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4. WASTEWATER CHARACTERISTICS <br /> <br />4.1.2 Historical FI0w Statistics <br />Peaking factors are commonly used to estimate future peak flow conditions and are <br />frequently based on analyses of historical average and peak flow data. The methods used <br />for estimating peaking factors involved analysis of historical peaking factors for the years <br />1990 through 2002 for both dry and wet weather conditions and the DEQ methodology. <br />Peaking factors for flow and load events (maximum month, maximum week, maximum day <br />and peak hour) are ratios of the particular seasonal events to the corresponding seasonal <br />averages. <br /> <br />Tables 4.1.2-1 and 4.1.2-2 present the historical dry and wet weather flow per capita and <br />peaking factor statistics, respectively. <br /> <br />TABLE 4.1.2-1 <br />Historical Dry Weather Flow StatistiCS <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Maximum <br /> Flow Per Capita Month Peaking Maximum Week Maximum Day Peak Hour <br /> (gpcd) Factor Peaking Factor Peaking Factor Peaking Factor <br /> <br /> Minimum 105 1.1 1.2 1.5 2.3 <br /> Average 128 1.3 1.7 2.3 2.8 <br /> Maximum 147 1.5 2.8 3.9 4.0 <br /> <br />TABLE 4.1.2-2 <br />Historical Wet Weather Flow Statistics <br />MWMC Facilities Plan, Eugene-Springfield <br /> <br /> Maximum <br /> Flow Per Capita Month Peaking Maximum Week Maximum Day Peak Hour <br /> (gpcd) Factor Peaking Factor Peaking Factor Peaking Factor <br /> <br /> Minimum 139 1.2 1.5 2.3 (a) <br /> Average 227 1.6 2.5 3.4 (a) <br /> Maximum 275 1.4 1.9 2.8 (a) <br /> <br />(a) Determined by collections system modeling, see Wet Weather Peak Flow Technical Memorandum. <br /> <br />4.1.3 DEQ Methodology Peaking Factor Analysis <br />The Guidelines for Making Wet-Weather and Peak Flow Projections for Sewage Treatment in <br />Western Oregon: MMDWF, MMWWF, PDAF, and PIF (DEQ, 1996) present instructions on <br />calculating current flow rates. A statistical analysis of historical data from 2000 and 2002 <br />was used to predict current peak flow rates. The maximum month flows for dry weather <br />and wet weather are predicted using rainfall recurrence data obtained from the National <br />Oceanic and Atmospheric Administration, National Climatic Data Center, Climatography of <br />the United States No. 20, 1971-2000, Eugene Mahlon Sweet Airport Station (NOAA, February <br /> <br />MWMC_4.0_REVS.DOC 4-3 <br /> <br /> <br />