Edward E. Belk Jr., U.S. Army Corps of Engineers
Belk provided an overview of the Army Corps of Engineers,1 its strategy for asset management, and its use of emerging technologies. He described the Corps’ three mission sets: (1) military (with a presence in more than 60 countries); (2) civil works (delivery, operation, and maintenance of civil infrastructure); and (3) engineering and research development (exploiting technology and emerging state of the art in both military and civil works missions).
Belk explained that there are 9 civil works divisions in the United States, containing 43 districts, organized around the nation’s watersheds. He emphasized that the Corps is different from many other federal agencies in that it does not receive money for people or for supplies; it instead receives funding for projects. Belk introduced the “giant math problem” confronting the infrastructure investment in the Corps: based on an estimate from the World Economic Council, approximately $7 trillion is expected to be needed for infrastructure between 2016 and 2030 to sustain current levels of economic activity and quality of life. Yet the United States is not currently prepared, through traditional public financing mechanisms, to make such investments. Among several initiatives to combat this problem, the Corps is
considering the use of public-private partnerships in the hopes that private sector capital can be leveraged to deliver public infrastructure.
The Corps owns and/or operates more than 3,000 assets around the United States, including locks, dams, and hydro power (of which the Corps produces 25 percent for the nation). Its primary mission revolves around the ease of having reliable navigation channels to move the nation’s goods, which can impact both national security and economic security. As the United States has more inland waterways than the rest of the world combined, it is imperative, according to Belk, that these channels are dependable. Part of the Corps’ mission also includes flood risk management, water-based recreation, and ecosystem restoration. He added that recapitalization is also a challenge for the Corps—systems built in the 1940s age and require maintenance to continue to perform appropriately. The American Society of Civil Engineers (ASCE) noted a deficit of $140 billion in water sector investments between 2016 and 2020; adding to that is the fact that the $76 billion in authorized Corps projects that have yet to be constructed is relying on a much smaller $4.6 billion annual Civil Works infrastructure budget, Belk explained. The National Research Council also conducted a study on investment for large public works infrastructure; its recommendations for investment were also fiscally impossible.
The Corps’ response was to develop an infrastructure strategy that includes the following:
- Asset management. Make risk-informed decisions about investments based upon understanding the conditions and consequences of failure of assets (see Figure 4.1).
- Life cycle portfolio management. Look at servicing the portfolio in terms of systems and the interrelationships and interoperability across those systems.
- Alternative financing. Focus on investments that will achieve an outcome over time.
Belk then described the Corps’ strategy for maintenance management, which includes the following phases: critical asset visibility, noncritical asset visibility, and required minimum maintenance data. The purpose of the strategy is to make better investment decisions across the portfolio through the development of a consistent, transparent, and repeatable process across the many subordinate commands in the Corps. He continued that the Corps is currently making modest investments to decrease some risk and increase the service life of those assets; the Corps would ideally like to focus more on modernization (based on current conditions, economic drivers, and performance outputs) in the future, if investments are available (see Figure 4.2). The current budget climate forces the Corps to mainly focus on sustaining conditions. Luckily, assets that are in excellent or good condition
dominate, as opposed to assets that are in poor condition or have already failed. Belk stressed that asset management and investment strategy needs to be based on choices made ahead of time instead of choices made after an asset fails. The best strategy, according to Belk, is to take a risk-informed systems approach and apply funds to decrease the most risk across a portfolio. He added that the Corps is also improving its modeling capabilities and use of portfolio analytics, which helps to make more informed decisions and to optimize investments. He noted that a culture change (i.e., a focus on value of investment over cost) would also encourage better decision making.
