GSG conducted a comprehensive geotechnical investigation to support the reconstruction and widening of the Tri-State Tollway between I-55 and I-90. Our services included subsurface exploration, geotechnical analysis and reporting for roadways, bridges, and retaining walls, along with environmental services such as PESA reviews, PSI sampling, and tree surveys.

Our exploration program followed Illinois Tollway and IDOT Geotechnical Manuals, as well as AASHTO LRFD Bridge Specifications.

Scope of Services

• • Bridge Structures: 181 borings to depths of 60–105 feet across key structures, including I-294 over I-88, Butterfield Rd., CCP RR, I-290, Ramp J, and Electric Ave
  • Retaining Walls: 680 borings totaling 25,856 feet of drilling
  • Overhead Sign Structures: 45 locations
  • Ramp Realignment & Detention Ponds: 32 additional borings, including piezometer installations for groundwater monitoring
  • Structural Geotechnical Reports: Reports were done for all structures