Metropolitan Council

Metropolitan Council Environmental Services Info Item: Infiltration/Inflow Mitigation Program Metropolitan Council Environment Committee November 8, 2011 Kyle Colvin, Assistant Manager, Engineering Services A Clean Water Agency

Presentation Outline • I/I Surcharge Program Overview • Task Force Recommendations • Measured Excessive Peak Events • Communities with I/I Work Plans • Qualified Work & Expenses • Total Regional Work Efforts • On-going I/I Mitigation Program • Task Force Recommendations • Revised Water Resources Management Policy Plan • Similarities and Differences to 2007 Surcharge Program • Determination of Peak Flow Thresholds or “Goals” • Implementation Schedule

2004 Task Force • Findings • Sufficient capacity with normal I/I to accommodate future growth. • At current levels of excessive I/I, future regional growth cannot be accommodated without extensive system capacity expansion. Cost for additional regional system capacity: $900 Million Mitigation “Excess” I/I at local level: $150 Million

2004 Task Force • Recommendations • MCES design standard for peak flow allowance is reasonable and its use should continue. • Communities with excessive I/I should be accountable for excess costs to regional system. • MCES must pursue strategy of I/I flow reduction rather than system expansion. • Council shall implement a Demand Charge in 2013 for continued excessive I/I flow to system.

2007 I/I “Surcharge Program” • June 2004 -June 2010: Monitoring for excess I/I • 2007-2011: Communities implement I/I mitigation plans • 2012: Council extends deadline for completing work • Two communities take advantage of additional year • Community given choice to implement I/I mitigation plan vs. Surcharge • Capped Surcharge Communities • Additional time given to complete work if cost of mitigation plan exceeds 25% of their annual Municipal Wastewater Charge • Five communities apply for cap extension, one completes work early

Regional Wastewater Summary Surcharge based on excess MGD peak only @ $384,000 per MGD (Estimated 2013 Rate). Hourly Metered Flow 3-year Average

I/I Excessive Communities Arden Hills Maplewood St. Anthony Bayport Medicine Lake St. Bonifacius Bloomington Medina St. Louis Park Chanhassen Mendota St. Paul Chaska Minneapolis Stillwater Columbia Heights Minnetonka Tonka Bay Eagan Minnetonka Beach Vadnais Heights Eden Prairie Mound Waconia Edina New Brighton West St. Paul Excelsior New Hope Farmington Newport Golden Valley Oakdale Greenwood Orono Hopkins Osseo Lakeville Plymouth Lauderdale Roseville LilydaleSavage Long Lake Shoreview Maple Plain South St. Paul Summary Total: 47 Communities

Local Mitigation Efforts Public Infrastructure • Investigative studies, system modeling, inspections, etc. • Pipe line rehabilitation/replacement • MH and lift station wet well rehabilitation • Storm water control projects Private Property • Cross connection discovery and disconnection • Sump pump/foundation drain disconnection program • Rain leader disconnection program • Service line inspection/repair/replacement

Local Reported Expenses • 2010 figure includes $52 million reported expenses from Minneapolis for work completed in 2004-2010. • 2011 Expense documentation from communities due to Council by 3/31/12. Figure based on work plans for 2011.

Mitigation Effort Results • 2006-2010 Dry Climate Period characterized by lower ground water tables and fewer intense snowmelt/rainfall events. • Complexity of rainfall events & response analysis • Lowered annual goal/threshold due to lower 3-year flow average

2010 Demand Charge Task Force • Created in 2010 to address need for implementation of Demand Charge in 2013 • Report Recommendations • Delay implementation of a Demand Charge • Develop and implement on-going I/I program • Continue to determine allowable I/I by metershed using peaking factors. • Council Actions • Sept. 8, 2010 – Amend Water Resources Management Policy Plan • Changes implementation of demand charge from specified year start to a “trigger” criteria. • Sept. 22, 2010 – Demand Charge Task Force Report • Accepts DCTF report • Authorize staff to implement procedures for “On-going” I/I reduction Program.

On-going Program Comparison to Surcharge Program 4-Year 5-Year On-going 5-Year (sunset) Yes No 10-Years 3-Years Yes No

On-going I/I Program • Adjustment for Growth • Estimated Flow from growth within 10-year rolling period • Add 50% of Growth flow to 10-year average flow • Adjustment for Water Conservation & I/I Mitigation Work • Estimated flow reduction within 10-year rolling period that is not reflected in 10-year average • Add 10% (1% per year of 10-year rolling avg.) to 10-year average flow.

On-going I/I Program • Adjustment for I/I into Council Interceptors • Estimated peak flow reduction to individual exceedances based on existence of interceptors within communities. • Reduction based on proportion of regional wastewater system size & length to total wastewater system size & length (local + regional). Example Peak Hourly exceedance would be reduced by 0.32 MGD

On-going I/I Program • Implementation Schedule • November/December – Communities notified of goals/thresholds Jan. 1, 2012 - June 30, 2012 July 1, 2012 - June 30, 2013 (Peak Flow Measurement) (Peak Flow Measurement) 2013 2014 (Community Work Plans) (Community Work Plans) • MCES continual effort to assess program effectiveness

Questions Kyle Colvin Engineering Services Group 651-602-1151 kyle.colvin@metc.state.mn.us http://www.metrocouncil.org/environment/ProjectTeams/documents/DemandChargeTaskForce_Final%20Report_September%202010.pdf

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