Laserfiche WebLink
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 Fork <br />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 offine-grained, buff-colored, lenticulaz sandstones, gray <br />shales and thin, lenticular coal beds. The sandstones predominate and are highly lenticular, discontinuous <br />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. The <br />sediments of this formation are weathered volcanic rocks. The Ohio Creek conglomerate is the basal unit <br />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 l/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 and <br />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 on pages 27 to 41 of Section 2.04 and on pages I l4 to 138 of <br />Section 2.05.6 of Volume 1. Water quality documentation may be found in Volume 4 and is supplemented <br />by annual hydrologic reports prepared since 1982. For a description of the ground water hydrology of the <br />mine area and permit revision area and a discussion of the impacts of mining on ground water, please refer <br />to the Hydrologic Balance portion and the Probable Hydrologic Consequences portion of Section B of this <br />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, [he localized shallow alluvial/colluvial areas in the <br />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 the <br />North Fork of the Gunnison River, located approximately two (2) miles southeast of the mine portals and <br />1,500 feet lower in elevation. Significant alluvial sand and gravel deposits averaging 34 feet thick exist <br />along the North Fork from the mouth of Terror Creek to the confluence of the Gunnison River. There are <br />numerous wells in the area which draw water from this alluvium; well yields range from 5 gpm to 120 <br />gpm, with average yields of approximately 17 gpm (page 31 of 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/coliuvium. Most of these reaches have little <br />ground water except during periods of stream flow. The most significant area of alluvium/ colluvium <br />occurs in the N W 1/4 of Section 13, Township 13 South, Range 92 West (Steven's Gulch wellfield), where a <br />25-foot-thick sandstone outcrop has created a topographic restriction such that a considerable thickness of <br />alluvial sands and colluvial material have been deposited. Test wells drilled by the applicant indicate that <br />the alluvium in this area can support a pumping rate of approximately 28 gpm (Ground Water Hydrology <br />12 <br />