City officials have shut down four municipal wells that supplied 40% of the city's water after tests showed that the wells were contaminated with toxic chemicals at levels in excess of state health advisory standards.
The presence in the water of traces of tetrachloroethylene and dichloroethylene pose a "very, very low risk" to the health of residents of 74,800 residents, said Gary Yamamoto, district engineer for the state Health Services Department.
The City Council, in a prepared statement released Tuesday, said the level of contaminants is so low that it amounts to one drop in two backyard swimming pools, "We do not believe there is a health risk posed to the community," council members said in the statement.
Under a state law that took effect last year, the city and all other water utitilies are required to make a one-time test for 48 organic chemicals commonly used in industry, Yamamoto said. South Gate conducted its first test last October. After tetrachloroehtylene was found in a well, officials said they voluntarily decided to test all 12 city wells for contamination. The tests showed that three more wells were contaminated with tetrachloroethylene and that one of those wells also contained dichloroethylene, city officials said.
The source of the contamination is unknown, as is the length of time that the chemicals have been in the water, city and state officials said. The city has hired an Irvine engineering firm to conduct further tests on the wells and to monitor the pollution, city officials said.
Purchase of Water Possible
Closing the four wells leaves the city with enough water to get by at present, but this summer the city may have to purchase additional water from the Metropolitan Water District of Southern California, city officials said. The four wells that were closed supplied the city with 1.5 billion gallons annually, city officials said.
The city closed a well off Garfield Avenue on Nov. 5, after tests conducted by city workers found the well contained levels of tetrachloroethylene that exceed state standards. On Jan. 24, the city closed three other wells in the city's Recreation Park after levels of tetrachloroethylene and dichloroethylene were found to exceed state standards, City Atty. Bruce Boogaard said.
City officials, however, did not inform residents of the water problems until Tuesday, when they released a 10-page statement to the news media.
"We were taking the time to assemble the information and our solutions to the problem," Boogaard said. "There wasn't a problem as soon as we shut down the wells. And there was no reason to create hysteria until we had answers to the questions that we knew would be raised."
Mayor Bill De Witt could not be reached for comment.
Notification Not Required
Under state law, city officials were not required to inform residents of the low levels of contamination found in the wells because the city voluntarily closed them, Yamamoto said. Had the city decided to keep the wells open, it would have been required to notify residents, he said.
The levels of contamination in city wells exceed so-called state action levels at which the state expects utilities to take some kind of action to minimize public risk, Yamamoto said.
While the state's cutoff point for tetrachloroethylene is four parts per billion, tests detected the chemical's presence in four city wells at maximum levels of between 5.2 and 8.1 ppb in each of the wells, city officials said.
In the tests done by the city, dichloroethylene was discovered in only one well at a rate of three-tenths ppb, while the state action level is two-tenths ppb, city officials said.
Both chemicals are made from petroleum. Tetrachloroethylene is a solvent used for degreasing while dichloroethylene is used to make plastics and other compounds. Both chemicals are suspected carcinogens, Yamamoto said.
In an interview, Yamamoto said city officials could reopen the wells if they are tested again and are found to contain contaminants below state action levels. The city also could reopen the wells if the water is treated with a carbon filter to remove contaminants, or mixed with contaminant-free water to reduce pollution levels below state action levels, Yamamoto said.
If the city has to purchase additional water, the cost is expected to be minimal, Boogaard said. The city pays $235 per acre foot, or 325,900 gallons, to purchase water from the Municipal Water District, while it costs the city $215 per acre foot to pump water from its own wells, Boogaard said.