NC0081621_Comments_20190315

ui Willis
ENGINEERS
March 15, 2019 1968.019 (34)
Mr. Qais Banihani
NC DEQ/ Division of Water Resources RECE1l/ED/nr-t-
NPDES Complex Permitting Unit NRfDW
1617 Mail Service Center MAR 18 2019
Raleigh, NC 27699-1617
Water Fioltources
Subject: Response to Draft NPDES Permit
f'�rmitting Section
NPDES Application NC0081621
Water and Sewer Authority of Cabarrus County
Muddy Creek WWTP
Dear Mr. Banihani:
The Water and Sewer Authority of Cabarrus County(WSACC)has previously submitted a request
for additional flow at the Muddy Creek Wastewater Treatment Plant. The Plant is currently
permitted at 0.3 million gallons per day(MGD)and the WSACC Expansion Application requested
an increase to 1.0 MGD. Although that request is supported by the WSACC Master Plan, the
NPDES Complex Permitting Unit has advised it will only issue a Permit for flow projections
arrived at using the methodology outlined in the Engineering Alternatives Analysis (EAA)
Guidance Document. Using this methodology based on historical growth in Midland, a Permit
of 0.53 MGD could be issued. The Draft Permit also includes new limits for several constituents
that are significantly more stringent than the current Permit.
WSACC believes that it can offer a compelling argument for its original 1.0 MGD request utilizing
the population projections developed by the North Carolina State Demographer which are
further supported by recent development activities in the area. Growth in Midland over the
past few years has been relatively slow but there is significant interest from the development
community and the Town has received numerous requests for wastewater service.
Unfortunately, the Town of Midland and ultimately WSACC cannot yet accept these requests
for additional flow because they are limited in the amount of wastewater treatment service
they can provide. We suggest that a more accurate representation of future growth in the area
is derived from projections by the North Carolina State Demographer who predicts growth
within the Midland service area to be significantly higher than the trend demonstrated over the
past few years. This finding is consistent with the WSACC Master Plan and is further supported
by requests for over 343,000 gallons per day of additional flow which are currently under
review.
10700 Sikes Place,Suite 115
Charlotte, North Carolina 28277
704.377.9844/NC License F-0114

Mr.Qais Banihani
March 15,2019
Page 2 of 2
Attached for your consideration is a calculation based on projections from the State
Demographer which would indicate an increase in flow to approximately 0.95 MGD through the
year 2040. Also attached for your review is a tabulation of requests received by the Town of
Midland which further support the justification for a larger Permit. We hope that the Complex
Permitting Unit will consider this additional information along with our previous documentation
and honor WSACC's request for 1.0 MGD NPDES Permit.
WSACC also requests that the Complex Permitting Unit reconsider some of the effluent
limitations presented in the previous Draft Permit. The Draft Permit and Fact Sheet indicate
significantly more restrictive proposed Permit conditions for the 0.53 MGD Plant. In particular
BOD5 and NH3-N limits are significantly more stringent. The Fast Sheet lists the basis of the new
limits as a series of instream models performed during the 1980s and 1990s. While revisiting
this work in 2007,the Division cautioned that the previous modeling effort may not be accurate.
It seems inappropriate that new limits be based on a thirty year old model simulation with
questionable accuracy, especially since the requested permit is significantly smaller than the
facility envisioned in 2007. This information is detailed in the November 21, 2007 letter to Van
Rowell at WSACC and in the October 25, 2007 NCDWR Memo, copies of which are attached.
WSACC therefore requests that a new 1.0 MGD Permit be issued with effluent characteristics
similar to the existing Permit, at least up to the 0.5 MGD level. This would allow WSACC to
continue with orderly expansion of the facilities at Muddy Creek while additional instream
evaluations are conducted, which may justify lesser effluent limits.
We appreciate your consideration of these requests. Should you have any questions or need
any additional information please let me know.
15 MAR 2019
Yours very truly, ,0`,0N CARO'/''.
WILLIS ENGINEERS O-bESSIp 1/..
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Charles A. Willis,Jr., PE, BCEE '<��S' 'N• �' ��/.,
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Attachments
cc: Water and Sewer Authority of Cabarrus County

