INTERRA, Inc. is the Geotechnical subconsultant to the design consultant Patrick Engineering. The proposed Olympic Boulevard improvements include the extension of Olympic Boulevard west over the Rock Run (new bridge structure) to form a new east-west connection between Houbolt Road and the I-55 East Frontage Road.  INTERRA’s scope of work includes drilling eight bridge structure borings to depths of up to 70 feet, including bedrock coring with challenging site access due to overgrown vegetation and Rock Run Creek; drilling four detention pond borings to estimate rock excavation quantities; drilling 15 roadway borings for proposed lane additions and extensions; and pavement cores to determine and document existing pavement conditions. The scope of work also includes extensive laboratory testing such as unconfined compressive strength tests on soil and rock samples, grainsize analysis, Atterberg Limits, and Illinois Bearing Ratio tests.

Engineering analysis includes evaluating various bridge foundation alternatives such as shallow foundations, pile foundations and drilled shafts with rock sockets. The presence of broken bedrock and highly argillaceous rock is presenting foundation design challenges. The Roadway Geotechnical Report (RGR) and Structure Geotechnical Report (SGR) are being prepared in accordance with IDOT guidelines. The design of the bridge is in progress and INTERRA is providing ongoing geotechnical engineering support for foundation design and construction considerations.