MCP Response Actions

BETA provides the Town of Lakeville with environmental consulting support for the response actions related to a release of gasoline from underground storage tanks (USTs) removed from the Department of Public Works (DPW) garage located on Montgomery Street. The southeast portion of the site is located within a Surface Water Supply Zone A. Two private water supply wells are located within 500 feet, requiring contaminant concentration in groundwater to achieve MCP Method 1 GW-1 groundwater standards.

Initial assessment and remediation activities were conducted by other consultants, starting in 1998 with the detection of gasoline in soil and groundwater. In 1999, volatile petroleum hydrocarbons (VHP) were detected in downgradient private drinking water wells, well above GW-1 Standards. These residences were subsequently connected to the Town’s water distribution system.

Non-aqueous phase liquid (NAPL) was detected in site monitoring wells in 1999 and an air sparging/soil vapor extraction and catalytic oxidation (AS/SVE/CATOX) system was installed at the site in September 2000 under an Immediate Response Action (IRA). In 2008, the Town retained BETA to provide an assessment of the remediation system and ongoing LSP services. Although operation of the AS/SVE/CATOX system resulted in significant removal of gasoline from the subsurface, BETA concluded that the effectiveness of the AS/SVE/CATOX system had declined significantly due to equipment failures, geologic constraints, groundwater levels, and other factors and that applicable Method 1 GW-1 Standards could not be achieved within a reasonable time frame, or at a reasonable cost, with ongoing operation of the system. Therefore, a decision was made to terminate operation of the system in the fall of 2008.

Since that time, ongoing IRA activities have included subsurface investigations, private well sampling and groundwater sampling. In February 2014, BETA submitted an IRA Completion and Class C Response Action Outcome (RAO) statement. The contaminant plume has shrunk significantly, with GW-1 exceedances detected in only the two monitoring wells located close to the former USTs. No contaminants were detected in a downgradient private drinking water well. A Substantial Hazard Evaluation (SHE) was completed and concluded that a substantial hazard is not posed to human receptors under current site conditions and uses. Ongoing activities include continued monitoring of groundwater and assessment of current soil conditions in anticipation of achieving a Permanent Solution.