In preparation for construction of the Gordie Howe International Bridge (GHIB) in Detroit, MI, at the U.S.-Canada border, the Michigan Department of Transportation (MDOT) is undertaking road and utility work along two miles of I-75. As a subconsultant to Parsons Corporation, Wade Trim designed major utility relocations for the I-75 Inlay project near the location of the proposed GHIB that include combined sewer, water main and freeway drainage.

Drawing on our experience working with the Detroit Water and Sewerage Department’s combined sewer and water systems, as well as major highway modification and depressed freeway projects, Wade Trim designed a storm sewer system to accommodate a 100-year design storm. MDOT’s requirement, exceeding their typical 50-year design storm standard, was met using massive storage chambers that increase the level of protection for the roadwork associated with the I-75 Inlay project and future GHIB project.

Multiple design alternatives were developed for relocation of each combined sewer siphon, ranging in size from 6 to 12 feet in diameter. A 3D model was created to test potential utility conflicts of the sewer’s siphon pipes. Poor, clay-like ground conditions on the project site were accommodated through the addition of steel sheet piling that will be left in place. The design work was completed ahead of schedule in six months, and under budget. Construction began in late summer of 2017 and is expected to be completed in fall of 2018.