Article

Industry Opinion: Dynamic Sampling Terminology

- by
Tags: Featured

This is an opinion piece by Peter Reading.

Disclaimer: The following article is an opinion piece and does not represent the views of the entire AGS.

As with many geotechnical investigative techniques, dynamic sampling has arrived via a circuitous route as an investigation tool to obtain samples primarily for contaminated land studies. The main precept leading to its development was to provide an investigation method that was relatively cheap and easy to operate whilst providing samples for inspection and testing. Ideally this would involve a method, which did not require heavy equipment and numerous tools and was easy to operate.

A number of variations have been developed in the design of sampling barrels and the method by which they may be driven, and it is perhaps not surprising that the terminology, which has been applied to the various methods, is somewhat confusing. One particular example is the term windowless now in common use where the sampling barrel used is a plain cylinder without the conventional rounded ended slots or “windows” running down the length of the barrel. However, this term is not used for all instances where dynamically driven barrels are devoid of windows, which only adds to the confusion.

This is further complicated by the term dynamic sampling being used to describe three distinctly different methods of driving the sampling barrels: the original method using a hand held jack hammer, the subsequent development of a light weight drop hammer rig on a tracked chassis and the more recent development as part of a rotary rig via a dual head system. These three methods deliver very different results, although in common use they are referred to with the same terminology, which primarily refers to the sampler and not the method of deployment. This discussion provides a suggested terminology, which removes the confusing term windowless and differentiates between the methods in common use.

It was during the early 1980s when window sampling appeared. The window sampler uses a hand held hydraulically operated jackhammer to drive tubes into the ground. This was an extension of the hydraulic breaker often see breaking concrete and surfacing such as road pavement. By the addition of a tube with a cutting edge at one end the hammer could be used to drive the tube into the ground and retrieve a sample of the soil to depths of a few metres.

The jackhammer equipped with tubes driven into the ground meant the process became quicker. However it is difficult to extract the soil from the tubes thus a slot was cut in the side of the lead tube to enable the soil to be seen and described. The tube was designed with a cutting edge at the bottom and a sloping interior at the top, which allows the soil to flow through the sampler. This sampler was difficult to use and was further developed to include long slots or windows to improve access to the sample. For the window sampler to progress the hole to depth the diameter of the sampler is progressively reduced every metre thus reducing the friction on the outer wall of the sampler and aiding recovery. Even so it is often necessary to use jacks to extract the tubes from the ground. There was also a limitation on the lithologies that could be successfully penetrated and sampled using the method.

The late 1980s into the 1990’s saw a significant change in the ground investigation industry with the demise of many of the household names of ground investigation practitioners. The result from this was many drillers became self-employed. Being self-employed the cost of a full cable tool set up was significant.

Windowless sampling came about following the development of the small track mounted rig able to drive a thick walled sample tube equipped with a liner, to moderate depths. These become commercially available around the mid to late 1990’s. These rigs seen as a more affordable method for the self-employed driller to put down holes to depths of up to 6m. (Although in some soils depths of 10m or more may be achieved) The rig, which generally weighs less than 1 tonne, can be readily moved on a trailer or transported in a long wheelbase van.

The arrival of this smaller much simpler, cleaner and cheaper rig to sample the ground was welcomed by those specifying investigations, whilst ignoring issues such as quality and representativeness of the samples recovered. The rig tooling is very different to that of the window sampler in that the tubes do not have the slot (window) in them, hence the somewhat nonsensical term windowless was used to describe them. As with the window sampler, they are reduced in diameter with depth to enable ease of extraction. In order to resolve the difficulty of removing the sample from the tube a plastic liner is used. The incorporation of the liner means that the body of the sampler becomes thicker and the area ratio becomes considerably higher, almost 115% for smaller diameter barrels. At 123mm diameter the area ratio is 50%. Such a high area ratio means the sample quality can never be considered better than a class 3 and is usually class 4 or 5 It is useful to note that the area ratio (Ar) is predominantly determined by the cross sectional area of the cutting shoe and not the sample tube itself. The sampler will only influence the Ar if it has a greater cross sectional area than the shoe. The degree of disturbance is also affected by the taper angle of the blade of the cutting shoe, which should be no more than 5 degrees for a class 1 sample system and is unrealistic for a system designed for all soil types.

During the early 2000s rotary drilling became a common method for sampling stiff clay. When deployed it would often be required to predrill using cable percussive rig to progress the borehole through superficial fine and coarse soils. Rig manufacturers, seeing the inefficiency of this two rig deployment, modified the rotary rig by providing a dual head arrangement whereby the superficial soils could be drilled using the same sample tooling as the earlier dynamic sampler rig. The borehole can therefore be progressed initially by dynamic sampling using a hydraulic percussive head and when at a suitable depth can be swopped to the rotary head to enable coring to take place. This was seen as a relatively simple addition since many rotary rigs were already equipped with both wire rope winches and a percussive hammer mechanism. The hydraulically operated hammer mechanism is able to deliver blows very rapidly. The more powerful rotary rig is able to dynamic sample to much greater depths than the smaller tracked machines, largely due to its ability to extract the sampler from greater depths. It is also able to handle a single diameter of tooling and sampler and can install and extract casing. In soft and firm soils the rig pull down can be used to push the sampler into the ground until the resistance is too great, at which point the hammer can be used.  The extra power and ability to case the hole whilst drilling at a large diameter improves the ability to obtain a slightly higher quality sample. It would seem that to continue to refer to the method as windowless sampling is not helpful and a distinction needs to be made to differentiate the methods of use.

It is useful to look at what our current codes and standards provide on this subject.

BS 5930+A1 (2020) described three methods of deploying the windowless sampler:
1. Hand held “rigs“ commonly electric, hydraulic, pneumatic and petrol driven percussive hammers – all methods are hand held.
2. Feed frame mounted drop weight rigs
3. Feed frame percussive hammer type rigs, these rigs are hydraulically powered.

BS EN ISO 22475 part 1 (2022) Table 2 line 2 refers to windowless samplers as thick walled (OS-TK/W) driven dynamically and being with sampling category C[B] where OS-TK/W refers to open tube samplers Thick walled.

There are two relevant notes that are within table 2, line2:

  • Note a) states that – if the sampling categories given in brackets are used in particularly favourable ground conditions – which should be explained in such cases – the higher quality indicated in the brackets can be achieved.
  • Note b) states includes windowless samplers

Table 2, Line 7, however, refers solely to windowless sampling and states that the achievable sample category is D (C). This clearly conflicts with the information in line 2.

BS EN ISO 22475-1(2022) provides an indication of quality class for various methods of drilling. The footnote to Table H4, Tube Sample Quality Class Assessment, states that the classification is not intended for dynamic samples from windowless samplers within a plastic liner, and advises that these will always only be classed as disturbed samples.

It is clear that with an ad-hoc history of the various sampling types, terms have become confused. It is time to adopt clearer terminology. To do this the terminology should differentiate the method used to drive the sampler and then describe the sampler type and to remove the confusing term “windowless”.

The delivery of the sampling method uses either hand held (HH) equipment with a hydraulic hammer ; the drop weight (DW) method such as the Terrier rig or  the hydraulically operated percussive hammer (HP) usually forming part of a rotary rig with a dual head. It should be noted that organisations must seriously consider the health implications for their operatives using hand held sampling due to the risk of HAVS.

There are basically two sample types the window sample (WS) a tube with a window /slot in the tube and the dynamic sample (DS)  system using a sample barrel fitted with a plastic liner, both are thick walled sampling systems with area ratios considerably in excess of 15%.

Combining the sample system and the method of driving the barrels gives the following terminology:-

Hand Held Window Sample (HHWS) – referring to a hand held hydraulic hammer which is used to drive rods that connect to the sampler tube which has slots or “windows” cut in its side. The diameter is progressively reduced every metre in order to reduce friction and aid retrieval. The sample is of very poor quality from a geotechnical perspective, being highly disturbed and altered, and is considered to be of quality class 5.

Hand Held Dynamic Sample (HHDS) – refers to a hand held hydraulic hammer used to drive the dynamic sample tube assembly with an inner plastic liner, (although less commonly used , it is understood that this combination has been adopted in some situations).

Drop Weight Dynamic Sample (DWDS) – used when referring to a small tracked or wheeled machine with a short mast where the driving mechanism is a drop weight carried on a chain lift. The weight is dropped onto an anvil that connects to drives rods fitted onto the sample tube. Due to the limited energy from the rig, the sample tubes are reduced in size as the hole is progressed deeper which reduces the friction between the sampler and the sides of the boreholes. This limits the depth achievable and the sample diameter recovered is reduced with depth (along with the sample quality). The depth of penetration is limited to less than 10m depending on the soil type being sampled. The sample quality is poor and not better than Class 4, mainly due to the very high area ratio, which reaches about 115% when using 40mm diameter tubes.

Hydraulic Percussive Dynamic Sample (HPDS) – uses the dynamic sample (DS) system to drive sample tubes by blows from a hydraulic percussive (HP) hammer which is part of a dual head system in conjunction with rotary drilling.  Because the rig is more powerful, it is able to drive the sampler with the more powerful and rapid application of blows from the hydraulic percussive hammer. It is also capable of pushing the sampler into soft to firm soil, a method considered significantly better than driving. The added power of the rig also enables the sampler to be used at a single size usually either 100mm or 123mm diameter.  The 123mm diameter sampler enables continuation of the borehole, below the HPDS section using wireline rotary drilling equipment. Casings may also be installed to ensure borehole stability whilst dynamic sampling. The area ratio for this method is typically around 47%, but it does remain constant as the same tube diameter is used for the full depth sampled. At best the method can only be considered to provide a Class 3 sample.

Method type Hand Held Window Sampling

 (HHWS)

 Drop Weight Dynamic sampling or Hand Held Dynamic Sampling

(DWDS)/(HHDS)

 Hydraulic Percussive Dynamic Sampling (HPDS)
Sample diameter 100mm to 40mm Requires sample diameter to be reduced with depth; 100mm to 40mm Requires sample diameter to be reduced with depth; Usually either  100mm or 123mm to full depth
Depth of sampling 5 to 6m Between 5 to 10m depending on strata, less using hand held 15m but could progress deeper
Casing option No Possible for 1 to2m Possible to full depth
Sample quality class 5 4 at best 3 at best
Instrumentation Only if hole remains stable and diameter is appropriate Only if hole remains stable and diameter is appropriate Yes
Approximate area ratio Up to 100% 47% at 100mm increasing to 115% at 46mm diameter 47% at 100mm diameter

Table 1 Comparison of dynamic sampling methods

The quality class of the sample obtained by any particular method is primarily determined by the profile of the sample assembly, typically thin walled sample tubes with low angle tapers providing better quality samples.  There is some evidence that the method of inserting the sampler will also affect the sample quality and it is recognised that a pushing the sampler barrel is always preferable to a dynamically driven sampler barrel.

