02-11-2019 Council Packet - Laserfiche WebLink

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CMP Part 4B. Sanitary Sewer Plan City of Orono Community Management Plan 2020-2040 Part 4B, Page 11 A comparison of the dry weather flow versus average annual flow versus the average daily flow in the peak rain fall week of that year by metershed for 2021-2016 is given in Table 4B-10. Dry weather flow is calculated as average flow during the months of January through February. The peek weather week is the week is the week with the most accumulation of rainfall. The purpose of this comparison is to give a general indication of the extent of I/I in the region. The data does show a significant difference between peek rain week average and dry weather and average annual flows which indicates I/I. Further action taken by the city starting in 2014 to address I&I appear to be reducing the magnitude of the impact particularly for inflow. The City prohibits the connections of foundation drains and roof leaders to the sanitary sewer system, and requires disconnection of the same. These ordinances are attached as Appendix 4B- B. City code prohibits the discharge of storm water to the sanitary sewer system and requiring the disconnection of existing I/I sources (Sec. 14-189. - Prohibited discharges of groundwater/stormwater into the sanitary sewerage system). The city does experience a high amount of home rebuilds, especially along the lake shore which coincides with a large portion of the municipal sewer system. All new construction is inspected for possible cross connection as part of the sewer connection permit process. In addition, the City has routine activities directed at recognizing and correcting I/I. During the City’s annual sewer system maintenance activities, 20% of the system is cleaned and televised to locate leaks or service connections with continuous flows. Appropriate corrective measures are then initiated with the affected property owner. The results of the inspections are used to develop and prioritize the City’s sewer rehabilitation projects. For the past 5 years and programmed in to the future the city allocates ~$250,000 per year for sewer improvement projects to address I&I issues. The City will consider additional education programs about I/ I. Year M435 Average Annual Flow (MGD) M435 Dry Weather Average Flow (MGD Peek Rain Event Week Average Daily Flow (MGD) M431 Average Annual Flow (MGD) M431 Dry Weather Average Flow (MGD Peek Rain Event Week Average Daily Flow (MGD) Average Annual Flow (MGD) Dry Weather Average Flow (MGD Peek Rain Event Week Average Daily Flow (MGD) Estimated Clearwater Flow (I&I) (MGY) 2012 0.4 0.33 0.77 0.08 0.08 0.15 0.48 0.41 0.92 27.57 2013 0.48 0.31 1.06 0.09 0.08 0.12 0.56 0.39 1.18 63.08 2014 0.53 0.37 1.2 0.09 0.08 0.14 0.61 0.45 1.33 60.46 2015 0.4 0.32 0.45 0.09 0.09 0.09 0.48 0.41 0.58 31.49 2016 0.45 0.4 0.67 0.1 0.1 0.11 0.54 0.49 0.78 18.4 Table 4B-10 Dry and Wet week I & I Comparison