Addressing sustainability demands a certain level of societal commitment and capacity to do the necessary work. This chapter examines issues related to society’s capacity to use underground engineering as part of the means to enhance urban sustainability. The committee’s task included exploring advantages of underground development, identifying research to capitalize on underground engineering opportunities, suggesting a research track direction to enhance needed human capacity, and exploring the drivers for underground development that enhance sustainability. In deliberating its charge, the committee came to realize that current models for education, research, and practice in fields relevant to underground engineering are more likely to encourage ad hoc and independent activity rather than the interdisciplinary efforts that promote sustainability. Market forces in the United States often encourage needed workforce capacity growth and urban and infrastructure development, but advances are often driven by the need to solve a particular engineering challenge in a particular setting without necessarily considering the broader societal benefits and impacts. Current institutional systems are not designed to develop the kinds of capacity needed for sustainable development. A new framework is needed that will enhance societal capacity and the types of research, education, training, and practices needed for sustainable urban planning and infrastructure development.
Societal capacity is greater than workforce capacity and includes:
• Sufficient availability of appropriately trained and experienced engineers, planners, architects, technicians, and other professionals to teach, research, plan, design, construct, operate, and maintain effective and resilient underground facilities;
• An adequate government, university, and industry commitment to develop the research capacity needed to keep the United States at the forefront of science and technology developments related to urban underground construction and space use (including the mechanical and electrical systems that are part of underground infrastructure);
• Sufficiently well-informed citizens and decision makers who appreciate the long-term implications of underground space use on the quality of life in urban areas; and
• Adequate institutional planning, policy, educational, and research structures that support cross-disciplinary and cross-sector initiatives to optimize sustainability and resilience through the use of underground facilities.
The preceding chapters describe realized and potential contributions of underground infrastructure and engineering to a sustainable urban society, and many areas of research and action items are identified throughout. The committee was not asked to prioritize these items because to do so would require an assessment of greater complexity than this committee could have achieved given the scale of its assignment. Instead, the committee identifies common themes related to changes in approaches to urban planning and underground engineering education, research, and practice necessary to promote urban sustainability. In this chapter, the committee presents a series of observations, conclusions, action items, and research necessary to support the most productive use of underground engineering for sustainable urban development. The conclusions are largely focused on the institutional frameworks that would support societal capacity, without which sustainability goals are less likely to be obtained.
Observation: There is little strategic coordination of underground infrastructure development in the United States.
Conclusion 1. Coordinated formal administrative support and management of underground infrastructure as part of an integrated, multi-dimensional, above- and belowground system of urban systems is vital to urban sustainability.
a. Recognize responsibilities related to formal support for underground infrastructure as part of the total urban system through coordinated planning and operations, fostered technological development, and local and regional rule making.
b. Develop and encourage use of a system for consistent data collection,
a. Explore within the federal government the most appropriate technical and administrative approaches to facilitate coordinated management of the underground as part of a total urban system. Recognize and coordinate with ongoing research in this area, for example, that conducted by the National Research Council (NRC) Transportation Research Board related to road projects.
b. Conduct a technology scan of how countries and cities around the world collect, manage, make available, and use three-dimensional geological and buried structure information.
Urban infrastructure generally, and underground infrastructure more specifically, is owned, constructed, operated, and maintained by many different privateand public-sector organizations to serve an even larger number of stakeholders. These different groups may each have their own unique missions, be driven by different goals, and have different financial vehicles, all of which may be divergent. Contractors hired to construct or operate underground infrastructure may not have long-term commitment to the infrastructure or the region. There may be little opportunity for owners and operators to understand the interdependencies between their respective infrastructure systems.
Consideration of the spatial and functional interdependencies of surface and underground infrastructure during all phases of infrastructure life cycle is vital to urban sustainability. However, cultural and political conventions in the United States tend to recognize, systematically plan, and organize only the real estate and air rights on or above the surface, effectively ignoring the valuable and nonrenewable real estate beneath our feet (with the exception of resource extraction). Further, since the 1980s, the United States has lacked a coordinated multi-agency federal thrust to keep U.S. research and technology at the forefront in underground development. Infrastructure development, in general, and underground infrastructure development, in particular, suffer in the United States from being organized by sectors and without any mission agency or other organization within the federal establishment dedicated to coordination across sectors. This coordination could lead to a better management of research investments and reduced risk for federal investments (particularly of large infrastructure projects), and could also be coordinated with investments by states and municipalities. Integrated, holistic, and three-dimensional planning is necessary.
