Ground-water contamination at five San Gabriel Valley sites is being assessed to ensure that leaks from underground chemical storage tanks do not reach drinking water supplies.
Most of the contaminated sites became public knowledge when businesses applied to the county Department of Public Works for permits to discontinue use of the tanks, where gasoline, oil or cleaning solvents had been stored.
Preliminary testing has disclosed some leakage at all the sites, but the pollutants have not seeped deep enough or spread far enough to reach drinking water stored in wells, said Josh Workman of the Regional Water Quality Control Board.
The tanks are in El Monte, South El Monte, Walnut, Industry and Rosemead.
Leakage Reports Required
Under Proposition 65, the toxic drinking water initiative passed in 1986, closure permits must include reports of possible leakage, said Joe Baiocco of the public works department.
The requests are referred to the water board, which recommends ways to clean up any contamination. Clean-up costs must be paid by the businesses.
"If the tanks are not in use anymore, they have to be closed out," Baiocco said. "Owners must take soil samples and drill borings to 40 feet to test for solvents in the ground."
Companies that discontinue use of the tanks without applying for a permit face fines of up to $5,000 a day for every day they are not in compliance, Baiocco said.
An undetermined number of closure permits have already been issued for other tanks in the San Gabriel Valley and elsewhere in the county, Workman said.
Seepage from many of the tanks has occurred over many years, he said. For example, Workman said, trichloroethylene, a metal-cleaning solvent that has been found in the ground under other tanks, was banned in the early 1960s.
However, so far, no contaminated has reached drinking supplies, said Steve Stewart of the county Department of Health Services. As a safeguard, wells constantly are being monitored.
Workman said there are various methods of cleaning up contaminated ground water, including pumping it from the ground and treating it with carbon filtration and applying bacteria to break down the contamination.
The owner must pay the clean-up cost, which can range from $50,000 to $1 million, depending on the extent of the problem, Workman said.
One of the closure permits is being sought by the Southern California Edison headquarters on Walnut Grove Avenue in Rosemead, where ethel benzene, fuel and cleaning solvents were stored in two tanks.
Company officials would like to continue using the tank, which holds gasoline for vehicles, said Mike Hertel, manager of environmental affairs for Edison. It was determined that the pumps, not the tanks, were leaking and contaminating the soil.
"We are working with the water board and hope they will say we can leave it alone because it is a minor problem," he said. "If we must do something, we could use microbes that decompose petrochemical fuels to clean up the soil."
"We are (closing) the solvent tank and will do the clean-up," he said.
Edison has investigated its 326 storage tanks throughout the state and will replace 60%, remove 30% and add additional monitoring systems to 10%, Hertel said. All the tanks will have alarm systems to detect leakage and a double-lined piping system.
The other sites on the list of closure applicants are an ARCO service station on Flair Drive in El Monte, the Phillips & Malone Production Machining Co. plant on Lidcombe Avenue in South El Monte, a Unocal service station on Valley Boulevard in Walnut and Hertz Penske Truck Rental & Leasing on Valley Boulevard in Industry.
At the ARCO station, 8,000 gallons of gasoline leaked from a tank. About 2,000 gallons of kerosene and used oil have leaked into the ground under the Phillips & Malone plant, which casts such parts as rotors and fittings for machines. Ground water under the Unocal service station is contaminated with an unknown amount of benzene and xylene, which are components of gasoline. Perchloroethylene, a metal-cleaning solvent, was found under the Hertz truck rental firm.
Officials at the businesses are trying to determine what clean-up steps are necessary and will present plans to the water board.