NC0020389_Speculative Limits_20031105

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Michael F. Easley, Governor
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State of North Carolina
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William G. Ross, Jr., Secretary
Department of Environment and Natural Resources
Alan W. Klimek, P.E., Director
Division of Water Quality
November 5, 2003
Keith R. Langdon, Town Manager
Town of Benson
P.O. Box 69
303 East Church Street
Benson, North Carolina 27504
Subject: Speculative Effluent Limits
Town of Benson WWTP
NPDES Permit NCO020389
Johnston County
Dear Mr. Langdon:
This letter is in response to your request for speculative effluent limits for a proposed expansion to
1.9 MGD at the Town of Benson WVVTP. Currently, this facility has limit of 1.5 MGD.
Receiving Stream. This facility discharges to the Hannah Creek in the Neuse River Basin. The Creek
is classified C-Nutrient Sensitive Waters and is slow moving and swamp -like in the vicinity of the
discharge. Upper Hannah Creek, which receives the Benson WWTP discharge, is currently impaired
due to low dissolved oxygen (D.O.) readings. The July 2002 Basinwide Water Quality Plan
recommends that the Division work with Benson to determine the cause of the low D.O. levels.
Speculative Limits. Speculative effluent limits for the proposed discharge of 1.9 MGD to the
Hannah Creek are presented in Attachment A(1.) The speculative limits were developed based on
our review of the Basinwide Plan and current water quality conditions in Neuse River Basin. The
nitrogen limit is consistent with the allocation allowed in the TMDL and in the new Nutrient
Sensitive Waters Management Strategy (15A NCAC 02B.0234). The BOD and ammonia limits are
based on the DWQ policy for new and expanding facilities. 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 modification request.
Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an
NPDES permit modification for expansion to 1.9 MGD 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 City's proposed discharge. In accordance with the North Carolina General
Statutes, the 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
North Carolina Division of Water Quality [phone]
1617 Mail Service Center FAX [phone]
Raleigh, North Carolina 27699-1617 On the Internet at http://h2o.enr.state.nc.us/

Speculative Limits Letter
NCO020389
Page 2 of 2
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.
Should you have any questions about these speculative limits or NPDES permitting requirements,
please feel free to contact Sergei Chernikov at [phone], extension 594.
Sincerely,
Lj
David A. Goodrich
Supervisor, NPDES Unit
Attachments:
A (1.) Effluent limitations and Monitoring Requirements -Speculative
Engineering Alternative Analysis Guidance Document
cc: US Fish and Wildlife Service, Ecological Services,
PO Box 33726,
Raleigh, NC 27636-3726
Attn: Sara Myers
NC WRC, Inland Fisheries,
1721 Mail Service Center,
Raleigh, NC, 27699-1721
Attn: Fred Harris
The Wooten Company
120 N. Boylan Avenue
Raleigh, NC 27603
Attn: Ford Chambliss, P.E.
Raleigh Regional Office
Central Files
NPDES Permit File, NCO020389
N

NCO020389
A. (1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS -Speculative
EFFLUENT
CHARACTERISTICS
LIMITS
MONITORING
REQUIREMENTS
Monthly
Average
Weekly
Average
Daily
Maximum
Measurement
Frequency
Sample.
Type
Sample
Lo•cation�
Flow
1.9 1\IGD
Continuous
Recording
I or E
BOD, 5 day (200C)2 [April 1 —
October 311
5.0 mg/L
75 mg/L
Daily
Composite
I & E
BOD, 5 day (201C)2 [November 1 —
March 31
10.0 mg/L
15.0 mg/L
Daily
Composite
I & E
Total Suspended Solids
30.0 mg/L
45.0 mg/L
Daily
Composite
I & E
NH3 as N [April 1 — October 311
1.0 m /L
3.0 m /L
Daily
Composite
E
NH3 as N [November 1 — March 311
2.0 m /L
6.0 m /L
Daily
Composite
E
Dissolved Oxy&n3
Daily
Grab
E
Fecal Coliform (geometric mean)
200/100 mL
400/100 mL
Daily
Grab
E
Total Residual Chlorine
17 µg/L
Daily
Grab
E
pH4
6-9 s.u. ..
Daily
Grab
E
Total Phosphorus'
.
2.0 mg/L (Quarterly Average)
Weekly
Composite
E
Chronic ToXi City6
I I
I Quarterly
Composite
E
Total Nitrogen
33,790 lb./year
I Annualy
Calculated
E
Footnotes:
1. Sample locations: E — Effluent, I — Influent, U — Upstream at NCSR 1211, D — Downstream at (1) NCSR 1711 and
(2) I-95 culvert. Stream samples shall be grab samples and shall be collected 3/Week during June — September and
1 /Week during the remaining months of the year. Instream monitoring is provisionally waived in light of the
Permittee's participation in the Lower Neuse Basin Association. Instream monitoring shall be conducted as
stated in this permit should the Permittee end its participation in the Association. Please also see Special
Condition A.(S.) for upstream monitoring.
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 dissolved oxygen effluent 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 and shall be monitored daily at the
effluent by grab sample.
5. The quarterly average for total phosphorus shall be the average of composite samples collected weekly during the
calendar quarter Qanuary-March, April June, July -September, October -December). This limit applies for members of
Neuse River Compliance Association. Non-members are subject to a more stringent limit of 1 mg/L.
6. Chronic Toxicity (Ceriodaphnia dubia) P/F at 90%: January, April, July, and October [see A. (2)]. Toxicity monitoring
shall coincide with metals monitoring.
There shall be no discharge of floating solids or visible foam in other than trace amounts.