As the Los Angeles River flows past Griffith Park, about 80% of its volume is effluent from the Tillman sewage treatment plant in the Sepulveda Basin.
Most of the water courses through the concrete-lined channel and out to sea. But near the park, millions of gallons a day percolate through unlined sections of river bottom and into ground water from which Los Angeles and Glendale draw part of their domestic water supply.
To Los Angeles water officials, this is an opportunity, not a problem. They hope to increase the recharge of underground water reserves already taking place by diverting river water into earth "spreading grounds"--where it will filter through the ground, theoretically cleansing it to near-drinking-water quality.
Would Serve 125,000
Ultimately, the Los Angeles Department of Water and Power hopes to divert 25,000 acre-feet per year of water from the river--enough to serve the needs of about 125,000 people.
"If we've got good quality reclaimed water, we don't want to waste it," said Bob Haw of the DWP. River diversions "would be a valuable way to further conserve our existing water supplies, especially since reclaimed water would be available even during dry years," according to a DWP report.
Actual use of the water is years away, however. For now, the DWP merely wants state approval to run a small-scale test of the cleansing power of the sandy soil beneath its Headworks Spreading Grounds--a series of basins wedged between the river, Griffith Park and Forest Lawn Memorial Park.
The idea of drinking treated sewer water is not so new. Since the 1960s, the Los Angeles County Sanitation Districts have been spreading effluent from water reclamation plants in Montebello and Pico Rivera to replenish underground water from which numerous cities and water districts draw part of their supplies. In Orange County, water from the Santa Ana River containing effluent from upstream sewage plants in Riverside and San Bernardino counties is also being diverted for ground-water recharge.
Moreover, officials say the Tillman effluent, which averages 40 million gallons a day, is cleaner than most water in the river--such as urban storm runoff that flushes oil from roads. Tillman is required by its state discharge permit to produce effluent clean enough to swim in, which is short of drinking water purity.
The DWP expects, perhaps as early as this week, to formally request approval from state health and water quality officials for a $250,000 pilot study. Plans call for pumping about 650,000 gallons of water a day from the river to the Headworks basin beginning later this year. The water would seep through the ground toward the river at about 1,000 feet per year--taking a year to reach an extraction well that would pull the water out of the ground before it could blend with ground water flowing to nearby city drinking-water wells.
Water would continuously be spread, extracted and analyzed for chemicals, metals and bacteria before being returned to the river.
Diversions Could Follow
If the experiment produces water that is fit to drink--or would be with minor additional treatment--large-scale diversions could follow.
In parched Southern California, with its booming population, almost everyone involved in the issue supports the idea--in principle.
State water quality officials are on record in support of reclaimed water use. And Dennis Dasker, supervising engineer with the Los Angeles Regional Water Quality Control Board, said the agency likely will approve the pilot project if it is convinced that the river water "would not escape beyond the influence of their extraction well."
Barbara Fine, a vice president with the Federation of Hillside and Canyon Assns. and longtime activist on drinking water issues, said her group supports "the fullest possible use of reclaimed water."
But she warned that a successful pilot study would not guarantee the safety of large-scale use of river water. Water in the pilot study could "come through with flying colors" because the soil can cleanse the modest volumes of water involved, Fine said.
But she questioned if the soil would continue to be an effective filter with "the constant saturation that will ultimately be the case when this water is spread" on a grand scale.
The need to avoid polluting ground water during the pilot study is particularly strong because the U.S. Environmental Protection Agency and several polluting industries are beginning to spend millions to clean it up.
About 15% of the Los Angeles water supply comes from wells in North Hollywood and along the Los Angeles River, many of them tainted by low levels of trichloroethylene (TCE), perchloroethylene (PCE) and other industrial solvents. The cities of Burbank, Glendale and the Crescenta Valley County Water District also draw part of their water from tainted wells. The most contaminated wells are not being pumped, and mildly polluted water from other wells is blended with fresh supplies to meet health standards.
About 20 Los Angeles and Glendale drinking-water wells are situated downstream from the Headworks Spreading Grounds along unlined reaches of the river. When most of the flood control work was done in the 1930s, those sections were purposely left open to promote ground-water recharge.
Clean Enough to Swim In
But today, nearly the entire flow in these areas is treatment plant effluent. In addition to the Tillman discharge, 25 million gallons a day pour in below Headworks from the Burbank and Los Angeles-Glendale water reclamation plants, whose effluents are also supposed to be clean enough to swim in.
According to DWP estimates, percolation through the unlined segments probably ranges between 7 million and 15 million gallons per day.
Based on data from the city wells, "we don't see any adverse effects" from the increased flow of treatment plant discharges, said Bruce Kuebler, engineer in charge of the DWP's water quality division.
"I don't have any information that it's causing any kind of negative impact," said Gary Yamamoto of the state Department of Health Services' public water supply branch, referring to the percolation of effluents through the river bed. "Nobody's really looked at it," he said.