NC0026913_speculative limits_19940616

State of North Carolina
Department of Environment,
Health and Natural Resources
Division of Environmental Management
James B. Hunt, Jr., Governor
Jonathan B. Howes, Secretary
A. Preston Howard, Jr., P.E., Director
June 16, 1994
117,1A
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Mr. Tom Douglas, Town Manager
Town of Sparta
P.O. Box 99
Sparta, N.C. 28675
Subject: Town of Sparta Wastewater Treatment Plant Expansion
NPDES Permit No. NC0026913
Alleghany County
Dear Mr. Douglas:
Your request for speculative effluent limits for the proposed expansion of the Sparta
WWTP to 0.95 MGD has been completed by the staff of the Technical Support Branch. In
order to receive final permit limits, a formal application will have to be submitted to the
Division's Water Quality Permits and Engineering Unit.
Based on available information, the tentative limits for conventional pollutants are:
Summer Winter
Wasteflow (MGD) 0.95 0.95
BOD5 (mg/1) 30 30
NH3-N (mg/1) 6 18
TSS (mg/1) 30 30
Fecal Coliform (#/100ni1) 200 200
pH (SU) 6-9 6-9
Chlorine (1.tg/1) 28 28
It should be noted that the tentative NH3-N limits are based on protecting the Little
River against instream toxicity. North Carolina is evaluating all NPDES dischargers for
ammonia toxicity following the Environmental Protection Agency (EPA) guidance to
protect the waters for an instream criteria of 1 mg/1 in the summer and 1.8 mg/1 in the
winter, under 7Q10 flow conditions.
The Division of Environmental Management (DEM) is now recommending chlorine
limits and dechlorination for all new or expanding dischargers proposing the use of
chlorine for disinfection. An acceptable level of chlorine in your effluent is 28 µg/1 to
ensure protection against acute toxicity. The process of chlorination/dechlorination or an
alternate form of disinfection, such as ultraviolet radiation, should allow the facility to
comply with the total residual chlorine limit.
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
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Letter to Tom Douglas
page 2
The instream waste concentration (IWC) at the expanded flow of 0.95 MGD is
13%. A chronic toxicity testing requirement with quarterly monitoring will remain a
condition of the NPDES permit. A complete evaluation of limits and monitoring
requirements for metals and other toxicants will have to be addressed at the time of formal
NPDES application. However, based on industrial information provided to the Division
during the Town's request for a Special Order of Consent, tentative effluent limits for the
following constituents will more than likely be recommended:
Cadmium 15 µg/1
Cyanide 39 µg/1
Mercury 0.09 µg/1
Effluent monitoring and/or limits for chromium, copper,nickel, lead, zinc, arsenic and
silver may also be recommended.
DEM is implementing a basinwide water quality management initiative. Our
schedule for the New River Basin is set for 1995. The plan will attempt to address all
sources of point and nonpoint pollutants where deemed necessary to protect or restore
water quality standards. In addressing interaction of sources, wasteload allocations may be
affected. Those facilities that already have committed to high levels of treatment technology
are least likely to be affected.
This information should provide some assistance in your planning endeavors.
Final NPDES effluent limitations will be determined after a formal permit application has
been submitted to the Division. If there are any additional questions concerning this matter,
please feel free to contact Ruth Swanek or Jackie Nowell of my staff at [phone].
rely,
onald L. S
Assistant Ch f for Tec 'cal Support
cc: Steve Mauney
Bob Lyons,
Central Files
WLA File