Each day, 35 million gallons of water pour from the city's new sewage-treatment plant in the Sepulveda Basin into the concrete-banked Los Angeles River. The water runs east for seven miles and, as it passes Forest Lawn Hollywood Hills Memorial Park, flows over a decaying, partially dismantled dam before it courses to the sea.
The Los Angeles Department of Water and Power, eager to ease--even slightly--the growing strain on its limited supply of drinkable water, has planned two projects to capture some of that steady stream of waste water and put it to use.
Water officials have proposed a pilot project to test whether treated water from Donald C. Tillman Water Reclamation Plant might someday be used to replenish ground water beneath the San Fernando Valley, which provides 15% of the city's drinking water.
In the proposed experiment, the deteriorating dam would be replaced, and river water would be diverted into the Headworks Spreading Grounds, an expanse of shallow basins near Forest Lawn where water is allowed to percolate into the earth.
Approval of Greenbelt Project Expected
The DWP is also expecting final approval of its Los Angeles River Greenbelt Project, which would provide up to 2 million gallons of treated waste water a day for irrigation. Los Angeles and Glendale already use some reclaimed water.
In this project, conceived in 1982, water flowing from the Tillman plant would be diverted by the same dam into a separate basin, where it would be treated and then sold--for watering only--to four customers: Forest Lawn Memorial Park, Mt. Sinai Memorial Park, the Lakeside Golf Club and Universal Studios. All four facilities now irrigate their expansive grounds with water from the city's regular supply.
The proposals are being assessed by county and state health agencies, which monitor any use of reclaimed water to ensure that there is no risk of the water carrying disease or potentially hazardous concentrations of industrial chemicals.
The DWP started diverting water from the Los Angeles River to the Headworks Spreading Grounds in 1917. The technology used to block the river flow changed in the 1950s from swinging wooden barriers to an inflatable rubber dam, but the idea remained the same: to recharge the natural subterranean reservoir locked in layers of sediment beneath the Valley with water that would otherwise run to the sea.
By 1982, the rubber dam had deteriorated until it needed replacement, said Walter Hoye, director of water engineering for DWP. But DWP left the dam alone, having planned to take it out of service anyway because, he said, the river was scheduled to be taken out of service soon as a source of drinking water.
Plant's Operations Halted Diversion
In the Sepulveda Basin, construction was about to start on the Donald C. Tillman Water Reclamation Plant, to treat the sewage of the West Valley and dump the treated waste water in the river. The DWP, once the plant was operating, would not be allowed to divert water from the river to replenish ground water.
The Tillman plant, which achieved full operation in September, 1985, removes most of the particles that reduce the clarity of the water, kills viruses and bacteria, and lowers concentrations of most hazardous chemicals to below limits set by the state for drinking water, said Robert Krivak, assistant plant manager.
The eight-stage treatment process at Tillman was not designed to meet all drinking-water standards, Krivak said, but it produces water that meets all standards for irrigation.
The turbidity, or cloudiness, of reclaimed water from Tillman and other waste-treatment plants is usually at least twice that allowed for drinking water, Krivak said. Because about 10% of the sewage treated at Tillman comes from industrial plants rather than homes, it occasionally contains a variety of potentially toxic compounds, including metals such as chromium and other chemicals, including cyanide, Krivak said.
Most of these chemicals are removed by the treatment process, but some are actually created during the process. For example, when some benign compounds are exposed to chlorine, they produce hazardous byproducts, said Peter Rogers, chief of the sanitary engineering branch of the state Department of Health Services.
Both DWP proposals to reuse Tillman water would require that the deteriorated rubber dam in the Los Angeles River below the plant be replaced. The river water diverted by the dam could be channeled either into a clay-lined basin that would be dug for the project or onto the spreading grounds for the pilot project to recharge ground water, said Winston Wu, a DWP water resources planning engineer.
Wu said that DWP is seeking bids for a new dam, which is expected to cost about $500,000 and resemble the previous rubber dam, a tube of rubberized fabric across the cement river bottom that can be inflated, either with air or water, to divert river water into adjacent basins.