Global was contracted to assist with the underwater construction of a launch portal for the San Francisco Bay Tunnel project, part of the Hetch Hetchy Water System Improvement Program. Diving was conducted to depths of 130 fsw in zero visibility. The crews installed rebar dowels, rebar mats, and assisted with the tremmie pour of a ten-foot thick concrete floor. After the tremmie pour was completed, the shaft was dewatered in preparation for the tunnel construction. Upon completion of the shaft, construction on the horizontal tunnel under San Francisco Bay could begin, drilled with a Tunnel Boring Machine (TBM).

News:2/22/11: Tunnel below bay will pipe water (San Francisco Examiner)
9/25/10: Construction underway on SF Bay tunnel (ABC San Francisco)
3/1/10: Bay Tunnel Project Overview (San Francisco Public Utilities)

Project Documents:
Bay Tunnel Fact Sheet