AGS Geology Codes – bones of contention to skeleton of the project

Although the AGS has become the industry standard way of transferring geotechnical and geo-environmental data, there remains a fairly large amount of confusion with regards to key aspects of the format.  A favourite bone of contention, particularly for the newcomer to the format perhaps, is that all too nefarious of fields, the Geology Code (GEOL_GEOL).

So what exactly is a Geology Code?  The mere name suggests that the values recorded should follow a strict naming convention, as endorsed by some faceless authority.  Who this authority might be may come as a surprise – for consultants who are not sure and want to know, it’s probably down to you.

To some the Geology Code is merely an unnecessary overhead, an extra piece of data which is superfluous to borehole log production and as such of little interest.  As the borehole log represents the deliverable, the rest is just a waste of time, right?  Of course, this is the traditional view of the subcontractor but these days an increasing number of clients have the nasty habit of asking for the data itself, not just its representation.  How the AGS format appears to have complicated life for the subcontractor!

By way of contrast, to some the Geology Code represents a versatile taxonomic tool.  The consultant takes into account a number of parameters – descriptions, laboratory results, geological maps et al – to apply due scientific method and so derive a justifiable classification for geological strata.  In this sense the Geology Code is a qualitative judgement and as such, perhaps, stands out in the AGS format from a plethora of numbers.  More wordy fields do exist, the full Geology Description (GEOL_DESC) providing an obvious example, but these are often recorded following the strict application of rules and standards.

To the consultant, therefore, the Geology Code could represent the sum of their work in the characterisation phase of investigation.  Having defined them, they can then use them to understand the nature of a site.  With them in place they can start to ask more incisive questions of the data – “how much Made Ground is there on site (and consequently how much will it cost me to deal with it)?” being a classic example.  Chemical concentrations or other parameters can be considered in their geological context, the numbers on the spreadsheet taking on meaning.  Furthermore, the assessment the Geology Code represents can be validated against laboratory test results in a manner which is simply not possible to the same degree if such assessments remain unrecorded, vast amounts of data digitally number-crunched far more efficiently than with a highlighter pen.  The view that a Geology Code is a consultant’s tool is perhaps a helpful one, the contractor’s objections above largely being vindicated.

That is not to say that consultants don’t sometimes grumble about a lack of Geology Codes, stating “the contractor didn’t put them in”.  However, such a statement may be an indicator that the consultant themselves have largely missed the point.  If the contractor’s role is to obtain the data and the consultant’s role is to interpret it why would the former perform the role of the latter?  The mere suggestion that things should be otherwise is sure to raise eyebrows in the UK market!  So the consultant’s complaint is often silenced by the gentle question, “Well, did you ask them to put it in?” or even “What should the Geology Codes be, then?”

These are key questions for the consultant to answer, the sooner the better.  For the newcomer the question of what actually represents a valid code is particularly daunting.  The consultant is entirely free to define whichever codes serve the needs of their project best, although this assumes that the consultant has sufficient confidence to collate such a list.  The AGS Notes for Guidance suggest that the BGS lexicon of named rock might provide a useful starting point, although other standards can be used.  Naturally, in house conventions may need to be observed (hence the need for the freedom mentioned above!) but the onus is clear – it is down to the consultant to define what codes are to be used.

Some consultants instruct their contractors to use their specified list in the AGS data submitted to them, on the understanding that the former is applying their judgement in their use.  This should be regarded as an achievable goal – the consultant understanding what the code represents (and their contractors position in relation to them), what they want the codes to be and communicating this to the contractor.  For projects involving multiple contractors this is of particular importance; what can be more tedious than correlating the “Boulder Clay” from one data supplier with the “BC” of another?  Either is permissible as far as the AGS rules are concerned, but allowing both into the same database may not be desirable.  Where the consultant is prepared to pro-actively manage the required codes, such discrepancies can be avoided at source.  Moreover, the contractor who stubbornly refuses to record any Geology Codes without such instruction from the consultant should no longer be regarded as an obstreperous individual, but instead an enlightened one.

Having determined that the consulting organisation needs to be in control of the active list of Geology Codes one has to be clear who within that organisation is qualified to apply them.  Given what the values represent, their application should always be the result of a clear professional judgement on behalf of an engineering geologist or geotechnical engineer.  Where such a scientific sanction is required, the consultant can ensure the quality of their data and so gain utility from it.  The Geology Code can be a great servant of the consultant where properly managed; without it (or, worse still, with bad management) the data can be almost entirely emasculated.

Of course, this is but one point of view.  Perhaps this perspective is all too idealistic.  What is your experience of working with Geology Codes?  How have you got them to work for your organisation?  Alternatively, what obstacles do you face in implementing them effectively?

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