NCWRC Comments - Niblick Drive Culvert Replacement

Baker, Caroline D
From: Munzer, Olivia
Sent: Friday, January 13, 2023 6:56 AM
To: [e-mail]
Cc: Saine, Gary; Pitner, Andrew; Stygar, KRYSTYNKA B CIV USARMY CESAW (USA)
Subject: NCWRC Comments - Niblick Drive Culvert Replacement
Mr. McMillan,
Please see the general recommendation below.
a) The culvert must be designed to allow for aquatic life and fish passage. Generally, the culvert or pipe invert should be
buried at least 1 foot below the natural streambed (measured from the natural thalweg depth) unless the slope of the
culvert is greater than 2% due to concerns of headcutting. If multiple barrels are required, barrels other than the base
flow barrel(s) should be placed on or near stream bankfull or floodplain bench elevation (similar to Lyonsfield
design). These should be reconnected to floodplain benches as appropriate. This may be accomplished by utilizing sills
on the upstream and downstream ends to restrict or divert flow to the base flow barrel(s). Silled barrels should be filled
with sediment so as not to entrap wildlife or support mosquito breeding conditions. Sufficient water depth should be
provided in the base flow barrel(s) during low flows to accommodate fish movement. If culverts are longer than 40-50
linear feet, alternating or notched baffles should be installed in a manner that mimics existing stream pattern. This
should enhance aquatic life passage: 1) by depositing sediments in the barrel, 2) by maintaining channel depth and flow
regimes, and 3) by providing resting places for fish and other aquatic organisms. In essence, base flow barrel(s) should
provide a continuum of water depth and channel width without substantial modifications of velocity.
b) If multiple pipes or cells are used, at least one pipe or box should be designed to remain dry during normal flows to
allow for wildlife passage.
c) Culverts or pipes should be situated along the existing channel alignment whenever possible to avoid channel
realignment. Widening the stream channel must be avoided. Stream channel widening at the inlet or outlet end of
structures typically decreases water velocity causing sediment deposition that requires increased maintenance and
disrupts aquatic life passage.
d) Riprap should not be placed in the active thalweg channel or placed in the streambed in a manner that precludes
aquatic life passage. Bioengineering boulders or structures should be professionally designed, sized, and installed.
Please let me know if you have questions,
Thank you.
Olivia Munzer
Western Piedmont Habitat Conservation Coordinator
NC Wildlife Resources Commission
Rogers Depot
1718 NC Hwy 56 W
Creedmoor, NC 27522
Office: 919-707-4056 (note new number)
Cell: 336-269-0074
[e-mail]
www.ncwildlife.org
13 n ISM

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