Belk next discussed the technology that the Corps is leveraging with its engineering and research development center to reduce cost and to extend the life of infrastructure, especially the application of more durable composite materials in the navigation sector. These projects have saved approximately $3 million in initial repair costs and $50 million in life cycle costs. The Corps has also engaged in more cost-effective nondestructive testing for tension and failure, as well as remote sensing for the quick and safe inspection of structures. Belk added that eNavigation can be used for damage avoidance between vessels and locks and dams, for instance, and structural health monitoring makes an assessment (based on appropriate analyses of measured data) about the ability of the system to perform successfully. Structural health monitoring can then be combined with probabilistic future loading and failure mode models to forecast the remaining useful life of an asset. He also described the combination of sensors and structural modeling used to predict conditions and then assess those conditions in real time so as to try to predict and prevent failures instead of responding to them.
In response to a question from General Paul Kern, The Cohen Group, Belk clarified that the Civil Works budget is not part of the Department of Defense (DoD) budget. Jesus de la Garza, Virginia Polytechnic Institute and State University (Virginia Tech), asked what kinds of projects might benefit from public-private partnerships. Belk first noted that while public-private partnerships are used regularly in various countries, the United States does not use them as often—initially, there was not a need for them given the municipal bond market’s investment in the water infrastructure, and the nation’s 2- to 4-year political cycle does not correspond to the 20- to 30-year cycle of a public-private partnership. However, the advantages of the public-private partnership, he continued, include the ability to extend service life and sustain performance of existing assets as well as to accelerate delivery and accrual of project benefits to new infrastructure. While the federal government carefully considers the use of money from the private sector to deliver public works (instead of the use of federal government funds with nearly
no interest), Belk emphasized that the cost savings of the decreased construction window that comes from a partnership can offset the private sector cost of capital. He added that it can be difficult to establish such partnerships at the federal level within existing laws. Other challenges include a lack of revenue generation for reinvestment in an asset—all revenue from assets currently goes back to the Department of the Treasury. Belk suggested that opportunities may exist for more policy and legislative assistance so that the federal agencies in the water sector can better participate in public-private partnerships.
Haydn Wadley, University of Virginia, asked how the Corps plans to respond to concerns about climate change. Belk responded that every recommendation and investment decision that the Corps makes in its planning for new infrastructure (and operations of current infrastructure) considers and incorporates climate change. He added that the Corps is also making significant investments in engineering research and development to better understand and respond to climate change issues. Peter Matthews, USTRANSCOM, noted that financial incentives are often misaligned, and he asked whether the ability of infrastructure to generate income is taken into account when investment decisions are made. Belk said that this is not taken into account, and he added that of the $5 billion that is invested each year across the portfolio, approximately $16 billion in revenue goes back to the Department of the Treasury. The Corps has discussed the concept of capturing such revenue to reinvest in their assets, although the Corps is allowed to compete with all federal agencies for such revenue as part of the annual budget process. Belk hopes to find a way to continue to have this discussion with decision makers before problems with infrastructure arise. Because 70 percent of the country’s current population was born after 1960, it is a challenge to describe the value proposition of infrastructure (and infrastructure investment) and what the lack of it looks like to people who have never been without something such as the interstate, for example.
UNRAVELING STRUCTURAL INFRASOUND: UNDERSTANDING THE SCIENCE FOR PERSISTENT REMOTE MONITORING OF CRITICAL INFRASTRUCTURE
Mihan McKenna, U.S. Army Engineer Research and Development Center
McKenna described her focus on force projection and maneuver—in other words, the ability to transport equipment to and within various mission-critical locations. The programs she discussed during her presentation are referred to as “Mihan’s Singing Bridges”—she proposed using geophysical knowledge to solve structural engineering’s remote sensing problems.
