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Feasibility Evaluation of the Arkansas Valley Pipeline <br />W ater Works! Committee <br />June 2003 <br />Option 2 -Raw water would be delivered and treated at local treatment facilities (Figure <br />3.3). This would allow entities to blend raw water from local sources with supplies <br />from the new pipeline, prior to treatment. In the case where local supplies are surface <br />water, conventional treatment would be adequate. However, if water supplied from the <br />proposed pipeline is blended with groundwater that requires reverse osmosis treatment, <br />an added filtration step will likely be needed. Local treatment may need to be expanded <br />in order to meet new MCL's unless blending reduces applicable contaminant <br />concentrations to appropriate levels. <br />Option 3 -Raw water would be delivered to several regional water treatment facilities <br />that would serve groupings of cities, towns, and water districts in a particular <br />geographic area. <br />O tion 4 - A "No-Action" option (Figure 3.4) in which the water suppliers downstream <br />from Pueblo would continue to utilize their existing sources of supply, but would <br />upgrade their existing water treatment plants and facilities to satisfy existing and <br />projected standards of the Safe Drinking Water Act. <br />Advantages of an upstream central water treatment plant include expected lower costs per <br />unit of water treated due to economy of scale and easier maintenance and administration of <br />treatment operations. Potential disadvantages include: pumping would be required to <br />maintain minimum pressure in the proposed Arkansas Valley Pipeline, loss of local water <br />supplier control, the Iikely need for additions of disinfectants in the pipeline at intermediate <br />locations to maintain water quality; and the need for higher design standards for the proposed <br />transmission pipeline to protect water quality. <br />Discussions with the Colorado Department of Public Health and Environment (CDPHE) <br />indicate that CDPHE would prefer a new central treatment plant rather than a number of <br />smaller, dispersed regional facilities. CDPHE also recognizes, however, that relying on local <br />plants, as currently practiced in the project area, is a viable option. <br />3.4.2 Option 1-Upstream Central Water Treatment Plant Option <br />For this option, our evaluation assumed that water diverted from Pueblo Reservoir would be <br />treated by a single, 20 mgd surface water treatment plant (WTP) located near the upper end <br />of the proposed pipeline. A final decision on the type of treatment (rapid-sand filtration <br />versus membranes) would be made during preliminary design when source water quality data <br />are analyzed in detail. For purposes of this evaluation, and considering the conservative and <br />proven treatment characteristics of rapid-sand filtration, our cost estimates are based on a <br />rapid-sand filtration process. A single pump station, located at or near the treatment plant, <br />would pump treated water downstream to the end users. Monitoring stations along the <br />32 <br />GEI Consultants, I11C. 01284 03-06-30 Feasf6ility Evaluation Final <br />