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B.A.Mittelm 3 <br /> 350 Westwood Lake Office Bret A.W <br /> 8441 Wayzata Boulevard Peter R.Wdlenbnng, P.E. <br /> AWS <br /> AleMinneapolis, MN 55426 Donald W.Sterna,P.E. <br /> . Ronald B.Bray,P.E. <br /> 612-541-4800 <br /> &Alssoctates,Inc. FAX 541-1700 <br /> Memorandum <br /> To: City Council <br /> City of St.Anthony <br /> From: Charles Janski, P.E. 09, <br /> Project Manager <br /> Date: August 30, 1999 <br /> Re: Sanitary Sewer Study <br /> WSB Project No. 1065.16 <br /> The City of St Anthony has two separate but related problems with the existing sanitary sewer <br /> system. Infiltration/ Inflow (UI) generates very high flow rates and the high flows exceed the <br /> . available capacity in the some of the existing sewer lines. <br /> The attached Sanitary Sewer Study is the first step in addressing the Infiltration/Inflow and capacity <br /> problems in the City's Sanitary Sewer System. Preparation of the document required review of <br /> available background information including many historic studies, City construction record <br /> drawings, and Metropolitan Council Environmental Services (MCES) flow records, as well as <br /> discussion with City operating staff and limited site visits. <br /> The flow records were analyzed to quantify the I/I and determine the financial cost to the City. This <br /> analysis suggests that in the two-year period of 1997 and 1998, the City of St Anthony paid <br /> approximately$151,000 to the MCES for the I/I in the system. An aggressive VI reduction program <br /> may remove a portion of this UI and provide measurable savings over a number of years. <br /> The sanitary sewer system was analyzed using a computer model to evaluate the capacity available <br /> in the existing pipe network. The model identified several areas that appear to have insufficient <br /> capacity during extreme UI conditions. Many of these areas correspond to the areas that occasionally <br /> have problems with sewer backups. <br /> The background review and flow analyses suggest that private property connections are the primary <br /> source of the remaining I/I in the system. The type of private property connections in the City of St <br /> Anthony are not easily removed or corrected so it is anticipated that significant flow reduction will <br /> take a number of years. Considering the delay in achieving flow reduction, some short-term <br /> • improvements are suggested to reduce the potential for continued sewer backups. <br /> Infrastructure Engineers Planners <br /> F.•I WPW/M1065.761083099-cncL wpd <br /> EQUAL OPPORTUNITY EMPLOYER <br />