SITUATION
The scope was to repair and rehabilitate using CIPP; a leaking triple-barreled 48-inch diameter, 308-foot long siphon, remove a cleaning nozzle stuck in the 84-inch diameter combined sewer interceptor immediately downstream of the siphon, and then rehabilitate with CIPP that 130-foot long section of that 84-inch pipe.
CHALLENGE
The most significant challenge faced was designing and constructing a bypass pumping system to handle the normal flow of 50 MGD and peak flow of 130 MGD, which involved to major hurdles: 1) as a tributary to the Mississippi River, the Wolf River’s susceptibility to flooding eliminated the shortest distance option of piping the bypass across the river; and 2) during the Christmas holidays in 2015 the Mississippi River reached critical flood stage, forcing an emergency response by SAK to secure the project site.
SOLVED
SAK assigned a Project Manager (PM) with extensive hydraulics and bypass pumping experience to deliver this project. SAK and the bypass pumping subcontract partner developed an alternate approach to bypass the interceptor’s flow from the outset safely. SAK’s PM successfully coordinated with the City of Memphis and the Tennessee DOT to secure permitting for a traffic control plan on a nearby bridge, to run six 4,500 foot long, 24” bypass pipelines (27,000 feet of pipe in total) across the bridge over the Wolf River and I-40, containing and conveying the 50 MGD of flow to an access manhole structure on the 84-inch combined interceptor downstream of the 130-foot section on which SAK would be working and installing CIPP. SAK also secured permitting from the U.S. Army Corps of Engineers and an Aquatic Resource Alteration Permit required by the project’s proximity to the waterways and wetlands. During the Christmas holidays, the Mississippi River reached a critical flood stage, and as a tributary to it, the Wolf River was swollen by the floodwaters. Our personnel’s safety required halting rehabilitation work activities, and the focus shifted to securing the project site. The bypass pumping system was shut off, and in less than 48 hours, our team removed twelve 18” pumps from the job site using two 60 ton cranes and simultaneously secured the discharge bypass piping and manifolds to keep them from becoming buoyant and floating off. The bypass operation was reset when the floodwaters receded. SAK resumed construction activities and completed the successful CIPP pipeline rehabilitation on the 84-inch segment of the interceptor downstream of the siphon. It had been revealed during the pipeline cleaning and inspection of the triple 48-inch barrel siphon that two of the three siphon barrels had experienced failures at some point, which were sources of the leaking the client had intended to repair before the CIPP rehabilitation of the siphon. Learning of the multiple failures in the 65-year-old siphon, the City of Memphis elected to forego the CIPP rehabilitation, abandon all three barrels, and under a separate on-call contract the City had in place, utilized directional drilling technology to install three new 48-inch siphon barrels. This completed the successful repair and rehabilitation of the Wolf River at McLean Siphon Repair safely and on time.
