The Western Pacific Railroad Co. site is a 90-acre former rail yard near Oroville, California. The facility operated from the 1880s until operations largely ceased by 1970, with the yard formally closing in 1982. Activities there included welding, painting, machining, and locomotive fueling. Waste solvents, oils, grease, and metal-laden wastewaters were discharged into an unlined surface impoundment until 1987. EPA added the site to the Superfund National Priorities List in 1990.
Contamination affected both soil and groundwater. Groundwater contained volatile organic compounds, including 1,1-DCE (1,1-dichloroethylene). Surface soil in the fueling area contained polycyclic aromatic hydrocarbons, and the former surface impoundment held heavy metals. EPA identified eight contaminants of concern in soil: arsenic, benzene, benzo[a]pyrene, chromium, copper, lead, polycyclic aromatic hydrocarbons, and toluene. Four California Water Service Company wells within three miles of the site serve roughly 10,000 customers, and a public drinking water well is located on-site just west of the fueling area.
Union Pacific Railroad, the subsequent site owner and potentially responsible party, led much of the physical cleanup work. Initial actions in the early 1990s removed soils and sludges from the surface impoundment and underground storage tanks, which were recycled into asphalt road base. A groundwater pump-and-treat system started in 1994. A second extraction well and a soil vapor extraction unit were added in 1997 to address 1,1-DCE contamination. Groundwater treatment finished in 1999 and the soil vapor system wrapped up in 2000. Contaminated soil in the fueling area was removed and replaced with clean fill in 1998. A deed restriction filed in 2001 limits future land use to industrial purposes only, and zoning prevents residential development.
EPA deleted the site from the National Priorities List in August 2001. Construction of the cleanup remedy was completed by March 1999, and the site achieved sitewide readiness for anticipated reuse in 2006. The most recent five-year review, completed September 19, 2023, confirmed that response actions protect public health and the environment in the short term. Human exposure pathways are under control, contaminated groundwater migration is stabilized, and no unacceptable discharge to surface water exists. Continued groundwater monitoring is required to maintain the remedy's protectiveness. The next five-year review is estimated between September and November 2028.
Today, part of the property includes a maintenance shop, a small classification yard, and an active rail line, while the fueling area remains inactive. Community members with questions can contact the EPA Remedial Project Manager or Community Involvement Coordinator.
