Many utility assets are buried, but exactly where they are and how they intersect with other infrastructure beneath the surface is unclear.

The vast web of buried infrastructure across the UK is a challenge for the utility sector. Against a backdrop of shifting policy expectations and regulatory uncertainty, utility suppliers are under pressure to maintain this underground asset base while demonstrating consistently high levels of efficiency, safety and service.

One of the key challenges for utilities tasked with managing buried assets is the dearth of accurate information about what is really going on below ground. Statutory records are often lacking reliable and up-to-date information, an issue made more problematic by the UK’s historic legacy of subterranean assets, from Roman sewers to Victorian drains.

Nicole Metje, a co-investigator of the Assessing the Underworld project, which is part of a 25-year initiative to make streetworks more sustainable, describes the maze of underground assets as chaotic. “We probably only accurately know where 50 per cent of our buried infrastructure is. Of the 50 per cent that we don’t know, it could be that they are only a few centimetres out or it could be metres out. That’s the background challenge that we’re facing,” she says.

“If you open the road or a junction and look at what’s there, it’s often a mess. It’s not just one pipe or one cable, they’re all crisscrossing. It’s basically a free-for-all in the underground space.”

Metje says the issue is exacerbated because there are no regulation guidelines: “There is advice from Street Works UK [formerly the National Joint Utilities Group] about how far you should put assets from the curb, what depth and how far depending on the type of asset. But often, a lot of that is not possible to do. Very few of our assets in the UK, and in a lot of countries, are laid in predefined trenches. They are just laid anywhere below the ground’s surface.”

Geophysical surveys

To repair, replace or lay new pipes and cables, it is crucial to have a comprehensive understanding of co-located assets. But with statutory records often falling short of the accuracy asset owners require, geophysical surveys can help to bridge the gap in knowledge of what is buried below ground. According to Metje, who is also a senior lecturer in the School of Civil Engineering at the University of Birmingham, the publication of PAS 128 in 2014 has had a major impact on the industry by improving the consistency of geophysical utility mapping.

“Pre-2014, people often said that there was no parity when companies were quoting for jobs because utility surveying meant different things to different people. For some it meant collecting statutory records, for some it meant doing geophysical surveying, and for others it meant doing trial excavations,” she explains. “Obviously, your tenders differ depending on what level you do, and the different levels give you different confidence in how accurately you can map the area.”

However, there is still a risk of uncertainty. Geophysical sensing technologies have their limitations, whether it’s an inability to always penetrate deep enough, or struggling to resolve stacked assets or assets that are too small.

Ultimately, for utility suppliers, the point of the exercise is ensuring the delivery of outstanding service, 24 hours a day, 365 days a year. For Bristol Water, this involves maintaining a network of almost 7,000km of water mains and services.

“If something fails or service levels are not met, it directly has an impact on individual customers,” says Frank van der Kleij, Bristol Water’s head of asset risk and planning. “As [our distribution network] is mainly situated below ground and the assets are quite diverse in terms of age, material and so on, it is challenging because you can’t maintain everything. It is about understanding what you need to maintain, ideally just before it starts failing because you need to be as proactive as possible. You want to avoid reactive issues.

“That’s one of the main issues moving forward: ensuring that when an underground asset is failing you can anticipate where and when that failure will happen. You can then mitigate that through an intervention before it fails or before it starts impacting customers.”

As part of Bristol Water’s drive to mitigate risks to its asset base, the company has developed a long-term burst mains model. “The prediction model gives you a good idea of what you need to do in terms of the level of intervention to ensure that you maintain bursts at an acceptable level. That gives you a high level understanding of how much investment you need to make in terms of asset failure intervention,” says van der Kleij.
However, the difficulty is knowing exactly where to invest resources at any one time.

That’s where you use other indicators, such as the work we are doing on increasing the number of sensors we have on the network,” he explains. “The sensors will give you early warnings where a potential asset can fail. There’s quite a lot of new technology on the market that can be used proactively to pick up very high levels of noise on the system, or pressure variations or flow, for example.

