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State sops up pollution at gas station

(ran PW edition of PT)

Along U.S. 41, just south of the entrance to Bud McKethan Park, is an undistinguished, boarded, concrete block building that once housed a Charter service station.

The building's innocuous appearance, though, is deceiving. In the soil and water below is probably the worst case of petroleum contamination in Brooksville's history.

Researchers found soil polluted with 20 times what the state considers an acceptable level of gasoline, and groundwater with 220 times the acceptable level of a far more toxic gasoline-related chemical, benzene.

The cleanup is expected to cost the state about $200,000.

"There were a couple of borings that were very hot. Essentially they were off the scale," said Brian Dougherty, an administrator with the state Department of Environmental Protection, referring to the soil readings.

He added that though the state has cleaned up the pollution left by hundreds of old gas stations, usually only the soil is involved.

"It's unusual for the contaminants to reach the water table," he said.

"We've never had contamination to this extent," said Stan DeAngelis, the city's building official.

There is some positive news, though. Despite the high concentration of gasoline and related chemicals, what state environmentalists call the "plume" of contaminants has not spread far beyond the station's property line, either in the water or in the soil.

It represents no threat to the city's groundwater supply and is not a health risk of any kind, said Scott Bell, who has overseen the project for DEP.

Also, he said, neither the city nor the current owner of the property, Circle K Corp., will pay for the cleanup. It falls under the state's "early detection incentive" program, which was initiated 10 years ago.

The program, financed primarily by fines levied on other polluters, gives immunity to the owners of service stations who report contamination on their property.

The state first heard of the contamination at the Charter site from Circle K in November 1988, said Ann Vry, a public relations manager in the company's Arizona headquarters.

The company had bought all of Charter's holdings the month before and inherited the site, she said. The state approved it for the early detection program in March 1989, she said. Circle K operated a store there until 1990, she said. It is now trying to sell the property.

As it does in most such cases, the state handed over both the assessment of the pollution levels at the gas station, as well as the eventual cleanup, to an Altamonte Springs company, Rust Environment & Infrastructure.

Rust recently completed the first phase, which cost $112,000, and is applying for the city permits it needs to begin the second. Though it is too early to estimate the cost for what Bell calls the "wrap phase," the bill probably will come to more than an additional $70,000, he said.

Among the more dramatic findings in the first phase, according to Dougherty: One soil sample had 10,000 parts per million of gasoline contamination. The state considers anything above 500 parts per million too high.

Though the water table is about 80 feet below the surface at the station, Rust measured 220 parts per billion of benzene in one water sample last June. Any measurement higher than 1 part per billion is considered unacceptable, Dougherty said. Benzene, in general, is the chemical that is causing the agency the most concern.

"That tends to be the driving contaminant in our petroleum cleanups," he said.

Another disturbing soil sample showed unsafe levels of gasoline pollution between 18 and 26 feet deep, then several feet of clean soil. "Then at 44 feet it pops up over 500 parts per million again," Dougherty said.

But, he added, readings just a few feet away from the property "came up clean," Dougherty said.

Bell attributed that to the dense soil and the thick wall of limestone in the area that prevent groundwater from moving as rapidly as it does in most other parts of the state.

Cleaning the contamination caused by petroleum tanks is often a simple matter of digging up the tanks and the surrounding soil, Bell said.

Because the contaminants go deeper at the Charter site, and because the groundwater also is polluted, Rust will be required to use far more sophisticated methods.

The Charter station actually had eight tanks, Vry said. Circle K already has removed three fiberglass tanks originally installed in 1986.

Five older steel tanks, which seem to be the source of most of the pollution, have been filled with sand for several years.

Rust will remove those tanks and clear the property. Workers then will cover the affected area with plastic so they can create a vacuum to suck the contaminants from the soil.

Rust's plan calls for digging five air intake wells and 17 "vapor recover wells" in the polluted area. Pumps then will draw air through the soil and bring the gasoline vapors with it. The air then is purified in a carbon filter.

Similarly, Rust will pump out the contaminated water, purify it, and either return it to the aquifer or transfer it to a retention pond.

One thing that will not be done is finger any villain who caused the pollution. Neither the state nor Circle K knows who installed the tanks or when. The early detection program was instituted with the awareness that past laws and the specifications of gasoline tank manufacturers were not adequate to prevent leakage. The program's aim is to clean up pollution, not prosecute polluters.

"Basically, it's not set up to determine blame, unless someone is really blatant about something," Bell said.