Resolution No. 4793 - Laserfiche WebLink

Home Browse Search

J~WMC FACiLmES PLAN refined until it met the criterion of keeping maximum water surface elevations in martholes lower than critical elevations. These critical elevations included 3 feet above pipe crown in areas where there were basements. In areas without basements, the criterion was 2 feet below ground surface. Once this criterion was achieved, it became a sub-area solution. A total of 21 sub-area solutions in the East system and 26 in the West system were developed to meet Objective 1. Cost and effect on peak flows and volumes reaching the WPCF characterized sUb-area solutions. The prelLrrrinary hst of sub-area solutions was developed to ensure that all reasonable applications of the four technologies were considered. This preliminary, comprehensive hst resulted in a number of solutions that were clearly inferior to others from cost and implementation perspectives. In addition, a number of solutions were largely redundant, with primary components essentially the same. As a result, sub-area solutions were quickly reduced to a manageable number based on cost, implementation, consistency with ongoing programs, disruption, and redundancy. Four combinations of sUb-area solutions from the East and West systems were selected for further analysis to meet Objective 2. Sub-area solutions from each system with similar features were combined to form systemwide alternatives. The systemwide alternatives were evaluated with the hydraulic model adjusted to reflect implementation of each of the four sub-area solutions. Each systemwide alter~.ative produced a hydrograph at the WPCF that showed the excessive flow and volume that remained after implementation of sub-area solutions. A cost-effectiveness exercise (optimization) using model results combined with cost estimates of components of individual systemwide alternatives was performed to develop systemwide solutions. An economic optimLzation analysis was performed to determine the most cost-effective mix of technologies for managing the excess peak flow rates and volumes at the WPCF for each systemwide alternative. As with the sub-area alternatives and solutions, technologies included system rehabihtation for control of RDII (etther public or pubhc and private), storage, and expansion of primary treatment capacity. Additional conveyance beyond that required for sub-area solutions was found to be unnecessary. $.1.2 Selection The WWFMP CAC and steering committee decided, using the established evaluation criteria and associated discussions, that the solution summarized in Table 6.1.2-1 was most desirable from a cost, implementation, and public acceptance perspective. The selected alternative elements are shown graphically in Figure 6.1.2-1. TABLE 6.1 MWMC Wastewater Collection System Wet Weather Flow Management Plan (WWFMP) SeJected A~temative MWMC Facilities Plan, Eugene-Springfield Component of WWFMP Description ,, Public system rehabilitation in seven sub-basins Sub-Ama Solution E24 (Spdn§~ield) ~, Further investigation in the Gateway ama and remediation as necessary ~ Upgrades to the WBlakenzie pump station MWMC_60~REV~t 1 DOC