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City of Roseville March, 2008 so the allowable peak flow is 10.03 (4.01 * 2.5) mgd. As the average flow declines, the allowable flow also declines, raising the possibility that a peak flow rate that is considered allowable one year, may be considered excessive in the future, During runoff conditions following a rain event or snowmelt period, the flows increase markedly due to infiltration and inflow (Ill) entering the sanitary sewer system. In September 2007, the City wastewater flow peaked in response to a 1.83 inch rainfall event. The peak hourly flow rate, recorded as the "net" of the formula calculation was: Table 3 -Peak Hourl Flow in m d followin 1.83 inch rainfall event on 5e tember 19,2007 Meter Formula Peak Hourl Flow Rate in m d M046-(M049+M050+M051+M052+M054+M055+M055A) 11.13* * Note This rate is calculated from the MCES Meter data, however, the City did not receive a notice that there was excessive slow as a result of this storm event. III. Temporary Flow Metering Temporary flow meters were installed in eight (8) manholes to subdivide the City of Roseville as shown on Figure 1. The temporary meters consisted of a transducer placed in the flow channel, connected to a flow meter/ data logger. The flow meter collects readings of flow depth and velocity from the submerged transducer. These values are then input into a formula and a flow rate is estimated. The eight (8) temporary flow meters were installed in the system from July 19, 2007 to August 29, 2007. This period was generally dry; however 2.05 inches of rainfall were received over a two day period on August 27 and 28, 2007. The flow data from the temporary meters are summarized in the following table: Table 4 -Summa of Tem ora Flow Meterin Data in m d Dry Weather Flow (8123/07) Peak Hourly Flow (8128/07) Meter A 0.41 * 0.85* Meter B 0.53 1.17 Meter C 0.14 0,24 Meter D 1.80 2.84 Meter E 0.07 0.17 Meter F 0,21 0.37 Meter G 0.35 0.54 Meter H 0.21 0.38 `Note: Meter A data is not considered reliable due to continuing debris buildup around transducer. IV. Analysis of flows The flow meters provide basic flow quantification and can be used in a number of ways to estimate an l/l quantity and make some predictions about possible sources of the Ill based on the flow patterns, The data can also be combined with other available City data to prioritize areas and maximize rehabilitation efforts. The data analysis included a number of steps as described below. The actual analysis for each "meter shed" is presented in a series of Figures in the Appendix, and the results are summarized in Table 5. Packground Data, o The estimated number of "Residential Equivalent Connections (REC)" and the length of the sanitary sewer tributary to the mater location were obtained form the City graphical information system (GIS). o The Monthly Flow data from the past three years were obtained from the MCES for their meters. o Data from the temporary meters were compiled. Parameters for Comparison o Estimate annual Ill volume and treatment cost using "base" flow analysis Page 5 of 12