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I I ,I I I I I I I, I I I I I I I I I I ......t ':1) \.0 CJ c:..~ EXECUTIVE SUMMARY c~ As part of the Phase IB portion of the San Luis Valley Confined Aquifer Study, the study team consisting of HRS Water Consultants, Inc., and Robert Moran, has performed analyses of: - geophysical logs of four deep wells in the aquifer test data from three deep wells in - satellite imagery of the Valley, Va 11 ey the Valley The Objective of the analyses was to add to the database of existing information on the hydrogeology of the deep confined aquifer, particularly hydrostratigraphic unit 3 (HSU-3), which lies at a depth of 2500 feet or more beneath most of the Valley, The studies of Phase IB, of which the analyses presented in this report are a part, are to determine the feasibility of the deep confined aquifer as a source of supplemental water supply for water users in the San Luis Valley. The primary conclusions arrived at by the study team, based on the analyses discussed above, are as follows: Aquifer tests conducted during Task 5 of Phase IA have yielded transmissivity estimates thought to be more representitive of HSU-2 than HSU- 3, the target of this study, due to apparent well completion in both HSU's and apparently much higher transmissivity in HSU-2. Aquifer tests and geophysical logs of the Hooper Pool Well and the Carroll Well (Figure 2.1), run for the present study, indicate that most of the water produced from these wells is from the upper confined aquifer (HSU-2) above a depth of about 2000 feet. The transmissivity estimates derived from aquifer testing of these wells thus is reflective of HSU-2 to a larger extent than HSU-3. This condition is likely to be the case in any deep water well which presently exists in the San Luis Valley. Geophysical logs run for this study in deep wells in the Alamosa area indicate an abrupt ground water quality degradation and increase in clay content below a depth of approximately 2000 feet. This is interpreted to be i