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Item No: 8C Meeting Date: April 10, 2017 Type of Business: Council Business Administrator Review: ____ City of Mounds View Staff Report To: Honorable Mayor and City Council From: Brian L. Erickson, Public Works Director/City Engineer Michael L. Richie, Public Works Project Coordinator Item Title/Subject: Resolution 8740, Approving Bidding Documents and Authorizing Advertisement for Bids for 2017 Sewer Rehabilitation Project Background/Discussion: The municipal sanitary sewer system is composed of approximately 45 miles of trunk sewer, 900 manholes, and 2 lift stations. The sanitary trunk sewer was largely constructed in the 1960’s and early 1970’s using (predominately) clay pipe. The use of clay pipe during this time was the industry standard, but more watertight pipe products (PVC) have been developed and replaced clay pipe to become the new industry standard the last few decades. Unfortunately, the leaky clay pipe incurs unnecessary Met Council treatment costs due to infiltration of ground water into the trunk sewer. In general, one gallon per minute of ground water entering the system equates to $1,000 of Met Council treatment costs annually. Public Works has an inspection and maintenance program for the municipal sanitary sewer system. This program includes inspecting the trunk sewer by televising and evaluating the condition of the pipe. Defects are logged while performing inspections, including cracks in the pipe and leaking joints. Repair and remediation of these deficiencies are incorporated into the street and utility improvement projects as much as possible. However, there are trunk sewers not located in these project areas, and conditions of trunk sewers in project areas can change over time. A priority list that ranks the segments of pipe needing repair or remediation is maintained by Public Works. A map of the 2017 sanitary sewer rehabilitation priorities is attached. The municipal storm sewer system is composed of approximately 30 miles of trunk sewer, 1,500 storm drains/manholes, 300 infiltration basins, and 10 regional ponds. The storm trunk sewer was largely constructed in the 1960’s and early 1970’s using (predominately) reinforced concrete pipe. The Public Works Department inspects the storm sewer by televising on an as-needed basis when problems (i.e. excessive settlement of a manhole structure) are observed. Over the past several months, the manhole structure on Edgewood Drive, in front of City Hall, has been observed to have excessive settlement. On March 15, 2017, Public Works Staff televised the storm sewer pipes leading into this manhole structure and observed that the rubber gaskets between the sections of pipe were missing, leading to excessive sand infiltration into the storm sewer in this area. The area of storm sewer to be rehabilitated is shown on the attached Figure. Cured-In-Place Pipe (CIPP) is a trenchless rehabilitation method used to fix pipes that are in good condition, but have leaky joints, without the need to dig up the streets, and replace the pipe. CIPP is a jointless, seamless, “pipe-within-a-pipe” that essentially places a hard liner inside the existing pipe. CIPP lining is considerably less expensive than trenching and replacing pipe, and there is no “inconvenience cost” compared to trenching methods. This is the method that will be used to rehabilitate the sanitary and storm sewers. The Engineering Division of Public Works has prepared plans and specifications (bid documents) in house for use in obtaining public bids for the sanitary and storm sewer rehabilitation project. A