On March 11, 2010, the Massachusetts Department of Environmental Protection (MassDEP) requested assistance from the EPA Region 1 Removal Program with the Capen Street Site In Milton, MA . An investigation conducted by the MassDEP and their state contractor in November 2009, documented elevated levels of arsenic (As) and lead (Pb) in surface soils on property owned by the Massachusetts Department of Conservation and Recreation (MA DCR) on land close to the Neponset River in Milton, MA. This property was immediately adjacent to the site where spoils from the Neponset River were placed during a dredging operation in the 1960’s and when the sampling was originally conducted, it was believed that the spoils were the source of the contamination. As there is a residential neighborhood adjacent to this DCR property (centered around Capen Street), the MassDEP utilized their contractor to collect soil samples on private properties throughout the neighborhood during the summer of 2010 to determine if arsenic and lead were present in surface soils at concentrations of concern. Lead and/or arsenic were detected in surface soils on a number of properties above potential imminent hazard levels (As: 40mg/kg, Pb: 1000 mg/kg established by the Massachusetts Contingency Plan (MCP)). Since other contaminants such as PCBs which were known to exist in the river spoils but were not detected in the DCR or residential properties, the source of the contamination is now believed to be from the historic spraying of a lead and arsenic based pesticide for gypsy moth caterpillar control.
The MA DCR mobilized to Milton with their contractor in late May, 2011 to begin excavating impacted soil from their property. EPA mobilized on June 27, 2011 to begin addressing the residential properties.
On June 29, 2011, excavation began on the first of ten properties previously identified. Since the walls and floor of each excavation were tested prior to backfilling, the excavations were, in many cases, expanded until the testing indicated that the levels of the contaminants of concern were below the imminent hazard levels. One of the excavations led to the removal of soil from two neighboring yards and a second excavation expanded onto one immediate neighbor’s property. In addition, the owner of one of the residential properties which had never granted access to the MassDEP, acquiesced and granted access to EPA and their contractor(s). This yard did contain arsenic and lead at levels of concern, so this raised the total number of properties to fourteen.
On August 30, 2011, excavation was completed on the final residential property. Restoration of these properties including backfilling, grading, re-vegetation, and fence reconstruction continued until site demobilization in mid-September.
