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Expenses:

Bridges

The St. Clair County Road Commission is responsible for over 224 bridges throughout the county, placing it second in the state for total number of bridges on a county road system (only Wayne County has more). Bridges are defined as any structure with over 20’ of clear span. This may be a single span concrete box, a concrete abutment with steel I-beam deck or two or three large round culverts with the total opening area greater than 20’.

Bridges come in many varieties that may include steel pipes, aluminum box structures, concrete box structures, concrete abutment walls with steel I-beam and concrete deck, concrete abutment walls with concrete beams, steel abutment walls with steel I-beam and concrete deck or wood deck, concrete abutment walls with steel truss deck (St. Clair County no longer has this type of bridge) and all wooden structures. Bridge lengths within the county vary from 21’ single span structures to the largest county bridge which is a 500’ total span. The current age range of bridges is 1 year old to over 80 years old across the county. Older bridges tend to be narrower as many designed in the 1920’s and 1930’s were intended for single vehicle usage. Newer bridges are wider to accommodate at least two traffic lanes to handle higher traffic usage. Current federal design standards require all new bridges to carry a minimum of two traffic lanes plus a shoulder on each side of the roadway.

Bridge replacement costs range from $250,000 for a short span bridge (20-30’span) to greater than $1.5 million for longer spans (150’ to 200’). The major source of funding comes from the federal government through the national Highway Bridge Program. This funding source provides 95% of the total replacement cost from the federal government with the remaining 5% paid by local agencies (either the road commission and/or township). A set amount of funding is available each year through the federal government with many agencies vying for a share of the dollars.  Bridges funded by this program are chosen by a regional bridge council which must sort through all of the applicants and determine which structures are of highest need. In Michigan, generally 20-25% of the totally annual bridge applicants are funded with the remaining left unfunded. Do to the large number of bridges in St. Clair County, the Road Commission often funds bridge maintenance and replacement projects 100% from its general fund to keep up with the needed work.

All bridges must be inspected per federal regulations. These inspections are performed on a biannual basis with each structure closely checked for deterioration, vehicle damage and flood damage. Each part of the bridge is rated for its current condition and recorded in report format. The data is then entered into a national database and used by the federal government to monitor the overall system condition as well as follow the trends of each state’s bridges.



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