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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />'. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Section 3 - Development of Alternatives <br /> <br />demand of 7 mgd in the year 2020, or over 17 days at the average flow of 2.5 mgd in the <br />year 2020. The reservoir volume can also be compared to the maximum month <br />demand. The City does not have monthly data available, but based on similar usage <br />patterns in Durango and Denver, the maximum monthly demand is estimated to be <br />about 15% of the annual demand, or about 420 AF. The 132 AF volume is about 31% of <br />this amount. This volume provides a reasonable level of protection in order to allow <br />time to make repairs or carry out inspection to the SWSP without impacting service to <br />the City. <br /> <br />The reservoir is proposed to be uncovered. An uncovered reservoir will be subject to <br />evaporation losses and contamination from windborne particles. However, these items <br />are typically not significant for raw water reservoirs. A change in water quality <br />regulations or increased concerns about evaporation would require a further <br />assessment. <br /> <br />Options: <br />In addition to the 132AF size suggested by the NCWCD criteria, the City also evaluated <br />reservoirs of 150 AF and 200AF. The costs for the different sizes were $1.376M for the <br />132 AF size, $1.516M for the 150 AF size and $1.870M for the 200 AF size. Detail of cost <br />is provided in Table 3.1 and a figure is shown in Appendix C. The City staff compared <br />the increased cost of a larger reservoir with the decreased risk to service and decided <br />that the 132 AF reservoir was suitable. <br /> <br />MONTGOMERY WATSON <br /> <br />Page 34 <br />