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To Drill, or Not to Drill, that is the question ?

Post 1736 of 23788

The UK Coal Authority finally yielded to Geoinvestigate’s demands for significant changes to be made in the wording of their Coal mining risk assessment Guidance Document “Risk Based Approach to Development Management – Guidance for Developers (Version 3, 2014)”.

The following is an extract of a letter received 17 Dec 2015 from their Corporate Manager in response to a FOI request from Geoinvestigate.


.…..You are the first person to comment on the content of the document in the four years that it has been available on our website…………

…………….concerning the use of the words “For exceptional circumstances” in the “General Guidance Notes” within the guidance document we will amend this in the next version of the guidance document to be published to read “Where necessary”.  We will also remove the word “Occasionally” from section 4 of the Model Report Template………

 We are confident from the thousands of Coal mining risk assessments which we have commented upon that nothing in our guidance document has adversely affected the content or outcome of any of them.


Geoinvestigate’s News article of 1st Dec 2015 raised the issue of  “Coal mining risk assessment and its Problems and Failings” That article flagged-up the CAs use of the words Exceptional and Occasional as perhaps having a significant consequence in respect of whether the outcome of a CMRA desk top study would lead to drilling or not.

It follows that such guidance from the CA on the expected outcome of CMRA may potentially also have had a significant effect on the safety of the CMRA outcomes which run into many thousands since the implementation of the system back in 2011.

Exceptional and Occasional are important because the inference from these descriptors is that the vast majority (some 65% to 85%) of CMRA outcomes should end with the Desk study with the expectation that only 35% – 15% of cases should progress further to Intrusive site investigation – namely “as a rule of thumb” drilling up to 30m or so.

In so using these words and stating them 2x in the guidance document it might be argued by some that the CA, wittingly or perhaps unwittingly may have influenced or biased the outcome of CMRA (which should be a wholly independent evaluation) away from drilling and site specific intrusive investigation and towards the remote desk based process with outcomes usually being decided without even inspecting the site.

The cynics among us might point the finger at the CA (a quasi non governmental organisiation or QUANGO) perhaps accusing them of pandering to the government’s drive in 2010/2011 (when the new guidance document was being formulated) to speed up the planning procedure and reduce development costs.



“Healey announces new measures to speed up planning decisions”

“Healey announces new measures to speed up planning decisions. News Release issued by the COI News Distribution Service on 25 March 2010. Planning Minister John Healey has today announced new measures designed to speed up decision-making…………”


While we will probably never know the reasons behind the CAs decision to incorporate such advice/direction to developers on the outcome of CMRA in the guidance document it is perhaps telling that while the CA have agreed to remove these terms they also feel it necessary to qualify this decision with the statement that it has not adversely affected the content or outcome of any CMRA since 2011.

In the lead up to the CAs decision to remove this controversial wording Geoinvestigate had raised the concern to the CA that a Competent Person carrying out a CMRA might feel obliged to follow the Coal Authority guidance and reach a decision in keeping with the CAs expectation namely that in most cases further Intrusive site investigation would be unnecessary. The Competent Person might also come under pressure from their developer client to obtain the same negative outcome with regard to the need for drilling.

In such a situation it is conceivable that a decision might be made whereby a less safe outcome is arrived at instead of recommending further drilling work which the assessor knows to be safer but which would result both in additional cost as well as delaying the start of the building works for the client.

With the removal of the words Exceptional and Occasional from the guidance document and the incorporation of  “Where necessary” the outcome of CMRA in Geoinvestigate’s opinion is likely to swing increasingly towards drilling, assisted by the introduction of safe, cost effective innovative technology such as that now offered by Geoinvestigaste’s New restricted access Microdrilling system.

Afterall this is common sense as the only way to conclusively prove what lies beneath your feet is to drill. Perhaps in the near future there will be less  armchair guessing AKA – CMRA and more practical site work being done.

A further nudge or perhaps “SHOVE” towards drilling may come shortly, again from the CA. They have been asked under a FOI request to revise Table 3 of their Guidance document which currently describes -

Coal Mining Geology. Record of (fissures)  with the add on “or Potential” as is currently applied to “Recorded mine gas emissions or Potential” below in the same table.

The purpose of this add-on is to allow for uncertainty in respect of the presence or otherwise of faults, fractures, fissures or break lines which may be hidden beneath a site but which can act as conduits for water and hazardous gas.

Such inevitable uncertainty is currently accommodated in Table 3 for recorded mining by “probable mining” and in the case of recorded gas by “potential gas”. However there is currently no similar flexibility or allowance for uncertainty in respect of “fissures”.                       

