Friday, October 6, 2000
Mount Carlisle to rise from Center's Little Dig
Tony Mariano of the water quality/resource committee was busy on the evening of September 26, advising both the board of health (BoH) and board of selectmen on the Department of Environmental Protection's plans for the cleanup of the Daisy's site. The soil has been contaminated with the gasoline additive methyl tertiary butyl ether (MTBE) from leaks from gas tanks that have since been removed.
The selectmen had been asked to respond to a request by the DEP to access the town-owned parking lot next to Daisys to park equipment for the purpose of pumping out, filtering, and discharging water from the site. The board had delayed approval pending resolution of worries about the safety of the cleanup plan.
Enthusiastic that the DEP is finally resolving the problem which has caused MTBE to appear in town center wells, the selectmen approved the request.
Mariano indicated to both boards that the DEP has responded satisfactorily to concerns regarding soil management, fumes, safety of the site, traffic management, and notification of abutters. He therefore recommended approval of the access to town land.
According to the DEP letter, the process will include:
· excavation of 1500 cubic yards of clean soil (above contaminated)
· excavation of 1500 cubic yards of contaminated soil (depth of 12 to 18 feet)
· dewatering to permit excavation below the water table installation of two well couplets to replace damaged wells, and
· monitoring of ground water for one year.
Mariano recommended that the selectmen add the provision that clean soil not be stockpiled on the site, so as to force the DEP to haul soil away quickly.
Due to logistical difficulties in trucking such large quantities of fill from the center of town while excavation equipment is still at the site, the contaminated soil will be stockpiled behind the Daisy's building for what the DEP hopes will be one week. The contaminated soil will be placed on top of plastic and will be covered with more plastic, which will be weighted in place.
Mariano noted that the soil stockpile is expected to be about 20 feet high, dubbing it "Mt. Carlisle." "The soil will be piled on the leaching field/ septic tank area behind Daisy's. Will the weight of the soil and the heavy equipment damage the system?" Mariano asked the board of health. After a few calculations and confirming that the area in question is paved, BoH engineer Rob Frado and chair Steve Opolski agreed that the weight should not affect the septic system.
Risk of water pollution small
At the selectmen's meeting, Lowell Street resident Tom Lockwood expressed concern over the removed water which, after filtration, will be released into storm drains that drain into wetlands behind the police station. Echoing the selectmen's earlier concerns, he asked whether there is a risk of releasing polluted water into the environment.
Mariano responded that fluid out of the tanks would be analyzed twice a day, and called the methods used by the DEP for filtering "very adequate for the concentrations we're looking at."
Mariano described the de-watering procedure in detail to the board of health. The process involves removal of soil down to two feet below the low water level. "Water will then be pumped out of the excavation site into a fractionization tank and through two 500-pound carbon filtering vessels, after which it will be discharged into the storm drain. Treated water will be sampled for analysis on days 1, 3, 7 and 14 of the process." Mariano also noted that the DEP will monitor groundwater in the area for a year.
Mariano told the selectmen the risk is small - "we're not doing something that hasn't been done a thousand times before."
Board of health member Martha Bedrosian expressed concerns about the safety of storing the contaminated soil on site, fearing dispersal of the volatile organic contaminants. Mariano noted that air quality monitoring will be performed during excavation and that the plastic above and below the stockpiled soil is meant to prevent erosion onto neighboring sites.
Out by Halloween
The project began October 2 and is planned to be completed by October 13, with activities from 7 a.m. to 4 p.m. each day.
A police detail will be at the site and snow fencing in place during excavation. Excavation is expected to last until October 13, and the selectmen have told the DEP it must end by October 23 at the latest.. "With the kids that go around there on Halloween, we've got to have them out of there by then," said Mariano.
© 2000 The Carlisle Mosquito