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Celebrating 20 Years at Hawkins: Dr Richard J Fletcher

Chloe Duggan — Fri, 24 Jul 2026 08:14:59 +0000

This month, we are proud to celebrate an incredible milestone as Dr Richard J Fletcher, Principal Associate and Fire & Explosions Expert in our Birmingham office, marks 20 years of service with Hawkins.

Since joining Hawkins in 2006, Richard has investigated more than 1,400 fire and explosion incidents, building a reputation for scientific rigour, impartiality, and technical excellence. His work has spanned everything from domestic fires and large-scale industrial losses to complex personal injury investigations involving fireworks.

Reflecting on his two decades at Hawkins, Richard said:

“I will never forget visiting my first fire scene 20 years ago with a colleague, seeing the destruction caused and then, over the years, learning how to identify the often subtle evidence that assists in determining the origin and cause of a fire. I can’t quite believe that it has been 20 years since I joined Hawkins!”

To mark the occasion, we sat down with Richard to look back on his career so far.

What brought you to Hawkins?

I obtained a BSc in Applied Chemistry from Portsmouth University, followed by a PhD focused on microbial corrosion. After that, I joined a small family-run company in Dorset, where I worked on non-destructive testing techniques, corrosion and materials failures.

While working there, I met and worked alongside Mr Rod Newbury, a former Managing Director of Hawkins, on the investigation of a rail accident. When that project came to an end, I approached Hawkins about potential opportunities, but there were no vacancies at the time. Around a year later, I received a call inviting me to interview for a Fire Investigator position in the Birmingham office. That opportunity ultimately led to what has now been a 20-year career with Hawkins.

How has your role evolved over the last 20 years?

The fundamental principles of fire investigation have not changed and never will. However, it has been fascinating to see how safety legislation has reduced some common causes of fire, such as smoking-related incidents and certain electrical failures.

At the same time, I’ve seen new fire risks emerge, particularly the significant rise in fires involving lithium-ion batteries.

Technology has also transformed the way we work. When I joined, I was fortunate to be given a digital camera while many colleagues were still using film. Smartphones soon followed, giving instant access to emails, and today we use tablets instead of paper. We also have access to drones, which allow us to safely view and document fire scenes from above.

Can you describe a case or moment that stands out as especially meaningful?

In 2012, just six years after joining Hawkins, I attended a fire involving a building approximately 140 metres long and up to 75 metres wide, with around three-quarters of the structure having collapsed. It remains one of the largest fire scenes that I have ever attended.

The investigation dominated the next two-and-a-half years of my career and ultimately resulted in a successful outcome for the insurer involved.

Another memorable experience was assisting with the investigation of an incident in the Channel Tunnel. We had to enter the tunnel at night, travelling on an open-topped service train. It was certainly one of the most unique locations I have ever visited.

I may also be one of the few people who can say they have investigated a fire caused by a medieval-style trebuchet!

What’s your favourite memory with your team?

The annual company meetings have always been a highlight. With colleagues spread across numerous offices, it’s a great opportunity to spend time together in person.

Over the years, I’ve had the chance to take part in activities I would probably never have experienced otherwise. Two that stand out are herding geese with a sheepdog and building rockets. One particularly memorable company meeting even featured a Spitfire aerobatics display during the evening entertainment.

What motivates you to come to work every day?

Fire investigation is unlike almost any other scientific profession. I often tell people that I rarely know what I’ll be doing the following week.

You always need to be prepared to change plans at short notice and attend a fire scene, and that unpredictability keeps the role interesting. Every investigation presents its own challenges and an opportunity to learn something new.

How has Hawkins supported you over the last two decades?

One of the things I value most about Hawkins is its commitment to training and professional development.

During my time here, I have been able to attend a wide range of specialist courses, including two pyrotechnics-related programmes:

-Practical Pyrotechnics – Stage/Theatre and Explosives Safety

– Handling Part 1 – TV/Film Pyrotechnics.

Hawkins has always recognised the importance of investing in training, and those opportunities have allowed me to broaden my expertise and develop specialist knowledge that has been invaluable throughout my career.

