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Reducing Damage to Underground Utility Infrastructure during Excavation: Costs, benefits, technical advances, case studies, and recommendations

image credit: Image by GZeiss

Summary of a white paper prepared for the Geospatial Information & Technology Association by Geoff Zeiss and Dr. Sakura Shinoaki

Over the past two decades in the U.S. there have been over 400 fatalities and nearly 2000 injuries attributed to hitting underground infrastructure during excavations. For comparison over the past 20 years in the U.S., there have been about the same number of fatalities (403) resulting from major commercial airline crashes (excluding 9/11). In addition inaccurate and missing information about underground infrastructure increases the risk of construction project schedule and budget overruns. It has been estimated that unreliable location information about underground infrastructure represents a $50 billion to $100 billion drag on the U.S. economy, multiple £ billions in the U.K. and € 1 billion in the Netherlands. Comparing the United States and Japan reveals a startling difference in the number of incidents of underground utility damage during construction. In the U.S. the number of incidents is between 400,000 and 800,000 per year (roughly one or two every minute). For Japan the number of incidents in 2016 was 134. Clearly something can be done to reduce the risk for construction workers and the public.

Underground utility damage is expensive.  Several jurisdictions have attempted to estimate the cost of underground utility damage for individual incidents and for entire national economies.  Costs can be broken down into direct costs and indirect costs. Direct costs include the costs of sending a crew to repair the damaged pipe or cable. Indirect costs include many factors that are often hard to quantify such as traffic disruption, injuries and fatalities among workers and the public, and the lost custom that local businesses experience. In the U.S. it is estimated that there are between 400,000 and 800,000 incidents of underground utility damage every year.  In the Netherlands there are over 41,000 incidents annually. Data collected by the Common Ground Alliance in the U.S. and KLIC in the Netherlands and research at the University of Birmingham in the U.K. have estimated the direct cost of underground utility damage in those jurisdictions. Furthermore, research at the University of Birmingham has estimated that total costs (direct+indirect) are 29 X direct costs. This leads to the important conclusion that underground utility damage represents a major drag on national economies, $50 to $100 billion annually in the U.S., £ billions in the U.K., and  € 1 billion in the Netherlands.

Government agencies and construction firms are recognizing that accurate models of underground infrastructure bring practical benefits to construction projects.  For example, the Sydney Light Rail extension is particularly interesting because a consulting firm hired to study this five year project concluded that if a complete and reliable 3D map of underground infrastructure had been available at the project planning stage, the project could have been completed at least one and a half years sooner.  The Alabama Department of Transportation saved $10 million by using 3D modeling of underground utilities on a major highway interchange project. The Expo Milano project estimated that it saved about €16 for every euro invested in improving the information about underground infrastructure. For a highway revitalization project in Cedar Falls, Iowa a 3D model of underground utilities was created before the start of the design phase.  200 utility conflicts were found prior to beginning construction, enabling the project to complete on schedule and 3% under bid. For a gas pipeline project in Washington State, a 3D model of underground infrastructure developed prior to design made it possible to compare alternative routes to determine the optimal routing for the new pipeline. These examples show that an accurate model (preferably in 3D) of underground utilities can not only reduce the risk of underground utility damage and the associated project delays and budget overruns but can also reduce the cost of infrastructure by designing to reduce unnecessary and costly moving of utilities.

In the last few years there have been important advances in technology for detecting underground infrastructure.  There include ground penetrating radar (GPR) capable of capturing scans at roadway speeds, software that simplifies the interpretation of GMPR scans, using LiDAR, to efficiently capture the location of newly installed underground pipelines, simultaneously capturing above and below-ground scans using LiDAR, and GPR, inertial mapping of pipe networks, acoustic locating down to 30 feet, using smartphones to inexpensively capture the location of underground cables and pipes exposed during construction, and mixed reality to visualize underground utilities.

Accurately mapping underground utility and telecom network assets represents a growing opportunity for professional surveyors. In order to ensure continuing improvement in the accuracy of location information about underground utilities, some international jurisdictions are requiring that new or modified underground infrastructure be surveyed by a registered surveyor. Technical advances are making it easier for surveyors to conduct underground surveys. For construction projects owners, engineers and contractors are increasingly recognizing that surveyors who can offer a combined above- and below-ground survey are able to add significantly more value than the traditional above-ground-only survey.

