Defending. New Orleans

D efending N ew O rleans Special Report ight years after Hurricane Katrina slammed into the levees and floodwalls that were supposed to protect the ...
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D efending N ew O rleans Special

Report

ight years after Hurricane Katrina slammed into the levees and floodwalls that were supposed to protect the city of New Orleans, causing multiple breaches that flooded much of the region for days and even weeks, the U.S. Army Corps of Engineers is completing a new line of defense for New Orleans that features miles of raised, reconstructed, and reinforced levees and floodwalls, along with enormous sector gates and surge barriers, including what is believed to be the world’s largest drainage pump

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station and a nearly 2 mi long barrier structure that was the largest civil works project ever undertaken by the Corps. The new physical infrastructure, together with changes in procedures and other improvements, were designed to make the city safer than it’s ever been. But even with a budget of more than $14 billion—of which $10.4 billion had been spent at press time—the Corps readily admits that this new system still does not actually protect New Orleans. Instead, as its name implies, the new Hurricane and Storm Damage Risk Reduction System (which goes by the unwieldy acronym HSDRRS, pronounced “HIZ-ders” by some) is designed primarily to reduce the risk that the residents of New Orleans face from storm surge and flooding if and when another major hurricane strikes the region. Prior to Katrina, the levees and floodwalls that surrounded New Orleans were referred to as a hurricane protection system, but that designation created “a false sense of security,” notes Colonel Edward R. Fleming, the commander of the Corps’s New Orleans District during the construction of much of the HSDRRS. As he explains, “A

U.S. Army Corps of Engineers, all

Eight years after Hurricane Katrina struck, the New Orleans region is being ringed by a more than $14-billion system of stronger and higher levees, improved floodwalls, and new storm surge barriers that the U.S. Army Corps of Engineers says provides the best defenses against hurricanes that the region has ever known. This special report examines what was constructed, how it is expected to work, and why various experts and groups have such strong feelings pro and con about the new system. . . . . By Robert L. Reid

A crisscrossing array of crane booms, opposite, helped the Corps to complete at least 2 mi of new T-wall floodwalls per month along a 23 mi long section of levees in St. Bernard Parish. The foundations of the new levee known as LPV-111 were buttressed via a method known as deep soil mixing and involved the installation of more than 18,000 stabilizing columns.

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levee doesn’t protect anybody or anything; a levee is just an additional feature that reduces risk” from storm surge. In such a risk reduction system, however, there are measures other than just federal flood projects to help reduce the risks, some undertaken by state and local authorities, including the elevation of buildings or critical equipment, the protection and restoration of barrier islands and coastal wetlands, and even the evacuation of populations that are in harm’s way, Fleming says. Given the combined threats to New Orleans of increasingly powerful storms that many climate scientists foresee, together with predictions of rises in sea level and the ongoing subsidence of the land in the region, “there will always be some residual risk” for the people of the Big Easy, Fleming says. And this is why, having learned critical lessons from Katrina, the Corps has adopted “a whole different mind-set,” he stresses. The change is more than a semantic switch away from “protection.” For the Corps’s New Orleans District, at least, it represents a tremendous change in the Corps’s approach to the engineering, financing, construction, and even purpose of major civil works. Fleming declared the HSDRRS “complete” in May after a series of practice drills at several of the new system’s major facilities in preparation for the 2013 hurricane season. He turned over command of the New Orleans District to Colonel Richard L. Hansen later that same month. Like “protection,” however, the designation “complete” also must be explained because certain critical construction projects for the system are still in the works. Of prime importance, the levees are not yet armored and construction has just begun on a series of permanent pump stations and closures to replace interim facilities at three outfall drainage canals along Lake Pontchartrain. But the system is complete in the sense that it is now capable of withstanding the surge from a storm that has a 1 percent chance of being equaled or exceeded in any given year, also known as a 100-year storm. The ability to withstand a 100-year storm is the standard used by the Federal Emergency Management Agency to certify the region for participation in the National Flood Insurance Program; the Corps has submitted a National Flood Insurance Program levee system evaluation report on the new levees to the Federal Emergency Management Agency, as required, but at press time certification from the program had not yet been granted. The new system will actually defend the New Orleans region today at a level above a strict 100-year standard, Fleming notes, given that it was designed to accommodate the storm surge of a 100-year event over the next 50 years. The design took into account the expected rise in sea level as well as the subsidence of land over those five decades. Moreover, the planned armoring of the new levees will be designed to offer the resilience necessary to survive the storm surge of a 500-year event. The armoring of levees is key to the Corps’s efforts to provide the resilience to withstand a 500-year storm, notes Fleming. Although the levee and floodwall elevations are designed to the 100-year storm standard, “if we get a 500-year storm and get overtopped, there will be flooding,” Fleming concedes, “but you’re not going to get the catastrophic [levee and floodwall] failure or the breaches like you would have seen before.” That idea is critical to the Corps’s new approach to risk reduction. New Orleans has often been flooded during ma[ 5 0 ] C i v i l E n g i n e e r i n g n o v em b e r 2 0 1 3

100-Year Risk Reduction System

jor storms, but the water was simply pumped out afterward. Considerable damage resulted, but there was not the citywide devastation that occurred during Katrina when the levees and floodwalls were breached, which meant there was no way to stop the water or send it back out again. The new system is also considered complete because for the first time since work began in the aftermath of Katrina, no temporary closures will be needed to secure construction openings during future storms because those openings have now all been closed, explained a May 30, 2013, issue of Task Force Hope’s Status Report Newsletter. (Task Force Hope is the name of the Corps office that is responsible for oversight of the HSDRRS program.)

As the clarification of such terms as “protection” and “complete” should indicate, however, little concerning the HSDRRS and post-Katrina New Orleans has been simple or easy. For example, the new system was tested in August 2012 by Hurricane Isaac and performed exactly as designed, according to Mike Stack, Jr., P.E., the New Orleans District’s chief of emergency management (see “New Orleans’ Defenses Weathered Isaac ‘Very Well,’” Civil Engineering online edition, September 25, 2012, http://www.asce.org/CEMagazine/Article.aspx?id=25769811641&terms=mike+stack+ hurricane+isaac). But instead of being able to breathe the proverbial sigh of relief, the Corps faced criticism because while the new defenses had protected people and property

within the perimeter system from Isaac’s surge-related flooding, it was contended that the HSDRRS might have worsened the flooding in certain regions outside of that system, including portions of Plaquemines and St. John the Baptist parishes that had not experienced flooding during Katrina. And while many local stakeholders interviewed by Civil Engineering for this special report did agree with a statement by Fleming that “the system that’s in place right now is the best system that New Orleans has ever seen, clearly better than it was before Katrina,” they also expressed strong reservations about individual aspects of that system. In particular, they questioned the adequacy of the 100-year standard itself, a standard that many have noted might not even prevent n o v em b e r 2 0 1 3

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The 1.8 mi long Inner Harbor Navigation Canal–Lake Borgne Surge Barrier, considered the largest barrier of its kind in the world, was designed to prevent storm surge from Lake Borgne from rushing into the Inner Harbor Navigation Canal and the Gulf Intracoastal Waterway.

the overtopping that the region experienced during Katrina, which produced storm surges and waves equivalent to those of a 400-year storm. A 100-year storm standard was declared “inadequate for flood protection structures in heavily populated areas such as New Orleans, where the failure of the system would be catastrophic,” according to a 2009 report by the National Academy of Engineering and the National Research Council entitled The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness. Likewise, ASCE’s Hurricane Katrina External Review Panel (ERP) declared the 100-year standard “unacceptable” in an April 15, 2008, letter to Lieutenant General Robert L. Van Antwerp, Jr., P.E., then the Corps’s commander and chief of engineers. The ERP conducted an independent technical review of the findings of the Corps-sponsored Interagency Performance Evaluation Task Force (IPET), which was established to assess the performance of the hurricane protection facilities in New Orleans and southeastern Louisiana during Katrina. Noting that the 100-year storm standard, even with a 500-year flood standard, means that there is a 10 percent chance every 50 years of Katrina-like catastrophic flooding and “loss of property, life, and lifestyle,” the ERP’s letter concluded that “this level of risk in the New Orleans area [is] far above that employed for other engineered structures.”

