Pemaco Maywood

Overview

A chemical mixing facility operated on this four-acre Maywood, California property from the late 1940s until 1991. A fire destroyed the plant in 1993, and investigations confirmed hazardous chemicals in soil and groundwater. EPA added the site to the National Priorities List on January 19, 1999. The site is cleaned up through one primary operable unit, with a final cleanup plan selected in January 2005.

EPA identified 78 contaminants of concern in soil and groundwater. These include volatile organic compounds such as benzene, trichloroethene, tetrachloroethene, and vinyl chloride. Other contaminants include 1,4-dioxane, MTBE, chloroform, and several other chlorinated compounds. Metals found in soil include arsenic, cadmium, chromium, lead, manganese, and nickel. Polycyclic aromatic hydrocarbons such as benzo[a]pyrene and naphthalene were also detected in soil.

EPA's cleanup combined several methods: electrical resistive heating in highly contaminated areas, dual-phase extraction of groundwater and soil vapor, removal of soil hot spots, and placement of a soil cover with revegetation. Treated vapor meets air quality standards before release. Treated groundwater and condensate go to the L.A. County Sanitary District sewer system. Physical construction of the remedy was completed in September 2007. EPA transferred lead agency oversight to California's Department of Toxic Substances Control (DTSC) in 2018. DTSC now manages monitoring, treatment plant operation, and cleanup activities. The site achieved sitewide ready for anticipated use status in September 2019 and is now part of Maywood Riverfront Park, which opened fully in November 2018.

Human exposure is under control and groundwater migration is stabilized, per the 2020 five-year review. That review also found the groundwater extraction system needs evaluation and optimization due to ineffective performance. EPA continues to sample groundwater twice yearly and monitor whether contaminated water stays within its original area. The Fourth Five-Year Review is underway in 2025, with the report due by September 30, 2025.

Community members can read the Five-Year Review report once posted on EPA's webpage. Copies will be available at EPA's Superfund Records Center at 75 Hawthorne Street, 3rd Floor, San Francisco, CA 94105, and at the Maywood César Chavez Public Library at 4323 East Slauson Avenue, Maywood, CA 90207. For questions, contact EPA's Community Involvement Coordinator. For state-related questions, contact the California Department of Toxic Substances Control.