In 2015, the Michigan Department of Transportation (MDOT) launched their I-75 Modernization Project, which will consist of eight construction segments. This I-75 widening and reconstruction project has been in the planning and development stages for 20 years. It encompasses 18 miles of freeway from M-102 to south of M-59. MDOT selected AECOM as their design-build contractor for Segment 1.

SME provided geotechnical engineering services for Segment 1. These services were needed for new or widened roadway embankments; foundations for new bridges at the interchange and at Squirrel, Adams and Square Lake Roads; some temporary retaining walls; new culverts; new truss and cantilever overhead freeway signs; and new traffic signals at the Adams Road exit. SME also provided design assistance during construction.

Based on a review of soil survey data for the project site, there were two probable I-75 peat marsh crossings that were of concern. Additionally, I-75 passes over two glacial moraines, and there were glacial spillway features with possible organic soils between these two moraines. Peat marsh areas can be challenging for maintaining traffic staging operations and embankment widening designs. SME was selected by the project team for its extensive experience managing peat marsh issues for highway projects.

As part of our evaluation, we addressed foundation support for seven bridges and subgrade support for pavements, which included evaluating both shallow and deep foundation systems for the bridges. In addition, SME evaluated embankment stability (especially for bridge approaches), including possible part-width construction areas and embankment settlement estimates. For pavements, we looked for poor subgrade support areas and provided recommendations to address these areas. Further, SME evaluated key constructability issues that included addressing the likelihood of shallow groundwater; possible vibration or shakedown settlement concerns due to loose sands; and geotechnical issues related to maintaining traffic during construction.