Rebuilding the air/ground transition of a 12" carrier pipe through a concrete wing wall required careful orchestration to complete
Suspended Pipelines - Air to Ground Transition
Midwestern Contractors (MWC) has a great deal of experience working on suspended pipelines. These pipelines present unique maintenance challenges. They are exposed to greater temperature extremes, and movement compared to buried pipelines. Corrosion is compounded in the winter when road salt spray falls on the pipe and hangers. The hangars and bridge structures are subject to the same corrosive conditions as the pipe. The maintenance work is not limited to the pipe but rather the entire system that supports the pipe.
At some point the pipeline transitions from suspended to buried. This can be accomplished with the use of the risers or through wing walls attached to bridge abutments. The latter can be problematic over prolonged periods of time. Risers provide a way to rapidly change the elevation of the pipeline. However, when the Right-of-Way depth is restricted, the pipe must follow a shallow line of lay as it exits the suspended portion. This requires penetration of the wing walls.
Typically, the pipe would be cased through the wall. But if a casing is not used the pipe would be coated and wrapped like the wraps used on air/ground interfaces. In this project MWC replaced all the hanger hardware several years ago. See 130th Street Bridge. At that time, the corrosion was treated, and the pipe and new hangers were coated. Now the pipe penetration through the wing walls had to be inspected, treated, and cased, to ensure the integrity of the pipe, and allow future access.
Scope of work
Remove wing walls, reinforce and rebuild walls. Strip and sand blast 12" carrier pipe, recoat, install link spacers, ring seals and case the pipe through the wing walls. Restore all disturbed areas.
Finding and marking foreign utilities was an important first step in laying out the work. Fiber optic cables and electrical lines were near the pipeline. These utilities were located, exposed, and secured. To create sufficient workspace one lane of traffic was closed. The lane was closed with a long taper to promote easier traffic merging. A controlled opening was left for construction vehicles to enter and exit. The slope towards the river was too steep to allow work on the pipeline. Scaffolding was erected to provide a safe and level workspace.
Mechanical and hand excavation was used to expose the pipe. The excavation created sufficient work area to allow for the attachment of guide rails for a circular concrete saw. This saw made clean cuts through the concrete and reinforcing rods. With the bulk of the concrete removed the remainder was chipped away with pneumatic tools. At this point, the pipe was sand blasted and then epoxy coated. Spacers and link seals were then installed, and a length of sleeve material was fabricated to provide additional protection through the wing wall.
Holes were drilled into the sides of the remaining wing wall. These holes formed the anchor points for reinforcing rods. The reinforcing rods were bent and tied into the shape of the internal supports for the new wing wall. The form was cut to seal around the casing. The carrier pipe was flanged on both sides of the wing wall. If corrosion develops in the future the carrier pipe can then be unbolted, cut, and removed from the casing. Allowing for a new piece to be installed. This operation was completed on each side of the bridge. With the reinforcing rod and form in place concrete was poured and finished.
The result was a pipeline penetration that could be maintained in the future. The surrounding disturbed areas were restored and reseeded.
There were no safety incidents on this project. The hazards included traffic driving into the work zone, falls, slips, and trips, rigging, and lifting. These hazards were mitigated by planning the work and designing structures to remove the risks, like scaffolding and traffic control.
Midwestern Contractors has built and maintained pipelines, stations, and related infrastructure since 1951. Our work includes piping modifications, Integrity projects, line lowering and relocations, cut outs, complete station modifications including bi-directional, small volume provers. As well as meter and regulation work. If you wish to speak with one of our Project Managers, or you have bid documents and desire a quote please click on Request a Project or call Mike Purpura at 630-936-3282.