Contaminated land.

Why contamination matters.

Building Regulations require the ground under a building to be reasonably free from anything that could damage it, and councils commonly attach planning conditions requiring contamination to be investigated, and dealt with where needed, before work starts.

The Environment Agency's Land Contamination Risk Management (LCRM) guidance sets out how. Risk depends on a link between a source of contamination, a pathway and a receptor, such as people or groundwater. As LCRM puts it, without a linkage there is not a risk, even if a contaminant is present.

From history to evidence.

1. Desk study, often called Phase 1. The site's history, such as old industry, fill, landfill or mining, is used to judge whether there is a plausible risk.
2. Intrusive investigation, often called Phase 2. Soil, water and gas samples are taken from trial pits, window samples and boreholes, to confirm the picture either way.
3. Testing by laboratories accredited for chemical testing, under UKAS and MCERTS.

Investigations follow BS 10175, the code of practice for investigating potentially contaminated sites. Its new 2026 edition adds guidance on PFAS and microplastics.

Ground gas.

Methane and carbon dioxide from made ground, peat or old mine workings can build up in buildings. Monitoring wells let us take readings over a number of visits, including when air pressure is falling, which is the worst case. The results show whether gas protection measures, such as membranes, are needed under BS 8485.

Mine gas is a particular consideration across the Wigan coalfield. See coal mining investigation.