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ow the Corps managed to construct the HSDRRS despite numerous challenges and impediments, the technical details of the system’s major features and facilities, and how these efforts have been perceived and received, as well as what the Corps might have to do next in terms of risk reduction in southeastern Louisiana, will be explored in this special report, for which I visited several of the major pieces of the new system, spoke with the Corps’s leaders and project managers and with its critics, and pored over stacks

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of reports, letters, news articles, the minutes of government agency meetings, and other documents. The consensus among those interviewed is that the HSDRRS should enable the residents of the Big Easy to rest a little easier during future hurricane seasons. However, they note that such an ambitious infrastructure project will never really be finished. Even the new levees will need additional lifts over time, and in fact work has already been done on one section. Moreover, some feel strongly that critical aspects of the new line of defense around New Orleans should be reconsidered and potentially even reworked. To understand the facilities that were constructed for the HSDRRS and why and how the Corps’s work on this project differed greatly from the many other efforts undertaken by its engineers, it’s best to start with a reexamination of what went wrong during Katrina, especially since many of the actions and decisions made before and even during that storm helped to guide the decisions about the design, construction, and funding of the new system. First, it’s important to remember that much of the New Orleans region is located below sea level and that flooding during hurricanes is hardly a new problem there. But during Katrina the water could not simply be pumped out because of a series of failures that included breaches in the region’s flood protection defenses at about 50 distinct locations and problems with the region’s pumping stations, according to the ERP’s 2007 report, The New Orleans Hurricane Protection System: What Went Wrong and Why (see “The ERP Report: What Went Wrong and Why,” Civil Engineering, June 2007, pages 54–61, 73–76). Thus, the devastation during Katrina was a “unique” natural disaster in which “much of the destruction was the result of engineering and engineering-related policy failures,” the ERP report concluded. In particular, although many of the failed levees had been overtopped by floodwaters that eroded the levee material, at

least seven of the major breaches were caused by the failure of the concrete floodwalls known as I walls that had been constructed atop levees that were not armored or otherwise protected against erosion. These included I walls at two of the outfall canals on Lake Pontchartrain—the 17th Street Canal and the London Avenue Canal—which failed while the floodwaters were still about 5 ft below the top of the walls, “well below the design water level,” the ERP report noted. Moreover, at the 17th Street site, the engineers “responsible for the design of the levee and I wall overestimated the soil strength,” the ERP stated. Potential problems with I walls in general had been discerned by the Corps as far back as 1985, when a field test under high-water conditions “revealed the potential for large I-wall deflections,” the ERP said. But as “research and new information evolved in the 1980s and 1990s, the design of the existing I walls was not checked for safety and stability in the light of new information,” the ERP explained. Elsewhere in New Orleans, Katrina showed the city’s pumping stations to be inadequately designed. The pumps lacked the capacity to handle the water levels that resulted, and the pump station buildings lacked the structural strength to withstand the wind and water forces of the hurricane, the ERP concluded. In Jefferson and St. Bernard parishes, for example, nearly all of the pump station operators had to be evacuated during the storm, which meant their pumps lay idle. The pumping stations at the south end of the 17th Street, London Avenue, and Orleans Avenue outfall canals were designed nearly a century ago to pump out rainfall but were “never strengthened or retrofitted” to resist the hydrostatic loads of storm surge, even though these facilities had come to be considered part of the region’s hurricane protection system, the ERP noted. During the design of the pre-Katrina hurricane defenses, Congress had authorized the Corps to protect the region against “the most severe combination of meteorological con-

ditions that are considered ‘reasonably characteristic’ of the region,” which for the Corps has historically meant a hypothetical storm called the standard project hurricane, the ERP noted. But “reasonably characteristic” implied a storm that the ERP considered to be less extreme than, say, the probable maximum hurricane as defined by the National Weather Service. As a result, the pre-Katrina New Orleans hurricane defenses were “underdesigned,” the ERP concluded. In fact, when Katrina struck, the New Orleans region’s hurricane protection system was actually “a system in name only,” the ERP said, restating a conclusion reached by the members of the IPET, as well as by Lieutenant General Carl A. Strock, P.E., Dist.D.NE, M.ASCE, now retired, who served as the Corps commander and chief of engineers during Katrina and is now employed by the international engineering firm Bechtel. Originally designed to provide flood protection and remove rainfall from the city, the presumed system was in reality “a disjointed agglomeration of many individual projects that were conceived and constructed in piecemeal fashion. Parts were then joined together in ‘make-do’ arrangements,” the ERP explained. Moreover, because of the congressional budgeting process, “the stream of funding for the New Orleans hurricane protection system was irregular, at best,” the ERP stated. “If a project was not sufficiently funded, the Corps was often required to delay implementation or to scale the project back.” As Fleming explains, the Corps does not receive an annual budget from Congress; thus, he says, “we cannot just go out and build things.” Instead, the Corps must receive authorizations and appropriations—permission and funding—for each project on a case-by-case basis. In the New Orleans region that approach was followed over the past six decades, the first hurricane protection project for the region being authorized in the mid-1950s, Fleming notes. Unfortunately, it produced an

The Lake Borgne surge barrier’s 26 ft high wall is supported by an A-frame system that features more than 1,200 vertical concrete piles, each 66 in. in diameter, and more than 600 inclined batter piles, each 248 ft long and 36 in. in diameter.

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unfinished line of defense that by August 2005 was roughly 60 percent complete for parts of the city on the east bank of the Mississippi, which cuts a winding course through the New Orleans region, and only about 40 percent complete for the neighborhoods on the west bank, Fleming says. Furthermore, even what had been constructed was not always adequate. The levees susceptible to overtopping had not been armored, and the levees and floodwalls had not been designed with sufficient additional height to accommodate the “well understood” subsidence in the region, the ERP noted. A lack of coordination among the various federal, state, and local agencies responsible for the construction, operation, and maintenance of segments of the hurricane protection system—including the pre-Katrina levee boards, some of which also ran such non-flood-protection operations as airports, parks, and casinos—also meant that certain floodgates “were out of service and left open during Hurricane Katrina because of repairs, allowing water to flood through them unimpeded,” the ERP said. In other locations, the openings into key waterways or drainage canals had no protection at all against Katrina’s storm surge. To the north of New Orleans, the Lake Pont­ chartrain side, these openings included the mouths of the outfall canals and the Inner Harbor Navigation Canal, a 5.5 mi long channel that links the lake to the Mississippi. Likewise, there was nothing stopping storm surge from Lake Borgne on the eastern side of the city at the confluence of the Mississippi River–Gulf Outlet (MRGO)—designed as a shortcut for navigation between the Gulf of Mexico and the port of New Orleans—and part of the New Orleans portion of the Gulf Intracoastal Waterway, a navigable inland waterway that stretches from Florida to Texas. These unobstructed openings, as well as nearby breaches, contributed to the flooding that caused more than 1,100 deaths and sank the

Lower Ninth Ward, Chalmette, Gentilly, the part of the city east of the Inner Harbor Navigation Canal and north of the Gulf Intracoastal Waterway (“New Orleans East”), and other sections of the city under as much as 10 ft or more of water. A month after Katrina hit, a second hurricane, Rita, struck the New Orleans region, causing some of the areas flooded during Katrina to flood again as certain key levees were breached for the second time. “Clearly there were gaps in the physical construction of the system that caused it not to really be a system,” concludes Fleming.

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The Lake Borgne surge barrier features a 150 ft wide sector gate with two steel-framed segments that swing open and closed to provide navigation for vessels of shallow draft.

n the basis of the extremely hard lessons learned from

hurricanes Katrina and Rita, the State of Louisiana decided to consolidate many of the existing levee districts in the New Orleans region under two so-called super levee boards. The Southeast Louisiana Flood Protection Authority–East (SLFPA– East) has jurisdiction over three levee districts—the East Jefferson Levee District, Orleans Levee District, and Lake Borgne Basin Levee District—on the east bank of the Mississippi River, and the Southeast Louisiana Flood Protection Authority–West (SLFPA–West) has jurisdiction over the West Jefferson Levee District and the Algiers Levee District on the west bank of the Mississippi. The Corps also set out to make fundamental changes, many of which addressed the ideas outlined in the IPET and ERP reports, notes Robert G. Traver, Ph.D., P.E., D.WRE, M.ASCE, a member of the ERP team, a professor in the civil and environmental engineering department at Villanova University, and the director of the university’s Center for the Advancement of Sustainability in Engineering. In particular, Traver commends the Corps’s early efforts to install erosion protection on certain new and existing levees, which improved the region’s defenses during Hurricane Gustav, in August 2008, and applauds the

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The Bayou Bienvenue lift gate structure on the Lake Borgne surge barrier measures 56 ft wide by roughly 80 ft tall. It is designed primarily for recreational boats.