Standards relating to locating and mapping underground infrastructure are advancing rapidly.  The American Society of Civil Engineers (ASCE) is nearing completion of a new quality Standard Guideline for Recording and Exchanging Utility Infrastructure Data (also referred to as the utility as-built standard) to complement ASCE 38-02.  A new revision of the British quality/confidence standard PAS 128 is also nearing completion.   The Open Geospatial Consortium is forming a Standards Working Group (SWG) to complete the Model for Underground Data Definition and Integration (MUDDI), which is intended to provide an open standards-based way to share information about the underground. 

Return on investment (ROI) studies of subsurface utility engineering (SUE) surveys applied to highway construction projects conducted since the late 1990s have consistently revealed a large return-on-investment from conducting SUE surveys as part of highway construction projects. One of the first by Purdue University in 1999 estimated that requiring SUE on highway construction projects would result in at least $1 billion in savings annually.  The most recent analysis for the Pennsylvania Department of Transport (PennDOT) differed from previous analyses by including both SUE and non-SUE projects. It estimated $11.39 in savings for every $1 spent on SUE. The study also showed that the greater the complexity level of buried utilities, the higher the SUE benefits. The largest contributor to the cost savings from SUE was a 40.33% reduction in project relocation costs by providing accurate underground utility information in the early stages of design. The next largest cost savings were 29.46% savings in construction and design costs, 9.59% reduction in redesign costs and 9.08% reduction in project delay costs due to utility relocation.  SUE enables designers to design efficiently and accurately with reliable information, so that design time can be saved and unnecessary construction work can be avoided or reduced. The cost of conducting a SUE survey was estimated to be 1.65% of project cost. The study concluded that SUE can provide accurate utility information with important project benefits at reasonable cost. 

While SUE surveys have been shown to reduce the risk of budget overruns and project delays for construction projects, they are not a silver bullet for reducing the number of incidents of underground utility damage.

Over the years I have personally compiled information on 25 jurisdictions in the Americas, Europe, and Asia Pacific that have implemented policies and organizational structures for sharing information about the location of underground infrastructure. These include comprehensive programs involving many different stakeholders, government mandated and run, government mandated and industry financed and run, industry supported and privately run, and municipally mandated and run. While many jurisdictions have attempted to address the problem of damage to underground infrastructure during construction, only a few have managed to capture statistics that provide evidence that underground utility damage has been reduced by their interventions. 

  • In North America every state and most provinces have enacted one call legislation. The Common Ground Alliance (CGA) has been collecting voluntarily submitted statistics on underground utility damage in North America since 2003.  The latest CGA DIRT Report for 2018 concluded that progress in the U.S. in reducing damages has plateaued. Total damages in the U.S. increased from 439,000 in 2017 to 509,000 in 2018, representing a 16% increase. Damages per 1,000 one call information requests increased by 11%, from 1.87 to 2.08, and damages per million dollars of construction spending (2017 constant dollars) also increased from 0.359 to 0.392.

  • Statistics on incidents of underground utility damage from the Ontario Regional Common Ground Alliance (ORCGA) 2018 DIRT Report reveals that the damage ratio - number of incidents per 1000 notifications - decreased from 2007 through 2014, but since 2014 the trend has been gradually increasing.

  • The Dutch one call KLIC system is very efficient, able to produce digital maps of underground infrastructure within a day of a request from an excavator. But there are over 41,000 incidents of utility damage every year in the Netherlands and there is no sign that this is decreasing.

  • The Pipeline and Hazardous Materials Safety Administration (PHMSA) which is responsible for gas and hazardous liquids pipelines in the United States has implemented programs to reduce incidents involving underground pipelines including during construction. PHMSA’s statistics are considered reliable because incident reporting is mandatory. In spite of the regulations implemented by PHMSA to improve pipeline safety, PHMSA’s statistics have not revealed a trend toward a reduction in pipeline incidents including those attributed to excavation damage.

Two jurisdictions where historical statistics reveal a reduction in annual incidents are Japan and Heathrow International Airport. For example, service strikes (accidentally hitting a utility cable or pipe) due to inaccurate information about underground infrastructure have declined at Heathrow by a factor of 6 since 2002 while total construction activity increased significantly. In both Japan and Heathrow a comprehensive multi-faceted approach was adopted that included policies, regulation, changes to construction practices, and new technologies.  These are described in detail in the white paper.

