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

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1&1 5/24/2007 Page 2 surface water. In the sanitary sewer, III is a problem because it uses pipe and treatment capacity that should be reserved for wastewater. In extreme cases, excessive III flows can cause sewer system backups and bypassing at treatment plants. The New MCES Plan: Historically, the MCES has charged communities for III based on the volume of water that was metered in the system without consideration of peak flows. In the past few years, MCES has been working with a task force to develop a new approach to reducing peak III flows that have a significant impact on interceptor and treatment plant sizing. This new approach will result in a surcharge for each community based on the peak flows in their collection system. The MCES will review three years of flow data to develop an average flow. A peaking factor is then applied to the average data to establish an "allowable peak flow rate." This calculated allowable peak is then compared to actual measured peaks to identifY peaks that exceed the allowable. This difference is considered "excessive flow," and is typically related to infiltration and/or inflow. The calculated allowable flow is established as the goal for the City to meet to avoid surcharges. In 2003 the MCES appointed a task force oflocal government representatives to examine the problem of III and propose strategies to solve it. In 2006, the MCES adopted a surcharge program to reduce III based on the recommendations and input from the local community representatives on the task force. Strategies include: . Setting III goals for all communities served by the metropolitan disposal system, and requiring communities to reduce their III to meet design flow standards by 2012. . Requiring all communities to develop and implement an III reduction program and include it in their local comprehensive plan. Communities currently within their III goals will need to develop plans for maintaining acceptable levels as the local infrastructure ages. . Starting in 2007, instituting a surcharge for maximum peak excessive III to provide funding for city III reduction efforts. Communities will have the right to appeal the surcharges, and deferrals may be requested for any surcharge amount more than 25 percent of the municipal wastewater charge imposed by the MCES. . Starting in 2013, instituting a "demand charge" for communities that still do not meet their III reduction goals, funds the MCES would employ to address the problem. . Potentially limiting increased wastewater service to communities with ongoing, excessive 1/1. The Met Council will work collaboratively with communities to reduce III in the wastewater system.