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extensive efforts that were undertaken by officials throughout southeastern Louisiana and in New Orleans itself to evacuate vulnerable populations prior to Gustav. To correct one of the harshest assessments from the IPET and ERP reports, the Corps sought to create an actual system that would defend the New Orleans area against hurricanes. This risk reduction system features a 133 mi perimeter of new, strengthened, or raised levees, along with floodwalls, gated structures, and pumps. The Corps’s efforts have been so comprehensive, Fleming adds, that some sort of work—raising, strengthening, repairing, or replacing—has been done to “every inch of this perimeter system.” The scope of the HSDRRS increases to 350 mi when all of the levees and floodwalls within the perimeter and in other planned projects in the region are included, and the new system also features a different type of floodwall, known as a T wall, to correct the problems caused by the earlier I walls. Existing structures, including gated barriers and pump stations, were strengthened and new facilities were constructed, especially where there had been no defenses at all against storm surge. And everything is tied into the existing levees on both banks of the Mississippi so that, in combination with new operating procedures that have been adopted, “we’ve worked very hard to make sure that it is in fact a system,” explains Fleming. Rather than relying on just that single “standard project hurricane” to determine the details of the new system, the Corps also took a new approach in analyzing the potential hazards, one based on IPET research that modeled 152 different possible hurricanes of different intensities. The modeling also looked at different tracks and explored how those storms might affect the new perimeter system, explains Mike Park, the chief of Task Force Hope. Using the best hydraulic modeling tools available

at the time, the IPET team studied storms that ranged from 50to 5,000-year events and considered such variables as water levels, maximum winds, storm size, speed, and direction. “It was a much more comprehensive definition of the hazard than anyone has ever had before to design a system like that,” notes Ed Link, Ph.D., M.ASCE, a senior research engineer in the civil and environmental engineering department at the University of Maryland and the leader of the IPET team. As with most civil works projects, the cost of the HSDRRS, more than $14 billion, was split between the Corps and the local sponsor—the State of Louisiana through its Coastal Protection and Restoration Authority. Approximately $9.6 billion was funded completely through federal money, while approximately $4.9 billion was covered through a cost-sharing arrangement, the federal government paying 65 percent and the local sponsor 35 percent. The Coastal Protection and Restoration Authority will also be the official owner of the projects once they are all completed and turned over to local control, although the operation and maintenance of the facilities, as well as portions of the state’s share of the construction costs, will eventually be the responsibility of the SLFPA–East and the SLFPA–West. In the New Orleans region, the HSDRRS consists primarily of two sets of projects that form distinct hydraulic units separated by the Mississippi—hydraulic units being developed portions of the region that require protection from storm surge. On the west bank of the Mississippi, in the hydraulic unit that the Corps formally refers to as the West Bank and Vicinity, the projects focused on risk reduction facilities and defenses in portions of St. Charles, Jefferson, Orleans, and Plaquemines parishes. The major civil works projects constructed here include the Gulf Intracoastal Waterway–West Closure n o v em b e r 2 0 1 3

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Complex, which features the nation’s largest sector gates and drainage pump station to prevent storm surge from entering two stretches of the Gulf Intracoastal Waterway. One is the Harvey Canal section (that canal, originally known as the Destrehan Canal, becoming part of the Gulf Intracoastal Waterway in 1924), and the other is the Algiers Canal section. Other major projects are the Bayou Segnette Complex, which involved the construction of a sector gate, a pump station, new floodwalls, and a levee, as well as the lowering of the existing Company Canal floodwall to create a new storm-water detention basin, and the Western Tie-In and the Eastern Tie-In, which, as their names imply, connect portions of the HSDRRS defenses to the existing Mississippi levees at locations that are actually to the southwest of the city, at Lake Cataouatche, and to the southeast, at the Hero Canal, near the point that the Corps designates river mile 70 (70 mi from the Mississippi’s mouth). In the second hydraulic unit, referred to formally as Lake Pontchartrain and Vicinity, the projects include civil works on the east bank of the Mississippi in portions of St. Charles, Jefferson, Orleans, and St. Bernard parishes. Among the major new risk reduction projects constructed in this unit are the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier, a 1.8 mi long structure that is the largest barrier of its kind in the world and is designed to prevent storm surge from Lake Borgne from rushing into the Inner Harbor Navigation Canal and the Gulf Intracoastal Waterway; the Seabrook Floodgate Complex, adjacent to New Orleans Lakefront Airport, on the shore of Lake Pontchartrain, which was designed to stop storm surge from coming south off the lake and also to work together with the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier; permanent closures and pump stations on the outfall canals along Lake Pont­ chartrain, now under construction; and a new floodwall and ramp for the existing parallel spans of the Lake Pontchartrain Causeway Bridge, which crosses the lake in a north–south direction. Although not technically part of the HSDRRS, the MRGO has been closed by constructing a rock dam across its channel, and the waterway has been “deauthorized as a federal navigation project,” explains Park, who adds that the Corps disputes whether the MRGO truly was the “conduit for storm surges that some have claimed.” The location of some of the new HSDRRS barriers helps to shield as much as 70 mi of levees and floodwalls from direct exposure to storm surge, notes Park. That is because the region’s perimeter defense previously followed the banks of those various canals and offered unobstructed openings. But now certain features of the new system close off those openings and essentially remove the canal levees and floodwalls from harm’s way. “So we’re defending on a much smaller front,” Park says, which

makes the new system more secure because “there are fewer things that can go wrong in a shorter perimeter.” Throughout the HSDRRS, the heights of floodwalls and other hardened structures were raised to elevations designed to accommodate storm surge, compaction, subsidence, settlement, and other possible changes over the next 50 years. These heights vary on the basis of the “much better understanding of storm surge potential” that the Corps has acquired since Katrina, says Park. So instead of constructing new levees or raising existing ones to a uniform elevation, the new system has been designed to achieve a “uniform level of risk reduction around the perimeter” to accommodate the 100-year storm surge potential at different sites, Park explains. To determine those individual levee heights, the overtopping rates at various elevations were analyzed, as were the still-water levels—essentially the storm surge without waves—for storms up to a 500-year event, Park says. The levee heights were then set at some point above those measurements for each particular location, he adds. In different sections of the east bank of the Mississippi, for instance, the levee heights now range from 12 to 26 ft above sea level because of the potential differences in storm surge at each location, and new floodwalls can take the elevations to more than 30 ft. The levees were also overbuilt where practicable to accommodate future conditions. Thus, a levee that needed to be only a certain height today was actually constructed somewhat higher to account for nearterm settlement and compaction, factors that the pre-Katrina levees did not address, Park explains. In St. Bernard Parish, a 23 mi section of levees that parallels the MRGO originally featured earthen levees approximately 14 to 15 ft high that during Katrina were battered by a still-water surge of as much as 18 ft and waves that reached 23 ft, says Chris Gilmore, P.E., a senior project manager for the Corps. Approximately 60 percent of the levees there were destroyed, he adds. So as part of the Corps’s efforts immediately after Katrina to provide new defenses as quickly as possible and then as part of the HSDRRS itself, the Corps rebuilt the remaining levees and constructed entirely new ones along that 23 mi section, raising the levees themselves to a height of 20 ft and capping the new levees with floodwalls that reached a maximum elevation of 32 ft, Gilmore says. After Katrina the Corps also adopted stricter specifications for the earthen materials it uses to construct levees, a change that sometimes made it “difficult to find the amount of borrow material that we did,” says Gilmore. The Corps engaged in “an unprecedented search for clay material,” seeking some 93 million cu yd of borrow material to complete the HSDRRS levees and floodwalls, explained a website created by the Corps “to serve as a reference for all landowners interested in providing clay material for these projects.”

The location of some of the new hsdrrss barriers helps to shield as much as 70 mi of levees and floodwalls from direct exposure to storm surge.

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The Seabrook Floodgate Complex, on the shore of Lake Pontchartrain adjacent to New Orleans Lakefront Airport, was designed to stop storm surge from coming south off the lake and also to work together with the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier.

The Corps is also in the process of raising and improving certain riverine levees along the Mississippi between river miles 70 and 85.5 as part of the 100-year risk reduction system, notes Fleming. The earthen levees and concrete floodwalls along this 15.5 mi section of the river could be improved as part of the HSDRRS because hurricane storm surge is the governing event in these locations. Levees improved in this way are referred to by the Corps as colocated. That means the height of a levee to reduce the risk from storm surge in a 100year event is higher at that location than the levee height required to protect people and property from riverine flooding. Elsewhere, the Corps cannot perform HSDRRS work on levees if riverine flooding is the governing event, one of the many complicated restrictions governing the work of the Corps, notes Fleming, who adds that the exact location of that distinction between riverine and storm surge flooding will probably move farther north on the Mississippi as sea levels rise. In addition to being raised, the HSDRRS levees and floodwalls along the Mississippi will be designed to offer greater resilience and longevity and easier maintenance, their slopes chosen so as to reduce wave run-up, adds Garnet Hardin, M.ASCE, a Corps project manager. In one area, a roughly 5 mi long levee section in New Orleans East flanking the Gulf Intracoastal Waterway east of the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier was reconstructed roughly 10 ft higher than it had been before Katrina and ultimately reached a height of approximately 28 ft. Known as the LPV-111 project (“LPV” denoting the Lake

Pontchartrain and Vicinity hydraulic unit), the new levee was so large that the engineers were especially concerned about consolidation of the levee material and subsidence, Park says. So prior to the construction of the larger levee section, the foundations were buttressed via a method known as deep soil mixing, auger drills being used to mix cement and water slurry into the soil to form a stabilizing column. Believed to be the largest such project in the United States, the deep soil mixing at LPV-111 involved 1.7 million cu yd of mixed material in the construction of more than 18,000 columns, each approximately 5 ft in diameter and 67 ft long on average, along the length of the levee. Deep soil mixing techniques were also used at the levees along the 17th Street and Orleans Avenue outfall canals. Another subsurface stabilization project in New Orleans East, where the soils are weak and marshy but the new levees required extensive footprints, involved the construction of a sand blanket several feet thick atop the footprint of the future levee and the insertion through that sand layer of approximately 250,000 wick drains, notes Park. The corrugated wick drains serve to preconsolidate the soil, creating “a pathway for groundwater to rise to the surface as we compress this under the sand blanket load, essentially pressing the water out,” Park explains. The wick drain system seems to be yielding benefits, Park adds, because little loss of elevation has been observed in the levees at which that technique was used. To address the problem of unarmored levees that were overtopped and failed during Katrina, the Corps plans to armor “virtually every point around the perimeter...in some fashion,” n o v em b e r 2 0 1 3

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Navigation Canal–Lake Borgne Surge Barrier, for example, fall into this category. In areas that did not lend themselves to major construction work, the Corps left the I walls in place but buttressed them with, say, “a support every six feet on center—sort of like studding a wall,” notes Fleming. However, he adds, “in the vast majority of cases we did switch to T walls.”

