EFFECTS OF HOMESTAKE MINE WORKINGS ON SUBSURFACE AND SURFACE HYDROLOGY

A study has been initiated as part of the Deep Underground Science and Engineering Laboratory site Environmental Impact Statement to gain understanding of subsurface and surface hydrological effects from groundwater pumping. Groundwater elevation in the early 1900’s was closely associated with Whitewood Creek, approximately 300 feet below the current Ross and Yates headframes. After pumping water for nearly a century the mine was closed and for five years, water flowed into the mine, ultimately filling to bottom 3621 feet. Since August 2008, renewed pumping has lowered the water table to ~5300 feet. It is currently unknown how the long-term pumping, the five-year hiatus, and renewed pumping has affected the groundwater flow, cone of depression, and the surface hydrology in the vicinity of the workings. This project will include assessment of the cone of depression, potential inflow from Whitewood Creek, and environmental effects of increased flow in Whitewood Creek. Historical and new data will be used to build groundwater models showing the cone of depression. These data will be augmented using water quality data from inside the mine and Whitewood Creek. Results will be utilized in the EIS to provide recommendations on methods to ensure environmental degradation to surface water does not occur as a result of installation and operation of DUSEL.