It should be noted that currently there is no published evidence, confirming a quality difference between DWDS, and HPDS sampled materials. However, in the authors experience the faster almost continuous driving from HPDS appears result in the edge disturbance to the sample, being considerably reduced. This is visually apparent from the “turning down” of the soil fabric at the sample edges, due to the forces required to overcome friction between the liner and the sample, which is much reduced. In any event, the two techniques are appreciably different and thus a descriptor that makes this differentiation is considered justified.

Article

New AGS members in 2022

- by
Tags: Featured

The AGS is pleased to announce that in 2022, 5 member organisations and 2 specialist members were accepted by the Membership Panel and approved by the Executive. The new member organisations are TRC Companies, HS2, Chemtech Environmental, EnviroSolution and South West Geotechnical Limited. The new specialist members are Paul Perry and Vivien Dent.

AGS Membership is open to geotechnical and geoenvironmental companies who employ specialists who can provide competent services, affiliate companies who provide support services and supplies to the members and individual specialists. Full details of membership criteria can be found at http://www.ags.org.uk/about/become-a-member/

Article

Specialist in Land Condition (SiLC) Affiliate Scheme Video

- by
Tags: Featured SiLC

As part of the initiative to promote the SiLC Affiliate Scheme (https://www.silc.org.uk/affiliate-scheme/), individual SiLCs have done a grand job in sending in video clips using their mobile phones and telling why they get excited about contaminated land, why they came into the profession and why they became a SiLC (https://www.silc.org.uk/) and SQP. Watch it and see what they have to say. None of the responses were scripted. Each contributer was sent a short list of questions and whatever they say is in their own words. The contributers also provided the interesting photographs that you will see in the video. An SQP is a registered individual under the National Quality Mark Scheme (NQMS) (https://www.claire.co.uk/projects-and-initiatives/nqms).

The video (https://www.youtube.com/watch?v=xSlz87569Cg) is directed at young people, particularly undergraduates or graduates, with one of the purposes being to encourage them to look at the geoenvironmental industry as a career path. However, others who are more advanced in their careers can also join the scheme and many have done so.

All the contributers to this video show that they are confident in the profession they have chosen and talk with such contagious enthusiasm that ‘who would not want to join them’ in such a rewarding career. They talk with passion about the variety of work that they get involved in, ‘never a dull moment’ as they say, and the variety of disciplines with which they interact.

To become a SiLC first requires chartered status and then the passing of the SiLC exam. The SiLC Affiliate Scheme was developed to assists new graduates, as well as those with more experience, to work towards full membership and chartered status of a professional body with guidance from a professional body advisor, and then progress towards SiLC/SQP registration with the assistance of a SiLC mentor. A key aspect of the scheme is the mentoring which will be provided to assist those on the scheme to progress towards recognised qualifications which will be a demonstration of their experience and capability in contaminated land and brownfield regeneration.

Have a look at the video to decide whether this scheme is right for you. Details of how to join are on the SiLC website (see above for link). The flyer for the SiLC Affiliate Scheme can be viewed here.

Article

Under Pressure – Talking about Mental Health and Suicide to Create a Safer Workplace

- by
Tags: Featured

This article discusses mental health issues and suicide. If this topic causes you distress or if you are currently struggling, please reach out for help. You may like to contact The Construction Industry Helpline on 0345 605 1956.

 

Geotechnical and Geoenvironmental Specialists find themselves potentially placed within what has become one of the deadliest sectors in the UK. And the numbers are tragic. Professionals in the construction sector are 6 times more likely to suicide, than to fall from a height on site and 2 workers each day take their own lives. That’s more than 3 times the average rate in the UK and higher than any other profession. Whilst these statistics are shocking, they may be just the tip of the iceberg as they only reflect onsite work data.

Although these are heart-breaking statistics, with each tragedy leaving friends and family in despair, we must urgently consider the needs of our professional colleagues currently in crisis. Those 2 people in the industry who are thinking of, and will possibly, suicide today. Those who are struggling daily, as high functioning employees, masking their intense pain.

The Chartered Institute of Building’s (CIOB ) comprehensive 2020 report, ‘Understanding Mental Health in the Built Environment’ found that 70% of over 2,000 construction professionals surveyed in 2019, had experienced depression, 87% had experienced anxiety in the last year and over 90% experienced stress, fatigue, poor concentration and overwhelm. Worse still, 26%, just over a quarter of those professionals interviewed, had thought about taking their own lives. We must acknowledge that good mental health within the industry could be at an all time low.

What exactly is mental health?

There are many misconceptions about what mental health is and what it isn’t. Mental health is our emotional, psychological and social wellbeing, it affects how we think, feel and behave. And, just like our physical health, it can ebb and flow.  Biological influences as well as life experiences can all have a positive or negative impact on our mental health.

When we are in a good state of mental health we are better able to access our cognitive abilities, problem solve, think rationally, and see things from a range of perspectives. We are more likely to enjoy resilience and cope more effectively with the ups and downs of life. The human design allows most of us to cope with around 2 hours of stress a day without negative consequences. However, if we are left in stressful situations long enough, high levels of stress at work, then at home, perhaps with continuous worries about finances, our wellbeing can start to deteriorate. Everyday things begin to feel much harder, life begins to feel like we’re wading through treacle. We may feel angry, lost, guilty, anxious, we may begin to withdraw from friends and family and at some point, we will fit the diagnosis for a mental health disorder such as general anxiety disorder or depression, or more commonly, both. Predictions made by the World Health Organization (WHO) show that, by 2030, mental health problems (particularly depression) will be the leading cause of mortality and morbidity globally.

Do I have a mental illness if I have suicidal thoughts?

A very common misconception is that suicidal thoughts and actions are a mental illness or indicative of one. Unfortunately, this assumption is prevalent across many communities and whilst those with a mental illness, such as depression, are at higher risk of suicide, suicidal thinking can affect absolutely anyone. Suicidal thoughts are not the reserve of those with a diagnosable mental illness.

As complicated as all our lives are and as suicide is, there is an algorithm that is constant – when our pain exceeds resources for coping with our pain, and when we have lost hope that things can be different, we can see suicidal ideation. Until this is more widely understood, we will continue to see an unwillingness to seek help, such is the stigma around mental illness. This stigma will be stopping some in the construction industry from discussing their feelings of overwhelm.

So why are those in the construction industry experiencing such high rates of suicide?

If the demands at work exceed how much an individual can cope with, they will experience work-related stress. Reports from within the sector suggest there are countless and diverse demands placed upon employees of all levels, from those around the board table, to those laying boards on site.

The sector’s employees live with the nomadic nature of work, long and demanding hours, late payment issues and the boom and bust nature of the industry. It’s an industry that is straining under the impact of the climate crisis, reduced supplies, increased costs and inflation. Individual workplaces manage to stay afloat by imposing tight deadlines and low margins, which often lead to harsher working conditions. All these pressures have the potential to impact working relationships and increase harassment or bullying within a male dominated sector that often struggles with toxic masculinity. Layer on top the numerous crippling impacts of current world events, and we can begin to see why so many colleagues within this sector are becoming vulnerable to work related burnout or breakdown.

CIOB reported that 70% of workers experienced moderate to extreme levels of stress due to poor communication, 65% of senior level staff found inadequate staffing to cause moderate to extreme levels of stress and 64% of manual workers experienced stress due to bullying. If channels of communication are poor, if it’s an environment where senior level staffing is inadequate and if people are experiencing bullying or harassment are unable to communicate it, we start to see why it’s being called “The Silent Crisis” within the industry.

In such a male dominant sector, does the hyper-masculine culture still prevent men from openly talking about their mental health and the stress they are experiencing? Would it be fair to suggest that the sector still plays host to a culture of toxic masculinity, encouraging men to adopt unhealthy coping mechanisms, suppress their emotions, mask distress, create an appearance of self-sufficiency which prevents them from seeking help?

If you were concerned about the stigma surrounding mental ill health in your workplace and believed that your employer wouldn’t be able or want to help, if you felt there was no space to talk, no time to find a solution, or felt you may even risk a potential promotion or even employment if you raised a personal mental health concern, would you speak up?

Many wouldn’t and instead find a way to drown their pain in an extra beer, more porn, gambling, or illicit drugs to numb their feelings, all the while masking the truth with yet more banter and bravado. The appearance of coping is paramount, to be able to continue to support their loved ones and keep a roof over their heads. Could this contribute to the high rates of suicide within the industry?

And let’s not forget women in the industry. The 12% of females within this sector may be at risk too. We know that there are hideously high rates of male suicide, but women typically have higher rates of suicide attempts and are certainly at higher risk of self harm. The protective factors for women may be that it’s far more acceptable and therefore more probable that women will independently reach out for help from colleagues, friends, family or professionals for support.

How can we cultivate workplaces that support mental health?

It takes global and community organisational levels to change the workplace culture. There are some big cogs in the system that need to move and respond in unison to efforts on the ground and perhaps we could be asking some questions with broader strokes.

Cultural and organisational change often seems beyond our reach –  it feels like that and as long as we continue to tell ourselves that it can’t be changed, so it will be. According to The Management of Health and Safety at Work Regulations 1999, all businesses have a legal duty to protect their employees’ safety at work by undertaking a risk assessment and acting on it. The existing legislation sights physical illness or injury, so what needs to be done to ensure mental health is included? In France, legislation is clear on injuries or suicides that take place on work premises.

We also know construction is capable of change when backed by Government legislation. Back in 2005, the UK Government introduced the ‘Working at Height Regulations’, and 10 years later, we see a 40% decrease in incidents. Now that workers are more at risk of suicide than falling from height, what can the industry do to work with the Government and address this appalling figure and implement better practice for mental health and wellbeing?

The Construction Skills Certification Scheme (CSCS) provides proof that individuals working on construction sites have the appropriate training and qualifications for the job. Given how prominent poor mental health is within the industry, perhaps this could be included in the CSCS application process and help raise standards and good practice around staff mental health within the sector?

We need a collaborative, local and national approach from academies through to government to educate, coordinate and legislate.

In the meantime, what more could be done to raise awareness?  According to the CIOB report, 71% of respondents said that they had not received any mental health awareness or training within the past three years. 20% were unsure how seriously their business would respond to a member of staff if they disclosed that they had a mental health issue. But of course, if we are still assuming that our colleagues’ despair is a mental illness, we will be offering solutions that are unlikely to be appropriate.