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The West Closure Complex features the nation’s largest sector gates and drainage pump station and was the site of a carefully planned and constructed floodwall along an environmentally protected area.

explained René Poché, a public affairs specialist for the Corps, who responded in writing to Civil Engineering questions. This armoring will be installed especially in such critical areas of the HSDRRS as the protected sides of levees, the transition points between levees and structures, and the points at which pipelines and utilities cross levee alignments, Poché explained. Although the final decisions on exactly which sections of levees will be armored and which methods will be used have not been made, the Corps has been testing different approaches and materials over the past several years with assistance from the U.S. Army Engineer Research and Development Center, Texas A&M University, and Colorado State University, which is equipped with a full-scale, computer-controlled wave overtopping simulator. The Corps and Louisiana State University have also conducted field tests on a section of levee in St. Charles Parish involving high-performance turf reinforcement mats through which grass was grown; various methods of mowing the grass also were tested during the experiment, which was carried out in the fall of 2011. More recently, the Corps conducted additional pilot tests involving five manufacturers of high-performance turf mats on two 5,000 ft long levee sections, one on an east-bank levee in St. Charles Parish and the other on a west-bank levee in the area encompassing Westwego and Harvey. At press time, additional armoring tests were under way. The armoring construction contracts are not expected to be awarded until June 2014, and construction is not expected to be completed until the fall of 2016. In contrast to the cost-sharing agreements governing most of the civil works projects carried out by the Corps, the cost of the armoring project, estimated at more than $300 million, will be borne entirely by the federal government, according to Park. The problems associated with I walls were resolved by [ 5 8 ] C i v i l E n g i n e e r i n g n o v em b e r 2 0 1 3

replacing most of those structures with more robust T-wall systems, so named because they resemble an inverted letter T, the horizontal section being at or below the ground. Angled steel beams formed from H-piles and reaching depths of 165 ft also were used to further brace the new T walls, and steel sheet piles were used to prevent water seepage. In one section of existing levees, for instance, more than 10,000 sheet piles were driven into the levees to depths reaching 70 ft, according to an article in the November 30, 2011, issue of Status Report Newsletter entitled “HSDRRS...What Lies Beneath?” In addition to providing greater robustness to the HSDRRS, the use of T walls in a 23 mi long section of levees in St. Bernard Parish also obviated the need to construct an impossibly large levee in that area, notes Park. If the levees there had simply been constructed to the heights deemed necessary, they would have required a footprint roughly 900 ft wide and therefore would have encroached on the nearby canals and marshland, Park explains. Instead, the T walls and their deep piles kept the levee footprints at a more manageable size and facilitated the fastpaced construction schedule, which involved the “extraordinary effort” of completing at least 2 mi of floodwalls per month in the lead-up to the 2011 hurricane season, Park says. He recalls an iconic construction photo taken during the project (see the image on page 48) that depicts something like 80 crane booms silhouetted against an orange sky at dusk. As he explains, when people ask him how 2 mi of floodwalls could be constructed each month, “I show them that picture and say, ‘This is how you do that.’” Some I walls remain within the HSDRRS, including walls that have been rendered redundant because newer defenses have been constructed between them and the path of potential storm surge. I walls on the protected side of the Inner Harbor

lthough the HSDRRS involved hundreds of construc-

tion projects, several stand out because of their size and importance and because they represent new lines of defense in areas that previously were wide open to storm surge. The Inner Harbor Navigation Canal–Lake Borgne Surge Barrier features a concrete wall approximately 10,000 ft long and 26 ft high that stretches roughly north to south across an area known as the Golden Triangle Marsh. The wall runs from the LPV-111 levee section in New Orleans East and crosses the now-closed channel of the MRGO before connecting to the St. Bernard Parish levees. Prior to Katrina the Corps believed that New Orleans was more in danger of flooding from Lake Pontchartrain than from Lake Borgne, notes Park. This was largely because of the flooding in 1965 from Hurricane Betsy, which pushed surge from Lake Pontchartrain into the Gulf Intracoastal Waterway, the Inner Harbor Navigation Canal, St. Bernard Parish, and the Lower Ninth Ward, he explains. During Katrina, however, “surge came in from the Gulf of Mexico, through Lake Borgne, and into this marsh area,” producing up to 15.5 ft of surge and waves of more than 20 ft, explains Jason Ragolia, P.E., the Corps’s deputy resident engineer for the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier. The water “came through this area into the

city...and put 20 feet of surge over the existing floodwalls, causing scour behind the floodwalls that caused the walls to fail,” Ragolia says. A 4,000 ft long section of I walls and levees collapsed and caused devastating flooding in St. Bernard Parish and the Lower Ninth Ward. Newly constructed T walls now stand where the I walls failed, Ragolia says. Although a few I walls remain, they are “no longer in use because we fight the flood here,” he explains in referring to the new surge barrier. At its northern end, the barrier’s crenellated parapet wall features two openings that can be sealed off in the event of a storm. One is a 150 ft wide sector gate with two steel-framed segments shaped like pie slices in plan that swing open and closed; the other is a barge gate in the form of a large floating block of concrete 150 ft wide and 42 ft tall that can be swung closed on a large hinge and then flooded so that it will sink and lock into position, retaining a 26 ft tall barrier above the water. Roughly in the middle of the barrier, at a location called Bayou Bienvenue, is a 56 ft wide vertical lift gate structure roughly 80 ft tall that, when closed, also provides a 26 ft tall storm surge defense, says Ragolia. The sector gate provides navigation for vessels of shallow draft, the lift gate is designed primarily for recreational boats, and the barge gate serves primarily as an alternative navigation route when the sector gate is under maintenance. The surge barrier facility also features a concrete-framed “safe house” for its staff of roughly four operators; the house is 32 ft above water and has enough fuel in storage to power generators that can operate the system for about two weeks, notes Ragolia.

The towering, blocklike West Closure Complex pump building is approximately 80 ft tall and 480 ft long and has a total pumping capacity of more than 19,000 cfs.

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The barrier wall itself and the gates are supported by an A-frame system that consists of more than 1,200 vertical concrete piles, each 66 in. in diameter, and more than 600 batter piles, each 248 ft long and 36 in. in diameter. The vertical piles were driven into the marshland to a depth 130 ft below the water level, the inclined piles were driven in at an angle of 40 degrees to a depth of 190 ft, and the two types of piles were connected by concrete caps that were precast or cast in place, according to Ragolia and information in the paper “Design and Construction of the Lake Borgne Surge Barrier in Response to Hurricane Katrina,” by Scott R. Huntsman, Ph.D., P.E., G.E., D.GE, F.ASCE, an engineer for Shaw Environmental & Infrastructure Group, of Concord, California. Huntsman presented his paper at the 2011 Conference on Coastal Engineering Practice, which was organized by ASCE’s Coasts, Oceans, Ports, and Rivers Institute. Shaw Environmental was the design/build contractor for the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier, which was designed by a joint venture of Tetra Tech INCA, headquartered in Bellevue, Washington, and Ben C. Gerwick, Inc., of Oakland, California. The approximately $1.1-billion project was the largest design/build contract

ever let by the Corps. The design/build approach, says Ragolia, was essential to the scale and 15-month construction time frame of the barrier, which had to be in place by June 1, 2011, for the start of the hurricane season. “If we’d done the typical design/bid/build, we’d still be looking at a marsh,” he says. The Seabrook Floodgate Complex is located to the west and north of the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier. Designed to act in tandem with that barrier, the Seabrook complex was constructed at the Lake Pontchartrain end of the Inner Harbor Navigation Canal just south of a railroad bridge and a highway bridge. During Katrina the roughly 350 ft wide channel here was wholly open and experienced storm surge in two directions, notes Gilmore. First, Katrina pushed storm surge northward from Lake Borgne “through this channel into Lake Pontchartrain,” he explains. “Then Katrina got past us, a little north of us, then flipped around and the storm surge came back from north to south.” This doubling back contributed to flooding in the area the Corps refers to as New Orleans Metro, which encompasses the east bank of Orleans Parish west of the Inner Harbor Navigation Canal and a small portion of Jefferson Parish near the Mississippi River. Flooding was also experienced in New Orleans East, Gentilly, the Ninth Ward—which includes the Lower Ninth—and St. Bernard Parish. In the HSDRRS, the Lake Borgne surge barrier is designed to prevent an east–west storm surge, whereas the Seabrook complex is designed to prevent the north–south surge, Gilmore says. The Seabrook complex features a 95 ft wide sector gate with two steel-framed segments shaped like pie slices in plan that are flanked by two 50 ft tall vertical lift gates. When I visited the site toward the end of the 2012 hurricane season, the air was filled with the sound of birds courtesy of a recording designed to keep birds away so they do not roost on top of the structure, where nests would “cause maintenance nightmares,” Gilmore explains. New sections of T walls, each roughly 900 ft long, were also constructed to tie the floodgate complex into the existing levees that line the lake to the east and west. A new gate on land also was constructed to accommodate an existing railroad line that passes the Seabrook complex. When the new gates are closed, they and the new floodwalls provide a 16 ft tall barrier against storm surge; some of the preexisting floodwalls also were raised to match that 16 ft elevation. Although the sector gates are designed to accommodate boats on the Inner Harbor Navigation Canal, the nonnavigable lift gates are designed primarily to ensure that water flow in the channel remains the same as before the complex was constructed, Gilmore explains. Enormous angled rakes on the northern side of the West Closure Complex pump station slide up and down in front of the intake screens to clear away debris that might block the flow of water.