McKenna explained that an aerial satellite image of a structure captures only the appearance of that structure, as opposed to its behavior, during one particular
moment in time. During route reconnaissance missions, a structure is often found to be in a very different condition than what appeared in the satellite image. McKenna shared an anecdote of troops in Iraq who tried to cross a bridge based upon its stable appearance in a satellite image taken just 1 hour previously; yet when they arrived, the bridge was not there, and so the operation was compromised. The Remote Assessment of Critical Infrastructure program begins to address this problem with “persistent standoff assessment and monitoring for the purpose of stability analysis, load ratings, structural health monitoring, and failure phenomenon analysis in both military and civil works applications utilizing infrasound,” according to McKenna. She defined infrasound as a low-frequency, subaudible sound transmitted over long distance and typically within the range of 0.1 to 20 Hz. These acoustics are created by volcanoes, earthquakes, explosions, surf, missiles, rockets, urban noise, and large infrastructure, and one must be able to identify signals of infrastructure out of this background noise. McKenna noted that most military-critical infrastructure used for stability operations, projection, or maneuver is large enough that the fundamental modes of motion of those structures are in the infrasound passband. She added that infrastructure is “singing” continuously, although at different modes depending on which modes are excited. Signal processing is then used to find the signals that “twinkle,” McKenna explained.
The Singing Bridges project has adopted some of the technologies used for remote monitoring of nuclear explosions; it enables the setup of a fully functional subaudible acoustic array in less than 1 hour, which can then be fed into any Army visualization platform. The project’s sensor system involved low-frequency acoustics, audible acoustics, and seismics, and it assessed meta effects that occur on the sensors in the ground (i.e., seismic-infrasound-meteorological-acoustic arrays). McKenna emphasized that these sensors work in real time (with only a half-second delay), which is crucial for troops conducting structural assessments in theater.
McKenna explained that the goal of incorporating geophysical techniques (including infrasound) in combination with structural engineering is to shift the mind-set away from how something appears to how something behaves and adopt persistent monitoring for instances when a structure cannot be assessed physically. This allows one to understand what the structure is doing as well as how it moves and breathes. This holistic understanding of a structure is particularly relevant for capacity, condition, and military route planning, according to McKenna.
She noted that infrasound can reveal material components, placement mechanisms, forensic events for explosions, and fire heights, for example. Infrasound cannot reveal crack propagation or weather patterns; however, microcracks are not necessarily important for military planning unless they have fundamentally undone the functional behavior of a bridge. McKenna’s program has expanded during the past decade to look at different types of structures, environments, and propagation regimes. Listening to sonic maps of infrastructure has the potential to
reduce costs associated with inspections, increase efficiency, and improve resource prioritization.
The program is also focused on dam structural health monitoring, change management techniques, urban monitoring, and scour/damage detection. Scour is the number one reason that bridges fall down; instead of inspecting bridges every 3 years for this problem, real-time monitoring from a distance of 5 to 10 kilometers away can be implemented without having to add any device to the structure itself that could be damaged or stolen. Within the next 5 years, McKenna hopes to have this technology transitioned to military end users as part of a visualization platform that takes in live data from the seismic-infrasound-meteorological-acoustic array and its general geographic area, which could better reveal the conditions of various structures.
McKenna concluded by describing the Remote Assessment of Infrastructure for Ensured Maneuver program, which will occur during the next 5 years. She emphasized the importance of near-real-time awareness of critical assets (even those within one’s control), as there is rarely time to stop and do a full inspection of these assets when an operation is in motion.
Wadley asked how modal patterns can be assessed with infrasound techniques to determine load capacity. McKenna explained that construction practices for an area are associated with expected modal behavior for a bridge in good condition in that same area. She added that engineering tools (such as assigning military load classification remotely) are still needed in this case, as is the study of satellite images. Valerie Browning, ValTech Solutions, LLC, asked whether these techniques could be used in surveillance mode to determine what might be going over a bridge. McKenna noted that this depends upon how close one is to the bridge and how much one knows about the target. De la Garza asked whether these techniques can be used to detect whether a bridge is entering resonance as a result of specific vehicle movement, for example. McKenna responded that numerical simulations demonstrated that such an event would be in the passband, although she has yet to see this while monitoring. Kern asked whether the Department of Homeland Security has been involved in monitoring, and McKenna noted that her experimental work to date has not involved the Department of Homeland Security, primarily because all of the structures that her group has monitored in the United States are of interest to the military engineering community and so require adoption by another agency. Richard Weyers, Virginia Tech, asked whether the infrasound techniques are sensitive enough to be able to pinpoint pieces of the bridge, and she noted that this is possible if the bridge is large enough to generate infrasound.
