Article Geotechnical

What is a pragmatic and safe approach to assessing the feasibility and design of infiltration systems on a site? When is it appropriate to undertake BRE365 tests, and how can we do so safely?

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Image credit: James Harrison – 4D GEO LTD

Article by Georgina Donbroski (Technical Director at Leap Environmental Ltd), James Harrison (Director at 4D Geo Limited) and Alex Dent (Associate Director at WSP)

Firstly, with respect to Health and Safety matters, it should be noted that CDM Regulations place duties on both the designer (of the ground investigation, including scheduling soakaway tests) and the contractor who will be implementing the tests. Based on CDM requirements, the following considers the ERIC principle, of Eliminate, Reduce, Improve and Control.

As with any site investigation process, a phased approach makes the most sense.  A good desk study should be able to ascertain the feasibility for infiltration systems to work on site and hence the potential requirement for BRE365 testing.  Consideration must be given not only to the potential infiltration rates achievable, but also the potential for contaminated land and/or groundwater, flood risk, winter (maximum) groundwater levels, designation of the groundwater resource, potential for ground instability etc, any of which may have a significant impact on the feasibility of the use of infiltration based drainage systems.

CIRIA C753 SUDs manual outlines how the above should be considered at the conceptual design stage, and encourages a preliminary assessment using desk based sources.  Assuming no other constraints exist, C753 also gives some preliminary infiltration ratings (good/poor/very poor/other)  based on soil type and notes that where infiltration rates of 10-6m/s of higher are anticipated (clays, clayey ‘loams’, structureless chalks), then an infiltration scheme may not be viable.

Thus we can eliminate (ERIC) unnecessary  testing  at an early design stage. The elimination of unnecessary  testing is clearly desirable, not only in terms of cost savings for the client but also from a Health and Safety point of view, especially when one considers the specific health and safety issues associated with soakaway testing (deep excavation and water).

Assuming the desk study indicates an infiltration based drainage system may be feasible, then is the phase 2 investigation a good time to undertake BRE365 testing?  Possibly not.  Do you know the maximum groundwater level, the detailed scheme layout, final ground levels, proposed location of SUDs?   If not, then perhaps it is still too soon to undertake large scale testing.  C753 states that “groundwater levels should be investigated to ensure the base of the proposed infiltration component is at least 1m above the maximum anticipated groundwater level (taking in to account any seasonal variations in levels and any underlying trends)”, and a greater unsaturated zone may be required by the Environment Agency if your site is located  within a groundwater source protection zone.

It is also critical for detailed design that the BRE365 test undertaken accurately replicates the zone of infiltration proposed for the final design.  An infiltration rate obtained from 2m head of water in a 3m deep trial pit will not provide an appropriate infiltration rate for permeable paving.  Similarly, a 1m shallow soakage test will not provide a suitable infiltration rate for permeable paving design if ground levels are to be significantly reduced.  And finally, particularly for sites where the infiltration potential is borderline and interbedded soil types are predominant, then testing at your proposed infiltration component location will be critical to obtain representative parameters for design.

So what can we do at the Phase 2 stage?  Unless you can prove groundwater at depth, then groundwater monitoring is key, and where groundwater is potentially high, more and more local authorities are insisting on winter monitoring.  We are also at an ideal stage to classify our soils using relatively cheap laboratory classification testing (PIs and PSDs), which will enable us as designers to more accurately estimate potential infiltration rates.  Preliminary testing may also be undertaken in boreholes, but the results should be used with caution, noting the smaller volume of water used, the potential for smearing of the borehole sides, depth tested and the need to still test 3 times.  BRE365 tests can be undertaken at this stage, but the client should be made aware that unless the testing is at the correct depth and location, additional BRE365 test should be required at the detailed design stage.

Having established the site is suitable and the type and specification of your infiltration system, then BRE DG365 sets out the method for obtaining the design soil infiltration rate.  Testing is usually within trial pits, which should be undertaken in accordance with the AGS Guidance on the safe excavation of trial pits.  BRE365 notes the pit should be to the same depth as the proposed soakaway, and 1-3m long and 0.3-1m wide, vertical trimmed sides, square and if necessary, for stability, filled with granular material.  Noting that only pits within clay soils or rock may be stable (even this is not a given), and that clay soils should have been deemed unsuitable during the desk study phase, then arguably most pits will need to have a granular backfill to adhere to the BRE DG365 methodology.

Providing a granular backfill also acts to reduce risk (ERIC)  by: significantly reducing the likelihood of trial pit collapse to the short period it remains open; removing the presence of open water filled pits; and enabling greater ease of measurement of water levels via the slotted pipe installed for monitoring.  It also enables testing to continue safely beyond a single day, removing the potential for open pits on site.

Granular backfill may be delivered to site in large bulk bags of pea shingle, enabling the excavator to easily move these to test locations. The monitoring pipe is placed within the trial pit (end covered with a bulk bag to prevent infilling), and the base of the shingle bag split to pour the gravel directly into the pit.  Above proposed invert level, the pit may be backfilled with arisings and the topsoil and turf re-laid if further testing may be required.  If trial pits are deemed stable when water is added, for example in competent chalk, then the trial pit should be covered to minimise/improve (ERIC) the risk of working next to open water, typically with a Heras fencing panel, prior to testing.  Open pits should secure, not be left unattended for any period of time and must be backfilled immediately once testing is complete.  Testing must only be undertaken by suitably trained and qualified staff, controlled (ERIC) under the Safe Systems of Work  defined in the RAMs.

