REMEDIATION OF MERCURY IMPACTS TO A PUBLIC WATER SUPPLY SYSTEM

A release of mercury at a municipal water well pump station building resulted in measurable concentrations of mercury in the water supply system, in the floor of the pump station building, in surrounding soil and mercury vapor in air in the building workspace. The well, one of only two water supply wells for the community, was immediately shut down. Following an initial response to the spill, an approach to remediate all media including was developed. The approach not only provided technical challenges but also required the coordination between four departments of the Massachusetts Department of Environmental Protection (MA DEP), including Water Supply, Bureau of Waste Prevention and Bureau of Waste Site Cleanup – Site Management and Emergency Response.This project was managed under the Massachusetts Contingency Plan (MCP) and under the supervision of a Massachusetts Licensed Site Professional (LSP). Activities performed include: physical recovery of spilled mercury, removal of impacted piping and equipment, decontamination of mercury-impacted surfaces in the building, basement ventilation, excavation and off-Site disposal of approximately 40 cubic yards of mercury-impacted soil, installation of three soil borings/shallow groundwater monitoring wells, and collection of air, soil, and groundwater samples for laboratory analysis. In addition, following the discovery of mercury in the water supply pipe scale, an approximate 150-foot section of pipe was removed from service. A Response Action Outcome was prepared for the site once the remediation was complete and a condition of no significant risk was shown to exist for this release.