Bay Bridge SAS E2-T1 Foundations - Oakland, Calif.
The Bay Bridge SAS E2/T1 project involved building the foundation of the self-anchored-suspension tower and constructing the eastern-most support structure for the Skyway Segment.
The E2, or eastern support, features two pile-supported footings linked by a reinforced concrete box and surmounted by pier columns to support the bridge's twin road decks. The construction of twin foundations required eight piles to be driven down into bedrock. A 52-foot-long concrete box section connects the two footings. The three-part structure is 220 feet long by 80 feet wide. Crews then constructed two, 120-foot-tall reinforced concrete pier columns.
The foundation for the 530-foot-tall steel tower called the T1 footing entailed constructing a concrete and steel base structure supported by 13 cast-in-drilled-hole piles set deep into underlying rock. Crews bored holes 196 feet deep through the thin mud layer into the bedrock. The top 107 feet of the pile is encased in an eight-foot-diameter permanent steel shell. The bottom 98 feet of the pile is a “rock socket” with steel-cage-reinforced concrete extending down into the bedrock without a steel casing. The entire footing frame is encased in concrete and formed a final footing structure 85 feet long, 73 feet wide and 21 feet thick.