Ground Stability Assessments

Ground stability assessment: achieve a rapid condition discharge

What is ground stability?

Ground stability refers to the ability of the ground to remain structurally sound and not undergo movement, such as subsidence, landslides, or settlement, that could impact buildings, infrastructure, and natural landscapes.

The stability of the ground depends on various geological, hydrological, and human-induced factors. Issues such as soil composition, groundwater levels, historical coal mining activity, and natural subsidence hazards all contribute to ground stability concerns.

What is a Ground Stability Assessment?

A ground stability assessment is an evaluation of the potential risks associated with ground stability issues. This assessment examines geological conditions, previous land use, and environmental factors to determine whether an area is prone to ground movement. The findings of the assessment inform construction and development plans to ensure safety and compliance with relevant regulations.

A ground stability assessment is carried out by a geo-environmental consultant and typically involves desk-based research using geological maps and data. Natural hazards will be taken into account and a site investigation may be followed by geotechnical investigations such as borehole drilling and soil testing. The necessary data is complied into a ground stability report. In cases where significant risks are identified, mitigation measures may be recommended, such as soil reinforcement, drainage improvements, or foundation modifications.

Why is a Ground Stability Report needed?

Ground stability assessments are crucial for several reasons:

1. Safety and structural integrity. Assessing ground stability issues helps prevent damage to buildings, roads, and infrastructure due to subsidence, landslides, or other ground movements.
2. Regulatory compliance. Many planning authorities require ground stability assessments as part of the development approval process to ensure construction projects adhere to safety regulations.
3. Risk management. Identifying potential ground stability issues in advance helps mitigate financial and legal risks associated with property damage or liability claims.
4. Environmental protection. Ground instability assessments contribute to sustainable land use by identifying areas at risk of erosion, flooding, or subsidence and suggesting appropriate mitigation measures.

When is a Ground Stability Assessment needed?

A ground stability assessment is typically required in the following scenarios:

• Applications for planning permission: Local planning authorities may require a ground stability report before granting permission for new developments, particularly in areas with known ground instability risks.
• Infrastructure projects: Large-scale infrastructure projects, such as roads, bridges, and tunnels, require stability assessments to ensure long-term structural integrity.
• Property purchases:  Homebuyers and investors often commission assessments when purchasing properties in areas with potential subsidence or historic coal mining activity.
• Post-mining and brownfield sites: Areas with a history of mine entries or industrial use require thorough assessments to determine potential subsidence risks before redevelopment.
• Natural subsidence areas: Locations prone to natural subsidence hazards, such as karst landscapes, clay-rich soils, running sand or coastal erosion zones, require stability assessments for any significant construction.

Types of Ground Stability Assessments

There are several types of ground stability assessments, depending on the specific risks and requirements:

• Preliminary desk study:  Utilises geological data, historical records, and environmental databases (such as British Geological Survey and Coal Authority data) to identify potential risks including natural hazards.
• Site investigation reports: Involves a site visit and inspection, borehole drilling, soil sampling, and laboratory analysis to assess ground conditions in detail.
• Geotechnical surveys: Provides in-depth engineering analysis, including soil mechanics, groundwater monitoring, and stability modelling.
• Mining subsidence assessments: Focuses on assessing risks in former metal and coal mining areas, using data from the Coal Authority and the Mining Redemption Authority.
• Landslide risk assessments: Examines slope instability and terrain stability in regions prone to landslides. The slope stability analysis uses geotechnical and hydrological data.

Is a Ground Stability Assessment mandatory?

The requirement for a ground stability assessment depends on location, land history, and development type. In the UK, planning authorities often require stability assessments for developments in high-risk areas, such as former mining sites or regions prone to natural subsidence. While not universally mandatory, assessments are strongly recommended for due diligence, particularly when acquiring land or property.

Land instability and the planning system

The UK planning system recognises land stability as a key factor in sustainable development. The National Planning Policy Framework emphasises the importance of considering ground stability risks in planning decisions. Local planning authorities must ensure that proposed developments do not increase risks related to land instability and that appropriate mitigation measures are in place.

Natural hazards

Several natural geological factors contribute to subsidence hazards in the UK, including:

• Clay shrinkage and swelling. Soils with high clay content expand and contract with moisture changes, leading to ground movement.
• Karst landscapes. Dissolving bedrock in areas of soluble rock such as limestone and chalk may develop natural cavities or sinkholes.
• Peat shrinkage. Peatland areas can experience ground subsidence as organic material decomposes and compacts.
• Landslides and coastal erosion. Steep terrain and unstable coastal regions are susceptible to slope instability and landslides, especially after heavy rainfall or human disturbances.

Who is responsible for land stability issues?

Responsibility for land stability varies depending on the specific circumstances:

• Property owners and developers have the primary responsibility to assess and mitigate ground stability risks before construction or land use changes.
• Local Planning Authorities ensure that applications for planning consent account for ground stability issues and impose necessary conditions on development.
• The British Geological Survey provides geological data and mapping resources to help identify ground stability risks.
• The Coal Authority offers guidance and detailed subsidence risk assessments for areas affected by past coal mining.
• The Mining Redemption Authority addresses stability issues related to historical mining operations and provides remediation measures.
• Environmental regulators may intervene in cases where collapsible ground poses significant environmental or public safety risks.

Assess potential risks from ground instability

Ground stability assessments are an essential part of land development, infrastructure planning, and property risk management. While not always legally required, they play a crucial role in ensuring safety, regulatory compliance, and long-term land use sustainability. Data from the British Geological Survey, Coal Authority, and Mining Redemption Authority provides valuable insights into ground stability issues, helping stakeholders make informed decisions about land use and development.

As land instability remains a significant concern in the planning system, proper assessment and mitigation strategies are vital to minimising risks and safeguarding future developments.

If you are concerned about a land instability issue or need to present a ground stability report with a planning application, the knowledgeable geo-environmental consultants at Arbtech can help. They cover the UK and are adept at carrying out these assessments. For further information, complete the contact form at the top of this page.