To strengthen power service reliability for customers in southeast Louisiana and comply with NERC performance requirements, Cleco Power and Entergy Louisiana are working together to construct a 36-mile storm-hardened transmission line from Gray to Patterson.
While Entergy’s portion, a 24-mile stretch of line from their Terrebonne Substation to Amelia, was completed in March 2018, Cleco began routing and designing its portion of the line in early 2016. In July 2018, Cleco received the required permits and began right-of-way clearing in advance of construction on its 12 miles of the new 230kV transmission line, connecting it from the tie point in Amelia to Cleco’s Bayou Vista Substation.
“This project is extremely unique as the line is being built across 93 percent wetlands, meaning we’re relying extensively on helicopters and marsh equipment to minimize impact on the wetlands,” said Lance Speer, Cleco senior engineer and construction manager for the project. “Included in that terrain are two islands, Avoca Island and Bateman Island, which have no road access.”
Cleco’s portion of the new line includes 101 new steel transmission structures. The majority of these structures will range in height from 80- to 110-feet, which is nearly triple the size of the average utility pole in a neighborhood. The structures will be supported on vibratory caissons, one-piece steel foundations weighing as much as 26 tons. The largest of Cleco’s structures will be approximately 239-feet tall, the equivalent of a 22-story building, in order for the line to cross the Atchafalaya River. The line also is crossing three other major waterways: Bayou Shaffer, Bayou Boeuf and the Gulf Intracoastal Waterway.
“There are currently 11 substations in the area where the line will be routed - seven belong to Cleco, two belong to Entergy, one to Louisiana Generating and one to Louisiana Energy & Power Authority. All 11 of these substations are served from two lines,” said Chris Thibodeaux, Cleco manager of transmission strategy and support. “This project adds a third source into that area midway between the 11 substations, therefore strengthening reliability along the Louisiana Gulf Coast region.”
Cleco’s portion of the project will cost approximately $62 million, which includes the construction of the line, power for lights on the water-crossing structures and additional work. The other large part of the project is the expansion of Bayou Vista substation, which includes the installation of an autotransformer, additional high voltage breakers and a new control house.
Thibodeaux continued, “When the project is completed, the line will be able to withstand winds up to 120 mph.”
The new transmission line also is designed to utilize horizontal vee insulator construction, which helps protect the structures should something fly or blow into the line which significantly lessens the potential for structural damage and speeds up the restoration process.
Following completion of construction, testing of the line, substation, relaying and protecting equipment will be performed by both utilities. Following testing, the line and equipment are expected to be placed into service in mid-2019.