02-25-1998 Council Agenda - Laserfiche WebLink

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Mayor & City Council February 20, 1998 Page 2 of 4 As part of this I/I study, I would like to implement a sump pump inspection program. In 1993, the Metropolitan Waste Control Commission, now known as Metropolitan Council Environmental Services, did a metro area infiltration/inflow study. Their study identified Little Canada as a City with high groundwater I /I. At that time, it was estimated that 30% of the 385,000,000 gallons going to the Met Council was groundwater infiltration. (Please see accompanying graphs.) This same study also estimated rainfall dependent I/I at 5 %. Ground water infiltration is ground water that enters a collection system through such sources as cracked pipes, leaky joints and deteriorated manholes during dry weather periods. Rain fall dependent I/I includes infiltration from sources that are influenced by temporarily elevated ground water levels during and after rainfall events and inflow which is storm water run -off or snow melt that flows into direct connections to the collection system from sources such as connected rain leaders, area drains, holes in manhole covers, cross connections from storm sewers and connected catch basins. Sump pumps that are improperly connected to the sanitary sewer system could fall under either ground water infiltration or rainfall dependent infiltration depending on when they are running. The base sanitary sewer flow is simply arrived at by looking at the amount of water that was metered into the system and making the assumption that all the metered water eventually makes its way into the sanitary sewer system, typically using December, January, and February as base flow months to eliminate water usage such as for lawn watering. As you can see, it appears we can remove a lot of clear water from the system. I believe one of the most cost effective ways to reduce clear water entering our sanitary sewer system is to implement a sump pump inspection program whereby we would inspect every property that is connected to the municipal sanitary sewer system. Enclosed for your information is a proposed sump pump inspection program timeline, a request for proposals for private property sump pump inspections, a proposed ordinance update to our Section 205.080., a copy of our existing ordinance, copies of an inspection form and compliance certificate, and an information packet that would be mailed to all properties that are connected to the sanitary sewer system prior to beginning the inspection program. I have also included a nine- city survey taken by the City of Plymouth that summarizes other selected cities' sump pump inspection programs I anticipate inspection quotes to fall within the range of $15 to $25 per property ($33,500- $56,000 for all connections). Printing and mailing costs should be approximately $2,000. Based on other communities reduction in flows after implementing a sump pump inspection program, I believe the payback period for this proposed program is less than two years. The following items should also be given consideration: Page 81