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A. Update on Infiltration & Inflow (I & I)0 CITY OF CHANHASSEN 7700 Market Boulevard PO Box 147 Chanhassen, MN 55317 Administration Phone: 952.227.1100 Fax: 952.227.1110 Building Inspections Phone: 952.227.1180 Fax: 952.227.1190 Engineering Phone: 952.227.1160 Fax: 952.227.1170 Finance Phone: 952.227.1140 Fax: 952.227.1110 Park & Recreation Phone: 952.227.1120 Fax: 952.227.1110 MEMORANDUM TO: Todd Gerhardt, City Manager FROM: Paul Oehme, City Engineer /Dir. of Public Works DATE: January 23, 2012a ' SUBJ: Update on Infiltration/Inflow (I &I) City Project #PW254 BACKGROUND In 2007 the Metropolitan Council Environmental Services (MCES) implemented a surcharge program that strongly encouraged communities that have documented high I &I problems to make improvements to the system or face financial penalties. Forty -six (46) metro communities took park in the program. I &I is a problem because it takes up capacity in the larger regional sewer pipes and treatment plants owned by MCES. During major rain events, this additional surge of water can consume the capacity of sewer pipes, resulting in home backups and overflows into creeks, wetlands and rivers. MCES estimates it would cost the region a minimum of $900 million dollars to build infrastructure large enough to convey the excess flows to the wastewater treatment plants. Senior Center Phone: 952.227.1125 Fax: 952.227.1110 Attachment Web Site www.ci.chanhassen.mn.us G .\ENG\PUBLICTW254 1 &1 \bkgd council ws l &l 012312.doc Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow The surcharge program is now complete and the Metropolitan Council will Recreation Center implement a Demand Charge program starting in 2013. A representative from 2310 Coulter Boulevard Metropolitan Council Environmental Services (MCES) is planning to give a brief Phone: 952.227.1400 update on the new I &I Demand Charge Program. The program again is designed Fax: 952.227.1404 to encourage municipalities to identify and reduce the amount of inflow and Planning & infiltration getting into the local system. A copy of the MCES demand charge Natural Resources program is attached to this background. Phone: 952.227.1130 Fax: 952.227.1110 Staff is also planning to give a brief update on what the city has completed to reduce I &I in the public system. Staff will also present information on what other Public Works communities have done, or are planning to do, to reduce I &I from their systems. 7901 Park Place Phone: 952.227.1300 Staff will also discuss what options the city may want to implement in the future Fax: 952.227.1310 to reduce the amount of I &I getting into the sewer system. Senior Center Phone: 952.227.1125 Fax: 952.227.1110 Attachment Web Site www.ci.chanhassen.mn.us G .\ENG\PUBLICTW254 1 &1 \bkgd council ws l &l 012312.doc Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow It Metropolitan Council Environmental Services Demand Charge Task Force Final Report September 2010 Metropolitan Council Environmental Services 390 Robert Street, North • St. Paul, MN 55101 • (651) 602 -1005 Metropolitan Council Members Chair Peter Bell Council Members Roger Scherer District 1 Natalie Steffen District 9 Tony Pistilli District 2 Kris Sanda District 10 Robert McFarlin District 3 Georgeanne Hilker District 11 Craig Peterson District 4 Sherry Broecker District 12 Polly Bowles District 5 Richard Aguilar District 13 Peggy Leppik District 6 Kirstin Sersland Beach District 14 Annette Meeks District 7 Daniel Wolter District 15 Lynette Wittsack District 8 Wendy Wulff District 16 Council Regional Administrator Thomas Weaver General Manager, Environmental Services William Moore The mission of the Metropolitan Council is to develop, in cooperation with local communities, a comprehensive regional planning framework, focusing on wastewater, transportation, parks and aviation systems, that guide the efficient growth of the metropolitan ara. The Council operates wastewater and transit services and administers housing and other grant programs. General Phone Regional Data Center TTY Metro Info Line E -mail Council Web Site 651- 602 -1000 651 -1140 651- 291 -0904 651- 602 -1888 data.center cgmetc.state.mn.us www.metrocouncil.ore Publication #32 -10 -026 Publication Date Table of Contents Section Executive Summary ...................................... ............................... Introduction.............................................. ............................... . Council's Existing I/I Policy and Program ............ ............................... Demand Charge Task Force ............................ ............................... System Capacity Analysis ............................... ............................... I/1 Program Issues and Recommendations ............ ............................... 2030 Policy Plan Amendment .......................... ............................... 