The Waitsfield Select Board okayed a plan for KAS Environmental Consulting in Williston to drill a water monitoring well on town office property so that the firm can continue monitoring ground water for contamination from a 1992 gas leak at the former Bonnette’s Garage, now the Mad River Valley Ambulance Service station in Waitsfield Village.
The board approved the new groundwater monitoring well at its January 29 meeting.
Leah Amerine, project manager for KAS Environmental Consulting, reported that after the leak was found the four former underground petroleum and diesel tanks were moved. She said that groundwater monitoring efforts had been underway per the Vermont Department of Environmental Conservation.
Since that time test wells on the MRVAS parcel and between it and the residence to the north have been conducted twice annually, per a KAS report. In July 2011 approximately 67 tons of petroleum impacted soils were dug and removed for off-site disposal during construction of the town’s water project and culvert installation on the west side of the property where it abuts Route 100.
KAS sampled again in May 2017, completing a round of groundwater sampling and a screening of the indoor air in the basement of the ambulance service and in the neighboring residence. Amerine said at that time engineers were only able to find one well and said that the readings in the basement of the station and the residence showed no petroleum.
“We recommended that the well network be reinstalled and resampled. We wanted to reinstall the ones between the station and neighboring property and proposed to add one on the town office side to see if the contamination had spread,” she said, noting that while petroleum doesn’t spread readily, it can spread through utility corridors.
In July 2019 KAS prepared a plan and work order for new wells and monitoring program.
“MRVAS asked us to put the plan on hold at that point and then COVID happened and in May 2023, the Vermont DEC reached back out with a site status inquiry and the new MRVAS president got back to us with an okay to proceed.
A December 6, 2023 KAS report on its supplemental site investigation (SSI) includes data on how the groundwater flows in that area. The executive summary of that investigation has groundwater flowing to the east/northeast at a hydraulic gradient of 2.1%. The September 7, 2023 visit that resulted in the report found that groundwater gathered from four wells showed that petroleum concentrations ranged from non-detectable in three with one well with detectable volatile organic compound concentrations.
“The results of the SSI indicate a dissolved phase plume continues to reside beneath the site in the immediate vicinity of the source area. Based on the measured northeasterly/easterly groundwater flow direction, the current monitoring well network is not believed to adequately define the dissolved phase plume,” the report states.
From that report came the recommendation to expand the testing to include the town office property to the west, which the town approved last month.
MRVAS bought the property in 1999 and according to Kevin Van Schaick, MRVAS rescue director, volunteer and facilities manager, the service looked into some of the suggested remediation, including removing soil throughout the site and replacing it with gravel. He said the state would have paid for it (as the spill is consider a Superfund site funded by federal grants to states).
“But there is no real advantage to us in coming off the Superfund site list unless we wanted to sell the property. It doesn’t cost us anything to be on the list,” he said.