Compare the 2 CRMAs below and the differences and problems of CMRA soon become apparent.
With regard to both also bear in mind the statement provided by the Coal Authority at the start of Section 3 of their publication RISK BASED APPROACH TO DEVELOPMENT MANAGEMENT – GUIDANCE FOR DEVELOPERS
“The table below summarizes the potential risks associated with coal mining legacy for the proposed development site, identified from list sources of information”.
The CA statement is proceeded by a list of sources including a Coal mining risk assessment Report purchased from the CA.
There then follows a risk assessment table which the CA say can be completed by a Desk study appraisal filling in the YES/NO boxes from the list of information most important of which is the initial Coal mining report.
Geoinvestigate has in recent months raised concerns with the CA about the application of CMRA as set out in Section 3 together with the related risk assessment used for the safe drilling of coal and the choice of drill flush. We have reviewed CMRAs released to the public domain and now available on the web since 2011 when the new guidance came in. Two of the many CMRAs processed by the CA every year are presented below.
While the assessment on the left is clearly inadequate the one on the right raises questions about the philosophy of risk assessment based solely on Desk study review and whether the output is a rationale estimate or in truth really guesstimation based on several imponderables which are unknown or undeterminable without intrusive site specific investigation.
The most important imponderables in CMRA are whether shallow mine workings, hazardous mine gas and gas seepage pathways (including “fissures”) are present or absent beneath in the immediate vicinity of a site making a source-pathway-receptor model viable or not.
In the case of risk assessment for drilling consideration of the geo-hazards not only applies to the confines of the property but also to the peripheral land where there may be a risk of gas migrating into nearby occupied buildings from drilling or piling activity within the site.
A discussion of drilling and mine gas hazards is presented in the CAs publication “Guidance on Managing the Risk of Hazardous Gases when Drilling or Piling near Coal” of which Section 6 deals with the risks posed by various drill flushing mediums and different drilling Scenarios or Situations.
The report on the left is for a site which falls within a Development High Risk Area where probable shallow coal mining are present and there are several mine entries nearby. Notwithstanding, this report astonishingly comes up with a NO output for each risk/hazard though the CA have warned that “coal may be near surface” and the original text of the Coal mining report was probably less optimistic.
The report on the right is also in a High Risk Area where there are probable shallow workings but no confirmed recorded workings. Though almost everything in the initial Coal mining report is NO (No mine entries, No fissures and No mine gas) the decisions in the table are YES.
While the CMRA on the right may be considered sensibly cautious or even pessimistic by some it is in our opinion not unreasonable given that it is an armchair assessment based on circumstantial evidence. Such caution in respect of CMRA only mirrors the Coal Authorities own cautious approach to safety when dealing with the drilling of coal and mine workings.
This is to be seen in the way the CA manages their own in-house exploratory drilling jobs. Having a choice of air, misted water and foam flushing mediums they always stipulate water because irrespective of the site specific geo-hazards it is by far the safest. Essentially it does not seem to matter to the CA what part of the country the site is located, what the site specific geo-hazards or the outcome of a site risk assessment may be they always adopt the safest option of water flush because it poses the least risk.
One can perhaps understand the CAs policy of using water flush as it ensures the highest level of protection for the public on CA internally managed drilling sites whether or not the geo-hazards and their own risk assessment warrants this level of drilling safety on every site. In addition it sensibly provides a safety allowance or a margin of error for uncertainty with regard to the occurrence of the two most significant imponderables these being mine gas and fissures/pathways both beneath the site itself as well as below the adjoining properties.
Applying the same understandably cautious approach one can then equally understand why a consultancy firm or Site investigation contractor faced with submitting a Desk study based CMRA but with no hard physical information on the presence or otherwise of hazardous gas or fissures or other pathways makes a sensibly cautious choice of YES for both thereby allowing for uncertainty even though the CA Coal mining report may be interpreted differently by others.
Or put another way – “I don’t know so I’m not going to take a chance until I’m certain!”
So while on the one hand the CA themselves operate a very cautious approach to drilling in coal and mine workings vis-a-vis their stipulation for water flush only on CA managed jobs they seem to contradict themselves when it comes to issuing external drill permits to you and me which allow for air, misted water and foam flushes which normally the CA will not permit on their exploratory drill sites.
It is our opinion that similar safety concerns extend to the CAs guidance to developers when they are assessing the outcome of the completed CMRA Table and they subsequently consider the Mitigation Strategy in Section 4. The main issue the developer has to address is whether there is a need for further intrusive investigation or the matter can be quickly wrapped-up without the need for exploratory drilling.
Both of the following statements made in Section 4 of the Mitigation Strategy clearly seem to suggest that the CA is keen to avoid further investigation.
“Occasionally where the desk-based assessment cannot conclude with certainty the extent of the coal mining risks on the site; details of further proposed on-site intrusive investigation works should be set out”
“For exceptional circumstances, set out the strategy for further Site investigations”
The reasons for making these statements in the guidance is unknown and Geoinvestigate has been unable to get a satisfactory response to our recent FOI request to the CA about them.
It is our opinion that both are ill-advised statements from the CA (who after all we are told is only a “consultee”) as they introduce the expectation or target from this quasi-government body or QUANGO that 65% to well in excess of 85% of CMRAs in High risk areas should be able to confidently conclude the coal mining risk on the site without the need for further intrusive works.
