <[e-mail]>; Pitner, Andrew
<[e-mail]>; Okioga, Irene <[e-mail]>; Jarrell, Jackie
([e-mail]) <[e-mail]>; Coco, Nick A <[e-mail]>;
Banihani, Qais <[e-mail]>; George Anipsitakis <[e-mail]>; Hill,
David A <[e-mail]>
Subject: [External] Revised Mallard Winter Model
Pam,
Good morning. The revised technical memo on the Mallard Creek winter model is attached.

Responses to DWR comments are provided below. The model files are too large to attach but are in
this OneDrive directory. Please let me know if you or your staff have any trouble accessing them, or
if you have any other questions on the revised model.
Thanks,
Clifton
Clifton Bell, P.E., P.G.
Brown and Caldwell
CBellftrwncald.com
T 757.518.2456 1 C 757.206.9110
E31'Wn. .
CaUIVAU
1. Contrary to the report's description that "For the winter conditions model, the WWTPs
were included at their full permitted flows, maximum monthly average concentrations
of BOD/CBOD and ammonia for winter months, and minimum effluent DO
concentrations", summertime effluent BOD/CBOD concentrations were used for all
WWTPs included in the model, including the Mallard Creek WRF. There is no change in
the effluent BOD/CBOD concentrations from the simulation of summer condition. This
needs to be corrected.
Response: This correction has been made. Because the f-ratios are assumed to be some as
with the summer model, winter CBODu values were calculated from the summer CBODu values
by multiplying the summer CBODu values by the ratio of summer to winter CBOD5/BOD5 (as
appropriate) permit limits for each WWTP. The CBODu values that were used in the summer
and winter model are listed in Table 3-2 of the technical memo.
2. Although minimum effluent DO concentration for the Mooresville WWTP (6 mg/L) is
correctly provided in Table 3-2 of the report, 5 mg/L was used in the modeling files for
the evaluation of winter condition.
Response: The value was changed to 6 mg/L in the model.
3. Effluent temperature for the Mallard Creek WRF is based on average March values from
the available effluent monitoring data (Table 3-4). A similar procedure should be applied
to estimate the effluent temperatures of four remaining WWTPs included in the model,
rather than using the receiving water temperature.
Response: Effluent temperature data (2009-2019) for the remaining four WWTPs were
provided by DWR. The average temperatures for the month of March were utilized in the
model. Those values are tabulated in the table below.

WWTP
Permit Number
Average Effluent Temp (*Q
Monroe WWrP
NCO024333
16.46
Rocky River Regional WWrP
NCO036269
16.84
Rocky River WWTP
NCO046728
15.03
Muddy Creek WWrP
NCO081621
13.45
4. Table 3-2 has two typos: NPDES Permit Number for the Muddy Creek WWTP is
NC0081621, not NC0024333. Also, flow limit for the Muddy Creek WWTP is 0.3 MGD,
not 0.2 MGD. (Same typos found in the summertime report.)
Response: The typos were corrected in both reports.

Brown A .
Caldwell
301 Bendix Road, Suite 400
Virginia Beach, VA 23452-1385
T: 757.518.2400
F: 757.518.2401
Technical Memorandum
Prepared for: Charlotte Water
Project Title: Permitting for the Expansion of Mallard Creek WRF
Project No.: 151553
Technical Memorandum No. 5
Subject: Mallard Creek Water Quality Modeling - Winter Condition
Date: July 23, 2019
To: Irene (Tesha) Okioga, Project Manager, Charlotte Water
From: George Anipsitakis, Brown and Caldwell
Copy to:
WA
Prepared by:
Clifton F. Bell, PE, PG
Reviewed by:
Douglas J. Durbin, PhD
Limitations:
This document was prepared solely for CLT Water in accordance with professional standards at the time the services were performed and in
accordance with the contract between CLT Water and Brown and Caldwell dated July 24, 2017. This document is governed by the specific scope of
work authorized by CLT Water; it is not intended to be relied upon by any other party except for regulatory authorities contemplated by the scope of
work. We have relied on information or instructions provided by CLT Water and other parties and, unless otherwise expressly indicated, have made
no independent investigation as to the validity, completeness, or accuracy of such information.

Mallard Creek Water Quality Modeling - Winter Condition
Table of Contents
List of Figures ..............................
Listof Tables................................................................. ................. iii
......................................................................
Section 1: Executive Summary .................................... 4
.............................................................................
Section 2: Background ............................... 5
......................................................................................................
Section 3: Representation of Winter Conditions in QUAL2K .................. 5
...........................................................
3.1 7Q1O Streamflow Values ................................................................ 6
......................................................
3.2 Permitted Effluent Limits ............................................... ....... 6
.....................................................
3.3 Average Air Temperature and Cloud Cover .................. 7
....................................
3.4 Dissolved Oxygen Concentrations and Water Temperature ................
Section 4: Sensitivity Analysis .......................................
4.1 Mallard Creek..............................................................10
...............................................................................
4.2 Rocky River........................................................................................ ..........15
...............................................
Section 5: Summary and Conclusions ..................................... 19
............................................................
References................................................................................................................................................... ........... 20
List of Figures
Figure 4-1: Scenario 1: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) at Three Outfall Discharge Rates with Best Available Estimates of CBOD
Decay and Nitrification Rates...............................................................12
............................................
Figure 4-2: Scenario 2: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate..............13
Figure 4-3: Scenario 3: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) Creek with Nitrification Rate 50 Percent Above Best Available Estimate....14
Figure 4-4: Scenario 4: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) with CBOD Decay and Nitrification Rate 50 Percent Above Best Available
Estimate................................................................................................................................ ............................15
Figure 4-5: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with Best Available Estimates of CBOD Decay and Nitrification Rates.................16
Figure 4-6: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate ......................16
Figure 4-7: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with Nitrification Rate 50 Percent Above Best Available Estimate ........................17
Figure 4-8: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with CBOD Decay and Nitrification Rates 50 Percent Above Best Available
Estimate.....................................................................................................................................................18
Brown AND Caldwell
it
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Mallard Creek Water Quality Model - Winter Condition
List of Tables
Table 2-1. Existing Effluent Limitations and Monitoring Requirements Mallard Creek Water Reclamation
Facility, Outfall 001............................................................................................................................................5
Table 3-1. Winter 7Q10 Streamflows from Weaver(2015)................................................................................... 6
Table 3-2. WWTP Effluent Limits and Associated Model Inputs............................................................................ 7
Table 4-1. Summary of Model Scenarios for Sensitivity Analysis........................................................................10
Table 4-2. Summary of Model Scenarios for Sensitivity Analysis........................................................................11
Brown-o Caldwell
iii
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Mallard Creek Water Quality Modeling - Winter Condition
Section 1: Executive Summary
Charlotte Water (CLTWater) is a public water and wastewater utility that serves customers within the City of
Charlotte and greater Mecklenburg County area. CLTWater owns and operates the Mallard Creek Water Rec-
lamation Facility (MCWRF) located on Mallard Creek, a tributary to the Rocky River. MCWRF is currently per-
mitted to discharge 12 million gallons per day (MGD) to Mallard Creek. In response to growth demands, CLT-
Water is planning an upgrade to the facility that would increase the total discharge to 14.9 MGD and
eventually to 16 MGD. This technical memorandum presents the methods and results of the water quality
modeling that was performed to determine whether MCWRF's existing CBOD5 and ammonia limits would be
protective of dissolved oxygen (DO) in Mallard Creek and the Rocky River during the winter condition (No-
vember through March).
