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• General Hydrology <br />Groundwater Systems. <br />The general geology in the vicinity of the proposed mine has <br />been described above, In brief summary, the basic stratigraphy <br />within the lower portions of the Coalmont Formation consists of <br />interbedded sandstones and siltstones, with the section immediately <br />overlying the Sudduth Coal made up of primarily sandstone. About <br />100 feet or so above the Sudduth Coal the section seems to be <br />predominately siltstone. These basic stratigraphic relationships <br />are illustrated on the cross sections (Exhibit C-3 and C-4). The <br />stratigraphy shown on these sections has been somewhat idealized <br />for the sake of simplicity and depicts a somewhat higher lateral <br />continuity than is actually found. Past and present experience in <br />observation of lithologies in the mined areas concludes that the <br />Coalmont Formation is generally highly interbedded and individual <br />• strata very lenticular in nature. Hence, such a media is naturally <br />restrictive to groundwater migration. <br />Immediately underlying the Sudduth Coal is the Upper Sandy <br />Member of the Pierre Shale which is of Late Cretaceous Aqe. <br />Exploration in the vicinity has indicated that this formation is <br />predominately an interbedded sandstone, siltstone and shale <br />sequence with the sand fraction being the greatest percentage. <br />This sandy zone is almost always separated from the coal by up to <br />as much as 30 feet of rather impervious siltstone. <br />Capping the upland divide areas in the vicinity of the proposed <br />mine are remnant terrace gravel deposits which were laid down by <br />the Canadian and Michigan River systems when they were at that <br />level. These gravel caps are sufficiently permeable to collect <br />water which infiltrates the surface as rain and snow melt. These <br />• <br />-5- <br />