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.o -14- The alluvial formation of Del Agua Canyon contains sufficient potable water to be put to beneficial use. Therefore, it is considered an important aquifer in the vicinity of the mine. The applicant has determined that the aquifer has a transmissivity of about 2000 gpd/ft. and a storage coefficient of 0.01. The aquifer is about 27 feet thick at its thickest point. Water levels vary from about 12 to 25 feet from the surface. Water quality in the aquifer is marginal for domestic use. The concentrations of total dissolved solids, manganese, iron, Lead, and pH occasionally exceed drinking water standards. The aquifer appears to be recharged by the occasional surface water flows and by discharge from adjacent bedrock strata. The ground water leaves the permit area to the east and probably discharges to surface waters downstream. Only limited amounts of ground water occur in the bedrock strata associated with the Trinidad Basin mining operations. Exploration drilling conducted by the applicant encountered no measurable ground water. Springs and seeps do occasionally flow from the coal seams and sandstones in response to snowmelt or precipitation. However, because of the topographic position of the coal seams, only isolated perched aquifers could exist. No significant perched aquifers have been identified by the applicant. Generally, the water from the springs and seeps evaporate rapidly and rarely reach the drainage system. T1~e one regional aquifer in the area, the Trinidad Sandstone, exists about 900 stratigraphic feet beneath the lowest coal seam to be mined. The application is in compliance with the' requirements of this section. VII. A17uvial Vallee Floors - Rules 2.06.8 and 4.24 The applicant conducted an investigation to affirmatively demonstrate that no alluvial valley floors exist within the mine area or adjacent affected area. The information on alluvial valley floors is found in Volume I, Section 6.1 and Volume III, pages 85 to 87 of the permit application. The investigation's study area included all valley floors within 3 miles of the permit area. This three-mile area is the distance generally accepted as adequate, since hydrologic impacts from mining seldom extend this far. The only valley floor identified as having mapable areas of unconsolidated alluvial deposits is the Del Agua Canyon. This canyon is included within the study area for three miles down- stream from the mine. This distance is justified since Carcia Canyon and Vi ana Canyon join Del Agua Canyon about 2 miles do~mstream from the mine. Both canyons make significant streamflow contributions to DeI Agua Canyon. The applicant mapped alluvial deposits on L~1 Agua Canyon from a point one mile upstream from the mine to 3 miles do~,~nstream. This mapped area does exceed the size criteria for potential alluvial valley floors, However, it was noted that much of the existing valley floor is disturbed due to past mining ventures in the canyon. The investigation sought to disprove the presence of an alluvial valley floor based on insufficient water available in i:he canyon to support agricultural activities. under Rule 2.06.8(3)(c)(ii), this would exclude the canyon as an alluvial valley floor.