Like any geotechnical design, parameters obtained from testing must first be used accordingly.  The infiltration rate is an empirical measurement which should be calculated as defined in BRE DG365 (with due regard to the use of gravel).  If it is not possible to carry out a test to the full depth of the pit, the guidance is clear that the results may be calculated based on the time for the fall of water from 75%-25% full of the actual maximum water depth achieved, with a similar correction for internal surface area.  Results should not be extrapolated to empty.  Secondly, the results must not be viewed in isolation, and must be given due consideration with respect to all the other factors known on site.  For example, an infiltration rate c10-4m/s obtained on a site known to be underlain by silty clayey sand or ‘loam’ is indicative of some other factor influencing the local infiltration rate.  Either the ground model is wrong, or some other factor, such as a void, made ground, service trench etc are influencing the result.  Geotechnical design requires experience and training,  and the selection of design parameters is critical to providing a sustainable design, including for SUDs.

So in summary,

  • Just like any aspect of geotechnical design, a phased approach to investigation (comprising desk study, preliminary investigation and detailed investigation) should be standard practice.
  • Just like any other aspect of geotechnical investigation due consideration should be given to Health and Safety issues by all parties.
  • If a GI contractor is proposing to undertake soakaway testing without use of gravel backfill (or if this is unclear) this should be queried with them at tender stage.

When client (or their advisors) are requesting soakway testing, it should be queried as to whether suitable desk study research has been undertaken.  Where this is being driven by a third party and being requested counter to the findings of desk study, for example to prove a negative to a LLFA or local drainage board, they should be reminded of the Health and Safety risks that they are introducing by demanding a test that puts personnel (and perhaps the public) at risk for very little or no technical benefit. Perhaps in this situation, if boreholes are being formed anyway for foundation design purposes, consideration could be given to testing based on BS EN ISO 22282-2:2012 Section 6.1.4 (which is also referred to in the SuDS Manual).

All good construction practice comes from experience and learning from others, including mistakes and near misses.  The authors would be pleased to hear members experience on BRE 365 soakage testing.  Have you had any near misses?  Do you use any alternative methods for assessing infiltration?  Have you had occasion to test infiltration systems and compare with original design parameters?

References

CIRIA Report C753 ‘The SuDS Manual’, CIRIA 2015

BRE DG365 ‘Soakaway Desgin’, BRE, 2016

BS EN ISO 22282-2:2012 ‘Geotechnical Invetigation and Testing – Geohydraulic testing. Part 2: Water Permeability testing in a borehole using open systems’, BSi, 2012

Article Sustainability

Climate Change and Land Contamination Risk Management: A multi-disciplinary crisis management challenge

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Article provided by Paul Nathanail (GHD), Claire Dickinson (Geo Environmental Matters) and Dr. Tom Henman (RSK Geosciences)

Climate change is causing extreme weather events – more intense precipitation, flooding events, prolonged droughts, extremes of temperature, prolonged periods of high or low temperature, more intense storm events leading to frequent and stronger winds and steeper drops in atmospheric pressure. In their pioneering presentation at the 10th Congress of the International Association for Engineering Geology and the Environment, held in Nottingham, Judith Nathanail and Vanessa Banks (2009) highlighted the effect of climate change on land contamination, among other aspects of engineering geology. These changes will influence the way we manage land contamination and carry out site investigations, risk assessments and design, undertake and verify remediation.

As well as influencing slope stability and rates of soil erosion, these events will affect the ground and hence the risks posed by chemical contaminants in the soil, water, non-aqueous and gaseous phases. The strength, deformability, permeability and durability of ground will change. Prolonged droughts will deepen and widen desiccation cracks in high plasticity soils. More intense precipitation will saturate and weaken ever deeper soils. There will also be effects on the water table. Higher temperatures will increase rates of chemical absorption rates, weathering and biological activity.

Extreme weather events will alter the behaviour of contaminants. Increased volatilisation will result from the higher vapour pressure of volatile organic compounds (VOC) resulting from higher temperatures. Most ground gas related incidents relate to very large falls in atmospheric pressure so their occurrence may increase unless adequately mitigated

Higher temperatures and more precipitation resulting in faster weathering could capture inorganic carbon in carbonate minerals. Increased dissolution could release nutrients stimulating microbial activity such as hydrocarbon degradation.  Heavy metal mobility can increase by acidification as more carbon dioxide dissolves in rainwater.

Remediation works will be disrupted by sudden downpours. Wet, slippery conditions increase wear and tear on tyres and make working conditions more dangerous. Worker and public safety will be threatened by stronger winds picking up hoardings or loose materials and equipment.

Risk assessments, remediation design and choice of construction materials must be resilient to modelled climate scenarios, such as extreme summer and winter temperatures and increased precipitation intensity. The probabilistic UK Climate Projections (UKCP18) are based on a limited number of future greenhouse gas (GHG) emission scenarios. Land contamination professionals will need to ensure that an appropriate range of future GHG emission scenarios have been taken into account.

