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INFLOW AND INFILTRATION FACTS Inflow and Infiltration - or 1/1 - are terms that describe clear water that enters wastewater collection systems and consumes capacity of the conveyance and treatment systems. Excessive flows can result in public and environmental health concerns if untreated sewage discharges to basements, rivers, or lakes. Each has unique sources, methods of entry, and effects on the wastewater collection system. Both are costly to communities and utility ratepayers due to increased conveyance and treatment costs. Inflow is typically stormwater that increases peak flow in the wastewater system during and after rainfall events from point sources such as broken manhole covers, sewer cleanouts, sump pumps, foundation drains, and rain leaders. Infiltration is typically groundwater that gradually enters the wastewater system through cracks and openings in sewer mains, service laterals, joints, and deteriorated manholes. Infiltration increases base flow in the wastewater system and removes water from the natural hydrologic cycle, which could otherwise recharge the regional aquifers. Regional Ongoing 1/1 Mitigation Program The Met Council has convened multiple community-based task force committees since ?003 which developed the Ongoing 1/1 Mitigation Program. The program goals include: • Protect public and environmental health by preventing untreated sewage discharges to basements and the environment • Minimize regional and local cost to convey and treat excessive 1/I • Ensure the vitality and sustainability of the regional water resources Success of mitigation Property owners, local community, and Met Council efforts related to 1/1 mitigation and water conservation have contributed to wastewater flow reduction across the region. • The annual regional wastewater flow has been reduced by roughly nine billion gallons per year since 2005. The flow decrease has occurred even as precipitation volumes, rainfall intensities, and populations have increased. • Two significant rainfall events occurred in October 2005 and June 2014. The 2014 rainfall event included higher precipitation and higher soil moisture, with lower peak flows recorded at the Metro and Blue Lake wastewater treatment plants when compared to the 2005 rainfall event. What can property owners do to mitigate 1/1? • Disconnect unlawful connections to the sanitary sewer system. Residents should contact the local Public Works department to help find reasonable alternatives. 11-2016 I www.metrocouncil.org METROPOLITANC O U N C I L 51