Metropolitan to begin work on dams of Southland's largest reservoir.

LOS ANGELES--(BUSINESS WIRE)--March 14, 1995--A huge excavation that will help form the foundation of the Southland's largest drinking-water reservoir and will likely yield a trove of paleontological treasures was authorized Tuesday by Metropolitan Water District of Southern California.

The MWD board of directors selected Kiewit Pacific Co.'s San Diego-based office to strip, clear and excavate about 12 million cubic yards of earth and rock to make way for one of the three dams that will create the reservoir in the Domenigoni and Diamond valleys located southwest of the city of Hemet.

"This massive undertaking marks the beginning of one of the largest earthfill dam projects in the United States," said Dennis Majors, Metropolitan's project manager for the $1.9 billion water storage facility.

"The monstrous hole that ultimately will cradle the reservoir's west dam will be large enough to hold more than six Empire State Buildings," Majors said.

When completed in 1999, the 4,500-acre lake will nearly double the coastal plain's reservoir storage capacity, providing a more reliable water supply and vital reserves for droughts, earthquakes or other emergencies.

"The reservoir will be essential to help meet Southern California's water needs well into the next century," Majors said. "It represents another increment in water development that has spanned more than 100 years and has made the Southland's $350 billion economy possible."

Unlike conventional reservoirs formed by dams on rivers and streams, Metropolitan's lake will be an offstream facility that stores water pumped into it from nearby aqueducts.

Starting in April, crews will perform large-scale trenching to clear a 1.5-mile path -- 60 feet deep and up to 2,000 feet wide -- across the west end of the Domenigoni Valley.

The initial excavation phase -- scheduled to be completed in October -- will be followed by a second, separate phase that will dig out another 7 million cubic yards of material to further expose the bedrock on which the dam foundation will rest.

During the massive digging, Majors said, the district expects to uncover a goldmine of paleontological fossils that may date as far back as the Ice Age.

"The reservoir site has the potential of becoming the Inland Empire's equivalent of the Rancho La Brea Tar Pits," Majors said, referring to the famous Los Angeles ancient asphalt deposit.

"Earlier, smaller excavations near the reservoir site have already uncovered mammoth and mastodon fossils and tusks, as well as the remains of an extinct zebra-like horse, bison, ground sloths, camel and dire wolf."

Once complete, the 1.8-mile-long dam, rising 285 feet above the valley floor, along with a longer east dam and a smaller saddle dam, will enclose the valleys to form the reservoir. Excavation of the east dam site, on the other side of the linked Domenigoni and Diamond valleys, and the saddle dam, which will plug the northern hills, is expected to begin later this spring.

"Combined, these dams will contain nearly 100 million cubic yards of clay, earth and large rock," Majors said. "By comparison, the dam for Lake Oroville, the largest reservoir on the California State Water Project system, holds just over 80 million cubic yards of earthfill."

Majors said excavation spoil materials will be either stockpiled for use later in the core of the west dam's embankment or applied to help contour the adjacent recreational area Metropolitan plans to create next to the lake. Cost of the initial excavation work is $23 million.

In addition to the excavation work, Kiewit's contract calls for the construction of a temporary diversion dike that will help control storm water runoff during construction. A new intersection along Winchester Road (State Highway 79) also will be built, and the highway will be widened to provide construction access to the site.

The Metropolitan Water District of Southern California is one of the world's largest water agencies. The district imports water from Northern California and the Colorado River, and delivers it on a wholesale basis to the Southland's coastal plain.

Through its 27 member public agencies, the district provides almost 60 percent of the water used by more than 16 million people living in portions of Los Angeles, Orange, Riverside, San Bernardino, San Diego and Ventura counties.

CONTACT: Metropolitan Water District of Southern California

Bob Gomperz, 213/217-6866 (office), 818/797-5478 (home)

Bob Muir, 213/217-6930 (office), 714/879-7478 (home)

Rob Hallwachs, 213/217-6450 (office), 818/398-7697 (home)

Jay Malinowski, 213/217-6480 (office), 818/951-4364 (home)