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J. Stream Buffer Zones <br />The Division does not propose to approve surface or underground mining <br />activities within 100 feet or through a perennial stream or stream with a <br />biological community (4.05.18(1)). <br />K. Probable Hydrologic Consequences <br />BRL provided an analysis of the Probable Hydrologic Consequences to be expected as a <br />result of mining and reclamation operations at the Bowie No. 2 Mine. The analysis is <br />presented in Section 2.05.6(3)(b)(iii) of the permit application document. Possible <br />hydrologic impacts to the local surface and ground water systems are summarized below. <br />Surface water systems directly above the mine working, and within the permit area, could <br />be minimally impacted due to mine subsidence. Surface cracking resulting from <br />subsidence could occur within the ephemeral and intermittent stream channels which <br />overlie the mine; however, such impacts should be minimal and surface cracks should fill <br />with sediment relatively quickly. Actual interruption of surface flows should not be <br />significant. <br />Stock ponds located above the mine, and within the permit area, could also be impacted <br />by subsidence; however, significant impacts are unlikely, due to the approved subsidence <br />protection plan for the Bowie No. 2 Mine which should minimize subsidence beneath any <br />of the stock ponds. These stock ponds are owned by BRL. <br />The required sediment and drainage control plan for the Bowie No. 2 Mine must be <br />constructed and maintained as permitted. This system will protect all offsite areas from <br />any detrimental impacts from sediment or surface runoff originating on the mine site. <br />It is possible that offsite areas might receive discharge from such sources as underground <br />mine water, refuse pile leachate, or other mine-related activities. Such parameters as iron <br />and oil and grease are strictly regulated by point source discharge permit standards <br />(issued by the Colorado Department of Public Health and Environment) limitations. <br />However, mine-related discharge may exhibit increased levels of total dissolved solids. <br />The Bowie No. 2 Mine permit document provides reasonable predictions of mine-related <br />discharge quantity and quality, specifically emphasizing possible increases in total <br />dissolved solids to the hydrologic system. The predictions indicate that any such <br />increases should not be significant, and downstream uses should not be impacted. <br />Perched groundwater, located above the mine workings and within the permit boundary, <br />could be impacted by subsidence. Specifically, subsidence could temporarily de-water <br />these zones; however, these water sources are not used, and recharge should occur over <br />time. It is also possible that the local bedrock groundwater quality could be impacted by <br />elevated total dissolved solids concentrations, as the mine fills with water following <br />mining, and as the water infiltrates to surrounding groundwater. Impacts within the <br />permit area should be minimal, due to the relative lack of useable groundwater, and due <br />to the vertical separation which exists between the D-2 coal seam, the B-2 coal seam and <br />the Rollins Sandstone located considerably below the mining elevation. Local alluvial <br />systems downgradient from the mine should not receive sufficient mine water drainage to <br />create any impacts. <br />29