Oakland Bay Bridge and Skyway Replacement

The Oakland Bay Bridge and Skyway were slated for replacement after a portion of the bridge’s upper deck collapsed in the 1989 Loma Prieta Earthquake. GeoEngineers was engaged to provide geotechnical consulting services to the contractor who installed the large-diameter permanent pile foundations for the Skyway Bridge portion of the bridge replacement project.

GeoEngineers also provided support for design and construction of temporary sheet pile cofferdams and other pile-supported temporary structures necessary to build the Skyway segment that would span San Francisco Bay from Yerba Buena Island to Oakland, California. Cofferdams are steel sheet pile retaining wall enclosures installed in the water to allow a temporary excavation with vertical sides to extend below mud line. For the Bay Bridge, these excavations were up to 50 feet below mud line and in about 20 feet of water. This deep excavation required lateral bracing at several levels within the cofferdam in order to resist the large lateral soil and water loads.

Approach

• Performed pile-driving analyses for a test pile program that consisted of driving three, 8-foot-diameter, 440-foot-long steel pipe piles
• Developed geotechnical criteria for design of 20 temporary cofferdams in soft Bay Mud deposits
• Addressed pile drivability and installation procedures for the two temporary end tower structures
• Developed pile capacity versus embedment criteria for temporary pile support for two work bridges, 14 tower cranes and 28 pile driving templates in accordance with the project plans and specifications

Results

• Safe and satisfactory performance of the temporary Skyway Bridge structures
• Successful installation of 160 eight-foot-diameter, steel-pipe piles while temporarily supporting the permanent pile foundation boxes