All levels of government in many regions of the country are facing economic difficulties that may be the economic norm for years to come. The intergovernmental financial assistance system that has made many underground systems possible may not be able to invest in underground infrastructure as has been done
in the past. Development of an institutional framework that catalyzes sustainable growth patterns through strategic targeted investments becomes even more important under such economic circumstances. Information management, information technologies, and communication will be key in facilitating the complex but efficient research and the design, construction, operation, and management of underground infrastructure.
Observation: Market forces in the United States encourage workforce capacity growth and urban and infrastructure development, but often in an ad hoc manner that may not be consistent with urban sustainability.
Conclusion 2. Development of underground space as part of sustainable urbanization requires expanded and coordinated communication with stakeholders to better incorporate site-specific conditions, greater flexibility, and long-term community needs into infrastructure system design and optimal lifecycle management.
a. Establish a federally led interdisciplinary network or organization of organizations and institutions to guide sustainable patterns in underground infrastructure development and encourage interdisciplinary research and communication of findings among all disciplines and stakeholders. Stakeholders include, for example, designers, long-term planners, architects, safety specialists, and an array of engineering, geologic, geophysical, environmental, and contracting specialists from industry, government, and academia.
b. Develop mechanisms for integrated and holistic three-dimensional research and planning that include information management and communication technologies to facilitate complex research, design, construction, operation, and management of underground infrastructure.
a. Explore models for designing sustainability into engineered systems of urban systems that recognize interdependencies, vulnerabilities, complexity, and adaptability. Coordinate ongoing research in the United States and elsewhere on, for example, complex adaptive systems and human factors engineering (e.g., incorporating behavioral science, human performance and capacity, personnel and training, and human biology and physiology into engineered systems).
b. Develop conceptual models of the complex interactions among multiple systems (e.g., mechanical, human, and environmental) to improve understanding, reduce risk, and effectively manage infrastructure amid changing technologies, societal conditions, and expectations.
c. Research the behavior of those operating, maintaining, and using underground infrastructure during normal and worst-case operation scenarios to optimize the human-technical interfaces in a manner consistent with long-term values.
An institutional framework that catalyzes sustainable development and adequately revitalizes the U.S. educational and research capacity to address sustainable urban underground space is needed. Required technical human capital could be developed within this framework by bringing federal, state, and local agencies, the engineering and construction industries, and university educators and researchers under the same umbrella. Underground space development could then be addressed in a holistic manner through integrated educational and research programs that extend beyond traditional undergraduate, graduate, and continuing engineering education and training. This involves significant changes in the basic structure of several professional degree programs in the United States including planning, architecture, engineering, public administration, and social and economic policy—a difficult undertaking. The nation needs planners that understand underground space and economists that better understand how underground infrastructure supports lifeline service provision and a robust economic urban environment. The NRC Transportation Research Board and the National Earthquake Hazard Reduction Program might be studied to determine what elements of those organizational models might be incorporated into an institutional framework as discussed here. It is particularly important that engineers understand social and economic factors that contribute to urban sustainability, but it is just as important that other stakeholders involved in urban planning and underground development have realistic expectations of engineering.
Shared information on the relationships among individual systems and overall system performance is vital, and an ontology that is accepted across sectors and institutional cultures is needed for coordination and collaboration (see Box 7.1). Data and models used to understand the direct, indirect, and social costs of decisions related to individual infrastructure elements over the life cycle of the system can be the basis for better decision making related to, for example, performance versus needed investments for repair, rehabilitation, or replacement.
Observation: Complex ownership models for underground infrastructure confuse responsibility for routine inspections, maintenance, repairs, guidelines, budgets, and liability.
Conclusion 3. There is a need to understand the ownership and control models of underground space and to develop guidelines for funding and performing essential periodic inspections, maintenance, and repair of individual infrastructure elements.
a. Analyze multidisciplinary and holistic approaches to view the complex web of ownership, control, and responsibilities associated with maintenance and safety of underground infrastructure.
b. Examine multidisciplinary approaches to aid transition to more modern systems management.
Understanding ownership, liability, and responsibility for underground space becomes more important if infrastructure management is to support improved sustainability across the full complexity of interlinked underground systems. Safety related to failure of, for example, underground utilities also needs to be addressed. With the increasing appreciation of Supervisory Control and Data Acquisition (SCADA) systems and their vulnerabilities, anticipatory strategies need to be developed to investigate events and either direct threats to urban society, or those that are the result of cascading failures. Past underinvestment in infrastructure construction and rehabilitation increases current and future vulnerability as a result of inadequate inspections, unrepaired deterioration, inadequate system capacity, and lack of adaptation to new demands and challenges.
