2000-02-10_GENERAL DOCUMENTS - C1981041

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.'cross dip" from the river. The entire sequence of Mesaverde that overlies the Cameo coal zone, behaves as a single hydrologic unit. The water table in the permit area and adjacent area can be directly correlated to its elevation relative to the Colorado River. Rock formations and alluvium below the level of the river are gravity-fed and are saturated with water from the river. Due to the clastic differentiation and lensing of sandstones and shales in the area together with the low permeability of the rock, the strata above the zone of saturation act to confine the body of groundwater. Therefore, the water table is located at approximately the same elevation as the Colorado River. This fact is important in defining the hydrologic impact on the water-bearing strata by the mine operation (see the Probable Hydrologic Consequences section of this document, Section C.II.). There are four primary water bearing zones that may be directly or indirectly affected by the mine operation: the Colorado River alluvium, the undifferentiated sandstone lenses in the Mesaverde above the coal seam, the Cameo coal seam, and the Rollins sandstone unit below the coal seam. There are no aquifers in the permit or adjacent area that can store and transmit water of sufficient quality or quantity for beneficial use. A September, 1997,study included in the permit application package confirms that the Rollins Sandstone in the permit area does not meet the regulatory criteria of an aquifer. Laboratory analyses have shown groundwater in the permit vicinity to be high in salts and of poor quality. Therefore, no beneficial uses of groundwater exist in the permit or adjacent area. No groundwater rights have been adjudicated on or adjacent to the permit area to date. Only one groundwater well (an alluvial well) exists adjacent to the permit area; it is used for stock watering. Please refer to Section C.II.I. (Probable Hydrologic Consequences) for further hydrologic information, including the groundwater monitoring plan. Additional information on hydrology can be found in Tabs 7, 17 and 18,of the permit and Section C.II. of this document. Surface Water Hydrology A general description of the surface water hydrology of the permit area is found in Volume 2, Tab 7 of the permit application. Maps displaying the general surface water hydrology are found in Exhibits 1 and 17 of that document. Please see Section C.II. of this document for a discussion of the Probable Hydrologic Consequences (PHC) of the Roadside Portal Mines on surface water quantity and quality and for a further discussion of the surface water monitoring plan. Alluvial valley floors(AVF's)are discussed in Section C.XI. of this document. The Colorado River is the only perennial stream in the permit area. On the west side of the river, Coal Creek and Jerry Creek flow through the Roadside North Portal portion of the permit area within deeply incised canyons draining approximately 12 and 70 square miles, respectively. Coal Creek, an ephemeral drainage, passes through surface mine disturbance near the Roadside North Portal where the channel has been diverted. Jerry Creek is an intermittent drainage located in the extreme northern portion of the permit area. In addition, a small portion of the permit area drains to Asbury Creek,which enters the Colorado River from the northwest, to the east of Jerry Creek. Flows in all of these drainages occur primarily during spring snowmelt and in response to sudden, high intensity thunderstorms,the latter of which are characterized by high peak discharges, short flow durations and high sediment loads. 14