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9.0 Environmental Report 9.1 Introduction This chapter describes potential environmental impacts associated with alternatives for the construction and operation of expanded MWMC facilities. The analysis includes a description of potential impacts to the physical, biological, and human environment in the immediate vicinity of the expanded facilities, as well as impacts to the receiving waters of the Willamette River at the WPCF outfall. The alternatives include MWMC's preferred alternative (System1 Alternative 5) Parallel Primary/Secondary Treatment, and the agency's next best alternative (System Alternative 4) High-Rate Clarification. To compare the project alternatives and potential environmental impacts that could occur if the facilities are not expanded, the analysis also includes a third alternative, the No Action Alternative (System Alternative 1). Because of insurmountable technical difficulties, Alternatives 2 and 3 were considered and eliminated as viable alternatives in this Facilities Plan (see Chapter 7.0). Therefore, an analysis of these alternatives is not included in this Environmental Report. To provide a basis for identifying how the physical layout of the current facilities will differ from potential future expansions and upgrades, a brief description of MWMC's main facilities is provided below. 9.1.1 Current Process Overview Currently, wastewater is channeled to the WPCF via 800 miles of Eugene-Springfield sanitary pipes and 47 pump stations (MWMC, 2004). At the WPCF, influent undergoes primary and secondary treatment. Biosolids are pumped to facultative sludge lagoons at the BMF and wastewater is disinfected before being discharged into the Willamette River. Water Pollution Control Facility (WPCF) Wastewater entering the WPCF undergoes four treatment phases prior to discharge into the Willamette River. These phases (preliminary, primary, secondary, and disinfection), as well as biosolids management at the facility, are described below. Proliminaty Troatmont. Preliminary treatment consists of receiving wastewater from the regional collection system, removing sand and debris, reducing the size of solids, and injecting air (aeration) to remove odorous gases (City of Eugene, 2004). The facility has available four grit removal chambers (each with a volume of 101,000 gallons) and four preaeration chambers (each with a volume of 152,000 gallons) - these are used according to 1 The Facilities Plan identifies various component alternatives and makes specific recommendations for these alternatives. The Environmental Report consists of a review of potential impacts for the entire system that makes up the WPCF. Therefore, to avoid confusion in how the term "altemative" is used, the two project altematives in the Environmental Report and the No Action Alternative are described as System Alternatives 1, 4, and 5. MWMC_9.0_REV14.DOC 9-1