How does Coal Authority Development High Risk Area affect conveyancing?

The Coal Authority publishes a boundary dataset called the Development High Risk Areas (DHRA), covering ~25% of England's land area + most of South Wales + parts of Scotland. A property within a DHRA polygon is in a historical coal mining zone, and the Coal Authority recommends commissioning a CON29M Mining Report (~£15-25 retail) before exchange of contracts. The CON29M covers shallow coal workings, mine entries, recorded coal mining ground subsidence, and coal mining hazards.

For conveyancers, the practical workflow:

1. At pre-contract stage, run a point-in-polygon test against the DHRA boundary. This is a binary in-or-out check — the property is either within a DHRA or it isn't. 2. If within a DHRA, commission the CON29M. The conveyancer's standard package (Groundsure / Landmark / FCI) bundles this; or the Stratum conveyancer-suite endpoint flags it as `coalMining.band: 'high'` with the recommendation copy. 3. Communicate the result to buyer + lender. Lenders often require the CON29M for DHRA properties.

The DHRA boundary data is published on data.gov.uk under OGL v3.0 (free + commercial re-use with attribution). Stratum's postcode-intelligence API runs the point-in-polygon test at /v1/postcode/{postcode} and returns the band + matched polygon ids + the recommendation copy. Same data the paid CON29M searches use, surfaced earlier in the matter.

Not covered by the boundary data alone: non-coal mining (tin in Cornwall, lead in Derbyshire, etc) — those need separate searches via the relevant authority.

Source: Coal Authority DHRA

Last updated 2026-05-06.