Hurricane Surge Protection

By Liz Moucka Krajca | September 28, 2010

New Orleans continues to prepare for the next big hurricane with levees and floodwalls.

"The Harvey Canal is a major canal on the Gulf Intercoastal Water Way (GIWW)," explained Gary Brouse, senior project manager of floodwalls for the United States Army Corps of Engineers (USACE). "This makes it open to a storm surge."

The community of Harvey is directly south across the Mississippi River from the New Orleans Garden District. The Harvey Canal provides sea access to a thriving industrial area with land access from Peters Road. The east bank of the Harvey Canal is on the west bank of the Mississippi River.

"The USACE was in the process of improving the levees along the Harvey Canal and was about 40 percent complete before Hurricane Katrina," Brouse continued. To accelerate construction since 2006, USACE divided the project into five separate contracts. Cajun Constructors was awarded three of the five Single Award Task Order Contracts (SATOCs).

Boh Bros. Construction Co., LLC was awarded a $62-million contract for the construction of 1,155 linear feet of floodwall to tie into the south end of the floodwall under construction by Cajun Constructors south of the Boomtown Casino. Boh's portion of the project will extend across the Hero Pump Station discharge channel and will follow Concord Road to Elmwood Marine. Boh's contract also includes building fronting protection for the Hero Pump Station.

Shavers-Whittle Construction, LLC has been awarded a $32,010,875 contract for west of Algiers Canal, where the Hero Pumping Station will tie into the levee at Algiers Canal east of Harvey Canal Floodwall.

Cajun Constructors recently completed flood gate structures at Bayou Segnette and is currently constructing 3,200 linear feet of reinforced concrete floodwall from Boomtown Casino to Hero Pump Station along Peters Road. This past February, Cajun Constructors was awarded a $132-million contract for the construction of 8,300 feet of floodwall to stretch south from the Harvey Canal sector gate at Lapalco Boulevard to the Peters Road cutoff.

An earthen levee along the undeveloped west bank of the Harvey Canal was raised to elevation 11 after Hurricane Katrina. A levee requires a 200-foot-wide swath of land, and the industrial real estate along the east bank was too precious. The final easement for this floodwall will be between 30 and 40 feet.

Floodwall Design

"After Katrina, the protection for the east bank was redesigned away from I-walls (sheet pile walls capped with concrete) to concrete T-walls," Brouse explained. "The T-walls will be a lot more resilient to overtopping and erosion. We also moved the alignment away from the canal to protect from barge traffic."

Before construction could begin, all the utilities, water, electricity, and telephone were relocated to the opposite side of Peters Road.

Although Cajun Constructors is self-performing between 80 and 90 percent of the work, they have subcontracted three firms to drive the piles for the foundation: Cajun Deep Foundations, a division of Cajun Constructors; Gulf South Piling; and Richard Goettle, Inc.

The wall is constructed as a series of 30-foot-long monoliths. The foundation of the T-wall begins with steel sheet piles driven vertically into the ground to prevent water from undercutting the wall. "Depending on the section and soil conditions, the sheet piles vary from 60 feet long to 84 feet long," said Jamey Sandefur, project manager for Cajun Constructors. "The actual support for the wall is provided by battered steel H-piles that range from 125 to 140 feet long; however, most are 130 feet long." Symons Forms are used to create the drainage structures in the wall's substructure.

Tom Charrier, Cajun program manager, added, "The battered H-piles provide greater support in the discounted soil conditions that range down to minus 50."

When driving the battered H-piles into the substructure, flag crews coordinate to temporarily stop traffic along Peters Road. During alignment and for the first portion of the pile driving, the steel H-piles extended out over Peters Road, creating a hazardous traffic situation. Teams of cranes drive piles simultaneously in different 30-foot sections, requiring the flaggers to coordinate closely with the pile driving teams. Each H-pile driving crew consists of a 250-ton crane, mostly Manitowoc 4100s and 888s, and a 100-ton rig assigned to it to stabilize lead wires.

Allan Darouse is the Cajun Constructors superintendent over the two task orders still under construction. These are readily identifiable by the file of 37 (at last count) cranes lining a little over three miles of Peters Road. In addition to the H-pile driving teams, smaller cranes make the area a beehive of activity. Various makes of 175-ton cranes unload the H-piles, which are delivered by barge via the Harvey Canal, and 100-ton rigs are kept busy in the lay-down yard. Cajun uses 70-ton and 100-ton cranes for pouring concrete.

Darouse described the wall: On top of the H-piles to ground level, the base slab is poured in 30-foot-long sections, 19 feet wide, and ranging in thickness from 3.5 feet to 5.5 feet at the southern end. Within the slab is a triple mat of No. 11 rebar. QPL has been the rebar installation subcontractor for all three task orders. Sitting on that base slab is the actual floodwall, which is 2.5 feet thick and varies in height from 16 to 21 feet to achieve top elevation of 14 MSL, according to Sandefur and Charrier. "A fluted architectural finish is created with DOKA forms on the protected side of the wall facing Peters Road," Darouse added.

By the time these three Task Orders have been completed, Cajun will place approximately 78,000 cubic yards of concrete. Concrete is being delivered by two suppliers that have facilities nearby: Carlo Ditta, which has a batch plant just across the canal, and Lefarge's two area plants.

Massive steel swing gates are installed at each property owners' driveway entrance. "The 27-inch-thick steel gates, which are being fabricated and installed by Manufab, are hung on stainless steel hinges with 6-inch- diameter pins," said Dave Daniels, USACE inspector. "The gates open toward the canal, so that floodwaters would push the gates against the wall, increasing the seal." All businesses between the canal and the floodwall would be flooded in that event.