The modeling approach with summer condition parameters was described in a prior technical memorandum
entitled Mallard Creek Water Quality Modeling Approach (Brown and Caldwell, 2018) that CLTWater submit-
ted to DEQ in March 2018. The same model was adapted to winter conditions as described in this technical
memorandum. This adaptation includes the use of winter 7Q10 streamflows, water temperatures, meteoro-
logical conditions, background dissolved oxygen conditions, and NPDES permit limits. Historical monitoring
data indicated that, of the winter months, March had the highest water temperatures, so March monitoring
data were used to characterize many model inputs such as dissolved oxygen and temperature of headwaters
and incremental inflows.
DO was not predicted to fall below 5.0 mg/L in any model scenario. Increased discharge rates were pre-
dicted to cause only small (-0.1 mg/L) decreases in the minimum DO in Mallard Creek, compared to the
12.0 MGD scenario. Increased discharge rates at MCWRF were also predicted to cause negligible change
(<0.05 mg/L) in DO conditions in the Rocky River itself, compared to the 12.0 MGD scenarios. Based on
these results, it was concluded that MCWRF's existing concentration limits for DO, CBOD5, and ammonia
would be protecting of water quality under increased discharge rates.
Brown,,Caldwell :
4
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Mallard Creek Water Quality Modeling - Winter Condition
Section 2: Background
CLTWater is a public water and wastewater utility that serves customers within the City of Charlotte and
greater Mecklenburg County area. CLTWater owns and operates the Mallard Creek Water Reclamation
Facility (MCWRF) located on Mallard Creek, a tributary to the Rocky River. MCWRF is currently permitted to
discharge 12 million gallons per day (MGD) to Mallard Creek. In response to growth demands, CLTWater is
planning an upgrade to the facility that would increase the total discharge to 14.9 MGD and eventually to 16
MGD.
For the expansion, CLTWater submitted a speculative limits request letter to DEQ in September 2018, and
DEQ provided speculative limits in February 2019. The summer speculative limits for dissolved oxygen (DO),
five-day carbonaceous oxygen demand (CBOD), and ammonia nitrogen partially relied upon a QUAL2K-based
modeling evaluation of DO sensitivity in Mallard Creek and the Rocky River (Brown and Caldwell, 2018). The
previous modeling analysis demonstrated that MCWRF's existing summer (April -October) limits (Table 2-1)
would be protective of DO in the receiving water. The purpose of this technical memorandum is to present
the methods and results of a similar evaluation for winter (November - March) conditions.
Parameter
Montrny Average
I weeKly Average
UGIIy NYC106V
Flow
12 MGD
NA
NA
CBOD, 5 day (Apr. 1- Oct 31)
4.2 mg/L
6.3 mg/L
NA
CBOD, 5 day (Nov. 1- Mar. 31)
8.3 mg/L
12.5 mg/L
NA
Total suspended solids
30.0 mg/L
45 mg/L
NA
NH3 as N (Apr.1- Oct 31)
1.0 mg/L
3.0 mg/L
NA
NH3 as N (Nov. 1- Mar. 31)
2.0 mg/L
6.0 mg/L
NA
Dissolved oxygen
NA
NA
6.0 mg/L
Fecal coliform (geometric mean)
200/ 100 mL
400/mL
NA
Temperature (deg. C)
Monitor and report only
Total zinc
Monitor and report only
pH
I
Between 6.0 and 9.0 s.u.
Chronic toxicity
Pass at effluent concentration of 90%
Effluent pollutant scan
Monitor and report only
Section 3: Representation of Winter Conditions in QUAL2K
This section describes how the critical winter condition was represented in QUAL2K. The modeling team
used the summer model documented by Brown and Caldwell (2018) as the starting point for the winter
model. The summer model itself was a QUAL2K-based version of a prior QUAL2E-UNCAS model developed
and documented by CH2M Hill (2001). The modeling team updated the summer QUAL2K model to represent
winter 7Q10 flows, temperatures, background DO concentrations, and point source discharges. The month
of March was used to represent air and water temperatures, because March is at the end of the winter
Brown,�-Cal�,
5
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
season and tends to have the highest temperatures of the season, and thus yields the most conservative
model outputs. The specific parameters that were altered for the winter condition are:
• 7Q10 streamflow values
• Permitted limits for wastewater treatment plants (WWTPs)
• Average air temperature and cloud cover
• DO concentrations and water temperature in headwaters and incremental inflows
Sections 3.1 through 3.4 describe the adaption of the previous QUAL2K model to represent winter
conditions. Other model characteristics, including the model segmentation and point sources, were
unchanged from the summer QUAL21K model. See Brown and Caldwell (2018) and CH2M Hill (2001) for
more background on the QUAL2K model segmentation and other model characteristics.
3A 7Q10 Streamflow Values
According to the fact sheet for MCWRF's existing NPDES permit, the facility's existing winter limits were
based on a Mallard Creek winter 7Q10 value of 2.1 cfs. The fact sheet did not cite a source or year range
upon which this value was based. For the present modeling exercise, the USGS provided an updated winter
7Q10 value of 2.2 cfs based on 1995-2011 stream gaging data, adjusted to reflect the Mallard Creek
drainage area at the point of the MCWRF discharge (J. Weaver, USGS, elec. comm., 22 Mar 2018). This
value was used in the QUAL2K model as the Mallard Creek headwater flow. USGS also provided an updated
estimate of the average annual streamflow discharge at this location (42.2 cfs).
Location I Winter 7Q10 (cfs)
Mallard Creek J 2.2
Rocky River near Norwood 1 79
The winter 7Q10 for the Rocky River at Norwood (79 cfs) was obtained from Weaver (2015) and was based
on 1930-2012 stream gaging data. Using the flows from the summer version of the QUAL2K model as a
starting point, the simulated flows into model headwaters (with the exception of Mallard Creek) and incre-
mental inflows were increased by the same proportion until the summed flows matched the 79 cfs value at
Norwood.
3.2 Permitted Effluent Limits
As documented by Brown and Caldwell (2018), the QUAL2K model includes four WWTPs in addition to the
MCWRF. WWTP flows and effluent parameters in the model were based on each facility's current NPDES
permit, which was obtained from the North Carolina Department of Environmental Quality (NCDEQ) on May
24, 2018. For the winter conditions model, the WWTPs were included at their full permitted flows (Table3-2),
maximum monthly average concentrations of BOD/CBOD and ammonia for winter months, and minimum
effluent DO concentrations. The f-ratios (e.g., ratio of CBOD-ultimate to CBOD5) were assumed to be the
same as those used in developing the summer model, and so the CBOD-ultimate inputs for the winter model
were calculated by multiplying the summer model CBOD-ultimate concentrations by the ratio of the winter
limits to the summer limits. The Mooresville WWTP has only one set of BOD5 limits that applies year-round.
Brown —Caldwell
6
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Mallard Creek Water Quality Modeling - Winter Condition
Facilities
Permit Component
Mooresville
(Rocky River)
WWT
NCO046728
Dye Creek
Mallard Creek
WRF
Concord (Rocky
Muddy Creek
River Regional) WWIP
Monroe WWfP
NCO024333
RichardsonCreek
NPDES Permit Number
NCO030210
NCO036269
NCO081621
Receiving Water
Mallard Creek
Rocky River
Rocky River
Flow (Monthly Average MGD)
5.5
24.0
0.3
10.4
12.0
BOD5 (mg/L) (April to October)
(Monthly Average)
N/A
N/A
10.0
I
7.3
15.0
BODS (mg/L) (Novemberto
March) (Monthly Average)
N/A
N/A
20.0
14.5
CBODS (mg/L) (April to Octo-
ber) (Monthly Average)
N/A
4.2
17.0
N/A
N/A
CBODS (mg/L) (Novemberto
March) (Monthly Average)
N/A
8.3
25.0 N/A
N/A
30.0
30.0
TSS (mg/L) (Monthly Average)
30.0
30.0 30.0
Summer CBODu (mg/L)
24.5
16.0
62.9 38.0
14.5
Winter CBODu (mg/L)
24.5
31.5
92.5 76.0
28.8
NH3-N (mg/L) (April to October)
(Monthly Average)
1.0
4.0 1 4.0
1.0
- -
2.0
NH3-N (mg/L) (Novemberto
March) (Monthly Average)
2.0
10.0 8.0
2.0
DO (mg/L) (as Daily Average in
Effluent)
��
z 6.0
> 6.0
__
z 6.0 z 5.0
5.0
- - -
nH
6.0-9.0
6.0-9.0
6.0-9.0 6.0-9.0
6.0-9.0
3.3 Average Air Temperature and Cloud Cover
Average air temperature for the winter condition was referenced using the weather station at Charlotte Doug-
las International Airport. Historical temperature and dew point values were averaged across all recorded val-
ues for March 2019. The average temperature was 9.84 ° C and the average dew point temperature was
0.89 ° C. Cloud cover was set to 50 percent based on historical percent cloud cover conditions for Charlotte
NC. Data was referenced from Weather Spark, which compiles historical weather data for many locations
around the world.
