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4.0 Wastewater Characteristics <br /> <br />This chapter presents the existing wastewater characteristics at the WPCF and consists of an <br />evaluation of historical flows and loads, as well as historical per capita and peaking factor <br />calculations. It also presents an analysis that correlates current plant wastewater flows with <br />current rainfall data in an independent effort to produce flow peaking factors. PWWFs have <br />been determined using an extensive collection system modeling approach. This historical <br />data analysis, in conjunction with the rainfall data analysis and the collection system <br />modeling, provide the basis for future flow and load projections. The "Flow and Load <br />Projections" technical memorandum presented a historical flow and load analysis, rainfall <br />flow analysis, population projections, and projections for future flows and loads based on <br />two independent methodologies. The "Wet Weather Peak Flow Analysis" technical <br />memorandum presented the collection system modeling methodology to develop the peak <br />wet weather flows. The following is a summary of the information presented in those <br />technical memorandums. <br /> <br />4.1 Wastewater Flow Characteristics <br />Two separate analyses of historical flow data were conducted. The first analysis includes <br />assessment of 12 years of historical plant data. The second analysis follows the Guidelines]or <br />Making Wet-Weather and Peak Flow Projections for Sewage Treatment in Western Oregon: <br />MMDWF, MMWWF, PDAF, and PIF, from the Oregon DEQ (DEQ, 1996). <br /> <br />4.1.1 Historical Seasonal Flow Analysis <br />Historical flow data from May 1990 through May 2002 were evaluated to determine <br />average, maximum month, maximum week, and maximum day flows. The data analysis <br />was broken up into dry and wet weather seasons. The two seasons align with the effluent <br />requirements as specified in the WPCF's NPDES permit. Flows at the WPCF are measured <br />at the influent Parshall flume. Dry weather includes flows occurring between May 1 and <br />October 31. Historical dry weather average and maximum month flows are depicted in <br />Figure 4.1.1-1. Wet weather includes flows occurring between November 1 and April 30. <br />Historical wet weather average and maximum month flows are depicted in Figure 4.1.1-2. <br /> <br />MWMC_4.0_REV9.DOC 4-1 <br /> <br /> <br />