Troed-Y-Rhiw Farm, Llan Road, Cwmfelin, Maesteg, CF34 9HW Data via plota.co.uk

From the Mining Remediation Authority, formerly the Coal Authority. The development high risk area marks recorded coal mining features at or near the surface: mine shafts and adits, shallow workings, mine gas and former opencast sites. Most planning applications there need a coal mining risk assessment; householder applications, changes of use and some minor works are exempt. Mine entry positions come from old plans and can be out by several metres, and unrecorded workings can exist anywhere in the coalfield.

Where development of farmland is needed, policy prefers poorer land over the best and most versatile (grades 1, 2 and 3a). Three sources: Natural England's post-1988 field surveys, which are definitive where they exist; the Defra predictive map for England (2025) and the Welsh Government predictive map, modelled from the soil map with 3a and 3b split; and the 1970s provisional map, which planners and other services still show, coarser and with grade 3 undivided. Where the provisional and predicted grades disagree, treat the predicted grade as the current estimate and expect an application to carry its own survey.

From the British Geological Survey and UK Health Security Agency indicative atlas. Under building regulations, as the BRE guide BR 211 (2023) sets out, new buildings and extensions need basic radon protection from class 3 in England and Wales and from class 2 in Scotland, and full protection from class 5. The class at the site itself, from the detailed BGS map, decides which.