Official of DWP Calls Valley’s Water Safer Than Alternative

Contaminated water from wells in the San Fernando Valley is safer to drink than the water that would have to be used if the wells were shut down, an official of the Los Angeles Department of Water and Power said Tuesday.

Some of the Valley’s well water is contaminated with low levels of suspected cancer-causing solvents. About 15% of the city’s water supply comes from Valley wells, many of which contain trichloroethylene, or TCE, and perchloroethylene, or PCE. TCE is used in dry cleaning and industrial degreasing.

Water from these wells is blended with water from uncontaminated wells and from the Owens Valley Aqueduct to dilute the contamination before delivery to customers. Nonetheless, TCE levels in water reaching consumers have sometimes exceeded the state’s recommended limits.

Aqueduct Water Worse

The Valley well water, however, contains far less of a more dangerous group of chemicals than is in water from the California Aqueduct, said Laurent McReynolds, DWP’s assistant chief engineer of water.

If the Valley wells were closed, Los Angeles would have to rely more heavily upon water from that aqueduct, which originates in the Sacramento Delta and now supplies only a fraction of the city’s water, he said.

“If we turned off the wells that have TCE in them, we’d end up supplying the public with water of a higher risk,” McReynolds said.

The DWP engineer made the water comparison at a hearing sponsored by the Assembly Environmental Safety and Toxic Material Committee on Thursday in Rosemead. The purpose of the hearing was to assess what progress, if any, federal, state and local government agencies have made in handling the ground-water contamination problem in the San Fernando and San Gabriel valleys.

Suspected Cancer Agent

The group of chemicals present in the California Aqueduct water is called trihalomethanes, which are formed when chlorine added for purification combines with natural organic substances already present. Trihalomethanes are a suspected carcinogen.

The California Aqueduct water generally contains 80 parts per billion of trihalomethanes, contrasted with only 20 to 30 parts per billion in Valley ground water. Water from Owens Valley Aqueduct, which supplies Los Angeles with most of its water, contains 30 to 40 parts per billion of trihalomethanes.

The state limits trihalomethanes in water to 100 parts per billion. At that level, 400 people out of a million have a chance of contracting cancer by drinking the water, according to government standards.

The hazard posed by TCE is not as great, McReynolds said. The state recommends that TCE in drinking water be limited to less than 5 ppb. At that level, a person who drinks two quarts of the contaminated water daily for 70 years has a one in 1 million chance of contracting cancer, according to state calculations.

During the hearing, committee members expressed frustration that the identification of ground-water contamination sites and cleanup has been slow. Committee chairman Sally Tanner said she hoped the hearing would “motivate agencies that have been dragging their feet.”

Acknowledging Tanner’s frustrations, Mark E. Leary, an engineer with the state’s Toxic Substance Control Division, said, rather sheepishly, “I’m not here to say we’ve made tremendous progress.”

It would be appropriate, he added, for the state “to eat a little humble pie.”