The Pester Refinery Co. site is a former petroleum refinery in El Dorado, Kansas. It has been on the EPA's National Priorities List (NPL) since March 1989. The site is organized into two operable units (OUs): one covering soil, sludge, and related remediation work, and one focused on groundwater. Cleanup construction finished in 1999, and the site reached "sitewide ready for anticipated reuse" status in May 2016. However, the site has not been deleted from the NPL.
Contamination affects groundwater, soil, sludge, and surface water. Groundwater holds volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylene, along with metals including arsenic, chromium, lead, and barium. Soil and sludge contain metals and polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene and naphthalene. EPA has identified 47 contaminants of concern in total. Health risks come mainly from people ingesting or contacting contaminated soil and groundwater.
Workers addressed contamination through bioremediation of hydrocarbon-laden soils, consolidation and solidification of pond soils under a containment cover, and an interceptor trench system to stop contaminated groundwater from reaching the nearby Walnut River. These actions ran from 1994 through 2006. Responsible parties, including Pester Refining Company and Total (under a Long-Term Care Agreement with the Kansas Department of Health and Environment, or KDHE), continue to operate and maintain the site. Institutional controls recorded with Butler County prevent incompatible land uses such as residential development, and KDHE conducts annual inspections to verify compliance.
The soil and sludge remedy is fully protective of human health and the environment. The groundwater remedy is protective only in the short term. The May 2024 Five-Year Review found hydrocarbon sheen at certain locations and rising benzene concentrations at some monitoring wells. In response, EPA recommended more frequent monitoring and installation of additional wells to track contamination in deeper aquifer layers and downstream areas. Ongoing work includes annual groundwater monitoring, quarterly petroleum sheen monitoring, annual inspections of soil covers and the trench system, and regular site maintenance. EPA will also conduct surface water and sediment sampling to confirm long-term protection. A remedial optimization plan was finalized in April 2022, and the next five-year review is scheduled for May 2029.
Community members can contact the EPA Community Involvement Coordinator or the Remedial Project Manager. Additional specialists covering hydrology, human health risk, ecological risk, and legal questions are also available through the EPA regional office.
