Fort Lewis (Landfill No. 5)

Overview

Fort Lewis Landfill No. 5 covers 180 acres in Tillicum, Washington, near Tacoma. It operated from 1967 to 1990, accepting municipal and industrial waste, demolition debris, and sludge from Fort Lewis wastewater treatment. The Army listed the site on the Superfund National Priorities List (NPL) on July 22, 1987. A remedial investigation began in January 1990 to assess contamination and risks.

EPA identified 25 contaminants of concern across three media: air, groundwater, and sediment. Air contaminants include benzene, toluene, trichloroethene, and vinyl chloride, among others. Groundwater contains substances such as benzene, trichloroethene, manganese, and naphthalene. Sediment contaminants include arsenic, chrysene, and pentachlorophenol. Groundwater modeling from 1980 to 1984 found that concentrations did not exceed regulatory standards and were expected to fall over time.

Closure of the landfill began in 1987 under the Tacoma-Pierce County Health Department and the Army. The closure added a cover, a surface water management system, and a passive gas ventilation system. Once the cap was in place, groundwater contaminant levels dropped below state and federal cleanup standards. A Record of Decision issued in July 1992 selected no further action as the remedy, meaning no active cleanup was needed beyond ongoing monitoring. Construction was completed in February 1995, and EPA deleted the site from the NPL in May 1995.

Human exposure is under control. All cleanup goals for current and reasonably anticipated future land uses have been met, required land-use restrictions are in place, and the site reached Sitewide Ready for Anticipated Use status on July 20, 2010. One area of continuing attention is groundwater migration. EPA has stated there is insufficient data to confirm whether contaminated groundwater movement is fully stabilized, and monitoring continues to address that uncertainty. The Army also continues groundwater monitoring under state and local solid waste landfill requirements.

Community members with questions about the site can contact the EPA Remedial Project Manager. The Community Involvement Coordinator can also answer questions about the site.