WSACC Population and Flow Projection
Muddy Creek WWTP NPDES
The Muddy Creek service area, located in Cabarrus County (County), North Carolina is expected to
undergo substantial growth over the next 20 years due to its proximity to the Charlotte Metropolitan area.
The County is seeing increased growth rates which have been projected to continue through 2038 by the
North Carolina State Demographer.
In the past year, the Muddy Creek Service area has received requests for flow allocation from several
planned subdivisions in the area. The WWTP already has an existing commitment of 70,000 gallons per
day and a requested commitment of 343,320 gallons per day from developers. When these flows are
added to the existing WWTP flow rate, it yields a total flow rate of 553,320 gallons per day,exceeding the
draft Permit level of 0.530 Million Gallons per Day(MGD)which was derived from the growth rates of the
Town of Midland.
Below is a population projection using the growth rate of the County applied to the Muddy Creek service
area. This projection has a resultant value very similar to the resultant flow projection of the WSACC
Master Plan,further confirming the validity of its result.
Engineering Alternatives Analysis Linear Extrapolation Method—Census Data
Assumptions:
Current Flow: 0.1400 MGD (2018 Last 6 Month Avg.)
2017 Cabarrus County Population: 205,204(2017 NC Census Estimate)
2038 Cabarrus County Projection: 294,680(2038 NC Census Projection)
Future Residential Flow Per Capita: 70 gal/capita (EAA Guidelines)
Future Commercial Flow Per Capita: d 15 gal/capita (EAA Guidelines)
Future Industrial Flow: 25,000 gallons (Estimate)
Muddy Creek Service Area: 36 square miles
Cabarrus County Area: 364 square miles
Calculations:
Annual Population Increase in Cabarrus County:
294,680—205,204 people
= 4,261 in Cabarrus County
21 years year -
Annual Estimated Population Increase in Muddy Creek Service Area from County Growth Rate:
4 261 people x 36 miles2 = 421 people in Muddy Creek Service Area
' year 364 miles2 year
Muddy Creek Service Area Population Increase from 2018 to 2040:
421 people x (2040— 2018) = 9,262 additional people
year
Willis Engineers
1968.019 2 s March 2019

WSACC Population and Flow Projection
Muddy Creek WWTP NPDES
Flows from Population Increase through 2040:
Residential: 9,262 capita x 70 gal apita = 648,340 gallons
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Commercial: 10,197 capita x 15 capita = 138,930 gallons
Total Daily Flows in 2040(Current Flow Rate plus Flows from Population Increase through 2040):
140,000 + 648,340 + 138,930 + 25,000 = 952,270 gallons
In conclusion, the growth rates in Cabarrus County provides a better representation of the projections in
the Muddy Creek Service area. By applying data for the entire county to the service area, the Linear
Extrapolation Method provides projections that more closely align with the WSACC Master Plan and
further justify the requested flow rates of the proposed facilities.
15 MAR 2019
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Willis Engineers
1968.019 2 March 2019

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Town of Midland Residential Development List 1/17/2019
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' -APiojeet:Nate4 e _ Project Location Est #btSPUnit F,I 4l:4t.,t
A#e4geMZjniW:
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,-;
,,, - 55446873590000,
55447931030000,
Cedar Creek NC Hwy 24/27 65.25 130
-.;iig;?: 55447869890000,
55447990740000
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Little Property Midland Road 48.68 132 220 55443633360000
Robinson Trust Property Bethel School Road 43.30 150 55448336370000
Queen's Property\Loving Property NC Hwy 24/27 234.44 395
TM'te 55556289380000
TOTAL: 391.67 807 220
GRAND TOTAL: 1027
Approx.Wastewater Flow(360 gpd/unit SF&240 gpd/unit TH) 343,320 gpd
Notes:
1 The above listed developments are within the current Midland town limits and have by right zoning for residential development.
2 After due diligence conversations with two town-center developers,the town has learned that more roof tops are needed to support the business
case for the commercial and retail development the town desires at the crossroads of HWY 24/27 and HWY 601.

