20001432_US 421 slope failure_20160810

Carpenter,Kristi
From:Wrenn, Brian L
Sent:Wednesday, August 10, 2016 8:55 AM
To:Paugh, Leilani Y; Williams, Andrew E SAW
Cc:Moore, Byron G
Subject:RE: US 421 slope failiure
Leilani,
Art gave us a brief description of the proposal in the field. I don’t recall any significant issues being raised by Andy or I
with the proposal. Obviously, the permitting mechanism is up to Andy. I would appreciate seeing the design drawings
prior to getting the application if possible.

Thanks,
Brian Wrenn
919-707-8792 (office)
919-710-6516 (mobile)

From: Paugh, Leilani Y
Sent: Monday, August 08, 2016 5:32 PM
To: Williams, Andrew E SAW <[e-mail]>
Cc: Wrenn, Brian L <[e-mail]>; Moore, Byron G <[e-mail]>
Subject: US 421 slope failiure

HI Andy and Brian
Byron Moore and I reviewed the slope failure on US 421 in Sanford with Division personnel. After review of
the site, we recommended that the stream channel should be left in place. This is due to the unstable
conditions of the channel both upstream and downstream of the slope failure area. The existing root system is
holding the channel in place. A channel relocation would require removal of the trees and excavation of a new
channel in poor soils. The right of way available is very limited by the existing sewer line so we would have no
control over the channel upstream of the area.
Division has worked with Geotech to design a buttressed slope protection to stabilize the slope after grading it
to a 2:1 ratio. We recommended a boulder toe protection in the outside bend of the channel adjacent to the
slope repair. This would stabilize the channel in place while maintaining a natural bed and bank.
For construction, Division would need a temporary stream impact at the repair area to build the buttressed
slope protection and install the boulder toe. Access would be along the sewer line crossing of the channel
upstream of the slope repair area and would also require a temporary stream crossing. We had discussed a
NW 3 as the appropriate permitting mechanism.
We should have final design drawings showing these recommendations but I wanted to get some feedback
from you about the concept and permitting.
Thanks

LeiLani Paugh
ICI/OSM Group Supervisor

919 707 6146
[e-mail]

NCDOT

Project Development & Environmental Analysis
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Raleigh, NC 27610

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