In the last few years several jurisdictions recognizing the importance of complete, accurate and up-to-date location data about underground infrastructure have initiated innovative programs related to data about the underground.  In 2019 legislation in Colorado mandated a subsurface utility engineering (SUE) survey prior to engineering design for public civil construction projects to reduce unnecessary and expensive relocations of utilities. It also required that network operators improve the quality of the information they maintain on the location of their underground infrastructure and provided civil penalties for submitting inaccurate as-builts.  Also groundbreaking is Colorado's legislation and regulation that mandates mapping natural gas gathering and flow lines and making this information open to the public via a web portal.  In 2017 the Singapore Land Authority (SLA), Singapore-ETH Centre, and the Geomatics Department of the City of Zürich started the Digital Underground project, a comprehensive program of technologies, policies, and processes for achieving and maintaining an accurate, current, and complete map of subsurface utilities in Singapore.   In the UK one of the first projects of the recently created Geospatial Commission is an initiative leading to the creation of a National Underground Assets Register (NUAR) for sharing location information about underground utilities among network operators and government. Two pilots in the North East and in Central London have been completed. The project is moving forward with plans to mandate sharing of location information about underground infrastructure at the national level. In 2015 the Netherlands mandated a national system for sharing underground geotechnical information exposed through boreholes and other digging techniques. On 1 January 2018, it became mandatory to report the first three data types, geotechnical surveys (CPT), groundwater monitoring wells and soil drilling sample profiles. In June 2018, this data became publicly available via the Dutch open data portal PDOK.  Work is underway to implement data models for the remaining 23 data types. 

Based on a review of many international initiatives to develop programs for underground infrastructure information, a set of 25 recommended elements have been compiled that organizations and jurisdictions including national, state/provincial and municipal are using to address the challenge of damage to underground infrastructure. These can be grouped into broad categories.

  • Reliable statistics on underground utility damage.

  • Taking advantage of the latest technical advances in underground utility detection and mapping.

  • Policies, procedures, and technologies for raising the level of accuracy, timeliness and completeness of information about the location of new and existing underground infrastructure. Specifically, the objective should be a maintained 3D model of underground infrastructure supported by a program of continuing quality improvement.

  • More sustainable design for underground infrastructure.  For example, avoiding sharp bends in pipes and ducts and including technologies for making utilities easier to track such as tracer wires and marker balls.   

  • High degree of collaboration between network operators, consulting engineers, contractors and project owners.        

  • Digitalizing the capture, sharing and updating of location information about     underground infrastructure.  This includes either a single physical database maintained through ETL processes or a federated database combining multiple physical databases each curated by a network operator. A single map of all underground infrastructure including utilities, telecom and unknown and abandoned equipment is provided via a browser or handheld device.

  • Data protection of location information about underground networks including security, privacy and protection for competitive information. This rests on three pillars; a legal framework of agreements with data providers, security technology, and trust among data providers, data brokers, and data users.

  • Providing access by stakeholders to underground infrastructure location information throughout the construction project life-cycle beginning with a SUE survey prior to engineering design which is accessible by planners, engineers/designers, construction contractors and those responsible for operations and maintenance.

  • Liability model for sharing responsibility for costs associated with underground utility damage.  This includes the costs of improving location information about underground infrastructure.

  • Training and education Ensuring that those involved in the detection, locating, and mapping of underground infrastructure are trained in the appropriate technologies and techniques to ensure completeness, accuracy and currency in the data they collect and manage.

  • A viable business model to maintain adequate funding for the program.

The Japanese and Heathrow experience have shown that to successfully reduce utility damage requires a comprehensive approach that implements most, but not necessarily all, of these recommendations.  A successful program for reducing underground utility damage requires the involvement of many stakeholders including network owners and operators, planners, surveyors, SUE engineers, design engineers, construction contractors, regulators and government agencies such as MOTs/DOTs need to be involved.  The goal is to reduce the risk of utility damage over the lifecycle of infrastructure from planning through operations and maintenance. A successful program not only reduces underground utility damage and the associated costs, injuries and fatalities and results in more projects on-time and on-budget, but also significantly reduces the cost of infrastructure construction and maintenance.  Additionally there are significant benefits for the construction industry. For example, reducing risk reduces insurance costs for an industry where margins are very low. Furthermore, developing and maintaining an accurate 3D map of underground infrastructure has potential benefits for other use cases beyond construction such as utility outage management, disaster planning, emergency response, urban digital twins and smart cities.


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Matt Chester's picture
Matt Chester on Apr 16, 2020

Thanks for sharing, Geoff-- some fascinating insights and obviously an important issue. For utilities who haven't yet fully embraced the potential digital solutions to underground mapping for these purposes, what types of tools do you recommend for them to utilize to really get started?

Geoff Zeiss's picture

Thank Geoff for the Post!

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