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6. DEVELOPMENT AND EVALUATION OF ALTERNATIVES handling, so the footprint required for this facility is relatively small. Experience at other facilities has proven there is very little cost savings gained through retrofitting existing chlorine contact channels with new UV channels over the construction of a new UV facility. Electrical room space requirements vary for different manufacturer's systems. Use of the existing chemical building should be considered for required electrical room space. Flow measurement would be incorporated into the UV facility to allow for UV dose pacing. A standby power source would be required for redundancy. Results The order-of-magnitude capital cost estimates and annual O&M costs are summarized in Table 6.3-3. The 20-year present worth costs are based on the order-of-magnitude capital cost estimates and annual O&M costs over 20 years at an interest rate of 3 percent. The UV costs were based on the Trojan UV4000Plus system. The present value comparison and non- monetary comparison are summarized in Table 6.3-4. TABLE 6.3-3 Summary of Disinfection Alternatives Order-of-Magnitude and Capital Cost Comparison MWMC Facilities Plan, Eugene-Springfield Capital Cost Annual O&M Cost Alternative (millions of dollars) (millions of dollars) I - Hypochlorite Disinfection of Secondary and Primary Effluent $4.1 $0.47 2 - Ultraviolet Disinfection of Secondary Effluent and Hypochlorite Disinfection of Primary Effluent $16.1 $0.46 TABLE 6.3-4 Summary of Disinfection Alternatives Present Value and Non-Monetary Cost Comparison MWMC Facilities Plan, Eugene-Springfield 20-yr Present Worth Cost' Non-Monetary Alternative (millions of dollars) Ratingb I - Hypochlorile Disinfection of Secondary and Primary Effluent $11.1 25 2 - Ultraviolet Disinfection of Secondary Effluent and $23.0 24 Hypochlorite Disinfection of Pdmary Effluent Notes: a 20-year present worth cost is based on capital and annual O&M costs over 20 years. b Non-monetary score is out of a possible maximum score of 30 points. By far the most cost-effective alternative on a capital cost basis is alternative 1, sodium hypochlorite for both SE and PE diversion flows. The O&M costs of alternative 1 are sensitive to increases in energy prices (electricity and natural gas) because of the large amounts of electricity and natural gas required to produce sodium hypochlorite; however, it is unlikely that the variability of the O&M costs will overcome the capital cost difference. Alternative 2 would be easy to operate because sodium hypochlorite disinfection would be MWMC_6.0_REV11.DOC 6-25