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<br />MWSI Project <br />Phase" Conjunctive Use Summary Report - DRAFT <br /> <br />August 22, ] 995 <br /> <br />While this assumption is made at this point of study, a more economical alternative may <br />exist by utilizing existing and future treatment units planned for other locations and existing <br />treated water pipelines, Under this alternative, the conjunctive use reservoir would be located as <br />close as possible to the treatment plant location. Under this scheme, a separate groundwater <br />treatment plant is required in the vicinity of the well field to treat groundwater that is fed directly <br />to the distribution system to meet daily demands, The excess from groundwater deliveries would <br />discharge as raw water to the conjunctive use reservoir with treatment when utilized. <br /> <br />A benefit cost analysis of these two options is recommended as part of the Phase 3 Study. <br />This analysis should look at specific storage sites and treatment plants. including the future use <br />ofDW's Foothills plant, and the capacity of the DW's existing treated water pipelines. <br /> <br />Conceptual Costing <br /> <br />Some conceptual costing of the scenarios presented was necessary to evaluate the <br />economics of conjunctive use to determine whether further study is warranted. The costs <br />presented here are a rough approximation of the magnitude of funding re~uired if a large scale <br />conjunctive use plan was implemented, These costs may be high or low and actual costs may <br />vary substantially from those presented. <br /> <br />Tables 7 and 8 present estimates of costs for implementation of the North Metro well <br />field and southern well field conjunctive use scenarios, respectively, as presented herein, These <br />cost tables recognize, but do not fully include, the portion of costs attributable to the participating <br />surface water system's delivery system, A "surface water charge" ("SWC") for use of surface <br />water supplies, including borrowing ability, is set at 2,500 per acre-foot and this cost is added to <br />reflect a initial surface system cost. <br /> <br />The initial subtotal represents the costs to bring a raw water supply to the vicinity of the <br />demand area for distribution. This cost can be compared with costs presented for other projects <br />which would have brought raw water supplies to the metropolitan area, to the vicinity of use. <br />The cost per acre-foot for the North Metro well field conjunctive use plan is estimated at $8,472 <br />per acre-foot for the groundwater system, or $10,972 with the surface water charge. The raw <br />water cost per acre-foot for the southern well field conjunctive use plan is estimated at $6,141 per <br />acre-foot for the groundwater system, or $8,64] with the surface water charge. <br /> <br />The costs in Tables 7 and 8 then add treatment and distribution costs to deliver these <br />supplies to each water provider along the distribution main route, These costs increase the <br />funding requirements to $13,632 per acre-foot for the North Metro plan and $11,441 per acre- <br />foot for the southern plan, again with surface water charges included. <br /> <br />Project costs in Tables 7 and 8 for this plan include costs for raw water pipelines, well <br />fields, water rights, the collection system, peak reservoir(s), recharge infrastructure, water <br /> <br />4\ <br />