The Los Angeles Department of Water and Power (LADWP) broke ground last week on the second of two 110-million gallon reservoirs that make up the Headworks Underground Reservoir Project. Like its predecessor, which completed last June, this massive, $230-million concrete tank will be the largest underground reservoir in the Western United States.

Known as the Headworks West, the project sits on a 43-acre site beside the 5 Freeway and Griffith Park, in the city of Burbank, about five miles north of Downtown Los Angeles. When complete in 2018, it will replace the storage once provided by the Silver Lake and Ivanhoe reservoirs. Its cutting-edge technology and design will significantly improve LADWP’s ability to manage the quality and reliability of the water stored there, say project officials.

Because LADWP recently completed roughly the same reservoir, the project team says construction should be relatively smooth. But because of uncertain soil conditions under the new storage facility, the design side of things are a little trickier, says William Lai, LADWP design manager.

"The two sites are not the same and the soil conditions on Headworks West are very strange," says Lai. "We have bedrock that is sloping down to the west and the bedrock is fractured." He says the project site, which was once a spreading ground for the Los Angeles River, has overtime been filled with loose sediment, which in an earthquake could cause liquefaction.

To remedy the situation, Moorpark, CA-based Sharma General Engineering Contractors is working with LADWP's in-house design team to improve soil conditions and remove liquefiable materials. Once the site is remediated and the design is 90 percent complete, LADWP can turn design documents over to the state's Division of Safety of Dams (DSOD), which oversees mass-concrete water-bearing structures.

Lai says the design is currently about 75 percent complete and should be finished, along with site prep in late summer. He says bidding for a lead contractor will go out this October or November and should be filled by early next year, with major construction operations to follow shortly.

As with the Phase 1 reservoir, this segment will be all about the concrete, as it is planned to consume some 140,000 tons of it. To avoid traffic jams on the freeway and local streets, the project team will once again build an on-site concrete production plant.

Once Headworks West is complete in 2018, both concrete structures will be buried under two to three feet of soil and native vegetation, and the site will incorporate seamlessly into the L.A. River revitalization. In addition to underground storage, the site will include a four-megawatt hydroelectric power plant — the only element of the facility that will be visible above ground.