Contractors on the centerpiece of San Francisco’s $4.6-billion upgrade of the Hetch Hetchy water system, a $215.3-million tunnel under San Francisco Bay that will replace the 1920s-era pipeline structure, were told to start work on April 1. Officials say the seismically enhanced structure and others planned will better protect the city water supply in an earthquake, such as the Southern California temblor on April 4.
The five-mile-long tunnel will replace old structures with a 9-ft-dia welded steel pipeline bored as deep as 100 ft under the bay’s floor. A tunnel-boring machine will minimize environmental impact. Awarded the construction contract in January is the joint venture of Michels Corp., Brownsville, Wis., Jay Dee Contractors Inc., Livonia, Mich., and Frank Coluccio Construction, Seattle, the team now building the latter city’s Sound Transit tunnel.