Entergy New Orleans (Louisiana, U.S.) has retained InfraSource Inc. (Media, Pennsylvania, U.S.) to take down the double-circuit 1431 kcmil conductor spanning the Mississippi River. This river crossing was the last remaining overhead transmission line crossing between the city of New Orleans and the Mississippi Gulf Coast.

Cruise ships were getting taller and wider, shipping vessels were increasing in size and the military's needs had increased to the point where action was needed. Entergy had already installed and energized the replacement underground circuit, but the conductor still had to come down.

Mark Maslonka, InfraSource project manager, describes the challenges of removing this conductor. “The river traffic was so heavy that the Coast Guard had to restrict all travel for eight hours a day, for two days a week, for three weeks. The Coast Guard was really good to work with. We were able to take down one conductor a day, which is a good day's work.”

The river-crossing span of 3021 ft (921 m) was held up by 400-ft (122-m)-high river-crossing towers attached to 100-ft (30-m)-high strain towers located 350 ft (107 m) away. InfraSource worked off both towers and helicopter platforms. A total of six conductors and two static wires were taken down.

The project took four weeks from start to finish, including one week to mobilize and perform trial runs. States Maslonka, “Trav Thieffe, the project manager from Entergy, provided all the support we needed to get the job done. He was great to work with and handled all the go-between work that is essential in a job like this.”

The actual removal of the conductor progressed as follows. First the insulator spacers were removed. Then the de-energized conductor was removed using a ¾-inch (19-mm) steel wire. Then the steel wire was removed using a ⅞-inch (22-mm) Uniline rope, followed by a ⅝-inch (15.8-mm) Uniline rope, followed by a ½-inch synthetic rope. The synthetic rope was then removed by helicopter.

Once the conductor was down, InfraSource crews removed the strain towers and guys. The main river-crossing towers were not taken down, and it looks likely that at least one tower might be converted for use as a communications tower.