Support to reduce suicides within the industry

We are beginning to see the introduction of Mental Health Policies, Mental Health First Aiders (MHFAs), flexible working, signposting to additional support, such as talking therapies or helplines, but there’s still have a long way to go in both educating staff and implementing processes to ensure we are working in healthy work environments that are suicide safe. Creating MHFAiders is meaningless if they are benign and if the structures are not in place to compassionately support colleagues.

The OLLIE Foundation, a suicide prevention charity in the UK, offers tailored suicide prevention training for the whole workplace, supporting everyone to feel more confident to have a conversation about suicide and mental health. The Foundation offers training to spot the invitations to recognise those at risk and to empower sensitive conversations about suicide. Most importantly we show you how as a line manager, colleague, or friend, how simply it can be to keep someone safe for now.

OLLIE advocates that in the world of suicide prevention, you don’t need an ‘ology’ to save a life. You don’t need a qualification in mental illness, and you don’t need to be a healthcare professional. You don’t need to be a doctor or a scientist or a psychiatrist. You simply need to be willing to step up and ask, are you OK? If you are willing to ask questions, listen to answers, validate feelings, and show empathy, you ARE equipped to prevent suicide. And if talking about feelings is not your happy place, or theirs, we will also show you how to use a simple process called a ‘safeplan’ and how you can use it to keep someone safe from acting on their thoughts.

OLLIE encourages workplaces to promote a culture that’s conducive to positive mental
health and wellbeing by exploring the following ideas:

  1. It’s important that the conversation around mental health isn’t automatically medicalised or formalised in the first instance. Implement a balance of both formal and informal support pathways. Peer support is most effective through activities the workforce is interested in and have suggested themselves, mens’ walking groups, 5 aside football matches, pizza nights for example. These all provide opportunities outside of work that help to create a culture of connectivity that can lead to courageous conversations. Steve Kerslake, founder of Construction Sport, recently featured in BBC’s We Are England: Mental Health, Coping in Construction to share the success he has had in using sport as a tool for peer support and conversation starters.
  2. More formalised support and clear signposting to external agencies such as Lighthouse Club’s Construction Industry helpline (flyers on the back of toilet doors, stickers on hardhats) to ensure as many colleagues as possible are made aware of the support available to them. The range of support available should be regularly shared and discussed, not just targeted to an individual at a time in need.
  3. Increase the team’s confidence through training and awareness talks such as those provided by The OLLIE Foundation. The University of Kent recently identified the industry’s biggest obstacles to discussing mental health was ultimately fear- that the word ‘suicide’ may have a negative impact on individuals and that it would be associated with the organisation raising this issue. We understand why that would be, but such fears are based on false assumptions, like the one shared earlier that all suicidal behaviours are indicative of mental illness. Another common fear based on false assumptions is that asking if someone’s thinking of suicide may just put the idea into their heads. You aren’t alone in worrying about that, but the truth is quite the opposite, research suggests you may just help save their life.
  4. Make a commitment to best practice and standards though a co produced Mental Health policies. It’s vital that your policy is unique to the needs of your workforce so that it is relevant and helpful and actively referred to for guidance from all members of the team – you may like to refer to The Mental Health at Work Commitment or Building Mental Health Charter to help get you started or review your current policy and practice.
  5. Ideally the workplace understands that its greatest asset is its staff. When that is the foundation of the workplace, things tend to flow better for everyone, including the bottom line! But as we don’t all have that foundation in place, let’s look at how we can create more open cultures of conversation so we can normalise discussions about wellbeing and mental health, with authenticity. Senior management can have a pivotal role in engaging in this type of conversation with colleagues at work, starting by openly talking about their own life experiences and feelings to set a precedent.

 

If you wish to continue this conversation around the great practice in your workplace, how we maintain good mental health and what more we can do to reduce emotional overwhelm and suicide within the construction industry, please participate in this anonymous questionnaire using the QR code below. Doing so will support OLLIE’s understanding of the obstacles to support and your stories of success.

If you wish to reduce the stigma and keep you, your colleagues and your loved ones safe from suicide, please do get in touch with The OLLIE Foundation to find out how they can support your workplace. Or simply join one of our online training sessions, they are open to everyone.

Getting tooled up with mental health support and suicide prevention with OLLIE gives organisations a unique advantage, boosting staff morale and their reputation within their community through their CSR. Align with OLLIE, and we’ll pledge to pay it forward, using training fees to fully fund prevention and awareness training for organisations, schools and public facing services in the workplace’s local community.

For further information please email: contactus@theolliefoundation.org

Article produced by Vicky Gutteridge and Debi Roberts – The OLLIE Foundation

Article

Q&A with Katharine Barker

- by
Tags: Featured

Full Name: Katharine Barker

Job Title: Associate Geotechnical Engineer

Company: CampbellReith

Katharine has 15 years’ experience as a geotechnical engineer. At the start of her career she was a site engineer working predominantly in London logging cores for projects such as Crossrail and the Emirates Cable Car. In 2013 Kat spent a year in New Zealand helping the rebuild effort in Christchurch after it was devastated by a series of strong earthquakes in 2010/2011.

On returning to the UK, Kat moved into consultancy and has been involved in projects ranging from foundation and retaining wall design to investigating the extent of un-mapped tunnels in the Chalk on the Isle of Thanet. She is involved in projects that range from small commercial extensions to large 500-unit residential schemes, industrial warehouse refurbishments, slope stability analyses and technical due diligence assessments.

What or who inspired you to join the geotechnical industry?

As a child I always wanted to be a geologist, which probably had something to do with growing up in New Zealand. After graduating from Bristol University with an MSci in Geology I initially wanted to venture into geophysics, but with jobs being few and far between the next best option was to take a role as a geotechnical engineer.

What does a typical day entail?

The day itself can vary broadly, but it always starts with checking those inescapable e-mails. During the course of the day I check in with the graduate and project engineers in my team to make sure that they are happy and busy. The rest of the day is filled with variety; writing fee proposals, compiling geotechnical designs, writing or reviewing reports, providing advice to my structural and civil colleagues, directing on-site investigation works, invoicing, resourcing and mentoring junior staff.

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

The first project I was handed when I joined CampbellReith was a new appointment to a Southend-on-Sea Council framework to provide geotechnical consultancy services, with a particular focus on the condition and stability of a number of areas of soft cliff frontage along the coast. Being part of this project from the very beginning has been very fulfilling.

From the initial visual inspections and risk assessment of the cliffs, to designing a ground investigation scheme, this project has offered diverse and enjoyable challenges throughout. We are currently in the process of undertaking ground investigation works, which will be used to build a comprehensive ground model for the slopes, allow stability analysis and, ultimately, the design of a stabilisation scheme that will safeguard the slopes from significant future ground movements.

What are the most challenging aspects of your role?

The most challenging part of many of the projects I’m involved in is communicating the importance of geotechnical input at an early stage. With most geotechnical hazards being below ground the old adage ‘out of sight, out of mind’ is something we have to constantly battle against. It’s often only when something goes wrong that geotechnical engineering is given the consideration it deserves.

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

I am a member of the Instrumentation and Monitoring Working Group as well as the Geotechnical Working Group. I was one of the founding members of an Underpinning Focus Group, which was established to further explore the subject of ground movement in relation to underpinning.  Our main objective is to look at the data available to try and better understand the ground movements that can arise from underpinned basement construction, with a view to establishing a clearer method of predicting potential ground movements associated with future projects.

What do you enjoy most about being an AGS Member?

I enjoy collaborating with my peers as part of the Working Groups.

What do you find beneficial about being an AGS Member?

Being able to actively participate in the community and contribute to the guidance and outputs produced by the AGS.

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

It’s important for the industry to have these groups where like-minded people can meet up, share knowledge and collaborate in productive ways. The AGS covers a broad range of aspects within the geotechnical and geoenvironmental disciplines, and I think the interaction and collaboration between disciplines helps the industry evolve in a positive way.

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

I’d like there to be an increased awareness and understanding of the importance of geotechnical engineering in the construction industry, which is a mammoth task that most of us are constantly fighting to achieve.

I also think that graduate or junior engineers would benefit from spending time on site as a ground investigation contractor to learn where the data they use in their models comes from, how it is gathered and what shortcomings or limitations there are during the data gathering process.

Article Contaminated Land Sustainability

Responding to the UK’s Soil Crisis – Sustainable Soil Management & the Future of Soil Reuse

- by
Tags: Featured

“The nation that destroys its soil destroys itself” President Franklin D Roosevelt, February 1937.

Summary

Humans have relied on soil for millennia but, globally, soil health is threatened, particularly by  climate change and intensive agriculture. The past decade has seen increased policy focus on soil, as the impacts of soil degradation on carbon stocks and the wider ecosystem have come under scrutiny. Government policies across the world are now starting to reflect the need for soil protection. However, effectively implementing such policies within the construction sector will require a significant cultural shift. Best-practice soil management and reuse, and the use of reconstructed soil, can contribute to a solution that improves soil health and quality and plays a role in mitigating climate change. Global targets for soil health, quality and its carbon stores must also be part of any serious efforts to reverse its decline.

Context & Issue

Soil consists of minerals, organic matter (specifically the material left over from decomposing plants and animals), organisms, water and gases. It underpins the food system, contains nutrients needed for plants to grow, and stores water. It supports biodiverse habitats; one gram of soil contains tens of thousands of microbial species. Soil acts as a filter for water, so it enters rivers more purified, and plays a key role in flood management, holding water after heavy rainfall. It provides a platform to allow construction. It also offers the most significant carbon storage system on earth, helping to regulate the climate.

Despite its life-giving properties, soil is in crisis across the world. Along with the effects of intensive agriculture, a growing population has caused significant changes to land use and contamination of soil. It is claimed that 3 cm of topsoil is generated every 1,000 years (UN FAO, 2019), yet in England and Wales roughly 2.9 million tonnes of topsoil are eroded annually. Most soil in England is classed as either ‘degraded’ or ‘very degraded’ (Environment Agency, 2019). Once soil becomes degraded, it can potentially emit greenhouses gases: carbon dioxide, methane and nitrous oxide.

On construction projects, the enthusiasm for projects to begin can be at the expense of highest quality, planned soil management. The tendency to strip sites and stockpile soil remains common; reuse is frequently an afterthought. Planning early to understand soil resources on construction sites (a Soil Resource Plan with Survey) and prepare for their reuse is too often overlooked. This creates the conditions for damaging soil and the risk of it being a waste material. Many consultants and advisors are pushing hard to change this behaviour and to create more educated clients.

