Protecting A Drinking Water Aquifer and an Estuary System A Massachusetts Contingency Plan Success Story

Presented on the 20th anniversary of the 1993 Massachusetts Contingency Plan, this case study demonstrates the effectiveness of the semi-privatized program. As part of a real estate assessment, contamination was identified at a facility on Cape Cod. The incident was reported to MassDEP on January 20, 1996, as a 72-hour reporting condition due to potential impacts to nearby private water supply wells. The contamination was the result of inadvertent releases of solvents including trichloroethene and tetrachloroethene. The facility was upgradient of Zone II of a municipal supply well, a number of residential water supply wells, an irrigation pond, a brook, cranberry bogs, and an estuary.  

While MassDEP focused its efforts on ensuring that the private wells were not impacted, the facility and its licensed site professional were also able to conduct additional assessment without MassDEP approval. Within one year of notification, more than 100 monitoring wells were installed and the extent of the 7000- by 1000-foot-wide plume was defined. The highest concentrations of tetrachloroethene and trichloroethene were 940 and 1100 micrograms per liter (μg/L), respectively. 

Source area sparging and soil vapor extraction reduced the concentration of solvents to background. A permanent solution for the facility property was filed with MassDEP on February 16, 2000. Groundwater treatment systems were installed 1500 feet and 3500 feet downgradient of the facility. The first operated for four years, the second for nine years. Both systems shut down when influent concentrations dropped below the cleanup standard of 5 μg/L. In 2012-2013 the concentration of solvents throughout the plume dropped below the cleanup standards. 

The flexible semi-privatized program, with its defined cleanup standards, allowed MassDEP to focus on risk reduction efforts and gave the licensed site professional  the ability to conduct expedited assessment/remedial measures and ultimately achieve cleanup.