The Materials Technology Laboratory is a former U.S. Army facility in Watertown, Massachusetts. The Army ran the site from 1816 through the twentieth century, using it for small arms storage, ammunition production, materials testing, and nuclear reactor research. EPA added it to the National Priorities List in 1994 after contamination was discovered. The site has since been deleted from that list, and much of the land has been redeveloped.
Soil contamination was the main concern. Twenty-three contaminants of concern were identified across two operable units covering soil and groundwater. These include polycyclic aromatic hydrocarbons such as benzo[a]pyrene, pesticides including chlordane and DDT compounds, and polychlorinated biphenyls in the form of Aroclor 1260. Groundwater near Building 311 contains volatile organic compounds, specifically tetrachloroethylene and trichloroethylene.
The U.S. Army, as site owner and operator, led remediation. Cleanup was organized into three active operable units. Soil work ran from 1996 through 2003, and a no-action decision was made for the Charles River operable unit in 2005. A 2019 Vapor Intrusion Study found no health risks from soil vapors, but the Army still excavated about 3,200 tons of contaminated soil near Buildings 311 and 312 between 2021 and 2022 as a precaution. Foundation cracks were also sealed. EPA deleted the site from the National Priorities List in 2006, and the site achieved sitewide ready for anticipated reuse status in 2007.
Human exposure is currently under control. Institutional controls, including zoning restrictions that prohibit residential development, remain in place. The Army monitors these controls annually. EPA conducts five-year reviews to confirm that protections continue to work. The sixth five-year review was completed in March 2026. An explanation of significant differences for the soil and groundwater operable unit is expected between December 2026 and February 2027.
The site has been largely redeveloped. Harvard University purchased 30 acres in 2005, leading to Arsenal on the Charles, a mixed-use complex with apartments, retail, restaurants, and offices. The site also includes Squibnocket Park, an 11-acre public recreation area with trails and waterfront access. Community members with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager.