In other words though in a HIGH Development Risk Area – more often than not there should be no need for exploratory drilling according to the Coal Authority.
The obvious criticism is that the CA cannot propose a system of unbiased risk assessment then try influence the outcome (as seems so clearly to be the intention of these 2 specific pieces of guidance) to fit with their expectation of the results. Reliable independent evaluation is what is required not a stick wielded by big brother.
Following the guidance from the CA the expectation would typically be a maximum of 15% to 35% uncertainty in High Risk Areas with regard to the outcome of CMRA in these areas and subsequent requirement for drilling .
Contrast this with the CAs 100% choice of water flush for their own internally managed exploratory drilling works as set out in 2015 Tender T28513 which equates with 100% uncertainty when it comes to assessing the safety of their own drilling works in High Risk Areas.
Also compare the CAs suggestion that there should be 65% to >85% confidence in High Risk Areas that drilling is not required with the following diagram.
This model is based on a diagram presented on page 38 of the CAs publication “Guidance on Managing the Risk of Hazardous Gases when Drilling or Piling near Coal”. Geoinvestigate has modified it by removing the drill rig and Boreholes – Note the paradox both in removing drilling from the model and because the CGM presented above is according to the CA the exception rather than that which is to be routinely anticipated at preliminary Desk study stage in Development High Risk areas.
Geoinvestigate believes the scenario shown by the diagram is representative of the geo-hazards which could potentially exist almost everywhere in Development High Risk areas where there are probable shallow mine workings, potential mine gases and various possible pathways to surface including natural geological fissures, cracks or breaks, mining disturbed or foundered roof strata, buried glacial or alluvial channels, basements and piles etc.
“Fissures” are included for consideration by the CA in Section 3’s risk assessment table and are described on page 9 of the guidance document.
“Fissures are large cracks sometimes appearing at surface which can be caused by mining exacerbating existing faults and breaks”
Whereas there is allowance in the guidance for uncertainty with regard to the occurrence of shallow mine working namely “recorded” or “probable” and for gas emissions (“recorded or potential”) there is surprisingly no similar tolerance regarding this pathway.
Whether this is an oversight by the CA or not this possible defect with the model has been raised with the CA under a freedom of information request. The following simple question was put to the CA
“Q6 Does the CA believe that there is less uncertainty in the predictability of fissures than there is for mine workings or gas emissions”?
Once again no satisfactory response to this question has been forthcoming from the Authority.
Faced with the CGM shown and having no site specific Intrusive site investigation data to draw upon and on which to safely base conclusions a completed risk table for this scenario would probably look like that presented earlier where the answer to every hazard is YES – Yes there is a known or potential risk of shallow coal workings, gas and pathways with the outcome being the recommendation of further Intrusive site investigation before a final decision can be made on mitigation measures.
Lower risks will be associated with an absence of these factors. Also if it is known that potential pathways, such as mine workings, are totally flooded it would have a large mitigating effect on the risk. However in reality it is very difficult to definitively prove that mine workings are totally flooded and that no pockets of dry roadways exist without detailed knowledge of the workings and a thorough understanding of the hydrogeology in the area. It should be noted that ground water levels will not, in many cases, correspond with the water levels in the mine workings
In fairness to the Coal Authority they do recognise the shortcomings of CMRA in their Guidance to Developers as the following extract shows.
“Where it is not possible to define whether there is a likelihood of any of the above conditions then it must be assumed that there is a potential for them to exist”.
The meaning of define being – “state or describe exactly the nature”
However contrary to the Coal Authorities stated expectation of this being an exceptional situation it is Geoinvestigate’s opinion that the normal expectation should be that usually it is not possible to confidently assess the site specific conditions or geo-hazards from a desk top study without an intrusive site specific investigation.
Put another way it is Geoinvestigate’s opinion that only in exceptional or rare circumstances should a CMRA be concluded without the need for proofing the site with Boreholes in a HIGH RISK AREA where there are probable shallow mine workings and the other factors gas and pathways are guesses.
So while risk based management or CMRA of our coal mining legacy may appear to have some sound rational scientific basis it is in reality nothing more than a sophisticated buzzword for what is at the end of the day an armchair exercise in guesstimation requiring that the assessor (like Superman) put on their x-ray specs to look inside the mountain.
The two examples of CMRA provided in this article highlight that CMRA can be all things to all folks and in some cases BIBO. It can be subject to misuse, manipulation and genuine error caused by a lack of experience/ignorance on the part of assessor with respect to their understanding of geology and the effects of mining and the reliability and limitations of the information on which much of CMRA is based – namely the initial Coal mining report. The latter in itself is nothing more than a Desk study so that the CMRA is in essence a Desk study of a Desk study but one which claims to provide a conclusively reliable output of measured risk rather than what in most cases it should be – a precursor to intrusive investigation.
In evaluating a site for CMRA there is an analogy with routine shallow Site investigation procedure. Even on a Greenfield site where a Desk study had shown there was negligible risk of contamination the routine expectation “to define whether there is a likelihood of this condition” would be to carry out Intrusive site investigation together with contamination testing – albeit limited. So why on earth on an site identified as being in a Coal Mining High Risk area should similar proofing be the exception rather than the norm?