East Bay Municipal Utilities District (EBMUD)
The Claremont Tunnel was a major priority of EBMUD’s 10-year seismic improvement program. The old tunnel was an 18,000 linear foot, 9-foot diameter horseshoe tunnel that carried treated water from the Orinda Filtration Plant through the Berkeley Hills to three distribution aqueducts. The original tunnel construction was completed in 1928 and is lined with a combination of reinforced and unreinforced concrete. The tunnel alignment crosses an actively creeping portion of the Hayward Fault Zone for a length of 920 feet. Studies indicate that a large-scale seismic event on the Hayward Fault will result in up to a 7.5 foot earth shift causing severe damage to the tunnel. Since the tunnel accounts for the water supply for 70 percent of the District’s customers, strengthening this link was critical to the success of the Seismic Improvement Program.
Aside from the areas affected by the fault zone, the remaining three miles of the Claremont Tunnel were vulnerable to damage from seismic shaking. To improve this condition, systematic contact grouting was performed to promote better ground/liner interaction. Construction on the improvements to the existing tunnel and on the bypass tunnel was completed in mid-2006.
EPC provided construction management and inspection services on the project. As part of the project, a bypass tunnel was constructed using the New Austrian Tunneling Method (NATM). EPC provided NATM tunnel inspection for the bypass tunnel.