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Mystery Bridge Rd./U.S. Highway 20 Superfund site near Evansville partially deleted from Superfund list

EPA making strides in cleaning up the Nation’s most contaminated sites

Contact Information: 
Cynthia Peterson (

DENVER (January 2, 2018) – As a result of staff working hard to implement Administrator Scott Pruitt’s initiatives to make strides in cleaning up the nation’s most contaminated toxic land sites, the U.S. Environmental Protection Agency (EPA) is announcing significant improvement in 2017 – through the deletion of all or parts of seven Superfund sites from the National Priorities List (NPL). This is more than triple the number of sites removed from the list in 2016.

“We have made it a priority to get these sites cleaned up faster and in the right way,” said EPA Administrator Scott Pruitt.  “By creating a streamlined task force and making major remedy decisions that hold potentially responsible parties accountable for cleanup, the Superfund program is carrying out the Agency’s mission of protecting human health and the environment more every day.”

In 2016, EPA had deletion activities at two NPL sites, one full site and portions of another. But in 2017, under the leadership of Administrator Pruitt, EPA has deleted three entire sites and portions of four others.  This increase in deletions reflects Administrator Pruitt’s commitment to accelerating progress, reducing risks at Superfund sites and returning sites to productive use.

These deletions come on the heels of Administrator Pruitt’s list of 21 sites that have been targeted for immediate and intense attention – a direct response to the Superfund Task Force Recommendations issued this summer.

The Mystery Bridge/U.S. Highway 20 Superfund site (Mystery Bridge site) in Natrona County, Wyoming, is one of the Superfund sites that included a partial deletion. The deletion of the Kinder Morgan, Inc. (KMI) parcel from the NPL is based on the completion of soil and groundwater cleanup actions for the parcel.  The remaining area of the Mystery Bridge site, the Dow Chemical Company and Dowell-Schlumberger, Inc. (DOW/DSI) parcel, remains on the NPL.

EPA added the Mystery Bridge site to the NPL in 1990 following the discovery of extensive soil and groundwater contamination at properties along Highway 20 east of Evansville, Wyoming. Because of industrial operations on the KMI and DOW/DSI parcels 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 nearby subdivisions. Response activities at the site included: the installation of a groundwater monitoring network; connecting residents in the nearby subdivision to the municipal water system; upgrading a nearby water treatment plant; and controlling the sources of contamination to inhibit further migration of the groundwater plumes into the subdivision.

EPA and the State of Wyoming have concluded that all appropriate responses under the Comprehensive Environmental Response, Compensation and Liability Act have been implemented and that no further cleanup is required for the KMI parcel of the site. EPA proposed the partial deletion of the KMI parcel in June 2017 and held a 30-day public comment period. After receiving no adverse site-specific comments, the parcel was deleted from the NPL on August 29, 2017.

The deletion of a site or portion of a site from the NPL does not preclude the EPA from taking future response actions at the site or portion of the site, if necessary. The EPA will continue to evaluate conditions and conduct Five-Year Reviews for the Mystery Bridge site, to ensure that the remedy remains protective of human health and the environment. The next Five-Year Review report is due September 2019.

The EPA Mystery Bridge site webpage contains further information about the site and provides documents supporting the partial deletion.

NPL deletion occurs when all the remedies are successfully implemented and no further cleanup is required to protect human health or the environment.  The Agency deletes portions of NPL sites when work at those portions is complete and other parts of the site still have ongoing actions.

The three completely deleted sites are:

  • Nutting Truck & Caster Co. in Minnesota, originally contaminated with trichloroethylene (TCE) in groundwater;

  • Shpack Landfill in Massachusetts, which had contaminated soil, sediment and groundwater; and,

  • Perdido Ground Water Contamination in Alabama, which was originally contaminated with benzene.

In addition to the partial deletion at the Mystery Bridge Rd/U.S. Highway 20 in Wyoming, EPA completed partial deletions for:

  • Ellisville Site in Missouri, which contained drums full of hazardous materials;

  • Omaha Lead in Nebraska, where surface soil was contaminated by deposition of air emissions from historic lead smelting and refining operations; and,

  • North Penn - Area 6 in Pennsylvania, where soils and groundwater were contaminated with volatile organic compounds.

Deleting a site or portions of a site from the NPL may facilitate future redevelopment, one of EPA’s goals for the Superfund program. 

The NPL is one focus area of the Superfund Task Force Recommendations to improve and revitalize the Superfund program. Work to prioritize and reinvigorate the Superfund program is underway and will continue into 2018.

The Superfund Task Force Recommendations can be viewed at

To search for more information about these sites, and other sites deleted from the NPL, please visit: