NC0043532_Speculative Limits_20050210

NPDES DOCUMENT SCANNING COVER SHEET
NPDES Permit:
NC0043532
West Stanly / Oakboro WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
February 10, 2005
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Michael F. Easley
Governor
N
The Honorable Joyce Little, Mayor
Town of Oakboro
P.O. Box 610
Oakboro, North Carolina 28129
Dear Mayor Little:
William G. Ross, Jr., Secretary
North Carolina Department of Environment and Natural Resources
Alan W. Klimek, P.E., Director
Division of Water Quality
February 10, 2005
Subject: Speculative Limits for Oakboro WWTP
NPDES Permit No. NC0043532
Stanly County
This letter is in response to the request for speculative effluent limits for the expanded Oakboro
WWTP. Wastewater flows of 1.2 and 3.0 MGD were targeted for discharge from Outfall 002 into the
Rocky River in the Yadkin -Pee Dee River Basin.
Please be advised that response to this request does not guarantee that the Division will issue an
NPDES permit to discharge treated wastewater into these receiving waters. The Town of Oakboro will
be required to complete an Engineering Alternatives Analysis (EAA) that must be submitted with the
application for the NPDES permit. The EAA should contain a clear and strong justification for the
expanded facility and an analysis of potential alternatives, which should include a thorough evaluation
of non -discharge alternatives. Nondischarge alternatives, such as spray irrigation, water conservation, or
connection to a regional treatment and disposal system, are considered to be environmentally preferable
to a surface water discharge. In accordance with the North Carolina General Statutes, the most
practicable waste treatment and disposal alternative with the least adverse impact on the environment is
required to be implemented. (A copy of the EAA guidance is attached with this letter).
This segment of Rocky River has a stream classification of C. The best usage of these waters is
aquatic life propagation and maintenance of biological integrity (including fishing and fish), wildlife,
secondary recreation, and agriculture. Using available information, the discharge point has an estimated
drainage area of 965 square miles, with an average flow of 920 cfs, a summer 7Q10 of 29 cfs and a
winter 7Q10 of 51 cfs. Please be advised that these are historical flows, however it is preferable that the
Town of Oakboro request updated flow estimations from the United States Geological Survey (USGS)
to ensure accuracy. You may contact J. Curtis Weaver of USGS at 919-571-4043 concerning your
request.
The tentative effluent limits for oxygen -consuming constituents for the Oakboro WWTP
discharge at the flows of 1.2 and 3.0 MGD are included on the attached effluent sheets. The speculative
limits are based on the results of a QUAL2E model application on the Rocky River and Mallard Creek
N. C. Division of Water Quality / NPDES Unit
1617 Mail Service Center, Raleigh, NC 27699-1617
Internet: h2o.enr.state.nc.us
Phone: [phone]
fax: [phone]
DENR Customer Service Center.1 800 623.7748

in the Yadkin River Basin. It is recommended that any new or expanding discharge in the lower
watersheds of the Rocky River should receive a total ultimate BOD limit of 32 mg/1 or less, equivalent
to 10 mg/1 BOD5 and 4 mg/1 NH3 for typical domestic discharges. This level of treatment will protect
the dissolved oxygen (DO) standard as well as preventing any one discharge from exhausting 100% of
the available assimilative capacity of the river. Please be advised that by the time of Oakboro's request
for expansion to 3.0 MGD, the Division may have made improvements to the model, and more stringent
limits than 10 mg/1 BOD5 and 4 mg/l NH3 may apply. Should the Town ultimately decide to expand
above 1.2 MGD ( and flows above 1.2 MGD are justified), please contact this office prior to proceeding
forward with the EAA. Also, the Town should be aware that expansions greater than 0.5 MGD will
require an environmental assessment (EA).
The Division of Water Quality is requiring chlorine limits for all new or expanding dischargers
proposing the use of chlorine for disinfection. The process of chlorination/dechlorination or an alternate
form of disinfection, such as ultraviolet radiation, should allow the facility to comply with this
requirement. Additionally, upon formal permit application, if there are industrial wastewater
contributors to your plant, an evaluation of limits and monitoring requirements for metals and other
toxicants will be done.
Final NPDES effluent limitations will be determined if a permit application is submitted
to the Division. If there are any additional questions concerning this matter, please feel free to
contact Jackie Nowell of my staff' at [phone] ext. 512.
Respectfully,
Susan A. Wilson, Acting Supervisor
NPDES Western Program
Attachments
cc: Larry Branch, Town of Oakboro P.O. Box 610 Oakboro NC 28219
Allen Wahab, The Wooten Company 120 North Boylan Avenue Raleigh NC 27603-1423
Mooresville Regional Office/Rex Gleason
Michelle Woolfolk/Modeling/TMDL Unit
Bobby Blowe, Construction Grants
Central Files
NPDES Permit File

