Laserfiche WebLink
<br /> <br />`~u~~`d?, iron, manganese, s?lenium and sulfate in excess of U.S. Puolic <br />Health Service drinking water standards (9rodgen and Giles, 1977). TDS levels <br />range from 76-600 mg/1. Poor quality and li;nited yields from water-bearing <br />units associated with the coals preclude significant use of this water in the <br />Twentymile Park Basin. <br />The :Jolf Creek coal-overburden aquifer consists of the Wolf Creek coal seam <br />and the overlying sandstone and siltstones. The Wolf Creek seam is only <br />partially saturated in the Little Middle Creek tract. Hydraulic conductivity <br />of the Wolf Creek aquifer is approximately 0.009 ft/day. Ground water from <br />the Wolf Creek coal is calcium/magnesium-bicarbonate type containing <br />approximately 450 mg/1 TDS with a pH of 7.4. <br />The Wedge coal overburden aquifer is composed of the Wedge coal and overlying <br />75 feet of shale and interbedded, lenticular sandstones. The hydraulic <br />conductivity of this aquifer ranges from .001 ft/day to .5 ft/day. Generally, <br />hydraulic conductivities decrease with increasing overburden thickness. Pump <br />tests of monitoring well 021-87-26 with a top of screen depth of 1518 feet and <br />well 006-82-488 with a top screen depth of 987 feet have permeabilities of <br />.008 ft/day and .09 ft/day respectively. Shallower wells 008-77-85 (40 feet) <br />and 008-74-6 (216 feet) near the edge of the Twentymile Park basin have <br />perneabilities of .495 ft/day and .455 ft/day respectively. When considering <br />ground water flow through the entire basin the lower permeabilities will be <br />the limiting factor in predicting flow rates. <br />The Lewis Shale contains limited ground water. Use of water from this unit is <br />considered insignificant in the Twentymile Park Basin. The Lewis Shale acts <br />as a confining layer creating artesian conditions in the underlying Twentymile <br />Sandstone. Reported well yields from the Lewis Shale are generally less than <br />5 gpm. Total dissolved solids concentrations range from 272 to 4,230 mg/L. <br />Water from the Lewis Shale may contain concentrations of iron, manganese, <br />nitrate, selenium and sulfate in excess of U.S. Public Health Service (1962) <br />standards (Brodgen and Giles, 1977). <br />The unconsolidated alluvial deposits of the Yampa River and its tributaries <br />produce the highest reported yields of ground water in the basin. Well yields <br />range from 5 gpm along the upper tributaries to 900 gpm along the Yampa <br />(Brodgen and Giles, 1977). Domestic and stock watering are the principal uses <br />of water from the alluvial aquifers. Hydraulic conductivities particularly in <br />the Yampa River alluvium, are sufficient locally to support long-term, <br />high-yield wells for municipal, industrial and irrigation needs. Total <br />dissolved solids concentrations range from 82 to 2,970 mg/1. Water quality in <br />the alluvium depends on the quality of water contributed from underlying <br />bedrock aquifers and the source of the alluvial material, and the water <br />quality of the recharging stream. Alluvial ground water may contain <br />concentrations of arsenic, iron, manganese, nitrate, selenium, and sulfate in <br />excess of U.S. Public Health Service Drinking Water Standards (Brodgen and <br />Giles, 1977). <br />The recharge, discharge and movement of ground water within the alluvial <br />aquifers are controlled by: <br />The gradient and flow of the associated stream; <br />32 <br />