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...;:-L._ ~ . . PROJECT PROPOSAL FOR CASTLE PINES CORE HOLE ANALYSIS DENVER BASIN, COLORADO Deep bedrock aquifers in the Denver basin increasingly are being developed as sources of water for domestic and municipal use. The hydrology and aquifer characteristics of aquifers 1,000 to 3,000 feet deep often are difficult to determine because of limited number of wells and inaccessibility of the deep water-yielding units. Water produced from these aquifers is valued at more than $2,000 per acre foot in much of the Front Range area. Colorado statutes limit annual pumpage from these aquifers partly on the basis of the volume of recoverable water in storage as measured by the aquifer characteristic specific yield; thus, accurate estimates of aquifer characteristics are of great economic importance in this water-short area. The Castle Pines water district, near Castle Rock, has recently undertaken a core-drilling program in an attempt to collect a complete sequence of rock core through the 3,000 feet comprising the four principal bedrock aquifers of the Denver basin. A somewhat limited laboratory analysis of core is planned in an attempt to define aquifer characteristics at the drill site. The availability of this core, which is of exceptional quality, creates an unique opportunity to further study and define the characteristics of the Denver basin bedrock aquifers. It is proposed that additional research be conducted on the core and the core hole to better define the characteristics at the site and to develop or improve analytical techniques that allow more rapid and accurate assessment of aquifer characteristics at other points in the Denver basin. The additional work also will improve the understanding of the geology and hydrology of the bedrock aquifers in the basin. The work is to be conducted as a joint undertaking of the Colorado State University, Jehn & Wood, Inc., and the U.S. Geological Survey. Three principal areas of investigation include: (1) detailed laboratory analyses of core samples, (2) geophysical logging and log analysis, and (3) aquifer testing. This work will result in comparison of core analyses data based on very small samples of aquifer materials with larger scale sampling obtained from geophysical logging, and finally with aquifer test results that sample a still larger volume of aquifer materials. Colorado State University primarily will be responsible for laboratory analyses of the core and analysis of geophysical logs as outlined below. OBJECTIVE The objective of the work proposed for Colorado State University is to systematically investigate the response of selected geophysical well logs as a function of specific yield. The goal is to establish a correlation between well-log response and specific yield that can be used to determine specific yield from well logs, thus eliminating the necessity for expensive and time consuming coring and laboratory measurements.