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• The Dakota, while thinner, and generally containing more shaley or silty interbeds than the <br />Cheyenne Formation, does have more gravels and an overall higher hydraulic conductivity <br />(K) value than the Cheyenne. <br />• The Kiowa Shale is the most recognizable formation in the driller's logs. It is also more <br />uniform and wider spread than previously thought, but the sparse pump test data and <br />continuity of water table conditions indicate the Kiowa is a leaky aquitard, made more so by <br />poor well completion practices in the area. <br />• The Cheyenne Sandstone is still fully saturated throughout most of the area and should be <br />protected and monitored. <br />• The Jurassic Morrison and Entrada are rarely penetrated and are considered to be a leaky <br />aquifer between the Cheyenne and Dockum. Although the Entrada is a potential aquifer, it is <br />generally too deep and overlain by more productive water -bearing formations and thus not a <br />common water exploration target. Some authors include it as part of the Dockum aquifer. <br />For purposes of this report, the Jurassic formations are undifferentiated. <br />• The Dockum is a very significant aquifer in the southeastern part of the area. The formation <br />is reported to be 300 to 570 feet thick and may be 700-800 feet thick in the subsurface. It is <br />the aquifer penetrated in many high capacity irrigation wells in southeastern Colorado and <br />southwestern Kansas. Generally wells are drilled 100 to 200 feet into the Dockum and <br />completed open hole, and some have 300 to 400 feet of penetration. Some of the better <br />driller's logs have recorded about 65% sand and silt in the formation. The lower portions of <br />the formation are essentially untested and for purposes of this report's proven water reserve <br />calculations, only the upper 200 feet of the formation was included. <br />• We have revised the estimated economically recoverable water for each of the aquifer units <br />from the Phase 1 Study. The overall estimate has been reduced from 32 million acre-feet to <br />22 million acre-feet due in part to more accurate information on the extent of the aquifer units <br />and the uncertainty of reserves in the lower portion of the Dockum aquifer. <br />• Recommendations have been made for changes in the management rules that apply to both <br />existing and new wells in the District. <br />• Based upon the results of this study, it may be possible to consider the Dockum Aquifer as a <br />closed basin in Colorado for purposes of administration. <br />It was a pleasure meeting with your Board in Lamar and we look forward to presenting the final <br />report to you and the rest of the District at the meeting in Walsh on January 28, 2002. <br />McLaughlin Water Engineer's sincerely appreciates the opportunity to serve you and looks forward to <br />further assisting the District in preserving your precious water resources. <br />Sincerely Yours, <br />Wayland Anderson, P.E., <br />Senior Project Manager <br />E. Thomas Cavanaugh, P.G., C.P.G. <br />Senior Geologist <br />99-028.003\Phase 2 Report\SHP Cover Letter <br />