3.4 Dissolved Oxygen Concentrations and Water Temperature
Dissolved oxygen concentrations for incremental inflows and headwater flows were obtained from DEQ and
EPA monitoring station data downloaded from the National Water Quality Monitoring Council website
(https://www.wateraualitydat- The data were used to characterize average March DO and water
temperatures of headwaters (excluding Mallard Creek) and incremental inflows to the Rocky River as shown
in Table 3-3.
Brown -Caldwell :
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
3-3.
March DO and Water
Temperatures from
RockyTable
DEQ and EPA Stations on the
Monitoring Station
DO Concentrations
Water Temperature
Application to QUAL2K Winter Model
— _
(TV-4(oC)
21NC01WQ-Q7330000
9.72
12.42
Applied to all incremental inflows/headwaters upstream of and in-
cluding West Branch(segments 1-41
21NCCOALMONS-Q7450000
10.80
8•90
Applied to all incremental inflows/headwaters downstream of West
-- -
Branch and upstream of Mallard Creek (segments 5-10)
21NCCOALMONS-Q7600000
10.60
9.50
Applied to all incremental inflows between Mallard Creek and Cod --
I Creek (se&mmt 12)
21NCCOALMONS-Q7780000
10.30
9.90
Applied to all incremental inflows between Coddle Creek and Irish
Buffalo Creeks (segments 13-16)
21NC01WQ-Q8210000
9.97
11.11
I
Average of these values applied to all incremental inflows between
21NCO2WQ-QB210000
9.99
12.35
Coldwater and Dutch Buffalo Creeks (segment 17)
21NCCOALMONS-Q8385000
9.90
11.10
Applied to all incremental between Dutch Buffalo and Crooked
Creek (segments 18-23)
21NC01WQ-Q9120000
10.72
10.38
Applied to all incremental inflows between Crooked Creek and
—
model end (segments 24-31
As required by MCWRF's NPDES permit, CLTWater staff monitors water quality on Mallard Creek both up-
stream and downstream of the MCWRF outfall, and on the Rocky River downstream of the Mallard Creek
confluence. Mallard Creek headwater, incremental inflow, and point source temperature inputs were charac-
terized using 2009-2019 water quality monitoring data provided by CLTWater (Table 3-4). Average values for
March were used. Effluent temperature data from 2009 to 2019 for downstream of the outPalls of the four
other WWTPs along the Rocky River were provided by NC Division of Water Resources (DWR) (Table 3-4). The
average temperatures for March were used.
Brown —Caldwell
s
Mallard Creek TM -Winter 23 July 2019.doez

Mallard Creek Water Quality Modeling — Winter Condition
DO Concentrations
Water Temperature
Model Input
(mg/L)
(°C)
Basis
Average March values from 2009-2019 monitoring
Mallard Creek Headwater
10.58
10. ii
data upstream of MCWRFoutfall
Based on daily average
17.49
Temperature based on average March values from
MCWRF Effluent
permitlimit(6.Omg/L)
_
2009-2019MCWRFDMR monitoring data
DO based on average March DO concentrations from
Incremental inflows to Mallard
2009-2019 monitoring data on Mallard Creek down -
Creek downstream of MCWRF out-
9.80
8.90
stream of MCWRF outfall. Temperature setto match av-
fall
erage March temperature from upstream segment of
the Rocky River above the Mallard Creek confluence.
Based on daily average
_
16.46
Average March values from 2009-2019 DMR data
Monroe WWfP Effluent
permit limit (5.0 nil
downstream of Monroe WWIP outfall
Average March values from 2009-2019 DMR data
Concord (Rocky River Regional)
Based on daily average
16.84
downstream of Concord (Rocky River Regional) WWfP
WWfP Effluent
permit limit (6.0 mg/L)_
outfall _
Mooresville (Rocky River) WWfP
Based on daily average
15.03
Average March values from 2009-2019 DMR data
Effluent
permit limit (6.0 mg/L)
downstream of Mooresville (Rocky River) WWiP outfall
Based on daily average
13.45
Average March values from 2009 2019 DMR data
Muddy Creek WWfP Effluent
permit limit (5.0 mg/L)
downstream of Muddy Creek WWrP Effluent outfall
Section 4: Sensitivity Analysis
After the winter 7Q10 version of the QUAL21K model was developed, it was applied to determine whether DO
in the receiving water would be sensitive to changes in the MCWRF flow rate and CBOD5/ammonia loads. All
model scenarios utilized MCWRF's existing winter CBOD5 and ammonia nitrogen concentration limits. Three
different MCWRF discharge rates were examined: 12.0 MGD (existing), 14.9 MGD, and 16.0 MGD. Model
results were examined to determine if DO was predicted to fall below 5.0 mg/L in the receiving water or in
the Rocky River below the Mallard Creek confluence, or whether DO was predicted to change significantly
with MCWRF discharge rate. The CBOD5 oxidation rate and nitrification rates also were varied to determine
the sensitivity of predictions to these values (Table 4-1). The cited magnitudes of the rates listed in Table 4-1
are for 20°C. However, the rates are temperature -dependent, and so QUAL2K automatically adjusts the rates
based on the predicted water temperature of each segment. The best available value for the CBOD5
oxidation rate was derived from CBOD bottle tests performed by CLTWater in 2018, and the best available
nitrification rate was derived from the 2001 calibrated model (CH2M Hill, 2001). See Brown and Caldwell
(2018) for more information on the derivation of these rates.
BrownmCaldwell
9
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Mallard Creek Water Quality Modeling - Winter Condition
Scenario
Number Descriptior
1A
i 1B
Best rate
estimates
lc
2A
HigherCBOD
2B
oxidation rate
2C
Higher
3A
3B
nitrification rat
3C
4A
Higher CBOD
4B
oxidation +
nitrification rate
4C
4.1 Mallard Creek
MCWRF
Mallard Creek Mallard Creek
Flow
Cl30D5
Nitrification Rate
(MGD)
Oxidation Rate (day-')
(day)
12.0
0.06 0.25
14.9
0.06 0.25
I 16.0
0.06 0.25
12.0
0.09
0.25
14.9
0.D9
0.25
16.0
0.09
0.25
12.0
0.06
0.375
14.9
0.06
0.375
16.0
0.06
0.375
12.0
0.09
0.375
14.9
0.09
0.375
s
16.0
0.09 j
0.375
Table 4-2 presents the minimum predicted DO values in Mallard Creek by scenario, as well as the predicted
change in minimum DO from the 12 MGD discharge scenario. Figures 4-1 through 4-4 are the simulated
Mallard Creek DO profiles for the model scenarios categories 1 through 4, respectively. In Figures 4-1
through 4-4, location zero (0 km) represents the confluence of Mallard Creek with the Rocky River and is the
most downstream point of Mallard Creek. Each figure includes a marker where the MCWRF effluent enters
Mallard Creek.
