is not a simple feat, but is essential to our capacity for resilience and ability to adapt to future challenges. An integrated three-dimensional approach to infrastructure design and management that considers and values space usage and human and social needs over time benefits all sectors of the community by protecting public health, reducing risks, maximizing reliability and long-term performance of urban infrastructure systems, and minimizing long-term costs.

The underground is a valuable resource. Urban planning too rarely takes a systematic account of the space both above and beneath Earth’s surface on a coordinated basis at any large scale, and rarely incorporates infrastructure lifecycle planning or long-term infrastructure sustainability when deciding a future course. Under the sponsorship of the National Science Foundation, the NRC convened a new panel of experts to explore sustainable underground development in the urban environment, to identify research needed to make good use of the advantages, and to develop an enhanced public and technical community understanding of the role of engineering of underground space in the sustainability of the urban built environment. The committee comprised researchers and practitioners with expertise in geotechnical engineering, underground construction, trenchless technologies, risk assessment, and visualization techniques for geotechnical applications. Additionally, the committee included expertise in sustainable infrastructure development, infrastructure policy and planning, and fire prevention, safety, and ventilation in the underground. The committee’s statement of task is provided in Box 1.1. Committee member biographies are included as Appendix A, and agendas from the committee’s open session meetings are included in Appendix B.


In general terms, urban infrastructure refers to all those physical and organizational structures that allow an urban system to function. Many types of infrastructure form the physical setting of the urban system (e.g., roads, utilities, buildings) and the governing, economic, and social frameworks that define a society. Underground infrastructure refers to any physical infrastructure that is placed beneath the surface and includes underground utilities (e.g., water, power, gas, communications, waste management), transportation (e.g., roads and highways, subways, freight and passenger rail) and their supporting facilities, building foundations, and any structure built in the underground to accommodate residential, industrial, manufacturing, recreational, or other purpose. Many types of infrastructure are further defined in Chapter 3. Given the broad nature of the committee charge and the many types of underground infrastructure, this report often generalizes underground infrastructure as a single category in many discussions, especially when referring to systems of infrastructure. It should be noted, however, that the benefits and challenges of individual types of underground infrastructure are not shared by all. Underground infrastructure is owned and operating by many different types of entities that serve many types

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