This is the third of a series about the 5 finalists for the ASCE’s Outstanding Civil Engineering Achievement (OCEA) awards. Established in 1960, the OCEA Award recognizes a project that makes a significant contribution to both the civil engineering profession and society as a whole. The winner of this year’s OCEA award will be announced at ASCE’s Outstanding Projects And Leaders (OPAL) Gala, March 20, at the Renaissance Arlington Capital View Hotel in Arlington, Virginia. Today, read about the Inner Harbor Navigation Canal (IHNC) Surge Barrier. The project also was featured in Civil Engineering magazine.
In August 2005, an 18-foot storm surge, which produced 7-foot waves caused by Hurricane Katrina, overpowered the Mississippi River–Gulf Outlet and Gulf Intercoastal Waterway, ultimately causing the collapse of a 4,000-foot-long section of the floodwall along Louisiana’s Inner Harbor Navigation Canal (IHNC). This and other levee and floodwall breaches brought nearly 15 feet of floodwaters into many southeastern Louisiana neighborhoods – covering a 90,000-mile area. This catastrophic failure caused a public loss of confidence in the city of New Orleans hurricane and flood control system.
After the hurricane, the U.S. Congress authorized the U.S. Army Corps of Engineers to design and construct a Storm Damage Risk Reduction System (SDRRS) which would defend against the effects of a future storm-surge event. The largest civil works design-build project in the Corps’ history, the $1.35 billion Inner Harbor Navigation Canal (IHNC) Surge Barrier is designed to reduce risk for some of southeast Louisiana’s more vulnerable areas from a future storm surge generated from Lake Borgne and the Gulf of Mexico. Nearly 2 miles long and 26 feet high, the project was completed in the spring of 2011 and helps keep the region a vital and safe commercial destination.
ASCE News Associate Editor Doug Scott interviewed Christopher E. Gilmore, P.E., senior project manager at U.S. Army Corps of Engineers in the greater New Orleans area.
1. What is the most innovative or creative aspect of your project?
The wall design, consisting of batter-pile-braced soldier piling and constructed on the water in a challenging geotechnical regime, is the most innovative part of the project. All components were sized for ease of erection in a maritime environment, considering capacity of lifting and pile driving equipment, as well as the ability of industry to fabricate and deliver “modular” components from land-based plants to the open-water construction area in Lake Borgne. U.S. industry was challenged given the number of large lift cranes used in the operation [and in use throughout the New Orleans Hurricane and Storm Damage Risk Reduction System (HSDRRS)] and the fact that only 5 of the largest-diameter pile driving hammers required for the soldier pile installation were available in the U.S. Three were actively used on the IHNC, with 2 in operation at any given time and 1 as a spare. Another innovative and creative aspect of the IHNC Surge Barrier project was the overtopping analysis. The surge barrier is designed to allow significant wave overtopping. The IHNC Surge Barrier connects 2 existing levee systems. With construction of the surge barrier, the existing levees west of the project or on the protected side become a secondary risk reduction system. The project was able to capitalize on this configuration and use the storage capacity behind the barrier effectively. Approximately 226.5 million cubic feet (the equivalent of 2,500 Olympic swimming pools) is reserved to accommodate the overtopping volume at the design conditions. In addition, to ensure that the overtopping volume was below the allowable limit while minimizing loads on the surge barrier wall, the designer proposed a crenulated parapet wall. Use of the crenulated wall minimized design loads by allowing the wall to be designed with water to the top of the crenel or lower elevation while the merlon minimized the quantity of water overtopping the wall. This allowed for optimization of pile length, which was particularly significant for the posttensioned precast concert piles.
