NC0081621_Speculative Limits_20071121

Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins, Director
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 NCO081621
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
Effluent Characteristic
Effluent Limitations
Monthly Average
Weekly Average
Daily Maximum
Flow
1.0/2.0/5.0 MGD
BOD5, (April 1 — October 31)
5.0 mg/I
7.5 m /I
BOD5, (November 1 — March 31)
10.0 m /I
15.0 m /I
Total Suspended Solids
30.0 m /I
45.0 mg/I
NH3 as N, (April 1 — October 31)
1.0 m /I
3.0 m /I
NH3 as N, (November 1 — March 31)
2.0 m /I
6.0 mg/I
TRC
28.0 u /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.
N'A' Karolina
Naturally
North Carolina Division of Water Quality 1617 Mail Service Center Raleigh, NC 27699-1617 Phone [phone]
Internet: vvww.ncwaterquality.or2 Location: 512 N. Salisbury St. Raleigh, NC 27604 Fax [phone]
An Equal Opportunity/Affirmative Action Employer— 50% Recycled/10% Post Consumer Paper
Customer Service
1-877-623-6748

Mr. Lane
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 [phone], extension 508.
Sincerely,
CP
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 IN
N
RE: WSACC Muddy Creek WWTP Speculative Limits — QUAL2E Model Simulation
NPDES Permit Number: NCO081621
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 MGD discharge with a monthly average BOD limit of 5 mIL/1
and a monthly averaep ammonia limit of 1 mg/1 wi) have minor impacts on the DO levels in the
river, but will not lower the levels below 5 mg/l. Although the model results indicate that

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 Creek
WWTP discharge. Iftl€t i &xcn; ,of the -Muddy Creep WWTP, the permit should'
contain the requirement�of at le weekly monitoring of Dd" oncentrations at this station.
y �r p red c r r , j4j �. Therefore, any an
should not have any further impact on the turbidity in the Rocky River.
As part 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.
W

NC DWQ YADKIN - PEE DEE RIVER BASIN PLAN Rocky River HUC 03040105 2008
N
Legend
Monitoring Stations
�^ Fish
6 Ambient
W Benthos
NPDES Non Discharge Permits
o Major
® Minor
NPDES Discharger Permits
e Major
A Minor
Aquatic Life Rating
Impaired
No Data
Not Rated
�f Supporting
Primary Roads
Municipality Boundary
County Boundary
C:5 8-Digit HUC Boundary
m �-1, C
Yadkin - Pee Dee River Basin
Rocky River and Lynches River Watersheds
8-Digit HUC 03040105 and 03040202
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Basinwide Planning Unit
July, 2008
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muddy creek
Subject: muddy creek
From: Pam Behm <[e-mail]>
Date: Fri, 16 Nov 2007 11:13:25 -0500
To: "[e-mail]" <[e-mail]>
Hi Agyeman-
I got your message, sorry I've been out of the office until today. The same spec
limits should apply for the 1 and 2 MGD discharge requests. Certainly, I would not
recommend anything less stringent than what was recommended for 5 MGD. If you need
me to run the model and graph it, let me know.
thanks,
Pam
1 of 1 11 /160007 12-10 PM

M
M
Figure 1. Rocky River with major tributaries and ambient monitoring stations labeled.
DRAFT

Rocky River QUAL2E Model Predictions for Proposed Expansion of
Muddy Creek WWTP from 0.3 MGD to 5 MGD
7.5
7.0
6.5
i
6.0
E
0
5.5
5.0
4.5
Rocky Regional Muddy Creek Long Creek
VWVTP VWVTP
4.0
0 4
8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72
river mile
-Muddy Cr WWTP at 5 MGD Current Permitted Load DO Standard
Figure 2. Rocky River (Dye Branch to Norwood) QUAL2E Model Predictions of Dissolved Oxygen (mg/L) for Proposed Expansion
of Muddy Creek WWTP from 0.3 to 5.0 MGD.
DRAFT

Dissolved Oxygen (mg/L) at Station Q7330000
16
14 — -
12 -
10 - - ---- -- - - -- - --
E
0
6
4
2
T- T- N M M U') co
O � O I N O 10N co
e- O CO N O CO N r' P-
o O O O T O O T O
Date
Figure 3. Dissolved Oxygen Concentrations at Station Q7330000 (Rocky Riv at SR2420 NR Davidson).
1)n
DO (mg/L)
15
10
{
pl
I 1- = 1- 1- 4 1- 1- 6 1- ` 1- 1- 9 1- 10 1- 11 1- 1_' 1-
6 obs. 6 obs. ti obs. 6 obs. 6 obs. 6 obs. 6 obs. 6 obs. : obs. 6 cabs. 6 obs. 6 tabs.
Figure 4. Monthly distribution of DO concentrations for Station Q7330000.
DRAFT
5

