FergussonRoad_UTCatCr_Macon_NCWRCComments

North Carolina Wildlife Resources Commission
Cameron Ingram, Executive Director

Mailing Address: Habitat Conservation • 1721 Mail Service Center • Raleigh, NC 27699-1721
Telephone: [phone] • Fax: [phone]
June 3, 2024

Ms. Shannon Healy
U.S. Army Corps of Engineers, Regulatory Branch
151 Patton Avenue, Room 208
Asheville, North Carolina 28801-5006

SUBJECT: Fergusson Road
UT Cat Creek, Macon County

Dear Ms. Healy:

Biologists with the North Carolina Wildlife Resources Commission (NCWRC) reviewed an
application that documents after-the-fact impacts to 240 ft of an unnamed tributary (UT) to Cat
Creek in Macon County. Our comments on this application are offered for your consideration
under provisions of the Clean Water Act of 1977 (33 U.S.C. 466 et. seq.) and Fish and Wildlife
Coordination Act (48 Stat. 401, as amended; 16 U.S.C. 661-667d).

Wild trout reproduction would not have been impacted by project activities, and a trout
moratorium would not have applied. However, Cat Creek is part of the Little Tennessee River
(Upper) Aquatic Habitat natural area, rated Very High by the NC Natural Heritage Program due
to its ecological importance and the richness of rare species it supports, such as the Smoky Dace
(Clinostomus sp., NC Significantly Rare).

The application accounts for after-the-fact impacts to a stream involving three high density
polyethylene (HDPE) culverts and three in-line ponds. The application describes intentions to
install low flow orifaces within each pond. It is unknown if the design will provide permanent
flows.

NCWRC does not support the construction of in-line ponds, as they serve as barriers to fish and
other aquatic organisms, artificially warm downstream waters in the warm season, and alter food
web dynamics in the downstream stream. We recommend that the ponds be removed and the
stream and associated riparian area restored.

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In addition, we recommend against using HDPE material for culverts, as this slick material is
less likely to hold stream substrate and provide for movement of aquatic organisms like fish and
salamanders.

Thank you for the opportunity to review and comment on this project. Please contact me at
[phone] if you have any questions about these comments.

Sincerely,

Andrea Leslie
Mountain Region Coordinator, Habitat Conservation Program

ec: Jennifer Robertson, Atlas Environmental, Inc.
Joey Winston, NC Division of Water Resources

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How to reduce the thermal impacts of pond outflows: Thermal impacts caused by ponds that
continuously release surface water into streams can be reduced in ponds that are equipped with a
standpipe to regulate water levels. The installation of a bottom drawoff device (see diagram)
over the existing standpipe helps reduce the temperature of water released by the pond by
siphoning off the cooler water found near the pond bottom. Furthermore, a bottom drawoff also
helps prevent fish kills in ponds by removing the stagnant, low oxygen water from the pond
bottom. The drawoff pipe needs to be large enough in diameter so that the cross-sectional area
of the space between the two pipes is greater than the cross-sectional area of the drainpipe. The
pipe needs to be long enough to reach into the cooler/deeper waters of the pond, and should leave
at least a couple feet of clearance above the bottom to avoid future interference from sediment
accumulation. The drawoff pipe should be constructed of a relatively light but rigid material
(aluminum is best). Heavy pipes are difficult to mount and put extra strain on the standpipe that
could eventually cause its failure. If the drawoff pipe material isn’t sufficiently rigid it may
collapse under the suction pressure. Typically drawoff pipes are mounted by inserting two
crossbars through the pipe 6-12 inches from the top end, then putting the drawoff pipe over the
standpipe so that these crossbars rest on the top of the standpipe. Three bolts or pins can be
inserted into the pipe several feet down from the top to serve as spacers that will keep the
drawoff pipe vertical and centered on the standpipe.

12’’
18’’
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Bottom water withdrawal devices do have their limitations. Ponds that are very shallow and/or
small may not benefit since the water temperatures near the bottom and at the surface will be
more similar. Also, if the outflow from a pond is going directly into a stream, then the water
should be aerated by routing it to splash onto rocks or other hard, jagged surfaces as it re-enters
the stream.