Laserfiche WebLink
K Probable Hydrologic Consequences of Mining (2.05.6(3)(b)(iii)) <br />This section reviews the Probable Hydrologic Consequences (PHC) of mining <br />at the Sanborn Creek Mine location. The review includes the probable <br />consequences which will result from the entve Sanborn Creek Mine, including <br />the Sanborn Creek Mine and Sanborn East Tract. The Cumulative <br />Hydrologic Impact Assessment (CHIA) for the North Fork of the Gunnison <br />River contains a detailed analysis of the cumulative impacts of all currently <br />permitted mine activities within the North Fork of the Gunnison River <br />drainage basin. The CHIA document is available for review at the Division <br />office. This PHC is based upon information contained within Permit No. <br />C-81-022 (Sanborn Creek Mine) and upon the analyses contained within the <br />CHIA for the North Fork Gunnison River. The PHC separately addresses <br />potential effects on groundwater and surface water. <br />Effects on Groundwater <br />Mining at the Sanborn Creek area of the Sanborn Creek Mine will impact the <br />ground water regime within the immediate area of the proposed operation, <br />but the impact is not anticipated to cause material damage to the ground <br />water regime. <br />Though the proposed operation will mine both the B and C seams that have <br />been mined before at the old Somerset Mine, the Sanborn Creek Mine will <br />not be connected to the old workings and will be protected by a 100-foot <br />buffer. The old mine is flooded and the proposed buffer will protect the new <br />operation from possible inundation from the old workings. The 100-foot <br />buffer will be maintained by advance drilling to find the location of the old <br />workings. <br />Mine water inflow into the Sanborn Creek Mine and Sanborn East Tract is <br />estimated to be 425 gallons per minute (gpm) or less. The old Sanborn Creek <br />Mine had an inflow rate of 0.15667 gpm/acre for the 1,500 acres of <br />development in the mine that was below the level of the North Fork River. <br />Projecting this rate to the 2,600 acres of the Sanborn Mine and Sanborn East <br />Tract yields an inflow of 407 gpm. The operator has rounded this figure to <br />425 gpm in the permit document. The operator has also projected an <br />additiona1235 gpm discharge from the old Sanborn Creek Mine, which might <br />reach the North Fork via the alluvial system. This is considered to be <br />extremely unlikely; however, the projection is used i^ the CHIA to allow for <br />absolute worst-case prediction. The following are potential sources for int7ow: <br />Sanborn Creek Mine 18 Permit Revision No. 3 <br />