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Mystery Bridge Superfund

The Mystery Bridge/U.S. Highway 20 Superfund site east of Evansville, as pictured in January. The EPA approved $1.4 million in grants to Wyoming for the cleanup of former industrial sites.

An area of contaminated groundwater beneath a housing development in Evansville has been partially removed from the Environmental Protection Agency’s National Priorities List, about 30 years after it was designated a superfund site, the agency announced Tuesday.

Seven other superfund sites from across the country were also deleted, or partially removed, from the list. EPA Administrator Scott Pruitt said in a statement Tuesday that crossing superfund sites off the list is evidence of the agency’s priorities after convening a task force to address sites last summer.

“It’s an official recognition that we’ve cleaned up the site and accomplished what we originally set out to do,” said Andrew Schmidt, remedial project manager for the Wyoming site, also called Mystery Bridge.

The Mystery Bridge super fund site overlaps with the Brookhurst subdivision, a group of homes between Highway 20 and the North Platte River, just east of Casper. Water beneath the neighborhood was contaminated by toxic substances like benzene from decades-old leaks and spills at a gas compressor plant and tetrachloroethene, a solvent used as a degreaser, from an industrial truck wash that was operated from the 1950s to the ‘80s.

The chemical compounds soaked into the soil and polluted part of the relatively shallow aquifer beneath the subdivision and moved gradually in the direction of the North Platte, Schmidt said.

The water pollution from the gas plant has been removed from the superfund list. The plume of underground toxins related to the truck wash remains on the list.

“That does not mean we are simply walking away,” Schmidt said of the deleted parcel of the Mystery Bridge site. “We are still going to go back every five years, look at it and make sure everything is okay.”

The agency is currently considering whether the second source of pollution, the truck wash, can be removed from the list as well, he said.

The EPA has been addressing the pollution at Mystery Bridge since the mid-’80s, after residents complained of poor air and water quality. State, local and federal investigation led to the discovery of contaminants and a warning that locals should not drink, wash or cook with their water due to the hazard of the chemical contamination

One resident’s water was found to have 160 parts per billion of benzene, according to Star-Tribune reporting in 1986. The EPA standard for safe benzene levels in drinking water today is 5 parts per billion.

The state originally offered bottled water to local residents. The EPA assisted in connecting the area to the city water system and improving the water treatment facilities.

The companies responsible were ordered to begin remediation at the sight in the late ‘80s, when Mystery Bridge was proposed for the National Priorities List.

Thirty years later that work is being officially concluded.

“Superfund sites are superfund for a reason,” Schmidt explained of the long cleanup process. “They are generally complex. Once contaminants get into the groundwater, it takes a while to remediate that.”

A call to the Evansville public works department was not returned by press time. A spokeswoman for the Casper-Natrona County Health Department was not up to speed on the superfund site, which has long been in the hands of the EPA.

Kinder Morgan operated the gas compression facility that led to the pollution. It is now owned by Tallgrass Energy Partners. The nearby oil field services truck wash was owned by Dow Chemical Company and Dowell-Schlumberger.

Schmidt said current water monitoring in the subdivision suggests that the aquifer is now at safe drinking water standard.

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Follow energy reporter Heather Richards on Twitter @hroxaner


Energy Reporter

Heather Richards writes about energy and the environment. A native of the Blue Ridge Mountains in Virginia, she moved to Wyoming in 2015 to cover natural resources and government in Buffalo. Heather joined the Star Tribune later that year.

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