Avoidance & Minimization.docx

Monday December 4, 2017
17BPJ.C.17
Guilford
40 2112
SR2735 (Sockwell Rd)
1.2 MI. E. JCT. NC61
UT to Reedy Fork
Google Map Link:
https://www.qooqle.com/maps/dir/36.1741762,-79.5513614/36.1741492,-79.551197/(c�36.1727299,-
79.5694932,7234m/data=!3m 1! 1 e3!4m2!4m 1!3e2?hl=en
Description of Need and Purpose:
The purpose of the project is to replace a non-inventory pipe (#40_2112) carrying the
waters of an unnamed tributary of Reedy Fork underneath SR2735 (Sockwell Rd) in
Guilford County. It is proposed to replace the existing 72" x 53" Arch Tile Pipe with an 87"
x 63" Corrugated Aluminum Alloy Pipe Arch with headwalls and sills. An off-site detour will
be utilized. The existing structure was constructed in the early decades of the 20t" century.
Actual date of construction is not known.
The current structure has reached the end of its life cycle. Severe scour exists under its
foundations which makes to susceptible to catastrophic failure during large flood events.
End walls are failing causing the shoulders of the roadway to erode.
Avoidance and Minimization:
The structure is in a tangent section of roadway which makes keeping the current center-
line alignment of upmost importance. Current lane widths of 10 feet will be maintained.
No additional lane width is anticipated.
In order to bring this section of roadway up to current safety standards we are now
required to install guardrail. Additional shoulder width is now required. Current shoulder
width on the north side varies from 3— 4 feet and the south side is less than 1 foot. The
minimum shoulder width in a guardrail section is 7 feet; therefore, additional shoulder is
required.
The length of the pipe has been minimized by using headwalls at both inlet and outlets.
The inlet headwall will provide stability for the roadway slope around the inlet as well as
improve flow characteristics of the structure.
The following options were considered but were not feasible:

Installing curb and gutter to reduce the need of extra shoulder width. Due to the
sag vertical curve and the requirement of the Jordan Lake Buffer Rules not to
discharge within the buffer zone this is not possible.
• Shifting the roadway to the south to avoid the ROW need on the north side would
more than double the footprint of the project. Due to this structure being in a
tangent section of roadway even a minimum center line shift of 3 feet would
increase the project length by 500 feet. We anticipate a center line shift of at least
20 feet. Shifting the roadway would require substantial additional ROW along with
a much larger area of disturbed soil which increases the protentional of
sedimentation loss.
Steepening of side slopes to reduce culvert length and minimize project footprint.
Steeper slopes than what is proposed were reviewed. This would require the use of
an armored (rip rap) slope to provide long-term slope stability. Even with the
steeper slope the rip rap application depth will project to a similar footprint as that
of the proposed flatter slope. There is negligible reduction in project footprint and
easements using steeper, armored side slopes.
• Replacing existing culvert at same location. Consideration was given to realigning
pipe to improve entrance and exit angle to receiving stream. However, this would
result in additional stream impacts. The existing stream banks are stable at inlet
and outlet so determined to keep alignment as is at existing location to minimize
impacts.
The Purpose of PDE:
The PDE will allow for the additional shoulder width and construction of the new shoulder.
Minimal clearing will occur in the PDE to allow for proper erosion control measures, (silt
fence).
Rip Rap will be placed at the toe of the roadway slope in locations where the existing ditch
is being encroached upon. Existing ditches on this project are on steep gradients so the toe
protection will provide stability and reduce velocities. The rip rap will be placed by
excavator from the roadway. We do not anticipate any equipment in the PDE other than
what is needed to install erosion control devices.
The proposed project, as designed, has minimized the footprint of the project and avoided
additional soil disturbance.