Contaminants Found in 17% of Large Public Water Wells

A systematic check of California’s drinking water has identified measurable levels of harmful industrial and agricultural chemicals in 17% of large public water supplies that draw from wells, the state Department of Health Services reported Wednesday.

Many of the systems with contamination problems are in Southern California, where wells provide a high proportion of the water for household use.

State officials said, however, that consumers should not be overly alarmed.

They said that as a result of the survey the wells that pose the highest risk have been either closed or will be used only when peak demand requires them. In other cases, water from contaminated wells has been treated or blended with other water to lower the health risks.

In all cases where levels of contaminants exceeded the state standards, consumers were notified either by their water supplier or the state Health Services Department, the report said.

In releasing the preliminary results of the well-testing program that began last year, state Health Services Director Kenneth W. Kizer stressed that the findings were based on a sampling of wells most likely to be contaminated. As a result, he said, the results tended to magnify the problems.

He said short-term exposure to the chemicals does not represent a serious health threat.

Even so, he said, he views the findings “with concern, but I don’t think it’s alarming. In a number of respects it is reassuring. . . . We sampled the worst wells in the state and found that 88% didn’t have a problem.”

But Michael Paparian, chief lobbyist for the Sierra Club, took another view. “It is certainly many more wells than we imagined would show up with contamination when the testing program started. . ,” he said. “Certainly we’re hoping there will be a lot of attention to cleanup and no further degradation of existing water supplies.”

For some of the wells, concentrations of contaminants were 80 times the level considered to be a health risk.

The most commonly identified chemicals were perchloroethylene, or PCE, and trichloroethylene, or TCE, both industrial solvents found in more than 100 of the wells tested. Chloroform, a solvent and disinfectant, was found in 86 wells. All three substances have been linked to cancer in animals.

Of the 2,558 wells that have been tested for 30 organic chemicals since Jan. 1, 1984, 315, or 12%, were found to have some level of contamination. But only 115 wells, or 4.5%, had levels of one or more chemicals that the department believes represent a significant health risk to Californians.

The largest number of contaminated wells turned up in Los Angeles County, where 127 wells serving 50 water systems were found to have measurable amounts of toxic chemicals. Of those wells, 69 had levels of one or more contaminants that exceeded state guidelines or legal limits.

Kizer noted that reporting was incomplete for several counties, including Los Angeles, and that the actual numbers would climb even higher.

The latest findings also exclude wells that were shut down before the survey began--including large numbers of wells found to be contaminated by pesticides in the Central Valley and wells contaminated by industrial solvents in the San Gabriel Valley, Kizer said.

Larry McReynolds, assistant chief engineer of water for the Los Angeles Department of Water and Power, said the results did not indicate a growing problem, but rather a deepening awareness of existing contamination.

“We’re seeing contaminants that for the most part have been there for years and even decades, and we’re just now getting the results from the testing,” he said. “It is not an indication of a rapid spread in ground-water contamination.”

The system-by-system check of drinking water supplies began after a number of contaminated wells were discovered in heavily industrial and agricultural areas around the state.

The survey thus far has looked only at 832 large public suppliers that depend at least in part on well water. These systems provide water to nearly 50% of the state’s population.

The report listed the confirmed results for 753 of those systems.

Paul Jacobs reported from Sacramento and Larry Stammer reported from Los Angeles.