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2011 - 2016 Capital Improvement Program

Project #8003, Mpls/St Paul Interceptor Improvements

Description:

This project provides for the rehabilitation of the core wastewater conveyance facilities in Minneapolis and St. Paul. Ranging in size from 54” to 13’ – 10” in diameter, some of these sewers have been in service for 60 or more years. This core interceptor system conveys more than 200 MGD to the Metropolitan Treatment Plant. It is characterized by large size, high flows and difficult access. Access shafts are as deep as 193 feet, and a few are located in underground caves and in ravines. The facility planning will include a review of the inspection findings, and will recommend alternative means to improve and repair the core interceptor system. A major project was the relocation of the Oak Street Interceptor to accommodate the new Gophers Stadium. That project resulted in separating the existing sanitary sewer from being located inside the storm sewer.

Purpose and Justification:

The project will correct problems with the aged, existing interceptors to assure system integrity and function and to avoid potential very costly emergency repairs to correct failures when they occur. The Oak Street Sewer Replacement project provided the opportunity to construct the sewer segments in conjunction with the new Gopher Stadium work at a lower cost and with less disruption.

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Project Authorization:

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   Projected Cash Flow:

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Impact on O&M Costs:

The project will significantly reduce emergency repair costs over potential costs without the project.

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Current Projects

Project Number & Description o Project #800310, Interceptor 1-MN-300 and 1-MN-320 Improvements - this project provides for color television inspection of the downstream 18,906 feet, or 63 per cent, of the Interceptor 1-MN-300 and the downstream 8500 feet, or 47 per cent, of Interceptor 1-MN-320. Last inspected in 1977, Interceptor 1-MN-300 is 60 to 92 feet deep and was constructed as concrete lined tunnel in 1936 to 1938. The portion of Interceptor 1-MN-320 to be inspected was constructed in 1889, of brick stone and concrete. The inspection and report preparation was completed in 2006. The cost of this inspection work was $78,000. (Location Map). o Project #800330, Oak Street Sewer Replacement - the Metropolitan Council currently owns and operates a 100 year old 96” storm sewer with a 10 year old 26.5”x45” sanitary sewer imbedded in its invert. The sanitary sewer needs to be redirected to the Minneapolis East Interceptor (MEI), a 10 ft. diameter sewer, to allow for the construction of the Central Corridor LRT crossing Oak Street at Washington Avenue. The project improves the system reliability by providing additional capacity for the redevelopment of the area and eliminate a segment of the “pipe in a pipe” construction. The estimated cost of this project is $23,725,500. (Location Map). o Project #800320, 1-SP-255 and 1-SP-214 Interceptor Rehabilitation - this project restored the structural integrity of these deteriorated interceptors. In that the size of the pipes and general location were similar, the two projects were merged together for both design and construction. Both of these facilities have been found to have structural defects. Due to factors such as traffic volumes on Como Avenue, the cost of bypass pumping and the disruption to adjacent businesses/residences the chosen method of rehabilitation was slip lining. The estimated cost of this project is $3,250,000. (Location Map). o Project #800340, Regulator Improvements - the MCES operates nine regulators and one pressure relief facility. This project will evaluate each of the facilities and develop a detailed strategy for physical and operational changes that will be necessary to comply with anticipated new permit requirements. The estimated cost of the planning phase of this project is $150,000. (Location Map). o Project #800390, Blue Lake Plant and Metropolitan Plant Service Area Planning - this project originated from the Interceptor Master Plan which identified a number of interceptor facilities requiring needed improvements to convey peak flows from different service areas. Since the development of that plan in 2002, significant growth has occurred faster than anticipated. A number of the projects need to be accelerated and moved from the Master Planning Level to the Facility Planning Level in a concerted, comprehensive and coordinated approach. The project utilizes a single contract and alternative procurement techniques for multiple projects to allow effective management of concurrent studies to take place with limited impact on Met Council Staffing. The estimated cost of this four year project is $10,000,000 of which $1,439,000 is being funded out of Mpls/St Paul Interceptor Improvements project.