"The New Irvington Tunnel provides a seismically designed connection between water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area water distribution systems," Tsztoo says. He notes that the New Irvington course crosses seven minor fault lines that could "react sympathetically" if an earthquake occurs along the major Hayward Fault, west of the tunnel, or the Calaveras Fault to the east.

Dan McMaster, Hatch Mott MacDonald project construction manager, says the presence of those faults is a big reason why the New Irvington Tunnel line should be completed without delay.

"With the original cast-in-place line, there could be severe damage and potential collapse in the event of a major quake," McMaster says. "That's why it's critical to get this in place as soon as possible."

WSIP is funded by a bond measure that San Francisco voters approved in 2002.

Other key WSIP projects include: construction of the $224-million Bay Division Pipeline No. 5—a 46,350-ft line running through Redwood City, North Fair Oaks, San Mateo County and Menlo Park—and replacement and repair of the $59-million, 19-mile Crystal Springs Pipeline No. 2, through parts of San Francisco and San Mateo counties. Mountain Cascade Inc., Livermore, is the contractor for Bay Division Pipeline No. 5 and San Francisco-based Ranger Pipelines Inc. has the Crystal Springs construction contract.

WISP's largest project is the $434-million replacement of the Calaveras Dam in Alameda County, which is the system's main backup to the Hetch Hetchy Reservoir. Built in 1925, the earth-fill dam, located about a mile from the active Calaveras Fault, is considered seismically vulnerable. In fact, the state Dept. of Water Resources scaled back to 30% capacity there in 2001 because of safety concerns. The dam's normal capacity is 96,850 acre-ft of water, or 31 billion gallons, representing nearly half of the water storage capacity in the Bay Area.

Construction of its earth-and-rock-fill replacement began in August 2011.

The new 210-ft-high dam will have a crest length of 1,210 feet, a base thickness of 1,180 feet and a crest thickness of 80 feet. The new spillway will be 1,550 ft long. When finished, it will have a storage capacity of about 31 billion gallons—about the same as its original capacity. It also will be able to withstand a magnitude 7.25 earthquake. A joint venture of Dragados USA, Flatiron Construction and Sukut Construction is the replacement dam's construction contractor team. Completion is scheduled for late 2015.