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A roughly 50 ft tall space within the West Closure Complex structure houses 11 giant pumps that weigh 70 tons apiece. The pumps were designed primarily to handle the heavy rainfalls that accompany storms.

To construct the Seabrook complex, the Corps first filled the existing scour holes in the channel, which were roughly 90 ft deep, with sand and then introduced piles, sheet piles, and cofferdams to dewater the site, Gilmore explains. The concrete structures that support the steel gates were then constructed, and the gates were brought to the site via barge. The bottom of the channel was lined with new rock for erosion control, and riprap was installed along the banks. Although the earthen levees around the floodgate complex will definitely need additional lifts periodically to ensure that the proper elevation is maintained, the concrete and steel gate structures cannot be raised easily. Thus, they were designed to provide the full 50-year design life right from the start. “So in 50 years, Seabrook should still provide that 100-year level of risk reduction,” Gilmore notes. The $165-million Seabrook complex was designed by the New Orleans office of Bioengineering Group and the international engineering firms Arcadis, based in Amsterdam, the Netherlands, and HNTB, based in New York City. St. Louis– based Alberici Constructors, Inc., served as the general contractor under a so-called early contractor involvement arrangement. In contracts of this type the general contractor provides certain preconstruction services concurrent with the design effort.  To the west of the Seabrook complex are the three outfall canals (17th Street, Orleans Avenue, and London Avenue) on Lake Pontchartrain for which permanent canal closures and pump stations are now under construction. Ground was bro-

ken in June, and the three facilities are expected to be completed by early 2017, explains Dan Bradley, an engineer and senior project manager for the Corps. The three outfall canals run south–north from internal pump stations within New Orleans. The canals are between 11,000 and 15,000 ft long and serve as critical elements in the city’s flood control system, especially for rainfall. Because the lake ends of the canals were unobstructed during Katrina, storm surge rushed into them, breaching the levees and floodwalls that lined the 17th Street and London Avenue canals and flooding much of the central portions of New Orleans. In recognition of the threat presented by the wide-open outfall canals, which have widths reaching 300 ft at their mouths, the Corps moved quickly in 2006 and 2007 to construct interim closure structures with gates and pumps that would block the mouths without impairing the drainage functions of the canals. Those interim facilities, however, had a limited life span and were not powerful enough to handle major hurricanes over the long term, Bradley says. They were also subject to extensive corrosion and required considerable maintenance. Robust and powerful permanent canal closures and pumps were therefore always envisioned to achieve the 100-year level of risk reduction at the canals, Bradley says. The $615-million design/build project is being designed and constructed by a joint venture known as PCCP Constructors, comprising Kiewit Louisiana Co., of Metairie, Louisiana; Traylor Bros., Inc., of Evansville, Indiana; and M.R. n o v em b e r 2 0 1 3

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Pittman Group, LLC, of St. Rose, Louisiana. Although still under design at press time, the new system is expected to feature permanent facilities with T walls, generator buildings, and gated structures that reach up to 18 ft above water— 2 ft higher than actually required to ensure that the facilities would have the “structural superiority” to withstand the expected storm surge, Bradley notes. The pumping capacities will vary, being 2,700 cfs at the Orleans Avenue Canal, 9,000 cfs at the London Avenue Canal, and 12,600 cfs at the 17th Street Canal, which means that the 17th Street facility could fill an Olympic-size swimming pool in just seven seconds, according to a July 2013 document prepared by the Corps entitled “Permanent Canal Closures & Pumps.” The new barriers will be closer to the lakefront than the interim facilities had been. Those facilities were kept back from the lake’s edge by as much as 1,000 ft as a safety measure so that storm surge waves would dissipate somewhat as they entered the canals, says Bradley. But the permanent closures and pump stations can be located right at the lakefront because they will be designed to better withstand both storm surge and wave impact, he says. The new facilities will also be designed to accommodate a disagreement that exists between the SLFPA–East and the Corps over how exactly water should be removed from the canals. The SLFPA–East is in favor of deepening the three canals and adapting them so that water would flow by gravity to the new drainage pump stations at Lake Pontchartrain, thus obviating the need for interior pump stations. This approach is referred to as Options 2/2a, explains Tim Doody, who serves as the SLFPA–East’s president. Through PCCP Constructors, the Corps is designing a system that will operate the new pump stations together with the existing interior pump stations; the Corps argues that it has the authority, but not the funding, from Congress to study Options 2/2a, explained Poché. The new facilities, however, are being designed with deeper foundations and intake basins than are currently required to accommodate Options 2/2a in case that approach is ever adopted and funded, notes Bradley. The superstructures are also being designed to be large enough to accommodate the larger motors and generators that would be necessary to operate the permanent facility pumps if the canals were ever deepened by as much as 15 ft, as envisioned under Options 2/2a, Bradley says. Unlike the surge barrier facilities at Lake Borgne and along the shore of Lake Pontchartrain, the new sector gate and pump station facility known as the Gulf Intracoastal Waterway–West Closure Complex was designed as a proactive rather than reactive element of the HSDRRS. Located on the southern side of the HSDRRS within the West Bank and Vicinity hydraulic unit, the West Closure Complex was constructed approximately half a mile south of the confluence of the Harvey Canal and Algiers Canal sections of the Gulf Intracoastal Waterway. Stretching east–west across the roughly 1,000 ft wide channel at this location, the West Closure Complex will use floodwalls, gates, and the pump station itself to block surge heading northward. The West Closure Complex, however, does not close off any of the storm surge routes that contributed to flooding during [ 6 2 ] C i v i l E n g i n e e r i n g n o v em b e r 2 0 1 3

Katrina. Instead, it draws on the lessons learned from Katrina to deal with potential flooding from future storms, says Tim Connell, the Corps’s project manager for the West Closure Complex. “Katrina basically brought an awareness that the whole area needed a higher level of risk reduction,” explains Connell. Moreover, if Katrina had struck the New Orleans region just 40 mi farther to the west, “it would have been a completely different story on this side of the river—this whole area would have been inundated,” Connell says. Although the West Closure Complex now provides a method of blocking storm surge from some 26 mi of levees and floodwalls along the Harvey Canal and Algiers Canal sections of the Gulf Intracoastal Waterway, the Mississippi River itself, just a few miles to the east, is not closed off in a similar way. But the riverine levees there, including the approximately 15 mi of colocated levees and floodwalls that are being raised as part of the HSDRRS, will provide the 100-year level of risk reduction in that area, Connell explains. Constructed at a cost of approximately $1 billion, the West Closure Complex features a 225 ft wide sector gate structure that is believed to be the largest in the United States, says Connell, as well as what has been called the world’s largest drainage pumping station. This towering, blocklike structure is approximately 80 ft tall and 480 ft long and features steel moment-resisting frames and 8 in. thick concrete panel walls, making it a “heavy, heavy concrete structure designed to withstand surge” and hurricane winds up to 140 mph, notes Connell. The pump station structure is founded on more than 1,100 steel pipe piles driven more than 160 ft into the soil and is topped by blinking navigation lights to warn away jets from a nearby naval air station. The sector gate segments weigh 750 tons each and are founded on a 10 ft thick concrete slab and more than 400 steel pipe piles. The pump station and the sector gates feature sheet-pile cutoff walls that reach depths of respectively 46 and 53 ft. Within the West Closure Complex, a roughly 50 ft tall space houses 11 giant pumps that weigh 70 tons apiece and have a total pumping capacity of more than 19,000 cfs. The pumping station was designed primarily to handle the heavy rainfalls that accompany storms now that this previously open end of the Gulf Intracoastal Waterway channel has been cut off by the sector gate system. Because of the surge potential, however, the facility has also been designed with a socalled nonsiphonic discharge, which means that the pumps will continue to operate at full capacity even as the level of water outside the complex rises as a result of storm surge. This feature sets the facility apart from the internal pumping stations in the canals elsewhere in the system, which lose capacity under the same conditions, Connell says. Enormous angled rakes on the northern side of the pump station slide up and down in front of the intake screens to clear away debris that might block the flow of water. The West Closure Complex was designed by Arcadis and constructed under an early contractor involvement arrangement by Gulf Intracoastal Constructors, a joint venture of Kiewit Corporation, of Omaha, Nebraska, and Traylor Bros. A two-level safe room within the West Closure Complex was constructed at an elevation of 26 ft above the normal

