Cornwall’s stunning landscapes hide a complex and sometimes hazardous underground legacy. Whether you’re planning a new development, buying land, or renovating an existing property, understanding the region’s most common ground risks is essential. These are some of the common risks you may encounter in Cornwall and how our team investigates and manages them.
1. Mining Hazards
The Risk:
Cornwall is historically one of the UK’s most mined regions, especially for tin, copper, and arsenic. Many historic features remain undocumented. This could result in collapse, subsidence, or gassing risks.
How We Investigate:
- Desk top mine searches
- Walkover surveys to identify surface features
- Targeted intrusive investigations (via drilling or trenching)
- Footings inspections
2. Contaminated Land
The Risk:
Sites can be at risk from contaminated land due to their former use, a nearby contamination source or even from natural geology.
These may impact health, groundwater, and future land use.
How We Investigate:
- Phase 1 Environmental Desk Studies (historical use, planning data, site walkovers)
- Phase 2 Intrusive Investigations (soil sampling)
- Ground gas monitoring
- Conceptual site models (CSMs) and quantitative risk assessments revised at every phase.
- Liaison with the Environment Agency and local planning authorities
3. Unstable Ground and Complex Geology
The Risk:
Cornwall’s geology is varied with some sites encountering bedrock at ground level whereas others can be metres down and require a piled foundation solution. These differences in geology across the county can also affect the sites drainage capabilities.
How We Investigate:
- Geotechnical site investigations (trial pits, rotary drilling, window sampling)
- Laboratory testing (Particle Size Distribution, Atterberg limits, moisture content, etc.)
- CBR testing
- Infiltration and Percolation drainage testing
4. Ground Gas
The Risk:
Ground gas can be a risk to a site from on site or nearby landfills or infilled land. Ground gas can pose explosion or health risks, especially in poorly ventilated structures.
How We Investigate:
- Multi-point borehole installation for gas monitoring
- Long-term gas monitoring (methane, CO₂, VOCs, etc.)
- Classification of gas regime using CIRIA C665
- Gas specific remediation schemes
5. Flooding & Groundwater
The Risk:
Certain areas of Cornwall — particularly coastal or valley zones — are at risk of surface flooding or rising groundwater.
How We Investigate:
- Groundwater monitoring via standpipes or data loggers
- Infiltration testing (BRE 365)
- Percolation testing (BS 6297:2007+A1:2008)
- Review of EA flood zone mapping
- Preliminary Flood Risk Assessments
Every site is unique, but experience in the local geology and historical context is key. Whether you’re a developer, architect, landowner or planning consultant, understanding and addressing ground risks early can save thousands and protect your project from delay.
At Wheal Jane Consultancy, we’ve helped hundreds of clients across Cornwall and the wider South West build safely and sustainably. If you’re planning a project or just want to better understand your site, get in touch. consultancy@wheal-jane.co.uk or 01872 560200