2011 and 2012 Surcharges .............................. ............................... Summary Recommendations ........................... ............................... Page 2 2 in Appendices Appendix A MCES Interceptor System Capacity Analysis Appendix B Ongoing 1/I Reduction Program Appendix C Recommended Water Resources Policy Plan Amendment Executive Summary The Metropolitan Council's 2030 Water Resources Management Policy Plan calls for the Council to implement a wastewater demand charge in 2013 for communities that have excessive inflow /infiltration. The intent of the demand charge would be to defray the cost of providing attenuation (storage) of excessive I/I to avoid overloading downstream facilities. In August 2009, the Council established a Demand Charge Task Force to develop specific recommendations for the demand charge. The Task Force met from September 2009 to August 2010, generally on a bi- monthly basis. Since the beginning of the Council's infiltration/inflow program in January 2007, 46 communities have participated in the program. A total of $46 million of local infiltration/inflow mitigation work has been documented through 2009. The recent drought in the region has made assessing the overall effectiveness of the program difficult. However, the decline in influent flow at the region's wastewater treatment plants measured since 2002 is at least partly the result of this investment in infiltration/inflow mitigation. With a desire to continue the infiltration /inflow program's progress and with the understanding that investing in local mitigation rather than storage is the region's preferred approach to reducing infiltration/inflow, the Demand Charge Task Force recommends: • The Council implement an ongoing infiltration/inflow reduction program similar to but improved from the existing program rather than a demand charge in 2013. • In cases where a community is not meeting its infiltration/inflow goal(s) or the community has not been implementing an effective I/I reduction program in the determination of the Council or if regulations and/or regulatory permits require the Council to ensure regulatory compliance, the Council may institute a wastewater rate demand charge. • The Council amend the 2030 Water Resources Management Policy Plan to reflect these recommendations. 1 Introduction The Metropolitan Council's inflow /infiltration (I/1) policy contained in the 2030 Water Resources Management Policy Plan (2030 Policy Plan), adopted in 2005, established that the Council will not provide additional capacity to serve excessive I/1 entering the regional sanitary sewer system. Further, starting in 2013 the Council is to implement a wastewater demand charge for communities that continue to require service for excessive I /I. The demand charge would defray the cost of providing attenuation (storage) of excessive I/I to avoid overloading downstream facilities. In August 2009 the Council appointed a Demand Charge Task Force to develop recommendations for the demand charge including its specific features and the 2013 implementation date. While the local mitigation of I/I has been successful in eliminating some of the excessive I /I, some remains in the system and it is expected to be a long -term challenge to achieving the Council's guidelines for allowable I/I. Without additional mitigation, the Council and its ratepayers will face substantial capital expenses for infrastructure to convey and treat the excessive I/I and risk of overflows will continue. Council's Existing I/I Policy and Program Concern about the impacts of I/I on the regional sanitary sewer system led the Council to appoint an I/I task force that met in 2003/2004 to develop recommendations for an I/I reduction program. The I/I Task Force estimated that the cost to store, convey, and treat excess I/I was in the $900 million range while the cost for source removal was in the $150 million range. Risk of system backups and overflows would continue. The I/I Task Force recommended that the Council initiate an I/1 program focused on mitigating excess I/1 versus increasing system capacity. The Council's existing I/I reduction program, based on the Task Force's recommendation and adopted in the Policy Plan, is a surcharge approach to source removal. The Policy Plan states that the Council will not provide additional sanitary sewer system capacity to serve excessive I/1. Communities with excessive I/1 would be required to eliminate the excess I/I within a reasonable time period. The premise of the policy is that short -term peak wet weather flow uses the system's reserve capacity needed for growth. The program's implementation strategies are shown on the right. • I/I izoals for all communities based on the designed peak hour flow capacity of the interceptor(s) serving the community and using the current peak hourly flow factor design standards for interceptors • Communi I/I mitigation programs developed and implemented from 2007 to 2011 • 1/1 surcharge program initiated by Council in conjunction with communities • In 2013, for communities not meeting goals (a) limit future increases in wastewater service until goal(s) are met and (b) institute a wastewater rate demand charge. 