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environment
FLOOD CONTROL
New Orleans Gates Are Hung As Call Rises for Taller Ones
 
By Angelle Bergeron
Heavy Lift. Contractors swing the first of two 175-ton sector gates into a cofferdam in the
Harvey Canal.

Contractors and engineers have set two 175-ton sector gates to block storm surge from forcing through a canal linking the Gulf of Mexico and the West Bank section of New Orleans. But as work was performed Aug. 3-4, the Army Corps of Engineers was asking whether the $40-million gates could be made taller to meet the latest, higher, storm protection criteria.

Purrington

“The gates are at [elevation] 111⁄2 ft,” says Jackie Purrington, the Corps’ New Orleans District-based project manager. “When the project was designed the authorized height was 91⁄2 ft, so this was more than sufficient. Within the last month or so, we received...funding to build to a 100-year elevation, so according to the new standards, the gate is four feet short. We’re looking at what we can do to remedy that.”

Multimedia:

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Installation of the Harvey Canal Sector Gates was begun in early 2004. Prior to Hurricane Katrina, it was the Corp’s single largest hurricane protection project. Originally scheduled to finish in 2006, it has met delays to accommodate modifications. Unless delayed again, it is now scheduled for completion by summer 2007, Purrington says.  The contractor is Boh Bros. Construction Co., and the heavy-lift specialist is Bisso Marine Co., both of New Orleans.

Purrington says several options are being studied to raise the gates to the 100-year standard. “We’re looking at whether the foundation can support adding onto the gate,” she says. Another option is to construct a wave break to reduce the storm surge and possibly eliminate the need for more height. “We’re trying to maintain progress while sorting things out,” Purrington says.

After Katrina hit last fall and brought a flood of federal funds to restore hurricane protections, the project was pushed up by several months to get the gates in place for the 2006 hurricane season.

However, with approval of additional appropriations that fund a drive to boost the city’s hurricane protection to 100-year standards, the final completion date, like the design specifications, has become a moving target. 

The gates are the central component of the “Westbank and vicinity” hurricane protection system. To build the 310x100-ft foundation, Boh Bros. constructed a cofferdam, excavated to -26 ft, poured a seal slab, de-watered and laid a concrete foundation that reaches 16 ft , says Vincent Saladino, Boh project superintendent.

At midnight on Aug. 3, the gates were loaded onto a derrick barge at the contractor’s fabrication yard in eastern New Orleans and moved in for placement in the canal. Bisso lifted with a 700-ton rig, while workers began the delicate process of placing each gate onto pintles—mushroom-shaped steel balls, 3 ft tall and 21⁄2 ft wide, at the lower pivot points of the gates.

 Once on the foundation, the floodgates will remain open for most of the time, providing a 125-ft horizontal clearance for vessel traffic. But they will be closed if there is a threat of storm surge.

(Photo top by Lane Lefort for ENR, below by Angelle Bergeron for ENR)

 


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