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cliff - forming sandstone. However, like the similar sandstone at the top of the Lower Coal member, this <br />sandstone is not a single persistent bed. <br />Three coal horizons have been identified in the Upper Coal member - the D (Oliver) horizon, the E <br />(Hawk's Nest) horizon, and the F horizon. The D horizon occurs directly above the "massive" sandstone <br />of the Lower Coal Bearing member and contains three seams. This horizon was mined in the Bowie No. <br />1 Mine. The E horizon occurs about 130 feet above the D horizon and contains two coal seams. The F <br />horizon contains two coal seams. Coal seams of the F horizon do not exist to the north of the North <br />Fork of the Gunnison River in thicknesses sufficient for mining. <br />The Barren (Undifferentiated) member of the Mesaverde Formation consists of up to 1,500 feet of <br />terrestrial sedimentary rocks. This unit consists of fine- grained, buff - colored, lenticular sandstones, gray <br />shales and thin, lenticular coal beds. The sandstones predominate and are highly lenticular, <br />discontinuous and of limited lateral extent in outcrop. <br />The Mesaverde Formation is unconformably overlain by the Tertiary Age Rudy or Wasatch Formation. <br />This formation consists of red to buff - colored shales, red sandstones, and red to gray conglomerates. <br />The sediments of this formation are weathered volcanic rocks. The Ohio Creek conglomerate is the <br />basal unit within the formation and is 100 to 200 feet thick. <br />Tertiary igneous intrusive rocks exist within the North Fork drainage basin. A diorite plug about 1,000 <br />feet in diameter outcrops along Hubbard Creek in the SE 1/4 of Section 7, Township 13 South, Range 91 <br />West of the 6th P.M. This may represent the erosional remnants of a volcanic flow feeder. Sills have <br />injected the Lower Coal Bearing member, particularly the B and C seams. These sills consist of diorite <br />and appear to have their source to the northwest of Terror Creek. <br />Hydrologic Balance - Rules 2.04.5, 2.04.7, 2.05.3, 2.05.6(31, 4.05 <br />Ground Water <br />Ground water information can be found Sections 2.04 and 2.05.6 of Volume 1. Water quality <br />documentation may be found in Volume 4 and is supplemented by annual hydrologic reports prepared <br />since 1982. For a description of the ground water hydrology of the mine area and permit revision area <br />and a discussion of the impacts of mining on ground water, please refer to the Hydrologic Balance <br />portion and the Probable Hydrologic Consequences portion of Section B of this Document. <br />Three categories of potential aquifers occur in the general area. These are alluvial and terrace deposits <br />associated with the North Fork of the Gunnison River, the localized shallow alluvial /colluvial areas in <br />the stream drainages, and ground water in the lenticular sandstones and the Rollins Sandstone of the <br />Mesaverde Formation. <br />The most significant occurrence of ground water in the general area is associated with the alluvium of <br />the North Fork of the Gunnison River, located approximately two (2) miles southeast of the mine portals <br />and 1,500 feet lower in elevation. Significant alluvial sand and gravel deposits averaging 34 feet thick <br />exist along the North Fork from the mouth of Terror Creek to the confluence of the Gunnison River. <br />There are numerous wells in the area which draw water from this alluvium; well yields range from 5 <br />gpm to 120 gpm, with average yields of approximately 17 gpm (Section 2.04.7, Volume 1). <br />Steven's Gulch, an ephemeral stream located in the center of the permit area, drains an area of 6.0 square <br />miles and contains several reaches of shallow alluvium /colluvium. Most of these reaches have little <br />Page 9 of 42 <br />