20211410 Ver 1_South Scales Street Bridge to Culvert Justifaction_20211105

Rockingham County Br# 780280
SR 2670
South Scales St.
Over Little Troublesome Creek

Justification of Bridge to Culvert
The project consists of replacing 23 foot long Structurally Deficient Bridge that has a Sufficiency Rating
of 63.4 in Rockingham County. The current structure was constructed primarily with concrete in 1920
with vertical breast walls with a cast in place roof slab. The existing structure is built and functions like a
culvert but due to its span length it is considered a bridge with the National Bridge Inspection Standards.
Due to scour of the foundation this structure has reached the end of its life cycle.

The proposed structure consists of a cast in place culvert, 2 barrels @ 13 feet by 12 feet high culvert.
This structure meets the hydrological requirements of the drainage area without significantly altering
the FEMA Flood studies. Culverts have lower construction and maintenance cost over the life cycle of
the structure as compared to a bridge. When site conditions allow a culvert is the preferred structure of
choice due to the lower overall cost and minimum construction time. Current budget constraints
require us to take the most economical option that meets environmental and safety concerns.
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. Raising the roadway grade also affects the FEMA Flood Plain Mapping.
In turn we cannot meet the requirements of the Memorandum of Agreement (MOA) with FEMA. If the
new bridge cannot be sized to meet the requirements of an MOA then map revisions need to be
performed for FEMA. First through a CLOMR (Conditional Letter of Map Revision) then a LOMR (Letter
Of Map Revision). NCDOT works very hard to make sure the replacement structure meets the
requirements of the MOA. Smaller streams in the Piedmont area are often best suited for culverts to
minimize raising the roadway grade. Due to the location of Industrial Drive just to the north a bridge
cannot be constructed without realigning Industrial Drive. This would add environmental impacts to the
project with additional real property cost.