Observation: The United States was a world leader in many areas of underground science and technology when there was federal and industry investment in underground engineering research and development.
Conclusion 4. Maintaining global competitiveness in underground engineering education, technology development, and practice supports urban sustainability, resilience, and the standard of living of the United States.
Potential Action: Allocate resources for broader interdisciplinary education and technology development in underground design and construction.
Research: Expand U.S. research that advances and revolutionizes, for example, materials technologies, robotic construction technologies, laser guidance systems, geographic information systems, and enhanced computer analysis and visualization systems that improve the ability to model, design, plan, and reduce risk associated with complex underground systems (see Chapter 6 for more detail).
It can be argued that achieving and maintaining a technological leadership position in underground engineering is not necessary for the United States to reap all the benefits from effective urban underground facilities. The United States
Managing and Sharing Data
Poorly delineated interdependencies may represent emerging risks, particularly in relation to extreme events. For example, performance maintenance, protection from attack, long- or short-term costs, quality of service, or equity of access and supply need to be investigated in terms of space (area affected, geographical linkage to secondary impacts, etc.) and time (temporal evolution of impacts and recovery) in order to optimize design or operation. Different modeling tools will necessarily serve different sets of stakeholders, but the information developed by them will be most useful if their formats are compatible and if they have common spatial and temporal registrations. System data and models often need high security but the means need to be developed to share the relevant and necessary information for studies of interdependency with a targeted user community. Uncertainties about data pedigree often exist in many infrastructure databases, and protocols that can provide information on data quality, resolution, uncertainty, and trustworthiness for example are important. Likewise, the management and curation of massive real-time data flows from performance sensing arrays and smart systems will become more important, as will tools for data mining, protocols for metadata generation, and tools to support rapid data interpretation including visualization.
does benefit from technologies developed elsewhere, but it is not in the country’s best interest to rely as strongly on imported technologies and expertise as is currently done. Many underground critical facilities are specifically designed to provide enhanced security and resilience in the face of potential extreme events or risks. Further, although outside the scope of this report, underground engineering is an important contributor to national defense and energy capacity. Reduced U.S. technological capacity in underground engineering can negatively contribute to economic growth and the global competitiveness of U.S. firms.
The United States has been a world leader in many areas of science and technology for underground construction (see Box 7.2) in the past. Partnerships with researchers at academic institutions in the past 40 years contributed to a continuous flow of ideas, enhanced understanding, and a high-quality graduating workforce that provided leadership for U.S. industry. However, that leadership is retiring, and few replacements have been trained. The majority of underground construction innovation (e.g., slurry walls, tieback anchors, micropiles, deep soil mixing, jet grouting, slurry and earth-pressure-balance tunneling machines, cured-in-place pipe relining systems, and many more) now comes from outside the United States.
Today in the United States, industry and research institutions continue to collaborate some on technology development, and research institutions often receive industry support for students and research. Much engineering, construction, and equipment manufacturing workforce knowledge, expertise, and training necessary for underground development occur through mentoring, on-the-job and
Once a World Leader
The United States has been a world leader in underground technologies in the past. For example, the first fully underground hydroelectric power plant was constructed at Snoqualmie Falls, Washington, in 1898 (PSE, 2009). Major developments in hard rock tunnel boring machines came about in the 1960s as a result of the decision of Chicago planners and the Metropolitan Water Reclamation District of Greater Chicago to build deep interceptor tunnels in the competent dolomite rock to eliminate sewage and storm water overflow into Lake Michigan (e.g., Hapgood, 2004). These projects engaged university researchers and resulted in knowledge growth. In the 1970s, there was intensive effort to improve underground construction technology as agencies recognized the growing need for underground space use in urban areas, particularly in conjunction with subway (with funding from the Urban Mass Transit Administration [UMTA]) and combined sewer and water projects (mandated by the U.S. Environmental Protection Agency [EPA]). These projects resulted in U.S. leadership in ground support technologies (e.g., rock bolting and tunnel lining) and tunnel boring machine design, invention, and manufacturing. With support from federal agencies including the National Science Foundation’s Research Applied to National Needs (RANN) program, UMTA, the Department of Defense, EPA, and the Department of Energy, the United States made significant advances in underground construction technologies in the 1970s and 1980s. Additionally, innovations in the pipeline construction and utility industries created radical new possibilities for pipeline and utility installations through new concepts in trenchless excavation and the adaptation of directional oil well drilling technologies to cable and pipeline installations in the 1980s and 1990s.
