Caulks Creek Force Main Condition Assessment and Rehabilitation

Client: Pure Technologies
Owner: Metropolitan St. Louis Sewer District
Year: 2020

The Caulks A Pump Station was constructed in 1986 to eliminate multiple package plants. The 20- and 24-inch ductile iron force main was eventually extended to the Creve Coeur Pump Station, removing the last of the package plants. A 36-inch force main was constructed in 2011 to create redundancy in case of failure. The condition assessment and rehabilitation project was completed to extend the life of the existing force main to ensure redundancy.

M3, as a subconsultant to Pure Technologies, helped to perform assessment on 30 medium to high priority force mains (including Spirit 2 Force Main) throughout St. Louis as part of MSD’s Consent Decree with EPA. The project’s goal was to identify and address locations along the force mains that have a high potential for failure due to corrosion and fatigue. Several non-destructive testing techniques were employed to evaluate the force mains, including sending a SmartBall® through the mains to record sonic variations that indicate air pockets.

M3 mounted monitors at the pump stations to record pressure data and performed hydraulic analysis to confirm locations where force mains flow under gravity conditions. M3 also designed combination air valves at several locations. Force main rehabilitation was recommended for locations that have a high probability of failure.

M3 designed pressure pipe rehabilitation for 30,000 feet of existing 20” and 24” ductile iron force main that has suffered numerous failures in recent years. Several alternatives were considered, including Cured in Place Pipe (CIPP), pulled HDPE liner, fusible PVC liner, pipe bursting and open cut. An EPA-SWMM hydraulic model was prepared to study the effects of the reduced pipe diameters on the existing pump station. There are numerous horizontal and vertical bends in the pipeline that affect the allowable length of rehabilitation before access pits are required. Obstructions to access pits included dense residential backyards, a mobile home park, levees along the Missouri River and railroad tracks. The project included the preparation of a Technical Memorandum that compared the rehabilitation methods and their construction costs. Construction Drawings and Specifications were prepared after MSD chose the preferred alternative, CIPP.

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