BrownANDCaldwQ
10
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Mallard Creek Water Quality Modeling - Winter Condition
Mallard Creek
MCWRF
Scenario Description Flow
Number (MGD) Minimum
Predicted DO
(mg/L)
1A
12.0
6.62
T
iB
Best available 149
6.55
rate estimates
-
1C
16.0
6.53
2A
12.0
HigherCBOD 14.9
6.60
6.53
2B
oxidation rate -
16.0
12.0
-
6.51
2C
3A
6.60
3B
Higher 14.9
6.53
nitrification rate
6.51
3C
16.0
12.0
4A
6.58
- -
HigherCBOD
- -
4B
oxidation +
14.9
6.51
4C
nitrification rates
j ! 16.0
6.49
Change in Min.
DO from
12 MGD
Discharge
(mg/L)
-0.07
-0.10
-0.07
-0.09
-0.07
-0.09
-0.07
-0.09
Rocky River Segment Below Mallard
Creek Confluence
Change in Min.
Minimum
DO from
Predicted DO
12 MGD
(mg/L)
Discharge
W/ L)
7.19
7.21
0.02
7.22
0.02
7.19
-
7.21
0.02
7.22
0.02
7.19
-
7.21
0.02
7.22
0.02
-
0.02
0.02
7.19
7.21
7.22
The winter QUAL2K model predicted that DO in Mallard Creek would decrease downstream of the MCWRF
outfall and start to increase again prior to the confluence with the Rocky River. The location of the minimum
DO value was predicted to occur between -2.5 and 3.3 km below the outfall, with the greater distances
predicted in scenarios with higher CBOD5 oxidation and nitrification rates. Under no scenario was DO in
Mallard Creek predicted to fall below 5.0 mg/L. The predicted DO minima in Mallard Creek had a low
sensitivity to changes in the MCWRF effluent; discharges of 14.9 and 16.0 MDG were only predicted to
decrease DO -0.1 mg/L relative to a discharge rate of 12.0 MGD. DO predictions were not very sensitive to
the CBOD oxidation or nitrification rates. This suggests that the small differences in predicted DO between
MCWRF discharge rates were primarily driven by the MCWRF effluent DO concentration and/or differences in
in -stream reaeration rates, rather than oxygen demand from CBOD or ammonia in Mallard Creek.
Brown Caldwell
11
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Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
an
E
v 8.0
on
a
x
0
7.0
0
50
6.0
5.0
SA ■
■1A-12MGD
♦16-14.9MGD
■ 1C- 16 MGD
♦ Mallard Creek WRF
4.0
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0
0.5 0.0
Location (km)
Figure 4-1. Scenario 1: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) at Three Outfall Discharge Rates with Best Available Estimates of CBOD Decay and Nitrification
Rates.
Brown —Caldwell
12
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Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
to
E
8.0
to
X
0
7.0
O
V)
0
6.0
5.0
I�
a
■2A-12MGD
♦26-14.9MGD
® 2C -16 MGD
Mallard Creek WRF
4.0
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Location (km)
Figure 42: Scenario 2: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate.
Brown -- Caldwell
13
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
F
0
6.0
5.0
4.0
r
* 3A-12 MGD
t36-14.9MGD
3C - 16 MGD
♦ Mallard Creek WRF
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Location (km)
Figure 4-3: Scenario 3: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) Creek with Nitrification Rate 50 Percent Above Best Available Estimate.
BrownAw Caldwell
14
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11.0
■
■
10.0
9.0
J
bCD
C
C 8.0
O1
Op
X
O
v
7.0
0
0
6.0
5.0
4.0
5.0
4.5
4.0
! 9
3.5 3.0 2.5 2.0
Location (km)
■4A-12MGD
®4B-14.9MGD
•4C-16MGD
• Mallard Creek WRF
R M 0 a ■ s
1.5 1.0 0.5 0.0
Figure 4-4: Scenario 4: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) with CBOD Decay and Nitrification Rate 50 Percent Above Best Available Estimate.
4.2 Rocky River
Table 4-2 presents the minimum predicted DO values in the Rocky River segment below the Mallard Creek
confluence by scenario, as well as the predicted change in minimum DO from the 12 MGD discharge
scenario. Figures 4-5 through 4-8 illustrate the simulated Rocky River DO profiles for the model scenarios
categories 1 through 4, respectively. In Figures 4-5 through 4-8, location zero (0 km) represents the
downstream -most portion of the model domain. Each figure includes a marker where Mallard Creek enters
the Rocky River. The major discontinuities in the DO profiles are caused by the entry of tributary flows with
different DO than the Rocky River.
Under the existing permitted condition scenario 1A, the confluence of Mallard Creek and the Rocky River is
located at a point where the Rocky River is recovering from an upstream DO sag (Figure 4-5), which is itself
caused by inputs from West Branch, Mooresville (Rocky River) WWTP, and Clarke Creek. This upstream DO
sag could be significantly overestimated due to the overestimation of the CBOD decay rates in upstream
model segments, as discussed in previous sections and by CH2M Hill (2001).
As shown in Table 4-2, increased discharge rates from MCWRF were predicted to cause only very small
changes in the minimum DO in the Rocky River below the Mallard Creek confluence.
BrownANDCaldwell If
15
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11
■
10 ■
• �r
R
9 w
m
E
c 8
4) q
on
a
x
O •
v
-a 7
0
C) 6
5
1A- 12 MGD
113- 14.9 MGD
• 1C - 16 MGD
A Mallard Creek
Confluence
4
120 100 80 60 40 20 0
Location (km)
Figure 4-5: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with Best Available Estimates of CBOD Decay and Nitrification Rates.
11
■
10 ■
■
■
a 9 •
Sao �
E
c 8
v
40
O
v 7
0
N
Z
51
2A - 12 MGD
26 - 14.9 MGD
• 2C - 16 MGD
♦ Mallard Creek
Confluence
4
120 100 80 60 40 20 0
Location (km)
Figure 4-6: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate.
Brown —Caldwell
16
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11
5
4
120
■ 3A - 12 MGD
• 313 - 14.9 MGD
• 3C - 16 MGD
• Mallard Creek
Confluence
100 80
60 40 20 0
Location (km)
Figure 4-7: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with Nitrification Rate 50 Percent Above Best Available Estimate.
Brown Allff, Caldwell
17
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11
■
10 ■
■
■
? 9 •
ono ■
E ■
c 8
°1 • ■4A-12MGD
x
O ■
v 7
v
0
N ■
N
0 6
5
4
120
4B - 14.9 MGD
• 4C- 16 MGD
♦ Mallard Creek
Confluence
0%/
100 80 60 40 20 0
Location (km)
Figure 4-8: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with CBOD Decay and Nitrification Rates 50 Percent Above Best Available Estimate.
Brown —Caldwell :
18
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
Section 5: Summary and Conclusions
The modeling exercise presented here was not a full-scale recalibration of previous models but rather was a
sensitivity -based exercise of whether MCWRF's existing permit limits would be protective of DO under higher
effluent discharge rates (14.9 and 16.0 MGD). The primary basis for evaluation was whether the updated
model predicts that higher discharge rates (14.9 and 16.0 MGD) would cause significant decreases in DO in
Mallard Creek and the Rocky River, relative to the 12.0 MGD model scenarios. The updated model relied
upon recent CBOD bottle tests to improve estimates of the local CBOD oxidation rate. Higher CBOD and
nitrification rates were also explored as part of the sensitivity analysis. DO was not predicted to fall below 5.0
mg/L in any model scenario. Importantly, DO changes from the increased discharge scenarios are projected
to be very small (probably undetectable) relative to the existing permitted condition. Increased discharges
rates were predicted to cause only small (-0.1 mg/L) decreases in the minimum DO in Mallard Creek,
compared to the 12.0 MGD scenario. Increased discharge rates at MCWRF were also predicted to cause
negligible change to DO conditions in the Rocky River itself, compared to the 12.0 MGD scenarios. The
primary conclusion is that MCWRF's existing winter concentration limits for CBOD5 and ammonia would be
fully protective of DO in Mallard Creek and the Rocky River under higher discharge rates.
