HomeMy WebLinkAbout20170220 Ver 1_USACE Compliance Comments_20180606Carpenter,Kristi
From: Bailey, David E CIV USARMY CESAW (US)
<David.E.Bailey2@usace.army.mil>
Sent: Thursday, June 07, 2018 9:59 AM
To: Thomson, Nicole J; Parker, Jerry A
Cc: Norton, Apri) R
Subject: [External] Compliance: Bridge 349, SR 2715, Guilford
Co; SAW-2017-00367
Attachments: 20180605 Notes and Pics.pdf
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Hi Nikki and Jerry. Following our visit to U-2525B on Tuesday, April and I visited 3 bridge
to culvert projects completed late last year. One of those was a bridge to triple-box
culvert project, Bridge 349 on SR 2715 in Guilford Co. The culvert was installed, the road
shoulder slopes appeared stable, and the project was open to traffic. Although stream
flow on the day of the site visit appeared to be normal, this stream appears to see large
fluctuations in flow and transports a large bed load of sediment. As such, there were
large bars/benches that had been recently deposited and it was difficult to see the sills
and whether they were installed according to plans. That said, it is clear that while the
designed low flow (i.e. main flow) culvert box was the middle box, the stream is using
the western-most hi flow box as the low flow box. The rip rap placed a few feet in front
of the western-most hi flow box, intended as the toe of a narrow floodplain bench, has
either been washed way or is partially buried in sediment; the small designed floodplain
bench in this area is completely inundated. The middle box has silted in with between 2
and 3 feet thick sediment. The eastern hi flow box appears to be functioning as
designed. Please see the attached marked-up plan sheet and pictures to help illustrate
our findings.
Since the stream flow is concentrated in the western hi flow box, the downstream
constructed floodplain bench on the west side of the stream has become unstable. Flow
from the western-most culvert exits the box, and immediately turns 90 degrees, over
the rip rap floodplain bench toe, and back into the old channel. Currently, matting is
bunched up along the rip rap toe. However, long-term this is an unstable situation that
will lead to this portion of the floodplain bench being eroded away. Further, given that
the sill in the center box is 1 foot lower than the 2 outside boxes, hi flows could be
expected to push the large amounts of accumulated sediment downstream in a large
pulse.
Since the culvert is not functioning as designed (as permitted), please provide
information regarding how the project will be augmented to provide long term stability
at the stream crossing location. It is possible that additional permitting will be necessary
depending on the proposed solution. Please let me know if you have any questions.
-Dave Bailey
David E. Bailey, PWS
Regulatory Project Manager
US Army Corps of Engineers
CE-SAW-RG-R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Phone: (919) 554-4884, Ext. 30.
Fax: (919) 562-0421
Email: David.E.Bailey2@usace.army.mil
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