05-29-07 Item 7C, Infiltraton and Inflow Study

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1&1 5/24/2007 Page 3 The following table shows initial calculations for the allowable peak flow from the City of Arden Hills and the estimated actual peak for each of the meters. Metershed Allowable Peak Flow (mgd) Estimated Actual Peak Flow (mgd) 51 (Ingerson and Hamline) 1.89 2.6 54 (Prior and Co. Rd. D) 0.84 1.05 59 (W. Round Lake Road) 1.23 1.7 The MCES program as implemented includes an annual surcharge for a period of five years starting in 2007. During the five-year period, the surcharge funds from each community would be held in a separate account that the community could draw from to fund III identification and reduction efforts. Based on the peaks from 2003, the City of Arden Hills has been surcharged $100,100 per year for five years, assuming a $10 million annual MCES program to reduce system flows. If Arden Hills' III remains above the allowable peak flow rate after the initial five years, the surcharge will continue; but the collected funds would no longer be available to the City. Instead, they would be turned over to MCES to cover the costs of improvements to the interceptor and treatment systems to accommodate III flows. However, any reductions in the III rates achieved in that five years would be taken into consideration in calculating future III surcharges. City staff has been working on eliminating potential sources ofI/I within the City's system. This is accomplished through televising, lining, pipe replacement, chemical grouting, and visual inspections of our sanitary sewer pipes and manholes. However, the 1&1 continues to cost the City money, because MCES bills us based on the amount of water treated. The City bills our residents based on water meter records. III flows into the sanitary system unmetered. We have no mechanism of billing users for the treatment of clear water flowing into the system. As a result, this is a direct cost to the City's utility funds and is passed along via our utility rates to our residents. To identify ways in which we can further reduce this cost to the City, the City of Roseville solicited proposals from 5 consulting engineering firms to further focus our search for III sources within the City of Roseville. Since Arden Hills has many of the same challenges with III as Roseville, Arden Hills was included as a part ofthe RFP. The potential for economies of scale on projects such as this is one of the partnership opportunities realized by the Joint Powers Agreement for Engineering Services. By identifying these sources, we will be able to reduce the flow by taking corrective actions, prevent potential surcharges, and reduce the costs for treating clear water. The scope of this proposal is to assist us in quantifying the system III. This is accomplished through isolating sources of the III and identifying an action plan for each City. The scope of the study includes identifying and prioritizing sources of the III and identifying potential reduction projects. The proposed III study includes 4 major tasks. These are: