NC0021920_staff comments_20040525

DIVISION OF WATER QUALITY
May 25, 2004
To: Alex Marks
Local Government Assistance Unit
From: Susan A. Wilson, Environmental Enginee-j
NPDES Unit �!
Subject: City of Whiteville - Whitemarsh WWTP
Comments for CDBG Program
NPDES No. NC0021920
Columbus County
I have reviewed portions of the submittal for the City of Whiteville to obtain funding for
wastewater treatment plant improvements under the CDBG Program. The proposed
project includes removal of the existing equalization basin structure and the addition of
a new aeration basin, retrofitting the existing clarifiers and increasing the depth 5 feet,
adding a new aerobic digester and aerated sludge holding tank, adding new influent
pumps, and the addition of standby power, as well as other planned improvements. No
increase in the current design flow of 3.0 MGD is planned with this proposal.
The NPDES Unit has no objections to the proposed improvements and agrees that the
improvements will likely assist in consistent wastewater treatment. The structural
integrity of the existing equalization basin and aeration basin must be corrected.
The NPDES Unit also offers the following comments based on the history of the plant
and potential future impacts:
• Dechlorination is not mentioned as part of the existing treatment scenario. The
City of Whiteville's NPDES permit requires that a total residual chlorine limit of
28 ug/1 must be met. If consistent dechlorination is not currently provided, this
should be considered in the improvement plan. cx,E,-Ds d, c,
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• The NPDES permit was recently reopened (2003) to include a limit for zinc. Due
to the previously high levels of zinc in the effluent, it is possible that zinc, as well
as other metals, is pervasive in the residuals at the plant. The City of Whiteville
should take this opportunity to determine if metals in the sludge are an issue
(and may continue to be an issue with the planned improvements). This
reviewer is unsure if the planned improvements will completely resolve the
metals issues.
It is likely with the reorganization of the Division of Water Quality that the permitting
for the construction/renovation of treatment units (Authorization to Construct, ATC
permits) will be transferred to the Division's Construction Grants and Loans Section.
The City and its consultants should plan for a minimum of 3 months to obtain an ATC
permit.
The City should also be aware that all NPDES permit limits must be maintained during
the construction and renovation of the plant.
cc: Central Files
NPDES Files
WiRO/ Water Quality Section