Significant groundwater contamination exists in the aquifer downgradient of the Bingham Canyon mining operations. Starting in the late 1980s, the State of Utah Natural Resource Damage Trustee has overseen the investigation of mining-influenced groundwater and the implementation of cleanup actions performed by Kennecott and the Jordan Valley Water Conservancy District to address two groundwater plumes located in southwest Salt Lake County. The plumes were caused by historical mining practices in the Kennecott South Zone. Approximately are impacted in the southwest portion of Salt Lake County. Because of the remediation efforts, which include more than a $100 million investment in a reverse osmosis facility, Kennecott's South End, (location of the contaminated aquifer) was removed from the United States Environmental Protection Agency (EPA) National Priorities List (NPL). This investment represents one of many remediation projects along the Oquirrh Mountains to clean up historic mining sites. To date, Kennecott Utah Copper has remediated more than of the total impacted by mining at a cost of more than $450 million. KUC has spent more than $350 million on the cleanup of historic mining waste and $100 million on groundwater cleanup.