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<br />2.04 Application for Permit for Underground Mining Activities <br />Dorchester No. 1 Mine, Fremont County, Colorado. <br />2.04.7 Hydrology Description <br />Attachment III contains the primary statement regarding Hydrology <br />In the Permit and general areas. The Informiation which follows is <br />supplemental to data presented In Attachment III and is offered In <br />direct response to Items listed In the Adequacy Review dated April 20, <br />1981. <br />2.04.7(1) Grand Water Information <br />Hvdrogeologic Frart~ework <br />• The Dorchester No. 1 Mine Permit Area lies on the northeastern <br />flank of the Wet Mountains near the upper end of a closed eliptical <br />synclinal basin (see Figure 2.O4.7(la)). The basin was formed by <br />folding associated with the Wet Mountain Thrust Fault, which forms Its <br />south and west boundaries. Parallel to the fault trace Is the axis of <br />Che Chandler Syncline, an asymnetrlcal feature with a steeply inclined <br />(nearly vertical) western limb and a rtuch more gradual dip (5°WNW In the <br />Permit Area) on the eastern lirtb. Figure 2.04.7 (lb) shows the <br />generalized orlentatlon of sedimentary strata within the basin. Units <br />of Importance in describing the hydrogeology of the Pennlr Area are the <br />Raton and VenneJo Formations, Trinidad Sandstone, and Pierre Shale. <br />Outcrops or subcrops of all units mentioned above actor around. the <br />entire rim of the basin (Figure 2.04.7 (la)). The topographic lav point <br />in the rim Is to the north, where (t is cut by the Arkansas River. The <br />topographic high point is Just south of the Permit Area along the Net <br />Mountain} Fault. <br />• The granitic Wet Mountains south and west of the .Permit Area <br />receive more precipltatlon than Lhe synclinal basin, and larger streams <br />originating in Lhe mountains and flawing northeast (Newlin and Oak <br />Creeks are exanples) are typically perennial until crossing the Wet <br />4 <br />