The Los Angeles Department of Water and Power (LADWP), and the Los Angeles County Department of Public Works broke ground this month on the Tujunga Spreading Grounds Enhancement Project, a $29-million expansion of an existing facility that will double its capacity to capture stormwater for local use.
Currently, the Tujunga Spreading Grounds can capture and store about 8,000 acre-ft, or 2.5 billion gallons of water a year. Once the enhancement is complete in 2018, that capacity will expand to 16,000 acre-ft, or 5 billion gallons, says LADWP. This enough water to supply 48,000 Los Angeles households every year.
In addition to conserving water, the enhancement will provide new open space and a walking path for neighborhood residents.
LADWP hired MWH Global Inc. to prepare the Final EIR report for the project, while the Los Angeles County Flood Control District designed the basin enhancement portion of the project. MWH Global is also responsible for developing the landscaping plan. W.A. Rasic Construction Company, Inc. is the contractor for earthwork and basin enhancement construction.
Crews are currently performing earthwork consisting of excavating existing basins and constructing new access roads and berms around the facility. In addition, a soil conveyor system that will be used to transport excavated soil off site is being installed to mitigate construction impacts on neighborhood residents and decrease the number of excavation trucks.
Art Castro, LADWP project manager on the Tujunga project, told me the EIR recommended a soil conveyor system in lieu of typical dump trucks to mitigate air quality impacts and to limit construction traffic and noise in the project vicinity. He says the incorporation of the conveyor will eliminate an estimated 180,000 truck trips throughout the life of the project.
"Although conventional, the installation of the soil conveyor system requires additional planning, permitting and construction in order to provide access across existing roads and open channels," says Castro. "Some of the additional work includes trenching, tunneling, and jacking and boring, that require further engineering evaluation and specialty construction."
He says the soil conveyor will be able to transport up to 1.7 million tons of excavated soil off site by the end of the project.
The enhancement is part of LADWP’s Stormwater Capture Master Plan, which aims to expand Los Angeles’ local water supply and reduce the city’s reliance on imported water. It also advances several of the objectives outlined in the city's Sustainable City Plan, including the goal of increasing local stormwater capture to 150,000 acre-ft per year by 2035.
LADWP says it plans to continue implementing stormwater capture projects that reduce the amount of runoff lost to the ocean, with large-scale spreading grounds enhancements like the Tujunga enhancement, as well as smaller projects like green streets, rain gardens, and rain barrels.
The Tujunga project is designed and managed by LA County Public Works. The department operates 14 major dams and 26 spreading grounds on behalf of the LA County Flood Control District, including the Tujunga Spreading Grounds facility.