“By using all of these indicators together you get a good indication of where potential assets could be failing. You can then add other technologies, such as inserting cameras to really understand where it’s likely that your assets are going to fail first.”

Van der Kleij says it’s an exciting time for the industry with the rapid evolution of new technologies that can make systems smarter and allow asset owners to gain more insight into their underground network. One way he believes the industry can further generate innovation is by working more closely with manufacturers and universities.

“Manufacturers tend to be at the end of the process, but ideally you want to have innovation being generated through collaboration with industry manufacturers as well as academia. That allows you to tackle a number of different areas in ways that you can’t if you’re trying to tackle problems individually,” he says.

Over the past five years Bristol Water has been involved in a project with Imperial College London and valve manufacturer Cla-val. The ongoing initiative involves introducing the principle of adaptive and dynamically controlled network areas. Through the application of smart technology, the project aims to provide a more resilient and better performing network (see case study, below).

Assessing the Underworld

Collaboration between industry and academia has also been key to the success of the Assessing the Underworld (ATU) initiative. Working with 59 stakeholders from across the industry, ATU was a follow-on from Mapping the Underworld (MTU), which focused on mapping underground assets, pipes and cables. Subsequently, ATU looked at using some of the same technology explored in the MTU project, as well as new technologies, and ways they could be deployed differently to obtain condition information. “Basically,” says Metje, “can we detect leaks, can we detect corrosion, can we identify issues with broken or overheating cables?”

The project consisted of various workstreams including research into vibro-acoustics, electromagnetic detection techniques and non-contact electrical resistivity. The research also focused on geotechnical and road infrastructure. Part of this work looked at trench reinstatement and current standards for repairing and filling trenches, and what impact that has on road quality.

“We said from the outset that if you put a trench in, you’re also damaging and reducing the life of the road itself because you’re creating a flow path for water to go in. You’ve reduced the strength of the road and potentially the subsurface if you haven’t compacted it well enough,” explains Metje.

The trench field trial was undertaken on campus at the University of Birmingham. The team looked at the impact of reinstating a trench using the current BSI standard, but at two ends of the spectrum: the best you could do and the worst you could get away with under the standard. “We’ve had some interesting findings that show a poorly reinstated trench which is still within the BSI standard would actually be a lot worse and would deteriorate the road quite significantly,” claims Metje. “It is also likely to have an impact on the buried pipes which then in the longer term is likely to reduce the life of the buried asset.”

While the ATU research finished in May 2018, the team is now involved in various ­follow-on projects working with stakeholders to test some of the findings.

“We have got ideas for how we take some of the research forward and look much more into underground space and how we use that space. It’s broader than just utilities – we’re looking at basements, tunnels and so on,” says Metje. “We need to think differently about the whole underground space. And that’s including the surface up to about 50m. We don’t currently understand the value of this space and how this could support urban living by moving functions from above ground to below ground.”

Taking a more holistic view of the sub­terranean space will be critical as more regions across the UK seek to deliver “smarter” cities by disrupting conventional approaches to planning, maintenance and investment. Van der Kleij believes that as part of this holistic approach, there is the potential for assets owners to share more information, thus benefitting individual utilities and the entire network. “The challenge is that as individual organisations you work towards many different commitments, so it’s not always possible to work closely together,” he admits. “If we invested in a high level of assets in a certain area, it would be ideal to work in collaboration with all the other utilities that also have commitment in the network at that particular location so that you look at it collectively.”

Metje agrees that the way people live and operate in the cities of the future could hinge on successfully utilising the underground space as a holistic asset: “It’s not just about the underground infrastructure that’s already there, we need to treat the subsurface space as an asset which has enormous value, if only we can harness it.

“We need to really value this subsurface asset, not just for today but also looking forward. Assets in the ground nowadays have a life of 100-plus years… you really need to take a long-term view.

“Can you use the potential of the underground space to deliver far better city living? That’s what I think should be done, but not enough people think of that as a third dimension. They only look upwards and not downwards, thus neglecting the underground space and its enormous potential and value.”