project-specific problem solving, extensive use of overseas construction firms on projects, and collaboration with international engineers on temporary assignments. To remain competitive, firms such as Parsons Brinkerhoff have career development programs to make up for the smaller number of colleges and universities that provide hands-on underground engineering knowledge. Industry groups such as the North American Society for Trenchless Technology (see http://nastt.org/training) also provide courses for professionals on targeted topics. However, this training is not viewed—even by those with extensive industry experience on the committee—as a broad education, and there is minimal contribution from higher education institutions to these efforts.
There are advantages but also important limitations associated with industrybased training. Economic competiveness within industry means that knowledge gained by a specific firm tends to remain with that firm and may even leave the United States if the firm returns overseas at project completion. Commercial constraints may prevent industry from embracing the challenges associated with an integrated and holistic approach to urban development, as well as those associated with infrastructure sustainability and long-term performance. In contrast, advancements made at multidisciplinary research institutes are more likely to
Multidisciplinary Research Aiding Domestic Competitiveness
From 1977 to 1995, at a time when the United States was a world leader in underground engineering technologies and innovation, the research organization with perhaps the broadest mission related to underground construction was the state-funded Underground Space Center at the University of Minnesota. The center assembled a multi-disciplinary team to look broadly at issues affecting underground space use, including public policy, planning, architectural design, geotechnical engineering, and underground heat transfer, and it became a model for several other centers around the world that guide underground space use in their respective countries. These include centers at the University of Delft in the Netherlands, Tongji University, Chongqing University and Nanjing Engineering Institute and other universities in China, and the Urban Underground Space Center of Japan. While University of Minnesota center was successful in terms of research activity and maintaining its broad mandate, the lack of a stable base funding for its mission left it vulnerable to a university- and state-funding recession that resulted in its closure in 1995.
be of greater societal benefit while also resulting in a more educated domestic workforce (see Box 7.3). This is even more important as the country prepares to address projected urban, demographic, and climate-related challenges.
Observation: Lack of funding continuity that allows meaningful investment in equipment and faculty has resulted in a substantial reduction in the number of U.S. university programs dedicated to integrated underground engineering research and education.
Conclusion 5. There is a critical shortage in educational, training, and research opportunities for engineers who wish to learn and practice underground engineering in the United States.
a. Develop national multidisciplinary, multi-institutional, cross-sector research centers that focus on different areas in underground engineering and sustainable urban infrastructure to produce the next generation of leaders in underground engineering.
b. Integrate graduate underground engineering studies with research programs or a critical mass of coordinated faculty activity to anchor research to
c. Develop university consortia to aggregate faculty expertise; strengthen industry-university faculty relationships.
d. Teach better facility planning and management with a multidisciplinary approach through traditional, distance, or hybrid-style education formats. Traineeships (e.g., NSF’s Integrative Graduate Education and Research Traineeships) could help to fund programs.
e. Expose undergraduates to multiple disciplines, issues, challenges, and opportunities associated with sustainable underground space use and engineering. f. Develop continuing education opportunities for professionals.
g. Develop appropriate credentialing for inspectors, technicians, and operators of complex underground facilities.
Good engineering depends on strong analytical skills, creativity, ingenuity, professionalism, and leadership (NAE, 2004) as well as on accumulated knowledge based on old and new successes in underground works. Undergraduate programs that contribute to the kinds of knowledge discussed in this report include but are not limited to mechanical, electrical, civil, structural, geotechnical and geological engineering, planning, architecture, public policy, fire safety, and information technology. However, traditional programs in these areas do not prepare students for an integrated approach to practice. Some interdisciplinary programs in underground engineering at the graduate level conform to the American Society of Civil Engineer’s Policy 465 to support a Master of Science (MS) degree (or equivalent) as prerequisite for professional practice (ASCE, 2007). Some examples of programs include the MS in infrastructure engineering at the University of California at Berkeley, the MS in sustainable and resilient infrastructure systems at the University of Illinois at Urbana-Champaign, and the infrastructure focus of the civil engineering program for the MS in Engineering at Louisiana Tech University (Brierley and Hawks, 2010). Graduate education at some schools includes specifically identified foci (e.g., the certificate in tunneling at the University of Texas at Austin) or specialization within a more generally named graduate degree program. Cooperative education and internships for all forms of education are especially important in underground engineering, which is less codified than, for example, engineering for structural building design.