Soil on construction sites are at risk of compaction as well as poor stockpiling conditions. Heavy machinery use increases soil compaction, compressing the soil structure and reducing porosity, nutrient cycling and gas exchanges, limiting productivity.

The risk of damage is increased for heavy clay soil during wet periods. More frequent, erratic weather patterns could increase this risk if it becomes more challenging to follow handling and management procedures on-site.

Another challenge is to encourage people’s engagement and understanding of soil, at individual, professional, societal and political levels. There is a clear need for political leadership and commitment to managing and improving soil health and quality. This will ensure its role in mitigating climate change is protected with waste creation and disposal minimised.

Addressing the issue

The UK is at a crossroads in deciding how it approaches soil management. Currently, soil accounts for the greatest tonnage of waste disposed to landfill in the UK. The complexity and relatively low environmental priority of soil creates significant challenges to its future management but, already, there is a lot of knowledge and expertise available to address the issue. The UK Government’s Soil Health Action Plan for England intends to address the challenge of increasing soil degradation by supporting the 25-year Environment Plan’s ambition for sustainable soil management by 2030. The scale of this crisis is finally appearing high on international political agendas too.

Industry can be empowered to take ownership of the issue and develop solutions for better soil management. The CL:AIRE Definition of Waste: Development Industry Code of Practice (DoW CoP) was the first, and remains a flagship initiative for the construction industry. It works within the principles set out in the Department of Business Innovation and Skills ‘Regulators’ Code’ (Office for Product Safety and Standards, Regulators’ Code) and remains a joint industry – regulator approach to soil management. A key objective of its design was to support the regulators by creating a system which clearly identifies low risk projects and activities, thus allowing them to focus resources on the opposite. Since its launch in 2008, the DoW CoP has allowed the sustainable reuse of over 160,000,000 m3 of soil and excavated materials, either on the site from which they were excavated, or on an alternative receiver site.

Landfill and soil waste

More needs to be done in the UK to discourage soil ending up in landfill. Defra’s 2022 statistics on waste (Defra, 2022) show that 58% of landfill tonnage is soil, most of which was removed for civil engineering projects and housebuilding. The situation is deeply ironic: removing and separating the soil from its natural environment means that it is effectively ‘lost’, yet this also leaves the problem of having to dispose of the removed soil, coupled with a need for importing virgin materials to make up the shortfall. The extraction and use of these replacement materials come with their own list of negative environmental, social and economic issues. The UK urgently needs a policy and regulatory system to stop this huge amount of soil going to landfill, whilst ensuring soil can be reused to a demonstrably high standard of environmental protection. In laudably chasing waste minimisation, care is needed to avoid creating the conditions for a race-to-the-bottom with regards to operational standards.

There are potential risks associated with soil when it is displaced, whether by industrial extraction processes and landfilling, or through erosion and climate pressures. The current Waste Strategy for England (Defra and Environment Agency, 2018) ignores the loss of soil to landfills despite these two issues being connected. This needs to be addressed. Such quantities of soil ending up in landfill sites is an indication of the low interest value accorded to the soil by UK citizens, society, politicians and policy makers. The two greatest inhibitors to soil reuse (and diversion from landfill) as they make it simply impossible are

  1. a lack of local potential receiver sites (e.g. a site with a requirement for soil), and
  2. non-alignment of donor (e.g. a site with surplus soil) and receiver sites during construction phases.

Where soil has been stockpiled, in the hope of eventual reuse, they readily become a burden to the holder. This increases the likelihood of them becoming a waste, (e.g. the likelihood of discard is increased) and certainly degrades their value ( by virtue of being a waste rather than a resource) to the point where they become benchmarked against some of the lowest grade waste streams we manage as a society. For example, Letsrecycle.com shows the market prices for many recycled materials. Negative values are only really associated with, unsurprisingly, the lowest quality materials such as Mixed Recycling facility films (plastic bags and wrappings), glass and low grade wood. That soil is frequently valued as poorly as such low grade wastes demonstrates how far the construction sector needs to change its behaviour if it is to truly value soil as a natural resource.

Creating the conditions for industry to set up high-quality, fixed soil treatment facilities, which can hold these valuable materials until the receiver site (that which is accepting soil) is identified and ready, would certainly play a huge role in addressing this negative situation. Poor performing treatment facility operators must not be allowed to unlevel the playing field against operators charging for a quality service to manage a valuable resource. The concept of ‘geo-resource’ hubs has also been developed by colleagues at the University of Plymouth, which captures the concept well.

Conversely there has been a tendency to overlook the benefits of bringing displaced soil back into its own environment. These benefits are detailed below.

Carbon storage

When soil is damaged, it cannot perform the essential task of storing carbon. Greenhouse gases are emitted in greater amounts. Lateral diffusion transfers nutrients to water and leads to degradation of aquatic ecosystems, placing an even greater strain on the environment.

Best-practice soil management helps address these issues and improves soil functionality at completed sites, beginning the process of re-capturing carbon back into the soil.

Water regulation

Uncompacted soil allow water to infiltrate, reducing surface runoff and the leaching of nutrients into water bodies during wet weather. Soil also retains water for plants to access during drier periods and this retention ability is essential for the creation of a healthy sub-soil ecosystem. Soil that has been sealed cannot hold rainwater. Replacing open areas and covering soil with a hard surface such as concrete (soil sealing) can have a significant negative impact on the above processes. Over a large area it becomes especially problematic. This flags how imperative it is to consider this issue at the early site project design stages as part of a soil resource plan.

Biodiversity net gain

A healthy local habitat is dependent on the quality of the soil underpinning it. Our understanding of the importance of sub-surface interactions has increased dramatically. We appreciate more than ever the vital role that mycorrhizal fungi and bacteria play in creating optimum growing conditions. Where soil is damaged, either physically or biologically, it follows that this will be reflected negatively on the surface. This ultimately hinders any effort to improve biodiversity of construction sites.

Reconstructing soil

Lost soil can be reconstructed. This could reduce the pressure on valuable and finite topsoil and support both sustainable development and food security. Inert materials (a frequent waste stream of construction operations) can be carefully mixed together to create a substrate with the characteristics of a healthy soil. This can be used in the manufacture of topsoil for urban grasslands, and potentially in the future for materials in high-value markets, such as horticulture and agriculture.

Cornwall’s Eden Project is an impressive example of infrastructure built using reconstructed soil in 8 hectares of a former sand quarry. Here, more than 80,000 tonnes of reconstructed soil were made by mixing locally-sourced, readily available waste materials. The resultant soil has a much higher organic component than most natural soil and has provided an excellent laboratory to assess the potential of reconstructed soil and how it might be optimised for widespread use. The team at the University of Plymouth has produced soil from suitable waste materials, working to improve their efficiency and nutrient retention, and influence both their deployment and the regulations surrounding their use. This work hopes to demonstrate the potential of reconstructed soil from waste as a viable option for communities across the world who need to rebuild their soil resources. This work continues under the ReCon Soil project, more details of which can be found at https://www.claire.co.uk/projects-and-initiatives/dow-cop

The components of natural soil can be varied but it is possible to develop reconstructed soil that potentially function better than natural soil. There is an obvious link here to material reuse, the circular economy and carbon capture.

Another benefit of soil creation is that it can be made to a specification. Depending on the application, the health of reconstructed soil needs to be assessed for its suitability, based on its end use location. A safe and high-performing reconstructed soil, deployed for construction, would be a precious resource in efforts to achieve environmental sustainability. Continued monitoring to ensure the soil’s performance will be key. For example, if it was situated close to a water course, and leached a lot of nitrogen, this could have a negative impact on water quality. If monitoring shows that the microbial community in the soil is not fit for purpose, this can be amended. Once the soil becomes `living’ it will need to be assessed at regular intervals to ascertain how well nutrients and other quality indicators are being retained. It will also be important to understand how such soil function in the long term, and to what extent their chemistry and biology should be regulated.

Land management

The nutrient content of soil differs depending on land use and management. Sustainable soil management seeks to optimise different functions to increase soil resilience, depending on the main land use. To develop effective solutions there is still much research left to do. Scientists need to embark on extensive monitoring and data collection. This would be helped by employing a whole-system approach involving natural and social scientists, communities, industry and policy makers. Alongside this there is great potential for the construction sector to adopt digital solutions to support soil management. One of the immediate areas where this could be done is with soil tracking. Once soil resources are properly assessed and their reuse is planned, the soil is handled and placed; it is imperative that its location, health and function is tracked throughout the process.

Conclusion

Regulation and policy must keep pace with scientific progress if climate emergency declarations are to become more than rhetoric. Wherever possible and appropriate soil must be considered, by regulators and industry alike, as a resource within a circular economy. Alongside this, ‘soil managers’ (e.g. the construction sector) must act as primary custodians of this resource. Where firms have sustainability strategies, including elements such as targeting zero waste and environmental net gain (often publicly marketed), it is imperative that best-practice soil management is always adopted. To not do so can call into question such strategies and commitments.

Soil management is not the sole task for either government or industry, it is a joint endeavour. CL:AIRE remains committed to helping create the conditions to allow this to happen especially through its DoW CoP.

The time in which environmental stewardship strategies can be developed is limited; it has to happen now.

References

Defra. (2022). UK statistics on waste. Retrieved from https://www.gov.uk/government/statistics/uk-waste-data/uk-statistics-on-waste

Defra and Environment Agency. (2018). Resources and waste strategy for England. Retrieved from https://www.gov.uk/government/publications/resources-and-waste-strategy-for-england#full-publication-update-history

Environment Agency. (2019). Retrieved from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/805926/State_of_the_environment_soil_report.pdf

FAO, U. (2019). Soil erosion: the greatest challenge to sustainable soil management. 100 pp. . Rome: Licence: CC BY-NC-SA 3.0 IGO.

Office for Product Safety and Standards. (Regulators’ Code). Regulators’ Code. Retrieved from https://www.gov.uk/government/publications/regulators-code

UN FAO. (2019). Retrieved from https://www.fao.org/about/meetings/soil-erosion-symposium/key-messages/en/

Article prepared by Professor Mark Fitzsimons, University of Plymouth & Nicholas Willenbrock, CL:AIRE

Featured image credited to Cognition Land & Water

Article

Definition of Waste Code of Practice and the regeneration of historic landfill sites – Where are We?

- by
Tags: Featured

The Specialist in Land Condition (SiLC) Register has been debating the regulatory approach and options for regeneration of landfill sites and use of the CL:AIRE Definition of Waste Code of Practice in England and Wales (DoWCoP) and the significant issues that are arising.  This article follows one which appeared in AGS Magazine during 2021[1].

