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ATTACHMENT 4 To 05-06-04 Draft MWMC Minutes facility plan, Current maximum month values are used as surrogate parameters for ammonia] The Master Plan concludes: "For BOD, the E/SWPCF has substantial remaining capacity to about 2030 as a result of lower than design per capita loadings and historical growth rates (page 462). It also speaks to TSS. "The results of remaining capacity, as measured by TSS, are also substantial, to about 2026 (page 462). DEQ, in its 2002 Fact Sheet [Again, these are based on 1996 values and were not updated to reflect the new NPDE$ permit] and evaluation discusses the different summer (dry season) and winter (wet season) BOD and TSS permit requirements. It concludes: "A review of recent monitoring data indicates the permittees should generally be able to comply with the permit limits. No changes from the.previous permit are proposed... An 85 percent removal efficiency limit is included in the proposed permit to comply with federal requirements.[ This requirement added significant difficulty to comply with the permit as a result of the dilute wet weather flows. For example, if influent concentrations of TSS are 100 mg/L due to high I/I volumes of l/I, then the plant must meet 85% removal, which translates to an effluent concentration of approximately 15 mg/L. This is significantly lower than the concentration limit of 30 mg/L required on a monthly basis.] An examinatiOn of the DMR data indicates the permittee will be able to meet the limit with the current facilities (page 10). The Draft Facilities Plan indicates that our permit has a Maximum Week TSS permit limit / removal requirements of 28,000 lbs / day and that CBOD has a Maximum Week requirement of 24,000 lbs/day. Actually, the permit does not refer to Maximum Week requirements. The permit chart refers to Monthly Average lbs/day, Weekly Average lbs/day, and Daily Maximum pounds. [This is correct, but the effluent limits must be met for the average of all 7-day periods, including the maximum 7- day average period (or maximum week)] CH2MHill chose to convert the requirement into Maximum week terms rather than use the measurements provided by DEQ in the permit. [lhe weekly permit requirements do not change, they are set for any ?-day period, whether you call it weekly average, or maximum week] The answer would appear to be the same as why we lost all of our dry weather capacity under the System Development Charge Methodology. Rather than using the Monthly Average measurement provided in the permit to compare to the Monthly Average capacity of 49 mgds (apples to apples), the decision was made to convert the data to Maximum Week lb/day and compare that number to the average flow design capacity of 49 mgd (apples to oranges). Dry season mass limitations for both CBOD and TSS outlined in the NPDES permit are based on the current dry season flow of 49 mgd. The mass limit requirements must be met for the highest 30-day flow period in the dry season Attachment 4 Page 13 of 17 4-16