ADDRESSING AGING WATER RESOURCES INFRASTRUCTURE CHALLENGES WITH FORENSICS, SERVICE LIFE MODELING, AND ADVANCED MATERIALS
Robert Moser, U.S. Army Engineer Research and Development Center
Moser described how scientific methods can be used to study infrastructure, understand the current state of structures, predict how damage progresses in the future, and integrate new types of materials to address aging infrastructure challenges. He emphasized that the techniques used for water resources infrastructure can also be used for many other types of structures if the mechanisms of deterioration are the same. He reiterated that the Army Corps of Engineers has a complex portfolio of aging infrastructure (on both the civil works and military sides) that needs to be addressed, including varied materials and operational facilities over 200 years old. His team focuses on trying to understand the current state of distress in existing structures, predict how that distress in going to progress, and then use that knowledge to make informed decisions in a limited funding environment—so that investments will help maintain operability in high-impact infrastructure.
Moser highlighted a few types of deterioration that affect the Corps’ infrastructure, including (1) alkali-aggregate reactions that cause cracking in concrete structures, (2) freeze/thaw distress that causes scaling and spalling in concrete structures, and (3) corrosion of metals. He explained that forensic analysis methods are used to assess materials in order to understand the current state of distress in structures, and he emphasized the value of trying to fix only those problems that one fully understands. He explained that multiple mechanisms can cause the same type of distress, so it is important to use these forensic tools (e.g., microscopy, spectroscopic analysis, mineralogical analysis) to better identify the fundamental drivers for that deterioration. Then, the repair strategy is more likely to be successful in stopping degradation. The Corps also confronts infrastructure issues related to abrasion, erosion, cavitation, geochemical dissolution, biodeterioration, salt scaling, and sulfate attacks from soil or water, for example.
A variety of service life models that consider deterioration mechanisms can then be used to predict the future state of distress, Moser continued. Model parameters must be input first, including such things as transport properties, reaction kinetics and products, and environmental conditions. Next calibration and validation data are needed—for example, survey data, structural health monitoring systems, or direct measurements of structural deterioration. This all needs to be translated to damage, according to Moser. Empirical correlations can then be made, and solid mechanics simulations can be performed. At this point in the process, he continued, it is possible to make risk-informed decisions about investing in maintenance and repair of the infrastructure. He noted that there is somewhat of a limited modeling
capacity for more complex types of deterioration and how they influence the performance of a structure, an area in which further research would be beneficial.
Moser shared an example application to understand the alkali-aggregate reaction. He explained that the process would begin with a visit to the existing structure. Historical data, if available, can be leveraged to understand expansion to date and accumulated structural damage. Without such data, crack sizes will be measured on the existing structure and related back to displacements that have occurred in that region. To understand how this damage will progress in the future, samples from the structure undergo accelerated degradation tests in the laboratory, the results of which will be fit to a model. These data are translated to a different time scale, ultimately leading to a better understanding of future damage, which is a powerful planning tool for engineers.
Moser noted that combining service life models with a life cycle cost analysis can be a useful tool to consider repair and rehabilitation alternatives (see Figure 4.3). The ultimate goal is to repair and improve durability (and thus performance) by using novel materials, which could decrease life cycle costs. These novel materials that can provide toughness and corrosion resistance for civilian facilities can be leveraged from the Corps’ military engineering programs.
For example, materials used to repair bomb craters in airfields quickly can also be used to repair lock structures quickly and maintain operations in the waterways. And materials currently used to repair damaged bridges may be adapted for application underwater, he explained.
Moser summarized that the many forms of deterioration require different methods for assessment and prediction; service life modeling tools are available for some deterioration mechanisms but not others; synergistic effects of deterioration are often neglected; service life models are often disjointed in the mechanisms they examine and could benefit from high-performance computing capabilities to study those problems in a multiphysics paradigm; and examination of advanced material options for maintenance and repair come from the integration of service life models and life cycle cost analysis.
