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DEVELOPMENT AND EVALUATION OF ALTERNATIVES <br /> <br />TABLE 6.2.1-2 <br />Facility Requirements for Alternative 1 at 2025 <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Total Required <br /> Secondary Capacity Capacity <br /> NPDES Permit Condition Aeration Basins Clarifiers (mgd) (mgd) <br /> <br />DWMM 2 (4 cells each) 9 60 59 <br />DWMW 2 (4 cells each) 10 90 86 <br />WWMM 2 (4 cells each) 10 119 111 <br />WWMW 2 (4 cells each) 10 165 165 <br /> <br />Alternative 2 - Expand Existing Secondary Treatment Facilities to Match Current Operations <br />This alternative requires expansion of the secondary treatment facilities to match the current <br />operational practices for biological treatment and secondary clarification. For this operation, <br />all of the primary effluent and RAS is fed to the first aeration cell in each aeration basin. <br />Sludge volume indexes from over 2600 days of operation show that 25 percent of the <br />measurements fall between 150 and 175 mg/g; thus, 175 mg/g was used as the basis for <br />estimating future capacity with expanded facilities. Table 6.2.1-3 summarizes the dry and <br />wet season design criteria used for analysis for expanding the existing secondary system. <br /> <br />TABLE 6.2.1-3 <br />Design Criteria: Traditional Plug-Flow Aeration Basins <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Parameter Dry Season Wet Season <br />Temperature, degrees C 15.6 12.5 <br />Nitrification Safety Factor 2.0 N/A <br />Aerobic Volume 100% 100% <br />Aerobic SRT, days 7.8 5 <br />SVI, ml/g 175 175 <br /> <br />Table 6.2.1-4 summarizes the facility requirements for expanding the existing secondary <br />treatment facilities. <br /> <br /> MWMC_6.0_REV11.DOC 6-9 <br /> <br /> <br />