Ground investigation (GI) work is routinely carried out to assess ground conditions and identify ground hazards prior to the construction of new buildings and infrastructure projects. The UK construction sector invests approximately Â£1.2 billion per year in GI, yet unforeseen ground conditions still cause significant delays and overspend, estimated at 10 per cent of project costs or £120 million per year.

Additional funding has been secured from the  to expand BGS pioneering Common Ground project. This initiative aims to develop a national geotechnical properties data service, maximising the return on GI investment and reducing risk, increasing efficiency and unlocking the value of GI data for the UK construction sector. 

Following the success of the project first phase, the new funding will enable BGS to build on pilot geotechnical data tools that were developed for Glasgow to deliver a national-scale geotechnical data service that combines geotechnical data with geological knowledge.

As BGS moves forward with this exciting phase, we remaincommitted to delivering solutions that maximise the return on investment in GI data, reduce carbon emissions and support a more resilient and efficient construction industry.

Alison Steven, data operations and governance manager at BGS.

Ensuring that users remain at the heart of product development, our partners, , will be conducting further market research and will develop a strategy to help BGS provide an authoritative data service with the functionality that suits the end user. 

The knowledge asset underpinning this project, the 51ÁÔÆæ National Geotechnical Properties Database (NGPD), contains data from approximately 200 000 boreholes, consolidated, validated and verified by BGS experts.

If you are a user or producer of GI data and would like to be involved in the project please get in touch with the Common Ground team.

Every city has a story hidden beneath its surface, shaped not just by people but by ancient landscapes and geological forces too. Under our streets, buildings and parks lies an unseen subsurface that has a major influence on how our cities function, grow and adapt.

On World Cities Day, we are highlighting urban geoscience — the study of the ground beneath our towns and cities — and why understanding this hidden world is essential for building safer and more resilient urban environments.

What is urban geoscience?

Urban geoscience helps us to understand the geology and both the natural (for example, ancient river valleys and glacial deposits) and human-made features (for example, old mine workings) beneath our cities. This knowledge helps planners and decision makers to more safely utilise the subsurface — for example, for water, energy and — while avoiding any challenges caused by the complex and sometimes unpredictable geology beneath our feet. As cities develop, urban geoscience offers the insight needed to mitigate risk and plan with confidence.

Examples of how British cities are influenced by geology

There are countless ways in which geology influences the evolution of our towns and cities. Here are four examples from around Britain.

London: shrink–swell clay and the changing climate

Much of London is built on the . This unit has clay-rich deposits that expand when wet and shrinks when dry, a phenomenon known as shrink–swell. This movement can cause cracks in buildings, damage roads and disrupt underground utilities.

With climate change, hotter and drier summers followed by intense rainfall are worsening the effects of shrink–swell. The 51ÁÔÆæ GeoClimate dataset models how these risks may change over time, showing areas most likely to experience future subsidence. Such modelling can allow for preventative or mitigative steps to be put in place to alleviate the effects of the hazard on property and infrastructure.

Glasgow: mining and geothermal energy

Glasgow sits on the Carboniferous-aged and the coal mined from beneath the city powered its industrial growth. The old mine workings have left voids in the subsurface that can collapse and, if the collapse is close to the surface, cause subsidence. However, if potential issues are known, preventative measures can be put in place to reduce the risk.

The 51ÁÔÆæ Mining Hazard dataset helps identify areas where past underground mining might pose a risk, supporting safer planning and development. Old mine workings are also providing new opportunities as warm water in flooded mine workings can be used to supply low-carbon heat and hot water to offices and homes, turning a legacy of coal mining into a .

Truro: radon risk from granite

Truro in Cornwall is a city built on Carboniferous to Permian-aged granite intrusions, which were formed when molten rock slowly cooled deep underground. Granite contains small amounts of the radioactive element uranium, which naturally breaks down (via a series of intermediate, unstable elements) over millions of years to produce radioactive .

