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HomeMy WebLinkAbout05-29-07 Item 7C, Infiltraton and Inflow Study ~ ~HlLLS Request for Council Action Prepared By: Kristine Gi.9a Dept.: Engineering Council Mtg. Date: --..............u--.Si29ifi7 Final Action Needed By: ..Si2~W{.__ ~)ty Agenda Item: 7C "."."....."."..."."~------ "Sudgete-(fAm"o"lJiiE _____.._.......... _______ _ ..... ...ltQ.Q~_1.Q.Q. Actual Amount: $9.600' Funding Source: m.._... .".""."_~~_~}f~fi.~~~~i:gi!~~f.Rd~~~~~~~~- mi!~}~ll~m];$;~qiliUm!Hif~~I~_.m.'...."..,."."."_______________......".".".....__._____________..................".._"_____________......."..."......."_..__________m_.._m."."."......."."________nm..m................._..____n____m..._....."...."."..._"_"____________.._"_.....,,...."..__"______________mm......."""_._._"__n_______........ iMotion to Approve a Proposal dated May 7, 2007 and Authorize Staff to Contract with Bonestroo to complete an Infiltration and Inflow (III)! !Study for the City in an amount not to exceed $9,600. . -------.-........----- ------..-........"--------..-.-........------- ---.-.........--------- -.-..........-------- -............---- --.--............"------- ~maffil~~mtlJ'meijFf~IL&:~h:yj~~~tsJliiL__,...,..,.".,....."__________.__,_.,..,."..,.,..._,___________.,___.,..,.,.."......_._____________.,..,.,..,."..,..,_"_"_________.___.,..,..,..,..,....._.____________,..,_,...".,.,._..._.____________.,..,.,..,..,._,._,.__________.,_____,..,..,..'.'..'.____________..,..,..,...._'_"__m_______......".".. iApprove a Proposal dated May 7, 2007 and Authorize Staff to Contract with Bonestroo to complete an Infiltration and Inflow (III) Study for thei iCity in an amount not to exceed $9,600. ' x From Civil Engineer Kristine Giga and Public Works Director Greg Hoag dated May 23, 2007 No.: "o,~No.: Recommendation: Recommendation: IOther: ~~H~IlQlal;ffOl!~IJ~:UQOslt1f~lhiJ1fJFzr;.0\mN?JJmjt___ "______ ___ ......._________. ."______ ._.._"_ _________ _ ' * $100,100 has been included in the 2007 budget for work relating to III. The labor costs in the proposal are $9,600. Please refer to the attached memorandum for additional direct expenses as a part of the III study. ~ ~ EN HILLS MEMORANDUM DATE: May 23, 2007 AGENDA ITEM 7.C TO: Mayor and City Council Michelle Wolfe, City Administrator Kristine Giga, Civil Engineer ~ Greg Hoag, Public Works Directo~ FROM: SUBJECT: Approve a Proposal dated May 7, 2007 and Authorize Staff to Contract with Bonestroo for an Infiltration and Inflow (III) Study for the City iu an amount not to exceed $9,600 BACKGROUND As part of a joint solicitation with the City ofRoseville, City of Arden Hills staff has requested proposals from 5 consulting engineering firms to assist us in identifying Infiltration and Inflow (III) sources within the City of Arden Hills. Prior to bringing these proposals to the Council for consideration, we wanted to provide a brief background on why III is a concern for the City of Arden Hills. The majority of Arden Hills' sanitary sewer system was constructed in the 1950's and 1960's, along with much of the current housing stock. The City's sanitary sewer system includes more than 42 miles of sewer piping and 14 lift stations. Wastewater treatment for the City is provided by the Metropolitan Council Environmental Services (MCES) at the Metro (Pig's Eye) Plant located in St Paul. The City of Arden Hills is billed by the MCES for the use of the interceptor sewer system and treatment of the wastewater at the Metro Plant. The City's wastewater flow is determined by the MCES through three separate meters. What is III?: Infiltration and inflow (III) is defined as clear water flow that would not require treatment had it not been mixed with wastewater. This water may enter the system through manhole covers or manhole wall joints, fractured pipe or other pipe deficiencies, or rain leaders from roofs of buildings that may be connected incorrectly to the sanitary sewer system. Once clear water enters the sanitary sewer system and becomes mixed with wastewater, it must be treated prior to discharge to a \\R VNAS 1 \AHdata$\PR&PW\Engineering\2007\Council_ Actions\5~29M07Memol&I.doc 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. 