The City of Los Angeles is looking to increase its reliance on groundwater supplies, tapping the San Fernando Basin, where a large number of wells are unused at the moment due to contamination, informs Los Angeles Times.
The restoration of the San Fernando Valley groundwater basin is one of several options to increase water supplies, together with investments in water recycling and water conservation. The city has been relying on imported water from Owens Valley, Northern California and the Colorado river, via aqueducts. As climate change strains imported water sources, it becomes even more important to source water locally.
The Los Angeles Department of Water and Power (DWP) hopes to increase the proportion of locally sourced water from the current 10% to 70% by 2035. Greater reliance on local groundwater supplies will also strengthen resilience in case of a major earthquake, since the aqueducts cross the San Andreas fault and would likely fail. The city is also investing in water recycling, such as Operation NEXT, a $16 billion plan to purify 100% of the wastewater treated at the Hyperion Water Reclamation Plant to replenish the city’s groundwater via indirect potable reuse. The city also hopes to expand the use of purified recycled water as direct potable reuse in the future.
Groundwater remediation is not a cheap option, but technology development and running out of cheaper water sources have made it more attractive. Also, the authorities spent many years in litigation, trying to find responsible parties to help pay for the huge cleanup costs. Although some companies have taken responsibility and are funding cleanup efforts, other costs are being paid by ratepayers, and other cities and the EPA are also in charge of treatment elsewhere in the basin.
Although Los Angeles has water rights in five local groundwater basins, the San Fernando Basin (SFB) accounts for nearly 80% of all local groundwater extracted. It is estimated it could potentially provide up to 21% of the total DWP water supply. There are a total of 115 groundwater wells in nine well fields in the groundwater basin, but only 41 were under operation as of 2021 due to contamination. Most of the contaminants are volatile organic compounds which likely ended up in the groundwater due to improper handling and disposal of chemicals used in industrial and commercial activities, dating back to as far as the 1940s.
Remediation efforts in the SFB started in the 1980s, through the EPA Superfund program, including identifying, containing and removing the contaminants. The DWP carried out a six-year characterization study of the well fields completed in 2015 and is currently implementing three response actions in the most productive northern SFB well fields.
Remediation facilities are in construction at the three project sites and will use best available technologies including liquid phase granular activated carbon, advanced oxidation processes, and ultraviolet light in conjunction with hydrogen peroxide. Once completed, the cleanup process will comprise multiple steps: water is pumped out of the ground, then filtered and treated. Finally, it will be fed into the distribution system of the city. The city thus hopes to restore the beneficial uses of the San Fernando Basin, including groundwater supplies as well as storage capacity for recycled water and stormwater.
