The Carlisle Mosquito Online

Friday, July 2, 1999


Effects of DPW gas spill worse than expected

Any hint of groundwater contamination rings alarm bells in Carlisle and galvanizes officials from both town and state. Such has been the case with the unexpectedly stubborn oil spill problem at the department of public works yard off Elizabeth Ridge Road.

Engineer Chris Mariano of ENSR, the firm retained by the town to remedy the situation, received the go-ahead for a cleanup program from the Carlisle Conservation Commission at the board's regular June 24 meeting. As the potential seriousness of the challenge increased, so has the complexity of the proposed remediation.

Mariano's brief history of the project began with the removal of the old underground oil tank in September 1998, as required by state law and local bylaw. When soil contamination was discovered in the area under the tank, the state Department of Environmental Protection (DEP) approved removal of 300 cubic feet of soil. Although water was found to be present, there was no evidence of groundwater contamination at that time. A recheck in January 1999 uncovered evidence of contamination, including a sheen on the surface of the nearby wetland. ENSR's task then was to find the source and extent of the problem. Test pits determined that the fuel infusion was still confined to the area surrounding the old tank.

Acting under the state's Immediate Response Action requirements, Mariano proposed to divert all existing piping around the offending area in order to address the underlying problem. He further recommended a rather exotic new technique that calls for creation of two wells to facilitate injection of microsorb microbes to ingest the oil. Oxygenated water will also be introduced to help the tiny organisms do their job. Marino estimated that the clean-up should be accomplished over the next 18 to 24 months.

The relatively new technology has been approved by the state. Declared Mariano, "We went for it because the alternative is to dig out all the soils, de-water the area and fill it in with clean dirt, a very costly process."

Commissioner Kathy Kiely inquired whether the contamination is migrating. Mariano admitted that it is, "but very slowly." He said this is not considered a major release and that the nearest residence is a reassuring distance away.

With words of encouragement and some evidence of crossed fingers, the commission approved the proposed plan. A standard order of conditions was issued with a special addendum requiring that hay bales which have been in place for several months be inspected and changed regularly.

1999 The Carlisle Mosquito