September 3, 2004
Phone: (504) 865-5714
Paul Zimmermann wasn't sure it would work until the switch was finally flipped, but when it was, he knew he'd helped make history.
Zimmermann, an adjunct instructor of data communications at University College, oversaw the recent project to bury 3,750 feet of high-voltage power transmission cables, weighing more than 400 tons, beneath the Mississippi River in Chalmette, La.
The power lines went live in July 2004. "Nothing like this had been tried before," says Zimmermann, manager of project controls at Entergy. "We were faced with a different and interesting challenge. We came up with a new and innovative solution."
Zimmermann has taught network information systems at University College for seven years, an avocation he says he thoroughly enjoys.
"It's something different from what I do on a day-to-day basis," he says. "It's a different setting and I enjoy it."
While burying power lines beneath rivers is nothing new, Zimmermann says the sheer size of this project differentiates it from previous efforts.
"People have drilled underneath the river before, but it was the length, the depth, the physical size," Zimmermann says. "We combined technologies that have been used throughout many different industries but never really in the utility industry."
The project ended a dispute with Carnival Cruise Lines, which had threatened to reroute its 207-foothigh Conquest cruise ship from the river due to power lines hung too low to safely accommodate the mammoth vessel.
According to Zimmermann, a number of ideas were put forth to address the problem of low-slung power lines, including raising the towers, but the decision to bury the lines proved to be the best, most cost-effective solution.
"Myself and my team put together this plan to get it done and, hindsight being 20/20, we still feel it was the best way," Zimmermann says.
After months of planning, Entergy began work on the project in August 2003. Using global positioning system-guided directional drilling, a technology borrowed from the offshore oil industry, Entergy bore a twisting, turning 54-inch-wide tunnel 100 feet below the bottom of the Mississippi River.
"There are a number of natural gas pipelines that pass across the river at that location," Zimmermann says. "We had to weave through those so that we didn't hit a pipeline--and we had to meet Corps of Engineers requirements. There are so many agencies that you have to get permits from. These days everybody has rules and regulations. Those were among the challenges to this type of job."
Once the hole was drilled, 50-foot-long sections of pipe were fused into continuous lengths and pulled through the tunnel with a conical steel-pulling unit. Then, specially manufactured transmission cables were pulled through the duct system with a crane. The cables were attached to Entergy's transmission system and energized on May 1, 2004.
The project finished within budget and ahead of schedule. Zimmermann adds that Entergy hopes to use technologies developed for this project in the future.
"We're looking at a number of other areas in Entergy where we could possibly do it again," Zimmermann says. "We definitely want to use it in other places within the company and within the industry. I've talked to a number of other companies about the technology and how we did it."
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