In the UK, a professional is usually identified by being a chartered member of their relevant body. A chartered practitioner has demonstrated a high level of knowledge, skills and experience, and is bound by a strict code of professional conduct.

A SiLC is a senior professional with the broad awareness, knowledge and understanding of land condition to provide impartial advice in the SiLC’s field of expertise. The SiLC Register lists  professionals from the range of professions relevant to land condition matters. SiLC is also the approving body for SQPs able to sign declarations of document adequacy under the National Quality Mark Scheme (NQMS). The Register is managed by the Professional and Technical Panel (PTP) of representatives from relevant professional bodies.

There is always uncertainty within site assessments and considering potential climate change impacts should be as site-specific as possible and based on available regional or local climate projections. The NQMS mandates consideration of uncertainties and the implications for both the site assessment and decisions taken on next steps.

For climate change to be effectively accommodated in land contamination risk management, each profession needs to ensure its insight into the effects of extreme weather effects are considered at each stage of a project. SiLCs are well placed to contribute to such multi-disciplinary assessments and advise on the wider implications for the project.

The authors are members of the SiLC Professional and Technical Panel.  For more information on SILC please visit www.silc.org.uk 

You can also contact Paul via email: paul.nathanail@ghd.com

REFERENCE

Nathanail, J. & Banks, V. 2009 Climate change: implications for engineering geology practice. In: Culshaw, Martin; Reeves, Helen; Jefferson, I; Spink, T.W., (eds.) Engineering geology for tomorrow’s cities. Geological Society of London Engineering Geology Special Publication, pp 65-82, 17pp. Available at: http://nora.nerc.ac.uk/id/eprint/9308/

Article

Dyslexia Awareness in the Geotechnical & Geoenvironmental Sectors

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October 4th to 10th was dyslexia awareness week and having a husband and a daughter with dyslexia, I felt prompted to write this article to raise awareness and celebrate the contribution that people with dyslexia make to our industry. This year’s theme is Invisible Dyslexia. Dyslexia itself isn’t visible and is all too often overlooked in the workplace and in education. As a result, people with dyslexia often feel unsupported, unwanted and invisible.

There are many benefits of dyslexia that are desirable to the geotechnical and geoenvironmental engineering sector including spatial visualisation, lateral thinking, deciphering data and creativity. Being able to spatially visualise complex ground conditions is an invaluable skill. Each person’s experience of dyslexia will of course be different, but each will bring skills to your business. If you work with someone with dyslexia, please don’t focus on the miss spelt words -it’s easy for someone else in your team to proof read and spell check. Instead – focus on the technical content and the fact you have a much better report as a result

For anyone wanting to understand a little more about dyslexia or for anyone who need support and advice, I recommend visiting the British Dyslexia Association website.  British Dyslexia Association (bdadyslexia.org.uk) They have a number of services and resources available for people including a helpline and can provide workplace needs assessments. They have a powerpoint designed for a workplace presentation. Link: https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fcdn.bdadyslexia.org.uk%2Fuploads%2Fdocuments%2FSupport-Us%2F2021-Dyslexia-Week-Workplace-presentation.pptx%3Fv%3D1632413597&wdOrigin=BROWSELINK

Vivien Dent

AGS Chair Elect. Leader of the Business Practice Working Group

Article

Thoughts from the Chair: Time

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Article by Sally Hudson, AGS Chair

I have always been in awe of the commitment shown by our AGS committee and Working Group members, or in fact by anyone in industry contributing to any extra-curricular activities over and above the ‘day job’. Ours is an often demanding and fast-paced way of earning a living, requiring an extra level of effort over the norm; to travel, undertake site work and meet deadlines. So this extra-over, as it were, must be recognised and gratitude is extended to practitioners and to Member companies that sanction the considerable amount of non-fee earning contributions made by staff to the AGS and other committees and industry bodies. This is how the AGS remains a not-for-profit Association and can divert resources where needed the most. We strive to provide opportunities to all those in the wider geotechnical and geoenvironmental industry for participation in all our activities. I am also grateful to all of our seminar and conference speakers for their gifts of time and expertise, which enable the AGS to fulfil this commitment to members. I will continue to drive and actively engage in these events.

The time committed to AGS activities is particularly impactful on businesses both this year and last, and our extra-curricular roles are being tested now more than ever, as we recover from the upheavals posed by the Covid-19 pandemic, by Brexit and by the unprecedented demands of HS2 investigations, enabling works and construction. I have spoken to representatives of many companies over the last few weeks and months, from consultants, main and specialist sub-contractors and from client bodies and asset owners, and the situation seems universal in that there is a shortage of quality candidates to recruit to permanent positions. This in turn has led to an increased pressure on the existing labour force. It has been well-reported that there is a national skills shortage in the UK, affecting several sectors and engineering is one of them. This matter has been predicted for some time and I am raising it here as I perceive it as a real risk to one of the core tenets of the AGS, that of a commitment to promote and enhance quality and safe practice. How do we find our way through to ensure a balance between fulfilling our commitments to clients and maintaining a high quality of work and improving on it? As the new AGS Chair, it is my responsibility to support and guide the Association activities to ensure that we provide benefit to all of our participants. I am pleased to report that we are already exploring several routes towards helping address the skills shortage crisis (and it is a crisis). We are working with academic bodies to promote awareness of this rewarding career among students in higher education and to explore potential apprenticeship routes. We are also in the process of consulting with those early in their careers and encouraging representatives into Working Groups to ensure refreshed thinking and to capture input from that group.