Kern asked whether the Corps shares its research since it applies to other types of structures beyond large civilian infrastructures. Moser responded that the information is shared with the Corps’ partners and customers. Reed Mosher, U.S. Army Engineer Research and Development Center, added that DoD has restrictions on conference attendance, which prevents the Corps from sharing its information as widely as it would like. Kern pointed out that it seems quite useful for everyone to understand the use of multimodal physics and life cycles. Weyers supported Moser’s assertion that synergistic behaviors of materials need to be considered, and he asked Moser how he accounts for expansion. Moser acknowledged that this is a challenge but confirmed that expansion is a function of confinement pressure based on alkali-silicon reactions. There are not currently good methods in use to find the expansion (and thus reduce it), he continued. He added that the Corps is involved in the work to develop new test methods for complex stress states and large structures.
Reed Mosher, U.S. Army Engineer Research and Development Center
Mosher offered a historical look at Hurricane Katrina and the resulting levee and flood wall impacts in New Orleans. Hurricane Katrina hit on August 29, 2005, caused more than $100 billion in damages, and killed 1,800 people. The city was completely flooded, mostly owing to failures in the levee and flood wall system.
The Interagency Performance Evaluation Taskforce, comprising 350 members from 50 federal agencies, state organizations, and academic institutions, was asked to “provide credible and objective scientific and engineering answers to fundamental questions about the performance of the hurricane protection and flood damage reduction system in the New Orleans metropolitan area,” according to Mosher:
- The Flood Protection System: What were the design criteria for the preKatrina hurricane protection system, and did the design, as-built construction, and maintained condition meet these criteria?
- The Storm: What were the storm surges and waves used as the basis of design, and how do these compare to the storm surges and waves generated by Hurricane Katrina?
- The Performance: How did the floodwalls, levees, pumping stations, and drainage canals, individually and acting as an integrated system, perform in response to Hurricane Katrina, and why?
- The Consequences: What have been the societal-related consequences of the Katrina-related damage?
- The Risk: Following the immediate repairs, what will be the quantifiable risk to New Orleans and the vicinity from future hurricanes and tropical storms?
Mosher described New Orleans as having good intentions with poor execution and performance, as it was not resilient in its behavior. The task force had less than 1 year to complete its evaluation while recovery efforts were under way in the city. The task force took a systems approach to its analysis by trying to understand the storm, the forces, the behavior, and all of the structures that were in place. It then fed this information back into the design for rehabilitating the structure. The task force produced a 7,000-page report—Mosher focused on the section on the performance of the walls for his presentation to this workshop. Figure 4.4 depicts the task force’s physical performance analysis, which included the surge and waves, dynamic and static forces, the design and intent, and the as-built conditions.
With this system-wide strategy, the task force tried to understand the breach mechanics and the nonbreach analytical analogs and then extend them across the whole area to assess system-wide integrity. The performance evaluation included field observations, field and laboratory investigations, historical information, slope stability, nonlinear finite element analysis, centrifuge physical modeling, and peer review.
Mosher shared a map from 1849 that depicted the entire city as swamp area; it remained this way until after World War II. He noted that the Hurricane Protection System included 350 miles of levee and flood walls (250 of which were federally funded, with the remaining 100 belonging to districts and parishes), 71 pumping stations, and 4 gate outlets. The city left 36 miles of waterway exposed because it did not want to pay to move pumping stations after failed legislation; this is where the major failures occurred during Hurricane Katrina, Mosher explained. Furthermore, so much of the city is below sea level, and many of its structures were not built to the correct elevation owing to incorrect survey information. While the walls in the city were built to sustain a 1-in-100-year chance storm event, Katrina was a
1-in-450-year chance storm event, and thus the walls were ineffective. The highest surge in the storm was approximately 27 feet along the Mississippi Gulf Coast, while New Orleans experienced surges of between 8 and 16 feet in some locations. Mosher continued that these surges were more than 4 to 6 feet beyond what the area was designed to sustain. Overall, 169 miles of federal levees and 34 pumping stations were damaged, and flood levels reached a depth of 12 feet in some areas of the city. He described the major failure areas from breached walls, overtopping, levee washouts, and surges, including, among many, from the 17th Street Canal breach and along London Avenue.