While government and local authorities are urged to consider the underground space as a complete asset, utility suppliers should similarly consider their subterranean asset base and the co-ordination of co-located assets with increasingly joined-up thinking. The way in which underground asset investment is planned, delivered, monitored and maintained in the future must be approached with a holistic view of the subsurface space. Failure to do so will be a serious impediment to creating the smart, sustainable and resilient cities of the future.

Data challenges

Data sharing and the accuracy of data is a big challenge. In Holland, the Cadastre is a land registry and mapping agency responsible for national mapping and maintenance of the country’s reference co-ordinate system. Companies must record their buried infrastructure on the centralised system and the information is available predominately online.

In contrast, much of the UK’s data on underground assets is held individually by companies. However, it is important to note that there are far fewer utility providers in Holland. The proliferation of utility firms in the UK after privatisation has resulted in a system that is more fragmented, and ultimately more challenging when it comes to data sharing.

Case study: Creating resilient and dynamically adaptive water networks.

Frank van der Kleij, Head of asset risk and planning, Bristol Water

In the UK, water distribution networks (WDNs) have been sectorised into “static” discrete district meter areas (DMAs) mainly for leakage management. By installing kept-shut boundary valves to create DMAs, the redundancy of connectivity and supply within large interconnected networks is severely reduced, thereby affecting operational resilience, water quality, and energy losses. Although DMAs have contributed towards a step change in managing leakage over several decades, DMAs have introduced operational restrictions that affect both customers and utilities.

New technologies and systems-based approaches are needed to improve operational resilience, hydraulic pressure and assets utilisation within WDNs during a time of escalating environmental, regulatory and financial constraints.

The project involves the next generation of intelligent water distribution networks that dynamically adapt their connectivity and hydraulic conditions to deliver a notable improvement of the 4Rs of: resilience for networks: redundancy; reliability; resistance; and response and recovery. This is achieved by replacing the kept-shut boundary and control valves with multi-function self-powered automatic control valves, or multi-function network controllers (MFNCs). The MFNCs adaptively control the network connectivity and hydraulic conditions based on mathematical optimisation to switch between hydraulic states that are specific for pressure control, incident response, water quality control and leakage management.

This work followed concepts used in communication networks, where “software-defined networks” and physical routers significantly improve the quality of service through dynamic connectivity and network adaptability.

A demonstrator (field lab), operated by Bristol Water, was implemented in 2012 as a “playground” for the development and integration of modelling, optimisation methods, and control technologies. The field lab includes three dynamically adaptive DMAs, 7900 customer connections and 59km of mains.

The combined know how and experience of a utility, product manufacturer and a university working collaboratively has been instrumental to the success of this project. The integrated analytics and technology for dynamically adaptive networks is now mature and provides a significant step change in the way water distribution networks are managed in the UK.

Case study: HV solid cable prioritisation means replacing only those assets that are at risk of failure.

Maxi Faridi, Innovation engineer, UK Power ­Networks

We are committed to delivering a safe and reliable service to our 8.2 million customers at the lowest possible cost. Our networks in London, the South East and East of England span more than 140,000km of underground cables, some of which have been in service for many years. Our aim is to invest in these assets to maintain reliable supplies and keep costs down for our customers.

Sometimes it can be a challenge to understand exactly the cause of a cable fault on our network because several different factors such as environmental, electrical or mechanical issues all have an impact on life expectancy. Traditionally, age alone was used in determining when to proactively replace cables. More recently we’ve developed a proactive and methodical approach for prioritising investment based on their performance. In order to achieve this, we set out to understand more about the condition of high voltage (HV) underground cables and to develop an HV cable prioritisation model.

UK Power Networks’ innovation team has developed a tool for HV solid cables that can help us identify HV cables for early replacements before their failure. We carried out detailed studies on HV underground cables and the reasons they had failed. This work enabled us to develop a methodology that assesses the condition of an HV underground cable, and proactively replace underground HV cables before faults occur. We’re improving the reliability of the network and reducing disruption to customers by ensuring cable replacement is carried out at the right time. The HV solid cable prioritisation tool is now a key part of how we maintain a safe, reliable electricity network.