In enclosed spaces like homes and offices, radon may build up to levels that pose a health risk, with prolonged exposure to elevated levels of radon increasing the risk of lung cancer. For most people, the risk of developing lung cancer from exposure to radon remains low. However, the advises you to test your home if you live or work in a radon affected area and there are several methods of reducing high radon levels in buildings.

Cornwall is just one of several areas around the UK were radon gas needs to be considered. The 51ÁÔÆæ/UKHSA Radon Potential dataset shows where elevated radon levels are most likely, showing where testing and mitigation are needed around the UK to make homes safer.

Cardiff: complex ground and urban redevelopment

The combination of river sands and gravels, glacial deposits and rocks of the Triassic-aged beneath the city of Cardiff affect drainage, groundwater flow and how easily the ground can be built on. As the city continues to grow and redevelop, understanding the subsurface is key for managing groundwater, avoiding subsidence and planning safe infrastructure.

The 51ÁÔÆæ 3D urban geology model for Cardiff helps to visualise the deposits beneath the city, while the 51ÁÔÆæ Civils dataset provides practical information on ground stability, excavation difficulty and chemical risks to construction materials.

Every city around the world is shaped or influenced to some degree by the rocks that lie beneath its foundations, a changing coastline along its shore or the risks posed by geohazards such as earthquakes, landslides or radon. As cities continue to grow and face new challenges, from a need to become climate resilient to an increasingly crowded subsurface, understanding the ground beneath them becomes more important than ever.

Urban geoscience connects the past with the present, helping us build cities that are not only functional but also resilient.

51ÁÔÆæ first-of-its-kind online tool, , predicts which roads create the most run-off pollutants and how road pollution can be tackled with nature-based solutions. The tool helps local authorities to prioritise water-quality improvement interventions at roads where major road run-off pollution is occurring and in the greenspaces that lie between the roads and the rivers. It is now being extended to estimate the number of pollutants, including fertilisers and pesticides, that are transported into rivers in rural areas.

°Õ³ó±ðÌýfirst online map was launched in 2023 in Londonand was partly funded by the Mayor of London, Transport for London (TfL) and the Environment Agency. It now highlights more than 280 miles (450km) of the capital roads that have a higher risk of road run-off pollution. In total, the tool now covers roughly 3862.3 km (2400 miles or 10 per cent) of London major roads.

What causes the pollution?

Fertilisers, pesticides and animal waste in rural areas can run off into rivers, introducing chemicals and excess nutrients that can cause algal blooms, depleting oxygen and harming aquatic life. Similarly, run-off from roads can carry oil, heavy metals and other toxic substances into waterways, contaminating the water and affecting ecosystems. These pollutants not only harm wildlife but also threaten the quality of drinking water for communities.

How does the tool work?

The tool combines pollutant emission factors, local rainfall conditions, surface area and the make-up of traffic on particular routes, using official data to predict where pollution hotspots are likely to occur. Results are shown on an interactive map. The tool then suggests potential nature-based solutions, such as wetlands, ponds and rain gardens, alongside roads to manage pollution before the water discharges into streams or rivers.

The new, expanded tool

The expanded tool will be tested across the catchment of the upper River Thames, above Dorchester-on-Thames. This area is predominantly covered by arable crops and grassland, but it has varied geology and soils that affect the movement of water and pollutants through the landscape. It also includes urban areas and sections of the M4 and M40 motorways, which generate pollution in road run-off.

The project, which is funded by the Government Office for Technology Transfer, will last for 18 months.

The Road Pollution Solutions Tool, which was only launched just over a year ago, is already showing just how beneficial it is in highlighting which roads in London are at risk of road run-off pollution.
Expanding this tool further to include an integrated assessment of agricultural pollution risks means that we can assess these pollution sources and explore what can be done to reduce them.

Chris Jackson, head of BGS Environmental Modelling.

Road Pollution Solutions is built on years of research by environmental charity and its partner , as well as the . The charity started its initial road runoff project identifying key polluting London roads in 2019, with funding help from the , and the .

The ground beneath our cities and towns is becoming increasingly important in a number of sectors. This is not only due to pressures from housing, transport, and utility infrastructure, but also from optimising the use of natural resources such as groundwater and heat.

