A precast concrete pile cap, spun-cast piles and closure piles come together to form a storm surge barrier that will better protect New Orleans from future violent weather attacks on the Gulf Coast. This massive project stretches two miles along the Gulf Intercoastal Waterway and beyond the billion-dollar mark, designed to protect against 100-year storm surges.
By Sue McCraven
Photos courtesy of Shaw
In one of the biggest storms to make landfall in U.S. history, Hurricane Katrina, armed with 140 mile per hour (193 km/h) winds and 20-foot- (6-m) high surges, overtopped and powered through half of the Army Corps of Engineers’ flood protection system for the City of New Orleans. More than 1,830 people lost their lives to the fury of the August 2005 hurricane and its aftermath in the coastal areas of Mississippi, Alabama and Louisiana, with the majority of human loss occurring in the low-lying and poorly drained soils of New Orleans and its nearby parishes.
The American Society of Civil Engineers’ 2006 assessment report stated that the 350-mile-long (560-km) system of levees and floodwalls in New Orleans “failed catastrophically” and that the pumping stations designed decades ago were never meant to function in a major hurricane or to prohibit flooding once levees were overtopped or breached. To their credit, and despite mitigating circumstances, the U.S. Army Corps of Engineers (Corps) took full responsibility for structural flood control failures in New Orleans. Today, with more than $1.3 billion in federal funding, the Corps is building the largest civilian project of its kind in the world: the two-mile-long (3.2-km) Inner Harbor Navigation Canal Lake Borgne Surge Barrier (IHNC) that will close off the Mississippi River Gulf Outlet (MRGO) and better protect residents along the Gulf Intracoastal Waterway (GIWW) from 100-year-level storm surges. Three gates will be built into the barrier wall for vessel transport and closures (see Figure 1A and Figure 1B).
Shaw of Baton Rouge, La., was selected as prime contractor on the design/build IHNC Surge Barrier project with subcontractor TMW, a joint venture of Traylor Bros. Inc. of Evansville, Ind.; Massman Construction Co. of St. Louis, Mo.; and Weeks Marine of Cranford, N. J. This article focuses on the challenges faced by the producers of the precast products that comprise much of this massive concrete and steel project: Tindall Corp. – Mississippi Division of Moss Point, Miss., produced the 92-ton (83-tonne) precast pile caps for the surge barrier. Gulf Coast Pre-Stress of Pass Christian, Miss., is fabricating the 2,512 pieces of 18-inch-square (457-mm) precast closure piles, and together with Bayshore Concrete Products of Cape Charles, Va., are fabricating the thousands of cylindrical spun-cast sections that make up the 144-foot-long (44-m), 88-ton (76-tonne) soldier piles required for this extraordinary endeavor.
How Tindall got its Biloxi back
Tindall Corp.’s waterfront facility in Biloxi, Miss., emerged from the deluge of Hurricane Katrina to play a critical role in building stronger flood protection for the Gulf Coast. The Biloxi precast plant sat under 9 feet of seawater the day after Hurricane Katrina’s surge waters washed away everything but the concrete footings for a half-mile inland in coastal communities in Mississippi. “When the water drained away,” explains Alex Guthrie, Tindall Mississippi Division senior project manager, “over 300 boats littered the yard and we lost 80 percent of our store materials, all our computers and the office records were history. The beds and Mi-Jacks were salvageable.” Tindall purchased a new 100-acre (41-hectare) site and built a
state-of-the-art facility in Moss Point, Miss., 5 miles (8 km) inland from the Gulf of Mexico.
But just a few years later, Tindall needed to get the Biloxi site back in order to provide the shipping logistics to successfully bid for work on the two-mile-long barrier project. Because Biloxi is strategically situated on the Gulf, Tindall could ship the precast pile caps built there via barge to the Bayou Bienvenue construction site about 60 miles (97 km) away. A pile cap is better shipped by barge than by truck when it is as massive as 15 feet × 18 feet × 6 feet (4.5 m × 5.5 m × 1.8 m) and weighs in at 92 tons (83 tonnes). By leasing back a part of the Biloxi site, Tindall was prepared for a successful bid.
Pile cap designs multiply on a work in progress
When asked about the challenges of the job, Guthrie acknowledges a design/build project this large often becomes an exercise in the ability to adapt to ongoing design changes and to manage the extensive paperwork in a multi-tiered approval process. “Tindall has gone through three to four design changes resulting in 23 different cap designs; about a dozen of these
have final approval. We were awarded the project in December 2008, began design in February 2009 in advance of construction, and in the first months of 2010 we are still dealing with a work in progress.” The majority of the 350 required caps are left- and right-hand designs and about 50 are end, expansion, isolation or special cap applications. In addition to numerous design changes, precast tolerances were very tight. “We were used to meeting tolerances prescribed by DOTs and AASHTO,” says Guthrie, “but there were stricter tolerances to meet in the Corps project.”
Tindall was also required to develop a loading and working plan for each type of product shipment made by barge. Because the channel at Biloxi is too narrow for the largest barges, Tindall loads about eight pieces (1.5 million lb [697,000 kg]) on smaller barges, and then the barges are pushed by tug to the construction site. At the barrier wall, TMW signs off to take over product installation (see Figures 2-4).