There is, for some, still a sense of being under-valued as a profession. Although in the long term this situation in which we find ourselves may improve our standing and recognition in the market place, we are already seeing an increase in remuneration packages required to attract candidates, a cost that will only have to be picked up by our clients. We are seeing costs of certain major infrastructure schemes escalating and although our front-end services are only a part of those costs, it is not hard to see how this could spread across all sectors. One of the powers of the AGS is that it has a voice, along with other collaborative industry organisations within Ground Forum, for Members to lobby Government on issues affecting our members and industry. Those companies that are not Member organisations of the AGS but who are active in the community and who use AGS data, please consider joining to assist in the promotion and enhancement of quality and safe practice within our industry.

Hopefully you have seen an increase in communication on what we do as an organisation to those outside of the AGS Committees during the term of my predecessor’s Chair tenure and I will continue to support this. This is my plea for your suggestions as to how we can improve or how you can assist: ags@ags.org.uk.

Article

Missing a trick? Is an unnecessarily complex permitting regime for the re-use of materials derived from historical landfill sites stifling their redevelopment?

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Article provided by Danny Hope SiLC, Hydrock; Eric Cooper SiLC, Hydrock; and Liz Hart SiLC, Lithos

Since the initiative to promote brownfield regeneration through redevelopment and the requirement for local planning authorities to maintain a brownfield register, an increasing number of derelict and contaminated sites have been remediated and safely bought back into beneficial use. Available brownfield regeneration opportunities are now beginning to shift to consider historic landfills, where permits have been surrendered, and areas that were infilled prior to waste management controls.

This interest creates a fantastic opportunity to bring these sites back into beneficial use. It provides a much-needed opportunity to improve and enhance the environment whilst at the same time delivering new homes/places and enhanced employment opportunities for the benefit of the communities in which they are located. However, we are experiencing inconsistency as to how these sites are regulated via the implementation of current waste legislation.

There is an increasing insistence that remediation supporting redevelopment of these sites, reusing site won materials, should be managed under a deposit for recovery permit (Defra, 2009. Environmental Permitting Guidance. The Waste Framework Directive) rather than following well established land regeneration guidance. This approach is causing confusion and significant delays. Ultimately if a practical way forward is not identified, there is real concern that these brownfield sites will be blighted and passed over for development in preference for less challenging greenfield sites, due to the disproportionate regulatory burden.

Anthropogenic material found in historic landfill sites is often similar in composition to ‘Made Ground’ identified on many brownfield sites and can be both chemically and physically suitable for retention and reuse within the development.  Unfortunately, the current approach is that if material is deemed to have been formally disposed of i.e., placed in a landfill (as opposed to made ground that may have been deposited across a site), it must be waste irrespective of its composition; even natural soils that have been placed in a landfill would be described as waste.  Reuse of any waste can only be achieved under an environmental permit.  Once something is classed as a waste, it must be assessed in line with WM3 and allocated a hazardous or non-hazardous waste code.

Remediation carried out under a planning permission embodies a ‘suitable for use’ approach based on generic and/or more detailed quantitative risk assessment – an approach adopted by the industry for many years. However, waste codes are allocated based on absolute concentrations, irrespective of site-specific risks. It follows that because thresholds for hazardous waste allocations are relatively low, material that is deemed suitable for use based on the site-specific risk assessment may be allocated a contradictory and barrier-inducing hazardous waste code

Once material is classified as hazardous waste there are further restrictions on how that material can be used;

  • Hazardous and non-hazardous waste codes cannot be mixed;
  • Different hazardous waste codes cannot be mixed; and
  • Treatment of hazardous waste is restricted to 10 tonnes per day.

It is also an inaccurate assumption that hazardous waste can simply be remediated to non-hazardous thresholds; this is often simply not feasible with time, cost and technical constraints.

The treatment of waste deemed hazardous under WM3 is limited to 10 tonnes per day. The current alternative is the application for and implementation of an Installation Permit. In the context of most remediation schemes, this quantity is miniscule and the upshot is that another layer of bureaucracy is introduced, with contractors having to apply for permits that they have no experience of. The industrial Emissions Directive that drives this requirement was surely never meant to regulate land remediation works?

Once in place, environmental permits are detailed on the Environment Agency public register. Permits (whether live or surrendered) will then be identified during land conveyancing, again this is a deterrent to development with property being ‘blighted’ and final sales hindered. The surrender of an environmental permit can also be a lengthy and costly process, again steering developers towards an easier option.

Within a remediation and earthworks project, limiting the options for re-using physically and chemically suitable site-won material potentially increases off-site disposal which again reduces a site’s commercial viability.

The current approach to historic landfills also undermines the government’s ‘Brownfield First’ policy and could lead to local authorities not achieving their house building targets and / or decreasing the provision of employment opportunities regionally and nationally.

Moreover, the issues raised here may also contradict the government’s ‘levelling up’ agenda. Many of the aforementioned types of site are located in the midlands and the north where land values are such that viability can be a major barrier to regeneration, more so than in the south where land values tend to be higher and development opportunities more prevalent.

