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Borehole investigation of mine workings

Post 2578 of 23788

Geoinvestigate’s compact microdrill was again in action today probing for mine workings. Having previously obtained a coal drilling permit from the Coal Authority to drill with water flush Microdrill was delivered to site on the back of a standard flatbed trailer.


Access to the drilling positions in several gardens was difficult but achievable with Microdrill.

In accordance with Coal Authority Guidance on Managing the Risk of Hazardous Gases when Drilling or Piling Near Coal (essentially a Code of practice for safe drilling and piling through coal) water flush was in this instance considered to be the safest flushing medium. This is because there was assessed to be an unknown or undetermined gas risk as is so often the case in exploratory drilling works on the UK coalfields.

The Coal Authority normally stipulates small volume water injection flush for their internally managed exploratory drilling works because it ensures minimal risk to the public from hazardous gases including carbon dioxide, methane and carbon monoxide. In fact it is rare under the Coal Authorities strict safety policy for drilling through coal for them to permit anything else but water.


The Coal Authorities strict policy with regard to water flush is something to be considered by Site investigation companies when compiling a Coal mining risk assessment (CMRA) or drawing-up a source-pathway-receptor based risk assessment for drilling permit application.

It should also be borne in mind by drilling contractors and consultants that the CA polices drill sites checking some 10% of drill sites per year to ensure compliance with the permit. A change in drill flush from that originally agreed with the CA would be a breach of terms and conditions and could result in prosecution.