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6. DEVELOPMENT AND EVALUATION OF ALTERNATIVES characteristics of the fine screenings are so much different than those of the existing coarse screenings. Once the flow passes through the screenings channels, separate grit removal would be used for the expanded facilities. These grit removal facilities would be designed to implement new technologies than used in the existing aerated grit chambers. Pretreated effluent from the new facilities could then be routed back to the existing facility where the effluent would be combined prior to preaeration, or the two separate pretreated effluents could be combined downstream of grit removal and routed to primary clarification. Additional grit and screenings loadout facilities would be required as part of the expansion. The major new equipment and processes associated with this alternative include: · Four (4) new fine screens (1/4-inch opening) · Two (2) new screenings washer/compactors · Four (4) Parshall flumes for flow measurement · Four (4) new cyclonic grit separators · Four (4) new grit pumps and cyclones · Two (2) new grit classifiers · Two (2) new screenings/grit hoppers Alternative 2 - Construct New Pretreatment Facility Alternative 2 considers constructing a new pretreatment facility east of the existing influent screw pumps. This facility would be a new standalone facility that would require separate influent pumping up to the influent channels. All of the technologies used in Alternative 1 would be applicable to Alternative 2 except all would be located in the new facility and would be independent. Flows in excess of the new facility capacity would be routed and processed at the existing pretreatment facility. The major new equipment and processes associated with this alternative include: · Four (4) new fine screens (1/4-inch opening) Two (2) new screenings washer/compactors · Four (4) Parshall flumes for flow measurement · Four (4) new cyclonic grit separators · Four (4) new grit pumps, concentrators, and classifiers · Two (2) new screenings/grit hoppers Results For Alternatives 1 and 2, the screenings channels and grit separators would be covered and the odorous air collected and treated in bioscrubbers. The cost comparison developed for each alternative is relative because it does not include the costs associated with odorous air ducting and treatment. The relative capital cost comparison and non-monetary comparison are summarized in Table 6.2.4-1. MWMC_6.0_REVI 1.DOC 6-15