On August 22, 2016, the Los Angeles Department of Water and Power began construction on the Tujunga Spreading Grounds, a project that is expected to capture about 5 billion gallons of stormwater per year. The Tujunga Spreading Grounds construction will reconfigure the 20 spreading basins into 9 deeper basins through the removal of soil and sediment from the site.
After completion, the Tujunga Spreading Grounds enhancement project will recharge the San Fernando Groundwater Basin with enough water to supply 48,000 households. The project, which is expected to be completed in 2018, will double the size of its storage from 2.5 billion gallons (8,000 acre-feet of water) to 5 billion gallons (16,000 acre-feet) per year. The project will capture stormwater that would otherwise flow to the Pacific Ocean.
The total project cost, including design, management, and construction: $27 Million. The project is funded by LADWP and has been awarded a $3 Million grant through the Integrated Regional Water Management Plan under Proposition 84. LADWP prepared an Initial Study and Notice of Preparation for the project in 2012. An Environmental Impact Report was prepared for the project and adopted in June 2013.
The Importance of Capturing Stormwater
Capturing stormwater to recharge local groundwater supplies is an important component to manage drought and provide a reliable supply of water to California residents. Capturing stormwater runoff may be accomplished by harvesting the runoff from rooftops, in rain barrels and cisterns for direct use in non-potable applications, or directing the runoff to open spaces and allowing it to infiltrate into the ground to recharge groundwater supplies, or by capturing and pumping water to spreading grounds, like the Tujunga Spreading Grounds.
Capturing this water would increase the sustainability of California’s water supplies and reduce surface water pollution in the state. The benefits of local stormwater capture projects include flood risk management, water quality, recreation, habitat, and climate resilience.
The use of water conservation facilities or spreading grounds adjacent to river channels and in soft-bottom channels permits water to percolate into groundwater basins for later pumping. These groundwater recharge facilities are located in areas where the underlying soils are composed of permeable formations and in hydraulic connection with the underlying aquifer. Water from snowmelt and rainwater runoff stored in reservoirs in the watershed is slowly released and diverted into the spreading grounds. The spreading grounds then infiltrate to groundwater.
The additional water from the Tujunga Spreading Grounds will increase the reliability of LA’s local water supply and reduce Los Angeles’ dependence on imported water. Los Angeles is in the fifth year of a drought. Our California water attorneys have learned that the LADWP also has plans for smaller stormwater capture 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.
The LA County Flood Control District is investigating additional solutions to adapt to climate change and continue to further enhance its stormwater capture efforts. Resiliency to climate change requires managing the use of existing stormwater conservation system, as well as storing stormwater for later within deep groundwater reserves. Increased infiltration and stormwater retention from these projects can replenish local groundwater reserves to provide a more reliable water supply as well as mitigate future potential flooding impacts.
Currently, only 15% of the city’s water comes from Los Angeles. More than half of Los Angeles’s water is imported and purchased from the Metropolitan Water District of Southern California. The Mayor of Los Angeles has set a goal for Los Angeles to capture 150,000 acre-feet of stormwater annually. The Tujunga Spreading Ground expansion project is expected to get the city close to 90% of the way there by 2035.