Using the coalfield interactive map before you buy a site
The published coalfield mapping tells you in a minute whether a site sits in a development high risk area, which decides whether a coal mining risk assessment is needed at all.
Before you spend anything on a site in a coalfield, put the postcode into the published coal authority interactive map and find out whether the land sits in a development high risk area. It takes a minute and it changes what the rest of the appraisal costs. The Mining Remediation Authority, formerly the Coal Authority, holds the national record of abandoned coal mines under the Coal Industry Act 1994, and it publishes mapping that shows where recorded features are close enough to the surface to matter.
The screening result splits sites into two groups, and the practical consequences are very different.
Finding the site and reading the result
The map works from a postcode or a grid reference, then lets you zoom to a boundary. What comes back is a classification rather than a list of features: development high risk area, or development low risk area.
High risk means one or more recorded features could affect surface stability at that location. The usual causes are recorded shallow coal workings, mine entries such as shafts and adits, mine gas outbursts, recorded surface hazards, past opencast working, fissures and break lines, or a licensed coal extraction area. Low risk means none of those is recorded close enough to the surface to be expected to cause a problem.
Do not read low risk as an all clear. Records for workings abandoned before statutory reporting duties are patchy, and unrecorded shallow workings turn up in low risk areas often enough that a ground investigation still needs to ask the question. The map lowers your risk. It does not remove it.
What the classification means for a planning application
Where a site falls in a development high risk area, the local planning authority will expect a coal mining risk assessment submitted with the application. Most coalfield authorities list it on their local validation checklist, and an application without one gets held at validation rather than refused, which wastes the same amount of time.
The assessment is a desk study with a site walkover. It pulls the site specific report, abandonment plans where they exist, borehole and shaft records, historic mapping and published geology, and then says what the features mean for the proposed layout and foundations. It is a specialist ground engineering document, so it needs a suitably qualified author. National guidance on land instability in the Planning Practice Guidance sets the expectation that the applicant demonstrates the site is, or can be made, stable for the proposed use.
Low risk sites rarely need one, though a council can still ask where a specific concern exists, and a site straddling the boundary between the two classifications should be treated as high risk for scoping purposes.
The assessment is also the document that carries the mitigation commitment forward. Where it recommends grouting, capping or a standstill zone, the authority will usually attach a condition requiring the remediation scheme to be approved and implemented before development begins. Write the recommendations in terms you can live with, because a condition drafted from a loosely worded assessment is harder to discharge than the works themselves.
Ordering the site specific report
The interactive mapping is free and generalised. The site specific report is paid for, boundary specific, and it is what the assessment is actually built on. Order it against the red line you intend to apply for, not against the title plan, because an access strip that clips a recorded shaft changes the answer.
Order it before exchange. A recorded mine entry with a standstill zone around it can sterilise a corner of a site, push a building line, force a redesign of the drainage, or remove two plots from a scheme of twelve. Those are land value questions, and they belong in the offer rather than in a post-completion surprise.
Reading mine entry records honestly
Every recorded mine entry carries a position and a confidence in that position. Older records, transcribed from plans drawn before reliable survey, can be tens of metres out. Treat a plotted shaft as the centre of a search zone rather than a point on the ground.
That is why locating a shaft normally involves probe drilling on a grid, and why the cost of doing so is a normal line in a coalfield site budget. The other reason to take the zone seriously is the permit regime: any work that disturbs coal or enters a mine entry needs consent from the authority, separate from planning permission and separate from building control, and it takes time to obtain.
Cross checking against other published sources
The coalfield map answers one question. Two other free sources answer the questions next to it. Published geological mapping and archived borehole logs from the British Geological Survey show what lies between the surface and any workings, which is what governs whether shallow workings can collapse to the surface. Historic Ordnance Survey editions show pit head gear, spoil, tramways, air shafts and infilled ground that no longer appear on the modern map.
Where the three sources disagree, the disagreement is the finding. A site classified low risk that shows a pit head on an 1890s map deserves a closer look before anyone prices foundations.
Aerial photography fills a further gap. Post-war coverage often shows infilled opencast ground, spoil regrading and demolished colliery structures that never reached a published map edition, and the shape of made ground on a 1950s photograph is frequently the clearest evidence of where fill depths change across a site.
Turning the finding into a layout decision
The useful output of screening is not a risk rating. It is a set of constraints drawn on the site plan: standstill zones around mine entries, areas where shallow workings are suspected, and the parts of the site where nothing changes. Put those on the constraints plan before the design starts alongside flood, trees, rights of way and heritage.
Designing around a shaft usually costs less than treating it. Public open space, parking courts and attenuation basins can sit in a standstill zone where a dwelling cannot. That is a layout decision, and it costs nothing if it is made in week one.
Building it into an option appraisal
For a site you are still deciding whether to buy, the coalfield answer belongs in the appraisal as three numbers: the investigation cost, the likely remediation cost range, and the plot loss. All three are estimates until the intrusive work is done, so record them with the assumption stated rather than as a single figure.
An illustrative case: a nine plot site in a former mining village screens as high risk, with one recorded shaft near the southern boundary. Probe drilling and a grouting allowance are added to the ground budget, two plots move north, and the southern corner becomes the attenuation basin. The scheme still works. Had the shaft been found after the reserved matters approval, it would not have.
Published geological mapping is the companion check, and once the constraints are mapped you can enter a postcode on the home page to see which documents the application is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required, and a coal mining risk assessment is one of them. This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
What is a development high risk area?
It is a mapped area where past coal mining is likely to have left features that could affect a new building, such as shallow workings, recorded mine entries, fissures, adits or areas of past opencast working. It covers only part of the coalfield, and it is the trigger for a coal mining risk assessment with a planning application in most coalfield authorities.
Does a low risk area mean no coal mining legacy at all?
No. A development low risk area means no specific recorded feature is expected to affect surface stability, but coal may still lie beneath at depth and unrecorded shallow workings exist. Mine entry records are incomplete, particularly for workings abandoned before the nineteenth century reporting duties, so the map lowers the risk rather than removing it.
Is the interactive map enough for a planning application?
No. The published mapping is a screening tool. Where a site falls in a development high risk area, the authority will expect a coal mining risk assessment written by a suitably qualified person, drawing on the site specific report, abandonment plans, borehole records and site walkover, with recommendations for further investigation or remediation.
How accurate are recorded mine entry positions?
Recorded positions carry a stated confidence, and older records can be out by tens of metres. That is why a mine entry near a boundary is treated as a zone rather than a point, and why probe drilling to locate a shaft is a normal part of the investigation rather than a sign that something has gone wrong.
Who pays for remediation of a shaft found mid-build?
The developer, in almost every case. Discovering a shaft after foundations are priced is the single most expensive way to learn about coal legacy, and a permit is needed before any work that disturbs coal or enters a mine entry. Screening before exchange costs a fraction of the alternative.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.