PERMFILE101111 - Laserfiche WebLink

Home Browse Search

However, further analysis using hydrogeologic evaluation and geologic cross-sections indicates that the • Rollins Sandstone is not a significant aquifer in the Jumbo Mountain area due to it low permeability, poor water quality, limited recharge (< 0.5 in/yrl and its hydraulic separation from the Rollins Sandstone on the north side of North Fork in the Jumbo Mountain area. In addition, in the Jumbo Mountain area, the strata finterburden) between the 8-Seam and the Rollins Sandstone thickens considerably wish an average thickness of about 150 feet. Because of these factors, it is highly unlikely that mining activities in the Jumbo Mountain area will affect the hydrogeologic character of the Rollins Sandstone. Therefore, no additional monitoring wells in the Rollins Sandstone and as stated in 2.04.7 111 Hydrology Description in the Colorado Regulations, are necessary. 4. Concern: 'MCC should install a B seam well down-dip from JMB-12 and active mining in Jumbo Mountain. Rule 2.05.613) states that the quality and quantity of surface and groundwater should be protected. An up-dip and down-dip well will provide data to assess whether any impact is occurring. The additional well should be located where it will not be destroyed by mining activities.' (April 15, 1994) Response: As stated in the MCC response dated May 23, 1994, down-dip from the mining operation the minable portion of the B-seam has been removed by an ancient landslide on the north side of the Jumbo • Mountain and the placement of such a monitoring well that would accurately monitor the impact of mining is not possible. I[ is recognized that mining of the B-Seam will affect groundwater within this unit. The coal seam will be drained and water levels will drop. Because groundwater slow is topographically controlled rather than structurally controlled, the placement of a monitoring well down-dip, should i[ be possible, would do little to monitor the overall hydrological impact to the B-Seam. Finally, based on the above calculations, the B-Seam is insignificant in terms oT the overall regional and local hydrologic balance and no additional well should be required. However, MCC is willing to work with the Division to design a satisfactory monitoring program. 6. Concern: 'From extensive review of PR-05 and the currently approved permit, it is apparent that groundwater in the Jumbo Mountain Tract is generally perched in the strata above the B-Seam and usually present invariable quantities in the B-seam and the Rollins Sandstone. The operator should develop and submit maps indicating the piezometric surface of the B-seam and Rollins Sandstone in the Jumbo Mountain Tract (Rule 2.04.7(41(c1. In addition, reference this information and expand discussion of the potential for Rollins water to move into the mine workings, specifically along faults.' (April 15, 1994) Response: Currently, there is insufficient data to develop a potentiometric map for the Rollins Sandstone. • 6