Restricting the reclamation of site-won material also directly opposes the drive for sustainable development, which is a core principle in the National Planning Policy Framework and even the Environment Agency has a core principle of improving the environment while promoting economic growth. Sustainability is also important in the wider context, we are a small Island, we must ensure we use available resources wisely.

It should be noted that UK industry is at the cutting edge of global remediation innovation, developing products which are exported around the world, a significant contributor to the UK economy. If re-development of brownfield sites becomes less prevalent, this innovation is likely to be stifled and income generated by the export of new technologies overseas will reduce.

Overall, it is unfortunately the case that aspects of the current regulatory regime are creating barriers to sustainable remediation and successful redevelopment of former waste disposal sites rather than facilitating it. No environmental or social benefit is accruing from the position currently being taken and there is no value in it beyond an unimaginative commitment to compliance.

CL:AIRE, with the support of the Environment Agency, has pioneered the sustainable re-use of materials via the Definition of Waste: Development Industry Code of Practice (DoWCoP) which has seen the beneficial re-use of millions of tonnes of earth across England and Wales, when the overarching EU Waste Directive threatened to stifle brownfield regeneration. SiLC and its members have always supported appropriate use of the DoWCoP and would like to ensure its continued and consistent use in line with the guidance and its overarching aim to promote sustainability and protection of human health and the environment.

We hope that a swift resolution can be found to these issues, with a clear and consistent way forward that does not stifle development opportunities, is protective of human health and the environment, encourages industrial entrepreneurship and innovation, but does not contradict government policies and site-specific approach to risk evaluation. Discussions between CL:AIRE, the Environment Agency, government and other experts has commenced and is ongoing. The SiLC PTP will also be adding its support to these discussions.

Article

Q&A with Hugh Mallett

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Full Name: Stephen Hugh Mallett (but known as Hugh since I was 10)

Job Title:  Technical Director

Company:  Buro Happold

I am a Chartered Engineering Geologist and Registered SiLC of forty five years professional experience. The first ten years focussed upon geological and geotechnical investigations in the UK and overseas.  After a particularly rainy day on site in South Wales, I joined the civil service and spent over four years (in the dry) as a geologist in the Minerals Planning Division of the Department of Environment.  In 1990, I joined the contaminated land team of an environmental consultancy (Aspinwall & Company) and have been involved in the investigation and assessment of land affected by contamination ever since (with Buro Happold since 2006).

What or who inspired you to join the geotechnical industry?

Courtesy of a friend in my village football team, I got a summer job as an assistant QS on the M5 construction near Weston Super Mare.  On our stretch of the motorway, there was an impressive limestone cutting which was inspected / mapped by a geologist abseiling down the rock face.  What more incentive does anyone need?  And, many years later, I got to do this myself at Treffgarne Gorge, in Pembrokeshire.  It was heaven.

What does a typical day entail?

The only thing that is typical is that there is no such thing.  It is the variety of projects, the range of tasks to be undertaken and the lovely (and not so nice) people that I work with that makes me keep coming back for more.  Although the majority of my days are spent in the office, I still love site work and get out whenever I can to do some “real work”.  Perhaps the most typical aspect is that every time I think that I know the ground conditions on a site, then the uncertainty principle rears its head and something unexpected / unknown is encountered to make you realise (again) that you know nothing.

Are there any projects which you’re particularly proud to have been a part of?

Jordan Dead Sea Potash investigation.  My first overseas project in 1977 – went for 6 weeks which turned into 9 months (it was called “Wimpey Time”).  Learned to fly a hovercraft. Got rescued by a Jordanian Air Force helicopter on the Jordan / Israel border. Found live land mines (over 1000 eventually cleared from the site).  Channel Tunnel Rail Link (HS1) contaminated land assessment in the early 1990s – really developed our understanding at the time.  Writing R&D 66 and then delivering training on it to over 300 local authority contaminated land officers with some lovely colleagues and the legendary Bill Baker.  The Olympic Stadium – cycling to site, spending the morning with our site engineer Gemma as construction happened and then cycling back to the office along the Grand Union Canal – I could not stop smiling.  Devising and delivering the “Stratigraphic Beer Tour” lecture (on many occasions – invitations welcomed!).

What are the most challenging aspects of your role?

The continual need to keep up to date with the technical aspects of our work on contaminated land is double edged.  It is really hard to do but also always keeps you on your toes, so work never loses its interest.

What AGS Working Group(s) are you a Member of and what are your current focuses?

I currently chair the Loss Prevention Working Group.  It is a very active Group and has many very committed members who are always providing really useful advice and guidance through the various Loss Prevention Alerts, articles and the rather wonderful Loss Prevention Guidance, which is worth the membership fee on its own and is due to be reviewed and re-published in 2022.

What do you enjoy most about being an AGS Member?

Being part of an organisation that is concerned about raising the standards in our industry and which does something about it by the provision of useful (and used) guidance and advice.

What do you find beneficial about being an AGS Member?

I have been an active member of the AGS since the early 1990s (being a founder member of the Contaminated Land Working Group) and can honestly say that I have learned so much from that involvement – getting out far more than I put in.

Why do you feel the AGS is important to the industry?

I shudder to think where the industry would be without it.  Think of the AGS Data Format, all of the technical and commercial advice and guidance, the support provided to all of the membership, the unselfish and collaborative behaviour of so many people.

