20151021 Ver 1_B-4792 - Bridge No 4 - NW 14 Permit Application - Polk County_20151112

Carpenter,Kristi
From:Chambers, Marla J
Sent:Thursday, November 12, 2015 3:27 PM
To:Davis, Mark S; 'Lori Beckwith ([e-mail])'
Cc:Deyton, Joshua B; Hill, Mark E; Chapman, Amy; Carpenter,Kristi; Barnett, Kevin;
McHenry, David G
Subject:RE: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County
Follow Up Flag:Follow up
Flag Status:Flagged
The response does not provide sufficient evidence that the current design won’t be a barrier to trout and aquatic life
passage. Replicating the conditions of the existing bridge crossing is not desirable or recommended. The existing bridge
appears to have had the interior bent added as a support, or at least had some significant rehabilitation done. We have
learned a lot since the construction of the bridges that are now being planned for replacement. The goal should be to
correct inferior crossing designs of the past, not to repeat them. In training that I have received, designers should
always go a ways above and below the crossing, beyond the influence of the crossing, to determine the natural
characteristics of the waterway for appropriate design.

It has been my experience in recent years that NCDOT tries to avoid bents or structures within the active channel, for
obvious and important reasons. As pointed out in the response, the stream channel upstream is wider than
downstream of the existing bridge. This may be due to the bottleneck effect of the existing crossing being too narrow
and the opening being too small, backing up the flow and substrate upstream and creating the higher velocities at the
outlet, scouring out a narrower channel downstream, like a hose pipe, over the years. The replacement of this bridge is
the opportunity to improve this situation and correct mistakes of the past.

The Madison Co. example provided in the response seems to illustrate my concerns. It appears this stream is now over-
widened and attempting to narrow itself, as evidenced by the vegetation growing in the channel on the left side (looking
downstream). Plus a mid-channel bar/island is beginning to form at the upstream face of the wall that separates the 2
cells of the culvert. Substrate and debris are beginning to accumulate and vegetation is growing at this mid-channel
structure, showing that splitting the stream flow and altering the natural flow regime is inappropriate.

The natural “bifurcation” of flow around boulders has no similarities to splitting the stream into the confined space of 2
barrels of a box culvert. Also, as evidenced by the Engineering Handbook information that I provided, the length of the
crossing has a significant effect on the ability of fish and other aquatic life to pass through. The proposed culvert is more
than 2.5 times longer than the existing crossing. Replicating the existing crossing dimensions and extending the length
of the crossing does not necessarily maintain the existing level of fish passage.

I’m not sure what to make of the significantly different velocities of the Culvert Avoidance and Minimization form. More
information would be needed on dates and conditions and methods of the 2 measurements. Perhaps nearby USGS
gauges could be helpful. Low flow measurements should be taken during normal flows, not the lower flows during a
drought or significantly dry periods. Higher flows and the flow point that blockage occurs should be considered,
especially where this bridge is located in the landscape. In order for fish and aquatic life to access Fork Creek as a refuge
during storm flows in the Pacolet River, velocities would need to remain passable despite increase in flows. Regardless,
velocities are not the only concern.

We recommend alternative designs that do not split the stream flow be developed, such as an aluminum arched culvert
or spanning structure. Adequate width and passage of storm flows that improve the existing design should be
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provided. We still believe that the current proposed design may be a barrier to aquatic life passage and does not
represent an appropriate modern design.

Marla

Marla Chambers // NCDOT Coordinator

Habitat Conservation Program

NC Wildlife Resources Commission
c/o NCDOT

206 Charter Street

Albemarle, North Carolina 28001
office: 704-982-9181
mobile: [phone]
[e-mail]

ncwildlife.org

From: Davis, Mark S
Sent: Thursday, November 12, 2015 9:57 AM
To: Chambers, Marla J; 'Lori Beckwith ([e-mail])'
Cc: Deyton, Joshua B; Hill, Mark E; Chapman, Amy; Carpenter,Kristi; Barnett, Kevin; McHenry, David G
Subject: FW: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County

Marla and Lori,

See the email below and the attached information regarding the culvert avoidance and minimization form for the
subject project. The project was reviewed by Stephen Morgan of our Hydraulics Unit and it appears the former form
was incorrect. This project has been in the works since 2008 and been passed around to several DOT units before it
finally found its way to the Division 14 Bridge Management Unit. There have been at least two or three consulting firms
working on this project since inception, which probably led to the incorrect culvert avoidance and minimization
form. The Department does not believe a bridge is warranted at this site. If you have any further questions, please
advise.

Thanks, Mark

Mark S. Davis
Environmental Supervisor

NC Department of Transportation/Division 14

828 586 2141 office

282 508 9670 mobile
[e-mail]

253 Webster Road

Sylva, NC 28779

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Email correspondence to and from this address is subject to the

North Carolina Public Records Law and may be disclosed to third parties.

From: Morgan, Stephen R
Sent: Tuesday, November 10, 2015 5:56 PM
To: Davis, Mark S
Cc: Djernes, Roger E
Subject: RE: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County

Mark,

The Culvert Avoidance and Minimization Form should be revised as attached.
My response to WRC comments are below.

Thanks,
Stephen

Please note the corrections to the Culvert Avoidance and Minimization form. The low flow velocities were taken from
higher storm events and therefore were incorrect. Also, the stream width is variable and boulder-rich, creating many
natural bifurcations throughout this reach.
The channel width, form and slope are not significantly altered by the design. While the culvert is a double barrel
culvert, we fully anticipate it to function very much the same as the existing two span bridge. The culvert geometry,
slope and bed material will approximate those of the existing bridge, thus providing similar passage for
terrestrial wildlife as well as aquatic species. The culvert will be sufficiently buried and the stream is sufficiently stable
with bed armoring to alleviate any concerns of head-cutting or culvert perching.

