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Sanborn Creek Project Page 18 August 21, 1992 • There are no known permeable fault zones connecting the planned ^C" and ^B" Seam workings in the Sanborn Creek Mine with either the "E" Seam workings, Hawk's Nest Mines, or the "D" Seam workings, Oliver No. 1 Mine. However, the Oliver No. 2 Mine on the opposite, south, side of the North Fork of the Gunnison River was abandoned in 1953 after an inrush of water and gas (Dunrud, 1976). This inrush intercepted, and continues to intercept, a perennial stream lying approximately 300 feet overhead. A high permeability natural flow path, such as a fractured fault zone, must have been present to produce such an inrush. Subsidence could not account for this inrush since the Oliver No. 2 Mine did not practice retreat mining, and the inrush occurred within a set of advancing sub-mains. A zone of fractured, but not water bearing, rock was intersected at the bottom of the slope, near the portal, of the Hawk's Nest East Portal Mine. Zf such a fractured rock zone were intersected during planned aininq at the Sanborn Creek Mine and it connected to water impounded in either of the overlying mines an inrush could result. This unlikely, but potential, hazard further supports the recommended pre-drainage of the overlying Oliver No. 1 Mine and, if water is present, the Hawk's Nest East Portal and West Portal Mines. • It is probable that mining of the "C" and "B" Seams in the Sanborn Creek Mine can be successfully completed as planned without adverse water impoundment problems developing. Development of mains, sub-mains and panel rooms can proceed without pre-draining water from any of the overlying mines. However, it is recommended that the water probably impounded in the overlying Oliver No. 1 Mine be pre-drained prior to robbing underlying pillars. If water is found to be impounded in the Hawk's Nest East and(or) West Portal Mines it should also be pre-drained. Chimney subsidence is unlikely to produce a connection between the Sanborn Creek Mine and workings in the overlying abandoned mines, the Oliver No. 1 Mines in the "D" Seam or the Hawk's Nest East or West Portal Mines in the "E" Seam. Such a chimney subsidence connection would be necessary for a mining related inrush of water into the Sanborn Creek Mine. Trough subsidence induced tensile strains accompanying crushing out of robbed panel pillars will probably slowly and progressively drain any water in the overlying abandoned mine workings. USBM guidelines (Babcock & Hooker, 1977) recommend drainage of all possible impounded water in the overlying Oliver No. 1 Mine and in the overlying Hawk's Nest East and west Portal Mines prior to robbing pillars during retreat mining of underlying panels in • the Sanborn Creek Mine.