What changes would you like to see implemented in the geotechnical industry?

At my first AGS meeting people talked about the need to raise the status of ground engineers.  Sadly, despite initiatives such as SiLC and RoGEP, we are still often perceived as people grubbing around in mud who need little, if any, consideration and deserve little if any respect.

I have a dream:  To see ground engineers knighted for their professional services, receiving the salaries of lawyers and obtaining the respect currently attributed to health professionals.

Article

Taking soil samples for determination of volatile organic compounds (VOCs)

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Article provided by Judith Nathanail (LQM), Geraint Williams (ALS), Mike Smith, Paul Nathanail (GHD)

“It’s not there!” 

“You haven’t looked hard enough”.

Once the preliminary risk assessment is done, and volatile organic compounds (VOC) are contaminants of concern the sampling and analytical strategies need to reflect the ease with which VOCs can be lost from a sample resulting in a false negative analytical result.

In case you are wondering, a VOC is “any organic compound having an initial boiling point less than or equal to 250 °C (482 °F) measured at a standard atmospheric pressure of 101.3 kPa.”

Volatiles are lost rapidly if soil samples are left exposed.  Losses of 25 – 50% have been recorded within 30 seconds of exposure.  Sampling method has an even bigger effect – with losses of up to 99.9% recorded from bulk sampling.  Where in situ VOC concentrations exceed an assessment criterion, such losses can result in false negatives, leaving behind unremediated soils or prematurely ending remediation.

BS 10175 recommends that samples intended for the determination of VOCs should be taken in a way that minimizes the loss of volatiles.  The primary purpose of BS 10176 is to specify procedures that can be followed in the field to minimize loss of volatile organic compounds (VOCs) during sampling.  These procedures need to be strictly adhered to in order to provide reliable and repeatable results.

The procedures described in BS 10176 are similar to those described in long standing guidance and standards across the world.  The immersion methods require considerable time, resources, safe work practices, competent oversight and quality control.

The procedures involve taking a small sample of known weight and volume is taken using a coring device followed by either sealing the intact core or immersing the sample in a liquid to prevent losses through volatilisation in a subsequently sealed vial.   BS 10176 describes procedures based on immersion in methanol, in sodium hydrogen sulfate (sodium bisulfate) (only for low VOC concentrations) or in de-ionized water.  The core is then used directly in the laboratory without sub-sampling.

BS 10176 requires duplicate samples are taken from the same soil stratum and as close as possible to the location of the first sample to provide the laboratory with an additional sample in case re-analysis is required.

Soils up to coarse sand can be sampled.  It is unlikely that samples representative of the in-situ VOC concentration can be obtained or tested from coarser soil fractions. For coarse gravel, cobbles, etc. alternative methods such as PID headspace screening or soil vapour sampling need to be adopted.

Standards like BS 10176 are drafted by working groups appointed by BSI’s Soil Quality Committee EH/4. EH/4 is responsible for developing British Standards in the fields of soil quality, soil pollution and contaminated soil. The committee contributes to European (CEN) and International (ISO) Standards. The EH/4 committee comprises representatives of relevant industry and academic bodies, learned and professional organisations and/or individual experts. Committee members volunteer their time and expertise to the development of standards.  You can find out more at: https://standardsdevelopment.bsigroup.com/committees/50001294

The authors presented an introduction to BS 10176:2020 in a webinar in April – a link to the recording is at: https://attendee.gotowebinar.com/recording/5875920295717747975

Article Loss Prevention

Revised AGS Client Guide to Domestic Basement Construction

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Construction of basements beneath houses in central London remains a buoyant market, which is good news for the sector.  Not so great, is the sad fact that building collapses still happen during basement works.  The AGS Client Guide to Domestic Basement Construction has therefore been updated (to version 3) in order to emphasise more prominently the fundamental importance of adequate temporary works.

The temporary works play a crucial role in minimising potential damage to adjoining and adjacent properties, as well as the host building.  Forward movement of the basement’s perimeter retaining walls must be resisted with high stiffness temporary and permanent props in order to minimise ground movements alongside the basement.  The revised Guide notes that as the contractor is responsible for the design as well as the implementation of temporary works, clients must ensure that the appointed contractor has adequate in-house design expertise or that they employ a professionally qualified temporary works engineer.  In both cases the temporary works designer should be able to demonstrate successful completion of other basement projects similar to the one being planned.

The revised guide can be downloaded from: https://www.ags.org.uk/item/client-guide-to-domestic-basement-construction/

Article Report Contaminated Land

AGS Contaminated Land Working Group – Update

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Alex Lee, AGS Contaminated Land Working Group Leader, has provided an update on the top issues the Contaminated Land Working Group discussed at their last meeting which took place virtually in July 2021.

Client’s Guides

The AGS CLWG are currently in the process of revising A Client’s Guide to Desk Studies and Reference List. The CLWG are also in the final stages of producing A Client’s Guide to Geoenvironmental Reports, which is being reviewed by the group ahead of publishing.

Sustainability

At the last meeting, the CLWG discussed sustainability, which may lead to a sub-group to work collaboratively on looking at sustainable site investigations and providing advice to AGS members on this.

HSG248

The CLWG have provided feedback on HSG248 and concerns from both CLWG and the AGS Labs WG were considered at the meeting. Representatives from the CLWG and Labs WG will continue to be involved with further discussions within the wider industry regarding this document.

