From 1961 to 1983, Union Pacific Railroad dumped wastewater treatment plant sludge into a 1-acre unlined pit in Pocatello, Idaho. Seepage from that pit, along with a nearby railroad tie treating facility, contaminated the underlying aquifers. EPA added the site to the National Priorities List in 1984 after an initial assessment in December 1979.
EPA identified 40 contaminants of concern across groundwater, soil, and sludge at the site. These include volatile organic compounds (VOCs) such as trichloroethene, tetrachloroethene, benzene, and chloroform. Heavy metals found at the site include arsenic, cadmium, chromium, beryllium, manganese, thallium, vanadium, and zinc. Polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene and chrysene were also detected. EPA determined these substances pose unacceptable risks to human health and the environment.
Under a legal agreement with EPA, Union Pacific Railroad carried out cleanup actions completed in 1994. Workers excavated and disposed of contaminated sludge and soil at a permitted landfill, removed non-aqueous phase liquid, and treated millions of gallons of contaminated groundwater before discharging it to the city's water treatment plant. The site also received fencing and institutional controls. A Record of Decision issued in September 1991, and amended in September 1994, guided the cleanup work. Physical construction was complete by September 1996.
All key performance measures now show the site is controlled. Groundwater beneath the site meets federal drinking water standards, human exposure pathways are under control, and groundwater migration is stabilized with no unacceptable discharge to surface water. EPA deleted the site from the National Priorities List in 1997. Today, Amtrak operates a train station at the site, and as of December 2024, 26 on-site businesses employed 297 people and generated an estimated $124 million in annual sales revenue.
Community members with questions about the site can contact the Remedial Project Manager. The Community Involvement Coordinator is also available to discuss concerns related to the site's remediation and cleanup activities.
