Officials of two San Gabriel Valley water companies that each have been forced to close two wells contaminated by industrial solvents say the closures will have little, if any, effect on service to customers because ample water is available from other wells.
The four wells were shut down after state health officials declared that the contamination would pose a cancer risk if the water were consumed untreated. Four other wells which the state also declared contaminated remain in use but the water is being blended and treated to meet health standards.
The new disclosures raise to 60 the number of wells in the San Gabriel Valley that are contaminated with chlorinated solvents at levels high enough to pose a health risk.
124 Wells Sampled
Clifford Sharpe, acting chief of the state health services' sanitary engineering branch, said the new findings are a result of a statewide program to test well water for 140 contaminants, including pesticides and volatile organic compounds. The state is sampling 124 of the 400 wells in the main San Gabriel Valley basin, which extends from Monterey Park to La Verne. An estimated 95% of the water piped to residents in the valley is drawn from the ground.
Sharpe said San Gabriel basin data still is being collected and analyzed, so it is too early to say whether the ground water contamination, first discovered five years ago, has moved, spread or intensified.
A high level of trichloroethylene (TCE) was first found in an Irwindale well in 1979. That discovery led to testing of other wells and within five months 37 wells were closed because of contamination by TCE and related compounds, primarily carbon tetrachloride (CTC) and perchloroethylene (PCE).
The newest findings involve TCE, found in two El Monte wells owned by California American Water Co., and 1,1-dichloroethylene (DCE) and 1,2-dichlororethane (DCA) found in six San Gabriel Valley Water Co. wells in Baldwin Park and La Puente.
Sharpe said DCA is a solvent used by paint manufacturers and DCE is used in plastics and in coating paper. TCE has been widely used as an industrial cleaning agent. Sharpe said all the compounds have been in such common use that it would be difficult to find where they leaked into the ground water.
Linn Magoffin, manager of California American Water Co. which serves San Marino and Duarte, said the two wells closed by his company are south of Valley Boulevard, near Baldwin Avenue, in El Monte. Magoffin said one of the wells already was closed because of a defective pump and the other was taken out of service when the state Department of Health Services reported test results to the company two weeks ago.
Magoffin said the TCE discovery was not surprising because the compound had been found earlier in other wells in the same area.
Gerald Black, general superintendent of the San Gabriel Valley Water Co., which serves parts of El Monte, South El Monte, La Puente, Baldwin Park, Hacienda Heights, Whittier, Monterey Park and San Gabriel, said the six wells in which DCE and DCA were found had shown TCE contamination earlier.
As a result of the new findings, Black said, two of the wells have been taken out of service and water from the four remaining wells is being blended with other water and aerated in a reservoir to disperse the contaminants into the air.
Black said the company has 24 other producing wells, so it should not face a water shortage. All water reaching customers will meet state health requirements, he said.
Cancerous in Lab Tests
State health officials said TCE, DCE and DCA have been shown to cause cancer in laboratory animals, but there is no proof that the compounds cause cancer in humans. However, the state recommends against drinking water that contains more than 5 parts per billion of TCE, 1 part per billion of DCA and 0.2 parts per billion of DCE.
The newly closed wells contained TCE concentrations of up to 9.6 parts per billion and smaller amounts of DCE and DCA.
The federal Environmental Protection Agency is developing a study to determine the sources of ground water contamination in the San Gabriel Valley and to outline a strategy for cleaning up or isolating the contaminants.