Superfund Site Profile

EPA is proposing to delete the property currently owned by Tallgrass Energy Partners, LP within the Mystery Bridge Superfund site from the National Priorities List. The public is invited to comment on the proposal during a comment period beginning on June 30, 2017 and ending July 31, 2017. For more information, view the public notice.


The Mystery Bridge Road/U.S. Highway 20 Superfund site is located in Natrona County, just east of Casper, Wyoming. The site includes two industrial properties and a residential area downgradient of the source areas that was impacted by releases of contaminants. The two industrial properties include a facility formerly owned by Kinder Morgan Energy Partners, L.P. (KMI) and facility owned by Dow Chemical Company/Dowell Schlumberger, Inc. (Dow/DSI). The downgradient residential area is called the Brookhurst residential subdivision, and consists of 125 lots ranging from 2 to 5 acres in size. Beginning in 1963, KMI owned and operated a gas compression and transmission plant at the site. The facility is still in operation, however, ownership has been transferred to Tallgrass Energy Partners, LP. Dow/DSI operated an oil production service facility and a truck wash at the site from the 1950s until the 1980s. As a result of industrial operations on the KMI and DOW/DSI properties over many years, a mixture of wastewater, oils and solvents seeped into the ground and created two areas of soil contamination and two groundwater plumes flowing toward the residential subdivisions on site. The site is also adjacent to the Sinclair Refinery (formerly Little America Refining Company). Potential releases at the Sinclair Refinery are currently being addressed under a Resource Conservation and Recovery Act 3008(h) order.

The potentially responsible parties (PRPs), KMI and Dow/DSI, worked with EPA to clean up the site’s two operable units (OUs) through a series of removal and remedial actions focusing on groundwater (OU1) and source contamination (OU2).