7C, Final Draft of I&I Report - Laserfiche WebLink

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City of Arden Hills March 2008 Table 3 - Peak Hourlv Flow in mod followina 1.83 inch rainfall event on Seotember 19,2007 Meter Number Peak Haurlv Flow Rate in mad M051 1.20 M052 0.10 M054 0.57' Ma59 US' "Note: Calculated peak flow Tate exceeds allowable flow listed in Table 2 III. Temporary Flow Metering Temporary flow meters were installed in three manholes to subdivide the meter sheds of Meters M054 and M059 in an attempt to isolate III flows to smaller areas and focus rehabilitation efforts. The locations of the temporary meters are shown on Figure 1. The temporary meters consisted of a transducer placed in the flow channel, connected to a flow meterl 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 three 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 Table 4. Table 4. - Summrnf Temoorarv Flow Meterlno Data in mad Meter 1 Meter 2 Meter 3 Drv Weather Flow (Sf23/071 0.42 . 0.07 0.13 Peak Hourly flow (S/28/07) 1.15'" 0.15 0.27 "Note: Temporary meter number 1 was Installed to diVIde the Meter 059 Meter Shed and attempt to isolate pos$jble :/1 sources. This meter was operating for about 8 weeks so no long term average flow data are available; however, some dry weather and peak data are available for evaluation. The flow data recorded at meter 1 suggest flow rates in excess of those recorded at the downstream meter M059 and therefore the data are considered unreliable for comparison at this time. IV. Data Analysis The flow meters provide basic flow quantification and can be used in a number of ways to estimate an III quantity and make some predictions about possible sources of the III 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. Background Data. a The estimated number of "Residential Equivalent Connections (REC)" and the length of the sanitary sewer tributary to the meter location were obtained from the City graphical information system (GIS). a The Monthly Flow data from the past three years were obtained from the MCES for their meters. a Data from the temporary meters were compiled. Parameters for (omparison a Estimate annual III volume and treatment cost using "base" flow analysis . The average daily wastewater flow from January is assumed to be a "base" flow that includes a minimal amount of infiltration. . The average daily flow from January is subtracted from the annual average daily flow and the annual III volume and treatment cost are calculated. a Per Connection flow rate o The annual average daily flow, January daily flow, and the peak month daily flow are divided by the number of Equivalent Residential Connections (ERC). Page 5 of 12