Removing an underground oil tank at Fairfield's Fire Station 5 earlier this year cost a total of $38,950. The same project at Fire Department headquarters/Station 1 on Reef Road is not proving so simple, the Board of Finance learned Tuesday.

According to a memo from Public Works Director Richard White, both of the fuel tanks removed behind Station 1-- a 1,000-gallon heating oil tank and a 2,000-gallon diesel tank -- had leaked.

"The 2,000-gallon diesel tank had leaked a significant amount of fuel over the years, resulting in significant contamination of the immediate soil and ground water," White said.

There is now an 8-foot-deep hole, measuring about 70-by-70 feet behind the station, where the tanks have been removed and contaminated soil excavated

Town boards had appropriated $152,000 for the tank removal at both stations, but the work at fire headquarters alone is now estimated to cost $431,382. With a contingency account bringing the total to $516,969, the estimated cost overrun, less the original $152,000 appropriation, is now $364,969.

Because of the extensive leaked fuel and the site's high water table, White said the state is requesting that the town not only remove the contaminated soil, but pump and filter ground water in the immediate area of the excavation to reduce the high level of hydrocarbons for the next two to four months. The state also wants wells to be installed around the perimeter to treat and monitor any ground water that potentially could leave the site. Those wells, according to White, might need to be treated and monitored for as long as one to two years before hydrocarbon levels are reduced to acceptable levels.

"We have gone significantly over" the original cost estimates, Fiscal Officer Paul Hiller told the finance board, adding that the overrun is entirely attributable to the cleanup. "For the short term we will expense it in the public works budget, but clearly there is going to be a need to come back -- although probably not before January -- for a special appropriation" to cover the extra expenses.

"I understand there was a major leak," finance board member Robert Stone said. "Is there a law that says we have to clean it up?"

Hiller said having been at the site, he doesn't see many options. And, he said, the town places requirements on private citizens and corporations to clean up similar leaks.

Stone asked that the board get a legal opinion on the town's responsibilities.

Interim First Selectman Michael Tetreau said he would arrange to get such a ruling, adding that there appears to be an underground stream at the site that carries water into the nearby marsh and that is a large part of the concern about wider contamination.