The Urban Interactive 3D models tool, hosted within BGS GeoIndex (onshore), was launched as a free to view service in 2021. It already includes conceptual models of London and the Thames valley, Cardiff, and the greater Glasgow region; now, a model featuring Liverpool and Warrington has also been made available.

The tool provides a 3D characterisation of the rocks and deposits beneath the area that make up the upper tens to hundreds of metres of the below ground. This data provides a vital understanding of where certain geology is and can assist different sectors in their planning within urban areas. For example, it gives a heads-up to local authorities and engineering consultancies of where they should consider the management of groundwater, and identifies potential geological resources, such as geothermal energy, when it comes to the planning and development of the area.

The BGS are striving to synthesise all the 3D geological model stock it holds into easily accessible and usable information. We hope that by providing this data, users can get an appreciation of the types of soil and rocks they live on and work with.

Ricky Terrington, Geospatial Data and Technologies Lead at BGS

Further information

• 3D urban geology, including further information about the Liverpool model
• (video)

Contact

For more information, please contact 51ÁÔÆæ press (bgspress@bgs.ac.uk) or call 07790 607 010.

51ÁÔÆæ and The Geological Society of London have accepted an invitation from the Government Office for Science (GO-Science) to launch a new network after its report, ‘’, called for improved cross-sectoral work to address future issues.

The network, ‘Future of the Subsurface Community of Interest’, is set to be a community of decision makers from Government departments, local authorities, regulators and others in the public sector involved in subsurface policy and planning. It will serve as a forum for exchanging knowledge on subsurface issues to improve coordination and regulation and allow more effective management of the subsurface and the services it provides.

Use of the subsurface has been vital to people for thousands of years. The availability of subsurface resources, such as water, fertile soil and building materials, has long influenced where we choose to live. The UK diverse geology also plays a significant role in shaping its landscape and influences various aspects of land use, planning and society.

The subsurface is a natural space for the infrastructure that underpins society. We have developed methods to use and exploit the subsurface in a multitude of different ways, such as for natural resources and space for infrastructure, which deliver a range of societal benefits.

The Foresight study not only highlights the future need for the subsurface to deliver net zero technologies and climate adaptation measures; it also emphasises the challenge of implementing cross-sectoral solutions and the issue of incomplete and inconsistent regulation, which limit future options.

We will work alongside The Geological Society to ensure that we fulfil the need highlighted in the report, to facilitate a shared understand across decision makers of the value of the subsurface for the long-term public good.

Stephanie Bricker, head of urban geoscience and spatial planning, BGS

Informed and effective public policy relies on access to timely, digestible and relevant scientific evidence. By working with the 51ÁÔÆæ to facilitate this Community of Interest, we aspire to support those working across the breadth of subsurface policy and planning to engage with the best available geoscience and promote informed decision making.

Dr Megan O’Donnell, head of policy and communications at The Geological Society

Find out more about Go-Science report, the Future of the Subsurface Foresight.

Contact
For enquiries about the Community of Interest please contact FutureSubsurface@bgs.ac.uk

For media enquiries, please contact the BGS Press Office (bgspress@bgs.ac.uk) or call 07790 607 010.

European policy is clear in its ambition to deliver a sustainable urban future for Europe. This research, led by BGS and the EuroGeoSurveys’ Urban Geology Expert Group, considers the role of urban geoscience in helping to achieve these ambitions by highlighting the relevance of geology to urban subsurface planning and wider policy.

Despite the lack of explicit reference to urban underground or subsurface space in key policy documents, the research identifies a significant number of priority urban issues for which geological characterisation is a pre-requisite (such as mitigation of climate impacts and delivering net zero energy) and where implementing nature-based solutions forms part of the answer.

Urban future

By 2050, it is likely that humanity will have become a predominantly urban species, with 70 per cent of the global population expected to be living in cities and the surrounding urban sprawl (International Organization for Migration, 2015).

