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Eastside Reservoir

Hemet, CA

Metropolitan Water District (MWD) of Southern California

March 1996 - September 1999

$438 million



To meet the demands of a growing population and satisfy drought and emergency needs, the Metropolitan Water District (MWD) of Southern California commissioned the $2 billion Eastside Reservoir project, also known as Diamond Valley Lake. A Zachry joint venture signed a $438 million contract to build one of three planned dams along with associated infrastructure, including an inlet/outlet tower as well as a pressure tunnel.

In the largest earth-moving project in the U.S. at the time, the joint venture excavated 5.5 million cubic yards of earth for the inlet/outlet approach channel, more than 6 million cubic yards of earth for the dam foundation and 70 million cubic yards of rock for the dam embankment. The 270-foot inlet/outlet tower and its access bridge required 95,000 cubic yards of concrete and nine million pounds of reinforcing steel.

Zachry constructed a horseshoe-shaped pressure (P-1) tunnel to connect the inlet/outlet tower to a pumping station located near the downstream face of the West Dam. The P-1 tunnel measures 2,300 feet long and 24 feet in diameter and was opened by drill-and-shoot excavation requiring 20,000 cubic yards of concrete behind a steel lining.

Work on the tunnel also required the installation of the same length of 16-foot steel pipe, complete with concrete backfill, pressure grout and epoxy liner.

The project’s overall mechanical work included a spillway, valves and 40,000 feet of miscellaneous piping, while the electrical scope incorporated multiple raceways and instrumentation and communications ducts. The completed Eastside Reservoir Dam stands 300 feet high and 1.7 miles long.

The new Diamond Valley Lake project doubled Southern California’s surface water storage capacity to more than 800,000 acre-feet, giving the MWD access to a six-month emergency water supply for use during droughts or peak water usage periods.