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Metropolitan Water Supply Investigation Proposal Hydrosphere, Inc. Septmber 17, 1993 Page 37 Arapahoe County. When that supply is not available, the Arapahoe County well system would be used to deliver that same 30,000 acre-feet of new supply. The Arapahoe County Utility Advisory Board completed a study entitled "Water Resource Plan, Arapahoe County Water Providers, Phase II Summary Report" prepared by Mulhern MRE, Inc., which is being published this month. This report summarizes the studies that the Utility Advisory Board has completed of a well system capable of delivering 30,000 acre-feet of groundwater a year into systems of water providers across Arapahoe County. The system includes wells, a collection system, a distribution main along E-470/C-470, a 10,000 acre-foot storage reservoir, and a water treatment facility. The study also addressed connections to the Denver Water Department system so that water supply could be delivered to the County providers either through the Denver system or through the County's groundwater system. The summary report also describes a financial analysis completed in the project to identify tap fee costs and financing mechanisms. The Denver Water Department has cooperated in discussions and studies of the Arapahoe County Utility Advisory Board. The Denver Water Department independently completed an evaluation of how their system could be modified operationally to develop additional yield, utilizing the groundwater system as a component of the Denver Water Department's total water supply system. This study, while identifying several operational problems that would need to be overcome, did show the feasibility of increasing firm yield in the Denver system with groundwater supply. In addition, the northern urbanized areas of Douglas County have recencly organized a new Douglas County Water Authority charged with searching out and evaluating new water supplies for their major providers. Douglas County, again, has an enonnous groundwater resource with proven ability to economically produce good quality groundwater. The Arapahoe County plan could readily be mirrored across the County line, thereby significantly increasing the groundwater yield and adding significant efficiencies of scale to the Arapahoe County program. The Douglas County Water Authority has expressed interest in further understanding how to utilize their groundwater resource to leverage further supplies from surface supplies in the mountains. Finally, even though reserving groundwater for periods of drought greatly extends the life of the aquifer systems, there would still be a net depletion in the aquifers over time. Therefore, the Utility Advisory Board has recommended including in the program a component of groundwater recharge. Again, during periods of high water yield from the mountains, excess water supplies could be used to recharge the groundwater system through the same system of wells during periods when water supply needs for Arapahoe and Douglas County are being met through surface water supply delivery. This technology is still relatively new for the Denver area, however, pilot studies such as those completed by the Denver Water Department, The Willows Water District, Parker Water and Sanitation District and Centennial Water and Sanitation District have indicated that such recharge is feasible and have continued studies to improve the technology. Comprehensive Analytical Capability The MWSI Project should aim toward the development of an analytical tool capable of evaluating a variety of methods for increasing metro area water supplies through cooperative operation of individual water supply systems. Ultimately this should include the capability to estimate overall system yield when individual water systems are operated in a cooperative rather than competitive mode. The MWSI Project should also be able to articulate such a mode of operation in terms of prior appropriation language, in order to address such questions