Read Richard’s article on Pyrotechnics here: Pyrotechnics in Engineering: Beyond Fireworks

Richard’s 20-year journey is a testament to his dedication, expertise and enthusiasm for fire investigation. From major industrial losses and unique challenges in the Channel Tunnel to investigating a fire caused by a trebuchet, his career at Hawkins has been anything but ordinary.

Congratulations, Richard, on this remarkable milestone, and thank you for your outstanding contribution to Hawkins over the last 20 years. We look forward to seeing what the next chapter brings.

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Stormwater Management on Bridges

Chloe Duggan — Sun, 19 Jul 2026 18:36:51 +0000

Bridges play a vital role in our daily lives by connecting areas separated by natural or man-made barriers, enabling efficient transportation and access. China has over 1 million bridges (CEIC, 2023), and Hong Kong alone currently has 1475 flyovers and road bridges (Highways Department, 2025). Each bridge contributes to ensuring smooth traffic flow and supporting daily commutes.

Bridges are typically designed to last more than 100 years; therefore, ensuring long-term performance is critical. Every year, billions of dollars are allocated to maintaining bridges worldwide and this figure is expected to rise as new bridges are constructed and existing ones age. A well-designed and properly maintained bridge will contribute to both its durability and reduced maintenance costs.

Among the many aspects of a bridge structure, stormwater management is particularly crucial. Poorly designed, installed, or maintained drainage systems can lead to water accumulation in undesirable areas, accelerating the deterioration of structural components and creating safety hazards for users and the surrounding environment, as shown in Figure 1. Effective drainage design and maintenance not only extend a bridge’s lifespan, but also reduce overall operational costs and improve safety.

This article provides an overview of stormwater management in bridge structures, with a particular focus on surface runoff control in concrete bridges and its role in ensuring structural safety and long-term durability. References to established design standards, including the UK’s Design Manual for Roads and Bridges (DMRB) and the Hong Kong Structures Design Manual 2013 (HKSDM2013), are included where applicable to illustrate best practices and regulatory guidance.

Discussion

Stormwater on a bridge is generally managed through four key methods: Structural Elements, Deck Drainage, Waterproofing Membranes, and Watertight Joints.

1. Structural Design

During the design stage, structural engineers and architects have the opportunity to incorporate strategies into the bridge geometry, surface shaping, and reinforcement detailing to minimise stormwater accumulation, often at little or no additional cost.

> Bridge geometry should ideally prevent standing water or ponding by incorporated appropriate longitudinal and transverse deck gradients. The UK’s DMRB-CD358 recommends a minimum longitudinal gradient of 1:100. Unfavourable geometries, such as vertical sags (Figure 2), can lead to water accumulation and should be avoided whenever possible. Where they are unavoidable, special attention to drainage and detailing is required.

> Structural shape plays a key role in stormwater management. Sloping the surface finish, such as on the bridge deck and bearing seat areas, helps prevent standing water by allowing it to flow naturally out of the horizontal surface towards designated drainage points. Drip edges and grooves are also important, as they help direct water away from structural surfaces. HKSDM2013 provides visual examples of both effective and poor practices for designing drip edges and grooves (see Figure 3). Any gaps exposed to stormwater should be avoided or properly sealed.

> Reinforcement detailing: Design codes and standards typically require crack width calculation to ensure that the size, number, and spacing of reinforcement bars are appropriate. This helps prevent excessive cracking from forming during the service, which could otherwise allow water to penetrate the concrete more rapidly and accelerate deterioration.

2. Deck Drainage

The deck drainage system consists of the intake, the drainpipes, and the outlet. Stormwater enters through the intake and is delivered through the drainpipes all the way to the outlet, where it connects to a local drainage system or natural water body. Poor design and maintenance can lead to several problems:

> Inadequate drainage design: Insufficient drainage capacity can lead to water build-up during heavy rainfall, leading to overflow into unwanted areas. This creates hazards for users and the surrounding environment. Incorporating drainage design from the early stages of bridge design is essential to achieve effective drainage.

> Blockages: Debris carried by stormwater can cause blockages, so drainage systems should be designed for ease of maintenance. Regular inspection routines are also crucial to ensure issues are identified and resolved promptly.

