M-15 over the Cass River Bridge

Owner: Michigan Department of Transportation
Location: Vassar, MI

Hardman Construction is currently working on the M-15 Bridge project in Vassar, Michigan. Hardman Construction is the prime contractor on the project, which includes the removal of the existing bridge and construction of the new structure, all while maintaining traffic on one side of the bridge at a time. Built in 1938, the former bridge was a 165’ long, three-span structure that carried two lanes of traffic through downtown Vassar. Both of its abutments and piers sat on spread footings. The new structure is a 214’ long, three-span bridge that will carry two lanes of traffic. The three spans crossing the river are made up of 25” steel beams which sit on both fixed and rocker bearings. The 48’ long approaches consist of 21” pre-stressed box beams which increases the total length to 310’. The project is being built as a part-width bridge project. By staging it as such, it allows motorists to cross the bridge on one side while removing and replacing the other half. Temporary traffic signals were installed at each end of the bridge to allow for safe traffic flow from each direction in the single lane. In order for construction traffic to access the pier work in the river, temporary causeways were built from each side of the river’s bank out to the closest pier in the river. These temporary causeways are built by placing layers of geotextile material on the river bottom. Rows of flexible, intermediate bulk container bags (FIBC bags) filled with clean, washed stone are placed along the causeway's edges, and a 12’ deep turbidity curtain is wrapped along the edges to contain any sediments from entering the river. The inside of the causeway is then filled with additional clean, washed stone. Each abutment and pier sits on four 5' diameter drilled shafts drilled down from 15’ to 23’ into the bedrock for a total length of approximately 62’. Each shaft is Cross Hole-Sonic Tested (SCL) to verify that the entire length of the shaft is free from anomalies. The structural steel beams sit on both fixed and rocker bearings. Each of the seven beam lines across the width of the bridge consists of two beams across the three spans, both with lengths of 98’ and 112’. Portions of the existing steel bridge railing is to be salvaged and used on the new bridge. The project started in the fall 2014 and will be completed in the fall of 2015.

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