20 Years of Monitoring Confirms That Institutional Controls Were an Appropriate Remedy
The site is underlain by till and fractured bedrock, which supplies water to the facility and vicinity residents. Volatile organic compound (VOC)-impacted soils in the area of the spills generates a plume which migrates in the shallow aquifer toward and discharges into an on-site pond. The facility and residential wells in the vicinity of the site were not impacted by VOCs. The RI concluded that the low hydraulic conductivity of the till, coupled with the strong upward vertical hydraulic gradients in the area of the pond, prevents impacts to the wells and off-Site properties.
A Technical Impracticability Evaluation indicated that it was impractical to restore groundwater to drinking water standards within a reasonable timeframe; therefore, attainment of drinking water standards were waived by the EPA. The 1995 Record of Decision set forth a remedy that combined institutional controls, groundwater monitoring with contingencies for further action, and five-year reviews.
Over 20 years of groundwater monitoring has validated the conceptual model that the site geology and hydrology limits the extent of the groundwater plume and confirms that institutional controls were an appropriate remedy. Although concentrations of VOCs have fluctuated and groundwater flow patterns have varied slightly due to variations in precipitation, the concentrations have stabilized or decreased and there have been no impacts to the deep aquifer/or bedrock.
The remedy resulted in a solution that is protective of human health and the environment, the removal of the site from the NPL, significant savings in remedial and monitoring costs, a low carbon footprint solution, and keeping the site in beneficial use.