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

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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.