Water Quality Outside of Capture Zone Improves with System Operation

A CERCLA site in Central Maine is currently being addressed with source control via containment based on a pump and treat system designed using groundwater modeling of the flow system in fractured bedrock. Appropriately targeted field data collection efforts and monitoring allowed the development of a comprehensive fate and transport model vetted and accepted by State and Federal agencies for use in evaluating plume containment operations. A Technical Impracticability (TI) Evaluation conducted to address whether Source Area Groundwater could be restored to drinking water standards within a reasonable period of time supported the conclusion that a TI Waiver of chemical-specific ARARs would be appropriate for the Source Area portion of the Site.  The final remedy selected for the site included Hydraulic containment of the Source Area Groundwater based on the groundwater flow model and a TI Waiver for the Source Area Groundwater, coupled with continued monitoring of and institutional controls for the Non-Source Area Groundwater. Operational groundwater piezometric monitoring results show strong agreement with model predictions. The data collected to date indicate that capture of the source zone effectively controls migration from the Site. Groundwater quality data from the first Five-Year review since the system became operational suggest that target VOC concentrations in Non-Source Area Groundwater beyond the capture zone are decreasing.