Protection of an Aquifer - A Case History

Abstract

At the request of a Colorado Ground Water Management District Board of Directors, we studied the bedrock aquifers within and in the immediate vicinity of the District. The purpose of the study was to develop bases for the effective and meaningful rules, regulations, and conservation measures to be adopted by the District. Our study included the compilation of data on the deep aquifers to develop an understanding of the suballuvium geologic formations so existing and future water rights can be protected while allowing optimum development protected while allowing optimum development of ground water resources from the deeper aquifers. The tabulation of municipal, commercial and other significant water supply wells completed in the bedrock aquifers was included in an engineering geologic report. BEDROCK AQUIFERS The results of our hydrogeologic study show that there are four significant bedrock aquifers within the District. These are: Dawson-Arapahoe sands Laramie sands Fox Hills sands Pierre transition zone sands These bedrock aquifers occur at or near the surface within the District as shown on Plates I and II. These aquifers are made up of sands and sandstones which are interlayered with shale. The dip is toward the south-southeast into the Denver Basin. Plates III, III-A and IV are geologic cross-sections which show how these aquifers occur at depth. These cross-sections also show the correlation of the sands over considerable distances and the manner in which the sands are separated from each other by relatively impermeable shale. Dawson-Arapahoe Sands This aquifer occurs in the southwest one-third of the District, as shown on Plates I and II. This aquifer is defined Plates I and II. This aquifer is defined as sands and sandstone, ranging in grain size from fine to very coarse, which overlie the predominantly shale section of the Laramie formation. The Dawson-Arapahoe aquifer occurs from the surface to a depth of approximately 800 feet in the immediate vicinity of Strasburg and approximately 1,200 ft. at the southwest corner of the District boundaries.