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Because the City of Orono sanitary sewer collection system <br />has been constructed from a variety of piping materials and is <br />located in variable ground water and topographic conditions and <br />as a result of the 1981 I/I Study* the City developed an ongoing <br />plan for abatement of infiltration and inflow. This plan <br />included the following: <br />1. Routine and onging televising of the system. Where <br />televising indicates sources of infiltration* chemical <br />injection treatment is applied to the source to eliminate <br />the infiltration. This procedure has proved especially <br />effective in the older clay tile portions of the system <br />which are subject to a relatively high potential rate of <br />joint failure and contain a relatively high number of <br />joints. <br />2. Ongoing visual inspection of manholes* and Installation <br />of neoprene lines where they would prove effective in <br />reducing infiltration. <br />3. Installation of manhole guards* a system which <br />eliminates surface water inflow into manholes subject to <br />occasional inundation. <br />4. Ose of state-of*>the**art technology (Ten State <br />Standards) in the design and construction of all new sewers <br />added to the system. <br />The goal of this plan was to limit I/I to no more than 25% <br />of the total flow* and reduction below 25% in all locations where <br />feasible and practical. <br />During the period 1981-1991, NWCC measured-flows varied <br />significantly from year to year* with the lowest flows occurring <br />during drought years. Analysis of the flow rates suggests that <br />in wet years* I/I may still be as much as 1/3 of the total flow.