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City of Roseville March, 2008 I, Introduction and Purpose Infiltration /Inflow (I!I) is defined as clear water that enters a sanitary sewer system. This clear water does not require treatment until it is mixed with the wastewater already in the sanitary sewer pipe. Once it is mixed, the combined flow must be conveyed to a treatment facility for treatment before it can be discharged back into the surface water network. The Ill in the system can increase the normal flow in the system enough to stress the conveyance capacity of the pipe network, pumping stations, and the wastewater treatment facilities, In the seven county metropolitan area, the Metropolitan Council Environmental Services (MCES) provides an interceptor sewer system to collect the wastewater from over 100 communities and convey it to one of eight MCES wastewater treatment facilities located around the metropolitan area. Communities own and operate their own local sanitary sewer systems to collect the wastewater from individual buildings within their service area. Any clear water (I/I) entering a local collection system is conveyed to and through the MCES system and directly impacts the available capacity of the MCES interceptor and treatment facilities. The Metropolitan Council appointed a Task Force to identify solutions to the regional I/I problem. The Task Force worked from April 2003 to May 2004 and developed recommendations which were adopted by the Metropolitan Council as Policy in 2004. The Policy established the Ill Surcharge Program that is now in affect with the intent to avoid "hundreds of millions" of dollars in regional infrastructure costs. The MCES currently monitors wastewater flows from all the tributary communities in the service area. With the I/I Surcharge Program an additional step was initiated to monitor peak flow conditions. Briefly, the program establishes a three year average flow for each community or "metershed" within the system. A peaking factor (multiplier) is applied to the average flow to determine an allowable peak flow. The peaking factor was previously adopted by the MCES for design purposes and it ranges from 4.0 for average flows less than 110,000 gallons per day (gpd) to 1.7 for flows over 30.0 million gallons per day (mgd). The MCES reviews hourly flow data from each meter during runoff events and compares the actual "peak hourly" flow to the allowable peak flow. If the actual peak is higher than the allowable peak, the extra flow is considered "excessive" and subject to the Ill surcharge rate of $350,000 per mgd (this rate is annually increased by an inflation factor). The Ill surcharge is calculated for the highest peak recorded by the MCES and the surcharge amount is subdivided into five (5) years of annual payments. If a greater peak is recorded in the five year period, the surcharge amount can be recalculated and increased for the remaining years in the 5 year program term. Surcharges began in 2007 and will run through 2011. Wastewater flow from the City of Roseville is calculated using data measured and recorded at 8 separate MCES flow meters. There are seven meters (M049, M050, M051, M054, M055, and M055A) that measure flow entering the City of Roseville from surrounding communities, and one meter (M046) measuring flow leaving the City of Roseville. The "Roseville" flow is calculated by subtracting the incoming flow from outgoing flow, The number of meters involved in the calculation provides a potential for errors in estimating the Roseville flow, however, considering the extensive interceptor system in the City, this is a reasonable method of establishing the flow, On an average day, the seven (7) influent meters record approximately 25% of the total flow measured at the outlet meter (M046). Meters M051 and M055 provide 7.1 % and 8.7% of the flow, respectively. The remaining five meters are all under 4%. On a peak day the seven influent meters recorded about 21 % of the total flow through the City. The majority of the flow recorded at MCES Meter M046 is generated within the City of Roseville. In 2007, the first year of the program, the City of Roseville did not have an Ill surcharge. However, in 2008 and the four remaining years of the program the City of Roseville will have an annual surcharge of $82, 538, The City has the option to pay the surcharge amount to the MCES, or make I/I reduction improvements to their system that will directly off set the surcharge amount. If the City expends less than the annual surcharge amount, the balance will be collected by the MCES and held in an account for future Ill improvement work. At the end of the five year program if there are any funds remaining in the community`s MCES account, Page 3 of 12