SOUTH GATE — In the last 13 months, chemical contamination has forced the city to close 5 of 11 wells that supplied half its water.
The latest closure came last month when tests showed that two wells exceeded the state Department of Health Services' recommended "action level" for tetrachloroethylene, a solvent used for degreasing.
The state calls for action--closing a well or cleaning the water--if the level of tetrachloroethylene, reaches four parts per billion. One South Gate well exceeded 10 parts per billion and the other had 14 parts per billion.
The traces of chemical found in the wells posed "a pretty low health risk," said David P. Spath, senior sanitary engineer for the state Department of Health Services.
Risk Is Minimal
"The four parts per billion means that you have a one-in-a-million risk in contracting cancer. If you were to drink two liters of water containing the four parts for 70 years, your chances of developing cancer would be less than one in 1 million," Spath said in a telephone interview from his office in Berkeley.
Rollie D. Berry, director of public works for South Gate, termed the water loss "pretty significant." He said the city is augmenting its own water supply with purchases from the Metropolitan Water District of Southern California.
When water use increases during the summer, he said, the city will have to greatly increase water purchases to serve its 71,000 customers. The city could conceivably double this year's $260,000 budget for Metropolitan Water purchases by the end of summer.
Cost of Water Double
The city pays $232 per acre foot, or 325,800 gallons, for purchases from Metropolitan Water, while it costs the city about $115 to $120 per acre foot to pump water from its own wells, Berry said.
Berry said he could not predict how this--as well as possible solutions to either treat the contaminated wells or find other water sources--would affect water customers' bills. But he said water rates, which are currently 65 cents per 750 gallons for both commercial and residential customers, could go up.
Both of the most recently closed wells are in South Gate Park. The wells were closed Dec. 23 after laboratory tests ordered by the city revealed the findings.
Two other wells in the park were closed in January, 1986, after levels of tetrachloroethylene and dichloroethylene were found to exceed state standards. Dichloroethylene is used to make plastic and other compounds. Both chemicals are made from petroleum.
First Closure in '85
Dichloroethylene was discovered in only one well at a rate of three-tenths part per billion, while the state action level is two-tenths part per billion, city officials said.
In November, 1985, the city closed its first well off Garfield Avenue after more than eight parts per billion tetrachloroethylene were found in that well.
The standards set by the health department are recommendations only, but Spath said the department "has received tremendous cooperation from utilities" to take contaminated wells out of service or limit their use, Spath said.
Under a state law that went into effect in 1985, the city and other water utilities are required to test for 48 organic chemicals commonly used in industry.
112 Wells Tested
There were 112 wells tested in the central water basin, which includes South Gate, Montebello, La Mirada and other southeast cities, said Thomas A. Salzano, field secretary for the Central Basin Water Assn. Of the 112 tested, 55 showed some traces of tetrachloroethylene or dichloroethylene, Salzano said. However, he said that "South Gate is a little unique for our area in that it showed a higher concentration of these organic solvents."
"We think this is an isolated problem," Salzano said, speculating that it might be traced to an industrial spill.
Berry said that the city staff is in the process of developing a specific proposal on how to go about investigating and identifying the source of the contamination. That proposal will be taken to the City Council.
Other Treatment Studied
Meanwhile, the city is looking at other ways to treat the well water and reopen the five closed wells, Berry said.
The council has approved a $70,000 contract with Boyle Engineering Corp. of Newport Beach to design a treatment facility that would remove or reduce the contaminants, Berry said. Construction costs alone for a treatment plant could be more than $500,000, he said.
The city could also consider reopening another well that has been closed for more than two years. The well is not contaminated but it has a tremendous amount of sand and silt.
"The cost of repairing the well would cost less than a new well," Berry said.
The city has also applied to the state for $3.3 million from the Safe Drinking Water Act of 1986 to help pay some of the cost of constructing a water treatment facility.
Additionally, two new wells are planned for the western section of the city as part of the development of a business and industrial park at the former General Motors assembly plant.
The city has applied for an $800,000 federal grant to help construct the wells. The city has not yet received an answer from any of the agencies on the funding requests.
The city is also having a financial study done by an Irvine consulting firm which is looking at how the city can best finance the capital improvements for the water system. That report is due in March.