Education and training has been integrated in some underground engineering programs including, for example, the tunneling and underground engineering group at the University of Illinois (1970s and 1980s), the Underground Space Center at the University of Minnesota (1977-1995), and the Trenchless Technology Center at Louisiana Tech University. Such research groups significantly influenced general practice and specific applications, but the size of the programs paled in comparison with the scale warranted by the level of national investments in underground space use and infrastructure.
Today, there is little expectation of the funding continuity that allows meaningful investment in equipment and faculty needed to support enduring and integrated research programs and the type of integrated graduate studies suggested here. This relates to the lack of continuous government focus on infrastructure issues in general, and underground infrastructure in particular. Relatively few university faculty in the United States engage in tunneling research, and many of those focus on tunnel performance in seismic and other extreme situations rather than on improving tunnel design and construction performance. The number of U.S. university programs dedicated to mining engineering has also reduced substantially since the 1960s: fewer than 20 exist today.
The decline of research in underground construction and tunneling in universities in the United States mirrors the fragmentation of U.S. government-sponsored activities in underground development research. An underground engineering workforce that supports sustainability cannot be created by simply merging educational programs of similar skill sets. This is true for several disciplines that are at the core of underground engineering such as geotechnical and mining engineering. Geotechnical engineering, for example, is often treated as a subdiscipline within civil engineering and hence competes for resources with structural, transportation, environmental, and other engineering disciplines. The number of geotechnical engineering faculty at a university may be only 1 or 2, and seldom more than 5 or 6 in even large civil engineering faculties of 30-40 professors.
Mining engineering education and training has suffered in part as a result of a reduction in U.S. mining activity in favor of overseas mine development. The loss of mining engineering programs, faculty, and students, given their similar core knowledge as their civil engineering colleagues, compounds the human capacity issues for underground engineering. Specialized knowledge areas such as tunneling have been put under pressure by state-mandated reductions in credit hour requirements for undergraduate degrees, the lack of interest by U.S. students in pursuing advanced degrees, and the limited or sporadic nature of funding opportunities for research in these fields.
Observation: The complexity of urban infrastructure systems and uncertainties associated with system design and performance increase with greater and more varied demands on both above- and belowground infrastructure.
Conclusion 6. Engineers and urban planners could better improve whole lifecycle facility performance and overall urban sustainability with documented and validated risk-informed approaches to project planning and design that balance lifecycle project needs in terms of service delivery, initial
a. Advance existing and develop new technologies for modeling uncertainty during all phases of infrastructure life cycle. These include invasive and noninvasive technologies for geologic site characterization (including existing and legacy infrastructure and materials); analytical and computational design methods; excavation, ground support, and monitoring technologies; and technologies for asset management including related to the management of data and security (see Chapters 6 and 7 for more details).
b. Develop strategies to investigate potential hazards, impending problems, and cascading evolution of problems, especially given current underinvestment in infrastructure system rehabilitation.
c. Engineers and planners could use extreme events to understand complex systems behaviors and interdependencies and to validate computational models of system performance.
Sustainability and resilience have only been considered in broad terms for a decade or two, and there are more questions than answers regarding what sustainability and resilience strategies are most effective. However limited our current knowledge is, however, it is necessary to act on the best knowledge we have while rapidly improving our grasp of the complex system interactions, and while developing metrics to assess progress. In this regard, the educational framework discussed above can create a new generation of professionals able to integrate technical disciplines with the emerging understanding of sustainability and resilience and integrate risk-informed approaches to design, construction, and management.
Large and complex underground facilities and networks represent major financial investments, provide critical functions and services for urban living, and must not degrade health and safety. For most cities, however, major underground projects are not a normal undertaking and hence present major challenges to policy makers and the professionals from the planning, architecture, engineering, financial, insurance, building code, and health and safety sectors that will be involved with such projects. Trusted information about alternatives, costs, benefits, and risks that can be used by all from those contributing disciplines is needed as are the means to improve that information as additional knowledge and experience is gained. Interdisciplinary research, education, and training that allow development of practical methods to determine, for example, the remaining useful life of utilities and services are needed. Consideration of topics such as how best to reuse or reconfigure underground space as technologies change are also part of performance and total lifecycle planning.
