20070410 Ver 1_Other Agency Correspondence_20070410

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North Carolina
Michael F. Easley, Governor
Memorandum
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NCDENR
Department of Environment and
Division of Water Resources
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Natural Resources
William G. Ross Jr., Secretary
John Morris, Director
April 5, 2007 4~~ ~~ ~"~fe r~
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To: Cyndi Karoly, 401 Unit Supervisor ~'~~%~ - w~T~e ct,.;.ti~ITY
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From: John Sutherland, Water Projects Section Chief
RE: Lake Townsend/City of Greensboro 401 W r Quality Certification
(Corps Act. ID# SAW-2007-00895-241)
The Division of Water Resources (DWR) is providing the following comments for consideration
during the drafting of a state 401 water quality certification for the construction of a replacement
dam downstream of the existing dam impounding Lake Townsend, a water supply reservoir for
the City of Greensboro.
The current flow release requirement from Lake Townsend was established in 1992, during
review of the environmental assessment for the City's water treatment plant expansion and the
required release is 7 cfs at full pool and 2 cfs at any elevation below full pool. The City typically
maintains the impoundment below full pool. DWR determined the normal release amount of 7
cfs based on a field study of instream flow needs conducted downstream on Reedy Fork. In
1992, DWR did not pursue its authority to request construction of a specific release mechanism
and a flow requirement of 7 cfs from the dam because leakage from the dam structure exceeded
the flow requirement most of the time. DWR and the Wildlife Resources Commission agreed to
allow the City to meet the 2 cfs requirement from their filter backwash discharge at the water
treatment plant just below the dam.
There is a reasonable expectation that the new construction will significantly reduce or eliminate
the leakage that now contributes to downstream flow from the existing dam.
As a condition for concurrence with the Finding of No Significant Impact (FONSI) associated
with the environmental assessment to replace the dam, DWR received an agreement from the
City to develop atiered-release strategy from the dam prior to its completion. DWR will also
need to discuss with the City the source of the release, especially when Lake Townsend is
operating within its lowest tier.
One
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Phone; 919-733-40641 FAX: [phone] Internet: www.ncwater.org [l
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DWR memorandum regarding Lake Townsend 401
Apri15, 2007 -Page 2
DWR requests that the Division of Water Quality include the following provisions within the
401 water quality certification:
• The new dam will maintain minimum flow requirements based on athree-tiered release
schedule tied to the amount of usable storage remaining in the City's combined
impoundments on Reedy Fork.
• Reductions in the minimum release will be accompanied by aten-percent reduction in
withdrawal from the Reedy Fork source of water supply for each tiered reduction in
downstream release.
• The tiered release developed in consultation with the City of Greensboro will not exceed
7 cfs, when in the top tier, and not be less than the 7Q10, when in the bottom tier. The
extent to which filter backwash water can be counted as part of the tiered flow release
targets will be determined during discussions with the City of Greensboro.
If you have any questions regarding these recommendations, please contact Fred Tarver, DWR at
919/715-5442 or Fred.Tarver(a~ncmail.net.
cc: Fred Tarver and Woody Yonts -DWR
Shari Bryant - WRC