•
O�\NA T /Q Michael F.Easley,Governor
• William G.Ross Jr.,Secretary
.. r North Carolina Department of Environment and Natural Resources
1 45 . 'C Coleen H.Sullins,Director
wta. Division of Water Quality
November 21, 2007
Mr.Van Rowell
Water&Sewer Authority of Cabarrus County
P.O. Box 428
Concord, North Carolina 28026-0428
Subject: Speculative Effluent Limits
WSACC Muddy Creek WWTP NC0081621
Proposed Expansion
Cabarrus County
Dear Mr. Rowell:
This letter is in response to your request for speculative effluent limits for a proposed expansion of Muddy Creek
WWTP from 0.3 MGD to 5.0 MGD of wastewater discharging to the Rocky River.
Receiving Stream: Muddy Creek WWTP discharges into the Rocky River. This segment of the Rocky River is
classified C waters. It should be noted that the Rocky River is impaired for turbidity. Therefore, any expansion
should not have any further impact on the turbidity in the Rocky River.
Speculative Limits: The speculative limits were developed based on an EPA-approved QUAL2E model on the
Rocky River. The model was run for Muddy Creek WWTP at the current permitted discharge of 0.3 MGD and the
proposed expansions to 5.0 MGD.
Based on available information, speculative effluent limits for the proposed discharges of 1.0/2.0/5.0 MGD to the
Rocky River are presented in Table 1. A complete evaluation of these'limits and monitoring frequencies in
addition to monitoring requirements for metals and other toxicants, will be addressed upon receipt of a formal
NPDES permit application request.
The model results indicate that 1.0/2.0/5.0 MGD discharges with the speculative limits presented in Table 1 will
have minor impacts on the dissolved oxygen levels in the river and will not lower the levels below the water quality
standard of'5 mg/L.
TABLE 1. Speculative Limits for Proposed Expansions
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Flow 1.0/2.0/5.0 MGD
BOD5i (April 1 —October 31) 5.0 mg/I 7.5 mg/I
BOD5, (November 1 —March 31) 10.0 mg/I 15.0 mg/I
Total Suspended Solids 30.0 mg/I 45.0 mg/I
NH3 as N, (April 1 —October 31) 1.0 mg/I 3.0 mg/I
NH3 as N, (November 1 —March 31) 2.0 mg/I 6.0 mg/I
TRC 28.0 ug/I
Fecal coliform (geometric mean) 200/100 ml 400/100 ml
Engineering Alternatives Analysis (EAA): Please note that the Division cannot guarantee that an NPDES permit
for an expansion to 1.0/2.0/5.0 MGD will be issued. Final decisions can only be made after the Division receives
and evaluates a formal permit application for Muddy Creek WWTP's proposed expansion.
None Carolina =
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North Carolina Division of Water Quality 1617 Mail Service Center Raleigh,NC 27699-1617 Phone[phone] Customer Service
Internet: www.ncwaterquality.org Location: 512 N.Salisbury St. Raleigh,NC 27604 Fax [phone]
An Equal Opportunity/Affirmative Action Employer—50%Recycled/10%Post Consumer Paper

- Mr. Lane I
Page 2 of 2 '
In accordance with the North Carolina General Statutes, the most practicable wastewater treatment and disposal
alternative with the least adverse impact on the environment is required to be implemented. 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. •
Alternatives to a surface water discharge, such as spray/drip irrigation, wastewater reuse, or inflow/infiltration
reduction, are considered to be environmentally preferable. A copy of the EAA requirements is attached to this
letter. Permit applications for new or expanding flow will be returned as incomplete if all EAA
requirements are not adequately addressed. If you have any questions regarding these requirements, please
contact the DWQ NPDES Unit at 919-733-5083.
State Environmental Policy Act (SEPA) EA/EIS Requirements: A SEPA EA or EIS document must be prepared
for all projects that 1) need a permit; 2) use public money or affect public lands; and 3) might have a potential to
significantly impact the environment. For new wastewater discharges, significant impact is defined as a proposed
discharge of >500,000 gpd and producing an instream waste concentration of > 33% based on summer 7Q10
flow conditions. For existing discharges, significant impact is defined as an expansion of>500,000 gpd additional
flow. Since the proposed discharge is an existing discharge with expansion of >500,000 gpd flow,
WSACC must prepare a SEPA document that evaluates the potential for impacting the quality of the
environment. The NPDES Program cannot accept an NPDES permit application for the expanded
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. A SEPA Environmental Assessment
(EA) should contain a clear justification for the proposed project. If the SEPA EA demonstrates that the project
may result in a significant adverse effect on the quality of the environment, you must then prepare a SEPA EIS
(Environmental Impact Statement). Since your proposed discharge is subject to SEPA, the EAA
requirements discussed above will need to be folded into the SEPA document. The SEPA process will be
delayed if all EAA requirements are not adequately addressed. If you have any questions regarding SEPA
EA/EIS requirements, please contact Hannah Stallings with the DWQ Planning Branch at [phone], ext.
555.
Should you have any questions about these speculative limits or NPDES permitting requirements, please feel free
to contact Agyeman Adu-Poku at(919)733-5083, extension 508.
Sincerely,
4 a4A.,-).-)
4("‘-'.
Susan A.Wilson, P.E.
Supervisor,Western NPDES Program
Attachment: EAA Guidance Document
cc: (without Attachment)
DWQ Mooresville Regional Office/Surface Water Protection Section
Central Files
NPDES Permit File
McKIM &CREED, P.A./Keith E. Lane, P.E.
200 MacKenan Court
Cary, NC 27511
NC Wildlife Resources Commission, Inland Fisheries/Fred Harris
1721 Mail Service Center
Raleigh, NC 27699-1721
US Fish &Wild Life/Tom Augspurger
P.O. Box 33726
Raleigh, NC 27636