2. What was the biggest challenge?
Meeting the organizational goal to provide the 100-year level of risk reduction by the start of the 2011 hurricane season was the single biggest challenge. From the outset in 2007, every aspect of the project was fundamentally affected by this immovable commitment to the citizens of New Orleans. The standard Corps organizational and operational processes in place at the time would have required 10 to 15 years to design, permit, and construct a project of this magnitude; the schedule allowed 4 years. This drove the Corps to streamline analysis and decision-making while maintaining strict accountability. It drove the design team to develop a solution that was adjustable to evolving design criteria and specifically tailored to support fast-track construction. Another challenge was the unpredictable marine environment and the time-constrained construction schedule, which necessitated 24-hour-per-day operations on open water. Given the potential for storm and lightning conditions to occur almost without warning, special emphasis was placed on lightning detection and warning systems so that workers could take the necessary sheltering and stand-down actions during storm events. Marshaling a 500-600 person workforce on an open-water construction site required careful logistics planning and sequencing of work operations so that the labor force could access and egress the project reliably and safely during the 24-hour operational cycle (2-10 hour work shifts and a 4-hour maintenance shift). Another significant challenge associated with the construction of the project was the need to specify and maintain close tolerances for the surge barrier’s large components (vertical piles, batter piles, closure piles, precast concrete caps, etc.), which were to be constructed on the water and in challenging soil conditions. Close tolerances were vital to helping ensure “fit-up” of the various barrier wall components.
3. Did your project have any technical issues that you had to overcome? If so, what were they and how did you overcome them?
The most significant technical issue was to initiate a fast-track production schedule for the 5.5-foot-diameter prestressed soldier pile, while pile load testing and overall wall height decisions were still being finalized. The modular nature of the prestressed pile (8 or 16 feet in length) allowed the fabricators to commence casting of the 10,000-plus segments in advance of the final decisions concerning overall pile length. Once final decisions were reached on the ultimate load and wall height, the segments were strung together and prestressed in their final as-constructed lengths and barged to the worksite from the precast plants that performed the fabrication. Additionally, the steel batter piles required precise placement templates and erection to assure accuracy of location in respect to the precast wall caps, which were used to tie the vertical pile and batter pile together into a rigid structure to withstand design storms. A very large (3-story) erection jig was constructed to align and place the batter piles at the appropriate configuration. The jig effectively maintained correct angle orientation and position with respect to the finished structure, ultimately assuring project performance. Another significant technical issue that had to be overcome was the accurate prediction of channel characteristics and vessel behavior. The presence of the surge barrier wall across the IHNC was predicted to change the characteristics of the channel flow, and as such, the manner in which large commercial vessels and recreational craft would navigate the area. The challenge for the project team was to accurately predict these changes.
4. What time and budget challenges did your project have and what did you do to overcome them?
The 4-year window to design, execute environmental clearances, acquire permits, and construct the project did not fit any traditional schedule timeframes. To maximize the time available, the Corps awarded a cost-reimbursable design-build contract based on 5% design in order to immediately begin fast-tracking activities. However, this significantly increased cost risk and schedule risk, as design evolution and price escalation could not be accurately quantified or contained. Further, the impact of cost growth was not only a risk to the project but also to the entire integrated risk reduction system for the greater New Orleans area, as funding had been determined by Congress. To overcome these challenges, a highly specialized technical team was assembled and integrated to manage the unique risks associated with cost-reimbursable contracting and design-build delivery, and an award fee was used to motivate the contractor and ensure that all project objectives were aligned. To further maximize the time available, major portions of work were subcontracted based on 30% design, and when design evolution led to cost growth, value engineering teams identified alternative options to achieve savings in excess of $250 million. Given the schedule and budget constraints imposed on the project, the design-build procurement approach identified by the USACE allowed for the creativity of the designers and constructors to collaborate from the outset. This collaboration led to the identification of specific project features and characteristics that helped to lower risk and deliver the technical objectives on time and within budget. This was accomplished through an intensive study conducted to establish the “most feasible” barrier wall and gate systems for the Gulf Intercoastal Waterway (GIWW) and Bayou Bienvenue floodgates.
5. Sustainability is one of the 3 strategic initiatives here at ASCE. Describe how your project adheres to being sustainable.
Environmental, social, and economic sustainability were of major concern throughout the design and construction of the IHNC Surge Barrier. The project delivery team investigated various project alternatives in compliance with the National Environmental Policy Act and consciously incorporated systems and techniques to help minimize environmental impact and deliver a product that provided substantial storm-risk reduction along with additional social and economic benefits for the greater New Orleans area.
Next, read about the Taizhou Bridge