PROJECT: BONNEVILLE DAM JUVINILLE FISH BYPASS, Cascade Locks, Oregon


Bonneville 2PH Fish Bypass Overwater Becker Drilling
Cornforth Consultants was retained by the Portland District to perform geotechnical explorations and prepare a Geotechnical Data Report for three potential alignments for the Juvenile Fish Bypass System that would utilize an existing Ice and Trash Sluiceway at the upstream intake and would discharge at the downstream tip of Cascade Island.

The preliminary project design involved the installation of large diameter in-water piles or piers to support the outfall structure. The purpose of the explorations was to determine the geotechnical properties of the subsurface materials for the preliminary design, and the initial geotechnical parameters for the construction of large diameter shafts. In addition, this work was used to evaluate the geotechnical properties for pile design, evaluate the liquefaction potential during an earthquake, and establish preliminary pile design parameters. Field explorations were conducted at three potential site locations for the Corner Collector Outfall alignment.

All exploratory drilling work was conducted from a floating plant during the designated in-water work period with a Becker Drill that had the capability to convert to a mud-rotary drill. The data was also utilized to analyze the factors of safety against liquefaction during the design earthquake, and locate potentially liquefiable zones and associated downdrag loads within the overburden materials. In-situ pressure meter testing established parameters for P-Y lateral load analysis. Other recommended preliminary pile design parameters included estimated capacities due to skin friction and end bearing, and uplift resistance available in pile rock sockets.

Cornforth Consultants Inc. received an “Outstanding” performance evaluation for this project by the Portland District. In his letter of appreciation to our firm for this project, District Engineer Col. Randall J. Butler stated: “Your final product was of superior quality. We compliment you on your high degree of professionalism and very cooperative attitude.”