Observation: Aging underground infrastructure may be susceptible to deterioration and issues associated with changing technologies, changing climate, and societal needs.
Conclusion 7. Underground space development requires a long-term commitment to technological advancements in an environment that is friendly to improved planning, innovation, and implementation.
a. Design infrastructure that allows ease of access for inspections, maintenance, repairs, upgrades, and reconfigurations in response to new needs or technologies that allow such work to be completed at lower costs.
b. Consider resource needs, availabilities, and access when making administrative and technical decisions concerning development. These include energy resources (e.g., oil, gas, and other energy resources), industrial minerals, high-value or critical strategic minerals (e.g., gold, uranium, rare earth elements), and construction materials (e.g., gravel, sand, building stone).
c. Use appropriate models that demonstrate multiple potential scenarios and allow better infrastructural system planning based on local conditions.
a. Academia and system stakeholders could collaboratively develop long-term performance simulation models for complex systems and validate the results over time to understand dynamic responses and emerging system behaviors.
b. Explore how technologies and innovations from other industries (e.g., exploration tools, in situ analytical techniques, measurement-while-drilling systems, laser scanning, fusion of multi-sensor data) and civilian application of military research could be applied to underground engineering.
c. Conduct long-term research on the effects of the underground infrastructure on the natural and built environments to increase the capacity of decision making for society’s best long-term interests.
d. Research comprehensively and on a common risk-cost-reward basis the long-term effects on sustainability of underground storage or disposal of urban wastes (e.g., municipal, sewage, or energy-related products).
Improved technologies can enhance the ability to select the most sustainable approach to underground space use by making such use cheaper or better. For example, the development of better planning, design, and construction technologies can reduce construction costs, minimize deterioration, increase resilience,
and address geologic, hydrologic, environmental, thermal, and social issues that exist or may arise over time. Technologies have improved in the past decades, but, interestingly, many of the general areas in which improvements are regularly cited as being needed have not changed. For example, in 1989, the National Research Council identified the ways in which geotechnology impacts the U.S. economy, the environment, and national security (NRC, 1989). Multiple research themes deserving special attention were identified that could contribute to infrastructure development and rehabilitation including:
• Influences of construction on nearby structures;
• trenchless construction technologies for installing and rehabilitating utility pipe networks (see Box 7.4);
• development and use of new materials such as plastic pipe, polymers, and geosynthetic materials to address infrastructure system needs;
• maintenance and renewal of aging infrastructure systems, including remote sensing systems to locate and assess infrastructure system quality; and
• an interdisciplinary approach to solving the diverse needs of complex infrastructure systems.
Research in many of these areas has improved U.S. capacity to develop underground systems, but research in these same areas is still warranted today, especially given national interest in sustainability and resilience. Chapter 6 provides a detailed discussion on needed technology innovations associated with site characterization, and underground infrastructure design, construction, operation, monitoring, and maintenance that could contribute to sustainable development.
Some specific technology development challenges and opportunities for research that would aid a more holistic approach to integrated urban system design and operation are highlighted in previous chapters and in Boxes 7.4 and 7.5.
Observation: Few data exist regarding the environmental and social impacts and lifecycle sustainability of urban development that can inform technology and administrative decisions related to long-term (decades to centuries) infrastructure operation, maintenance, and reduced costs.
Conclusion 8. Comprehensive and scientific retrospective studies of the direct and indirect costs and impacts of various types of underground projects are needed to evaluate usefulness and economic, environmental, and social impacts so that future planning can maximize sustainability.
Specific Challenges for Pipe and Cable Systems
• Piping systems in the United States have expected service lives of 50 to 100 years, and cables have expected service lives of 10 to 15 years (EPA, 2008). Many systems in the United States have exceeded their expected service lives and may fail in coming years if not renovated or replaced.
• The development of new pipe and cable materials that perform better over longer life cycles, as well as of new smart underground infrastructure networks that monitor their own performance and condition are needed. Smart systems could allow improved prediction of needed repairs before costly failures occur. The result could be more intelligent infrastructure maintenance planning and integrated decision making. For example, needed repairs in an area could be coordinated, minimizing combined repair costs and closure of public rights of way.
• Three-dimensional position and performance information is important, especially given the premium now placed on new techniques to rehabilitate conduits and increase capacity of existing pipe in situ rather than creating new alignments.