NC Division of Water Quality
Planning Section—Modeling&TMDL Unit
Technical Memorandum
October 25,2007
TO: Toya Fields, Western NPDES Unit
CC: Kathy Stecker,Modeling &TMDL Unit
Susan Wilson,Western NPDES Unit
FROM: Pam Behm,Modeling&TMDL Unit
RE: WSACC Muddy Creek WWTP Speculative Limits—QUAL2E Model Simulation
NPDES Permit Number: NC0081621
This is in response to your request for speculative limits for a proposed expansion of the Muddy
Creek Wastewater Treatment Plant(WWTP)from 0.3 MGD to 5.0 MGD. The Rocky River
QUAL2E model,which is a low-flow, steady-state, and one-dimensional BOD model,was used
to evaluate the effect of the requested expansion on dissolved oxygen(DO) concentrations in the
Rocky River. A map of the area is provided in Figure 1.
The QUAL2E model extends 73.4 miles from Dye Branch to the USGS gage (02126000)just
below Lanes Creek near the Town of Norwood. The oldest portion of the QUAL2E model is the
upstream portion and extends 42.8 miles downstream to just below the confluence of Muddy
Creek. This portion of the model is actually a combination of three individual QUAL2E models,
which were developed for wasteload allocation. These three models are: the Mooresville
WWTP model completed in 1988,the Mallard Creek WWTP model, completed in 1992, and the
Concord Regional WWTP model, also completed in 1988. The downstream model was
developed in 2001 to extend the model down to the USGS gage in Norwood.
When the downstream model was developed, it was combined with the upstream model,but the
upstream model was not recalibrated. This means the upstream model is about 20 years old and
is based on 20-year old flow regimes. The downstream model was developed and calibrated
using very little monitoring data, although there is good time-of-travel and long term BOD data.
Most of the other parameters were estimated from data collected during one-sampling trip in
May. I am particularly concerned that tributary inputs to the Rocky are not fully accounted for in
the model. For these reasons, the Rocky River QUAL2E model is in need of recalibration and
extreme care should be taken in interpreting model results.
The model was run for the Muddy Creek WWTP current permitted discharge of 0.3 MGD and
the proposed expansion to 5.0 MGD. This discharge occurs at about river mile 43 in the model.
Figure 2 shows the simulated dissolved oxygen(DO)levels for the two different scenarios. The
model results indicate that a 5.0 MOD discharge with a monthly average BOD Jirpit of 5 mg/1
and a monthly average,< nmonia limit oft mg/1 will have minor impacts onthe DO levels in the
river,but will not lower the levels below 5 mg/1. Although the model results indicate that
1

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•
dissolved oxygen in the river would most likely meet water quality standards,the predicted
dissolved oxygen levels should be interpreted with caution. These levels would depend on flows
from tributaries and other WWTPs discharging to the Rocky River and the current river
conditions.
Analyses of dissolved oxygen data from 2000-2006 from various stations along the Rocky River
are provided in Figures 3-12. Stations Q8210000, Q8355000,and Q8385000 exhibit DO
concentrations below the standard of 5 mg/L during the summer months. The low DO values at
Station Q8385000 are of particular concern because this station is right below the Muddy'dCr k
WWTP discharge. t ' Etisan e i tti o o ,149 ��Y.Ae �W�" � ��lt641 a
cczn eqt emt ta4attle t 'gg mont ingl ncentxat ot tlil glat iii
I §h944 9449.tek 1d . ,9 CY y al§143 ainif2. ,tY0 Therefore, any expansion
should not have any further impact on the turbidity in the Rocky River.
Asart of the speculative limits request,there was also a request to determine the speculative
maximum discharge that may be permissible assuming that the plant is upgraded to best practical
technology for BOD and Ammonia removal. Due to the age of the model and the associated
uncertainties,the Rocky River QUAL2E model is not an adequate tool to determine the
maximum discharge that may be permissible.
The Rocky River QUAL2E model needs to be recalibrated and updated to current conditions
prior to considering any further speculative limit discharge requests. The model should also be
extended down to the confluence of the Rocky River and the Pee Dee River. The current model
ends at the USGS gage in Norwood and shows DO decreasing(see Figure 2). It is important to
extend the model further downstream to see if the DO recovers before it reaches the Pee Dee
River,which is impaired for low DO.
If the dischargers in this area are working together to develop a regional plan(as recommended
by DWQ earlier this year),perhaps they can include updating and expanding the QUAL2E
model as part of their planning process. This will provide the dischargers with a tool to test
various scenarios as they work towards developing a regional plan. The Modeling and TMDL
Unit can provide guidance and review of the model.
If you have any questions please contact me at 919-733-5083 ext. 506.
•