4 The I/I surcharge program began January 1, 2007. To date, 46 communities have participated in the surcharge program. A total of $46 million of local I/I mitigation work has been documented through 2009 as part of the program. The region's recent drought has made assessing the overall effectiveness of the program difficult. However, the decline in influent flow at the region's wastewater treatment plants measured since 2002 is at least partly the result of this investment in infiltration/inflow mitigation. Demand Charge Task Force On August 13, 2009 the Council appointed a Demand Charge Task Force to develop recommendations for the demand charge including its specific features and the 2013 implementation date. The Task Force generally met bi- monthly from September 2009 to August 2010. The Task Force reviewed information presented by the Metropolitan Council Environmental Services (MCES) staff, which also provided facilitation and administrative support. The recommendations and conclusions were arrived at by consensus of the Task Force members. The Task Force established goals for the next phase of the Council's I/1 program. The Task Force recognized that several goals conflict and that satisfying all goals was likely not possible. Given that I/I mitigation is a complex issue with numerous aspects that communities and the Council cannot control or foresee the Task Force sought a balanced approach that would foster continued progress as it developed recommendations for the next phase of the program. • Effective in achieving I/I policy goals • Equitable among served communities • Defensible using measured flow data • Fiscally responsible consistent with cost of service and other policies; accounts for regional economics • Reasonable, uniform rules and procedures • Flexible to deal with uncertainties and change • Understandable System Capacity Analysis I/1 mitigation is needed in order to recover or maintain regional sanitary sewer system capacity to provide for growth and to help minimize the potential for wastewater backups in basements, spills from manholes, or overflows from regulators. The 2013 demand charge implementation date was established based on a 2004 analysis of the sanitary sewer system performed for the previous 1/I task force. A new capacity analysis was performed using more recent data and projections. See Appendix A for full details of the capacity analysis. Conclusions from the analysis are summarized in the box on the following page. The current system analysis indicates that capacity is adequate for several years longer than the previous analysis indicated. With the slowdown in regional growth, the current policy's 2013 demand charge implementation date appears less urgent. Interceptor Capacity • A small number of growth- related interceptor capacity improvements are needed and are underway. • Capacity is adequate through 2020 for the remainder of the interceptor system. • If not addressed, excessive I/I will continue to cause interceptor system capacity constraints and risks. Treatment Capacity • Excessive I/I uses reserve capacity at the Blue Lake, Metropolitan, and St. Croix Valley Wastewater Treatment Plants (WWTPs). • During extremely excessive I/I events, flow has been diverted around the biological treatment system to protect the process. Though effluent limits have been met under these conditions, this flow blending poses future regulatory risk. • No WWTP capacity expansions are planned in the immediate future. I/I Program Issues and Recommendations During the course of Task Force meetings, members' comments ranged from the I/I program's nature and goals to specific aspects of program implementation. The following paragraphs summarize members' comments about the overall program. Table 1 summarizes a number of specific implementation issues and recommendations for the next phase of the I/I reduction program. Members' comments about the overall program fell into the following categories: • Program's goal and approach • Program procedures • Appeals Task force members agree with the Council's policy and the I/I program's premise of eliminating excess I/I sources rather than increasing regional sanitary sewer system capacity to handle excess I /I. Members commented that drought, water conservation and I/I mitigation itself can unfairly make a community's goals more difficult to reach under the current program's goal- setting method. Members also discussed how the program would ultimately measure success. Sources of excess I/I may become more difficult to locate and mitigate, I/I mitigation is not well - defined, and the vagaries of weather, such as drought, can complicate measuring the program's effectiveness. Currently, a community satisfies program requirements by expending funds on local mitigation equal to its surcharge. While this may satisfy program requirements, there is no guarantee it achieves the program goal of reducing excess I/I and avoiding future exceedances. 