Dissolved Oxygen (mg/L) at Station Q8210000
16
14 --
12 -
as 1 0
E
O 8 — ---
W JA V
4
2
T T- N N co M M 1q, It to 0
O O O O O O O O O O O O
w LO N CO L O f- et
O N I- N CC N
CO T-
T-
Date
Figure 5. Dissolved Oxygen Concentrations at Station Q8210000 (Rocky Riv at US601 NR Concord).
20
DO (mg/L)
15
10
0 0 0 , i * * *
01 1
1- 4 1- 1- F 1- _ 1- 1- 9 1- 10 1- 11 1- 1? 1-
obs. obs. 4 obs. if 0bS. 5 obs. obs. 5 obs- ; obs. 4 obs. 4 obs. 4 obs. 4 obs.
Figure 6. Monthly distribution of DO concentrations for Station Q8210000.
DRAFT
on

Dissolved Oxygen (mg/L) at Station Q8355000
16
14
12
--
— —
E
10
-
- -- -----
O
0
4-
2
O O
O O
N N M ct
O O O O O O
LO
CID
Co O
CID O
I�
CO IC`
0 O I- O Co
N Q 1O O
M
N
00 0
Q CO
O
O O
0 e- O Co N O
O O O O O
Co
O
N
O
Date
Figure 7. Dissolved Oxygen Concentrations at Station Q8355000 (Rocky Riv at SR1114 NR Midland).
-�0
DO (mg/L)
15
10
0
1- 1- 51- 6 1- 10 1- 11 1- 12 1-
obs. 5 obs. ? cabs. obs. 14 obs. 14 obs. 14 obs. 14 obs. 14 obs. ? obs. - obs. obs-
Figure 8. Monthly distribution of DO concentrations for Station Q8355000.
DRAFT 7

Dissolved Oxygen (mg/L) at Station Q8385000
16
14
12
10 -
E
O 8 --
4-
2
O O T— N N M CO C0
CO OO 10 10 `O 10 OO CO O OO 10
C to O fl - O C0 M 00
O N N (0 N N N
L O O CO N
Date
Figure 9. Dissolved Oxygen Concentrations at Station Q8385000 (Rocky Riv at SR1606 NR Monroe).
20
DO (mg/L)
15
10
4z
01 1
1- 4 - 5 1- E 1- _ 1- ^ 1- 9 1- 10 1- 11 l- 1' 1-
obs. ' obs. , obs. o11s. 14 obs. 14 obs. 14 obs. 14 obs. 14 obi. 7 obs. - obs. , obs.
Figure 10. Monthly distribution of DO concentrations for Station Q8385000.
DRAFT

Dissolved Oxygen (mg/L) at Station Q9120000
16
14
- -- —
12
-
-- - ----------- -----
10
--
E
0
6
4
-
2
O O r N N M `� d' LO O (0
O O O CID CID CID O O O O O
Il- to O M 00 U')
O O O O O O O r O O
Date
Figure 11. Dissolved Oxygen Concentrations at Station Q9120000 (Rocky Riv at SR 1935 NR Norwood).
00 (mg/t)
15
10
0
1- 4 1- 1- 6 1- - 1- 1- 9 1-1-
6 obs. 6 obs. 6 obs. obs. , obs. _ obs. 7 obs. , obi. 6 obs. ' obs. - obs. ^ obs,
Figure 12. Monthly distribution of DO concentrations for Station Q9120000.
DRAFT 9

e4**,McKIM&CREED
September 18, 2007
Susan A. Wilson, P.E.
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
i
SEP 2 0 2007 Lo
DENR - WATER QUALITY j
POINT SOURCE BRANCH J
E N G I N E E R S
S U R V E Y O R .S
P L A N N E R S
M&C 02000-0013
RE: Speculative Waste Limits Request for Expansion of Existing WSACC
Muddy Creek WWTP, Cabarrus County, NPDES Permit NCO081621
Dear Ms. Wilson:
On July 10, 2007, representatives from McKim & Creed met with NCDENR
DWQ, Water and Sewer Authority of Cabarrus County (WSACC), and Union
County officials for an evaluation meeting regarding the aforementioned plant.
The meeting discussed the current status of the basin itself and more specifically
the Muddy Creek and Rocky River Waste Water Treatment Plants. Both plants
discharge into the Rocky River classed C by DWQ. The discharge locations are
in subbasin 03-07-12 of the Yadkin River Basin.
The core of the discussions explored the potential for future expansions and
associated permitting, as well as long range planning for the area to develop a
water management model that works toward eliminating water quality and
source issues in the region.
Efforts are currently underway to expand the Muddy Creek Plant from the
current 75,000 gpd capacity to the existing permitted discharge flow of 300,000
gpd. The Rocky River Plant (NPDES Permit NC0036269) has a permitted
discharge flow of 34 MGD, which is estimated to be sufficient through 2015. The
200 M a c K e n a n Court current effluent limits for each plant are attached.
Cary, NC 2 7 5 1 1 It is estimated that Cabarrus County waste water flows at the Muddy Creek
plant may approach up to 5 MGD in the next twenty year planning period.
Although current discussions are being held between WSACC, Union, and
91 9.233.8091
Fax [phone]
www.mckimcreed.com,

