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5. BASIS OF PLANNING <br /> <br />FIGURE 5.1.3-1 <br />Dry Weather Maximum Month Effluent Concentration Requirements <br />Based on Existing Mass Load Limitations and Projected Flows <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> 12.0 85,0 <br /> <br />  75.8 <br /> 10.0 - _ Current Effluent Concentration - -~---~'~- 75.0 <br /> '~-- Limit <br /> 8.0 - 65.0 <br /> <br /> 6.0 -- 55.0 v <br /> <br /> LI_ <br /> <br /> 45.0 <br /> 4,0 46.0 - - ~__~-~----- <br /> <br /> 40.1 <br /> 2.0 ~ ~_ ~--~- - ~-3 ;'.~' ....... 35.0 <br /> /~5 35.7 I <br /> <br /> 31.3 <br /> <br /> 0.0 25.0 <br /> 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 <br /> <br /> Year <br /> <br /> ,~ CBOD and TSS Concentration ---*- Dry Weather Max Month Flow ~ Average Dry Weather Flow <br /> <br />Similarly, wet season maximum month mass limitations for both CBOD and TSS as outlined <br />in the NPDES permit are based on the average wet season flow of 75 mgd. Although <br />significantly higher, concentration limits are also specified in the NPDES permit for wet <br />weather. Percent removal requirements also apply. Figure 5.1.3-2 illustrates the anticipated <br />maximum month CBOD and TSS concentrations that result from projected flows and <br />unchanged mass limitations as specified in the existing NPDES permit. These are shown <br />relative to the anticipated concentration and percent removal requirement. However, <br />because peak wet weather flows are very dilute, it is the percent removal requirement that <br />limits effluent CBOD and TSS during critical wet weather flow periods and this is the most <br />difficult to achieve. <br /> <br />MWMC_5.0_REV8DOC 5-5 <br /> <br /> <br />