Modern Sanitation Landfill covers 66 acres in Lower Windsor Township, York County, Pennsylvania. It accepted municipal and non-hazardous industrial waste for decades, with open domestic dumping starting in the 1940s and reported hazardous waste disposal between 1976 and 1979. EPA added the site to the Superfund National Priorities List in June 1986 after past disposal practices contaminated soil, groundwater, and surface water with hazardous chemicals.
EPA identified 16 contaminants of concern at the site, all found in groundwater. These include volatile organic compounds such as benzene, chloroform, trichloroethene, tetrachloroethene, and vinyl chloride. Other contaminants include dichloroethane and dichloroethene compounds, 1,4-dichlorobenzene, dichloromethane, carbon tetrachloride, and polycyclic aromatic hydrocarbons.
EPA selected a cleanup plan in June 1991. The remedy covers one main operable unit focused on the landfill cap. Work included building a low-permeability cap over 62 of the 66 acres, installing groundwater extraction systems on the eastern and western perimeters, constructing a wastewater treatment facility and landfill gas extraction system, adding fencing, and setting up a monitoring network. Construction was completed in October 2000. In February 2015, EPA modified groundwater cleanup goals to align with Safe Drinking Water Act maximum contaminant levels and Pennsylvania-specific standards, and added institutional controls to restrict groundwater use and protect the cap.
The 2025 Five-Year Review confirms the remedy is currently protective of human health and the environment. The cap is functioning properly, preventing direct contact with landfill waste. Contaminated groundwater is stabilized and contained, with no unacceptable discharge to surface water. The site has achieved "Sitewide Ready for Anticipated Use" status, meaning all cleanup goals for current and reasonably anticipated future land uses have been met. The review does recommend that EPA sample groundwater for PFAS compounds, which are per- and polyfluoroalkyl substances, to determine whether any contamination is connected to the site. The site has not yet been deleted from the National Priorities List.
Community members can get involved through EPA's Superfund community involvement process. A factsheet summarizing the 2025 Five-Year Review findings is available from EPA. Questions can be directed to the EPA's Community Involvement Coordinator or Remedial Project Manager.
