Lantmans IGA

A former gasoline underground storage tank (UST) system has been identified as the source of methyl tert-butyl ether (MTBE) in the bedrock aquifer in the Town of Hinesburg. MTBE had been detected in a nearby industrial water supply since at least 1999. After this industrial operation ceased in 2008, the groundwater elevations and flow direction changed, resulting in migration of MTBE toward the former Town wells. MTBE has been detected in the two former Town of Hinesburg supply wells since mid-December 2008.

The extent of contamination and the mechanism by which contaminants enter the bedrock aquifer have been identified as strong downward vertical gradient through a fractured clay system coupled with a dewatered soil/bedrock interface caused by pumping influences of major water supply wells. A remediation system consisting of multi-phase extraction (MPE) and groundwater extraction (GES) was installed at Lantman’s in March 2008 to recover petroleum mass in the subsurface and to mitigate the persistent flux of contaminants to the bedrock aquifer. When in operation, WHEM routinely monitored the former Town of Hinesburg Water supply for the presence of benzene and MTBE. The results indicated this system operated successfully, preventing the migration of contaminants to the Town water supply above applicable standards.