Brown AM Caldwell
19
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
References
Brown and Caldwell. 2018. Mallard Creek Water Quality Modeling —Update and Sensitivity Analysis. Technical Memorandum
No. 3 submitted to Charlotte Water. 39 p.
C142M Hill. 2001. QUAL2E-UNCAS Application to Rocky River from Mooresville WWTP to USGS Flow Gage near Norwood in
North Carolina. Draft report prepared for Cabarrus County, Charlotte -Mecklenburg utility Dept., and Union Co. Public
Works. 37 p. plus appendices.
Weaver. Curtis J., Low -flow characteristics and flow -duration statistics for selected USGS continuous -record stream gaging
stations in North Carolina through 2012., North Carolina Department of Environmental and Natural Resources, Division
of Water Resources. 2015.
Brown Catdwell
20
Mallard Creek TM -Winter 23 July 2019.docx

Brown .
Caldwell
301 Bendix Road, Suite 400
Virginia Beach, VA 23452-1385
T: 757.518.2400
F: 757.518.2401
Technical Memorandum
Prepared for: Charlotte Water
Project Title: Permitting for the Expansion of Mallard Creek WRF
Project No.: 151553
Technical Memorandum No. 5
Subject:
Mallard Creek Water Quality Modeling - Winter Condition
Date:
July 23, 2019
To:
Irene (Tesha) Okioga, Project Manager, Charlotte Water
From:
George Anipsitakis, Brown and Caldwell
Copy to:
Prepared by:
Clifton F. Bell, PE, PG
Reviewed by: _
Douglas J. Durbin, PhD
Limitations:
This document was prepared solely for CLT Water in accordance with professional standards at the time the services were performed and in
accordance with the contract between CLT Water and Brown and Caldwell dated July 24, 2017. This document is governed by the specific scope of
work authorized by CLT Water; it is not intended to be relied upon by any other party except for regulatory authorities contemplated by the scope of
work. We have relied on information or instructions provided by CLT Water and other parties and, unless otherwise expressly indicated, have made
no independent investigation as to the validity, completeness, or accuracy of such information.

Mallard Creek Water Quality Modeling - Winter Condition
Table of Contents
List of Figures
List of Tables ................
Section 1: Executive Summary ..............................................................................................
Section2: Background.......................................................................................................... ..... 5
........... .............
Section 3: Representation of Winter Conditions in QUAL2K.............................................................
3.1 7Q10 Streamflow Values................................................................................................................................ 6
3.2 Permitted Effluent Limits............................................................................................................. 6
3.3 Average Air Temperature and Cloud Cover.................................................................... 7
.................
3.4 Dissolved Oxygen Concentrations and Water Temperature ............................................ ............ 7
.................
Section4: Sensitivity Analysis................................................................................................. ............ 9
....................
4.1 Mallard Creek................................................................................................................
4.2 Rocky River.................................................................................................................................. ..................15
Section 5: Summary and Conclusions....................................................................................... ..19
.........................
References........................................................................................................................ ... 20
...................................
List of Figures
Figure 4-1: Scenario 1: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) at Three Outfall Discharge Rates with Best Available Estimates of CBOD
Decayand Nitrification Rates.......................................................................................................... .......12
Figure 4-2: Scenario 2: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate..............13
Figure 4-3: Scenario 3: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) Creek with Nitrification Rate 50 Percent Above Best Available Estimate....14
Figure 4-4: Scenario 4: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky
River (represented by 0 km) with CBOD Decay and Nitrification Rate 50 Percent Above Best Available
Estimate........................................................................................................................................... ...15
..............
Figure 4-5: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with Best Available Estimates of CBOD Decay and Nitrification Rates.................16
Figure 4-6: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate ......................16
Figure 4-7: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with Nitrification Rate 50 Percent Above Best Available Estimate ........................17
Figure 4-8: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point
(Represented by 0 km) with CBOD Decay and Nitrification Rates 50 Percent Above Best Available
Estimate............................................................................................................................ .........18
.......................
Brown Aw Caldwell
ii
Mallard Creek TMWinter23 July 2019.docx

Mallard Creek Water Quality Model - Winter Condition
List of Tables
Table 2-1. Existing Effluent Limitations and Monitoring Requirements Mallard Creek Water Reclamation
Facility, Outfall 001............................................................................................................................................ 5
Table 3-1. Winter 7Q10 Streamflows from Weaver(2015)................................................................................... 6
Table 3-2. WWTP Effluent Limits and Associated Model Inputs............................................................................ 7
Table 4-1. Summary of Model Scenarios for Sensitivity Analysis........................................................................10
Table 4-2. Summary of Model Scenarios for Sensitivity Analysis........................................................................11
Brown —Caldwell
iii
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
Section 1: Executive Summary
Charlotte Water (CLTWater) is a public water and wastewater utility that serves customers within the City of
Charlotte and greater Mecklenburg County area. CLTWater owns and operates the Mallard Creek Water Rec-
lamation Facility (MCWRF) located on Mallard Creek, a tributary to the Rocky River. MCWRF is currently per-
mitted to discharge 12 million gallons per day (MGD) to Mallard Creek. In response to growth demands, CLT-
Water is planning an upgrade to the facility that would increase the total discharge to 14.9 MGD and
eventually to 16 MGD. This technical memorandum presents the methods and results of the water quality
modeling that was performed to determine whether MCWRF's existing CBOD5 and ammonia limits would be
protective of dissolved oxygen (DO) in Mallard Creek and the Rocky River during the winter condition (No-
vember through March).
The modeling approach with summer condition parameters was described in a prior technical memorandum
entitled Mallard Creek Water Quality Modeling Approach (Brown and Caldwell, 2018) that CLTWater submit-
ted to DEQ in March 2018. The same model was adapted to winter conditions as described in this technical
memorandum. This adaptation includes the use of winter 7Q10 streamflows, water temperatures, meteoro-
logical conditions, background dissolved oxygen conditions, and NPDES permit limits. Historical monitoring
data indicated that, of the winter months, March had the highest water temperatures, so March monitoring
data were used to characterize many model inputs such as dissolved oxygen and temperature of headwaters
and incremental inflows.
DO was not predicted to fall below 5.0 mg/L in any model scenario. Increased discharge rates were pre-
dicted to cause only small (-0.1 mg/L) decreases in the minimum DO in Mallard Creek, compared to the
12.0 MGD scenario. Increased discharge rates at MCWRF were also predicted to cause negligible change
(<0.05 mg/L) in DO conditions in the Rocky River itself, compared to the 12.0 MGD scenarios. Based on
these results, it was concluded that MCWRF's existing concentration limits for DO, CBOD5, and ammonia
would be protecting of water quality under increased discharge rates.
Brown —Caldwell
4
Mallard Creek TM -Winter 23 July 2019.dm

Mallard Creek Water Quality Modeling - Winter Condition
Section 2: Background
CLTWater is a public water and wastewater utility that serves customers within the City of Charlotte and
greater Mecklenburg County area. CLTWater owns and operates the Mallard Creek Water Reclamation
Facility (MCWRF) located on Mallard Creek, a tributary to the Rocky River. MCWRF is currently permitted to
discharge 12 million gallons per day (MGD) to Mallard Creek. In response to growth demands, CLTWater is
planning an upgrade to the facility that would increase the total discharge to 14.9 MGD and eventually to 16
MGD.