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: 1&1 5/24/2007 Page 4 Task 1: Data Gatherine: & Evaluation: Review Mapsl Datal MCES Flow Records Collection and review of existing City & MCES sanitary sewer data; including water consumption records, sanitary sewer maps, storm sewer maps, lift station pump details, pump run time records, sanitary sewer televising reports, City maintenance and reconstruction records, records of system backups, and any additional background data. Task 2: Develop Meterine: Proe:ram to Isolate Flows The Arden Hills sanitary sewer system includes more than 42 miles of pipe. With a system of this size, it is important to subdivide the task into smaller pieces to isolate the system into manageable areas for study. The majority of the system will be divided into sub-districts at the consultant's determination, and flow meters will be installed to monitor flows. Task 3: Source Identification Effort Through the metering effort, the consultant will identify possible sources of the system VI and attempt to isolate the sources to some of the subdistricts of the system. The method of source identification will depend on the anticipated sources of the VI. One or more of the following source identification methods may be used in any or all of the sanitary sewer sub-districts: . Smoke testing (If needed, includes additional cost to paid for directly by the City) . Physical inspection of manholes (To be performed by City staff with consultant direction) . Internal television inspection (If needed, includes additional cost to be paid for directly by the City) . Sump pump inspection program (If this is identified as a source of VI, staff will evaluate how to proceed, with consultant direction) Task 4: Report Preparation The consultant shall prepare a report to formally present the findings of the work in a format that can be presented to the City Council. It is anticipated that City staff will present the findings to the City Council. The report will present a summary of the data gathered, VI sources and problem areas identified based on the work completed, conclusions concerning the potential for effective rehabilitation of possible VI sources, and recommendations for the next phases of the VI reduction effort. There are many rehabilitation procedures and methods available to address identified defects. The appropriate procedure is determined by considering the type of defect, its location and access, and the cost and benefits of rehabilitation. Identified defects will be prioritized. FINANCIAL IMPLICATIONS This is specialized work; therefore, we solicited five consulting companies to provide us proposals to complete the study. We received four proposals for this work, from Bonestroo, Bolton & Menk, Inc., SEH, Inc., and WSB & Associates. Amounts proposed are below: Arden Hills Roseville Bonestroo $9,600 $ I 6,500 Bolton & Menk $20,118 $30,624 SEH $55,304 $75,940 WSB $18,116 $20,923 1&1 5/24/2007 Page 5 After reviewing their proposals, staff recommends that we engage Bonestroo to complete this work at a labor cost not to exceed $9,600. Due to the nature of the investigation, there will be additional equipment costs for this work. Without understanding the full extent of the VI issue in Arden Hills, it is difficult to assign a "not to exceed cost" for this additional investigation. As a result, staff wrote the proposal with these being direct costs. These costs are: . Flow meter rental: The consultant will need to break the City down into individual sewersheds to monitor flows. The length of time these meters will be in place is weather dependent. The meters need to monitor "normal flow" and "high flow". High flow occurs when we receive significant rain events. We anticipate that the meter rental will be for about one month, with an estimated cost of$2,100. However, if we have a drier than normal summer, this cost will be more due to extension of the monitoring period. . Smoke Testing: Once the consultant has identified the individual sewersheds with III, they need to complete additional testing to determine if the VI is the result ofInfiltration (ground water) or Inflow (sump pump or storm sewer connections). Smoke testing is one way that this can be accomplished. This is the most efficient and cost effective way to locate and identify the number of rain leaders from buildings that are connected to the sanitary sewer. Smoke testing involves forcing smoke-filled air through the sewer line. The smoke will fill the main line plus any connections following the path of the leak to the ground surface revealing the location and source of the problem. Smoke testing costs $185/ hour for 700 feet per hour. This cost will depend on the size of the sewershed identified for further III investigation. All costs for this study will be paid for using sanitary sewer funds budgeted for inflow and infiltration reduction; $100,100 was included in the 2007 budget for these purposes. The findings will be brought to the City Council once the study is complete for consideration of the next steps. RECOMMENDED COUNCIL ACTION Motion to Approve a Proposal dated May 7,2007 and Authorize Staff to Contract with Bonestroo to complete an Infiltration and Inflow (III) Study for the City in an amount not to exceed $9,600.