Delineation of Abandonment Procedures for the Bunker Hill and Crescent Mines, Shoshone County, Idaho.
The Bunker Hill and Crescent Mines are located in similar physical, geohydrologic, and geographic settings. The mines are only 3 miles apart and are connected physically by a crosscut drift. Flooding of the lower levels of both mines is expected to significantly reduce acid water production in those areas of the mines, although the mines are expected to fill with acid water because of the dissolution of oxidation products during the filling process. At least one mine pool volume of water is expected to require treatment after flooding. The levels of the Crescent Mine that are above the elevation of flooding are not expected to require the application of any special abandonment techniques upon mine closure because the drainage from the upper mine workings is good quality water. The presence of acid water in the upper workings of the Bunker Hill Mine does require the use of abandonment techniques to reduce water treatment costs after mine closure. Infiltration control, water diversion procedures, and partial flooding of the upper mine workings may be used to reduce acid water production in the upper mine levels.