A high-voltage transmission line buried 100 feet beneath the bottom of the Mississippi River at New Orleans, which incorporates a number of first-ever technologies and engineering techniques, has been energized by Entergy Louisiana, Inc., a subsidiary of Entergy Corporation.

"Our transmission engineers have written a new chapter in power industry history as they built on the company's record of supplying reliable power in a unique region both blessed and challenged by the constraints of natural boundaries and a rich but delicate ecosystem," said J. Wayne Leonard, Entergy's chief executive officer.

Applying oil-industry directional drilling and aerospace satellite guidance, Entergy's transmission engineers developed a way to permanently resolve the issue of ever-larger vessels entering the port of New Orleans.

The company's new high-voltage transmission lines are housed inside a flexible duct system of 12 pipes of varying diameters nearly 4000 feet long, weighing over 400 tons. The transmission cables within the ducts are among the longest, heaviest unspliced underground transmission cables ever manufactured.

Enameled strands and the use of fiber optics, along with their continuous length, size, ratings and voltage class make the transmission cables unique.

Project Details

After months of planning and staging, work on the under river transmission cable project began last August. A horizontal directional drilling unit, guided by GPS technology, wound a path beneath the river bottom and exited on the opposite bank four inches from its target point.

Fifty-foot long sections of color coded pipe were fused into continuous lengths, each approximately 4000 feet long. The twelve separate pipe strings were bound together. The lead end of the bundle was attached to a conical steel pulling unit. A four-foot diameter tunnel was drilled beneath the river bottom and the pipe bundle pulled through.

The continuous length high-voltage transmission cables were then pulled through their designated parts of the duct system and terminated on both sides of the river. The cables were attached to Entergy's transmission system and energized on May 1, 2004.

The project was completed ahead of its June 2004 completion date, which had been announced in December of 2002.

[FACT SHEET: Under River Transmission Cable Project]

-- December 2002: Entergy announces plan to bury the high-voltage transmission lines crossing the Mississippi River between Chalmette and Algiers beneath the river bottom so large vessels can sail to the Port of New Orleans without special maneuvering.

-- As a short-term solution to large vessel access to the port, Entergy reconfigured transmission towers and subsequently raised overhead transmission lines spanning the river. Before the lines were raised, when large cruise ship passed under lines, lower lines spanning river were de-energized. The Coast Guard, River Pilots, Entergy and others collaborated on the short-term solution.

-- The under-river transmission line project was completed May 1, 2004 ahead of the announced June estimated completion date

-- Transmission cable for the under-river project was specially ordered and manufactured. Manufacturing and delivery took less than one year. The cables were delivered to New Orleans in December 2003.

-- Approximately 45,000 feet of the specially-designed, continuous (unspliced) high voltage cable, weighing nearly 1,000,000 pounds, manufactured by J-Power Systems in Japan, was required for the project.

-- July 2003: crews began joining 50-foot long sections of high density polyethylene pipe (HDPE) into "strings" approximately 3,500 feet long. When completed, about 46,800 feet of pipe, weighing approximately 750,000 pounds, had been fabricated.

-- Diameters of pipe used in project: two inches, ten inches and 18 inches.

-- Transmission lines are now buried 100 feet below the bottom of the Mississippi River. This required the deepest horizontal drilling across the Mississippi in history.

-- The total distance (pipe length) across the river -- approximately 3500 feet.

-- Total amount of pipe purchased for the project -- nearly 48,000 feet.

-- Total weight of the pipe -- approximately 800,000 lbs.

-- Total length of cable purchased for the project -- approximately 45,000 feet.

-- Total weight of cable -- nearly 1,000,000 lbs.

-- Longest single length cable of this design ever manufactured and installed.