2009-09-14_GENERAL DOCUMENTS - C1981019

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stream valleys. Stratigraphically, the Trout Creek Sandstone is the major regional aquifer in the area. It is approximately 800 feet beneath the lowest coal seam to be mined. The principal recharge for the aquifer is to the south of the permit area in the headwaters of Taylor and Goodspring Creeks. There is no continuous, regional ground water system on the permit area above the flood plain of Goodspring Creek. No saturation was encountered in any of the beds to be mined in test holes drilled by W.R. Grace and Company and the USGS (information contained in the PAP and the Northwest Colorado EIS). The Trout Creek Sandstone outcrops north of the permit area, where ground water is discharged at the surface. The Mancos Shale underlies the Iles Formation and forms the base of the regional ground water system in the area. This shale is exposed at the surface north of the permit area, in the southern limb of the Axial Basin Anticline. Due to the impervious nature of the Mancos Shale, ground water flow in either the deep bedrock units of the Williams Fork and Iles i orn.a ions or uic alluvial aquiof %-J U iuig anu vv 11son ?,icekS iS uiSciiai?cu w Me streams where they flow across the Mancos Shale. 3.2.9 Surface Water Hydrology Surface water information is found in Sections 2.04.7 and 4.05 (Volume 1 for the East Pit, West Pit, Section 16 Pit, Facilities Area and Gossard Loadout and Volume 12 for South Taylor); Maps 11, 11A, 12, 12A, 32 and 37; and Exhibit 7 of the PAP. Surface water information for the South Taylor and Lower Wilson areas can be found in Section 2.04.7(2) Surface Water Resource Information and Section 4.05 Hydrologic Balance in Volume 12. Tables 2.04.7-30 to 36, Volume 12, also present surface water information for the South Taylor and Lower Wilson areas as do Figures 2.04.7-22 to 32, again found in Volume 12. Map 10A and Map 1 IA in Volume 14 provide monitoring and other hydrologic feature locations for the South Taylor and Lower Wilson areas. The permit area is drained by two perennial streams: Goodspring Creek on the east, North Fork of Goodspring Creek on the South, and Wilson Creek on the west. Taylor Creek, an intermittent stream located just inside and generally parallel to the west boundary of the permit area, and generally parallel to Wilson Creek, flows into Wilson Creek north of the rail loadout. Several ephemeral drainages occur on the permit area, including the Streeter Drainage. This drainage profile was raised as a result of excess spoil fill in the Streeter Canyon, the deepest fill (the Streeter Fill) near the confluence of Streeter Drainage and Goodspring Creek. These drainages are tributaries to Milk Creek, which flows into the Yampa River about seven miles north of the permit area. Precipitation averages 18 inches annually on the property and runoff is limited. Flows in the drainages are mainly in response to snow melt or intense thunderstorm events. Water sampled from the drainages is quite hard, dominated by calcium and magnesium cations and bicarbonate and sulfate anions. The relatively high alkalinity and pH of the system impedes the solubility and transport of heavy cations, thus minimizing potential toxicity problems associated with heavy metals or acid drainage. Proposed Decision and Findings of Compliance 14 September 2009 Permit Renewal 05 Page 22