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5534 (' indicates that Alternative 2 is estimated to require 381 wells and Alternative 3A is estimated to require 298 wells, for a difference of 83 wells. It does seem reasonable to conclude that Altemative 2 will require more wells than Alternative 3A, but the number of additional wells should be considered to be a rough estimate, In the draft report, Alternative 3A was selected over Alternative 2, even though Alternative 3A requires more wells and has a greater estimated overall cost. If the difference in the number of required wells has been overestimated (due to underpredicting the well capacities), then the cost disadvantage of Alternative 3A would be even lower, and it would still be the preferred alternative, However, planners should also be aware of the possibility that the modeling might underestimate the required number of wells, meaning that the cost difference between Altematives 3A and 2 might be greater than estimated. Without additional data on the performance of wells as the aquifer becomes unconfined and the water table drops into the aquifer, it seems unlikely that the reliability of the local well model can be improved significantly. Summary ( In conclusion, we feel that the modeling that has been performed provides adequate information for allowing planners to choose a preferred alternative between the various water supply alternatives being considered for the South Metro Study Area, However, we caution that the regional model in its current form may be inappropriate to use to assess other groundwater issues in the basin, We feel that there are improvements that could still be made to the regional model. Attempts were made to address some of the problems inherent in the SB74 model as summarized by Stan Robson (USGS) and the SB-74 Technical Review Committee, However, we believe significant questions remain regarding the ability of the model to accurately simulate stream/alluvial aquiferlbedrock aquifer interactions. Similarly, we believe the ways in which the models address aquifer layering and well production under unconfined conditions continue to need refinement. Ultimately, to improve the modeling effort, additional field work may be needed in these areas, As well performance data are collected as the Denver Basin aquifers gradually drain, additional evaluation of the predictive capability of the local well model could be made as well. References 1, Hydrosphere, Inc; HRS Water Consultants; Black & Veatch, Inc.; Rick Giardina & Associates; Trout, Wflwer & Freeman, P,C.; and Mulhern MRE, Inc., August 2003, Draft (Privileged and Confidential) South MetrO Water Supply Study, variously paginated. (' '- . Page 4