4 Issue Progran Goal Demand charge Table 1 UI Promm Issues and Recommendations The goal of the I/1 program is to minimize the risk of system backups and overflows and to reserve system capacity for growth. A demand charge approach to I/1 mitigation, in which a community with excessive inflow /infiltration would be assessed a charge to defray the cost of the Council's providing attenuation (storage) of excessive I /I, diverts funds from local mitigation and allocates them to building storage. This approach does not address I/I at the source and it has not been shown elsewhere to effectively avoid backups, spills, and overflows. It is not the preferred approach to reducing infiltration/inflow. Allowable I/I The current program establishes I/I goals for each metershed by setting an allowable peak hour flow, based on average flow multiplied by the applicable MCES standard peaking factor. The standard peaking factors account for diurnal fldw variation and an allowable level of I/I. Although based on industry standards, the factors do not directly address the following: • Specific amount of allowable I/I incorporated in the factor. • Type of sewer system (sanitary versus originally combined). • Age of sewer system (design codes that allowed sump pump and foundation drain connections; materials of construction). • Antecedent precipitation and subsequent groundwater level. • Rainfall intensity, duration, volume, and frequency are not considered, due to regulatory compliance issues. Consequently, two problems arise: Recommendations Continue the I/I program with these two goals, with added recognition of case -by -case evaluations of risk based on system capacity analyses and applicable regulatory Implement an ongoing I/I reduction program with characteristics similar to the existing program (i.e., continuing to "rebate" mitigation costs), rather than imposing a general demand charge, beginning in 2013. In any specific case in which a community is not meeting its infiltration/inflow goal(s), and the community has not been implementing an effective I/I reduction program in the determination of the Council or if regulations and/or regulatory permits require the Council to ensure regulatory compliance, the Council may institute a wastewater rate demand charge. Continue to determine exceedances based on peak hour flow using its standard peaking factors to determine peak hour flow limits. Gather, analyze, and share the program's existing information and data to better quantify mitigation effectiveness Evaluate and develop, as appropriate, an improved method for determining allowable I/I that better accounts for items such as: • Age and type of sewer system • Risk of overflow and backups • Historical flow variability and components (base sanitary flow, groundwater infiltration, rainfall - dependent I /I) • System hydraulics, such as available flow attenuation, travel time, and reserve capacity Use the findings of the above to update the program for Goal and Table 1 I/I Program Issues and Recommendations Issue Description Recommendations (1) It is difficult to assess the effectiveness of I/1 mitigation the 2040 Policy Plan. work. (2) Communities may cycle on and off the I/I exceedance list, even after expending significant funds on I/1 mitigation. Program Procedures Base flow The current program uses a 3 -year rolling average daily flow as Use a longer time period (e.g., 10 years) for the base flow to the base flow for determining allowable peak flows. Drought normalize the effects of precipitation (drought and wet can lower a community's 3 -year rolling average which, in turn, periods). lowers the community's allowable peak flow. Water A community's water conservation and I/I mitigation can lower Provide a general adjustment of 1% per year for water conservation, its 3 -year rolling average daily flow. This, in turn, lowers the conservation and I/I mitigation so as not to penalize and 1/1 community's allowable peak flow, effectively penalizing a communities for their work in these areas. Also, allow for a mitigation community for water conservation and 1/I mitigation. greater adjustment if a community can substantiate it with actual data. Growth If a longer time period is used for the base flow in the Adjust the rolling average daily flow for the wastewater calculation of the allowable peak flows, communities that have generated by the growth in the community from the middle of had growth over the longer period will be penalized. the rolling average period to the goal year, thus increasing the base flow to account for the growth that has occurred. I/I into A community should not be accountable for I/I that enters the Where applicable, adjust peak measured flows in a metershed Council Council's interceptors that pass through the community. by subtracting out that portion of the peak estimated to be due interceptors to I/I into Council interceptors