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5. BASIS OF PLANNING TABLE 5.1.1-1 Existing NPDES Discharge Requirements and Limitations for the WPCF MWMC Facilities Plan, Eugene-Springfield (1) No wastes shall be discharged from these outfalls and no activities shall be conducted which violate water quality standards as adopted in OAR 340-41-0445, unless the cause of the discharge is due to storm events as allowed under OAR 340-41-120 (13) or (14) as follows: (2) Raw sewage discharges are prohibited to waters of the state from November 1 through May 21, except during a storm event greater than the one-in-five-year, 24-hour duration storm, and from May 22 through October 31, except during a storm event greater than the one-in-ten-year, 24-hour duration storm. If an overflow occurs between May 22 and June 1, and if the permittee demonstrates to the Department's satisfaction that no increase in risk to beneficial uses occurred because of the overflow, no violation shall be triggered if the storm associated with the overflow was greater than the one-in-five-year, 24-hour duration storm. ~ Average dry weather design flow to the facility equals 49 mgd. Summer mass load limits based on average dry weather design flow to the facility. Winter mass load limits based on average wet weather design flow to the facility equaling 75 mgd. The daily mass load limit is suspended on any day in which the flow to the treatment facility exceeds 98 mgd (twice the design average dry weather flow). The treated effluent discharge has mass load and concentration limitations for CBOD5 and TSS established for the dry season (May 1 - October 31) and the wet season (November 1 - April 30). These current mass load limitations are the same as for the previous NPDES permit, and these are based on the standards for the Willamette Basin. The permit requires 85 percent removal of BOD5 and TSS, and the permit also allows for the daily mass load limitations to be suspended on any day that the influent flow exceeds 98 mgd (or twice the design average dry Weather flow). The permit does not address effluent blending or selective treatment operation methods that are used by the WPCF when plant flows exceed the maximum day hydraulic capacity. Under these conditions, a portion of the primary effluent flow is directed to the chlorine contact basins and blended with secondary effluent prior to disinfection. Treated effluent also includes limitations for ammonia, bacteria (E. coli), pH, total residual chlorine, and excess thermal loading (during May 1 - Oct. 31). The ammonia and excess thermal load limitations are new to the 2002 permit. The tmtreated emergency SSOs have specific limits on the seasonal timing and storm event conditions that create circumstances such that these discharges are unavoidable and allowable under state law [OAR 340-41-120 (13) or (14)]. The third category of discharge that is addressed in the NPDES permit is reclaimed wastewater. MWMC is constructing a reclaimed water pipeline from the WPCF to the BMF to provide water to the planned poplar plantation and the BMF's belt filter presses. No reuse is permitted without meeting specific permit conditions and providing a specific plan for its use. The permit specifies that prior to any use of reclaimed water it must receive at least Level II or Level III treatment as defined in OAR 340-55, and must meet specific bacteria limitations. MWMC_5.0_REV8_VKS.DOC ~3