System should be on-line in 2½ years, official says
A Tucson Water official yesterday revealed the plans and the timetable for cleaning TCE from contaminated southside ground water.
Tom Jefferson, the city utility's water quality engineer, said the city will sink nine wells this fall as it starts work on the cleanup system.
The system, which could cost up to $30 million, should begin operating in about 2½ years, he said.
Officials believe the system will take at least 20 years to clean southside ground water to federal drinking-water standards, said Walter Burg, Tucson Airport Authority general manager.
Jefferson and Burg spoke during a news conference yesterday at which the U.S. Air Force deposited a $2.5 million check into a TCE-cleanup trust account.
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Air Force Col. Ray Swenson said he also paid the Environmental Protection Agency nearly $1.67 million yesterday for studies the agency and its consultants conducted to determine the extent, severity and sources of the TCE pollution.
TCE is trichloroethylene, an industrial solvent that causes cancers in laboratory animals. The EPA found TCE in southside ground water above the federal limit in 1981, forcing Tucson Water to close nine wells by 1986.
TCE contaminates ground water in a finger-shaped plume up to a mile wide and more than 4 miles long. The pollution plume reaches from Hughes Aircraft Co.'s Air Force-owned missile plant south of Tucson International Airport to Michigan Street.
The Air Force built a $28 million treatment system at the Hughes plant that is cleaning ground water today south of Los Reales Road.
The EPA, in 1987 after several Superfund studies, named Hughes and Airport Authority tenants, including McDonnell Douglas Corp., as sources of pollution north of Los Reales.
The EPA also named the Air Force because it owns the missile plant, the Airport Authority because it leased airport facilities to polluting industrial tenants, and the city because it owns the airport land.
A federal court Superfund agreement was filed In September, spelling out the cleanup terms:
• The Air Force pays $2.5 million and the EPA bill.
• McDonnell Douglas pays $500,000.
• The Airport Authority will pay $2.5 million in the future.
• The Air Force and the Airport Authority will split all costs beyond $5.5 million.
• Tucson Water oversees construction and operates the cleanup system.
U.S. District Judge Richard Bilby signed the cleanup agreement this month.
Jefferson said the new cleanup system will resemble the Air Force's $28 million system to the south.
"We'll have water extraction wells, a collection system and treatment with an air stripper," he said.
An air stripper is a tower in which tainted water is pumped to the top and exposed to air as it trickles down through packing material. TCE molecules evaporate.
The treated water is pumped into the Tucson Water system.
A Tucson Water contractor is expected to design the collection system and stripping tower by year's end, Jefferson said.
Jefferson said the stripping tower will have filters, most likely of carbon, to trap the TCE so it does not pollute the air. Contaminated carbon filters usually are incinerated, sometimes on-site, he said.
Construction of the system could begin in mid-1992 and be complete in a year, Jefferson said.