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. . . , Memorandum March 14,2005 Page 3 Philosophy of System Maintenance and Capital Improvements Our general philosophy has been to ensure that the high priority infrastructure is inspected and improved as necessary. Sanitary sewer improvements can be generally classified as either operationally based or efficiency based. Operational improvements ensure the system operates and limits potential exposure to the city (claims due to baekups in basements, environmental damage etc.). Efficiency based improvements arc implemented to rednee or eliminate infiltration (reduce MCES costs) or reduce operational costs (lift station maintenance manpower, electricity etc.). Often improvements benefit both ofthose classifications however the primary driver has been to ensnre the system is operating safely and with the least amount of failure risk. As is true with most systems, the highest potential for system failure lies within the "moving parts" - in this ease the lift stations. If a lift station fails, the system upstream of the station is at risk for backing np into homes (these can be very large areas). Depending on the failure at a lift station, the remedy may involve parts that arc not readily availahle or the need to truck sewage temporarily out of the station both of which are potentially expensive. Failnres in pipe generally do not have the same amount of potential risk associated with them and the initial remedy is generally an inexpensive spot repair to the pipe performed by City crews. Current available technology allows cities to install structural liners in existing sanitary sewer pipe without any excavation and virtually no interruption to residential use of the system. Beeause of this technology the decision to improve existing pipe can be made somewhat independent of street reconstruction activities. In general, the work eompleted over the past six years has concentrated on the improvement of the city's lift stations and trunk sewer to reduce the city's exposure from system failure. The pipe lining and joint sealing performed to date has been concentrated on the areas with the highest observed infiltration (via televising) into the system which also are some of the oldest pipes in the city. During this time we have made improvements to approximately 25,000 ft of trunk and collector sewer (approximately 14% of the system) to reduee or eliminate infiltration into the system. Based upon the analysis by Dan Beckman and Jeremy Anderson presented to the council earlier this year, the retum on investment for the efficiency improvements to the City is less than 10 years. Water Distribution System System Overview The city purchases potable water from Roseville (purchased from St. Paul) which enters the city at three metered locations (2 -12" mains, one 16" main). These large diameter mains form a "skeleton" throughout the city which feed the two water towers and connect to each other at various points to provide interlocking loops. Emergency connections to New Brighton and Shoreview exist and can be opened to assist those communities in time of crisis or vice versa. Watermains are always full and under pressure. Pipe materials arc typically Ductile Iron Pipe (DIP) (current), Cast Iron Pipe (C1P) (oldest) or high strength Plastic HDPE (current). Watermain appurtenances include valves, hydrants and bends (all DIP materials). Infrastructure Components Organized bv Critical Importance to Svstem ODeration I. South Water Tower 2. North Water Tower 3. Booster Station 4. Trunk pipe (12" - 16") 5. Hydrants 6. Valves 7. Distribution pipe (6" - 10" CIP - most vulnerable) 8. Distribution pipe (6"-10" DIP, HOPE -least vulnerable)