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5 BASIS OF PLANNING 5.1,6 Plant Reliability and Redundancy Criteria New or .expanding treatment works are required to meet min~um standards for mechanical, electrical, fluid systems, and component reliability in accordance with EPA's policy. This is to ensure that the treatment facilities will operate effectively on a day-to-day basis and that capabilities are provided for satisfactory operation during power fmlures, flooding, peak load's, equipment failures, and maintenance shutdowns. These reliability and redundancy standards are important to ensure that unacceptable degradation of the receiving water will not occur as a result of the interrupted operation of specific treatment operations or processes. In that regard, standards have been established for three classes of wastewater treatment works. The Reliability Class I definition is applicable for the WPCF. Thi~ reliability designation is based on the possible beneficial uses that may be negatively affected by a WPCF failure. The Reliability Class I definition consists of the following: "Works which discharge into navigable waters that could be permanently or unacceptably damaged by effluent which was degraded in quality for only a few hours. Examples of Reliability Class I works might be those discharging near drinking water reservoirs, into shellfish waters, or ~n close proxhnity to areas used for water contact sports." Table 5.1.6-t lists the mJnLmum backup requirements for plant components that may be provided at the WPCF facility in accordance with EPA's Works Design Criteria, Reliability Class I, for sewage treatment plants. In addition to the standards listed in the table, with the exception of prLmary clarification, unit operations will be designed to pass the peak hydraulic flow with one unit out of service. Also, mechanical components in the facility will be designed to enable repair or replacement without violating the effluent limitati~ or control diversion. causing 3'ABLE 5.1.6-1 Reliability C~ass I Requirements MWMC Facility Plan, Eugene-Springfield Plant Component Requirement Raw Sewage Pumps Peak flow with largest unit out of service. Peak flow is defined as the maximum wastewater flow expected during the design pedod of the treatment works. Mechanical Bar One backup with either manual or mechanical cleaning (manual cleaning r~ only two Screens screens). Gnt Removal Minimum of two units. Primary Sedimentation 50% of design flow capaci'~ with largest unit out of sep,~ice. Design flow is defined as the flow used as the design basis of the component. Activated Sludge A minimum of two equal volume basins; no backup basin required. Process Aeration Blowers Supply the design air capacity with the largest umt out of service; provide a minimum of two umts. Air Diffusers Isolation of largest section of d~ffusers (w~thin a basin) without measurably impairing oxygen transfer. Secondary 75% of design flow capacity wIth largest unit out of service. Design flow is defined as Sedimentation the flow used as the design basis of the component. Disinfectant Contact 50% of the design flow with largest unit out of sen/ice. Design flow is defined as the Basin flow used as the design basis of the component. MWMC_5 0_REVS_V~(S.DOC