The Williams Pipe Line Co. Disposal Pit covers 52 acres at a petroleum terminal in Sioux Falls, South Dakota. The terminal has operated since the 1940s, handling fuel oil, diesel, gasoline, jet fuel, and liquid fertilizers. A burn pond built in 1945 collected contaminated stormwater runoff until 1987, with petroleum products periodically burned off. Those operations left groundwater contaminated with hazardous chemicals.
EPA identified two contaminants of concern in groundwater across the site: arsenic and total petroleum hydrocarbons (TPH). Both were flagged because EPA determined they posed an unacceptable risk to human health or the environment based on the amount present and potential health effects from exposure.
Cleanup moved through several phases. An initial assessment was completed in March 1985. The site was added to the National Priorities List (NPL), the federal roster of priority Superfund sites, in August 1990. A combined remedial investigation and feasibility study ran from April 1991 through September 1994, when EPA selected a remedy of no-further-action monitoring for the main operable unit. Potentially responsible parties carried out cleanup actions, and construction was completed by September 1994. EPA deleted the site from the NPL on April 2, 1999, confirming that cleanup goals had been met.
Human exposure is currently under control across the entire site, and groundwater contamination is stabilized with no unacceptable discharge to surface water. Ongoing groundwater petroleum contamination is being managed by the South Dakota Department of Environment and Natural Resources (DENR) under a regulatory exemption. EPA's response at the site is complete. The site achieved sitewide ready for anticipated reuse status in June 2006, meaning all cleanup goals for current and expected future land uses have been met and required controls are in place. The property is actively used for petroleum storage, with 42 aboveground storage tanks, a fuel loading area, garages, and an administration building.
Community members or interested parties can contact the EPA Remedial Project Manager. For state-related questions, contact the South Dakota DENR Ground Water Quality Program. Site records are available at the Siouxland Libraries Main Library in Sioux Falls, the DENR office in Pierre, and the EPA Superfund Records Center in Denver at (303) 312-7273.
