The Olin Chemical site covers 53 acres in Wilmington, Massachusetts, where a specialty chemicals plant operated from 1953 to 1986. Waste disposal in unlined lagoons, spills, and other releases spread contamination across the property and into surrounding areas. EPA added the site to the National Priorities List in April 2006. The site is organized into three operable units covering the Olin property, off-property surface water and sediments, and groundwater.
Contaminants detected at the site include N-nitrosodimethylamine (NDMA), a probable human carcinogen, along with ammonia, chromium, benzo[a]pyrene, bis(2-ethylhexyl)phthalate, and trimethylpentene compounds. These substances appear in groundwater, soil, sediment, and surface water. NDMA contamination prompted the town to shut down five public water supply wells that served more than 7,000 people. EPA has determined that human exposure across the site is currently under control, but contaminated groundwater migration is not yet stabilized.
Four companies, American Biltrite Inc., NOR-AM Agro LLC, Olin Corporation, and Stepan Company, agreed in a September 2023 federal court settlement to carry out or fund the cleanup at an estimated cost of about $48 million, plus $400,000 for EPA oversight. The approved remedy includes groundwater extraction and treatment systems, excavation of contaminated wetland soil and sediment, caps and cover systems over remaining soil contamination, and institutional controls restricting land and groundwater use. Extraction well drilling and installation for targeting dense contamination was completed in December 2025. Soil sampling ran from March through December 2025, and a preliminary remedial design plan for upland soils is expected in summer 2026. A Record of Decision for long-term groundwater remediation is estimated for 2028. A real estate developer, Wilmington Woburn Industrial LLC, has entered a Prospective Purchaser Agreement with EPA and plans to build a warehouse facility at the main property entrance, coordinating construction with cleanup requirements.
Residents can stay involved through EPA newsletters and informational open houses. A Community Involvement Plan was finalized in November 2023. Community records are available at the Wilmington Memorial Library at 175 Middlesex Avenue and at the EPA Region 1 Records Center in Boston. Residents with questions can contact the EPA's Community Involvement Coordinator or Remedial Project Manager.
(NOTE: This summary was created based on all information available on the EPA's official site profile page as of May 29, 2026. To see the most up-to-date information provided by the EPA, visit the EPA's official profile page for this site. For questions, or to politely request the EPA keep their profile page current, contact the EPA Community Involvement Coordinator or Remedial Project Manager assigned to this site.)
