Installation of Marine Pile Foundations at the Skyway Project for the San Francisco Oakland Bay Bridge-PDF

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The Skyway segment of the San Francisco–Oakland Bay Bridge required 28 marine pier foundations in challenging Bay mud and deep-water conditions. Twenty foundations used sheet-pile cofferdams; eight western piers were built without cofferdams using steel cradles to support their footing boxes.<br /><br />Early design changes improved constructability and helped meet strict alignment tolerances. Instead of driving piles first and lowering a footing box over them, crews positioned each box before driving the piles through its sleeves. The pile-to-box connection was also redesigned to allow welding from inside the pile and footing box, where access was better.<br /><br />Construction began with dredging an access causeway for marine equipment, followed by additional “glory hole” dredging at selected sites to reduce soil pressure on cofferdams. For cofferdam piers, large wale frames were placed and secured with support piles before sheet piles were driven. Crews then excavated to the required depth and installed a carefully leveled gravel bed.<br /><br />Each 900-ton footing box was fabricated in Texas, shipped by barge to San Francisco, ballasted with concrete, and lowered into position using a specially built catamaran barge. After its position was checked, locking fill secured it and supported the cofferdam during dewatering.<br /><br />The foundations were supported by six 2.5-meter-diameter piles per box, averaging 108 meters long. Piles were driven in two sections using hydraulic hammers and templates to maintain alignment. Once driven, they were cut to grade, cleaned, sealed, and fitted with 75-millimeter shear plates connecting them to the box sleeves. The connections were welded, grouted, and filled with concrete.<br /><br />The project’s success depended on early coordination among the owner, designer, and contractor, along with specialized marine equipment and construction methods. Planning-stage modifications reduced installation risks and enabled all footing structures to be installed within required tolerances.

Keywords

San Francisco–Oakland Bay Bridge

Skyway segment

marine pier foundations

Bay mud

cofferdams

footing boxes

sheet piles

dredging

pile driving

marine construction