On 21st June 2021, SiLC wrote to the Environment Agency (EA) and Department for Environment, Food and Rural Affairs (DEFRA) to raise the profile of the problem citing that “due to the demand on UK land resources, brownfield regeneration professionals are beginning to consider redevelopment of historic landfills, whether or not permits have been surrendered, and areas infilled prior to waste management controls. This interest creates a fantastic opportunity to bring these sites back into beneficial use, however, we are noticing an increasing degree of inconsistency in how these sites are regulated via the implementation of current waste legislation.”

Responses were received from both DEFRA and the EA, which essentially welcomed our suggestions but requested feedback and evidence to support SiLC’s views to ensure that any change in approach is protective of human health and the environment – obviously, a shared goal of SiLC.

As part of our drive to gather this evidence and support change, on June 30th 2022, SiLC hosted its first ever live webinar entitled Regeneration of Historical Landfill Sites – Multi-Stakeholder Perspectives. We had an amazing response with 168 registering, 137 final attendees, with a further  31 viewing the recording. Feedback was great, with an average survey rating of 4.5 out of 5. This topic is clearly very relevant for brownfield professionals.

Key themes covered in the webinar included looking at the history and development of the DoWCoP and key decisions that under pinned this; presentation of case studies which illustrated DoWCoP could effectively be used for regeneration of historic landfills while securing environmental betterment and protection of health; and case studies that clearly showed significant issues with undertaking land regeneration under the permitting regime, namely that there are no suitable permits and the adoption of waste codes in permits hinder the suitable for use approach.

Alongside this webinar, SiLC undertook a survey during August and September 2022 requesting views on the use (and misuse) of the DoWCoP and in particular experiences of the difference between project and programme delivery via DoWCoP and permitting. We had an excellent response with 212 respondents, again demonstrating this is an important topic for brownfield professionals.  Responses were mainly from consultants, registered qualified persons and specialist remediation contractors (combined 89% of total), 6% of respondents were regulators.

Key themes from the survey were a clear drive on the part of regulators to permit more activities, leading to significant increased costs and delays in projects as reported by 48% of respondents.  The permitting system is overwhelmed, with the average determination time of 2 years recorded in the survey.  Whilst we were not surprised, it was stark reading to find that 17% of projects were abandoned because of this issue.  However, the survey did also indicate that there is still misunderstanding regarding the DoWCoP intended use and some delayed projects were highly likely to have been due to the code of practice being applied incorrectly.

SiLC are committed to raising standards, raising quality, and raising awareness. We intend to follow up this article with a more detailed breakdown of the survey results, share with CL:AIRE, continue evidence-based discussions with the EA and DEFRA and also consider how we can support industry to better understand available options for management of soils.  A framework for action will be included in our follow up AGS article.

[1] Missing a trick? Is an unnecessarily complex permitting regime for the re-use of materials derived from historical landfill sites stifling their redevelopment? AGS Magazine August / September 2021.

Prepared on behalf of SiLC by Danny Hope (Hydrock), Louise Beale (SLR Consulting), Clive Williams (Mott Macdonald) and Liz Hart (Hart Environmental Ltd).

Article Safety

The relationship between LOLER and drilling machines

- by
Tags: Featured

The Health and Safety Executive (HSE) requires industry bodies, such as the Association of Geotechnical and Geoenvironmental Specialists (AGS) and British Drilling Association (BDA) (who represent the majority of the land drilling sector), to provide guidance to their own sectors through documented standards of good practice and guidance to help ensure legal compliance and encourage safety improvements.

The relationship between drilling machines and the Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) has been regularly contested as the primary use of a drilling machine is not to lift, thus precluding a drilling machine from the scope of LOLER. However, the components forming, and added to the mechanism in order to create a borehole, are the same as those used by machines for lifting. It is therefore prudent that the drilling industry implements robust examination and certification requirements to ensure the safe operation of the drilling machine.

Current AGS and BDA guidance documents, combined with the BDA audit, require that the maintenance and inspection requirements of drilling machines should be undertaken to the same standard, with regards to competence, thoroughness, and recording, as that required for components legislated for by LOLER.

Following consultation with the Health and Safety Executive (HSE), and subsequently underpinned by the release of L113 Safe use of lifting Equipment, (HSE 2014), the land drilling sector represented by the AGS and BDA:

  • mirrored the requirements of LOLER, where it could be applied,
  • reinforced the Provision and Use of Work Equipment Regulations 1998 (PUWER) in its

Why has the drilling industry chosen to mirror elements of LOLER?

The mechanism for progressing a borehole is either, rotational, resonance or percussion, or a combination. It is reasonable to conclude that a drilling machine is not designed “for” lifting or lowering loads but for creating boreholes; confirming that a drilling machine cannot be tested against LOLER as it fails at the first hurdle.

To explain why aspects of LOLER 1998 are adopted; an understanding of the failure modes that are aligned between machines designed for lifting and machines designed for drilling must be considered. Both types primarily use either or a combination of steel wire ropes, sheaves, and winches. Additional components are used on both types, to connect auxiliary items to enable the activity to take place. Therefore, both types of machines will have similar failure characteristics caused by overloading, under rating, damage and deterioration due to use or working environment. Where failure modes are aligned it is obvious that mitigation of failure should also be aligned.

Which elements of LOLER 1998 are applied to drilling machines?

LOLER prescribes (regulation 9, 10 & 11), and the AGS and BDA supports, a regime of inspection with two significant, prerequisites which are:

  1. A specific regime for inspection; annual thorough examination of the drilling machines and six- monthly thorough examination of accessories, and
  2. A legal onus emphasising that the competent person (for examination), “must be sufficiently independent and impartial to allow objective decisions to be made”.

Where specific tooling, used by drilling machines, to enable the lifting process does not currently conform to LOLER inspection or examination, the manufacturer should be consulted to obtain the Safe Working Load (SWL) in order that the equipment can be added to an inspection regime.

Examination certification shall mirror Schedule 1 of LOLER and contain the following particulars:

  • Name and address of the company for whom the examination was made,
  • Address of the premises at which the thorough examination was made,
  • Sufficient identification of the drilling machine, its winches, ropes and lifting accessories including, where known, their date of manufacture,
  • The date of the last thorough examination,
  • The safe working load (SWL) of the drilling machine, its winches, its accessories, and the Factor of Safety (FOS) applied to each,
  • The type of examination e., six monthly inspection or annual examination or if after the occurrence of exceptional circumstances,
  • Identification of any part that had a defect which is or could become a danger to persons, detailing the description of the defect,
  • Any repair, renewal or alteration required to remedy a defect found to be a danger to persons,
  • Any defect which is not yet but could become a danger to persons, the time by which it could become such a danger, along with details of any repair, renewal or alteration required to remedy it,
  • The latest date by which the next thorough examination must be carried out,
  • Where the thorough examination included testing; the particulars of any test undertaken,
  • Name and competency qualifications of the person making the report,
  • Name and address of the examiner’s company / employer,
  • Name and address of the person signing or authenticating the report on behalf of its author,
  • Date of the thorough

What is the legal standing of AGS & BDA guidance?

Following good practice is not a legal requirement in itself, but should an organisation choose not to follow good practice, and something goes wrong, that organisation may well be found liable of a tort of negligence under the Health and Safety at Work Act, 1974 and face a financial penalty and or a custodial sentence for it’s Directors.

Essentially, the AGS and BDA has combined the constant application of PUWER and the two elements of LOLER to provide further documented good practice to follow for the drilling industry and thereby continue to improve drilling machine safety.

More information regarding the Application of PUWER and LOLER to Land Drilling can be obtained from the AGS website.

Article provided by the AGS Safety Working Group and BDA Safety Sub-Committee

Article

Introduction to Cone Penetration Testing

- by
Tags: Featured

Cone Penetration Testing (CPT) or Piezocone (Cone Penetration with pore water pressure measurement (CPTU)) have seen a significant increase in use over the last 20 years. It has grown from a rarely used test to forming a significant element of most ground investigations carried out today. The publication of documents such as Eurocode 7 and ISO standard has helped push the use of CPTs as a reliable and important method of gaining quality repeatable in situ data from the ground for design purposes.

Developments in the cone technology allowing equipment to be more robust has also helped, along with the ever-increasing number of sensors that can be added to a CPT to make the test even more powerful.

Test Procedure
The test procedure is clearly defined in the British Standard, BS EN ISO 22476-1. In its simplest form, a cone is pushed into the ground at a standard penetration rate. The cone is connected by an umbilical cable that feeds the data to the data logger and logging computer, which displays these results in real time on screen. The cone is pushed in using a series of 1-metre-long rods by a set of hydraulic rams inside the CPT rig.

There are several checks and some preparation of the cone that needs to be done before commencement of the test which is outlined in the British Standard in detail. These include things such as checking the dimensions of the cone, checking zero values, being aware of temperature differences and saturating the piezo element of the cone.

The test is carried out at a relatively fast rate of two centimetres per second, when compared to traditional drilling techniques. This enables between 100 to 150 metres of testing in a shift, depending on ground conditions.

It is also vitally important to fully understand the limitations of CPTs. A standard CPT rod is only 36mm in diameter and most rigs will push between 10-20 tonnes, so care has to be taken not to damage or break the equipment. A good understanding of the probable ground conditions is vital when deciding if CPTs will give you the required outcome on your site.

CPT Equipment
Cones
Cone technology has seen major developments over the past 20 years. The standard CPT cone now measures pore pressure and is referred to as a piezocone. The pore pressure element can also be mounted in one of three positions, depending on ground conditions and the purpose of the test. Over recent years, the importance of temperature effecting the electronics inside the cone has been recognised and this has led to better temperature compensation.

Cones have also moved from being analogue to digital, which has allowed for many more sensors to be added to a standard CPT to gain additional data. These include magnetometers for detecting unexploded ordnance and pile lengths; sensors that measure the natural gamma radiation in the soil which can assist in solution feature investigations and the seismic cone which can measure shear wave velocites down hole. A more detailed list is provided in Table 1.

There has also been a significant development in the application of environmental cones that are capable of measuring most types of contamination. Two common examples of environmental cones are the membrane interface probe and the optical imaging probe. These are used to rapidly map contamination plumes over large areas. A more detailed list of these cones are provided in Table 1.

Table 1. List of some of the different cones and modules commonly used.

Other cone types that are regularly used are the soil moisture probe, video cone with a camera mounted on the side that records an image and the hydraulic profiling tool which pumps out water as the cone is going into the ground to measure hydraulic conductivity. There are also specialist cones for working in very soft soils. These can be specially calibrated CPT cones or modified cones such as the ball cone and T-Bar.