Whilst cities deliver economic benefits, high urban populations place extreme pressures on land, the environment and natural resources, and are major contributors to climate change (Smith and Bricker, 2021). Urban centres only cover approximately 3 per cent of the land surface, but they account for more than 70 per cent of energy consumption and 75 per cent of carbon emissions (Smith and Bricker, 2021). The impact of urbanisation, therefore, extends far beyond its physical footprint.

Although cities are part of the problem, as centres of innovation, knowledge, and economic prosperity, they must also be a solution. Global programmes, including the (SDGs), recognise the role of cities in delivering climate targets and sustainable approaches. These global ambitions are also adopted at a European level, through, for example:

Urban geoscience establishes the need for city masterplans to include geological considerations, including hazard management, use of natural resources and nature-based solutions. These draw on a range of disciplines such as engineering geology, hydrogeology and environmental geology, and utilise a range of technologies such as geological modelling and remote sensing.

Urban strategies for subsurface management

One of the primary routes to embed subsurface information in city decision making is the development of underground masterplans and supplementary planning guidance for subsurface land uses.

Approaches to subsurface governance vary between countries; some focus on land-use zoning to protect future subsurface development, for example for future transport infrastructure, which is achieved through national planning policy. Others aim to protect rights to underground resources, such as water, minerals, oil and gas, through environmental regulation. The national-level approach to subsurface governance ultimately dictates the extent to which geological information is included within the planning process.

European policies

A review of some key European urban and environmental policies and strategies has been undertaken as part of this research, to assess the extent to which urban geoscience issues and opportunities are represented at a policy level. Even though the urban subsurface environment is not explicitly referenced and there is no direct mention of the role of geology, urban geosciences can make positive contributions to five key challenges:

• sustainable use of land
• climate impacts and mitigation
• transition to net zero energy
• implementation of nature-based solutions
• clean water

This research provides a unique perspective on recent advances in urban geoscience across Europe and, reassuringly, we see a strong line of sight between the research directions and policy needs. However, the dependencies between the policy objectives and geological context are far easier for the geologist to discern. The benefit of the EuroGeoSurveys’ Urban Geology Expert Group is that we are developing a cohort of scientists who are happy working across geological disciplines and at the boundary of their science to provide more innovative and collaborative solutions that speak to the needs of urban practitioners. We recognise that geology is only one piece of the puzzle for a sustainable urban future.

Stephanie Bricker, head of urban geoscience and spatial planning at BGS.

An evolving science

The urban geoscience discipline is successfully evolving to deliver integrated urban science in response to these policy aims. We see a strong alignment between the policy themes and the current urban pressures and research priorities identified by urban geoscientists across Europe geological surveys.

The review of urban geoscience research priorities also shows that the discipline is broadening to embrace wider geo-environmental specialisms, including geothermal expertise, geo-data and informatics, geoheritage and science policy.

Demonstrating the value of urban geoscience for different urban challenges is a future priority. It is important for the recruitment of influential stakeholders in terms of, for example:

• the value of geological data for urban development
• demonstrating the multiple benefits of nature-based solutions
• risk reduction in hazardous urban environments

As one of the more accessible geological disciplines, urban geoscience even has a role in broader geological knowledge creation in aligned non-geological organisations, and in improving diversity within geological communities.

The role of the urban geoscientist as an agent of change to enhance integrated science, improve the accessibility of geological issues and accelerate the translation of national or regional geology to local settings and to urban policy drivers should not be underestimated.

Urban geology has rapidly evolved from an emerging field to one that is becoming increasingly recognised as crucial to bridge the divides between the many sectors that meet in the urban subsurface – underground infrastructure, energy systems, transport, geological storage, geoheritage, waste management, groundwater and soil health, natural and human-induced hazards. Increasing urbanisation coupled with climate change impacts will increasingly weigh on competing uses of the urban subsurface. Because of these competing uses, urban geologists play a key role in our ability to plan for future sustainable, climate-resilient cities.

Julie Hollis, secretary general at EuroGeoSurveys.

Further reading

The full report: .

More information

This magnificent, space-ship-like Victorian Gothic monument is a tribute to one of Scotland finest writers, Sir Walter Scott, and also happens to be one of my favourite stone-built structures.