Mosher cautioned against jumping to conclusions when performing forensic analysis. Although there were similar failures on numerous canals, there were different reasons for each failure. The task force’s analysis demonstrated that the 17th Street Canal breach mechanism included the following: deflection of the I-wall by surge/waves; full hydrostatic pressure along the wall that split the levee into two blocks; weaker clay at the levee toe that caused failure in the subsurface clay layer; and displacement of the soil block from the wall back. Mosher specified that the task force conducted shear strength calculations and identified the relationship between the shear strength of soil and normal clay—the design of the levee did not
separate the shear strength at the crown of the levee from the bottom of the levee. He also noted that the task force did centrifuge testing on the soil from various sites to study failure mechanisms and finite element analysis to understand the height at which the water led to big movements in the wall itself.
Mosher shared the task force’s findings and lessons learned from the 17th Street Canal breach and the London Avenue Canal breaches that were passed on to the designers. The findings and lessons learned from a study of the London Avenue Canal breaches had some similarities and some differences to those of the 17th Street Canal breaches:
- Failure Mechanisms
- The gap formation between the wall and the levee soil adjacent to the canal side of the wall (17th Street and London Avenue).
- The variation in shear strength from the levee crest to the toe and beyond (17th Street).
- Uplift pressures on the base of the levee and the marsh layer, leading to instability of the I-walls and levees (London Avenue).
- Lessons Learned
- Assume that the gap will occur, and design the walls and levees to ensure that they are stable (i.e., increase the levee toe footprint and add stability beams) (17th Street and London Avenue).
- Control the underseepage with relief wells, seepage cutoff walls, and seepage berms (London Avenue).
Regarding levee scour and erosion, the task force identified the following failure mechanisms: overtopping from surge and waves and hydraulically filled levees. The task force also learned about the need to assess the erodibility of the emplace levee materials, to avoid silts and sands and hydraulic fills for levee construction, and to increase the compaction effort for levee materials, according to Mosher.
De la Garza asked Peter Matthews if a readiness alarm sounded in USTRANSCOM when three strategic seaports and two alternative seaports were affected during Hurricane Katrina. Matthews noted that he does not believe a single hurricane will compromise all of the strategic seaports at once because the infrastructure is robust; however, USTRANSCOM is prepared to mitigate if any are unavailable for some length of time in the future. De la Garza asked Matthews how troops would have been deployed during or after Katrina (if they had not been prior to the storm), and Matthews responded that New Orleans itself is not a “power projection seaport” from a military standpoint. However, Hurricane Katrina still
taught USTRANSCOM that intra-agency and inter-agency coordination can always be improved—for example, coordination for transportation of supplies and for evacuation was limited, which created confusion and congestion.
Wadley asked Mosher to explain what has been done to prevent these types of failures from happening again. Mosher noted improvements including paved levees, berms to increase strength, increased wall heights, and relocation of pumping stations. Michael McGrath, McGrath Analytics, LLC, asked Mosher about the role of forecasts for changes in sea level. Mosher anticipated a 30-foot height by the end of this century, which means that everything has to be built at least 3 feet higher. De la Garza asked if “Katrina the sequel” has been simulated, based on the repairs that have been made. Mosher responded that not much progress has been made in terms of physical models; however, issues of levee resilience are under investigation. He expects that although flooding will still occur, recovery will be better since exposure will be reduced from relocating the pumping stations. Erik Svedberg, National Academies, asked whether these lessons learned have been applied to other natural disasters. Mosher explained that the Corps has focused primarily on developing new criteria to examine levees that incorporate the new design criteria but added that Hurricane Katrina has generally increased awareness and reinforced the need for continued research, experiments, and analysis.