water level. Shielded by 16 in. thick reinforced-concrete walls and designed to withstand winds of up to 250 mph, the safe room can accommodate approximately 10 people, providing bunks and even showers. Outside the facility, large diesel tanks store enough fuel to operate the pumps and generators for the complex’s electrical systems for more than three days, making the complex completely self-sufficient. The at-grade, external site of the fuel tanks, however, is going to be improved, Connell adds. Although the fuel tanks are considered secure “for all normal events...we are looking at measures to further harden and further secure those tanks because they are the lifeblood of the station,” he says. During the fast-paced design of the pump station, the elevation of the tanks, which originally were to be higher to accommodate the most powerful storms, was lowered to expedite construction, Connell explains. “But now we’re taking measures to ensure their survivability in these extreme events,” he says. As part of the West Closure Complex project, the Algiers Canal section was also dredged, a nearby road was realigned, and large intake and discharge basins were dug out on respectively the northern and southern sides of the complex, says Connell. As a secondary line of defense against storm surge in the West Closure Complex region, a new floodwall also was constructed along the Harvey Canal section. Approximately 3.5 mi long, this new T-wall section is 14 ft high and is founded on 130 ft deep H-piles. During major storms, the Harvey Canal and Algiers Canal sections will now provide approximately 12.5 mi of detention basins for the interior pump stations, notes Connell. One of the most challenging projects in the West Closure Complex vicinity, however, involved a 4,200 ft long T-wall structure that was constructed on a narrow strip of land just 100 ft wide along the western side of the channel just north of the sector gate floodwall. The work site was restricted because it bordered the Bayou aux Carpes wetlands area, which is protected by the U.S. Environmental Protection Agency under section 404 (c) of the Clean Water Act. Unfortunately, during the risk analysis phase of the design of the HSDRRS, it was determined that a structure to block surge would be necessary in the Bayou aux Carpes, notes Connell. The Corps initially proposed the construction of a barrier directly across the area covered by section 404 (c) but encountered opposition from both the Environmental Protection Agency and local environmental groups, Connell notes. Working with the agency and other groups, however, the Corps developed a compromise solution: it would construct the floodwall in a 100 ft wide band along the edge of the 404 (c) area, and that floodwall would tie into other floodwalls outside of the protected wetlands, Connell explains. To ensure compliance with the 404 (c) restrictions, a fence

was erected to delineate the boundaries of the approved work site, and anyone working in that area had to be specially trained. Upon completing the training, each person would receive a 404 (c) sticker to place on his or her hard hat. The sticker designated that the person had been trained and thus could work in the designated area, and it also served as a reminder of the work site limitations, says Connell. “You understood that you didn’t go past the border fence for any reason—that’s the limit. You didn’t clear over there, you didn’t throw anything over there,” he explains. To the east of the West Closure Complex, the Corps constructed a series of levees and structures that form the Eastern Tie-In. The work included a new pump station, two 53 ft wide steel swing gates across a highway used for hurricane evacuations, and a swing gate for an adjoining railroad line. These projects tie the HSDRRS into the existing Hero Canal levees and the colocated levees on the Mississippi on the southeastern side of the new system. The corresponding Western TieIn was constructed at the southwestern end of the HSDRRS. It includes approximately 4.5 mi of new levees and floodwalls, a navigable closure structure across an area known as Bayou Verret, an elevated crossing at one highway, two railroad gates, and a second highway crossing before it connects to the Mississippi River levees near river mile 118. The Corps spent approximately $123 million repairing the existing pump stations in the New Orleans metropolitan region and an estimated $340 million in making those facilities stormproof. This work included the construction of new, elevated safe rooms, the hardening of the building structures, the installation of new generators and additional fuel capacity, the construction of perimeter floodwalls and berms, and other measures designed to prevent the conditions that forced many pump station operators to abandon their facilities during Katrina. Because evacuation is now seen as a major part of the new emphasis on risk reduction, the HSDRRS also features a new floodwall, as well as an elevated road and bridge over that floodwall, at the southern entrance to the Lake Pontchartrain Causeway Bridge. During storms the southern entrance to the bridge used to be closed off with sandbags that were piled up against the surrounding, taller I walls, explains Brett Herr, P.E., an engineer and branch chief in the Corps’s protection and restoration office. While this method seemed to prevent severe overtopping, even during Katrina, it was not considered adequate in the aftermath of that storm, says Herr. A floodgate had first been considered, he adds, but that idea was rejected because the causeway, which features twin parallel structures, each carrying two lanes across the lake, is a major evacuation route. Therefore the goal was to find a solution that would keep the causeway open as long as possible.

Shielded by 16 in. thick reinforced-concrete

walls and designed to withstand winds of up to 250 mph, the safe room can accommodate approximately 10 people, providing bunks and even showers.

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In the end, the answer involved not shutting the bridge at all. Instead, the causeway project involved the replacement of the original I walls with taller T walls in 40 ft sections and the construction of new, longer bridge ramps that pass over the new floodwall. The new ramps are supported on a series of concrete piers founded on piles driven to depths reaching 120 ft, explains Justin Smith, a project manager for the Corps. The causeway project was especially challenging because of the confined area on which the work was conducted and because the numerous underground utilities, some of which had to be relocated, were not well documented, says Herr. Furthermore, complicated detours and lane openings and closings were necessary to keep the causeway in operation throughout the construction phase, and a canopy arch bearing the name of the causeway had to be preserved and then reinstalled, along with new cameras to monitor the traffic flow, says Herr. Designed by Gulf Engineers & Consultants, of Baton Rouge, Louisiana, the $43-million causeway project was constructed by New Orleans–based Boh Bros. Construction Co., L.L.C.

D

uring the more than seven

Weakest Link in Post-Katrina Flood Defense.” Complicating matters, the bearings on several of the pumps at the West Closure Complex repeatedly cracked during the installation phase. The 4,000 ft levee that had to be raised was not a surprise, explained Poché, because it was in an area that was expected to “experience significant settlement in a relatively short period of time,” in part because it was constructed above an old slough. Thus, the Corps had always anticipated that the area would have to be monitored regularly and that additional lifts would be needed, he noted. The malfunctioning barge gate in the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier was finally closed successfully during the practice drills in May and has been opened and closed several times since then, Poché said. A special training program was implemented for the barge gate operators, he added, noting that each time “our crews operated the gate, they became more experienced and more familiar with its operation.” Although certain sensors and gauges failed during the recent drills, those faulty systems have been replaced, and none of these problems prevented the successful operation of the barge gate, Poché stressed. Robert A. Turner, Jr., P.E., CFM, M.ASCE, the SLFPA–East’s regional director, says that while he is now somewhat reassured about the barge gate, he still has concerns. In particular, he describes the barge gate as “an extremely complex mechanism” that relies on pumps, chains, chain drives, and other equipment. Since none of the equipment is automated, he says, it “needs constant human monitoring and intervention in order to effect a successful closure.” Heavily influenced by the wind and the currents in the channel, the barge gate is closed by an operator standing on the deck manipulating a pair of toggle switches controlling separate windlasses that function at different speeds, which means that “every time you close it, it’s a different experience,” Turner explains. Moreover, the Corps recommends that closure of the barge gate begin as much as 96 hours in advance of a storm— something that Turner says does not anticipate fast-moving events that come in quickly off the coast. In the case of the West Closure Complex pump bearings that failed during installation, the incident does not represent a problem so much as “a pretty incredible story of the determination of the contractors to meet the goal,” explains Connell. The goal was to have at least 8 of the 11 pumps operational by June 2011, the start of that year’s hurricane season, he notes. But as the contractors—M.R. Pittman Group, Gulf Intracoastal Constructors, and various subcontractors—started to test the pumps in April 2011, there was an indication that the shafts were overheating. The test was stopped, but not before an upper bearing had cracked. When the same thing happened on both the second and the third pump as they were tested, the

The malfunctioning barge gate in the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier was finally closed

years and more than 400 construction contracts that were involved in the creation of the new risk reduction system, the Corps faced numerous challenges, many of them highlighted in an article in the January 28, 2013, issue of Status Report Newsletter entitled “Construction of HSDRRS: A Sometimes Bumpy Road.” These bumps included the need to rework schedules to accommodate both the nesting season of egrets, a protected bird species, and the comings and goings of freight trains that operated throughout the construction phase. In addition to installing new track in the areas that were to receive railroad gates, the Corps had to cope with historic levels of Mississippi River flooding in 2011, the complexities of raising and widening a levee at the foot of the only runway at Louis Armstrong New Orleans International Airport that can accommodate instrument landings, and other complications. Additional problems included a series of back-and-forth legal challenges by the losing parties when contracts for certain projects were awarded. A 4,000 ft long section of a new earthen levee in the northeastern part of New Orleans “subsided so low it wouldn’t be able to withstand a storm surge caused by a socalled 100-year hurricane,” according to a July 16, 2013, article in the Times-Picayune entitled “Sinking Sections of Eastern New Orleans Hurricane Levee Prompt $1.3 Million Repair.” Moreover, the barge gate in the Inner Harbor Navigation Canal– Lake Borgne Surge Barrier was damaged in an early test. This problem and others caused considerable concern to officials in the SLFPA–East, according to a March 21, 2013, article in the Lens, the Web publication of a nonprofit group that focuses on the New Orleans area, entitled “Local Officials Losing Sleep over

successfully during the practice drills in May and has been opened and closed several times since then.

