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<br />Comprehensive Sanitary Sewer Plan <br />City of Arden Hills, MN <br />WSB Project No. 3455-20 Page 17 <br />I/I Analysis <br />Arden Hills’ sanitary sewer system currently consists of approximately 49 miles of gravity main, <br />14 lift stations, and 3.6 miles of forcemain. Approximately 26 percent of the gravity mains have <br />been lined in the last fifteen years, primarily in the southern half of the system. Approximately 38 <br />percent of the residential housing in the City was constructed before 1970. The only I/I <br />evaluation that has been done for pre-1970 era private services is the televising of their wye <br />connection during the trunk main televising listed in Table 12. I/I reduction activities are <br />discussed in greater detail in the next section. <br />A comparison of the dry weather flow versus average annual flow for the MCES Meter Service <br />Areas within the City is given in Table 11. Dry weather flow is calculated as the average flow <br />during the months of December through February. The purpose of this comparison is to give a <br />general indication of the extent of I/I in the region. <br />Table 11. Dry Weather Flow vs. Average Annual Flow <br />Meter Service <br />Area Year Dry Weather Flow <br />(MGD) <br />Average Annual Flow <br />(MGD) <br />M051 <br />2012 <br />2013 <br />2014 <br />2015 <br />2016 <br />0.270 <br />0.216 <br />0.275 <br />0.307 <br />0.337 <br />0.307 <br />0.327 <br />0.398 <br />0.327 <br />0.364 <br />M052 <br />2012 <br />2013 <br />2014 <br />2015 <br />2016 <br />0.027 <br />0.021 <br />0.022 <br />0.021 <br />0.026 <br />0.029 <br />0.030 <br />0.031 <br />0.023 <br />0.030 <br />M054 <br />2012 <br />2013 <br />2014 <br />2015 <br />2016 <br />0.167 <br />0.210 <br />0.159 <br />0.182 <br />0.212 <br />0.169 <br />0.208 <br />0.196 <br />0.172 <br />0.212 <br />M059 <br />2012 <br />2013 <br />2014 <br />2015 <br />2016 <br />0.228 <br />0.246 <br />0.244 <br />0.254 <br />0.255 <br />0.233 <br />0.261 <br />0.285 <br />0.265 <br />0.261 <br />The disparity between dry weather flow and average annual flow was greatest in 2013 and 2014 <br />and was most pronounced in Metersheds M051 and M052. Much of the sanitary sewer lining <br />work, listed in Table 12, was completed in these Metersheds in 2013 and 2015, so the City <br />expects to see a reduction of I/I in these areas. Based on the difference between average and <br />dry weather flow, averaged over 2012-2016, the estimated amount of clearwater entering the <br />system is 90,000 gallons per day. <br /> <br />Dr <br />a <br />f <br />t <br /> <br />11 <br />/ <br />2 <br />0 <br />/ <br />2 <br />0 <br />1 <br />7