Coal Authority Underlines the Importance of Ground Investigation and Desk Studies

Posted on June 6, 2018
Archive : June 2018
Category : Site Investigation

After subsidence hit a housing estate in a former mining area, the Coal Authority is calling on local authority planners, surveyors, developers and consultants to ensure that the legacy of coal mining is fully considered before development takes place. In particular, they have emphasised the need for both desk-based research and ground investigations.

Following the subsidence – which impacted 35 properties – the Coal Authority carried out extensive ground investigations to identify the cause. The investigations revealed mine workings which had not been recorded on historical plans of the area.

Simon Reed, Chief Operating Officer, Coal Authority, said: “We have released our initial recommendations to ensure there is awareness of the risks posed by historical coal mining legacy, in light of our findings from this recent subsidence event.

“In this instance, given the depth and age of the workings, and knowledge about risks of subsidence at the time, we cannot criticise the developer’s approach taken at the time with respect to these mining circumstances, but we must now build on this new knowledge to address these risks better moving forward.

“This was an area of unrecorded mine workings and caution must be adopted in assuming that the absence of a record means the absence of mining. Although our historic plans did not, in this case, reveal the coal workings they are a vital part of any site assessment prior to development therefore, in future we may ask for more information, or for more works to take place, to reduce the likelihood of a similar subsidence event happening again.”

To reduce the risk of similar incidents, the Coal Authority has stressed the need for both desk-based research and ground investigations to be carried out prior to development in former mining areas. This would enable stakeholders to confirm the:

  • Potential for unrecorded shallow workings
  • Accuracy of shallow coal old working plans
  • Competence of the strata overlying the coal
  • Potential effects of groundwater including assessment of recovering levels post mining which are still taking place today

While historic mining plans are invaluable, they don’t always give a true representation of the coal workings underground. The areas mined may vary from those shown on historical plans, and the extraction rates can vary from those shown on historical plans.

This is why it is important to combine desk studies with accurate and reliable ground investigation. Geotechnics provides the full spectrum of ground investigation services – from desk-based research and specialist advice through to ground investigations, in-situ monitoring and laboratory testing. With 4 offices throughout the UK, we can mobilise to anywhere across the country to help clients save money and de-risk projects.