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6. DEVELOPMENT AND EVALUATION OF ALTERNATIVES TABLE 6.1.2-1 MWMC Wastewater Collection System Wet Weather Flow Management Plan (WWFMP) Selected Alternative MWMC Facilities Plan, Eugene-Springfield Component of WWFMP Description · No Storage Sub-Area Solution W25 (Eugene) · Public system rehabilitation in 21 sub-basins · Installation of valve at 14th and Tyler · Upgrade to screw pumps at treatment plant · No storage Strategy to Manage Excess Flow at WPCF for Existing · Manage 100% of 82 mgd excess flow rate and Conditions 59.4 MG excess volume by adding primary clarification capacity to the WPCF. MG = million gallons mgd = million gallons per day The solution set in Table 6.1.2-1 includes those aspects of the WWFMP that were cost - effective in the optimization analysis relative to competing alternative technologies. Contributing to this recommendation were the following factors: · It is the least-cost alternative. · It relies heavily on RDII reduction of the public system, which is considered to be the most implementable approach to RDII reduction. · RDII reduction has the dual benefit of achieving and maintaining good, long-term system pipeline conditions. · Each city is already performing rehabilitation at various levels; therefore, this alternative builds on current programs. · This alternative is consistent with the current theme within many cities of a sustainable approach to developing infrastructure programs. This approach promotes creating increased efficiency from existing systems versus accepting poor performance from some portions of the system and building more facilities to compensate for them. · It has a minimum of additional pipeline requirements and associated disruption. · It does not require storage facilities that could pose aesthetic and siting issues. The selected systemwide solution was evaluated under estimates of buildout conditions and flows. To achieve sub-area solutions under buildout conditions, additional public-only system rehabilitation was evaluated and found to provide an acceptable solution. The 10-year Wet Weather Flow Management Plan Implementation Schedule is given in Figure 6.1.2-2. As mentioned previously, since the adoption of the WWFMP, both Eugene and Springfield have put into action positive management practices for the wastewater collection system as outlined in the WWFMP, and have aggressively pursued RDII source MWMC_6.0_REV11.DOC 6-5