The reader may now realise where this path might be leading. Cutting to the chase -

In a High Development risk area where there are probable or potential shallow mine workings, unknown or undetermined potential mine gas hazards and potential fissures the source – pathway – model is complete.

This would not be Exceptionally nor Occasionally but the naturally sensibly safe assumption to arrive at for most building development or drilling work on UK coalfields where shallow coal is present. The CA themselves in their guidance document for drilling have set this out as the reasonably foreseeable coalfield CGM situation.

source-pathway-recpetor hazardous gas

Modified CA Conceptual Ground Model.

Many “Competent Persons” carrying out RAs including ourselves believe this model is appropriate given all the unknowns and imponderables at the preliminary investigation stage when there may be little or no site specific Desk study information, the Desk study information available may be on the macro scale and in most cases no visit has been made to inspect the property. Some LPAs think the same including Rugby Council


Rugby Council Decision Notice 25 Nov 2015 Planning Ref R15/2211

INFORMATIVE 1: The proposed development lies within an area that has been defined by The Coal Authority as containing potential hazards arising from former coal mining activity. These hazards can include: mine entries (shafts and adits); shallow coal workings; geological features (fissures and break lines); mine gas and previous surface mining sites. Although such hazards are seldom readily visible, they can OFTEN be present and problems can occur in the future, particularly as a result of development taking place


Logically it follows that in most cases the Desk study outcome alone would not be sufficient and further Intrusive site investigation would be required using water flush drilling (preferably a small volume injection systems such as that offered by New Microdrill) as this flushing medium is safest in High Risk or unknown coal and gas situations and where occupied buildings are nearby.



For this reason in respect of their own internally managed drill sites the CA always stipulate water flush because in self licensing themselves for first time exploratory work they invariably always assess the potential risk to be at its HIGHEST.

The CAs sensibly safe (perhaps to some conservative) approach to risk assessment matches that of Geoinvestigate, Rugby Council and many other Coal mining risk assessments Geoinvestigate has reviewed in recent months. It could be argued that if this is the general situation why bother with CMRA at all ?

It is Geoinvestigates opinion that obtaining a CMRA at the start of a planning application is often of questionable worth. In most situations we see the RA as a precursor to drilling and obtaining a drilling permit. Even then in most straightforward mining situations (excluding those involving mine entries) the CMRA is often only duplicating the same abiguity which is presented in the initial Coal mining report .

Were the planning directive to be changed with insistence from the start that a drilling investigation must be carried out  as part of the initial planning application submission (together with the stipulation that the drilling method must be a low volume water injection system) a site which was located in a HIGH Development Risk area would not require a CMRA. This would perhaps only be warranted in those instances where the property was affected by recorded mineshafts and adits.

Geoinvestigate has reviewed many CMRAs for planning applications where the outcome was predictable from the outset in that that further intrusive exploratory work would be required. Conditional planning was granted with the proviso that drilling be carried out and the results reviewed again both by a Competent Person, the Coal Authority and the Local Planning Authority. In our opinion such “double handling” is a waste of time and resources particularly at a time when LPAs and the CA are overstretched as is evident from the current long delay in the latter’s processing of drill permits.

Geoinvestigate would argue that in most cases it would be more cost effective to roll the RA and the drilling investigation together as part of the initial planning application thereby shortening the planning procedure and , reducing consultation time. Furthermore cost savings would be made by reducing potential wastage arising from the adoption of inappropriate mitigation measures that might otherwise occur were these measures to be determined soley from less accurate Desk study outcomes without the hard physical proof provided by a borehole investigation which enables specifically targeted cost effective design.

Geoinvestigate have carried out many intrusive investigations where drilling has shown coal was either absent, intact and unmined, too thin to have been mined or mineworking was too deep to influence surface development Had it not been for drilling expensive Foundation design would in many cases have been unnecessarily implemented as insurance against the unknown.

Microdrill on it's 50th job

Microdrill on it’s 50th job


More than 18 years ago Geoinvestigate predicated that the day would arrive when all development sites (no matter how small) on the UK coalfields) where there was a probable shallow mine working risk would be automatically referred for drilling investigation.

Up till recently what may have prevented this was site access difficulties, safety, drilling costs and perhaps the CAs guidance to developers and Competent Persons carrying out RA that only EXCEPTIONALLY or rarely should drilling be carried in High Risk areas which in itself is a major contradiction.

With the recent advent of innovative, safe, compact, fast, clean, quiet, cost effective, Microdrilling technology the time has now come to stop guessing about the impact of coal mining legacy in Development High Risk areas. Today the question should not be whether to drill or not but -

“Why aren’t you drilling in a HIGH RISK AREA ? “.