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-22- CUMULATIVE HYDROLOGIC IMPACT STUDY ~ - Rule 2.07.6(2)(c) requires the Division to make an assessment of the probable cumulative impacts of all anticipated coal mining in the general area on the hydrologic balance and to make a finding that the operations proposed in the permit application has been designed to prevent damage to the hydrologic balance outside the proposed permit area. This Cummulative Hydrologic Impact Study (CRIB) assesses the projected cumulative hydrologic impacts of all anticipated coal mining operation in the general area of the Dorchester No. 1 Mine. Anticipated mining is defined as the proposed life-of-mine areas for the existing mines and those for which complete permit applications have been submitted to the Division. The general area of the Dorchester No. 1 Mine has been considered to be the Chandler Synclinal Basin which coincides with the Canon City Coal Field. The surface water and ground water general areas for this CHIS also generally coincide. Figure 1 illustrates the locations of the mines within the general area. All of the mining operations considered in this assessment are located near the axis of the Chandler Syncline and are mining coal from the middle portion of the Cretaceous Vermejo Formation. Eleven coal seams occur in this formation and have thicknesses ranging from 1 to 16 feet It is difficult to correlate the strata between mines because each mine uses different terminology for the individual coal seams. Figure 3 gives a general correlation of the relationship of the seams being mined. Terminology used by the individual mines will be used in this discussion. These anticipated and existing operations, as described below, include: the Dorchester No. 1, the G.E.C. Strip Mine, Twin Pines # 2, and Newlin Creek Mine. The Dorchester No. 1 Mine lies on the southern terminus of the Chandler Syncline, and is currently mining the Red Arrow and the Dirty Jack O'Lantern seams of the Vermejo Formation. Both seams are stratigraphically lower than any of the other seams to be mined by the other three proposed mines. The G.E.C. surface mine will be removing five seams. The maximum depth of extraction will be 100 feet and the pit will, therefore, be above the piezometric surface. No inflows from bedrock strata to the pit have been observed by Division personnel. As stipulated in the G.E.C. permit, additional monitoring is underway to assess the baseline conditions for both surface and ground water effects for the new areas of the G.E.C. Mine. The proposed Twin Pines underground mine is on the northern side of the Canon City Coal Field and proposes to mine the Brookside coal seam. Information regarding the probable hydrologic consequences of this mine are currently being assessed by the Small Operators Assistance Program. The Newlin Creek underground mine is proposing to mine the uppermost seam, the Rex Carbon, and the second highest economic seam, the Shamrock. Both seams are shallow and the workings are currently above the piezometric surface, as is shown on Map 2.04.76 of the Newlin Creek application.