For the expansion, CLTWater submitted a speculative limits request letter to DEQ in September 2018, and
DEQ provided speculative limits in February 2019. The summer speculative limits for dissolved oxygen (DO),
five-day carbonaceous oxygen demand (CBOD), and ammonia nitrogen partially relied upon a QUAL2K-based
modeling evaluation of DO sensitivity in Mallard Creek and the Rocky River (Brown and Caldwell, 2018). The
previous modeling analysis demonstrated that MCWRF's existing summer (April -October) limits (Table 2-1)
would be protective of DO in the receiving water. The purpose of this technical memorandum is to present
the methods and results of a similar evaluation for winter (November - March) conditions.
Parameter
Monthly Average
Weekly Average
Daily Average
Flow
12 MGD
NA
NA
CBOD, 5 day (Apr. i - Oct 31)
4.2 mg/L
6.3 mg/L
NA
CBOD, 5 day (Nov.1- Mar. 31)
8.3 mg/L
12.5 mg/L
NA
Total suspended solids
30.0 mg/L
45 mg/L
NA
NH3 as N (Apr. 1- Oct 31)
1.0 mg/L
3.0 mg/L
NA
NH3 as N (Nov. 1- Mar. 31)
2.0 mg/L
6.0 mg/L
NA
Dissolved oxygen
NA
NA
6.0 mg/L
Fecal coliform (geometric mean)
200/100 mL
400/mL
NA
Temperature (deg. C)
Monitor and report only
Total zinc
Monitor and report only
pH
Between 6.0 and 9.0 s.u.
Chronic toxicity
Pass at effluent concentration of 90%
Effluent pollutant scan
Monitor and report only
Section 3: Representation of Winter Conditions in QUAL2K
This section describes how the critical winter condition was represented in QUAL2K. The modeling team
used the summer model documented by Brown and Caldwell (2018) as the starting point for the winter
model. The summer model itself was a QUAL2K-based version of a prior QUAL2E-UNCAS model developed
and documented by CH21VI Hill (2001). The modeling team updated the summer QUAL2K model to represent
winter 7Q10 flows, temperatures, background DO concentrations, and point source discharges. The month
of March was used to represent air and water temperatures, because March is at the end of the winter
BrownAwCaldwell
5
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
season and tends to have the highest temperatures of the season, and thus yields the most conservative
model outputs. The specific parameters that were altered for the winter condition are:
• 7Q10 streamflow values
• Permitted limits for wastewater treatment plants (WWTPs)
• Average air temperature and cloud cover
• DO concentrations and water temperature in headwaters and incremental inflows
Sections 3.1 through 3.4 describe the adaption of the previous QUAL2K model to represent winter
conditions. Other model characteristics, including the model segmentation and point sources, were
unchanged from the summer QUAL2K model. See Brown and Caldwell (2018) and CH2M Hill (2001) for
more background on the QUAL2K model segmentation and other model characteristics.
3.1 7Q10 Streamflow Values
According to the fact sheet for MCWRF's existing NPDES permit, the facility's existing winter limits were
based on a Mallard Creek winter 7Q10 value of 2.1 cfs. The fact sheet did not cite a source or year range
upon which this value was based. For the present modeling exercise, the USGS provided an updated winter
7Q10 value of 2.2 cfs based on 1995-2011 stream gaging data, adjusted to reflect the Mallard Creek
drainage area at the point of the MCWRF discharge (J. Weaver, USGS, elec. comm., 22 Mar 2018). This
value was used in the QUAL2K model as the Mallard Creek headwater flow. USGS also provided an updated
estimate of the average annual streamflow discharge at this location (42.2 cfs).
Table 3-1. Winter 7Q10 Streamflows from Weaver (2015)
Location Winter 7Q 10 (cfs)
Mallard Creek 2.2
Rocky River near Norwood 79
The winter 7Q10 for the Rocky River at Norwood (79 cfs) was obtained from Weaver (2015) and was based
on 1930-2012 stream gaging data. Using the flows from the summer version of the QUAL2K model as a
starting point, the simulated flows into model headwaters (with the exception of Mallard Creek) and incre-
mental inflows were increased by the same proportion until the summed flows matched the 79 cfs value at
Norwood.
3.2 Permitted Effluent Limits
As documented by Brown and Caldwell (2018), the QUAL2K model includes four WWTPs in addition to the
MCWRF. WWTP flows and effluent parameters in the model were based on each facility's current NPDES
permit, which was obtained from the North Carolina Department of Environmental. Quality (NCDEQ) on May
24, 2018. For the winter conditions model, the WWTPs were included at their full permitted flows (Table3-2),
maximum monthly average concentrations of BOD/CBOD and ammonia for winter months, and minimum
effluent DO concentrations. The f-ratios (e.g., ratio of CBOD-ultimate to CBOD5) were assumed to be the
same as those used in developing the summer model, and so the CBOD-ultimate inputs for the winter model
were calculated by multiplying the summer model CBOD-ultimate concentrations by the ratio of the winter
limits to the summer limits. The Mooresville WWTP has only one set of BOD5 limits that applies year-round.
Brown —Caldwell
Mallard Creek TM -Winter 23 July 20A.docx

Mallard Creek Water Quality Modeling - Winter Condition
Permit Component
NPDES Permit Number
Receiving Water
Flow (Monthly Average MGD)
BODS (mg/L) (April to October)
(Monthly Average)
BOD5 (mg/L) (Novemberto
March) (Monthly Average)
CBODS (mg/L) (April to Octo-
ber) (Monthly Average)
CBODS (mg/L) (November to
March) (Monthly Average)
TSS (mg/L) (Monthly Average)
Summer CBODu (mg/L)
Winter CBODu (mg/L)
NH3-N (mg/L) (April to October)
(Monthly Average)
NH3-N (mg/L) (November to
March) (Monthly Average)
DO (mg/ Q (as Daily Average in
Effluent)
PH
Mooresville
(Rocky River)
WWIP
NCO046728
Dye Creek
5.5
15.0
N/A
N/A
30.0
24.5
24.5
2.0
z 6.0
6.0 - 9.0
Mallard Creek
WRF
NCO030210
Mallard Creek
12.0
N/A
Facilities
Concord (Rocky
Muddy Creek
River Regional)
WWfP
WWrP
NCO036269
NCO081621
Rocky River
Rocky River
24.0
0.3
N/A
10.0
Monroe WWrP
NCO024333
Richardson
Creek
10.4
7.3
N/A ! N/A I 20.0 I 14.5
4.2 1 17.0 1 N/A I N/A
8.3
30.0
16.0
31.5
25.0
N/A
N/A
30.0
62.9 -
92.5
30.0
30.0
38.0
14.5
76.0
28.8
1.0
4.0
4.0
1.0
2.0
2.0
10.0
8.0
> 6.0
2 6.0
z 5.0
5.0
6.0-9.0
6.0-9.0
6.0 9.0
6.0-9.0
3.3 Average Air Temperature and Cloud Cover
Average air temperature for the winter condition was referenced using the weather station at Charlotte Doug-
las International Airport. Historical temperature and dew point values were averaged across all recorded val-
ues for March 2019. The average temperature was 9.84 °C and the average dew point temperature was
0.89 ° C. Cloud cover was set to 50 percent based on historical percent cloud cover conditions for Charlotte
NC. Data was referenced from Weather Spark, which compiles historical weather data for many locations
around the world.
3.4 Dissolved Oxygen Concentrations and Water Temperature
Dissolved oxygen concentrations for incremental inflows and headwater flows were obtained from DEQ and
EPA monitoring station data downloaded from the National Water Quality Monitoring Council website
(https://www.wateroualitydata.usl-por+r ). The data were used to characterize average March DO and water
temperatures of headwaters (excluding Mallard Creek) and incremental inflows to the Rocky River as shown
in Table 3-3.