In the sketch below, note how the culvert width and bridge width are very similar:

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Also note how the stream width as shown by the JS lines vary in the above depiction. They are much wider upstream
than downstream. Because these lines represent the limits of jurisdictional waters they include several sections of
varying stream widths and bifurcated flows due to boulder depositions- see attached pictures.

We would anticipate any woody debris capture to behave similarly or better than the existing bridge, which has a much
wider center bridge bent. The existing bridge does not appear to capture appreciable amounts of woody debris. Similarly
any mid-channel deposition would be similar to the existing bridge. No mid-channel deposition was present downstream
of the site.

Also included are pictures from a reference project that replaced a two span bridge with a double barrel culvert on a
trout stream in Madison County. The drainage area was 6 square miles for that site versus 2 square miles for this site.
The culvert was buried with baffles and sills to retain bedload.

We fully anticipate any of the concerns raised by WRC to be mitigated appropriately. We fully expect the net result to be
a stream crossing that will provide terrestrial and aquatic passage while providing the long-term operational and
economic benefits of a culvert structure.

Stephen Morgan, PE

Project Manager, Design Support

Hydraulics Unit

NCDOT

919 707 6739 office

919 961 0887 mobile

[e-mail]

1590 Mail Service Center
Raleigh NC 27699-1590
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1020 Birch Ridge Dr

Raleigh NC 27610

Email correspondence to and from this address is subject to the

North Carolina Public Records Law and may be disclosed to third parties.

_____________________________________________________________

From: Davis, Mark S
Sent: Thursday, October 29, 2015 8:56 AM
To: Morgan, Stephen R; Djernes, Roger E
Subject: FW: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County

Stephen,

Please response to the comments below.

Roger,

We have the same concerns for Bridge No. 107 in Graham County as we discussed yesterday.

Thanks for your help, Mark

From: Chambers, Marla J
Sent: Wednesday, October 28, 2015 3:56 PM
To: Beckwith, Loretta A SAW
Cc: Davis, Mark S; Chapman, Amy; Barnett, Kevin
Subject: RE: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County

I have significant concerns regarding the design of this bridge replacement project involving a trout stream. Our scoping
comments from 2009 are attached; this project is number 17 in the project specific comments section (page 6). It
appears that the proposed design will convert this bridge crossing, just upstream of the confluence with the Pacolet
River, to a 2-barreled box culvert on a 4% slope that apparently splits the flow of this reported 20’ wide stream into two
11’ wide barrels. As the Bridge to Culvert Avoidance and Minimization form indicates, this will increase the existing low
flow velocity of 5.9 fps to 8.9 fps. I found the following in the Technical Supplement 14N – Fish Passage and Screening
Design (Part 654 National Engineering Handbook, 2007):

For adult salmonid passage through a culvert, NOAA
Fisheries Service (2000) recommends average calculated
velocities of 6.0 feet per second for distances
of less than 60 feet, 4.0 feet per second for distances
between 100 and 200 feet, and 2.0 feet per second for
distances greater than 300 feet.

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You can access the handbook at http://directives.sc.egov.usda.gov/17824.wba.

Standard recommendations in our scoping letters indicate that a continuum of water depth and channel width without
substantial modifications of velocity should be provided. Concerns with splitting the stream flow have been voiced
before and included altering the natural flows, potentially decreasing velocities upstream and forming mid-channel bars
or stream aggradation and increasing velocities at the outlet, potentially creating scour and perching the culvert. Woody
debris is more likely to get caught up at the inlet, causing maintenance issues and potentially exacerbating the effects of
the altered flow. The project also appears to narrow and reduce the opening for flood flows at this crossing and
provides no flood plain access; which seems important at a location in very close proximity to a river. The ability of fish
and other aquatic species to access tributaries for spawning and refuge is vital and the current design of this crossing
may block passage due to slope, velocities, and altered flow regimes.

Stream corridors often serve as travel corridors for wildlife. Crossing designs that allow wildlife passage are also
important concerns that should be considered for this project to increase safety for the traveling public and animals,
alike, and to reduce the negative effects of habitat fragmentation. As indicated in our scoping comments, Wild Rainbow
Trout occur in the project area, as well as rare fish and crayfish species. The Rainbow Trout moratorium from January 1
to April 15 and Design Standards in Sensitive Watersheds should apply to any bridge replacement project at this
location. We believe replacing this bridge with another spanning structure is the most appropriate for this location,
setting, and existing fish and wildlife resources.

I recommend further investigation into an appropriate design for this crossing. I can participate in a site visit, if
desired. If a formal letter is needed, let me know.

Thank you,
Marla

Marla Chambers // NCDOT Coordinator

Habitat Conservation Program

NC Wildlife Resources Commission
c/o NCDOT

206 Charter Street

Albemarle, North Carolina 28001
office: 704-982-9181
mobile: [phone]
[e-mail]

ncwildlife.org

From: Davis, Mark S
Sent: Tuesday, September 29, 2015 10:19 AM
To: Beckwith, Loretta A SAW; Chapman, Amy; Carpenter,Kristi; Barnett, Kevin; Jason Mays ([e-mail]);
Chambers, Marla J; DeWit, Benjamin J
Cc: Deyton, Joshua B; Hill, Mark E
Subject: B-4792 - Bridge No. 4 - NW 14 Permit Application - Polk County

Ladies and Gentlemen,

Attached for your review and comment is the subject permit application. If you have any questions, please advise.
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Thanks, Mark

Mark S. Davis
Division 14 Environmental Supervisor
253 Webster Rd.
Sylva, NC 28779
828-586-2141
email: [e-mail]

Email correspondence to and from this sender is subject to the N.C. Public Records Law and may be disclosed to third parties.
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