Transformation in Urban Underground Infrastructure
Credit: Ricardo Gomez Angel
In September 2023 a pivotal two-day transatlantic workshop explored the state of the art in urban underground infrastructure research. The workshop was funded by UK Research and Innovation (UKRI) and the US National Science Foundation (NSF), and brought together internationally-leading infrastructure scholars and experts from the UK and USA to consider the big questions and identify major gaps in knowledge and the enabling technology. The resulting report is an important milestone in defining the opportunities for transformation in urban underground infrastructure.
Download the full report: US-UK Workshop on Transformation in Urban Underground Infrastructure.
Cities are major drivers of economic growth, technological innovation, and cultural vitality. However, their infrastructure systems are often patchworks of legacy and new components with incompatible standards, materials, and governance structures. The performance of such systems can be unpredictable under normal conditions and more so when subjected to extreme events. Mega projects are especially susceptible to cost overrun, delay, and public criticism. In the USA, for example, the Gateway Tunnel project to construct two new tunnels underneath New York’s Hudson River and repair existing tunnels is currently three years behind schedule and is expected to cost US$2 billion above original projected costs. In the UK, The London Underground’s Elizabeth Line was repeatedly delayed and re-costed, coming in almost £4 billion over its 2013 estimate.
The need for transformation
One by product of long lead times, delays and cost overruns is that the public is paying increasing amounts for services that are not delivered for decades. Long project delays create uncertainty about whether project services will be fit for purpose once delivered. It is extremely difficult to predict future service demand. For example, London’s M25 ring road was proposed in 1944 and completed in 1986, by which time it had insufficient capacity to meet demand. This problem was the result of three factors that remain relevant today: 1) insufficient demand forecasting, 2) the inability to be able to change the design to meet new demand projections, and 3) inducing demand once in use.
Without a paradigm shift in how infrastructure systems are engineered, constructed, and operated, significant cost overruns are likely to continue and the gap between the services these systems are designed to deliver and the population’s requirements will continue to widen.
We require our infrastructure to operate seamlessly and continuously, supporting uninterrupted movement and commerce. This can be a challenge for underground infrastructures such as water and wastewater, transportation, telecommunications, and power systems, because of access difficulties and the harsh underground environment in which these systems reside. Smart city and digital twin concepts offer a promising direction to help reduce this challenge, especially given new breakthroughs in sensing and computation. However, key knowledge gaps remain.
As national governments invest into the trillions in infrastructure to combat climate change (e.g., US Inflation Reduction Act of 2022 and the UK Net Zero Strategy), there is a window of opportunity to mobilise scientific communities to create socially equitable, minimally disruptive and potentially transformative solutions for sub-surface infrastructure.
Opportunities for improving the utilisation of underground infrastructure
The transatlantic workshop brought together experts in civil engineering, urban planning, computer science, operations engineering, public policy, sensing, energy, waste and other fields to explore how underground infrastructure systems can better support a net zero future.
It became clear that we do not fully understand the subsurface, we do not work efficiently in the subsurface, and we do not use the subsurface to its full potential. Seven thematic areas were identified as offering enablers and potential solutions to these challenges:
1. Sustainability, resilience and equity
The ability of the underground to positively contribute to sustainability, resilience and equity are evident but poorly understood. Additionally, sustainability, resilience, and equity do not always complement each other and so it is important to fully understand the trade-offs. For example, underground infrastructure should actively decrease societal disparities, but difficult decisions have to be made if this leads to decreased environmental sustainability and resilience. Nations must better understand the costs and benefits of centralised versus decentralised systems and develop national strategies for underground infrastructure.
2. Ownership, governance, regulations, codes and standards
Unfortunately, underground ownership, governance, regulations, codes and standards lag behind their surface equivalents. For example, it is not always clear or established who owns and governs the subsurface, its contents and the rights of way through it. Clear ownership may be desirable as it comes with the possibility of investment and profit, but it also requires capital investment and exposes the owner to legal liability. It is important, therefore, that governance models, regulations, codes and standards for the underground encourage innovation and investment and reduce risk. In addition, clear processes for educating engineers and other stakeholders in new codes and standards will be necessary.
3. Hazards
The subsurface is both a victim to and a creator of hazards. Emerging risks for underground infrastructure are not well understood. Hazard-driven design priorities should be used to reduce the risk borne by underground projects, but new techniques are needed to support below-ground hazard identification and characterisation. Perhaps the most substantial contributor to risk reduction, and thus ripe for prioritisation, is the better understanding of subsurface and infrastructure conditions.
4. Technological innovation
Identifying which technologies are worth developing can be expensive and time consuming and so must be underpinned by robust research and testing. Faster construction and smart and proactive maintenance and retrofitting planning and implementation can address risks. New materials that are self-aware, self-healing, self-maintaining, regenerative and report on their condition and function should be specifically developed for underground infrastructure. An ‘internet of things’ for the subsurface could support a smart subsurface with self-aware and self-maintaining assets, and ‘subsurface observatories’ could test technologies and processes, devise and evaluate new tools and models, assess data provision and analytics approaches, assess and develop best practices, and demonstrate value.
5. Data
Inventories of underground built asset locations and conditions, such as the UK’s National Underground Asset Register (NUAR), need to be created and maintained. High quality data, and policies and mechanisms that encourage data curation and data sharing, are necessary. Issues of data privacy, security protection, and responsibility must be addressed. In addition, data in the immediate aftermath of extreme events should be captured as a matter of course.
6. Metrics, tools and models
Data, when available, can be exploited by metrics, tools and models to create deeper understandings. Metrics tools and models designed specifically for the underground are needed to create a value proposition and to assess the potential costs of taking or not taking action. With metrics come the ability set standards. From standards, regulations follow. Once there are regulations, legislation can be established.
7. Systems of systems and collaboration
A collaborative, systems-of-systems approach to transforming underground infrastructure is an imperative. No one industry, sector, profession or discipline can truly take a systems-of-systems approach; collaboration is needed. Furthermore, that collaboration must be supported with processes and funding.
There is a clear need for a transformation in underground infrastructure to enable nations to use the underground to its full potential. The workshop uncovered a wide variety of challenges associated with constructing, operating, monitoring, maintaining and decommissioning subsurface infrastructure. It revealed a broad lack of understanding in many key areas, and the urgent need for scientific and technological advancement.
The delegation identified commonalities between the UK and USA in the challenges and successes associated with constructing and operating underground infrastructure. Combining approaches, such as ontologies, map forms, model languages and data sharing, were noted as drivers of transformation.
This report is a first step toward driving transformation and advancement in underground infrastructure. It provides a firm base on which future work can build to advance our understanding and technology, and to overcome the barriers to transforming our underground infrastructure systems.
Download the full report: US-UK Workshop on Transformation in Urban Underground Infrastructure
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