in the metershed. Metersheds The lack of multiple meters in some larger communities makes • Continue to determine exceedances on a metershed basis. it difficult to determine where I/I sources are and the . Upon request and where substantial I/I exists, collaborate effectiveness of specific I/I mitigation work. On the other hand, with communities in metering projects to assess I/I multiple meters can cause a community to have an exceedance sources. when, if the flow was consolidated in one meter, no exceedance may have occurred. Mitigation The current program has a 5 -year mitigation period (this is the Implement a 4 -year mitigation period beginning with the period length of the surcharge phase of the program). exceedance's billing year (e.g., the mitigation period for a June 2013 exceedance would begin in January 2014; the mitigation period for a July 2013 exceedance would begin in January 2015. Redu ing the mitigation period from 5 to 4 years Table 1 I/I Program Issues and Recommendations Issue Description Recommendations reflects the fact that communities generally have had time to determine I/I sources and priority areas. In addition, allow a 1- year look -back period from the time of the exceedance; that is, I/I mitigation work performed in the calendar year prior to the exceedance would be eligible (e.g., mitigation expenses incurred in 2013 could help meet the requirements for the June 2013 exceedance; mitigation expenses incurred in 2014 could help meet the requirements of the July 2013 exceedance). The 1 -year look -back period is intended to provide incentive for communities to perform ongoing and proactive I/I mitigation. Appeals Locating I/I What should be done if significant funds are expended in trying Allow a community to appeal to extend or defer the I/I sources to locate specific I/I sources without success? mitigation period for a defined period of time until: • I/1 sources are found (i.e., rain events occur that point to the sources) • The community can develop a reasonable mitigation plan in the absence of specific location information. The appeal must be based on the findings of the community's I/I source en ineering investigation. I/I mitigation The current program assumes I/I mitigation costs $350,000 • Continue the current program's procedure of allowing a cost (escalated each year for inflation) per million gallon per day of community to appeal and reduce the estimated mitigation assumption I/I reduced. While program cost documentation submitted by cost if the actual cost of mitigating the sources can be communities generally supports this value, there may be cases shown to be less than the estimated mitigation cost. where a cost - benefit analysis is warranted. . Allow a community to appeal the estimated mitigation cost if it is more than estimates of the lifecycle cost of storage, conveyance, and treatment of excess I /I. The appeal process would initiate a joint cost analysis between the community and the Council. The cost analysis would be based on appropriate design criteria such as a design storm frequency. If the cost analysis indicates that the estimated cost of mitigation is more than the estimated cost of regional storage, conveyance and treatment, the Council may allow the community to waive its option to Table 1 VI Program Issues and Recommendations Issue Description Recommendations perform the estimated mitigation work and the Council would impose a financial charge on the community to defray the cost of regional storage, conveyance and treatment. Super Storm Should there be some limit on the size of storm event for which Although the Council's permits do not identify a storm or other exceedances will be measured? frequency for which overflows or spills would be allowed, extraordinary include an appeal process that may allow relief if a community circumstances is otherwise making progress toward I/I mitigation and a peak flow event was caused by unusual conditions or extraordinary circumstances. Task force members commented on various technical aspects of the current program. They urged the Council to use the information and data gathered in the current program phase to further develop the program. For example, they questioned whether MCES' standard peaking factors are appropriate in all cases and whether the mitigation costs used to establish surcharge values are valid for all communities. They recommended that these and other technical aspects be reviewed. Finally, task force members discussed program procedures. While members understood the need for the program to have uniform rules and procedures, they encouraged the Council not to take a "one- size - fits -all" approach in a program of this magnitude because such an approach could lead to inequities among communities. They suggested the Council consider ways to incorporate into thr.program processes such as case -by -case analyses, cost effectiveness reviews, and an appeal process for unique situations. Though the Task Force and