ERES Codes

Members of the CLWG are involved with a sub-group which is assisting with the review of ERES codes.

Working Outside Of The AGS

The AGS Contaminated Land Working Group have many members who are involved in a range of different projects and working groups; SAGTA C4SL project, the National Brownfield Forum, SiLC, SoBRA and more. This enables us to share new information within the Group but also relay the position of the AGS CLWG outside of the organisation.

If you interested in joining the AGS Contaminated Land Working Group, please contact the AGS Secretariat at ags@ags.org.uk.

Article Laboratories

Laboratory Assessment and Sampling Practice Webinar Summary

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On 30th June, the AGS held their first webinar on the subject of laboratories, focusing on laboratory assessment and sampling practice. The event was sponsored by ALS Environmental and Geotechnical Engineering.

This webinar saw Will Fardon (AGS Laboratories WG Leader), Geraint Williams (ALS) and John Powell (Geolabs) investigate various aspects of sample submission, discussing best practice and guidance for how to get the most from the laboratory, the testing and some pitfalls to avoid. The event also covered different methods for assessing vapour intrusion and issues related to the quality and quantities required of laboratory samples for geotechnical testing to ensure representative Soil Parameters

This paid for event was rated 4.6 stars out of 5, by our 100 registered delegates.

If you missed this webinar, the replay is now live and available for view on the AGS website. The webinar costs £25 for AGS Members and £30 for non-Members (prices exclude VAT). Click HERE to view the replay and download the speaker presentations and file handouts.

Article

prEN 1997 Parts 1, 2 and 3 – Latest versions

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Free download of the latest [April 2021] versions of the prENV Eurocode 7 for review and information. Any queries or comments should be addressed to the AGS representatives currently serving on the BSI B/526 Committee [Gary Evans] or [Chris Raison] or direct to BSI.

CEN-TC250-SC7_N1504_prEN_1997-1_MASTER_v2021.19_Submission

CEN-TC250-SC7_N1506_prEN_1997-2_MASTER_v2021.11_Submission

CEN-TC250-SC7_N1508_prEN_1997-3_MASTER_v2021.40_Submission

Article Geotechnical

Digital transformation in ground engineering – hopes and fears?

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Article provided by Neil Chadwick, Director, Digital Geotechnical and Stephen Lawrence West, Director, Ground Engineering, Ramboll

Digital transformation is a term that, within the ground engineering sector, can engender feelings of hope or fear or possibly both at the same time. The hope is for a future where we have tools that can help us all to do a better job for society’s benefit. The fear is of being left behind, individually or corporately, or concern about potential undesirable consequences if we allow the machines to take over. In this article we will explore some of these fears, a few of which are well founded, but our main goal is to accentuate the positives that digital transformation can bring and encourage creative thought and debate about this issue by the AGS members.

It starts with the data

The digital revolution is also a data revolution. The good news is that our industry is already pretty good at handling data. At the heart of this is our own AGS data transfer format for factual GI data. We take it for granted but it is probably the world’s most successful ground data transfer format. Other countries, and other parts of the construction industry, look at us with envy.

Despite this success we should not rest on our laurels – and we are not. The AGS format is adapting and expanding. We have introduced AGSi, for ground models and interpreted data, and a draft for AGS piling is now starting to gather some real interest. The AGS Instrumentation and Monitoring Working Group is also on the case, currently studying real world I&M data flows.

Few would doubt the value of digital tools for helping us to sort out the data, or the need for common standards for when we need share that data. The opportunity that digital transformation provides is a step change improvement on what we already have Our day to day experience of modern apps and websites has, quite rightly, increased expectations for the user experience of technical software. We want tools that are both smarter and easier to use. However, if we want our software vendors to provide these, then we need to be pro-active in telling them what we really need, and why.

Interpretation: humans vs machines?

Interpretation of data to inform design is perhaps the first flashpoint in the discussion about the nature and extent of machine input to our processes. We all know and accept that ground data is normally less than perfect, with outliers that are outliers for a good reason, albeit we don’t always know the reason at the time. In this country we have been reluctant to use even relatively straightforward statistical methods in our interpretation, so therefore it comes as no surprise to find that many get nervous when the digital evangelists start talking about data driven design and machine learning.

It is right that we should question these. Data driven design is just that. In many cases, a data driven design could give us the right answer, but data is subject to imperfections, bias and limitations. If we are not careful we may end up reinforcing the bias (as Amazon once found out, to their embarrassment), or we could get things completely wrong if we extrapolate outside the valid range of the data.  We also need to ask what is the ‘right answer’ when considering design solutions.  Can a purely data led design provide an answer that is right for the overall needs of a particular client and project that suitably weighs risk.  This is where the human element can provide insight to select the right answer having been guided by information provided from past data.

Machine learning goes further and can potentially unlock more value from our data, but the mantra here is ‘don’t forget the physics’. The realities of the ground are such that the machines will always need a human partner for their learning process, whose role will be to  define the geological and other rules that should be obeyed, and act as final arbiter to select the design ground model.

An example of the above is interpretation of geological horizons from borehole data. We already use computers to help us with this, but at present it typically needs need human intervention to account for features such as buried river channels that may be apparent from the desk study conceptual model, but may be have been missed by the existing boreholes.

