09-27-2006 Council Agenda - Laserfiche WebLink

Home Browse Search

515 Little Canada Road, Little Canada, MN 55117-1600 (651) 766 -4029 / FAX: (651) 766 -4048 www. ci.little -c anada. mn. us MAYOR Bill Blesener COUNCIL Jim IaValle Rick Montour Barbara Allan John Keis ADMINISTRATOR Joel R. Hanson MEMORANDUM To: Mayor Blesener & Members of City Council From: Bill Dircks, Public Works Superintendent Date: September 20, 2006 Re: Inflow and Infiltration in Sanitary Sewer Laterals The City received a monthly flow comparison chart of sewer flows into the Metropolitan Council system. It has been included for your reference. The chart shows a significant drop in flows over the last year or so. The question is whether this is a positive trend or an anomaly due to the dry year we have had. Early indications lead us to believe that the reduced flows are in large part due to the dry weather. Staff also believes that the manhole cover replacement project has aided the cause along with the replacement of the sanitary sewer main along County Road D from Payne Ave. to Edgerton St. and some stretches on Carla Lane. So while the reduced flows are encouraging, staff still believes there is some work to do regarding inflow and infiltration. In the search for inflow and infiltration a contractor has televised a selection of sanitary sewer service laterals running from the main to individual houses in areas deemed to be susceptible to infiltration. Those areas televised initially were Carla Lane and County Rd. B2 east of Edgerton St. We discovered major Leaks in two services we televised. The estimate given by the television contractor was roughly 10 -20 gallons per minute of clear water leaking into the service. That is a significant number when calculated over a year's time. The common cause of lateral leaks is failure of the joint between the stub installed by the City's contractor and the pipe from the house run by a different contractor at a later date In years past, the joint was formed using concrete or blackjack. Both are highly susceptible to erosion and corrosion between acidic soils and sewer water passing over them. Cracks are also very possible in old clay pipe. Staff would like to repair the leaking services and would like direction on how these repairs should be funded. The options would be to assess the homeowner for the work, assess half to the homeowner and have the City pay half, or the City could pay for the repair. In the long -term perspective of our sanitary sewer flows, it is in the City's best interest to fix the leaks. This would lead to reduced flows to Metropolitan Council