MCES staff could not address all of the issues raised, the Task Force members' comments provide areas to consider in the next 1 to 5 years as the Council further defines the I/I program and develops the 2040 Policy Plan. After discussing a number of options for the next phase of the I/I program, the Task Force came to the consensus recommendation that the Council implement an ongoing, second phase (herein called "Ongoing Program ") of the inflow and infiltration (1 /I) reduction program beginning in 2013 rather than implement a demand charge at this time. The Task Force recognizes that the Council may need to institute a wastewater rate demand charge for those communities that have not met their I/I goal(s), if the community has not been implementing an effective I/I reduction program in the determination of the Council, or if regulations and /or regulatory permits require MCES action to ensure regulatory compliance. A complete description of the recommended Ongoing Program is contained in Appendix B. The Ongoing Program requirements apply to all communities whether or not they previously were required to implement I/I reduction work. The Ongoing Program will be further defined in a Procedure Manual. 2030 Policy Plan Amendment The Task Force recommends that the Council amend its 2030 Policy Plan as needed to reflect the changes to the I/1 program. The text of the Policy Plan amendment is in Appendix C. A public hearing on the proposed amendment was held on July 13, 2010. Written comments on the amendment are contained in Appendix C also. This report addresses a number of the issues raised during the public hearing process, such as special regulatory circumstances, metering, MCES standard flow peaking factors, I/I mitigation costs, and time to complete I/I mitigation work. These issues will be addressed further in the Ongoing Program Procedures Manual and in the next Policy Plan update. The recommended Ongoing Program is a result of the Council's I/I reduction initiative that began in 2003 with the initial 1/I Task Force and was defined in the 2030 Policy Plan. Figure 1 shows the Ongoing Program schedule in relation to the Council's overall I/I Program and Policy Plan development, implementation, and evaluation. The Task Force recommends that a Figure 1 UI Pro ram Schedule Year `03- `05 `06 `07 `08 `09 `10 `11 `12 `13 `14 `15 Beyond `04 `15 UI Policy I/1 2030 Demand Demand 2040 Task Policy Charge Task Charge Policy Force Plan Force 1 Task Plan Force 2 M Program a. Development Surcharge Ongoing Program Program Development Develop- ment b. Implementation Surcharge Program (recommended Ongoing 1/I Reduction Program extension of mitigation work to '12) c. Evaluation Surcharge Program Evaluation subsequent demand charge task force be convened in approximately 2014 to review and revise, as necessary, the Ongoing Program. The 2040 Policy Plan process will provide an opportunity to make any resulting policy revisions. 2011 and 2012 Surcharges Recognizing the financial stresses associated with the current economic environment, the Task Force considered options to minimize the combined financial impacts of the Council's proposed SAC shift (discussed under the "Ongoing Program Cap" section of Appendix B) and any remaining I/1 surcharge work. In the current surcharge phase of MCES' 1/I program, I/I reduction work for non - capped communities is scheduled to be complete in 2011. An evaluation period, with no 1/I reduction work except for capped communities, is planned for 2012. To lessen financial impacts and to allow 1/I reduction activities to continue into 2012, the Task Force recommends that non - capped communities with I/I reduction work required in 2011 be allowed to defer up to half of the required work to 2012. Because capped communities are already deferring work beyond 2011, this recommendation does not apply to capped communities. However, the annual required 1/1 reduction work for capped communities in 2011 and 2012 will be determined based on 25% of the community's MWC minus the impact of any shift of costs from SAC to the municipal wastewater charge allowed by state statute MS 473.517 subd.3b. Summary Recommendations The Demand Charge Task Force recommends that: • The Council implements the Ongoing I/1 Reduction Program beginning in 2013. • The Council may institute a wastewater rate demand charge for those communities that have not met their I/I goal(s), if the community has not been implementing an effective I/I reduction program in the determination of the Council, or if regulations and/or regulatory permits require MCES action to ensure regulatory compliance. • Non - capped communities with I/I reduction work required in 2011 be allowed to defer up to half of the required work to 2012. • The annual required I/1 reduction work for capped communities in 2011 and 2012 be determined based on 25% of the community's MWC minus any SAC shift. • The Council amends its 2030 Policy Plan as needed to reflect the above recommendations. G