The U.S. Environmental Protection Agency has proposed construction of a $5.4-million treatment system for four water wells in the Whittier Narrows area, where suspected carcinogens are moving from one large ground-water basin toward another.
The treatment system is designed to provide pure water for 17,000 Whittier area customers of Suburban Water Systems of La Puente, and to stop pollutants from moving from San Gabriel Valley ground water through the Whittier Narrows into the Central Basin, which underlies the southeastern section of the county.
"It's a good deal for our customers," said Timothy Jochem, Suburban operations administrator. If the EPA does not act, he said, Suburban will have to build the plant or abandon the wells and buy imported water, which would result in water rate increase of 50% to 100%.
"The bottom line is that our customers will not see a rate increase," Jochem said.
The four wells are in Suburban's Bartolo well field, between the San Gabriel River and the 605 Freeway in an unincorporated area north of Whittier Narrows Dam. Water from the Main San Gabriel Basin, whose wells supply water to nearly 1 million people, flows underground at Whittier Narrows into the Central Basin, with wells serving 1.3 million people. The connection between the basins is a 2-mile-wide channel of shallow ground water, moving 500 to 1,000 feet a year.
In the San Gabriel Valley, about one-third of the wells have detectable amounts of trichloroethylene (TCE), perchloroethylene (PCE) and other contaminants. The Bartolo wells have low levels of TCE and PCE, but are thought to be in the path of an approaching plume of contaminated water and the levels could rise. Water with TCE levels above 5 parts per billion or PCE levels above 4 parts per billion is considered unsafe for drinking.
John G. Joham Jr., general manager of the Central Basin Municipal Water District in Downey, said water producers in the Central Basin fear that if the San Gabriel Valley ground-water pollution "is left unchecked, it could move into our area."
Joham said EPA's proposal for Suburban's Bartolo well field seems like "a step in the right direction" but he said he could not comment on details of the project until his agency's experts complete their analysis of the EPA plan.
The EPA will solicit public comment on its proposal at a hearing at 7:30 p.m. Wednesday at the Whittier Community Center Theater, 7630 S. Washington St., Whittier.
Next year the EPA will release a study evaluating other steps that should be taken at Whittier Narrows to clean up ground water and protect the Central Basin.
EPA's preliminary estimate of the cost of the additional Whittier Narrows work is $20 million to $70 million.
The EPA looked at nine alternatives for dealing with contamination of the Bartolo well field. The cheapest would be to abandon the wells and obtain imported water from the Metropolitan Water District, but the EPA rejected this idea because it would do nothing to clean up ground water.
The other alternatives analyzed by the EPA involve treatment systems. The system the EPA is proposing calls for construction of at least two, and possibly three, aeration towers to remove TCE, PCE and other organic compounds.
Water would be piped from the four wells to the top of 40-foot towers, then would flow downward as air is pumped upward, transferring the compounds from water to air through evaporation. The contaminated air would be channeled to a carbon filter system that would trap at least 90% of the contaminants. Remaining contaminants would be released into the atmosphere.
The EPA estimates it will cost about $4.38 million to build the system. In addition, the plan calls for spending $1.04 million to modify the four wells so water is drawn from levels with high concentrations of contaminants.
Jochem said his company has designed aeration towers in consultation with EPA's contractor on the project, CH2M Hill, and the U.S. Army Corps of Engineers, which controls Whittier Narrows.
The treatment system and the wells are within the flood retention area of Whittier Narrows Dam at an elevation that has a probability of being flooded once every 30 years. The EPA said it can incorporate flood-proofing features into the design.
Seeking another site would delay work and increase costs, the EPA said in its assessment of the project, and "this delay would be unacceptable given the public health and environmental threat posted by the ground-water contamination of the Bartolo well field."
The EPA is expected to decide in September whether to go ahead with the project. Jochem said it would take five to eight months to build the treatment towers.
In addition to the construction cost, the EPA estimates it would cost $809,000 a year to operate and maintain the system. The EPA would pay 90% of the construction cost and 90% of the operation and maintenance cost for 10 years. The state Department of Health Services has agreed "in principle" to pay the remaining 10%, although the amount has not been budgeted.
Jochem said Suburban Water would operate the system and be responsible for it after the EPA ends its involvement in 10 years.
He said it is not clear how long it will take to remove the contaminants, but the system could be operating well into the next century.