Borehole GPR to Detect and Map Deviated H-Pile Foundations

The East Side Combined Sewer Overflow (CSO) Tunnel in Portland, Oregon will pass through a major elevated freeway interchange where it will negotiate a series of steel H-pile deep foundations. Given the high risk of encountering an obstruction during tunnel excavation, geophysical techniques were used to assess the risk of encountering H-pile foundations. Borehole ground penetrating radar and magnetometer surveys were performed along the proposed tunnel alignment to detect potential deviant H-piles. Results of the survey indicated a deviant pile that potentially conflicted with the proposed tunnel alignment and the alignment was subsequently relocated to avoid the potential obstruction.