The U.S. Environmental Protection Agency has deleted a parcel of land at the Mystery Bridge/U.S. Highway 20 Superfund site in Natrona County from its national priorities list, according to a news release Tuesday.

The action partially ended a three-decade controversy over the health and safety of the residents of the Brookhurst subdivision near the Town of Evansville.

This was one of two sites affected by the EPA's decision.

This parcel owned by Kinder Morgan, Inc., was removed from the priorities list after the completion of soil and groundwater cleanup actions, according to the news release.

The remaining area of the Mystery Bridge site is owned by Dow Chemical Company and Dowell-Schlumberger, Inc.

In 1990, the EPA added the Mystery Bridge site to the national priorities list after the discovery of extensive soil and groundwater contamination along U.S. Highway 20 east of Evansville.

Industrial operations site over many years caused wastewater, oils and solvents to seep into the ground and created two areas of soil contamination and two groundwater plumes flowing toward nearby subdivisions.

The national priorities listing came four years after Brookhurst residents complained of poor air and water quality in the area. The Wyoming Department of Environmental Quality, the Natrona County Health Department, and the EPA's Office of Drinking Water began investigating the site, according to the EPA's Record of Decision about the site.

The Centers for Disease Control's Agency for Toxic Substances and Disease Registry investigated ground water contamination, according to the record of decision. "ATSDR determined that there was an imminent and significant health threat to site residents and that if action were not taken within one year, the levels of contaminants would Increase the lifetime cancer risk for individuals drinking well water from the area."

The state provided bottled water for residents.


Remediation included installing a groundwater monitoring network, connecting residents  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.
The 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 Kinder Morgan, Inc., site.

The agency proposed the partial deletion of this parcel in June and held a 30-day public comment period. After receiving no adverse site-specific comments, the parcel was deleted from the national priorities list on Aug. 29, according to the news release.
The deletion of a site or portion of a site from the priorities list does not preclude the EPA from taking future actions at the site. It also may encourage future development, a goal of the Superfund program.

The EPA will continue to evaluate conditions and conduct five-year reviews for the Mystery Bridge site to ensure the remediation continues to protect human health and the environment. The next review report is due September 2019.
The EPA Mystery Bridge site website contains further information about the site and provides documents supporting the partial deletion.

This and 20 other deletions followed EPA Administrator Scott Pruitt’s list of sites targeted for immediate and intense attention after the Superfund Task Force Recommendations issued this summer.

For more information about the Superfund Task Force Recommendations visit its website. To search for more information about these and other sites, visit the national priorities list website.

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