20220840 Ver 1_Running Creek Rd Bridge to Culvert Justification_20220623

01/30/2019
40 - GUILFORD Br# 400183
SR2710 Running Creek Road
Gibsonville
The project consists of replacing a 33-foot-long Structurally Deficient Bridge that has a Sufficiency Rating
of 40.96 in Guilford County. The current structure is a timber deck on I-beams setting on timber caps on
timber piles. The current structure was constructed primarily with timbers in 1956. Timber structures
typically have a life span of 50 years and this structure is 63 years old and has reached the end of its life
cycle .
The proposed structure consists of a 2 @ 12' X 10' Reinforced Concrete Box Culvert. This structure
meets the hydrological requirements of the drainage area without significantly altering the FEMA Flood
studies. Typically, the length of a bridge will be much longer than that of a culvert. Increasing the
bridge length creates several issues that must be overcome . If a bridge is utilized there must be at least
four feet of clearance under the bridge to allow access for maintenance workers at the abutment. In
areas where culverts are recommended this requires us to raise the roadway grade which also increases
the impacts due to the increased fill slopes. Smaller streams in the Piedmont area are often best suited
for culverts to minimize raising the roadway grade .
Justification for bridge to culvert:
• The basin drainage area and estimated discharges are compatible with a culvert structure . And
as mentioned, typically prefer culverts due to longer service life and reduced maintenance vs a f
bridge .
• The proposed culvert and existing bridge (with vertical concrete abutments) have similar
hydraulic type openings and properties. Hydraulic function including backwater, outlet
velocities, etc. will remain similar.
• The inlet and outlet channels look stable . So, we would anticipate the same with a culvert.
Justification for shifting the Roadway:
• The main purpose for shifting the roadway is to improve safety by providing a better alignment
over the stream .