Cones are not the only thing a CPT rig can push into the ground! There are specially modified vanes that can be used to measure shear strength directly and driven sampling systems. The CPT rig can also be used for installing instrumentation such as piezometers and inclinometers.

Rigs
CPT rigs come in all shapes and sizes depending on what is needed for each particular project. The larger the rig the more reaction weight it will have to push the cone in the ground. However, it is not always the case that you need a large rig to achieve the required depths in a certain ground condition. You also don’t always have the space for a large CPT rig so smaller ones may need be deployed instead.

Rigs are often divided into wheeled and tracked versions and these can come in different sizes. You can also get rigs that have both wheels and tracks on them, known as track-trucks. A good thing about the larger rigs is that they provide comfortable places for work not only for the CPT operator but also the supervising engineer.

Smaller CPT rigs such as crawlers can be between one and a half and three tonnes. These rigs typically come with some sort of anchoring system to provide extra reaction force for the test. The use of the anchors can slow down the overall operation and reduce the amount of testing that can be completed in a shift and consideration also needs to be taken for the potential to damage underground services, if used. The major advantage of these rigs is that they can be used to access difficult to reach locations and they are often used on Jack up platforms and pontoons for carrying out work over water.

There are even smaller rigs which are hand portable that are often used in basements. These are bolted to the concrete slab in the building which then provides the reaction force for the test. These can be run off an electric power pack which enables emission free testing inside a building with no need for fume extraction.

Furthermore, there are rigs that have been specially adapted for work in certain environments. The rail environment is a good example where rigs have been modified to fit on rail vehicles to enable testing to be carried out from the track.

Offshore is also a major area for CPTs and it is this industry that funded a lot of cone development research during the 1970s and 80s. The speed of the CPT and the quality of data that we get from it makes it ideal for work in marine environments. Rigs have been developed that are fully submersible which can be lowered to the seabed to carry out tests. Projects in this sector are commonly for pipeline routes and foundations for wind farms.

Data Processing
While performing a piezocone test, the measured data is automatically converted from millivolts to engineering units. The results of cone resistance qc, sleeve friction fs, and porewater pressure u2 are shown graphically on the computer screen, giving real time access to the interested parties. Inclination and penetration rate are also monitored; although they are not used directly in soil classification and geotechnical parameters derivation, they assist in the process of quality checking the data.

Data processing starts with generating the corrected cone resistance, qt and friction ratio, Rf through very simple calculations which involve measured results only. At this phase of data processing, Soil Behaviour Type, SBT can be plotted on one of the charts available based on qc/ qt and Rf to give a name to the soils encountered during penetration. To derive more soil properties, it is nearly always necessary to have information on groundwater conditions, GWL and density/unit weight, γ to establish total and effective vertical stresses, σv0 and σ’v, to derive pore pressure ratio, Bq and other normalized parameters, Qt and FR, which can be used to classify soils based on more advanced SBT charts, like Robertson 2016, which interpret soils strictly based on their behaviour (contractive or dilative, drained or undrained) instead of giving the geological descriptions (sand, silt or clay).

Furthermore, data processing continues with the derivation of geotechnical parameters based on many correlations published in the literature over the years linking the measured CPT/U data to the required soil properties. These correlations are incorporated into various software packages making it a very easy electronic process to plot the results on soil behaviour type charts and to generate all possible soils properties. However, the use of software to process CPTU results into geotechnical information should be done with care. Although these packages perform the mathematical calculations correctly, they are often used with too little basic information, experience and/ or knowledge (Powell & Dhimitri, 2022). A list of soil properties that can be derived from CPTU measured data is presented in Table 2.

Table 2. List of possible parameters to derive from correlations available in the literature.

Use of CPTs in Geotechnical Practice

CPTUs are a powerful tool not only for soil characterisation, but also to give extensive information on soil properties and their behaviour in situ. Over the years, they have proven to be very successful to provide information regarding the design parameters in difficult soil conditions. The use of CPTU tests is worthwhile in settlement evaluation, especially when you perform a dissipation test by stopping the penetration at the required depth and waiting for the excess pore water pressure to dissipate. This provides us with valuable geotechnical information such as ground water level at that position in that moment if the dissipation test is left to run to equilibrium, drainage conditions and consolidation parameters. Furthermore, measured or derived parameters from CPTs can be used to perform bearing capacity analysis for shallow and deep foundations.

CPTU based methods to assess the liquefaction potential (the phenomenon that turns solid ground into a liquid-like state) of soils are straightforward to determine the cyclic resistance ratio, CRR. They have proven to be very successful in tailings materials and regions prone to earthquakes. In addition, CPTUs are widely used as a quality check for ground improvement projects where cone resistance, qc pre and post ground improvement application helps the designers to make real time decisions. In areas where the geology is Chalk, cone penetration tests are becoming a cost-effective method to identify chalk and solution features, especially by taking measurements of the gamma radiation while penetrating the soils.

Reference
Powell, J. J. M., Dhimitri L. “Watch out for the use of global correlations and “black box” interpretation of CPTU data [taylorfrancis.com]”. 5th International Symposium on Cone Penetration Testing (CPT’22), 8-10 June 2022, Bologna, Italy. CRC Press. p. 651-656

Authors:
Darren Ward – Managing Director – In Situ Site Investigation Ltd
Luisa Dhimitri – Geotechnical Engineer – In Situ Site Investigation Ltd
John Holt – Pressuremeter Testing Manager – Senior Geologist, Insitu Testing

Article Sustainability

Brownfield and Biodiversity Net Gain – opportunities and risks

- by
Tags: Featured

Biodiversity net gain (BNG) is an approach to development that aims to leave biodiversity in a measurably better state than before. BNG is both an outcome and a process. The approach to BNG consists of ten guiding principles as outlined in the Good Practice Principles for Development[1] and in England, the application of an excel-based tool, the Biodiversity Metric 3.1 Calculation Tool[2] (hereafter ‘the Metric’), as a proxy measure of biodiversity. In this article, we will explore how the Principles for Development are essential to the best practice application of the Metric to avoid biodiversity being considered as a numbers game. We will also discuss the opportunities and risks presented by BNG and its delivery to the development of brownfield land.

Across the UK, the BNG approach is known and associated with policy and legislation to different degrees. In England, the Environment Act 2021 has made the BNG approach a mandatory requirement of planning permission. This primary legislation requires all size developments, excluding permitted development, to achieve a minimum of a 10% net gain in biodiversity for at least 30 years, demonstrated through the Metric. It will come into effect between 2023 and 2025 and tie in with secondary legislation providing further details of how the approach will work in practice. In the meantime, Local Planning Authorities already expect net gain to be achieved in developments, as required by the National Planning Policy Framework (NPPF); the difference being that the NPPF does not define a percentage.

In Scotland, Wales and Northern Ireland, legislation for BNG does not yet exist. Current policy, however, suggests the use of BNG as a valid and robust way to meet policy requirements. For example, in Scotland, the latest National Planning Framework 43 must implement the Planning (Scotland) Act 2019 stipulation for development to secure positive effects for biodiversity[3]. In Wales, under the Planning Policy Edition 11, there is the requirement for development to prevent biodiversity losses or compensate for losses where damage is unavoidable[4] and that any development must provide a net benefit for biodiversity. In Northern Ireland, Planning Policy Statement 2: Natural Heritage 2013 states ‘planning policies of this statement must have regard to any strategy designated for the conservation of biodiversity…’ and ‘protection and/or enhancement’ of ‘natural heritage features and designated sites’ is required[5].

This article will focus on England, where policy and legislation are most developed in BNG, allowing for better exploration of implications for brownfield land. However, many of the principles of how the approach works, as well as drawbacks and opportunities, could apply elsewhere in the UK.

Initially, Natural England, the relevant non-departmental public body, considered whether brownfield land should be excluded from the Metric. However, following a recently completed consultation[6], the government is proposing not to apply exemptions to brownfield sites that meet a set criteria. They state that ‘an exemption based on an appropriate combination of these criteria would deliver little added benefit and would greatly complicate the requirement’s scope for developers and planning authorities alike…. furthermore, many brownfield sites offer significant potential for achieving biodiversity net gain as they often have a low pre-development biodiversity value’[7].  Therefore, brownfield developments are seen to offer significant biodiversity value, especially in urban environments.

The habitats found on brownfield land vary from areas of remaining bare ground or hard standing, to ruderal and ephemeral vegetation, to grassland and scrub. Where a combination of these habitats occurs within a certain continuous area, they can fit the description of Open Mosaic Habitats on Previously Developed Land (OMH). The periodic disturbance and abandonment of the land replicates the ‘disturbance’ process found in natural ecosystems. Disturbance is often essential to ‘restart the clock’ of succession (the process by which the structure and mix of species and habitats in an area change over time). Disturbance supports the creation of a variety of habitats across a landscape, which in turn supports species diversity. This is where brownfield land can be valuable to biodiversity.

Brownfield land often falls into the category of a biodiversity rich habitat or one that is very poor for biodiversity. The type of species and habitats found on brownfield land are often rarer than those found in the countryside, with evidence suggesting between 12% and 15% of all nationally rare and scarce insects are recorded on these sites[8]. Whilst the countryside is often viewed as more biodiverse, many modern farming methods prevent the establishment of diverse habitats and species. Therefore, often brownfield land is more bio-diverse than the farmed countryside.

Where brownfield land does not have OMH and is classified as poor quality, it can offer significant opportunities for habitat banking. Habitat banks are habitats that are created in advance of development i.e., banked for later. When a development goes ahead, and the habitat can’t be saved, the habitat bank can be called upon to offset the habitat lost providing the previous steps of the mitigation hierarchy have been applied[9]. There are various opportunities with brownfield land to provide a bank. Where low scoring brownfield habitats are present, such as with hardstanding, bare ground or certain ruderal, ephemeral, grassland and scrub types, much can be done to improve biodiversity. For example, taking up the hardstanding to plant, planting up bare ground, adding more native species variety to existing grassland or scrubby areas, or adding a range of habitats instead of one.

As habitat banking is in its infancy, expert advice is necessary before setting up a habitat bank to ensure that the correct governance, registration (with the LPA but likely also with NE) and monitoring procedures are in place to meet the Environment Act (2021) requirements. Currently, there is no regulation around habitat banking; regulation is expected between 2023 and 2025 when BNG will become mandatory.

When brownfield land has low scoring habitats of condition and distinctiveness, they can  be used to contribute toward a development project to achieve net gain, as they can be replaced with almost any other habitat and result in significant biodiversity improvements. This is providing that they are not OMH or other priority habitats i.e., some ponds or native woodland. For example, a site consisting of one hectare area of bare ground provides 2 biodiversity units according to the Metric. Should two-thirds be lost to development and the remainder landscaped with native scrub, 2.21 units could be provided, making a 10% net gain.