Custom steel forms and curing in hot weather
Maintaining concrete curing temperatures at less than 160 F (72 C) when Gulf Coast summer temperatures reached 100 F (39 C) required ice chips and chilled water in the mix. “We maintained the concrete going into the forms at 76 F (25 C) to compensate for the heat of hydration,” says Guthrie. “Six new custom steel forms, 3/8-inch-thick (9.5-mm), were purchased for this project so that we could meet the demands of rapid installation.” Unlike typical precast production, Tindall could not do next-day stripping of forms. “We had to wait between 36 and 48 hours before we could strip the forms after pours; the client specified a slow-cure mix design to minimize cracking, and the sheer mass of concrete required a longer cure.” With the purchase of specialized forms, more than 30 additional people were hired to maintain the high production rates for the project. Ramps were built for the ready-mixed trucks to reach the top of the tall pile cap forms. Quality control is paramount. At the time of publication of this article, Tindall expects to be about 75 percent complete with production for the surge barrier wall with about 60 percent of the product installed.
Unprecedented production schedule required precaster team work
“The schedule for delivery of the spun-cast pile production for the IHNC Surge Barrier was so unprecedented that no single producer could commit to it,” says Don Theobald, vice president of engineering for Gulf Coast Pre-Stress (GCP), of Pass Christian, Miss. Bayshore Concrete Products (BCP) of Cape Charles, Va., and GCP worked simultaneously to produce 1,271 full-length, 66-inch-diameter (1,676-mm) cylinder piles to supply precast product to meet the production demands of several ongoing areas of construction along the barrier wall.
Because spun-cast cylinder piles are made in 16-foot sections and then assembled together with post-tensioning to make a completed pile, GCP alone had spun more than 6,300 sections before assembling the first 144-foot-long (44-m) pile. This early onset of fabrication “enabled the designers and geotechnical personnel to finalize designs and establish pile lengths while production was continuing,” explains Theobald. Once the pile lengths were established and released for fabrication, GCP and BCP were able to ship loads of preassembled piles in just a few days. “As a result,” says Theobald, “the pile driving contractors did not have to wait on materials.” (see Figures 5-6)
The smaller precast pieces between the cylindrical piles are 18 inch x 18 inch × 60-foot-long (457 mm × 457 mm × 18.3-m long) prestressed piles called closure piles (see Figure 7). There is a closure pile on each side of the opening between the 66-inch-diameter (1,676-mm) spun-cast cylinder piles. All closure piles were furnished by GCP. About 8 inches (205 mm) of one corner of the square closure pile is cut off to provide a cavity that was later grouted to establish a watertight fit between the cylindrical soldier piles.
High precast design loads at navigation gates
GCP has cast 43,300 lineal feet (13,198 m) of 24-inch-square (610-mmsquare) piles (426 total pieces) for the GIWW Bypass Gate Structure. GCP is producing 200 precast piles for another vertical-lift navigation gate that will be operational in Bay Bienvenue. The barrier wall will contain two floodgates (a swing barge gate and a sector gate) and one vertical lift gate.
“Because of the design loads on the piles at the gateways,” says Theobald, “the pile design was quite unusual – all required heavier than normal spiral wire, W14 (0.422-inch diameter [10.7-mmdiameter]), whereas the typical size spiral pile wire used in our area is a W4 (0.225-inch-diameter [5.7-mm-diameter]). In addition to the prestressing strands, the head of each square tension pile required 20 No. 8, 16-foot-long (4.9-m) reinforcing bars along with a 2½-inch-diameter (63.5-mm), 8-foot-long (2.4-m), high-strength tension connection rod.”
Six days per week, 24 hours per day, 400 days
“We were, of course, familiar with fabricating large spuncast piles for bridge foundations and harbor applications,” says Michael Spruill, chief operation officer for production at GCP in Pass Christian, Miss., “and we had worked with the Corps before. But this is the first time we had produced our 66-inch-diameter (1676-mm) spun-cast piles for anything like the magnitude required for this surge barrier wall.” The product may have been the same, but nothing else was typical for GCP in its production work for the IHNC project. While not experiencing the numerous design changes required of Tindall, a dramatic change in the normal scheduling routine proved to be the biggest adjustment for GCP staff.
“Sure, we were used to working five days per week, Monday through Friday,” explains Spruill, “and we typically produced about 10 16-foot-long spun-cast piles per day.” Overnight, GCP began operating 24 hours per day and six days per week – a huge scheduling change – to produce four times its typical product yield. “Months before the piles were needed on the project, we were producing and stockpiling 36 to 40 sections a day,” Spruill recalls. Seventy additional workers, including pulling staff from other areas of production, were needed to meet pile production for the project.
Nine spun-cast pile sections are joined together to form a 144-foot-long pile weighing 175,000 pounds (88 tons), the size specified by the Corps for driving into the muddy soils beneath Bayou Bienvenue. GCP loaded 10 piles on each of three barges, filling one barge per day. Once three barges were loaded, “we’d push the three barges in tandem to the construction site,” says Spruill, for a shipping distance of about 45 miles (72 km).