• Utilidors that combine utility systems into compact and maintainable configurations may be effectively justified through development of workable scenarios for secure multi-utility facilities, lifecycle cost-benefit analyses, and effective transitioning strategies combined with demonstration projects.
• Future design standards need to include consideration of the role of individual system elements in the larger urban system over their life cycles. Standards also need to anticipate, for example, the effects of climate change in a region (e.g., drainage systems may require greater capacity to accommodate increased intensity, duration, and frequency of storms).
• Planning and design will need to accommodate multi-hazard approaches to risk-based management over the life cycle of systems and will need to consider long-term robustness, resilience, and sustainability during design and operation. For example, the impacts on groundwater resources and structural adequacy, buoyancy, water tightness, and corrosion will require increased attention in areas affected by changing groundwater levels (especially if coupled with saltwater intrusion).
a. Conduct comprehensive and scientific investigations to retrospectively identify the lifecycle performance of various types of underground infrastructure and to identify the aspects of project planning, design, construction, and operation that contribute most to project costs and performance. For example, track financial (both direct and indirect), environmental (e.g., air and water quality), and social impacts over an extended period (e.g., decades) following a project such as Boston’s Central Artery alignment.
b. Develop common metrics for assessing sustainable development more generally, and for assessing specific economic, environmental, and social impacts.
c. Develop quantitative methods to compare the value of underground space
Mapping and Data Capture and Assessment Technologies
Urban underground space can be better managed with less labor-intensive means to map accurate positions of all underground utilities, perform essential lifeline service inspections, and manage the resulting massive databases. Reliable documentation of all things underground in an accessible and searchable database system would improve the ability of planners to maximize underground space use while minimizing construction and maintenance costs. The technologies also could lead to better long-term systems approaches to planning, construction, operations, and maintenance. The means also could be developed to dynamically link ground information models with feedback from construction or monitoring equipment to enable real-time characterization, response prediction, and decision making related to processes throughout infrastructure life cycles. However, underground data collection and transmission related to wired system robustness and wireless system transmission capabilities and energy requirements still present challenges. Sensors and network systems are needed that can be placed underground in widely distributed and self-organizing networks, that allow long-term operation (including calibration and location registration and configuration), and that can be operated remotely. Coordinated technology developments could be considered in areas such as low-power sensing and systems, power scavenging and harvesting, or the development of wireless signal transmission systems in the underground.
on a par with other urban resources (e.g., linked to market value of surface property) and in consideration of the impacts on future underground use (e.g., infrastructure may need to be placed in increasingly difficult ground conditions).
d. Compile data about sustainability aspects of various construction methods and materials (e.g., the availability of materials and energy embodied in production of materials).
Lifecycle analysis is a strategic tool that can inform decisions related to operations, maintenance, costs, and environmental impacts that affect sustainability. Understanding whether, for example, urban underground development precludes good stewardship of underground water resources in a region may require quantifying the amount of evapotranspiration, groundwater recharge, flow patterns, and pollution, among other factors, enabled because of different construction techniques or the preservation of natural landscapes. Retrospective analyses inform strategic prospective lifecycle cost analyses that, ideally, become part of local and regional planning processes. Decision makers that understand the true costs of infrastructure options over time are likely better poised to make decisions that support sustainability. Design decisions that affect sustainability include, for example, those that integrate initial (during construction) and permanent ground support systems that require less construction materials, use materials with improved performance, or incorporate more waste or by-product
Capturing all costs, such as diminished air quality or those associated with disruption and business losses during street closures, in a comparison of project alternatives remains a challenge and a topic for future research. Although costs may differ significantly among similar projects, discrepancies observed in the cost of a lane-kilometer of roadway in various countries, for example, suggest that investigating the detailed reasons for lower costs in some countries as compared to others would be worthwhile. Understanding such relationships would assist development of a realistic management framework that objectively distributes total costs over infrastructure life cycle. An entire infrastructure management framework could be informed that includes planning, documenting existing conditions, establishing land use requirements (both above and below ground), and issuance of permits for approved underground use (as directed by informed policy).
Observation: Underground infrastructure can safely enhance the lives of millions, but few federal-level safety regulations exist to guide operational safety at a time when underground system complexity is increasing.