This monument holds a special place in my heart. I first arrived in Edinburgh on my birthday, back in October 2000. As I stepped off the bus, this monument stood before me, black against the hazy grey backdrop of the Old Town. An instant confirmation that I was in the right place to fulfil my stone conservation dream.

Conservation work on this particular structure happened prior to my arrival in Edinburgh, however I have climbed the narrow 287-step spiral stair case to the top on many occasions to understand more about the author and the monument itself.

There is much to be learned from its 183-year history.

A masterpiece that came with a price beyond money

The Scott Monument is amongst the most important monuments in Edinburgh and possibly one of Scotland most significant. At 200 feet tall (almost 61 m), it is currently the second largest monument to a writer in the world. The monument design and construction (between 1840 and1844) were led by the talented joiner and self-taught architect, George Meikle Kemp, who anonymously entered the competition to design the monument. Tragically, he drowned in the Union Canal before the monument completion.

The ornate design required intensive stone carving: apart from the structure itself, there are sixty-four statues, primarily featuring characters from Scott novels. Unfortunately, it has been reported that as many as 23 of the 70 stonemasons died of silicosis during, or shortly after, the monument construction. In those days, the toll taken by quarrying and stone-building was intensive ( well worth your time) and young men who began to work as stonemasons in their teens rarely lived to reach 35. In this respect, the monument can be viewed as a much of a homage to stone, architecture and the skill of the architect, quarriers, masons and craftsmen who created it, as to Walter Scott himself.  It also a tribute to sound conservation decisions, which is where I would like to focus next in this spotlight.

The stone

The pristine white stone for Scott statue was carved out of a single 30-ton block of marble by Sir John Steell, sculptor of many other statues around Edinburgh. The marble was sourced from the famous Carrara marble quarries in Italy, which also produced the marble Michelangelo carved. These quarries are still active and supplying the revered marble to this day.

There is a lot of information available for those interested to read more about Carrara marble, so I would instead like to focus on the sandstone used for the bulk of the monument. This stone was sourced locally from Binny Quarry, near Ecclesmachan in West Lothian, which also supplied lots of stone to many other buildings in Edinburgh, such as the National Gallery.

By 1855, the rock extracted at the quarry already had a strong reputation as a building stone due to its durability, the relative ease of work and its desirable appearance.

This building stone has been classified by BGS as  and we hold various historical samples in our BGS Building Stone Collections. The samples range in colour from very light grey to brownish-grey, and brown when freshly quarried. Weathered samples from buildings tend to appear browner, but the stone can be very brown even fresh, as the sample bottom-right in the image attests.

The sandstone is generally fine to medium-grained, with relatively large muscovite mica flakes visible, clearly indicating the bedding. The mica content is variable across the whole range of samples, yet ever present and characteristic.

Under the microscope, it is a very quartz-rich sandstone (defined as a quartz-arenite), with a very small percentage of feldspar and rock fragments. Minor iron oxides/hydroxides exist. Relatively abundant mica flakes exist and are well aligned, indicating the bedding. Importantly, the grains are well cemented by a continuous coating of silica cement, making the stone rather durable. The total porosity is around 10 to 15 per cent, which is towards the medium to low end of Scottish Carboniferous sandstones. One of the stone most important characteristics (and a reasonably uncommon one, for a Scottish building stone), is its hydrocarbon content, which contributes to its brownish colour and other interesting properties, scattered as minute particles within its pore system.

As the stone weathers, the brown colour intensifies as part of the hydrocarbons (and some of the iron content) mobilise and migrate to the surface of the stone. Allegedly, because of this hydrocarbon content, it seems that smog pollution (fly-ash particles product from coal combustion, dust, etc.) sticks easily (and faster) to this stone than in other sandstones used in Edinburgh at the time, blackening its surface. However, this could also be attributed to the monument location between the train station (old trains released a lot of smoke) and Princes Street.

