NC0037834_approval_19960806

State of North Carolina
Department of Environment,
Health and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Jonathan B. Howes, Secretary
A. Preston Howard, Jr., P.E., Director
August 6, 1996
Thomas W. Griffin
Utilities Superintendent
City of Winston-Salem
P.O. Box 2511
Winston-Salem, North Carolina 27102
Dear Mr. Griffin:
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DBJECT: NPDES Permit # NC0037834
A Archie Elledge WWTP
Winston-Salem Cyanide Study
Forsyth County
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We have completed review of the c .a+<ude'sfudy performed on the influent and effluent at
the Archie Elledge WWTP per the seftl�ement agreement dated March 10, 1995 and NPDES
permit NC0037834 Part III, Special Condition I. The purpose of the study was to examine
the influence of the wastewater -specific matrix effects and determine an appropriate
quantitation level for the measurement of cyanide at the Archie Elledge WWTP effluent.
We concur with the following conclusions of the study:
• Influent Results: The influent sample results showed interference effects throughout
the range of spike sample concentrations. The results indicated a tendency toward false
negatives and poor recovery, but that detection did indicate some presence of cyanide.
• Effluent Results: The interference was documented to a lesser extent in the effluent
samples than influent samples. High variability of the effluent results was shown in the
range of 5 to 15 pg/1 of cyanide. However, the test method produced reliable results at
concentrations greater than 20 µg/1.
Therefore, based on these results, the Division will evaluate the reasonable potential of the
presence of cyanide in the effluent to contribute to a water quality standard violation and
determine compliance with the cyanide limits based on a quantitation level of 20 µg/1. Any
cyanide concentrations in the Archie Elledge WWTP effluent at levels of less than 20 µg/1
will be considered to be zero for purposes of compliance. Future improvements to the
cyanide test method may require a re-evaluation of the 20 µg/1 quantitation level.
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
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Per the February 28th meeting and letter of March 9, 1996 from CH2M Hill, Winston-
Salem will be submitting a final technical memorandum documenting the study results,
including backup information on chain -of -custody forms, spiking documentation and the
laboratory results.
If you have any questions about this letter, please contact Dave Goodrich at 919/733-5083,
extension 517.
Sincerely,
/in- A. Preston oward, Jr_, P.
cc: Stan Webb, City of Winston-Salem
Bill Kreutzberger, CH2M Hill
Steve Mauney, WSRO
William B. Edwards, Water Chemistry Laboratory
Larry Ausley, Aquatic Survey & Toxicology Unit
Perrnits & Engineering Unit
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