Strict New Limit on PCE in Well Water Proposed

State health officials are proposing a tough new standard that would reduce the amount of PCE that is permitted in drinking water, a move that could force some San Gabriel Valley water producers to close wells or install costly treatment systems.

The new standard would halve the permitted level of PCE (perchloroethylene), a suspected carcinogen that has contaminated numerous wells in the San Gabriel and San Fernando valleys. The change would put 18 wells in the San Gabriel Valley and about 15 in the San Fernando Valley over the PCE limit.

Risk Would Be Cut

Pete Rogers, chief of the state health department’s water supply branch, said the proposal would reduce the already-low risk from PCE in water. He said it would be inappropriate for the agency to “condone even minor risks if we can do something about it.”

There is no federal standard for PCE in drinking water, although the U.S. Environmental Protection Agency is expected to propose a limit of 5 parts per billion. Under the state proposal, which could be adopted by the end of the year, the current advisory limit for PCE of 4 parts per billion would be replaced by a formal legal standard of 2 parts per billion, roughly a drop of PCE in 6,500 gallons of water.

Hearing Scheduled

A public hearing will be held in Sacramento on July 13 to establish standards for PCE and 13 other water contaminants. Local water officials said the PCE proposal is the only one that will present new compliance problems to area water systems.

In the Main San Gabriel Basin, whose wells provide 90% of the water supply for about 1 million San Gabriel Valley residents, EPA says 44 wells are now closed because of pollution by PCE and related compounds, such as TCE (trichloroethylene).

It is not clear how many more wells would be closed by changing the PCE limit because some contaminated wells could be kept open by blending their output with purer water. In other cases, utilities might elect to install treatment systems rather than close wells.

Low Levels

Gerald Black, operations manager of the San Gabriel Valley Water Co., which serves 120,000 residents, said 14 of his company’s wells have PCE, but the levels are so low that current drinking water requirements can be met by diluting with other water or through a simple aeration process.

But if the proposed standard is adopted, Black said, six wells will be out of compliance, and dilution and aeration will not keep them open.

The company cannot close the wells because it needs the water supply, Black said, and there is no way to get imported water to the area without building new pipelines. The only practical alternative, he said, is to install treatment systems at a cost of up to $1 million for each well.

3 Wells at Issue

Timothy C. Jochem, administrator of the operations division of Suburban Water Systems, which serves about 200,000 residents from Glendora south to La Mirada, said three of his company’s wells would be affected. The wells are in the Whittier Narrows area, where EPA is already considering a plan to build a treatment system that would remove PCE, TCE and other volatile organic chemicals.

Jochem said Suburban hopes that the new standard will not go into effect until the treatment system can be built.

“The timing is what could hurt us,” said Reginald Stone, Suburban senior vice president. “At best, we’re looking at a year away for the treatment tower.”

Robert Berlien, general manager of the Upper San Gabriel Valley Municipal Water District, said a number of water producers will oppose the reduced PCE limit at the July 13 hearing, but the fact that it is costly to comply with the proposal is not likely to alter the decision.

Berlien said that although the health department “may feel sorry for us,” its decision will be based on health, not cost, issues.

And one argument that the utilities can make, Berlien said, is that a tougher standard could result in reduced health protection if water mildly tainted with PCE is replaced by surface water containing trihalomethanes, a group of suspected cancer-causing chemicals.

‘A Little Baffling’

Duane Georgeson, the Los Angeles Department of Water and Power’s assistant general manager for water, called the proposed state standard “a little baffling,” given EPA’s leanings and scientific dispute over whether PCE causes cancer.

Although the Los Angeles Department of Water and Power meets the proposed PCE standard through blending, Georgeson said smaller utilities that lack blending capability might have to increase purchase of surface supplies from the Metropolitan Water District.

This, he said, would present a higher theoretical health risk because MWD supplies from the state Water Project and Colorado River are much higher in trihalomethanes than ground water.

Trihalomethanes are a group of suspected cancer-causing chemicals, including chloroform, that are formed when the chlorine or chloramine used in disinfection reacts with natural contaminants in water. Since surface water attracts more algae, animal waste and debris than ground water, more chemical disinfection is needed, and hence more trihalomethanes are formed.

Federal Standard

The federal standard for trihalomethanes in drinking water is 100 parts per billion. But according to some estimates, as many as 400 additional cancer cases could occur among 1 million continuous users of water containing that much of the trihalomethanes.

A person served that water theoretically would be more at risk than a consumer of water containing a bit more PCE than allowed under the proposed state standard. The EPA is reviewing its trihalomethane standard, and a bill before the state legislature would require a tougher California standard.

Rogers, the health department’s water supply chief, acknowledged the possible problem of trading ground water for surface water. But, he said, the state isn’t asking utilities to abandon their wells.

“The best solution, in all honesty, is to put treatment on the wells rather than switch to surface water,” he said.

PCE has been widely used as a dry cleaner and metal degreaser and at one time was used to decaffeinate coffee. Over the years, it has seeped into ground water through spills, leaks and deliberate dumping.

Although PCE is not very toxic, there is concern that continuous exposure through drinking water could slightly increase the risk of cancer. State health officials say a limit of 2 parts per billion in drinking water would present a cancer risk of no more than one in a million.

Since roughly 30% of all people--or 300,000 in 1 million--will have cancer sometime in their lives, the risk is very small. Such estimates do not take into account the combined effects of other trace pollutants in water, however, nor potential exposure to PCE through skin absorption in bathing or swimming or steam in a shower.

TCE Limits

Along with the PCE proposal, the state is proposing a standard of 5 parts per billion for TCE. The TCE proposal is unchanged from the current state action level and conforms with the federal standard. PCE and TCE are the mostly widely found organic contaminants in wells in the San Gabriel Valley and elsewhere in the state.

PCE was found in 199 of 2,947 wells sampled statewide in 1984 and ‘85, and TCE was found in 188 of them.