Agenda Packets - 2009/03/23 (2) - Laserfiche WebLink

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April 13, 2009 Item No. 7I Page 2 Discussion: Sanitary Sewer Repairs in the 2009-2010 Street and Utility Improvement Project The 2009-2010 Street and Utility Improvement Project includes a number of repairs to the existing sanitary sewer system. Included in these are three methods of non-intrusive repairs: - Chemical sealing of individual joints between pipes - Installation of short (5 to 10 feet long) liners in the pipe - Lining an entire segment of pipe from manhole to manhole The merits of each of these methods of repair were discussed in the original Feasibility Report for the 2007-2008 Street and Utility Improvement Project. The spot repairs are intended to address individual cracked pipe or leaking joints. They are not intended as a method for root control within the sewer mains. The lining of an entire segment of pipe from manhole to manhole, referred to as “slip lining”, is effective for cracked pipe, leaking joints, and root control. The liner essentially creates a new, seamless pipe inside the existing pipe. There are no joints in the liner, and therefore the liner is virtually unsusceptible to infiltration (leaking joints) and root intrusion. The non-intrusive sewer repairs included in the 2009-2010 Street and Utility Improvement Project were identified on the basis of cracked pipes or infiltration – not on root control. Therefore the majority of the non-intrusive repairs included in the project were spot repairs. Slip lining was proposed for only one segment of sanitary sewer that had several leaking joints, making it more cost effective to line the entire segment rather than install several short liners. Current Root Control Program Mounds View has been experiencing a wide spread maintenance issue of roots in the sanitary sewer. This is common for the type of sanitary sewer that exists in the City, due to the joint system of the older style of pipes. The current maintenance approach has been to treat the roots by chemical application. While effective, this is a short-term approach and is not a permanent solution for the problem. After treatment, the roots typically grow back in approximately 1 to 2 years, and the line requires treatment again. The treatment for roots results in a real expense to the City. The annual budget has typically included $15,000 to $20,000 for root control ($15,000 for 2009). The cycle for performing root control over the entire City is approximately 6 to 8 years. Looking at this from an overall perspective, through the course of one complete cycle of the current root control program, the City spends from $90,000 to $160,000, without making any real progress on the issue.