In the UK, there is a focus on the remediation of brownfield sites. However, remediation can decrease habitat diversity if it involves intense management instead of natural processes. The addition of nutrient rich topsoil and seeding grass species that require intense management regimes homogenises sites, decreasing plant and animal diversity. Where remediation is not considered, brownfield sites are often neglected and result in scrub encroachment, which can in some cases reduce biodiversity.

High quality brownfield sites may be OMH, which must be considered separately. As a mosaic habitat it may include other habitats of principle importance and is not easily defined so its definition depends on meeting a number of quality criteria. It can be made up of a wide range of habitats including grassland, tall ruderal plant species, native and non-native invasive species and early pioneer communities and is particularly valuable to rare and declining invertebrates[10]. They are vital in ensuring high levels of biodiversity in the UK, supporting pioneer species and species that move between habitat patches, and providing refuge for others. OMH is a Habitat of Principle Importance under Section 41 of the Natural Environment and Rural Communities Act 2006 due to its ability to support a rich assemblage of invertebrates. To qualify it needs to be at least 0.25ha, have more than one specified habitat type within the mosaic, and meet other specific criteria including a known history of disturbance at the site[11].

Within the Metric, OMH is assigned a high ‘distinctiveness’ level. Distinctiveness is a term used in BNG to describe innate qualities of a particular habitat type and can range from very low to very high.  Due to the high distinctiveness of OMH, encountering a site with OMH can be problematic for the developer. Instead of losing and needing to replace 2 units/ha (as would be the case for bare ground), losing OMH habitat would result in the loss of at least 6 units/ha. OMH must also be replaced with the same habitat. Finally, OMH is considered to be of medium difficulty to create in the ‘difficulty to create’ risk factor of the Metric, meaning that it will likely only be successfully created two-thirds of the time. Thus, the Metric requires 1ha of lost OMH to be replaced with 1.9ha of the same habitat of the same quality.

One of the aims of the Metric is to disincentivise development on particularly valuable habitats, which might occur with OMH. However, though it is difficult to create, other habitats in the Metric are considered harder to create. OMH may also be easier to manage: because the habitat is a result of previous disturbance, more disturbance can be used to ‘reset its clock’. This could be as simple as clearing areas rotationally from time to time. Also, this habitat is only considered to require four years to reach moderate condition in the ‘time to target’ risk factor of the Metric, and ten years to reach time to target good condition. However, the site would need to be managed for 30 years under the Environment Act. It should be noted that each site is unique and there is no set time period in which OMH will develop. This period is dependent on various factors like the type of brownfield site, proximity to other landscape features, topology and climate. Furthermore, because the distinctiveness of the habitats is high, they produce high numbers of biodiversity units relative to their area. Finally, these areas punch above their weight in biodiversity terms compared to other habitats and can be particularly valuable in urban areas where other greenspace is lacking.  For these reasons, OMH could be a good habitat to investigate when setting up a habitat bank.

The government has identified that at least 300,000 new homes would need to be built in order to meet the increasing housing supply demands. It recently announced an initiative to promote the development of derelict sites into new homes under a new brownfield fund[12]. Whilst this is viewed as a way to boost local economies and home ownership, there is a significant risk to biodiversity and ensuring climate resilience within cities. Research has shown that ex-landfill sites contain assemblages of rarer birds, which could be lost through new housing developments (Macgregor et al., 2022)[13].

There are several opportunities associated with this type of habitat, including the multi-functionality of these sites and the creation of habitats from the start of the succession, thus supporting more biodiverse pioneer species than had previously occurred.  Additionally, naturally occurring OMHs, which develop as a result, will enhance biodiversity in a fragmented landscape through the creation of habitat corridors, which will have an overall significant beneficial impact on future biodiversity.

In conclusion, brownfield sites, through the presence of OMH, can have greater biodiversity than that of countryside land and other land within the UK, as shown through the Metric. This increased biodiversity uplift in both condition and distinctiveness occurs through the development of OMH on brownfield land that is in a poor condition. However, to realise these benefits, further awareness is required including the correct management regime of these sites and to increase the public and developers’ perception of the benefits of these sites. OMH provides vital successional habitats for a wide variety of species if the natural ecosystem process is allowed to occur. These habitats are Habitats of Principle Importance and are key to enhancing biodiversity, climate resilience and wider natural capital benefits.   These sites have commercial potential through offering habitat credits (i.e., a unit of trade that places monetary value on habitat preservation or restoration[14]) to both developers and Local Planning Authorities via the creation of habitat banks.  However, allowing OMH to occur on these sites is not considered in line with the current government plans to build new homes and boost the local economics.

References:

[1] CIEEM, CIRIA, IEMA (2016) ‘Biodiversity Net Gain: Good practice principles for development

https://cieem.net/resource/biodiversity-net-gain-good-practice-principles-for-development/ Biodiversity-Net-Gain-Principles.pdf (cieem.net)

[2] Natural England (2022), The Biodiversity Metric 3.1. The Biodiversity Metric 3.1 – JP039 (naturalengland.org.uk)

[3] Planning (Scotland) Act 2019 [online]. Available at: https://www.legislation.gov.uk/asp/2019/13/section/2/enacted

[4] Welsh Government. Planning Policy Edition 11 [online]. Available at: https://gov.wales/sites/default/files/publications/2021-02/planning-policy-wales-edition-11_0.pdf

[5] Department of the Environment (2013). Planning Policy Statement 2 Natural Heritage [online].

Available at: https://www.infrastructure-ni.gov.uk/publications/retained-planning-policy

[6] Department for Environment Food & Rural Affairs (2022) ‘Consultation on Biodiversity Net Gain Regulations and Implementations.  https://consult.defra.gov.uk/defra-net-gain-consultation-team/consultation-on-biodiversity-net-gain-regulations/ (accessed 01/08/222). Results expected Autumn 2022.

[7] Department for Environment Food & Rural Affairs (2022) ‘Consultation on Biodiversity Net Gain Regulations and Implementations. https://consult.defra.gov.uk/defra-net-gain-consultation-team/consultation-on-biodiversity-net-gain-regulations/ (accessed 01/08/222). Pg 26.

[8] Lush.M., Kirby.P., & Shepherd.P. (2013) ‘Open Mosaic habitat survey handbook’ Open Mosaic Habitat Survey Handbook (buglife.org.uk) (accessed 29/07/22).

[9] Chartered Institute of Ecology and Environmental Management (2021) ‘Good Practice Requirements for Delivering Biodiversity Net Gain (On-and Off-site)

[10] https://www.nature.scot/sites/default/files/2018-02/Priority%20Habitat%20-%20Open%20Mosaic%20Habitats%20On%20Previously%20Developed%20Land.pdf#:~:text=The%20Open%20mosaic%20habitats%20on%20previously%20developed%20land,sites%20support%20good%20examples%20of%20this%20priority%20habitat. (accessed 01/08/22)

[11] Riding, A., Critchley, N., Wilson, L. and Parker, J. 2010. Definition and mapping of open mosaic habitats on previously developed land: Phase 1. Defra Research Report WC0722. London, Department for Environment Food and Rural Affairs.

[12] Department for Levelling Up, Housing and Communities (2022). ‘Derelict sites to be transferred into new homes as new brownfield sites opens’ https://www.gov.uk/government/news/derelict-sites-to-be-transformed-into-new-homes-as-new-brownfield-fund-opens (accessed 29/07/22).

[13] Mcgregor.C., Bunting. M., Deutz.P., Bourn.N., Roy.D., Mayes.W. ‘Brownfield sites promote biodiversity at a landscape scale. Science of the Total Environment, Vol 804, Jan 2022, 150162.

[14] Garnter.T., (2010) ‘Habitat Credit Trading’ PERC Reports, Volume 28, No.1.

Article provided by Hannah Williams (Principal Ecologist, BNG) & Harriett Ricketts (Natural Capital Specialist) – WSP

Image credit to Andy O’Dea, Cognition Land and Water

Article Sustainability

New SoBRA Guidance on the Incorporation of Future Climate Change Effects into Controlled Waters Risk Assessments of Land Contamination

- by
Tags: Featured

Overview

In May 2021 a SoBRA sub-committee was established to develop guidance to help practitioners in the land contamination sector to account for climate change effects in controlled water risk assessments (CWRA) in a robust and consistent manner.  The sub-committee has representatives from geo-environmental consultancy and UK regulatory bodies (a full list of contributors is provided at the end of this article).  The full guidance entitled “Guidance on assessing risk to controlled waters from UK land contamination under conditions of future climate change” (V.1.0, dated August 2022), will soon be available for download from the SoBRA website[1].

Context

Climate change is expected to alter the frequency and distribution of rainfall, increase atmospheric temperatures, and increase the frequency and severity of extreme weather events, leading to longer periods of drought and more extreme rainfall events with associated rising groundwater and surface water levels causing flooding and coastal inundation. Furthermore, long-term changes in climate are forecast with the Meteorological Office projecting that by 2070, on average across the UK, summers will be between 0.9 and 5.4 ᵒC warmer, and winters will be between 0.7 and 4.2 ᵒC warmer[2].  Precipitation is also expected to be affected, with a -47% to +2% UK average change during the summer months, and a -1% to +35% change during winter months[3].  The projected pattern of rainfall across the UK is not uniform and will continue to vary on seasonal and regional scales into the future – see information provided by the Met Office[4] for seasonal and regional variations.

Changes in recharge rates, and to a lesser extent atmospheric temperature, can be important factors in determining the outcome of CWRAs[5]  being completed to assess the impacts to receptors from contaminant sources.  Climate change could therefore alter the risk posed to controlled waters (including to groundwater resources, surface water bodies, marine bodies, and groundwater-dependent terrestrial ecosystems), and the required management of these risks.

The need to incorporate the predicted effects of future climate change into qualitative and quantitative risk assessments has been recognised but rarely implemented in practice. This need is set out within the Environment Agency’s 2010 “Managing and reducing land contamination: guiding principles (GPLC2) FAQ 8”, and within the National Planning Policy Framework (NPPF) for England and Wales and LCRM. It is understood that the National Planning Framework 4 and WAT-PS-10 in Scotland will also in future include the need to consider climate change within land contamination risk assessments. Within the recently published BS21365[6] there is a requirement to consider and identify ‘possible foreseeable events’ within CSMs that could affect contaminant impacts or create new exposure pathways, e.g. flooding, rising groundwater or seawater levels and extreme weather which all go hand in hand with climate change. The absence of published UK guidance has resulted in variable ways of inclusion of climate change effects into CWRA, or, more usually, the influence of climate change being ignored entirely.