Conclusion 9. Greater user acceptance and occupancy of underground infrastructure and facilities are likely if underground spaces are planned with more consideration of utility, ease of access, wayfinding, safety, and aesthetics.
a. Develop and adopt performance-based safety mechanisms and codes that not only account for today’s underground occupancies (e.g., mixed use, multi level) and risks, but also allow for expansion and change of use. The International Code Council technical requirements, applicable National Fire Protection Association standards, and other related standards and guidelines could be expanded and made applicable to underground facilities.
b. Incorporate human factor and complex systems engineering concepts to guide threat recognition and technical and operational decision making for normal operations and for operations during times of stress (e.g., in response to extreme events).
c. Incorporate behavioral science, training, biology and physiology, human performance and capacity into safety codes and design.
a. Research the state of practice and best practices related to safety systems (e.g., hazard detection, notification, ventilation, fire suppression, emergency egress, and system integration). Develop appropriate minimum safety system requirements to incorporate into national-level guidelines and standards.
b. Compare international underground safety codes and guidelines with those applicable in the United States to identify inadequacies and guide future practice, recognizing existing efforts in this area (e.g., by the Federal Highway Administration).
Public acceptance and use of underground space will increase if underground infrastructure is more convenient and comfortable to use. One design challenge is long-range planning that incorporates strong connectivity within underground systems and with surface systems. This means creating usable reasonably connected underground systems that limit pedestrian travel time and lengthy vertical movement by stairs, escalators, or elevators. However, existing building codes may not be flexible enough to accommodate the types of design that increase convenience.
Building codes exist to protect the health and safety of those constructing, operating, or using infrastructure, but their slowly evolving nature leaves little room to benefit from evolving technologies. Further, existing safety codes, regulations, and standards designed to address known risks above ground are often inadequate for large-scale, sustainable development of the underground. Largescale public use will require development of new and updated safety regulations that specifically address risk of the underground and activities (occupancies) therein.
Allowing variation in design based on better understanding of how to create safe but interesting and enjoyable underground space without greatly increasing costs and space requirements remains a challenge. Incorporating more human factors engineering into underground and urban system design and operation may improve the underground for safety, productivity, and aesthetics. Research into new materials and their behaviors, combined with risk assessments and management activities that incorporate, for example, provisions for emergency evacuations, rescue, and recovery would benefit the underground environment during normal operations, as well as during and following stressful events. Identifying and countering negative perceptions can be as important as safety and technical challenges and require their own research focus.
Observation: Underground space is a valuable but decidedly nonrenewable resource.
Conclusion 10. Underground space can enhance urban sustainability only if the underground is thoroughly understood and if underground use and reuse and the protection of the natural and built environments are incorporated into long-term total urban infrastructure system planning.
a. Institute planning of all underground space as part of an evolving urban system to be carefully engineered or preserved for optimal long-term use and regional sustainability.
b. Establish reasonably intensive groundwater, soil, and infrastructure monitoring practices to track the health of the underground urban environment according to the general geologic conditions and use. Use data generated from a range of environments and situations to inform urban planning in other areas.
It is easy to look at a photograph of a city and envision a three-dimensional model of its surface structures, skyscrapers, and raised highways. This report challenges many urban planners, designers, engineers, researchers, contractors, and infrastructure operators to include the subsurface in this three-dimensional model, and to coherently link infrastructure between the surface and subsurface. Just as there is only so much surface area in a given city, there is only so much usable underground volume beneath the surface. However, unlike infrastructure on the surface, underground infrastructure cannot be easily removed or rebuilt when its useful life ends. Once subsurface geologic materials are removed and infrastructure elements or waste are put in their place, the subsurface cannot be restored to its original state and possibly may not be used for other purposes. For this reason, urban sustainability is dependent on thorough understanding of the underground and how best to plan for the use, reuse, and protection of underground resources—whether referring to natural energy or material resources, or to the underground space itself.
People have exploited underground space and resources for thousands of years to advance and protect survival, economic prospects, mythological culture, and spiritual growth. These endeavors involved high risks offset by the belief that the benefits of the underground exceeded the dangers—long before there was detailed understanding of the underground environment or sophisticated tools with which to explore it. However, early successes and failures in the underground helped build the substantial knowledge base that exists today throughout the world. The challenge now is to create a comparable legacy to sustain the
nation’s natural resources, economic efficiency, and social solidarity for the long term. This means expanding our knowledge base in ways that align our technical tools, collective perceptions, public policies, regulations, and procedures so that we can reduce risks to negligible levels, create needed services and spaces that function reliably and lift our spirits, and ultimately provide an integral and balanced support system for livable and sustainable urban areas.
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