At the beginning of 2010, GCP was finished with production of about 70 percent of the spun-cast piles required by the Corps for the IHNC Surge Barrier; Bayshore Concrete Products produced the balance of the spun-cast piles for the project.
No harbor of refuge : Ocean barges during hurricane season
From May to October 2009 and during the height of the South Atlantic hurricane season, Bayshore Concrete Products of Cape Charles, Va., had to ship its spun-cast piles on big ocean-going barges more than 1,500 miles (2,400 km) around Florida’s peninsula to Bayou Bienvenue. “We shipped 18 to 21 completed piles – that’s about 1,800 tons (1,600 tonnes) of precast product per barge – on double-barge tows pulled by Dann Ocean Towing of Tampa,” says Chad Saunders, project executive with Bayshore Concrete.
The typical trip took 14 days, running from Cape Charles to New Orleans, which left loads exposed for an extended amount of time once underway (Figure 8). Bayshore had eight barges and three tugs in service during the height of shipping. “Ports-of-refuge close during tropical storms and refuse harbor to large vessels like barges for fear of the damage they may wreak on docks and facilities should they break free of their moorings,” says Saunders “I once received a call from the tug captain in the early morning – who was pulling our loaded barges to the Gulf Coast construction site – saying that a fast-moving tropical weather system came across Florida from the Gulf to the Atlantic and his only recourse was to turn the barges into the wind and ride out the bad weather. Fortunately for us, we were able to withstand these conditions due to the use of naval architects and surveyors who ensured that the products were loaded and fastened properly.”
Even the U.S. Coast Guard served notice to the barge operators that if high winds came up, the vessels must leave the construction site waters and seek safe haven elsewhere. “These strict marine safety precautions are all in the wake of the destruction caused by Hurricane Katrina,” says Saunders. “In fact, should a hurricane be imminent, any barges left in the area would be addressed by the Coast Guard, resulting in stiff penalties to the owner.” Needless to say, with 13 total shipments, Saunders learned a great deal about the perils of ocean-going shipping in fulfilling Bayshore’s precast contract for the IHNC Surge Barrier project.
The giant proves agile indeed
The U.S. Army Corps of Engineers took a good deal of harsh criticism from a number of academic and professional sources in the aftermath of Hurricane Katrina. Charlie Hess, senior vice president and project manager for Shaw in New Orleans, understands that many people in the New Orleans area hold the Corps accountable for deficiencies in the design of the earthen levees that were built 50 to 60 years ago. Hess has more than 40 years of construction experience, including 32 years with the U. S. Army Corps of Engineers and as the director of Corps civil works operations, and his work in Iraq and with the U.S. Department of Homeland Security.
Levees and floodwalls of necessity were built on extremely poor soils to provide a measure of flood control for New Orleans, a city that lies in a virtual bowl below sea level. Hess explains that “Hurricane Katrina would have challenged any flood protection structure.” When construction is complete in July 2011, IHNC Surge Barrier will be a truly remarkable feat for the U. S. Corps of Engineers, whose past civil projects averaged 16 to 17 years in duration. In this largest project of its kind in the world and the largest design/build, cost-type civil project in Corps history, “We find a very large-scale endeavor and a very short fuse,” Hess says.
To prove his point, Hess explains that in the fall of 2007, with only 5 percent of the design concept complete, the Corps began accepting full-scale proposals with estimated costs from four different short-listed firms. By April 2008 contracts were awarded, and by May 2009 construction commenced on the barrier wall. This design/build, cost-type approach “is a huge transformation for an organization that historically provided builders with a plan and specs and asked for fixed-price proposals,” claims Hess. The IHNC project benefits from being fully funded by Congress in contrast to many civil works projects that are intermittently funded over many years.
Precast : high standards in an industrialized approach
“This entire job takes place in the water. We are essentially constructing this surge barrier in a marsh,” says Hess. “By using precast elements, we can ensure high quality control of the products in a very consistent and homogeneous construction style. Precast allows us to take an industrialized approach, almost assembly-line efficiency, in erection of the structure.” A trestle system allows product delivery and installation to take place simultaneously at six to seven locations along the barrier wall (see Figures 9-10). Template element equipment, housed on the trestle platform, allows for a high degree of precision (plus or minus 3 inches [75 mm]) in the installation of the soldier and batter piles.
With precast concrete’s just-in-time delivery of consistently high-quality product, this unprecedented civil engineering project has risen 26 feet (7.9 m) above the Gulf Coast bayou at a remarkable pace. As a case in point: In just five months and 12 days, working two pile drivers two shifts per day six days per week, crews finished driving 1,271 spun-cast soldier piles (see Figure 11).
Strength must be met with strength, and in the face of such power and fury as Hurricane Katrina, the people of New Orleans and Louisiana can now have some assurance that these precast concrete storm surge barriers will help protect their property and lives.
Sue McCraven, NPCA senior technical consultant, is a civil engineer, technical writer and editor, and environmental scientist who has contributed numerous articles and studies to prominent scientific journals.