Effect of Future Climate Change on Controlled Waters Risk Assessments

All CWRA are underpinned by a conceptual site model (CSM), which synthesises the key physical, chemical, and biological processes that characterise the system, and establishes any potential Source-Pathway-Receptor linkages (i.e. no linkage, no risk).

Figure 1: Indicative CSM considerations based on a climatic shift to ‘wetter’ weather.

Future climate change could foreseeably affect any given CSM.  For example, an increase in precipitation could lead to increased recharge resulting in rising groundwater levels; source (e.g. soil) erosion; or overland flow.  It can further be seen how these scenarios could affect the pathways from source to receptors e.g. unsaturated zone thickness, hydraulic gradients and dilution factors, or the introduction of new pathways e.g. from overland flow, or previously unsaturated drains/culverts acting as new preferential pathways (see Figure 1).  As a result of the change in pathway, the number and type of receptors may also be affected, all of which could change the calculated ‘risk’ posed to controlled waters[7].

Figure 2: Indicative CSM considerations based on a climatic shift to ‘drier’ weather.

By way of another example, an increase in extended periods of hot dry weather or drought i.e. as predicted for the summer months, could result in reduced overland flow; falling groundwater levels which could, for example, change the pathway length by increasing the unsaturated zone thickness or increase dependency of baseflow to rivers; source drying increasing the risk of wind erosion/dust generation, and the development of desiccation cracks creating preferential vertical flow paths; changes in water demand e.g. through the installation of new abstraction wells or enhanced drawdown.  All of which could again alter the calculated ‘risk’ posed to controlled waters (see Figure 2).

In line with industry standards (e.g. LCRM[8]), the SoBRA guidance recognises that any change to a CSM (due to future climate change effects) must be determined by a suitably qualified and experienced professional, using evidence-based reasoning, and that the risk assessment process should only progress to higher tiers (i.e. generic quantitative and detailed quantitative) if the risk cannot be determined ‘acceptable’ at the preliminary stage.  The SoBRA guidance supports practitioners in doing this by setting out “What-if” scenarios for source, pathway, receptor CSM components that could be affected by climate change, in order to guide evidence-based reasoning. This is in line with the approach detailed in BS21365.

Adequacy of Available Datasets

The current best source of information for understanding future meteorological (e.g. temperature and precipitation) and sea level rise projections is the Met Office UK Climate Projection (CP) 18[9] dataset. This dataset was primarily developed to inform water resource management and flood risk assessment and as such the data modelled under the worst case high emissions scenario (RCP 8.5) is the most comprehensive, particularly when considering effects at the local scale. Projections are available until the end of the century. The projections consider average effects and do not necessarily include the effects of extreme events.

The Enhanced Future Flows and Groundwater[10] (eFLaG) Project, which is based on UKCP18 meteorological data, is the most up to date source of information detailing projections to recharge and river flows. This may be a more useful data source in relation to understanding changes to the hydrogeological CSM in relation to future climate change.

The choice of data set used to understand future climate change influences on the CSM is ultimately the responsibility of the risk assessor and should be suitably justified with uncertainties and limitations clearly stated. As the effects of climate change vary seasonally and spatially across the UK, careful consideration should be given to the site setting when choosing the appropriate climate model output for use in risk assessment.

Adequacy of Available Modelling Tools

Commercial modelling tools used in the higher tiers of risk assessment e.g. the Remedial Targets Methodology worksheet (‘P20’)[11], and ConSim[12], currently assume environmental conditions remain constant, however, the effects of future climate change are projected to vary over time, and so therefore will the established pollutant linkages.

This poses a challenge for practitioners with tools ill-equipped to model changes to the values of parameters over time.  Although distributed flow models exist (e.g. MODFLOW and FEFLOW), in addition to compartmental modelling environments (e.g. ConSim), the data requirements, time, and computational and staff resources required to develop and run these models is unlikely to be proportionate to most routine land contamination risk assessments.

It is therefore evident that further tools need to be developed (or current tools adapted) to model the transient effects of future climate change.  However, until such time, the SoBRA guidance recommends that existing tools are employed, except where risks are borderline acceptable (in which case an existing transient modelling approach may be most appropriate).  The SoBRA guidance sets out recommendations for how this can be achieved using commercially available tools.

SoBRA Sub-Committee Members

David Drury (Golder Associates / WSP); Emma Evans (Arcadis); Emma Hipkins (Golder Associates / WSP); Emma Khadun (The LK Group); Helen McMillan (RSK Geosciences); Isla Smail (The Scottish Environment Protection Agency); James Wilson (Atkins); Jesse Davies (Ramboll); Jonathon Atkinson (The Environment Agency); Katie Gamlin (WSP); Leon Warrington (Hydrock); Roisin Lindsay (WSP); Sarah Poulton (Natural Resources Wales); and Suzanne Blackman (Mott MacDonald).

We would also like to thank Simon Cole (SoBRA chair) and the wider SoBRA Executive Committee for their support and contributions in making this guidance possible.

[1] https://sobra.org.uk/

[2] UK Climate Projections: Headline Findings.  July 2021 (available at https://www.metoffice.gov.uk).  Values presented are based on Met Office high emissions projections (RCP8.5) for 10% and 90% probability levels.

[3] Where a negative value denotes a reduction in precipitation.

[4] UKCP18 Climate Change Over Land (available at https://www.metoffice.gov.uk).

[5] Controlled waters is a term used in legislation in England and Wales. Its equivalent in Scotland is the water environment. It is understood that Northern Ireland use both terms. Throughout this article the term ‘controlled waters’ is used to refer to regulated groundwater and surface water throughout the UK.

[6] BS EN ISO 21365:2020 Soil quality – conceptual site models for potentially contaminated sites

[7] Changes to a Conceptual Site Model can also be envisaged because of increases in the frequency and duration of extreme cold weather events, changes to wind intensity and duration, pluvial or groundwater flooding, marine inundation, and river or coastal erosion.

[8] Land Contamination Risk Management Guidance.  Available at https://www.gov.uk/government/publications/land-contamination-risk-management-lcrm

[9] https://www.metoffice.gov.uk/research/approach/collaboration/ukcp

[10] https://www.ceh.ac.uk/our-science/projects/eflag-enhanced-future-flows-and-groundwater

[11] https://www.gov.uk/government/publications/remedial-targets-worksheet-v22a-user-manual

[12] http://www.consim.co.uk/

Article provided by Dr. Emma Hipkins, Helen McMillan, and Isla Smail on behalf of the wider SoBRA Climate Change and Controlled Waters sub-group.

Article

Q&A with Alex Dent

- by
Tags: Featured


Full Name: Alex Dent
Job Title: Associate Director
Company: WSP UK Ltd

I have 25years experience in ground engineering, covering a wide variety of ground conditions, market sectors, geotechnical structures and deliverables. I have worked on UK and international projects. I have extensive experience in the design of foundations, basements and earthworks and in the assessment of ground movements and slopes. I am WSP’s Geotechncial Net 0 lead and mentor a number of junior team members on their route to chartership. I believe that the best way to deliver cost effective ‘joined up’ design solutions is through close collaboration with our structural, civil engineering and geo-environmental colleagues.

What or who inspired you to join the geotechnical industry?

Desperation! I graduated from a B.Sc in Geology and Geophysics (University of Durham) in the mid 90s recession and jobs in the oil and gas sector were hard to come by. Out of desperation I researched other geological opportunities and Engineering Geology came up as an option. It sounded like and interesting technical challenge involving geology, physics and maths. I also liked the idea of an industry that that provides direct benefit to society.

What does a typical day entail?

There is no such thing a typical day! But broadly speaking this week; Providing technical advice for the ground investigation on part of HS2, reviewing settlement monitoring data on another project, resolving contactor queries on a slope stabilisation project, line management duties, progressing WSPs Net 0 priorities and duties as an AGS Committee member.

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

Geotechnical design for the award winning Proton Beam Therapy Centre for UCL Hospitals – at 24m, then London’s deepest basement with nearby tube tunnels, Thames Water assets and surrounding buildings all requiring consideration.

Freetown, Sierra Leone. A lovely locally based client team and a project with great vision and the potential to raise people out of poverty.

What are the most challenging aspects of your role?

Clients, or perhaps more correctly, their Project Managers and QSs, nearly all mistaking cost for value. Clients should be educated to ‘invest’ in ground investigation and ‘invest’ in design – this could pay substantial dividends over the project lifecycle. But no: they would sooner quibble over a handful boreholes or ‘brow beat’ over design fees etc.

The industry wide lack of qualified and suitably experienced engineers/geologist, with resultant resourcing issues is a challenge. This challenge is only going to get harder if the numbers taking up geology degrees continues to decrease.

The theories behind our designs assume that soils are homogenous and isotropic. They aren’t. We only sample (let alone test) as small fraction of the ground we are modelling. There also a number of factors that may influence a given soil parameter, e.g. strain magnitude. Modelling of the ground is therefore a perpetual joy and challenge.

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

I am the leader of the AGS Geotechnical Working Group (GWG). My focus is to ensure that our meetings are stimulating and provide tangible results for the benefit of the AGS membership. The GWG are looking at a number of matters relation to Net 0 in geotechnical design, the next generation of Eurocodes and a number of other interesting topics.

What do you enjoy most about being an AGS Member?

Sharing knowledge.

What do you find beneficial about being an AGS Member?

A sense of community; we are all in this together. We are facing the same challenges and generating guidance to benefit of each other.

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

It provides some great resources which are really helpful for briefing and guiding more junior team members. It helps ensure that the quality of work produced by its members is of a suitable standard, and hence drives up standards for the industry as a whole. Through the Ground Forum, its gives us a collective voice.

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

A change in Client’s/QS’s/Project Manager’s attitude to geotechnical engineering – Geotechnical engineering is not a bolt on to a Geoenvironmental investigation required to discharge a planning application. When we write a report it is meant to be read, understood and its advice considered – not ‘ticked’ as done and then filed.

A chance to be ‘on the top table’ and present the findings of our reports and our design solutions directly to clients. This might help them better understand the issues that their projects face, the key role we play in helping them manage their risks, the value geotechnical engineers can bring to a project and ultimately help them to ‘invest’ in what we do.

Some better quality logging (and checking of logs prior to issue) would be nice too – how is it 25years in and I still see logs with ‘stiff SAND’, ‘dense CLAY’, ‘very sandy very gravelly CLAY/SILT with many cobbles and boulders’ and the like in factual reports?