20191358 Ver 1_Advice on culvert repair_20191206

From: Amschler, Crystal C CIV USARMY CESAW (US)
To: McHenry, David G; Mitchell, Robert K; Mathis, Amy - FS
Cc: Breedlove, Patrick J; Chambers, Marla J
Subject: [External] RE: Advice on culvert repair in Muskrat Branch in Clay County
Date: Friday, December 6, 2019 1:57:08 PM
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Dave,
I've reviewed the project changes and the requirements under NWP-3 and determined that the new
proposal meets the requirements and conditions of NWP-3. Based on previous correspondences,
maintaining a perched condition on the culvert (that will remain in place and only have the collapsed
portion removed) provides more benefit to the aquatic environment than burial of the culvert
would, as the perched condition provides a barrier to prevent rainbow trout traveling upstream into
the native brook trout population. Both WRC and USFS have expressed support for this design in
order to protect the native brook trout population. In addition, WRC has also recommend that the
project adhere to the Rainbow Trout Moratorium and that in -stream work and land disturbance be
prohibited within the 25-foot trout buffer from January 1 to April 15 to protect the egg and fry
stages of trout.
As such, DOT is authorized to proceed with this project under NWP 3 with no further coordination
with this office required, and as long as the work is conducted as described and adheres to the
Rainbow Trout Moratorium.
Sincerely,
Crystal C. Amschler
Project Manager
Asheville Regulatory
Field Office
151 Patton Avenue,
Room 208
Asheville, NC 28403
(828)-271-7980 Ext 4231
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From: McHenry, David G [mailto:[e-mail]]
Sent: Thursday, December 5, 2019 4:49 PM
To: Amschler, Crystal C CIV USARMY CESAW (US) <[e-mail]>; Mitchell,
Robert K <[e-mail]>; Mathis, Amy - FS <amy. math [e-mail]>
Cc: Breedlove, Patrick J <[e-mail]>; Chambers, Marla J

<[e-mail]>
Subject: [Non-DoD Source] Advice on culvert repair in Muskrat Branch in Clay County
As we spoke about today, though time is short, we are still hoping to get work done on this before
January 1, only now we may just cut the damaged pipe section off (approx. 45 feet) and construct a
large rock -lined channel/flume instead of putting back new culvert. We would leave the remaining
culvert outlet perched and place a large "flat rock" directly under the outflow, but then also
construct a rock -lined channel below it in footprint of where the damaged culvert was. The rock in
this channel would be fitted together as much as possible using very large and relatively flat sided
boulders. This would hopefully prevent much flow refugia from forming and maintain sediment
transport below the culvert. This is generally similar to the flume concept Brian with USFS
mentioned when we met out there and should keep the perch and shallow water at the base of the
outflow as Jason with USFS had in mind as well.
It seems with the granted variance from the long moratorium that the work would now be
consistent with NWP 3 non -notification or even NWP 18 non -notification, provided we could do the
work in the wet. This "flume option" would avoid having to cut any trees and not require placing
dewatering pipe and sand bags though the 600 feet or so of pipe upstream, per the original plan.
Our maintenance folks don't believe they could just sand bag at the downstream end of the pipe
and keep it from blowing through. Though working in the wet is not desirable, in this situation the
amount of fine sediment lost from excavating the old culvert section out should be minimal because
this area is already open and has been well -scoured by high flows. And, the work would probably
only take a few hours/half day. Please advise what thoughts you may have on permitting needs, if
any, or other aspects of this.
And Amy, if you would not mind checking with Jason, I would appreciate that so he knows the plan
now. And please let me know if you all have any other thoughts on it.
Thanks
Dave
From: McHenry, David G
Sent: Monday, August 19, 2019 5:03 PM
To: Amschler, Crystal C SAW ([e-mail])
<[e-mail]>; Chambers, Marla J <[e-mail]>
Cc: Breedlove, Patrick <[e-mail]>; Barnett, Kevin <[e-mail]>;
Mathis, Amy - FS <amy. math [e-mail]>
Subject: Culvert repair in Muskrat Branch in Clay County
0,
We would please appreciate some advice with a culvert section repair on a trout stream that we

have been having difficulty arranging. The location is on Muskrat Branch in Clay County (see map).
The last 45 feet or so of about 600' of round culvert upstream under US 64 has collapsed. The USFS
has noted that there are now rainbow trout upstream of the highway in this creek where there were
once only brook trout. It is possible that there are flow refugia in this long culvert that have allowed
rainbow trout to ascend, though the culvert has about a 6% slope. USFS has recommended (see
attached correspondence) that we leave the new culvert in an impassible situation, such as by
keeping the new culvert section in a perched condition, if possible. This may be unavoidable
anyway. But, we understand that this would require a variance from Nationwide conditions. We
are also evaluating whether we can replace the failed length of corrugated pipe with smooth wall
pipe or can place a large flat rock to dissipate outflow to further impair fish passage here. Attached
are pictures of the culvert in 2016 and again in 2019 showing how the rock road fill above has
washed-out and reduced the magnitude of perch in the scour pool below the outlet.
Please advise your thoughts permit -wise, concerns, ideas... anything.
Note that there is an attached erosion control plan (see attached) showing a new access road to the
culvert inlet. This would allow for construction of temporary dewatering pipe (600 feet plus) inside
the existing culvert to work in the dry at the outlet. However, this would require considerable tree
clearing for equipment access, and so I have asked that the contractor evaluate whether they can
avoid that and just do sandbag dam in the old pipe near the outlet. They are still considering that,
though I suspect it would be possible if the work was done under quickly and under low flows as we
have now.
One other alternative might be to excavate around the old pipe, fill around it with large boulders and
then just cut-out most if not all of the old pipe. The engineers are not too keen on that idea since
they want the culvert length back so they can rebuild a more stable fill slope. However, I am not
sure it is off the table.
Thanks
Dave
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