New Irvington Tunnel Project
AWARD OF MERIT
Owner San Francisco Public Utilities Commission
Lead Designer AECOM
Contractor Southland Tutor Perini JV
Construction Management Hatch Mott MacDonald
Consultant Jacobs Associates
Subcontractors Johnson Western Gunite Co.; Malcolm Drilling Co.; Municon Consultants; R&W Concrete Contractors; San Joaquin Electric; Pacific International Grout Co.
As a vital part of San Francisco’s Hetch Hetchy Regional Water System, the 1930s-era Irvington Tunnel supplies approximately 85% of the city’s water. However, the critically important tunnel had not been dewatered or physically inspected since 1966. As part of the $4.6-billion Water System Improvement Program, San Francisco built a new 3.5-mile-long tunnel to parallel the original tunnel as a seismically reliable alternative.
High groundwater inflows, gaseous conditions and two major fault zones made the $259-million project extremely challenging. Many pumps extracted water, and crews injected more than 7.8 million lb of cement before excavation to reduce inflow so the team could construct the 13-plus-ft-dia tunnel. Construction was completed with minimal disruption to the water system or to the local population, according to city officials.