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The interim closure and pump station at the Orleans Canal and facilities at the 17th Street and London Avenue canals were kept back from the edge of Lake Pontchartrain so that the storm surge waves would dissipate somewhat before striking them.

contractors realized there was a definite problem, notes Connell. So they got together, disassembled the pumps within the station, removed all the shafts and gears, and ultimately determined that the tolerance on the gears was too tight. The tolerance had been tightened to avoid vibration issues, Connell notes, but it ended up being too tight, which caused friction. So the contractors remachined the bearings to accommodate additional tolerance, addressed some alignment issues that had come to light, and then reassembled the pumps. The 45-day period between April and June was originally intended to provide a cushion that would enable the contractors to resolve minor problems. Instead, it was used to solve a major problem so that on June 1, 2011, declares Connell, “we had 8 of the 11 pumps pumping water—a phenomenal event!”

W

hile overcoming these and other bumps, the con-

struction of the HSDRRS benefited from at least three critical developments, says Fleming. First and perhaps most important, the HSDRRS projects were not limited by the usual short-term, incremental funding that affects so many other major civil works efforts, he explains. Instead, from late 2005 through 2008 Congress passed seven supplemental appropriation bills that totaled more than $14 billion—roughly three times the Corps’s usual annual civil works budget, notes Fleming—to fund the new system for the New Orleans area. Other Corps projects, including the ongoing dredging of the Mississippi, still had to cope with the uncertainty of not knowing from year to year how much money would be available, but this was not the case with the HSDRRS program. Even as the budget battles in Washington raised the possibility of federal government

shutdowns over the years, Fleming knew he had the money he needed to proceed with the HSDRRS efforts. In addition to the certainty it afforded those working on the HSDRRS, the guaranteed funding enabled the Corps to benefit from economies of scale and award contracts more easily, Fleming says. “”We even got into the steel business,” he notes, explaining that the incremental approach would have meant awarding different contracts to various contractors, and those firms would then have had to “wait in line at steel mills” to obtain the necessary products, essentially competing with one another and driving up the cost of the steel or causing delays. But because the Corps knew how much money it had to work with, as well as what sort of steel it would need, “we bought a lot of steel in advance, put it in storage yards, and told the contractors not to worry about steel—just come get it from us,” Fleming says. It was the first time the Corps had tried such an approach, he says, and it definitely saved both time and money. A second major development that enabled the Corps to complete the HSDRRS faster than other civil works projects involved an expedited environmental review process to meet the requirements of the National Environmental Policy Act (NEPA). If the Corps had been required to follow the typical requirements set forth in that law, especially the completion of several detailed reports that analyzed the HSDRRS projects in their entirety, it would have taken “a significant amount of time,” perhaps as much as three years, before any construction could have begun, according to the final version of the Corps’s “Comprehensive Environmental Document: Greater New Orleans Area Hurricane and Storm Damage Risk Reduction System,” which was published in May. Typically, the Corps would have had to prepare a n o v em b e r 2 0 1 3

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separate environmental impact statement for each of the more than 400 projects within the HSDRRS, explains Fleming. But if that had been the case “we’d still be doing [environmental impact statements] at this point,” he says. Instead, the Corps was allowed to use so-called emergency alternative arrangements approved by the White House’s Council on Environmental Quality. “We still had to do the full NEPA process,” says Fleming, “still had to disclose all of the impacts to the environment, to people, to air, traffic, pollution, et cetera.” And there were still public meetings and public comment periods, he adds. But the use of the alternative arrangements did permit the environmental evaluation “of numerous smaller construction projects as the engineering design for each segment was developed, rather than waiting to complete the NEPA evaluation once the designs for the entire system were complete,” explained the final version of the “Comprehensive Environmental Document: Greater New Orleans Area Hurricane and Storm Damage Risk Reduction System.” The alternative arrangements cut through a lot of red tape and allowed the Corps to start construction on the HSDRRS projects much earlier than is typically the case, Fleming says. Fleming also praised the various state and local organizations in southeastern Louisiana that passed new laws and implemented other measures that enabled the Corps to acquire the land needed for the HSDRRS in an expedited fashion. Indeed, he considers this the third major development that enabled the Corps to complete the new system so quickly.

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he new system underwent a baptism by storm surge last year when Hurricane Isaac, a large, slow-moving storm of low intensity, stalled over the region for roughly 45 hours. In preparation, all of the major new features of the HSDRRS were either closed or utilized for the first time in an actual storm, including the first closure of the sector gates at the West Closure Complex—where the site’s massive pumps also were put into action—the Seabrook Floodgate Complex, and the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier. (The barrier’s barge gate was already in its closed position, but it was still under construction at the time.) Some 300 of the more than 500 openings in the perimeter system that provide access for railroads and motor vehicles and serve other purposes as well were closed for Isaac; the remaining openings along the Mississippi did not have to close because the water levels there were not considered high enough to create a storm surge risk, as explained by Stack and recounted in the Civil Engineering online article “New Orleans’ Defenses Weathered Isaac ‘Very Well.’” Temporary closures also had to be erected in several locations at which construction work was still under way, including two sites that had to be kept open as long as possible because, as Stack explained and as was reported in the above article, once closed they would have blocked major evacuation routes. During Isaac there were several locations, especially at the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier, at which “had we not had this system in place, the old system would have been overtopped,” says Fleming. Senator David Vitter (R-Louisiana) concurs, noting in written responses to

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Civil Engineering’s questions that even if Isaac “didn’t fully test the system,” the new HSDRRS defenses definitely prevented significant flooding within its perimeter. But Vitter also cited the “tragic flooding” that occurred in areas outside of the HSDRRS and joined others in asking whether the new system caused that flooding, especially because some of the neighborhoods had not experienced flooding during Katrina or Rita. The result was a reexamination of the new system by the Corps and a call from Vitter for an independent peer review. The Corps’s analysis, Hurricane Isaac with and without 2012 100-Year HSDRRS Evaluation, was released in February of this year and peer-reviewed by Battelle Memorial Institute, of Columbus, Ohio, and the Water Institute of the Gulf, based in Baton Rouge, Louisiana. Although Isaac’s “nearly 45 hour duration of tropical force winds, track, size and slow forward motion, and considerable rainfall resulted in significant volume of water delivered onshore,” the Corps concluded that “the HSDRRS could not have significantly influenced inundation at communities external to the system.” Instead, the flooding of communities outside of the HSDRRS “was caused by intense and long duration storm surge due to the long duration of tropical force winds, which in some cases were aggravated by extreme local rainfall.” In response, Vitter emphasized that there is “more important work to do” with regard to flood protection in southeastern Louisiana. Many of the areas flooded during Isaac “have little to no flood protection,” Vitter stated, adding that “many of these areas were promised protection through other Army Corps projects” that have since been “dramatically slowed or cancelled.” Stressing “the need for critical flood protection in areas outside the 100-year system,” Vitter called on the Corps to “expedite ongoing projects to protect those areas that were heavily flooded because of Isaac.” Vitter has also called for reforms to the Corps designed to eliminate “unnecessary bureaucracy” and cost overruns, reduce red tape, and “streamline and complete” other Corps projects in the region. The senator’s proposed reforms are included in the Water Resources Development Act of 2013, which passed the Senate in May and at press time was still being considered by the House.

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ike Vitter, a number of local stakeholders, as well as

other engineers who have studied the new system, have both praise and misgivings regarding the HSDRRS. For example, Thomas L. Jackson, P.E., D.WRE, Pres.03.ASCE, a former president of the SLFPA–East and a regular member of that body until the summer of 2012, asks, “When you look at the system that was built around New Orleans, are we better off today than we were pre-Katrina? Absolutely— no doubt about it!” However, he also asks, “Do I have differences about some of the things that were done? Yes, I do!” Jackson notes that the SLFPA–East “fought tooth and nail on a number of issues” with the Corps, including the decision by the Corps to use H-piles that had not been coated with a corrosion-resistant paint in constructing the T walls in St. Bernard Parish; instead, the Corps used larger piles than necessary “to add a level of thickness to act as the corrosion

