It has long been the aim of the Contaminated Land Working Group to produce a definitive guide to ground investigation good practice similar to that produced for Geotechnical Ground Investigation in 2016. As with many things in life, I feel that this has rather been eclipsed by events. The definition of good practice has certainly changed over time and the available standards and guidance available from BSI, ISO, CEN, AGS, CIRIA, CL:AIRE and many others continues to develop around us. Indeed, there is a veritable treasure trove of training and advice available on almost any aspect of site investigation, sampling and monitoring you care to consider and keeping up with them all, and especially acting on them, can be a job in itself. This is even more true if you subscribe to or work under ISO9001 et al. With the publication of the ISO BS 18400 series on Soil Quality, hopefully some of this existing variation will be resolved, rationalised and summarised to some extent.
Having been in this business for over 25 years now, training students, young practitioners and fellow professionals in the art and science of site investigation, sampling and monitoring as well as being current chair of BSI EH/4 (responsible for BS10175), I am perhaps more aware than most of the sheer range of material out there. Indeed, I have noted on previous occasions that if stacked on top of each other, the guidance alone would probably reach to your waist. So, do we really need any more guidance on this topic? Well perhaps the main reason for doing so would be to at least provide a road map and summary of where to find all the other information you might need to know (or at least should know about) when undertaking or commissioning a ground investigation.
Firstly though, we should step back and consider what ground investigation actually is and why we undertake them in the first place. In simple terms investigation is the process used to determine and quantify remaining unknowns from the Conceptual Site Model (CSM). As such, actual ground investigation can come in many forms, types, phases and be given many (often confusing) names depending on how, where, when and what is planned. For a Desk Study or preliminary investigation for example this is usually as a site visit and observation and then remotely from the office following a review of the available data.
If, following an initial assessment of the CSM, a risk has the potential to be present, potentially significant unknowns remain and/or further quantification of perceived issues is required, we then move on to designing the intrusive or main investigation phase. This should be based on and reflect consideration of a range of factors depending on both what we know and what we don’t and should ultimately dictate where we look, sample, install and monitor real world locations and materials. This can be followed by any number of additional supplementary investigations to confirm specific aspects, the most common of which is probably undertaken to determine the extents, composition and nature of identified deleterious materials to thereby assist in the production of a site-specific materials management plans and/or remediation strategy.
So, given the above, what is Geoenvironmental Ground Investigation? This is somewhat of an open question really and as with many things depends ultimately on context and perception. For Geoenvironmental practitioners, I think the clue is in the name and should be about following a scientifically justifiable, recordable and systematic approach to digging holes in the ground and finding out what’s there. What happens afterwards is a whole topic and world of its own beyond the scope of consideration in this discussion, but should be considered and questioned when designing any investigation. What you plan to do with the data you will gather should in part, through consideration of the CSM, resources, available analysis, analytical tools available, etc. dictate what data you actually get from the investigation. Failure to appreciate this aspect from the start of the process can sometimes lead to quite significant problems and costs further down the line.
So, where do we go from here? Well a good stop-gap and the method I would generally suggest at the moment as a starting point to anyone who asks, is to look to the various standards that guidance themselves reference, especially given that all good practice should ultimately be standards driven or at least backed by standard references. BS10175 is a good summary of most of what you need to know when investigating potentially contaminated land and has extensive references to other relevant standards including in the most recent update/revision, the BS ISO 18400 series. So how would I write an AGS guidance note for good practice in Geoenvironmental ground investigation? Well I can certainly think of worse than a white page with a large arrow pointing to the latest version of BS10175 and the BS ISO 18400 series. But, as I chair of the committee that looks after all of this for BSI, I suppose I would say that wouldn’t I….
Opinion piece provided by Chris Swainston, Principal Environmental Engineer at Soils Limited
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