The Montrose Chemical Corp. site is a former DDT pesticide manufacturing plant that operated in Torrance, California from 1947 to 1982. The 18-acre Superfund site was added to the National Priorities List in October 1989. It covers the former plant property, the adjacent Jones Chemicals property, and surrounding areas affected by decades of manufacturing and disposal. Cleanup is organized into seven operable units targeting different areas and contamination types. Construction is not yet complete, and the site remains on the National Priorities List.
The main contaminants are DDT and PCBs in soil, ocean sediments, and fish, along with chlorobenzene, benzene, and other volatile organic compounds in groundwater and soil. DDT levels in shallow soils under the on-site asphalt cap still exceed 10,000 parts per million in some areas. Groundwater contamination extends more than 1.3 miles from the plant. On the Palos Verdes Shelf, DDT concentrations exceed 200 parts per million near outfall pipes, covering roughly 44 square kilometers of ocean sediment. Both DDT and PCBs are classified as probable human carcinogens and can damage the immune, reproductive, nervous, and endocrine systems. Fish from the shelf, especially bottom-feeders like white croaker, carry unsafe levels of both contaminants. Human exposure is not under control, groundwater migration is not stabilized, and the site is not ready for its anticipated use.
Cleanup actions to date include an asphalt cap placed over the entire former plant property, removal of DDT-contaminated soil from nearby residential yards, and a groundwater treatment system operating since February 2019 that has removed over 65,776 pounds of contaminants. Pilot studies using electrical resistance heating have removed more than 200,000 pounds of volatile organic compounds from the dense underground chlorobenzene mass since 2020. Commercial fishing for white croaker near the Palos Verdes Shelf has been banned since 1990, and monitored natural recovery efforts show DDT levels slowly declining in sediments and fish. No contamination has been detected in drinking water supplies, and no domestic water supply wells were found in the contaminated groundwater area as of the most recent review.
EPA completed the third Five-Year Review for the groundwater and dense non-aqueous phase liquid operable units in September 2025. The review found current groundwater cleanup is short-term protective, but long-term protection requires addressing TCE and benzene plumes. The DNAPL cleanup was found to be protective. Groundwater remedial work is estimated to continue through 2028.
Community members can attend a virtual public meeting on April 21, 2026, from 6 to 7:30 p.m., where EPA project managers will discuss cleanup updates for both the Montrose and Del Amo sites. Spanish interpretation will be available. Residents can register for the Zoom link and submit questions directly to EPA staff. EPA also recommends consulting fish consumption guidelines for the Palos Verdes Shelf area to reduce exposure to DDT and PCBs from locally caught fish.
