Paul Gribbon and Julius Strid presenting at Mid-Atlantic Region DBIA conference
Mid-Atlantic Region DBIA will be featuring Paul Gribbon and Julius Strid of Schnabel Engineering on June 17, 2021 for a presentation on the ‘Portland Method’ Contract used for the Willamette River CSO Tunnel Program in Portland, Oregon. The 10-year $850 million Program met all budgets, and met all deadlines with no prime contractor claims. This innovative alternate contracting approach for the tunnel construction included a qualifications-based contractor procurement process, a pre-construction planning phase with the selected contractors, and cost-reimbursable-fixed-fee construction contracts.
The project was the first use of slurry pressure tunnel boring machines (TBMs) in the U.S. The method was chosen primarily because of the gap-graded nested cobbles/boulders (glacial dam Missoula catastrophic flood deposits) with a face pressure of 3 bar at tunnel level. This project also included the 149-ft diameter, 160-ft deep Swan Island Pump Station located in saturated alluvium next to the Willamette River.