Brown- Caldwell
7
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
Monitoring Station
21NCOIWQ-Q7330000
21NCCOALrfIONS-Q7450000
21NCCOALMONS-Q7600000
21NCCOALMONS-Q7780000
21NC01WQ.Q8210000
21NCO2WQ-QS210000
21NCCOALITIONS-Q8385000
21NC01WQ-Q9120000
DO Concentrations
Water Temperature
(Ill
('C)
Application to QUAL2K Winter Model
9.72
12.42
Applied to all incremental inflows/headwaters upstream of and in-
cludin West Branch se ments 1-4
10.80
8.90
Applied to all incremental inflows/headwaters downstream of West
Branch and upstream of Mallard Creek (segments 5-10)
10.60
9.50
1 Applied to all incremental inflows between Mallard Creek and Cod-
dle Creek (s ent 12
10.30
9.90
Applied to all incremental inflows between Coddle Creek and Irish
Buffalo Creeks (segments 13-1
9•97
11.11
Average of these values applied to all incremental inflows between
9•99
12.35
Coldwater and Dutch Buffalo Creeks (segment 17)
9.90
11.10
APplled to all incremental between Dutch Buffalo and Crooked
Creek (segments 18-23)
10.72
10.38
_
Applied to all incremental inflows between Crooked Creek and
model end se ants 24.31
As required by MCWRF's NPDES permit, CLTWater staff monitors water quality on Mallard Creek both up-
stream and downstream of the MCWRF outfall, and on the Rocky River downstream of the Mallard Creek
confluence. Mallard Creek headwater, incremental inflow, and point source temperature inputs were charac-
terized using 2009-2019 water quality monitoring data provided by CLTWater (Table 3-4). Average values for
March were used. Effluent temperature data from 2009 to 2019 for downstream of the outfalls of the four
other WWTPs along the Rocky River were provided by NC Division of Water Resources (DWR) (Table 3-4). The
average temperatures for March were used.
BrownAlCaldwell
8
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling — Winter Condition
Model Input
Mallard Creek Headwater
MCWRF Effluent
Incremental inflows to Mallard
Creek downstream of MCWRF out -
fall
Monroe WWTP Effluent
Concord (Rocky River Regional)
WWfP Effluent
Mooresville (Rocky River) WWrP
Effluent
Muddy Creek WWrP Effluent
DO Concentrations
(mg/0
10.58
Water Temperature Basis
(°C)
10.1
Based on daily average 17.4
permit limit (6.0 nl
9.80 8.90
Based on daily average 16.4
permit limit (5.0 mg/L)
Based on daily average 16.8
permit limit (6.0 mg/L)
Based on daily average
permit limit (6.0 ril
Based on daily average
permit limit (5.0 mg/L)
Section 4: Sensitivity Analysis
1 Average March values from 2009-2019 monitoring
_ _data upstream of MCWRF outfall
9 Temperature based on average March values from
2009-2019 MCWRF DMR monitoring data
DO based on average March DO concentrations from
2009-2019 monitoring data on Mallard Creek down-
stream of MCWRF outfall. Temperature set to match av-
erage March temperature from upstream segment of
the Rocky River abovethe Mallard Creek confluence.
6 Average March values from 2009-2019 DMR data
downstream of Monroe WWTP outfall
Average March values from 2009-2019 DMR data
4 downstream of Concord (Rocky River Regional) WWTP
_� -- outfall
15.03 Average March values from 2009-2019 DMR data
downstream of Mooresville (Rocky River) WWTP outfall
13.45 Average March values from 2009-2019 DMR data
downstream of Muddy Creek WWTP Effluent outfall
After the winter 7Q10 version of the QUAL2K model was developed, it was applied to determine whether DO
in the receiving water would be sensitive to changes in the MCWRF flow rate and CBOD5/ammonia loads. All
model scenarios utilized MCWRF's existing winter CBOD5 and ammonia nitrogen concentration limits. Three
different MCWRF discharge rates were examined: 12.0 MGD (existing), 14.9 MGD, and 16.0 MGD. Model
results were examined to determine if DO was predicted to fall below 5.0 mg/L in the receiving water or in
the Rocky River below the Mallard Creek confluence, or whether DO was predicted to change significantly
with MCWRF discharge rate. The CBOD5 oxidation rate and nitrification rates also were varied to determine
the sensitivity of predictions to these values (Table 4-1). The cited magnitudes of the rates listed in Table 4-1
are for 20°C. However, the rates are temperature -dependent, and so QUAL21K automatically adjusts the rates
based on the predicted water temperature of each segment. The best available value for the CBOD5
oxidation rate was derived from CBOD bottle tests performed by CLTWater in 2018, and the best available
nitrification rate was derived from the 2001 calibrated model (CH2M Hill, 2001). See Brown and Caldwell
(2018) for more information on the derivation of these rates.
Brown ,- Caldwell
9
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
Scenario
MCWRF
Mallard Creek
Mallard Creek
Number
Description
Flow
CBOD5
Oxidation Rate
Nitrification Rate
(MGD)
_
(dayl)
(day-')
y- )
Best rate
12.0
0.25
0.25
1A
0.06
1B
14.9
0.06
estimates
16.0
0.25
1C
0.06
0.09
0.09
2A
12.0
HigherCBOD 14.9
0.25
2B
0.25
oxidation rate
16.0
12.0
Higher 14.9
nitrification rate _
16.0
12.0
Higher CBOD
oxidation+ 14.9
nitrification rates
2C
0.09
0.25
3A
0.06
0.375
3B
0.06
0.375
3C
0.06
0.375
4A
0.09
0.375
4B
0.09
0.375
4C
I 16.0
0.09
0.375
4.1 Mallard Creek
Table 4-2 presents the minimum predicted DO values in Mallard Creek by scenario, as well as the predicted
change in minimum DO from the 12 MGD discharge scenario. Figures 4-1 through 4-4 are the simulated
Mallard Creek DO profiles for the model scenarios categories 1 through 4, respectively. In Figures 4-1
through 4-4, location zero (0 km) represents the confluence of Mallard Creek with the Rocky River and is the
most downstream point of Mallard Creek. Each figure includes a marker where the MCWRF effluent enters
Mallard Creek.
BrownAND [dwell
10
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
MCWRF
Scenario Description Flow
Number I (MGD)
3A
12.0
149
18
Bestavailable
rate estimates
1C
16.0
12.0
2A
14.9
I
2B
HigherCBOD
oxidation rate
2C
16.0
12.0
3A
14.9
313
Higher
nitrification rate
16.0
3C
12.0
4A
Higher CBOD
4B
oxidation +
14.9
4C
nitrification rates
16.0
Minimum
Predicted DO
(mg/L)
6.62
6.55
6.53
6.60
6.53
6.51 1
6.60
6.53
6.51
6.58
6.51
6.49
Change in Min.
DO from
12 MGD
Discharge
(mg/L)
-0.07
-0A0
-0.07
-0.09
-0.07
-0.09
-0.07
-0.09
Rocky River Segment Below Mallard
Creek Confluence
Change in Min.
Minimum
DO from
Predicted DO
12 MGD
(mg/L)
Discharge
(mg/ L)
7.19
7.21
0.02
7.22
0.02
7.19
7.21
0.02
7.22
0.02
7.19
-
7.21
0.02
7.22
0.02
7.19
-
7.21
0.02
7.22
0.02
The winter QUAL2K model predicted that DO in Mallard Creek would decrease downstream of the MCWRF
outfall and start to increase again prior to the confluence with the Rocky River. The location of the minimum
DO value was predicted to occur between -2.5 and 3.3 km below the outfall, with the greater distances
predicted in scenarios with higher CBOD5 oxidation and nitrification rates. Under no scenario was DO in
Mallard Creek predicted to fall below 5.0 mg/L. The predicted DO minima in Mallard Creek had a low
sensitivity to changes in the MCWRF effluent; discharges of 14.9 and 16.0 MDG were only predicted to
decrease DO -0.1 mg/L relative to a discharge rate of 12.0 MGD. DO predictions were not very sensitive to
the CBOD oxidation or nitrification rates. This suggests that the small differences in predicted DO between
MCWRF discharge rates were primarily driven by the MCWRF effluent DO concentration and/or differences in
in -stream reaeration rates, rather than oxygen demand from CBOD or ammonia in Mallard Creek.