A. SPECULATIVE EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS -
OAKBORO WWTP at 1.2 MGD
During the period beginning on the effective date of the permit and lasting until expiration, the
Permittee is authorized to discharge from outfall 002 (Rocky River). Such discharges shall be
limited and monitored by the Permittee as specified below:
EFFLUENT
CHARACTERISTICS
LIMITS
MONITORING REQUIREMENTS
Monthly
Average
Weekly
Average
Daily
Maximum
Measurement
Frequency
Sample
Type
Sample Location1
Flow '
1.2 MGD '
Continuous
Recording
Influent or Effluent
BOD, 5-day, 204C2
10.0 mg/L
15.0 mg/L
3Mreek
Composite
Influent, Effluent
Total Suspended Residue 2
30.0 mg/L
45.0 mg/L
3/Week
Composite
Influent, Effluent
NH3 as N
4.0 mg/L
12.0 mg/L
3Mleek
Composite
Effluent
Fecal Coliform
(geometric mean)
,
200 / 100 ml
400 / 100 ml
3/Week
Grab
Effluent
Dissolved 0xygen3
3Mleek
Grab
Effluent, Upstream,
Downstream
pH4
3Mfeek
Grab
Effluent
Total Residual Chlorines
28 Ng/L
3Meek
Grab
Effluent
Total Nitrogen
(NO2+NO3+TKN)
Monthly
Composite
Effluent
Total Phosphorus
Monthly
Composite
Effluent
Temperature, °C
3Mleek
Grab
_
Effluent , Upstream,
Downstream
Chronic Toxicity
Quarterly
Composite
Effluent
Notes:
1. Influent, Effluent, Upstream, Downstream
2. The monthly average effluent BOD5 and Total Suspended Residue concentrations shall not exceed 15% of the
respective influent value (85% removal).
3. The daily average effluent dissolved oxygen concentration shall not be less than 6.0 mg/L.
4. The pH shall not be less than 6.0 standard units nor greater than 9.0 standard units.
5. Monitoring requirement and limit applies only if chlorine is added for disinfection.
6. Chronic Toxicity (Ceriodaphnia) P/F at 6%; Months to be determined
There shall be no discharge of floating solids or visible foam in other than trace

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Oakboro WWTP w/ 3.0
MGD expansion
Residual Chlorine
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (UG/L)
UPS BACKGROUND LEVEL (1
IWC (%)
Allowable Concentration (ugi
Fecal Limit
Ratio of 6.2 :1
29
3
4.65
17.0
0
13.82
123.02
Ammonia as NH3
(summer)
7Q10 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL
IWC (%)
Allowable Concentration (m
Ammonia as NH3
(winter)
29
3
4.65
1.0
0.22
13.82
5.86
7Q10 (CFS)
200/100m1 DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL
IWC (%)
Allowable Concentration (m
3
4.65
1.8
0.22
8.36
19.13
11/18/2004

Oakboro WWTP w/ 1.2 MGD expansion
Residual Chlorine
7010 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (UG/L)
UPS BACKGROUND LEVEL (l
IWC (%)
Allowable Concentration (ug)
Fecal Limit
Ratio of 15.6 :1
29
1.2
1.86
17.0
0
6.03
282.05
Ammonia as NH3
(summer)
7010 (CFS)
DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL
IWC (%)
Allowable Concentration (m
Ammonia as NH3
(winter)
7010 (CFS)
200/100m1 DESIGN FLOW (MGD)
DESIGN FLOW (CFS)
STREAM STD (MG/L)
UPS BACKGROUND LEVEL
IWC (%)
Allowable Concentration (m
29
1.2
1.86
1.0
0.22
6.03
13.16
51
1.2
1.86
1.8
0.22
3.52
45.12
11/18/2004

dpix /1/Zi/cy
THE
WOOTEN
COMPANY
ENGINEERING
PLANNING
ARCHITECTURE
rtr4,t-tt,{ .;=/'N6y./: - Z cl
.416
October 26, 2004
Mr. Dave Goodrich
NPDES Unit
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: Speculative Limits Request
Town of Oakboro WWTP '
NPDES Permit No. NC0043532
Stanly County
Dear Mr. Goodrich:
OCT 2 8 2004
DENR - WATER QUALITY
POINT SOURCE BRANCH
On behalf of the Town of Oakboro, this letter is to request speculative limits for a series
of expansions for the Town's wastewater treatment plant. The plant is currently
operating within permitted flow limits. Due to the rapid growth experience in western
Stanly County, influenced in part by Mecklenburg and Cabarrus Counties, the Town is
taking the necessary steps to appropriately allocate treatment capacity as well as plan for
future expansion of the WWTP.
We, therefore, request speculative limits for future expansion of 1.2 mgd, 1.8 mgd, 2.4
mgd and 3.0 mgd: The limits should be provided for Outfall 002 which discharges into
the Rocky River.
If you should have any questions concerning this request, please contact me at 919-828-
0531 or at my email address at [e-mail]. We appreciate your
consideration for this request and look forward to the Division's response.
Sincerely,
THE WOOTEN COMPANY
iffe.loodd-
Allen Wahab, P.E.
AW:sml
120 North Boylan Avenue cc: Larry Branch, Town of Oakboro
Raleigh NC 27603-1423
919.828.0531
fax [phone]