Mosley Road Sanitary Landfill covers 72 acres in Oklahoma County, Oklahoma. Between February and August 1976, the site accepted about 1.7 million gallons of liquid hazardous waste, including solvents, industrial sludge, and trichloroethene. That waste went into three unlined pits now buried under municipal solid waste. EPA added the site to the National Priorities List (NPL) in 1990. The NPL is the federal list of the most serious uncontrolled hazardous waste sites in the country.
The main contaminants found in groundwater include vinyl chloride, benzene, arsenic, and barium. Both the shallower alluvial aquifer and the deeper Garber-Wellington aquifer, a potential drinking water source for nearby cities, have been affected. Soil and sediment also contain a range of hazardous substances, including chlorinated solvents, heavy metals such as lead, cadmium, and chromium, and pesticides like DDT compounds, dieldrin, and heptachlor.
Cleanup actions have addressed contamination from multiple angles. A compacted clay landfill cap was installed in 1988. A landfill gas management system was built between August 1995 and February 1996 to control volatile organic compounds and reduce explosion hazards. The full remedial action construction was completed in September 2004. Waste Management of Oklahoma now maintains the cap, runs semi-annual groundwater monitoring in both aquifers, and conducts quarterly landfill gas monitoring. Deed restrictions prohibit new well installation and groundwater use at the site. Natural attenuation, meaning natural processes that break down or reduce contaminant levels over time, is also part of the cleanup approach.
EPA deleted the site from the NPL in 2013, confirming that cleanup goals were met. The site achieved "sitewide ready for anticipated reuse" status in 2007 and now hosts a commercial renewable energy operation where Waste Management converts landfill methane into diesel fuel and wax. Arsenic exceedances continue in some monitoring wells, though these may partly reflect naturally occurring arsenic in Oklahoma soils. Human exposure is under control, and groundwater migration is stabilized. EPA completed the most recent five-year review in September 2024 and found the site protective of human health and the environment in the short term. The review recommended adding monitoring for PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate) to the groundwater monitoring plan before the next review in August 2028.
Community members can review the 2024 Five-Year Review Report at the Ralph Ellison Library in Oklahoma City or online through EPA. Questions can be directed to EPA's Community Involvement Coordinator or Remedial Project Manager. The Oklahoma Department of Environmental Quality also maintains site records and can provide additional information.
