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entisol occur to a limited extent within the area to be disturbed on steep, south-facing slopes. The <br />very thick Silas loam soil developed from alluvium within narrow bands along the larger ephemeral <br />drainages. <br />The predominant hill-slope soils have relatively thick, loamy textured mollic epipedons, well suited <br />for reclamation use. Salvageable thickness of these soils averages from 12 inches to 30 inches. <br />Subsoils in these units are somewhat marginal, due to heavier texture or excessive cobbles. The <br />Silas loam soil along the drainage valley bottoms is generally suitable for salvage to depths of five <br />feet or more. <br />3.2.8 Ground Water Hydrology <br />Ground water information is found in Sections 2.04.5, 2.04.7 (Volume 1 for the East Pit, West Pit, <br />Section 16 Pit, Facilities Area and Gossard Loadout and Volume 12 for South Taylor) and Exhibit 7 <br />of the PAP and in Colowyo's Annual Hydrologic Reports. Ground water occurs as isolated, perched <br />aquifers in interbedded and lenticular sandstones and coals and within isolated alluvial aquifers. Base <br />flow in the two perennial streams in the general area (Good Spring Creek and Wilson Creek) comes <br />mainly from ground water discharge from alluvial aquifers in the stream valleys. Stratigraphically, <br />the Trout Creek Sandstone is the major regional aquifer in the azea. It is approximately 800 feet <br />beneath the lowest coal seam to be mined. The principal recharge for the aquifer is to the south of the <br />permit azea in the headwaters of Taylor and Goodspring Creeks. There is no continuous, regional <br />ground water system on the permit azea above the flood plain of Goodspring Creek. No saturation <br />was encountered in any of the beds to be mined in test holes drilled by W.R. Grace and Company <br />and the USGS (information contained in the PAP and the Northwest Colorado EIS). <br />The Trout Creek Sandstone outcrops north of the permit area, where ground water is discharged at <br />the surface. The Mancos Shale underlies the Iles Formation and forms the base of the regional <br />ground water system in the azea. This shale is exposed at the surface north of the permit area, in the <br />southern limb of the Axial Basin Anticline. Due to the impervious nature of the Mancos Shale, <br />ground water flow in either the deep bedrock units of the Williams Fork and Iles Formations or the <br />alluvial aquifers of Goodspring and Wilson Creeks is discharged to the streams where they flow <br />across the Mancos Shale. <br />3.2.9 Surface Water Hydrology <br />Surface water information is found in Sections 2.04.7 and 4.05 (Volume 1 for the East Pit, West Pit, <br />Section 16 Pit, Facilities Area and Gossazd Loadout and Volume 12 for South Taylor); Maps 11, <br />1 I A, 12, 12A, 32 and 37; and Exhibit 7 of the PAP. Surface water information for the South Taylor <br />and Lower Wilson areas can be found in Section 2.04.7(2) Surface Water Resource Information and <br />Section 4.05 Hydrologic Balance in Volume 12. Tables 2.04.7-30 to 36, Volume 12, also present <br />surface water information for the South Taylor and Lower Wilson azeas as do Figures 2.04.7-22 to <br />32, again found in Volume 12. Map l0A and Map 11A in Volume 14 provide monitoring and other <br />hydrologic feature locations for the South Taylor and Lower Wilson areas. The permit area is <br />Proposed Decision and Findings of Compliance 4 May 2007 <br />Perini[ Revision 02 Page 19 <br />