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Inner Strength

Innovative Technology Replaces Failing CMP Tunnel with RCP

By Gaetan Vaillancourt

Afailing 144-in. corrugated metal pipe tunnel in Lewiston, Maine, was replaced with a reinforced concrete pipe (RCP) structure using an innovative installation method. The contractor, Diaz Corp. of Jay, Maine, devised the method to avoid having to excavate the pipe in place under existing and proposed streets, highway ramps and a railway line, sometimes at depths of 45 to 55 feet. Diaz had the choice of either pulling (by winch) or pushing the concrete pipe in place over a distance of 1,048 feet. Either way, there would be no digging involved, and the project could be scheduled and carried out during winter conditions.

First constructed in 1972, the large-diameter metal culvert (tunnel) conveys the flow of Jep- son Brook under highway ramps, railway and local roads. Any sign of failure with this major structure had to be addressed immediately. Piece-meal rehabilitation was not an option.

Diaz contacted Strescon Ltd. of Saint John, New Brunswick, to supply the 108-in.-diameter RCP. Strescon used the dry-cast method for the first time to produce such large-diameter pipe. During the winter months of 2001 and 2002, the 31,500-lb. sections were produced in Strescon’s new plant.

Choosing to push the concrete pipe in place, the contractor fabricated a special cart that was driven into the existing metal pipe. A couple of jacks were used to lift the precast concrete pipe off the ground while the cart was pushed along the existing tunnel with a Bobcat loader. In most cases, the cart had to maneuver through six to eight inches of running water inside the pipe. As a section of pipe was moved into position, the jacks were lowered and the pipe homed with the previously positioned pipe using two 6-ton come-alongs anchored in two holes that were lat- er used for pumping grout between the old metal and new concrete pipe. The process was repeated for each unit of pipe by pulling the cart out of the tunnel and loading it with another concrete pipe. No special reinforcement of the bells of the pipe was necessary since the pipe was homed using come-alongs.

With an overwhelming need for the rehabili- tation and upgrade of infrastructure in North America, more innovative approaches to installing reinforced concrete pipe are in demand. Although most rehabilitation projects involve routine construction practices, periodi- cally the contractor, owner and consulting engineer will be challenged to come up with innovative technologies. In this case, a solu- tion was found to a problem that would have cost a great deal more to correct if the conven- tional open-cut method had been used. As this project demonstrates, the versatility of rein- forced concrete pipe can contribute signifi- cantly to improving our underground infrastructure and providing drainage systems that will endure for generations. —Gaetan Vaillancourt is Pipe Division Manag- er with Strescon Limited, Saint John, New Brunswick, 506-633-8877; this report was initially prepared for American Concrete Pipe Association