One of my predecessors at BGS, Dr Tait, noticed in 1932 that ‘the replacement of water by small amounts of oil in the pores between grains contributed to the durability of the stone.’ These oils make the stone even less permeable than it may seem, due to their water-repellent qualities. In general, most of our fresh samples have a surprisingly lower permeability than you would initially expect by looking at comparable Scottish sandstone, or the sample thin section (10 to 15 per cent porosity). Not all samples have the same permeability though and, from a small sample of drop tests I conducted, it seems that the browner the sample, the more the water ‘beads up’ and does not penetrate through the porous system of the stone.

Conservation

Having admired the Sir Walter Scott Memorial for years, I have followed the evolution  of the monument conservation efforts with interest.

Prior to the 1990s, sandstone from Clashach Quarry was used as a replacement building stone for the monument, a reasonably appropriate choice given the scarcity of quarries at the time. Between 1997 and 1999, a £1.4 million, multifaceted conservation plan was prepared and executed. It was decided that the monument current stones should be conserved, with the possibility of cleaning them. Photogrammetry was used to survey the monument and create detailed architectural drawings.

To clean, or not to clean … that is the question!

I am often asked why the monument was not cleaned, a question I myself had posed many years ago to a professor at the University of Edinburgh. He said that the question of cleaning or not cleaning the monument had been the source of much debate. Before making such a decision and, as it should be in any project involving stone cleaning, various test panels were carried out. The results of this test can still be seen on the south side of the monument today, with each panel cleaned using different methods and strengths of application. When you look at them, you can see how one of those methods removed the crust of pollution, but somehow managed to keep a thin patina, which in some ways respects the age of the monument. Other methods left the stone absolutely clean, still keeping the original brownish colour of the stone, whilst some methods appear to have altered the colour of the stone slightly to varying degrees.

The difference in outcomes across the test panels can be clearly seen in the images. The decision of what constitutes a ‘successful’ cleaning approach is partly a philosophical (and personal) one, as cleaner does not necessarily equate to better in terms of respecting the monument age and character. There is also an inherent risk of damaging the stone. It is reassuring, however, that twenty-five years after the cleaning tests, the test panels do not show any visual evidence of damage, which shows both the care with which this work was undertaken, as well as the durability of this particular stone. I would love to put my eyes, magnifying lens and nose close to those panels whilst holding information of which cleaning method was employed on each. There would be so much to learn!   

One final reflection about these panels is that, a quarter of a century later, they do not appear to be much dirtier, which indicates how much cleaner the air we breathe is today compared to when the monument was built.

It is believed that the architect chose that particular stone because he knew that it would quickly turn black, and was therefore part of the monuments’ design, providing a more ‘gothic’ appearance and striking contrast with the white of the marble statue. As the stone was not suffering deterioration caused directly by the crust of soiling and pollution, the team of conservation architects, stone conservators and academics, in agreement with the heritage groups ultimately decided against cleaning the monument. They concluded that cleaning it would be disrespectful to the memory and intentions of the original architect and that cleaning it was ultimately not worth the risk of damaging the stone. I believe this was a wise ‘minimal intervention’ conservation decision.

Rocking the golf course

The conservation of the building has been carefully considered in other ways too. When it came to restoring damaged stone blocks, sculptures and other carvings, stone need to be sourced from the original quarry. By this time however, the site was in use as a golf course. The site was temporarily re-excavated for this project, with sufficient stone extracted and stored for future repairs (allegedly in the underground vaults of the monument) and the quarry was restored back to a golf course, which it remains to this day.

That wider vision about managing resources responsibly is what conservation should be about. Safeguarding sources of important stone, applying sound conservation practice and using locally sourced materials to minimise impact on the environment in addition to boosting local employment. It’s a win-win situation from every point of view.

Closing thoughts

Conservation of building stones is an ongoing process and, maybe one day in my old age, I will have a chance to get involved in further efforts aimed at the preservation of this iconic structure. Thanks to the excellent sourcing of the stone, the skill of the original craftsmen and the valuable conservation efforts that have come before, the Scott Monument is in good health. I hope that this continues well beyond my lifetime.

Further information

About the author