Checking coal mining legacy data for a site

Two mapped areas decide how much coal mining work your application needs, and they are not the same thing. A coal mining reporting area is the broad footprint where the national coal legacy body, the Coal Authority, since renamed the Mining Remediation Authority, holds and issues coal mining information. A development high risk area is a much smaller mapped area where recorded features could affect the stability of the ground beneath your site.

Inside a reporting area you can buy a report. Inside a development high risk area you need a coal mining risk assessment with the planning application, and the Authority becomes a statutory consultee.

Check which one you are in before you commission anything else.

What a reporting area actually means

It means records exist for the area and the Authority will issue a report for a property within it. Roughly speaking it follows the coalfields: the North East, Yorkshire, the East and West Midlands, Lancashire, Cumbria, Staffordshire, Warwickshire, Shropshire, Kent, the Forest of Dean and South Wales.

Being inside one is not itself a planning constraint. Plenty of land in a reporting area has no workings beneath it, and plenty has workings deep enough to be irrelevant to a two-storey house.

What the designation does is tell you to ask the question. Solicitors act on it for conveyancing. For development, it is the trigger to run the free map check and find out whether the site is also in the higher risk category.

The map walkthrough is set out in the coalfield interactive map before you buy a site, and it is the first ten minutes of any site appraisal in these areas.

Development high risk areas and what they trigger

A development high risk area is drawn around recorded features that could affect surface stability. Typical drivers are mine entries such as shafts and adits, coal workings at shallow depth, recorded geological features that could transmit movement, mine gas outbreak sites, and areas of spoil.

Two consequences follow inside one.

First, the council will expect a coal mining risk assessment to accompany the application. Most authorities in coalfield districts list it on their local validation checklist, and an application without one is commonly returned as invalid rather than refused.

Second, the Authority is consulted on the application as a statutory consultee under the procedures in the Development Management Procedure Order 2015. Its response is technical and specific: it will say whether it agrees the assessment has identified the features correctly and whether the proposed mitigation is acceptable, and it will ask for conditions where intrusive investigation is still outstanding.

Its comments carry real weight with officers, because the authority has no in-house expertise on mining legacy and the consultee does.

What goes in a coal mining risk assessment

The assessment is a desk-based document with a specific job: identify the coal mining features that could affect this development, and say what should be done about them.

A usable one contains:

• a site description with the proposed development, foundation type and any basement or below-ground works
• a review of the coal mining information, including mine abandonment plans, borehole records and reported hazards
• the depth, seam names and recorded extent of workings beneath and adjacent to the site
• the position and, where known, the treatment history of any mine entry, with its zone of influence plotted against the proposed layout
• an assessment of mine gas potential
• a conclusion on risk to the development and the neighbouring land
• a recommendation for intrusive investigation, or a reasoned conclusion that none is needed

The last point is where these documents are weakest. An assessment that concludes no further work is needed, on a site where the seam is 15 metres down and the records are from the 1870s, will attract a consultee objection. Better to recommend a proportionate investigation and get a condition than to argue the point at appeal.

Ground conditions for foundation design overlap heavily, so commission the geotechnical assessment and the mining work together. One rig visit answering both questions is a great deal less expensive than two.

Reading the report: entries, workings and hazards

Three categories of finding drive decisions.

Mine entries are the sharpest. A shaft or adit carries a zone of influence, derived from its depth and the geology, within which building is normally unacceptable unless the entry has been located, proved and treated. Historic capping is not the same as modern treatment, and a capped shaft under a 1960s garage is a common and expensive discovery. Treatment usually means excavation to sound strata, a reinforced concrete cap and a gas vent, designed and verified.

Shallow workings are the commonest finding. Where a seam was worked within a depth that could affect surface stability, the response is drilling on a grid to prove the workings and grouting to fill voids, followed by a verification record. The cost is driven by area and depth, so a layout that keeps buildings off the worst part of the site saves more than any negotiation.

Mine gas is the least visible. Methane, carbon dioxide and oxygen-depleted air can migrate along workings and fissures, and the response is a gas monitoring regime and, where indicated, protection measures under the relevant British Standard with independent verification on site. Where the ground is also contaminated from a previous use, the gas and contamination work should be scoped together, alongside the contaminated land assessment.

The permit you need before you drill

Coal and associated mining property are vested in the Authority under the Coal Industry Act 1994. Intrusive activity that enters coal, coal mine workings or a mine entry needs a permit from the Authority, and that includes ground investigation boreholes, grouting and piling.

Build the permit into the programme rather than discovering it when the rig is booked. The application needs the site location, the proposed works, the depths and a method statement, and the Authority may attach conditions about how voids are treated and how boreholes are sealed.

The same forward planning applies to other utility and records enquiries on a site, which is the point made in ordering sewer records and pre-development enquiries.

What the data does not tell you

Four limits, each of which has caught developers out.

Records are records. Systematic deposit of abandonment plans came late in the nineteenth century, so bell pits, adits and shallow pillar and stall workings from earlier periods frequently appear nowhere. On old coalfield margins, absence of a record tells you almost nothing.

Coal only. Metalliferous mining, limestone and chalk extraction, brine pumping, gypsum and clay workings all sit outside coal mining reports and need separate enquiry, usually starting with British Geological Survey data and the local authority's own records.

No risk assessment. A mining report is an information product. It does not assess the effect of recorded features on your particular building, your foundation design or your basement, which is the job of the risk assessment and the site investigation.

No guarantee. Treatment verified 30 years ago to the standards of the day may not satisfy a structural engineer now, and the report will not tell you that.

So treat the data as the starting point for a proportionate investigation rather than as an answer. On a coalfield site the honest position at planning stage is usually that the features are identified, the risk is understood, and the confirmation comes from the ground.

Enter your postcode on PlanScope to see which reports your site is likely to need.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.