Building a Giant Water Bunker in L.A. Is No Easy Task
On the surface, the $230-million Silver Lake Reservoir Replacement Project in Burbank—which resembles a big concrete warehouse—looks like a simple project. But the construction team has had to overcome a host of hurdles, including a fast-track schedule, demanding concrete placement and a tunnel dig through sinkhole-prone soil.
"People have come to the jobsite and asked if we are building a Costco," says Alexander Reyman, construction manager for the Los Angeles Dept. of Water and Power (DWP), which is the owner and designer. "But what we are building is a lot more important; it is a sophisticated, covered reservoir that is going to get buried, and is meant to work as a flow-through reservoir."
The multiphase project, which is scheduled for completion in 2018, consists of twin 55-million-gallon reservoirs that will be hidden after construction by about 10 ft of soil; a 2,900-ft-long underground water-pipe connector; a 4-MW hydroelectric powerplant; and landscaping to cover the reservoirs. The site is located at the Headworks spreading grounds—a 43-acre former wetlands collecting site adjacent to Interstate 5 and the Los Angeles River.
The reservoir will eliminate contamination of drinking water by allowing the water to bypass the existing uncovered Silver Lake and Ivanhoe reservoirs and flow into the new Headworks Reservoir, thereby complying with new U.S. Environmental Protection Agency (EPA) water quality regulations.
The $140-million first phase broke ground in January 2013 and is scheduled for completion by Nov. 21 to meet the required EPA deadline. It includes the 550-ft-long by 535-ft-wide East Reservoir and the 8-ft-dia water pipe.
Crews are finishing up building the 35-ft-tall covered reservoir in a 45-ft-deep excavation. The concrete tub has a 4-ft-deep base slab, cast-in-place walls and a 2.5-ft-deep cover slab supported by 279 3-ft-dia columns placed in a 30-ft-square grid. The basin will contain some 18 million lb of reinforcing steel.
A Four-Sided Dam
When crews first started, the in-service date for the entire project was Nov. 21, but the project team was delayed a year at the start of construction, says Vince Quinones, the construction manager for WOL, a joint venture of Webcor Builders, Obayashi San Francisco and W.M. Lyles. SSC Construction of Corona is constructing the reservoir.
WOL attributes most of the delay to securing design approvals from the state's Division of Safety of Dams (DSOD), which oversees mass-concrete water-bearing structures.
Reyman adds: "Because of the reservoir's size and shape, [DSOD] considers it a four-sided dam and as such they have to review all the plans and construction for it before it goes into service. Part of the delay was we had to wait for them to finish reviewing our plans, so WOL had to wait to send the bid package out and by the time we got everything done, our total time left to do the construction was pretty short."