Susan A. Wilson
September 18, 2007
Page 2 of 2
Stanly Counties pertaining to the possibilities of reuse customers these
alternatives are not concrete as of yet.
McKim & Creed, on behalf of WSACC, thus requests speculative effluent limits
for the Muddy Creek plant for up to 5 MGD. Since the increase to 5 MGD will be
progressive over time it would be beneficial to phase the effluent limits to the
increase of flow. Thus we are requesting incremental speculative effluent limits
at 1 MGD, 2 MGD, and 5 MGD. If possible we would also like to request a
speculative maximum discharge that may be permissible assuming that the plant
is upgraded to best practical technology for BOD and Ammonia removal.
As discussed in the meeting in July, it is understood that the speculative limits
cannot be issued without updating the existing the dissolved oxygen model for
the Rocky River. Thus WSACC is requesting that the NPDES Unit revisit the
river model and provide new speculative limits for the Muddy Creek plant as
noted above. At the July 10 meeting, the concept of a bubble permit with the
Rocky River plant was also discussed. WSACC is interested in discussing this
with you in more detail if preliminary model results show that this approach
would allow greater flexibility in permitting these increased flows.
Thank you for your time and consideration. If you have any further questions do
not hesitate to contact me or Tim Baldwin at (919)-233-8091.
Sincerely,
McKIM & CREED, P.A.
Keith E. Lane, PE
Project Manager
Enclosures: Site Location Maps, Current NPDES Limits
cc: Van Rowell — WSACC
Tim Baldwin, Bob Rubin — McKim & Creed
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Longitude: 35 12 32
Latitude:80'29'27"
Receiving Stream: Rocky River
Stream Class: C
Drainage Basin: Yadkin
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Permit Capacity 34 MGD,Jr W l
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W W rP Muddy Creek WWTP
V w rP` Rocky River WWTP
QCounty Boundary
Muddy Creek and Rocky River
WWTP Locations
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WSACC Muddy Creek WWTP
NPDES Permit NC0081621
Effluent Limitations and Monitoring Requirements (0.30 MGD)
Effluent
Characteristics
Limits
Monito ing Requirements
Monthly
Weekly
Daily
Measurement
Sample
Sample
Average
Average
Maximum
Frequency
Type
Location
Influent or
Flow
.075 MGD
Continuous
Recording
Effluent
BOD, 5-day (20°C) (April
Influent or
1- October 31)
10.0 m /L
15.0 m /L
3/Week
Composite
Effluent
BOD, 5-day (20°C)
Influent or
november 1- March 31
20.0 m /L
30.0 m /L
3/Week
Composite
Effluent
Total Suspended
Influent or
Residue
30.0 m /L
45.0 m /L
3/Week
Composite
Effluent
NH3 as N (April 1-
October 31)
4.0 m /L
12.0 m /L
3/Week
Composite
Effluent
NH3 as N (November 1-
March 31)
8.0 m /L
24.0 m .L
3/Week
Composite
Effluent
Effluent,
Upstream &
Dissolved Oxygen
3/Week
Grab
Downstream
Fecal Coliform
400/100
(geometric mean
200/100 ml
ml
3/Week
Grab
Effluent
Total Residual Chlorine
28 /L
3/Week
Grab
Effluent
Effluent,
Upstream &
Temperature C°
3/Week
Grab
Downstream
pH
3/Week
Grab
Effluent

Rocky River WWTP
NPDES Permit NCO036269
Effluent Limitations and Monitoring Requirements (34 MGD)
Effluent
Characteristics
Limits
Monitoring Requirements
Monthly
Weekly
Daily
Measurement
Sample
Sample
Average
Average
Maximum
Frequency
Type
Location
Influent or
Flow
34 MGD
Continuous
Recording
Effluent
CBOD, 5-day (20°C)
Influent or
(April 1- October 31)
10.0 m /L
25. m /L
Daily
Composite
Effluent
CBOD, 5-day (20°C)
Influent or
november 1- March 31
20.0 m /L
35 m /L
Daijy
Composite
Effluent
Influent or
Total Suspended Solids
30.0 m /L
45.0 m /L
Daily
Composite
Effluent
NH3 as N (April 1-
October 31)
2.0 m /L
6.0 m /L
Daily
Composite
Effluent
NH3 as N (November 1-
March 31)
4.0 m /L
12.0 mg. L
Daily
Composite
Effluent
Effluent,
Upstream &
Dissolved Oxygen
Daily
Grab
Downstream
Fecal Coliform
400/100
(geometric mean
200/100 ml
ml
Daily
Grab
Effluent
Total Residual Chlorine
25 /L
Daily
Grab
Effluent
Effluent,
Upstream &
Temperature ( C°)
3/Week
Grab
Downstream
H
3/Week
Grab
Effluent