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Twentymile Coal, LLC (TC) <br />Narrative <br />Lease by Modification Application Wolf Creek Reserve — April 2014 <br />mining on water quality can be measured by analyzing monitoring data for indicator <br />parameters such as electrical conductivity (EC), total dissolved solids (TDS), total suspended <br />solids (TSS), sodium adsorption ratio (SAR), pH, and metals. <br />Mining activities in the Permit Area may result in changes in surface water quality. Mining <br />practices such as removing and stockpiling topsoil, clearing vegetation, road construction, <br />and vehicular travel in disturbed areas have the potential to increase erosion and sediment <br />loss in disturbance. TSS concentrations in receiving streams should not increase due to <br />mining activities because flows from disturbed and reclaimed areas are intercepted and <br />treated in sedimentation ponds prior to discharge to meet National Pollutant Discharge <br />Elimination System (NPDES) effluent limits. The effects of leaching on exposed spoil and <br />waste rock piles, detention of water in sedimentation ponds, and pumping water out of pits <br />and underground mine workings, have the potential to increase TDS concentrations and alter <br />the ionic composition of surface waters, however, given the limited surface disturbance and <br />that mine water discharge is unlikely, potential surface water quality impacts should be <br />minimal. <br />In summary, planned underground mining activities have the potential to affect surface water <br />quantity in terms of runoff flows and flow rates including changes in peak flows and low <br />flow conditions. Similarly, the planned underground mining activities have the potential to <br />affect existing surface water quality in terms of conductivity, TDS, TSS, ionic composition, <br />SAR, pH, and trace metals, with iron and manganese, the primary indicators. <br />The underground mining activities that have the potential of impacting surface water flows <br />and water quality are described in detail in TC's Mining and Reclamation Permit (CDRMS <br />Permit No. C-82-056). This discussion includes an assessment of the nature and magnitude <br />of potential impacts. The primary potential surface water impact would result from the <br />discharge to Fish Creek of mine inflows, which under present and anticipated mining <br />conditions is unlikely. If discharge were to occur, it would be controlled and monitored <br />under applicable provisions of TC's Colorado Discharge Permit System (CDPS) Permit. <br />Ground Water <br />Within the TC Permit Area (includes the Wolf Creek Reserve and proposed lease modification <br />area) ground water exists in the structural Twentymile Park ground water basin under water - <br />table conditions. Ground water occurrence, storage, and movement are associated with and <br />controlled by the porosity and continuity of water -bearing units, as well as structural features <br />within the basin, including structural gradients and faults. Known water -bearing units include <br />(in ascending sequence) the Trout Creek Sandstone, Wadge Coal Seam overburden, <br />Twentymile Sandstone, and surface alluvial/colluvial deposits. <br />Ground water resource information for the Twentymile Park ground water basin can be found in <br />TC's Mining and Reclamation Permit (Permit No. C-82-056). In addition, the ground water <br />information contained in CYCC's permits C-81-071 and C-84-062 provide information on the <br />WCR BLM Lease App Narrative 0414.docx Page 14 <br />