20170311 Ver 1_WRC Comments_20170419

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� North Carolina Wildlife Resources Commission ��
MEMORANDUM
TO:
FROM:
Gordon Myers, Executive Director
February 15, 2016
Lori Beckwith, NCDOT Regulatory Project Manager
Asheville Regulatory Field Office, USACE
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Marla Chambers, Western NCDOT Coordinator �L�- ��.ct�r�z�.r,:�.
Habitat Conservation Program, NCWRC
SUBJECT: Review of NCDOT's application for Section 404 and 401 permits to replace
Bridge No. 16 over Elk Fork on NC 197, Yancey County, North Carolina.
The North Carolina Department of Transportation has submitted an application to obtain a
Section 404 Permit from the U.S. Army Corps of Engineers and a 401 Water Quality
Certification from the NC Division of Water Resources. Staff biologists with the North Carolina
Wildlife Resources Commission (NCWRC) have reviewed the information provided. These
comments are provided in accardance with the provisions of the state and federal Environmental
Policy Acts (G.S. 113A-lthrough 113-10; 1 NCAC 25 and 42 U.S.C. 4332(2)(c), respectively),
the Clean Water Act of 1977 (33 U.S.C. 466 et seq.) and the Fish and Wildlife Coordination Act
(48 Stat. 401, as amended; 16 U.S.C. 661-667d), as applicable.
The NCDOT proposes to replace Bridge No. 16 over Elk Fork on NC 197 with a two-barrel box
culvert measuring 2@ 8' W x 4' H X 76' L using both barrels for the low flow. The application
indicated the predominantly cobble and boulder stream, approximately 14 feet wide, has a slope
of 7.17% at the project site. Elk Fark is classified as WS-II, Trout, HQW. We are very
concerned that splitting the base flow of the stream may lead to fish and aquatic life passage
issues, increased maintenance activities and costs, and erosional problems on streambanks and
roadway embankment.
Placing the normal flow of a stream into two or more barrels of a culvert alters the flow and
sediment transport patterns that can cause problems, such as over-widening of the channel, mid-
channel bar formation, stream instability, and streambank erosion. While the project site
Mailing Address: Habitat Conservation • 1721 Mail Service Center • Raleigh, NC 27699-1721
Telephone: [phone] • Fax: [phone]

BRIDGE NO. 16 PAGE 2 FEBRUARY 15, 2016
ELK FORK, YANCEY CO.
conditions and substrate make stream instability unlikely, debris accumulation from the mid-
channel culvert wall is a greater concern for this project. A debris jam was removed from the
upstream side of this bridge last week, the morning of a field meeting between USACE, NCDOT
and NCWRC regarding this project. A crutch bent had been placed mid-channel under the
bridge structure and a sizable rain occurred the previous night. We understand that debris
removal activities are a regular maintenance activity at the subject bridge.
The Federal Highway Administration publication "Hydraulic Design of Highway Culverts"
(2012) states "As a minimum, debris accumulation will increase maintenance costs and at the
extreme can lead to increased upstream flooding, potential overtopping and roadway
embankment failure. Another FHWA publication, "Debris Control Structures, Evaluation and
Countermeasures" (2005), characterizes debris accumulation at culvert and bridge structure
openings as a widespread problem that frequently causes unsatisfactory performance and
malfunction. Blockage of a large portion of the waterway opening increases backwater
elevations upstream and increases flow velocity through the contracted opening. These
conditions can cause high drag and hydrostatic forces that can lead to structural failure and
collapse. High velocity flows deflected away from the main channel can cause severe bank
erosion. It also notes that debris jams distort pool-riffle sequences and gravel bar formations and
changes erosional and depositional processes.
Watershed Sciences, in their 2007 "Literature Review of Modern Box Culvert Design", indicated
that multi-cell culverts should not be used in Rosgen Type A streams, due to steep slopes, in
excess of 3%. Use in A or D type streams would likely obstruct fish passage. They also indicate
design considerations for other stream types and that multi-cell systems may not be appropriate
for stream corridors with a significant debris jam potential, due to floodplain cells being highly
susceptible to debris accumulations. We believe the mid-channel obstacle of multiple barrels of
a culvert conveying the stream's base flow will be even more susceptible to debris jams and their
negative effects. The increased flow velocities through a contracted opening, coupled with the
steep slope of the site will likely hinder aquatic life passage for this project.
For these reasons, we recommend a redesign of this bridge replacement project to avoid splitting
the base flow into multiple barrels. The high debris drift nature of the site should be considered
when designing a structure that will maintain natural flow and sediment transport patterns as
much as possible and maintain or improve fish and other aquatic organism passage. We also
provide this information for NCDOT to consider for other bridge replacement projects in the
state.
Thank you for the opportunity to review and comment on this project. If you have any questions
regarding these comments, please contact me at marla.chambers(a�ncwildlife.org or (704) 982-
9181.
cc: Amy Chapman, NCDWR
Kevin Barnett, NCDWR
Andrew Henderson, USFWS
Roger Bryan, NCDOT

BRIDGE NO. 16 PAGE 3 FEBRUARY 15, 2016
ELK FORK, YANCEY CO.
Literature Cited:
FHWA, 2005, "Debris Control Structures, Evaluation and Countermeasures," Hydraulic
Engineering Circular 9, Report FHWA IF-04-016 (J.B. Bradley, D.L. Richards, C.D. Bahner).
FHWA, 2012, "Hydraulic Design of Highway Culverts," Report FHWA-HIF-12-026 Hydraulic
Design Series No. 5, Third Edition, Washington, D.C. (J.D. Schall, P.L. Thompson, S.M. Zerges,
R.T. Kilgore, J.L. Morris).
Watershed Sciences, 2007, "Literature Review of Modern Box Culvert Design" [cited 2016 Feb
15] Available from:
http://urbancreeks.or /�old�site/WildcatWRAP/A�G4_WS_Culvert%20Desi�pdf