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L.A. to Treat Contaminated Groundwater for City Use

Workers from the Los Angeles Department of Water and Power constructing a groundwater monitoring well
The Los Angeles Department of Water and Power is constructing 26 groundwater monitoring wells in various areas of the east San Fernando Valley as part of a comprehensive groundwater system improvement project that will enhance the local groundwater supply. Los Angeles Department of Water and Power

Faced with dwindling water resources, the Los Angeles Department of Water and Power will construct an extensive system of wells and treatment facilities to pump and treat water from a superfund site in the San Fernando Valley.

September 24, 2013—Because of its geographical location and naturally dry conditions, Los Angeles has long had to import most of its water. However, in recent years drought and overreliance on imports have depleted those water sources and driven up the cost of importation. Faced with a state of affairs that is economically and environmentally unsustainable, city officials have a solution in mind: building one of the world’s largest groundwater treatment systems to capture water that is already in the city but is currently too polluted to use.

The Los Angeles Department of Water and Power (LADWP) announced this summer that it plans to construct a system of treatment facilities that would pump and treat water from San Fernando Valley’s 115 groundwater wells. Roughly half of these wells, however, are currently closed because of contamination, and many areas in the San Fernando Valley have been designated Superfund sites. Plumes of toxic chemicals have continued spreading through the valley’s groundwater over the years, forcing more and more well closures.

Between 2007 and 2012 Los Angeles obtained more than 87 percent of its water supply from northern California and the Colorado River, and just 11 percent came from the city’s groundwater wells, which represent about 80 percent of the city’s local water rights. LADWP officials expect their first groundwater treatment plant to open by 2022 and predict that using treated well water could help reduce reliance on imported water and increase groundwater use from an average of 65,000 acre-ft today to 111,500 acre-ft when implemented.

“This is an arid area, so we’re trying to take advantage of all of the sources of supply that we have,” says Susan Rowghani, P.E., M.ASCE, the LADWP’s director of water engineering and technical services. “Our other sources of supply are challenged due to drought or environmental issues, so it’s hard to leave [local groundwater] on the table and not do anything with it.”

The LADWP’s decision to bolster its groundwater treatment infrastructure derives from a comprehensive study launched in 2008. Officials estimate the city could spend as much as $800 million in constructing two initial treatment plants. Construction would begin in about five years, and additional, smaller facilities could be built later.

Groundwater quality in Los Angeles has been a concern since the 1980s, when parts of the San Fernando Valley were placed on the National Priority List and thus became Superfund sites.

Groundwater samples from the San Fernando Valley were found to contain such contaminants as trichloroethylene and perchloroethylene that dated as far back as the 1940s, when waste disposal in the valley was not regulated. Despite remedial efforts that have included closing wells and pumping and treating groundwater, the contaminants have continued to spread.

As the U.S. city ranking second in population, Los Angeles used an average of about 187 billion gal of water each year from 2007 to 2012, but various problems in recent years have made that water increasingly difficult to acquire. Aside from migrating pollutants in its groundwater, Los Angeles has seen its water supply further threatened by increasingly frequent drought conditions and growing demands from other parts of the region.

The city has traditionally imported much of its water from the Sierra Nevada, but decreased snowpack on the mountains has meant less water, which has driven up importation costs and forced Los Angeles to reduce its Sierra Nevada imports to their lowest level in a century. Additionally, excessive diversion has caused problems in the Colorado River and the vast watershed of the San Francisco Bay, forcing much of Southern California to reconsider importation, says Mark Gold, the associate director of the University of California at Los Angeles’s Institute of the Environment and Sustainability.

“We’re in an age when imported water is getting more and more expensive, and the ecological consequences of importation grow larger and larger, and the impacts of climate change and [population] growth reduce imported water supplies,” Gold says. Decreasing imports, he believes, “is just the right thing to do.”

Los Angeles is one of a number of local governments that have set goals for reducing their dependence on imported water, a group that includes Santa Monica, Camarillo, Long Beach, and Ventura County. LADWP officials say that their groundwater treatment facilities will be part of a larger sustainability effort that will involve capturing storm water, recycling water, and replenishing groundwater.

Rowghani says that the LADWP is currently in the process of drilling wells in the San Fernando Valley to determine what contaminants are present and what types of treatment would be most suitable. In the coming years the agency will begin the environmental review and permitting processes that will have to be carried out before the first facilities can be designed and built.

Environmental experts have applauded the LADWP’s plan, calling it a major shift from past policies. Gold suggests that Los Angeles officials have been reluctant to embrace the concept of treating polluted water because of a public backlash in 2000 that quashed the city’s plans for a recycling plant that would have converted wastewater to drinking water.

Gold hopes that there will not be a similar outcry this time around, and he says that the groundwater treatment process could include such processes as air stripping, granulated active carbon treatment, reduction coagulation filtration, and ion exchange, ensuring that the resulting water quality would be “absolutely exemplary.” He also anticipates the water to come at less cost than through importation and to be obtained in a way that is more environmentally responsible.

“It’s a really exciting time,” he says. “This is an acknowledgment that you can wait around for 30 years for a groundwater aquifer to be cleaned up through the Superfund process—and not have it get done—or you can take matters into your own hands and pump and treat.”



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