surface,” according to a written response to a follow-up question submitted by Civil Engineering to the Corps’s Gilmore. The use of additional steel thickness “is a widely accepted practice that is used all over the world,” especially by the marine industry, Gilmore explained. Both Louisiana’s Coastal Protection and Restoration Authority and the Corps have been conducting corrosion tests. Although Gilmore noted that the authority’s tests are reported to have revealed “excessive corrosion,” the Corps’s tests, which included excavations to expose the H-piles for a visual inspection and instrument measurements, were still being evaluated at press time. Jackson also points to the SLFPA–East’s disagreement with the Corps over the Options 2/2a gravity flow proposal for the three outfall canals on Lake Pontchartrain. The Corps warns that this approach might take up to 10 years to complete and involve “significant construction impacts to the residents” and that large expanses of real estate would have to be acquired, noted Poché. John M. Barry, a New Orleans– based writer and the vice president of the SLFPA–East, adds two more major areas of contention: the planned armoring of the levees and a study sponsored by the SLFPA–East suggesting that the Corps’s analysis of the hurricane surge hazards for the New Orleans region might already be outdated. According to the minutes of a May 16, 2013, meeting, the SLFPA–East is concerned that the Corps “is reviewing revised (reduced) overtopping rates which could significantly reduce the amount of armoring anticipated and planned in New Orleans East and along the lakefront in Orleans and Jefferson parishes.” The authority is also worried that the Corps might eliminate “the use of a risk analysis in determining how much of the HSDRRS should be armored for resiliency.” As a result, the SLFPA–East unanimously voted to request that an independent external peer review group “be assembled to examine and comment on both the sufficiency of overtopping rate calculations and the necessity for making risk assessment an integral part of determining the armoring footprint,” according to the May 16 resolution. The SLFPA–East is particularly concerned about armoring because the Corps did not initially plan to armor most of the authority’s levees with anything other than regular grass, notes Turner. The SLFPA–East does not consider grass alone to be adequate armoring, he says. But at press time he was encouraged that the Corps was reevaluating that plan and seeking additional input from the authority. Although no one from the SLFPA–West responded to Civil Engineering’s requests for an interview, officials from that authority have suggested that the Corps consider either raising the levees in the west-bank projects several feet now rather

than installing the turf mat armoring or delaying the installation of the armoring until after the levees have been raised anyway because of local subsidence, according to an August 16, 2013, article in the Times-Picayune. Barry also points to a recent study, Hurricane Surge Hazard Analysis: The State of the Practice and Recent Applications for Southeast Louisiana, which was prepared for the SLFPA–East by Bob Jacobsen, P.E., M.ASCE, a private engineering consultant in Baton Rouge, Louisiana, and the new president of ASCE’s Louisiana Section. According to Jacobsen’s report, between 2005 and 2009 the Corps conducted “a ground-breaking analysis” of the 100-year surge hazard in support of the regional Federal Emergency Management Agency flood insurance study and the HSDRRS design. This analysis “employed considerable professional, academic, and other technical resources and greatly advanced the state of scientific knowledge and engineering practice,” Jacobsen wrote. However, as Jacobsen told me, “surge hazard analysis methodologies are evolving rapidly.” For example, it is now recognized that the 100-year hazard must also account for the probabilities of “large, slow-moving, lowintensity storms,” in addition to those associated with major hurricanes, Jacobsen said. Moreover, exponential increases in computational power mean that engineers can now greatly expand both the number of storms and the hydrodynamic model resolution to better capture surge responses. Jacobsen’s report indicated that the Corps’s storm set of 152 events and the computer modeling can now be improved to better characterize important surge effects in such large, sheltered water bodies as Lake Pontchartrain. Such analyses are critical to estimating 500year storm surges. Richard A. Luettich, Jr., Sc.D., a professor of marine sciences at the University of North Carolina, the director of the Institute of Marine Sciences there, and a recent member of the SLFPA–East, stresses that “a system of this significance and magnitude should be reviewed on a periodic basis.” Every 5 years would be good, he says, but at the very least a system such as the HSDRRS should be examined every 10 years “to simply reevaluate, based on current knowledge and practice, whether it continues to provide the protection that we thought it did when it was designed.” Luettich, who also served on National Academy of Engineering and National Research Council teams that examined the response of the hurricane defenses during Katrina and the design of the new HSDrRS, would like to see the development of sensors to monitor the integrity of the new HSDRRS over time. There are a few such sensors in place, he notes, but he recommends the use of many more to measure ground or slope movement of the levees, settlement, seepage, gaps, or “any of those things (Continued on Page 83)

Exponential increases

in computational power mean that engineers can now greatly expand both the number of storms and the hydrodynamic model resolution to better capture surge responses.

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Defending New Orleans (Continued from Page 67) that may be occurring on a very slow and routine basis that have the potential to undermine the performance of the system when impacted by a major storm event,” he explains. The long-term maintenance of the HSDrRS “presents a tremendous engineering challenge,” Luettich notes, “but also a tremendous engineering opportunity to really develop a system that can monitor the performance and the robustness of the system as it goes forward and gets ready to meet the next major event.”

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lthough the Corps has started to hand over control of certain aspects of the HSDRRS to the local authorities that will be responsible for the operation and maintenance of the new system, this has mainly involved sections of levees and floodwalls so far, notes Turner. Most of the large infrastructure facilities, especially the West Closure Complex and the Inner Harbor Navigation Canal–Lake Borgne Surge Barrier, are still being operated by the Corps because they are only about 99 percent complete rather than 100 percent, explained Poché. These facilities will probably be turned over to the local authorities by the end of the year, says Turner, who commends the Corps for its commitment not to turn over any of these major facilities in the midst of the current hurricane season. Of course, once such organizations as the SLFPA–East do assume responsibility for the HSDRRS features within their jurisdictions, they will have to find a way to pay for the new defenses year after year. Doody estimates that operating and maintaining the risk reduction facilities will cost the SLFPA– East roughly $16 million annually and that perhaps another $20 million annually will have to be expended over the next several decades to help pay the local share of the construction cost. Both Doody and Barry contend that many of the hurricane defenses constructed in the New Orleans region, including aspects of the HSDRRS, involve projects that provide benefits to the rest of the United States, for example, protecting navigation channels for com-

merce throughout the region. Yet the considering whether people should be local residents end up bearing the costs living in certain parts of New Orleans. that arise both in operating and main- As O’Rourke notes in voicing a sentitaining the systems and in recovering ment expressed by many, “Nature’s gofrom the losses that are sustained when ing to control, ultimately, and bring the levees and floodwalls along those up some event that exceeds the capacity of the system.” At that point, he navigation routes fail, they explain. concludes, “we’ll have to A prime example insee how the human side volves the gated structures ce responds.” that have been constructed along the Gulf Intracoastal Robert L. Reid is the senior ediWaterway. “The Corps says tor of Civil Engineering. that is flood protection,” Doody muses, “but we say it’s a hole in our flood protecReid Project Credits tion.” Such systems should, Hurricane and Storm Damlike the Corps-operated locks along the Mississippi, be owned age Risk Reduction System owner and operated by the Corps, Doody says. and local sponsor: Coastal Protection The costs of operating and maintain- and Restoration Authority of Louisiing a large system like the HSDRRS be- ana Oversight of Hurricane and Storm come “a kind of unfunded mandate” for Damage Risk Reduction System dethe local authorities, notes Thomas D. sign and construction: U.S. Army O’Rourke, Ph.D., M.ASCE, who holds Corps of Engineers and numerous conthe Thomas R. Briggs Professorship tractors Inner Harbor Navigation Cain Engineering at Cornell University nal–Lake Borgne Surge Barrier designand also served on the National Acad- er: Joint venture of Tetra Tech INCA, emy of Engineering and National Re- Bellevue, Washington, and Ben C. Gersearch Council team that produced the wick, Inc., Oakland, California Inner 2009 report. Levees, in particular, are a Harbor Navigation Canal–Lake Borgne “wasting asset” in the New Orleans re- Surge Barrier design/build contractor: gion because of the ongoing local settle- Shaw Environmental & Infrastructure ment, regional subsidence, and erosion Group, Concord, California Seabrook and thus require expensive maintenance Floodgate Complex designer: Bioenand improvements over time, O’Rourke gineering Group, New Orleans; Arsays. New Orleans, which still has not cadis, Amsterdam, the Netherlands; returned to its pre-Katrina population and HNTB, New York City Seabrook levels, faces the additional challenge of Floodgate Complex contractor: Alfinding the tax base to fund the costs of berici Constructors, Inc., St. Louis Gulf such maintenance, he adds. O’Rourke Intracoastal Waterway–West Closure predicts that some sort of financial assis- Complex design: Arcadis, Amstertance from the state or federal govern- dam, the Netherlands Gulf Intracoastal Waterway–West Closure Complex ment may be necessary. O’Rourke praises the Corps’s efforts contractor: Gulf Intracoastal Conin the construction of the HSDRRS, but structors—a joint venture of Kiewit he also stresses that “we have residual Corporation, Omaha, Nebraska, and risks here that we just don’t fully un- Traylor Bros., Inc., Evansville, Indiana derstand...so I always call this a work Outfall canal permanent closure and pump station design/build contractor: in progress.” Indeed, many of the experts inter- PCCP Constructors—a joint venture of viewed for this special report say that Kiewit Louisiana Co., Metairie, Louisimuch work remains to be done to im- ana; Traylor Bros., Inc., Evansville, Inprove hurricane defenses in the entire diana; and M.R. Pittman Group, LLC, southeastern Louisiana region. The ef- St. Rose, Louisiana Causeway project forts will include restoring wetlands designer: Gulf Engineers & Consuland barrier islands, elevating houses tants, Baton Rouge, Louisiana Causeand other structures, adopting new ap- way project contractor: Boh Bros. proaches to land use planning, and even Construction Co., L.L.C., New Orleans n o v em b e r 2 0 1 3

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