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The 446-acre Midvale Slag site is located in Midvale City and Murray City, Utah. Five lead and copper smelters operated at the site between 1871 and 1971. Smelter facilities were demolished in the 1970s. Smelting operations contaminated groundwater and soil with heavy metals. Following cleanup, operation and maintenance activities are ongoing.
What Has Been Done to Clean Up the Site?
The site is being addressed through federal, state and potentially responsible party (PRP) actions.
EPA has conducted five-year reviews at the site. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that the remedies at OU1 and OU2 are expected to be protective of human health and the environment upon completion. In the interim, exposure pathways that could result in unacceptable risk are being controlled.
What Is the Current Site Status?
The site consisted of two areas, referred to by EPA as operable units OUs. OU1 is the northern 266 acres of the site. OU2 is the remaining 180 acres to the south. The dividing boundary between OU1 and OU2 is slightly south of 7200 South, which bisects the site.
The long-term remedy for OU1, selected in 1995, included removing and replacing yard soils at Winchester Estates, a small residential development at the northern end of the site. The remedy also included groundwater monitoring and institutional controls. In 1998, EPA updated the remedy to excavate contaminated soils on one additional parcel of land. In 2006, EPA again updated the remedy to change land use restrictions to accommodate multiple land uses. The update also created an approach to riparian management and a comprehensive groundwater monitoring plan that was consistent for both OUs. Cleanup at OU1 is complete.
EPA selected the long-term remedy for OU2 in 2002. EPA divided OU2 cleanup into three parts: smelter waste and slag, groundwater and the riparian zone. Cleanup of the smelter waste and slag included regrading, installation of a vegetated soil cover and institutional controls. This work finished in 2007. A monitoring system ensures that groundwater from the site does not cause exceedances of state water quality standards in the Jordan River. The OU2 remedy also required formation of a stakeholder group to focus on a plan to restore and stabilize the banks of the Jordan River as it flows through the western portion of the site.
From 2008 through 2010, EPA implemented the Jordan River Riparian Improvement Project. Work included removal of a damaged sheet pile dam from the river that was a relic of past mining activities, installation of a new dam structure to stabilize the riverbed slope and prevent potential riverbank erosion, installation of additional stabilization measures and flow control devices, and revegetation with native and riparian wetland plants. The site achieved Superfund “construction complete” status in September 2011.
In 1990, EPA started cleanup actions to address immediate threats at the site. EPA removed chemicals found in an abandoned lab, detonated about 20 pounds of explosives and fenced the site to prevent public access. In 1996, contaminated soil was excavated from the Butterfield Lumber portion of OU2 and from the small, unmarked Pioneer Cemetery.