Underground mapping project: Going underground (Utilities special report)

Experts from universities across the UK are mapping the nation's ageing networks of utility pipes and cables to cut disruption caused by street works, writes project leader Chris Rogers from the University of Birmingham's department of civil engineering.

University engineers and computer scientists are hoping to put paid to unnecessary disruption caused by utility companies when they dig up roads and pavements by developing techniques to locate and map all of the cables and pipes buried beneath them.

The Mapping the Underworld project will pool information collected by engineers from Birmingham, Bath, Nottingham, Sheffield and Southampton universities, and computer scientists from Leeds University. This will be shared by the utility companies that own the buried service infrastructure, and those responsible for the highways and footpaths beneath which they are buried, in order to streamline street works.

There are millions of kilometres of underground cables and pipes beneath the streets - water distribution pipelines, sewers, gas pipelines, electricity, telecoms, traffic signals and drainage systems. An estimated four million holes are dug each year in UK highways and footpaths by utility companies so they can install new services or repair and maintain existing ones. A significant proportion of these holes, up to 25% according to some estimates, are what are termed dry holes - they fail to locate the buried service they are targeting.

Every time a hole is dug, there is a risk of damage to another utility's services and workers are exposed to the danger of striking live power cables. The risk is higher if the person doing the digging does not know what lies beneath the surface and where it is.

There is also the potential of long-term damage to road structures as more holes are dug, due to discontinuities in the bound layers around the edges of the patches and if reinstatement is imperfect. Unnecessary additional excavations should be avoided wherever possible.

The last effect is the disruption to road users caused by street works, which encompasses a range of issues including stress to drivers, diversions of heavy vehicles onto roads that are not suitable, increased incidence of accidents and traffic jams.

Buried assets
Many of today's buried assets were laid in Victorian times when recording details of location and depth was not a priority. Even if records were made, the reference points for measurements will probably be lost - kerb lines have probably moved and buildings might have been demolished and replaced. More pipelines and cables have since been laid and records exist in different formats, but few are compatible as there has never been a single, common standard for such data.

One of the sub-projects of Mapping the Underworld plans to create a common format for knowledge collation and sharing so the maps produced can be used effectively. This is where the computer scientists come in. The main focus of the Mapping the Underworld initiative is provided by the location and mapping sub-projects. The location sub-project plans to combine different technologies, notably ground-probing radar, acoustics and low-frequency electromagnetic fields (natural gravitational fields and those induced by electrical cables), into a single device.

The idea is that a combination of the outputs, together with an intelligent use of pertinent ground properties in the interpretation of the resulting data, will result in a far greater success at locating the buried infrastructure and may enable the buried objects to be identified. One reason for believing that this approach will be successful is that the technologies are complementary (ground-probing radar ceases to be effective over distances of 1m to 2m in saturated clay soils, whereas acoustic techniques favour such conditions but are less successful in partially saturated soils).

Once the location devices have been developed and proved, the data must be accurately positioned and mapped. Engineers at Nottingham University are seeking novel methods of improving GPS surveying techniques to improve accuracy, while also removing the blind areas in urban street canyons where visibility of satellites is compromised.

The final sub-project is being carried out by Oxford University and concerns the installation of RFID (radio frequency identification) tags on pipes that are newly installed or repaired so that workers can use hand-held devices to remotely interrogate from the ground surface the tags for information such as type of pipe and contents, date and method of installation or repair and reinstatement, and perhaps standards in force at the time the work was carried out. This addresses the question: 'What should we do now if we were starting again with buried utility operations?'

Work is underway on a parallel project at the University of Birmingham into technologies that will make the operation of buried assets more efficient. A research team, led by Dr David Chapman, is developing micro-sensors that can be embedded into the pipes at manufacturing.

Preventative maintenance
These sensors will be interrogated by electronic signals from a few metres away and will be configured to record information about the condition of the pipe or cable so that preventative maintenance can take place. For example, the sensors could be devised to register a physical or chemical signature, such as strain or chloride ion concentration, in relation to a trigger value that would indicate the pipeline is approaching failure. This two-pronged attack on the problem will seek to create smart location techniques and smart pipes that will tell us where they are and how they are feeling.

Figures suggest that the utility industry's annual direct construction costs associated with street works are £1.5bn, with third-party damage costs at about £150m, while the societal costs, such as delays to road users, environmental damage, disruption of businesses and air pollution, may be as high as £5.5bn a year. It is clear that the research, which is funded by the Engineering and Physical Sciences Research Council (£1m) and UK Water Industry Research (£200,000), has the potential to reduce the direct and indirect costs of street works associated with buried services.

Five workshops focusing on topics such as sensors, mapping technologies, knowledge integration and sharing, buried asset condition assessment and novel approaches to the provision of buried services are being held during the project. The workshops aim to present the latest findings of the research and to garner ideas on how it should be targeted and implemented from all interested stakeholders.

Anyone wishing to take part in a workshop should contact Nicole Metje (n.metje@bham.ac.uk).

Further information on the Mapping the Underworld project can be obtained from Chris Rogers at the University of Birmingham (c.d.f.rogers@bham.ac.uk).

[Contract Journal, 1 June 2006, p 14]