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3. Existing Conditions ' 3.1 Sanitary Sewer ' The sanitary sewer system in the project area consists of 9-inch and 18-inch diameter vitrified clay pipe (VCP) installed in the 1960's. The joint sealing material in use at that time was typically an oakum and bituminous material. No problems have been reported in this area but it is anticipated that the joints will have minor root intrusions and minor offsets due to the age and construction methods. The calculated capacity of the existing 300-foot section of 18-inch pipe, in "new" condition; between the two intersections of 29th Avenue and Wilson ' Street is about 6,000 gpm. The calculated capacity of a new 9-inch line on 291h Avenue is about 450 gpm. The actual capacity of each line will be somewhat less than the calculated capacity due to variations in alignment ' and solids deposition in the pipes. Wastewater flow in the City of St. Anthony is metered by the Metropolitan 1 Council Environmental Services (MCES) at four locations. Meter number 104 is located on the southern boundary of the City at the end of the 18-inch sewer on Wilson Street. This location provides flow records for the project ' area and the majority of the Community. According to MCES records, the wastewater flow in the St. Anthony sanitary sewer system increases significantly during spring runoff conditions and during and after heavy ' rainfall events. Under normal dry weather conditions(January 1997)the flow at meter M-104 averages about 300 gpm. The flow increases during wet conditions (July 1997) to an average of about 770 gpm. On the peak day in ' July 1997, the flow recorded at the MCES metering point reached an average of about 1,400 gpm over the entire day. Instantaneous peaks certainly were higher than the average for the day; however, without ' additional data, it is difficult to reasonably estimate the amount of flow in the system under these short-term conditions. During the high flow period in July 1997, there were numerous reports of sanitary sewer lines backing up into the residents basements along 29th Avenue and Wilson Street. In some cases the sewer backups are a regular occurrence and residents have been investigating methods of installing back- flow protection like a check valve or a gate valve. ' In consideration of the capacity calculations, anticipated peak flow rates and reports of system backups, it can be concluded that the sanitary sewer system in the project area does not have sufficient capacity in its current ' condition to convey the anticipated wastewater flow rates. ' City of St.Anthony A 2000 Street&Utility Improvement Project WSB Feasibility Report WSB Project No. 1065.25 ' Page 4