Laserfiche WebLink
3.Z.8 Ground Water Hydrology <br />Ground water information is found in Sections 2.04.5, 2.04.7 and Exhibit 7 of the PAP and in <br />Colowyo's Annual Hydrologic Reports. Ground water occurs as isolated, perched aquifers in <br />interbedded and lenticular sandstones and coals and within isolated alluvial aquifers. Base flow <br />in the two perennial streams in the general azea (Good Spring Creek and Wilson Creek) comes <br />mainly from ground water discharge from alluvial aquifers in the stream valleys. <br />Stratigraphically, the Trout Creek Sandstone is the major regional aquifer in the azea. It is <br />approximately 800 feet beneath the lowest coal seam to be mined. The principal rechazge for the <br />aquifer is to the south of the permit azea in the headwaters of Taylor and Goodspring Creeks. <br />There is no continuous, regional ground water system on the pemut azea above the flood plain of <br />Goodspring Creek. No saturation was encountered in any ofthe-beds to be mined in test holes <br />drilled by W.R. Grace and Company and the USGS (information contained in the PAP and the <br />.Northwest Colorado EIS). <br />The Trout Creek Sandstone outcrops north of the permit area, where ground water is dischazged <br />at 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 <br />the southern limb of the Axial Basin Anticline. Due to the impervious nature of the. Mancos <br />Shale, ground water flow in either the deep bedrock units of`the Williams Fork and Iles <br />Formations or the alluvial aquifers of Goodspring and Wilson Creeks is discharged to the. streams. <br />where they flow across the Maneos Shale; <br />3.2.9 Surface Water Hydrology <br />Surface water, information is .found in Sections 2114.7 and 4.05; Maps 11;127 12A;.32_and 37; <br />and Exhibit 7 of the PAP. The permit azea is drained by two perennial stream: Goodspring Creek <br />on the east and Wilson Creek on the west. Taylor Creek, an intermittent stream located just <br />inside and generally parallel to the west boundary of the pemut azea, and generally parallel to <br />Wilson Creek, flows into Wilson Creek north of the rail loadout. Several ephemeral drainages <br />occur on the permit area;.including the Streeter Drainage. This drainage profile was raised as a <br />result of excess spoil fill in the Streeter Canyon, the deepest fill (the Streeter Fill) neaz the <br />confluence of Streeter Drainage and Goodspring Creek. These drainages aze tributaries to Milk <br />Creek, which.flows into the Xampa Ricer about seven miles north aE the permit.area. . <br />Precipitation averages 18 inches annually on the property and runoffrs limited. Flows in the , <br />drainages aze mainly in response to snow melt or intense thunderstorm events_ <br />Water sampled from the drainages is quite hazd, dominated by calcium and magnesium cations <br />and bicarbonate and sulfate anions. The relatively high alkalinity and pH of the system impedes <br />the solubility and transport of heavy cations, thus minimizing potential toxicity problems <br />associated with heavy metals or acid drainage. <br />No alluvial valley floors (AVF's) exist within the area to be mined. However, the alluvial <br />deposits of Goodspring Creek, Wilson Creek, and lower Elkhorn Creek meet the geomorphic and <br />October 21, 2002 15 <br />