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Cleaning up a massive groundwater plume contaminated with a suspected cancer-causing agent on Salt Lake City's east side is entering a new phase with an agreement signed by the Veterans Administration hospital, the state and the federal government.

SALT LAKE CITY — The state of Utah, the U.S. Environmental Protection Agency and the Veterans Administration hospital in Salt Lake City are formalizing an extensive agreement to handle the long-term testing and remediation of a contaminated groundwater plume.

The agreement, out for public comment through the end of this year, represents the next step in an extensive undertaking to tackle contamination posed by a suspected cancer-causing agent, tetrachloroethylene, or PCE.

Suspected to be about 200 acres big, the 700 South/1600 East plume was declared a Superfund site by the EPA in 2013, laying the foundation to accelerate removal of the hazard.

Federal officials believe the PCE entered the aquifer as the result of a dry cleaning operation at the George E. Wahlen Department of Veterans Affairs Medical Center from 1976 to 1984.

Routine sampling of the Mount Olivet Irrigation Well in 1990 found evidence of PCE about 2,200 feet down gradient of the 72-acre medical campus, and by 2004, a Salt Lake City municipal drinking water well was shut down as a precaution.

The EPA, the Utah Department of Environmental Quality and the hospital has hosted a variety of community meetings in which homeowners in the area were asked to voluntarily have indoor air sampled for potential vapor intrusion.

An extensive round of testing and sampling of indoor air and soil gas was carried out in the fall of 2014 and early winter of 2015.

The EPA reports that the results of that survey — in which 21 locations had detectable levels of PCE — merits additional investigation. While the levels of PCE exceeded standards set in three of the samples, the contamination did not rise to an "action" level or include other potential contaminants of concern, according to the document.

An additional nine homes and East High School were sampled in 2016 for vapor intrusion, with one home that showed results above screening standards set by the EPA. Another home showed results that required the installation of a system to remove the PCE, according to officials.

More monitoring and sampling will be carried out in 2017 to more accurately characterize the plume.

Shaun McGrath, the EPA's regional administrator, said the federal agreement launches the next phase of sampling and study and more opportunity for public involvement.

The hospital has also compiled an informational page about the plume.

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