Impacts on water resources have been one of the most contentious and debated issues of the Rosemont Mine proposal. But some facts are not in dispute. For example, the 3,000-foot-deep open pit, when abandoned, would begin filling with groundwater, eventually creating a circular pit lake measuring almost 1 mile across.
Because the water would be toxic, the estimated 90,000 acre/feet of water (enough water for nearly 300,000 families for a year) could never be used for recreation or human consumption. The mine would also significantly reduce surface water flows into Davidson Canyon and Cienega Creek, which are located downstream of the mine.
Pima County is extremely concerned about the impacts that reduced surface flows would have on the lush riparian and aquatic resources of the Cienega Creek Natural Preserve and the species that depend on this water. Other signi cant water concerns include impacts to wells in Sahuarita (from pumping for mine use) and in the Cienega Valley (from the pit lake), and contamination of surface and groundwater from mine processing procedures and the pit lake.