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, , - Memorandum March 14,2005 Page 2 . The trunk sewer network in the city generally divides the city in thirds. The northern third of the city is collected and discharged at Gateway Blvd and 1-35W via 21" pipe. The eastem third of the city is discharged by forcemain along Hamline Avenue out of Lift Station #8. The western third ofthe city is discharged at Prior Avenue via 21" pipe. Forcemains are pressure pipes between a lift station and a gravity flow pipe located higher than the station. Forcemains are usually made of steel, iron or plastic. Pipe materials for gravity pipes are typically Vitrified Clay Pipe VCP (oldest), Reinforced Concrete Pipe RCP (larger diameters, current) and Plastic PVC (current) Ductile Iron Pipe (current). Sanitary Sewer appurtenances include manholes and drop manholes (drop manholes have pipes entering/leaving more than 12" vertically apart from each other). Lift stations include a variety of equipment and piping for operation and monitoring primarily consisting of2-3 pumps, control panel, valves, sump wetwell and lifting mechanisms. City crews clean all of the sanitary sewer pipes in the city by jetting high pressure water through them. This routine operation may also highlight problematic issues with the system. Infrastructure Comoonents Organized bv Critical Irnoortance to Svstem Operation 1. Lift Stations #8, #5, #2 2. All other Lift Stalions 3. Force mains out of lift stations 4. Trunk Sewer 12" - 21" (RCP) (33,660 ft) 5. Collector Sewer 8"-10" (VCP-most vulnerable) (136,350 ft) 6. Collector Sewers 8" -1 O"(PVC-least vulnerable) (7,100 ft) . Infrastructure Assessment Methods The City's sanitary sewer system conditions are assessed through the following: . Daily inspection/observations of lift station operations . Inspection of manholes . Remote controlled televising of sewer pipe . Records of repairs by city crews . Routine cleaning (jetting) of pipes (may indicate sag in pipe, blockage or collapse) Repair and Rehabilitation Techniques Sanitary Sewer infrastructure repair and rehabilitation techniques include the following: . Lift Stations: Rebuilding of pumps, valve replacement, total slation rehabilitation . Forcemains: Cured in place pipe liners (CIPP), replacement, spot repairs(dig up) . Sewer Pipe: CIPP lining, replacement, spot repairs (dig up), spot repairs (C1PP),joint sealing . Manholes: centrifugal lining, invert reconstruction, joint sealing, grouting, reconstruction Recent Caoitallmprovements . Replacement of the pumps and controls in Lift Stations #8, #5, #2 . Full conversion from can-type station to submersible pump lift station - LS #3, #6, #7 . Current CIP includes conversion of the remaining 6 lift stations to submersible pumps . Systematically televised all sewer pipe south of 1-694 as well as well as selected areas north of 1- 694. . Installed CIPP liners in 4,000 feet oflrunk sewer . Installed CIPP liners in 6,000 feel of collector sewer . Joint sealed 4,600 feet of trunk sewer . Joint sealed 10,300 feet of collector sewer .