Interstate 84 Sandy River Bridge Geotechnical Investigation
Cornforth Consultants (CCI) was retained by the Oregon Bridge Delivery Partners (OBDP) to perform subsurface investigations for a replacement bridge and prepare a Geotechnical Data Report and a Geotechnical Data Sheet. OBDP managed the OTIA III State Bridge Delivery Program for ODOT. Subsurface investigations are typically performed by the foundation designer as part of the foundation design process; however, in this case, the investigations for this proposed replacement bridge were performed before the foundation designer was selected so that the drilling in the Sandy River could be completed during the in-water work period.
The field exploration program consisted of 10 borings drilled up to 185 feet deep through sand, gravel, and sporadic cobbles and boulders. In addition to the difficult subsurface conditions, additional challenges included coordinating drilling and pressuremeter testing with the in-water work period, rising waters of the river, and interstate lane closure restrictions.