Having said all that, the authors believe that we should be embracing these techniques, using them to help us make more informed and hopefully better decisions. The fact that 100 different engineers can come up with 100 different design lines from the same data is not something we should be proud of.

A good example of a positive experience from machine learning was given at the AGS Data Conference in 2017. One of the presentations looked at the machine learning applied to CPT interpretation for a large regional scale dataset. Human verification of selected interpretation was undertaken for control purposes. It was confirmed that some of the machine generated interpretations required correction after review, but these were outnumbered by the number of cases where, after review, the machine was considered to have got it right, not the original human!

Automation of the design process

This is where things start to get really interesting. There is plenty of scope for using automation to help with factual and interpretative reporting, but automation of analysis and design calculations is likely to be one of the main digital battlegrounds in the coming years.

As mentioned above, digital 3D ground models are already a reality on many projects. One area ripe for development is finding a better way to input these models directly into analysis/design software, replacing what is currently mainly a manual process. However, we need to think carefully about what model we use for input. We are most familiar with the ‘geological (observational) model’ which is our best guess of what we think might be going on based on the conceptual model and lessons learned from our education and experience. However, for analysis we should be using a ‘geotechnical design model’ which also takes account of uncertainties and code requirements.  These models can be compiled by an intelligent digital partner by prompting the geotechnical engineer to make key decisions relating to geological setting and how to account for ground related risks.

One of the main concerns expressed about automation of design is that we will forget how to do the design calculations, with the younger generation not learning at all. This is a legitimate concern, and it is by no means unique to ground engineering. If we automate (or perhaps when we automate is more correct) we will need redefine the role of the human in the design process. We will probably still be doing some sort of verification, which should allow us to practice our skills and judgement. We don’t have all the answers to this conundrum, but it would be wrong to allow this to be a barrier to much needed progress. We will have to work through it.

There are some who are ambivalent, or even hostile, to automation, fearing that many will lose their jobs. However, others see the opportunities that it can bring, such as allowing us to do more analysis, considering more scenarios, to create better designs for our clients. If we get this right, we should be able to spend more time on real design and less on manually transferring data from one bit of software to another. We need to make sure that, as an industry, we are all aligned in looking to deliver real change and real benefits. We must avoid being drawn into a race to the bottom (on time/cost). It is within our gift.

Automation in construction

Digital transformation is not confined to the design office. There are many opportunities for increased use of digital technologies on site.

Digital field capture of data for ground investigation and construction is now starting to become routine, although we still have some way to go on this.

Augmented reality, where models and the real world can be visualised together, is an under-used technology that certainly merits further attention.

Automation of construction processes is the next frontier. Will we see robots running around construction sites?  One day, perhaps, but the reality of construction automation may be slightly more down to earth. For example, it may include automated boring or piling rigs, or earthworks equipment, with humans still in attendance but with more of the work and decision making done by the machines.

Automation of earthworks operations is the one of the main subjects of research and development in the ground domain, and there are already many examples of digital technologies being used to good effect. Typical applications include tracking of compaction plant, to provide information on number of passes, to assess specification compliance. Another example, published recently in NCE, shows how a contractor is monitoring earthworks vehicle movements on a large linear infrastructure site, then using AI to optimise utilisation of the fleet.

This is not digitisation for the sake of digitisation as there are some important additional benefits that can be obtained by automating construction. Firstly, there is the obvious benefit to health and safety if we can keep as many humans as possible out of harm’s way. This is one of the main drivers for research in this domain.

The other benefits are perhaps not so obvious, but should be of interest to ground specialists. Digitisation and automation of construction will very likely lead to increased monitoring of the processes. This additional data could prove very useful, if we choose to leverage it. A further benefit should be improved consistency of processes which, when taken together with the extra monitoring, should leave us with better build quality, and better records.

We will still need humans to keep a close eye on things as the ground never ceases to conjure up surprises, but if we get this right we could end up in a much better and safer place.

Do we all need to be digital experts?

A good question, that has been answered many times by many people, with many different answers given. The reality is that we can only hold a limited amount of knowledge in our heads. It is unrealistic to ask all ground specialists to become digital specialists, and the authors believe that it would be wrong to significantly dilute or reduce most individual’s knowledge of ground engineering (whatever branch that happens to be) to make way for lots of digital skills.

However, getting digital specialists to do all of our digital legwork is not the right answer either. We should aim for a general increase in awareness and knowledge of digital issues and capabilities at all grades, including the oldies. Digital specialists may still be brought in for the heavy development work, but it would also be helpful to have some people with a foot in both camps.

Whatever the arrangement, we need ground and digital specialists to work together to identify the problems that need to be solved, and the improvements that can be made. If we leave it all to the digital people then we may get lots of shiny new toys, but not the ones we really wanted.

In conclusion

Much of this article has talked about some of the potential problems that digital transformation may bring. However, our mission has been to inform, challenge, and hopefully allay some fears. Digitisation is coming, and we should embrace it, as it will offer great opportunities for improvement within our industry and can be seen as an aid to help us communicate even more effectively with our colleagues, clients, and the public.

However, if we are going to get the most from it, we need ground specialists to work with the digital specialists. The digital specialists may know how to get there, but we need to tell them where to go.