Laserfiche WebLink
localized perched groundwater would be located at the depth of the first <br />impermeable layer within the undifferentiated Mesa Verde. Above the river, <br />recharge is mainly by precipitation, but due to the steep topography and the low <br />permeability of the formations, infiltration rates are low. <br />According to the Willard Owens report, rock formations and alluvium below the <br />level of the river are gravity fed and are saturated with water from the river. Due <br />to the interbedding and lensing of sandstones and shales in the area and the low <br />permeability of the rock, the strata above the zone of saturation acts to confine <br />the body of groundwater. This report asserts that the water table lies at <br />approximately the same elevation as the adjacent river. <br />Two of the wells in the Graystone report show water levels above the Rollins <br />Sandstone. The Roadside South Portal well shows a water level elevation <br />approximately 200' higher than the Colorado where it crosses the subcrop of the <br />• Rollins Sandstone. This would indicate some recharge from precipitation along <br />outcrops at a higher elevation than the river or from geologic structures such as <br />shear zones or fault. The low calculated water level elevation for the Roadside <br />North Portal well would indicate very low recharge rates from the river if any. <br />Three stratigraphic units contain groundwater. The first unit is the strata <br />overlying the coal seam. This unit consists of intricately interbedded sandstones <br />and shales of discontinuous nature. Consequently, although very small and <br />locally perched groundwater zones may exist, groundwater moves slowly <br />through and between interconnected sandstone and shale lenses and beds. <br />The thickness of these lenses and beds varies within the Mesa Verde group. <br />The depth of this overburden ranges from 1 to 1900 feet in the project area. <br />• 7-2 (Rev. 9117197) <br />