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<br /> The lowermost member of the Mesa Verde Formation, the Rollins Sandstone, is a
<br /> white to buff-colored, well-sorted, medium-grained sandstone, ranging from
<br /> 150 feet to 200 feet thick in the permit area. The Lower Coal Member overlies
<br /> the Rollins Sandstone and consists of interbedded sandstones, siltstones, coals,
<br /> and shale. The unit averages 265 feet thick in the permit are and bears three
<br /> significant coal seams--the A, B, and C seams. A massive sandstone 25 feet
<br /> to 225 feet thick lies at the top of the Lower Coal Member and separates it
<br /> from the Upper Coal Member.
<br /> The Upper Coal Member is approximately 220 feet thick, containing shales, silt-
<br /> stones, sandstones, and the D, E, and F coal seams. The Orchard Valley mine will
<br /> be located in the lowermost seam, the "D" seam. At the mine site, the coal is
<br /> immediately overlain and underlain by shale. See Figure 2.04.1, Typical Litho-
<br /> graphic Section Roof and Floor Rock of the "D" Seam, page 34, Section 2.04 of
<br /> Volume 8. The "D" seam overburden ranges from approximately 500 feet to 2,000
<br /> feet within the permit area. The thickness of this seam decreases from 26 feet
<br /> at the outcrop to 8 feet at the northern edge of the permit boundary. The "D"
<br /> seam dips from the outcrop area in the South five percent to the North, and the
<br /> strike is North 880 West.
<br /> Overlying the Upper Coal Member is the Barren Member of the Mesa Verde Group.
<br /> This unit consists of interbedded and interlensed sandstones, siltstones, and
<br /> shales of varying thicknesses. This unit is thought to be of terrestrial origin
<br /> and, as a result, the sandstones and the coals are highly lenticular, discon-
<br /> tinuous, and of limited lateral extent in outcrop. This unit ranges up to
<br /> 1 ,500 feet thick and outcrops throughout the southern portion of the permit
<br /> area.
<br /> ` Three categories of potential aquifers occur in the general area. These are
<br /> alluvial and terrace deposits associated with the North Fork of the Gunnison
<br /> River, the localized shallow alluvial areas in the Stevens Gulch and Terror
<br /> Creek drainages, and groundwater in the lenticular sandstones and the Rollins
<br /> Sandstone of the Mesa Verde Formation.
<br /> The most significant occurence of groundwater in the general area is associated
<br /> with the alluvium of the North Fork of the Gunnison River, located approximately
<br /> 2 miles southeast of the mine portals and 1,500 feet lower in elevation. Sig-
<br /> nificant alluvial sand and gravel deposits averaging 34 feet thick exist along
<br /> the North Fork from the mouth of Terror Creek to the confluence of the Gunnison
<br /> River. There are numerous wells in the area which draw water from this alluvium,
<br /> with an average yield of 17.4 gpm. See Table 2.04.3, Well Printout, pages
<br /> 56-57, Section 2.04, Volume B.
<br /> Stevens Gulch, an ephemeral stream, located to the West of the permit area, drains
<br /> an area of 6.0 square miles and contains several reaches of shallow alluvium.
<br /> Most of these reaches have little groundwater except during periods of stream
<br /> significant area of alluvium occurs in the NW'ir of Section 13,
<br /> T13S, R°2W, -where a 25-foot thick sandstone outcrop has created a topographic
<br /> rests_ -_c suc;' t' at a ccnsiderable thickness of a?lurial sands has been de-
<br /> posited by the ephemeral flow. Test wells drilled by the applicant indicate
<br /> that the alluvium in this area can support a pumping rate of approximately
<br /> 28 arm, and as a result, the applicant has installed a production well and
<br /> currently uses this water for domestic use, dust control, and fire control. See
<br /> Ground [eater Investigation of Stevens Gulch for Colorado Westmoreland, Inc. and
<br /> Well Completion Report SG-2 in the Ground Water appendix of Volume 2, and Figure
<br />
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