Brown --Caldwell
11
Mallard Creek TM -Winter 231uly 2019.doex

Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
ao
E
C: 8.0
Cu
on
x
O
m 7.0
O
N
N
6.0
* 1A -12 MGD
•1B-14.9MGD
1C -16 MGD
A Mallard Creek WRF
5.0
4.0
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Location (km)
Figure 41: Scenario 1: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) at Three Outfall Discharge Rates with Best Available Estimates of CBOD Decay and Nitrification
Rates.
Brown —Caldwell
12
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
OD
E
v 8.0
bD
X
O
v 7.0
O
N
6.0
02A- 12 MGD
♦213-14.9 MGD
m 2C- 16 MGD
Mallard Creek WRF
fj
w
6 s ■
5.0
4.0
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Location (km)
Figure 4-2: Scenario 2: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate.
BrownA-Cald%-Mt
13
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
m
E
v 8.0
to
a
x
O
7.0
0
0
6.0
5.0
9 . 6 a 9 0 !
,A
F 3A-12 MGD
!313- 14.9 MGD
3C- 16 MGD
w Mallard Creek WRF
4.0
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
Location (km)
Figure 4-3: Scenario 3: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by 0 km) Creek with Nitrification Rate 50 Percent Above Best Available Estimate.
Brown Am- Caldwell
14
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11.0
10.0
9.0
J
M
!_
C 8.0
UJ
to
X
O
_2 7.0
O
0
6.0
5.0
4.0
5.0
4.5
4.0 3.5
It
3.0 2.5 2.0
Location (km)
■4A-12MGD
®4B- 14.9 MGD
a4C-16MGD
♦ Mallard Creek WRF
1.5 1.0 0.5 0.0
Figure 4-4: Scenario 4: Dissolved Oxygen Concentration Along Mallard Creek to the Confluence with Rocky River
(represented by O.km) with CBOD Decay and Nitrification Rate 50 Percent Above Best Available Estimate.
4.2 Rocky River
Table 4-2 presents the minimum predicted DO values in the Rocky River segment below the Mallard Creek
confluence by scenario, as well as the predicted change in minimum DO from the 12 MGD discharge
scenario. Figures 4-5 through 4-8 illustrate the simulated Rocky River DO profiles for the model scenarios
categories 1 through 4, respectively. In Figures 4-5 through 4-8, location zero (0 km) represents the
downstream -most portion of the model domain. Each figure includes a marker where Mallard Creek enters
the Rocky River. The major discontinuities in the DO profiles are caused by the entry of tributary flows with
different DO than the Rocky River.
Under the existing permitted condition scenario 1A, the confluence of Mallard Creek and the Rocky River is
located at a point where the Rocky River is recovering from an upstream DO sag (Figure 4-5), which is itself
caused by inputs from West Branch, Mooresville (Rocky River) WWTP, and Clarke Creek. This upstream DO
sag could be significantly overestimated due to the overestimation of the CBOD decay rates in upstream
model segments, as discussed in previous sections and by CH2M Hill (2001).
As shown in Table 4-2, increased discharge rates from MCWRF were predicted to cause only very small
changes in the minimum DO in the Rocky River below the Mallard Creek confluence.
Brown—Catdwell
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Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
0 6
5
1A- 12 MGD
1B - 14.9 MGD
■ 1C - 16 MGD
♦ Mallard Creek
Confluence
120 100 80 60 40 20 0
Location (km)
Figure 4-5: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with Best Available Estimates of CBOD Decay and Nitrification Rates.
11
■
10 ■
■
■
9 ■
aLn ■
E ■
C 8
X
x
O
-0 7
v
0 ■
Z
5
■ 2A- 12 MGD
• 2B - 14.9 MGD
■ 2C-16 MGD
♦ Mallard Creek
Confluence
4
120 100 80 60 40 20 0
Location (km)
Figure 4-6: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with CBOD Decay Rate 50 Percent Above Best Available Estimate.
Brown Catdwett
16
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11
r
10 ■
■ rr�
r
■
9 ■
J
i
OD
!_ ■
8 r
■ 3A- 12 MGD
ao
X
0 d
0 7
v
0
N r
6
5
4
120
• 313- 14.9 MGD
• 3C -16 MGD
♦ Mallard Creek
Confluence
100
v
80 60 40
Location (km)
20 0
Figure 4-7: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with Nitrification Rate 50 Percent Above Best Available Estimate.
Brown — Caldwell
17
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
11
0 6
5
4
120
4A- 12 MGD
413 -14.9 MGD
•4C-16MGD
A Mallard Creek
Confluence
100
80 60 40 20
0
Location (km)
Figure 4-8: Dissolved Oxygen Concentration Along the Rocky River to the Downstream Model End Point (Represented
by 0 km) with CBOD Decay and Nitrification Rates 50 Percent Above Best Available Estimate.
BrownAw Caldwell
18
Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling — Winter Condition
Section 5: Summary and Conclusions
The modeling exercise presented here was not a full-scale recalibration of previous models but rather was a
sensitivity -based exercise of whether MCWRF's existing permit limits would be protective of DO under higher
effluent discharge rates (14.9 and 16.0 MGD). The primary basis for evaluation was whether the updated
model predicts that higher discharge rates (14.9 and 16.0 MGD) would cause significant decreases in DO in
Mallard Creek and the Rocky River, relative to the 12.0 MGD model scenarios. The updated model relied
upon recent CBOD bottle tests to improve estimates of the local CBOD oxidation rate. Higher CBOD and
nitrification rates were also explored as part of the sensitivity analysis. DO was not predicted to fall below 5.0
mg/L in any model scenario. Importantly, DO changes from the increased discharge scenarios are projected
to be very small (probably undetectable) relative to the existing permitted condition. Increased discharges
rates were predicted to cause only small (-0.1 mg/L) decreases in the minimum DO in Mallard Creek,
compared to the 12.0 MGD scenario. Increased discharge rates at MCWRF were also predicted to cause
negligible change to DO conditions in the Rocky River itself, compared to the 12.0 MGD scenarios. The
primary conclusion is that MCWRF's existing winter concentration limits for CBOD5 and ammonia would be
fully protective of DO in Mallard Creek and the Rocky River under higher discharge rates.
Brown Caldwell
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Mallard Creek TM -Winter 23 July 2019.docx

Mallard Creek Water Quality Modeling - Winter Condition
References
Brown and Caldwell. 2018. Mallard Creek Water Quality Modeling —Update and Sensitivity Analysis. Technical Memorandum
No. 3 submitted to Charlotte Water. 39 p.
CH2M Hill. 2001. QUAL2E-UNCAS Application to Rocky River from Mooresville WWTP to USGS Flow Gage near Norwood in
North Carolina. Draft report prepared for Cabarrus County, Charlotte -Mecklenburg utility Dept., and Union Co. Public
Works. 37 p. plus appendices.
Weaver. Curtis J., Low -flow characteristics and flow -duration statistics for selected USGS continuous -record stream gaging
stations in North Carolina through 2012., North Carolina Department of Environmental and Natural Resources, Division
of Water Resources. 2015.
Brown —Caldwell
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Mallard Creek TM -Winter 23 July 2019.doex