By lowering a television camera down a 600-foot well at Whittier Narrows, investigators working for the U. S. Environmental Protection Agency last week began the first major effort to chart the depth of ground-water pollution in the San Gabriel Valley.
The work will help the EPA devise a plan to keep chemical compounds that have invaded San Gabriel Valley wells from moving through Whittier Narrows into the Central Basin in the southeastern part of the county.
Neil Ziemba, manager of the EPA's Superfund project on ground-water problems in the San Gabriel Valley, said investigators know where the major areas of pollution lie from analyzing tests taken at the hundreds of wells that dot the valley. But since each well collects water from many different depths, new work is needed to pinpoint the levels at which contaminants are found.
Ziemba said that if pollution is found only at certain levels, then that water could be extracted and treated, improving the efficiency of the clean-up process. It would be quicker and cheaper to treat only water that is contaminated, leaving the water at the uncontaminated levels alone, he said.
The test results will show whether contaminants, mostly industrial solvents, are confined to shallow water or have seeped to deeper levels.
Five wells will be tested at a cost of $100,000. EPA officials hope to have some results within a few weeks.
The contaminants are invisible, present in tiny amounts that can be measured only by sophisticated laboratory tests. But the cameras used last week enabled investigators to examine the condition of the first well, including the perforations that allow ground water to enter it.
Mark Henry, a hydrologist, said information gleaned by television will be used to determine where to seal off portions of the well so that water samples can be collected at various depths and sent to a laboratory for analysis.
This well belongs to Suburban Water Systems and is in the Whittier Narrows conservation area near Pico Rivera. Timothy C. Jochem, administrator of the company's operations division, said the well is one of four in the area that serve 18,000 customers in Whittier and neighboring communities.
People have been drawing water from wells in that area beside the San Gabriel River since the turn of the century, Jochem said. The water quality has always been high, but low concentrations of trichloroethylene (TCE), a solvent that is a suspected carcinogen, have been detected recently.
The TCE levels are so low that the water has remained drinkable under state and federal regulations, Jochem said, but Suburban has begun planning treatment systems to remove TCE and other contaminants in case the water quality deteriorates. He said it would cost $1 million to $2 million to install systems to treat water from all four wells.
Nearly a mile north of the Suburban property, the San Gabriel Valley Water Co. has a well that has been closed for about five years because of contamination from both TCE and perchloroethylene (PCE), an industrial and dry-cleaning solvent. An EPA contractor will take samples from that well this week to find the depth of the pollution, and later three other wells in the area will also be sampled.
Gerald Black, operations manager for San Gabriel Valley Water Co., said his company has not devised a treatment plan for its well but is awaiting results of the EPA tests to find out whether it is practical to bring the well back into service. "We'd be thrilled if we could get the well back on line," he said.
Black said his company has bypassed ground-water pollution in Baldwin Park and El Monte by drilling new wells 1,000 feet deep, sealing off the top 500 or 600 feet and drawing only deep water. Jochem said Suburban, too, has been drilling deep wells to avoid contaminants.
But Ziemba said deep wells may make the problem worse, drawing water down and allowing contaminants to seep further below the surface, which would "make cleanup that much more difficult."
While the EPA is continuing to look at the overall problem of ground-water contamination in the San Gabriel Valley, Ziemba said the Whittier Narrows is receiving special attention because ground water is channeled through there to the Central Basin. Ziemba said that some wells in the Central Basin have contaminants but that the problem is much worse in the San Gabriel Valley, where 70 wells have water that cannot meet federal standards.
Ziemba said ground water moves through Whittier Narrows at a rate of about 500 to 1,000 feet per year.
Exactly how TCE, PCE and other contaminants have found their way into ground water in the San Gabriel Valley is unknown.