> Unsuitable materials: The material chosen should be durable and require minimal maintenance. Design codes often specify suitable material types. For example, HKSDM2013 requires the use of Unplasticized Polyvinyl Chloride (uPVC) for drainpipes in Hong Kong.

3. Waterproofing Membrane

A waterproofing membrane is an additional impervious layer, typically made of bitumen, polymer, or cementitious materials, applied over the bridge deck to prevent direct water ingress. Selecting the appropriate material for each specific project is crucial to ensure effective waterproofing.

These membranes can be applied in different forms, such as liquid, sheet, or spray. It is essential to adhere to relevant design codes when applying waterproofing to ensure long term effectiveness. Improper application can lead to issues such as insufficient bond strength, leakage due to poor detailing, and damage due to construction activities.

4. Watertight Joint

In modern bridge design, continuous bridges are increasingly favoured over simply supported designs. This shift is largely due to the risks associated with bridge joints, which are prone to leakage, deterioration, and high maintenance demands. Modern design codes such as HKSDM2013 and DMRB CD350 include clauses encouraging designers to minimise joints wherever feasible.

In certain circumstances, joints might be unavoidable, for example monolithic connection at abutments or when connecting new structures to existing ones. Such cases present their own challenges, and using a movement joint can be a safer and more economical design choice. In these cases, joints must be fully watertight, and access for maintenance must be considered in the joint design.
Joint watertightness can be achieved through, proprietary watertight movement joints or integrating drainage systems within the joint. If joints are not watertight, accumulated water can lead to:

Role of Technology in Bridge Drainage maintenance

maintaining drainage systems on bridges can be labour and cost intensive, especially for long bridges spanning challenging terrains such as seas or valleys. The use of modern technologies can improve safety, enhance maintenance quality, and reduce operational costs. For example, CCTV cameras installed on bridges allow personnel to inspect drainage inlets and identify surface blockages or flooding without the need of road closures or traffic diversions. Drones and drain inspection cameras (Figure 7) can inspect hard-to-reach locations, such as drainpipes running at the underside of the bridge. Various sensors (flow, pressure, moisture, etc.) combined with artificial intelligence have the potential to support real-time monitoring, early detection of anomalies, and predictive maintenance planning. These approaches reduce the likelihood of sudden failures and help maintenance teams respond proactively.

Final Remarks

Stormwater management on bridges is a well-established aspect of bridge design, addressed by various design standards such as HKSDM2013 and DMRB. Adhering to these guidelines when designing both the structure and the drainage system results in more durable, reliable and cost effective bridges. In summary, stormwater management on bridge is achieved through:

Structural design: bridge geometry, element shape, and reinforcement detailing.
Good deck drainage system design and maintenance.
Application of appropriate waterproofing membranes.
Provision of watertight joints and minimisation of joints where possible.

Technologies such as CCTVs, drones, inspection cameras, and smart sensors powered by AI are increasingly important for improving the safety, quality, and cost-effectiveness of bridge drainage maintenance. These tools enable remote inspections, real-time monitoring, and predictive analysis making them particularly valuable for long bridges spanning challenging terrains.

About the Author

Eng Phin is a structural engineer with over 10 years of experience in bridge and building design. He began his career in Indonesia, contributing to major bridge projects such as the Semanggi Interchange Upgrade and Kualanamu Light Rail Transit system. His expertise spans modern bridge construction methods, temporary works, and post-tensioning.

He has since worked on international projects in Hong Kong and beyond, applying local and global design standards while promoting digital engineering in structural design.

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Paul Lemon

Lorraine — Wed, 15 Jul 2026 08:59:56 +0000

Paul is a full-time specialist in the niche area of slips, trips and stair fall incident investigation, and leads Hawkins’ work in this area. He is a sought-after Expert Witness in this field, regularly preparing reports and giving evidence in Court.

He was part of the small HSE team that developed HSE’s early understanding of the causes of pedestrian slips, trips and stair falls. Paul’s work at HSE’s Laboratories (HSL) involved leading and coordinating research in these subject areas, and led to him serving as HSE’s principal Expert Witness for cases involving pedestrian accidents, presenting evidence to Magistrates’ Courts, Crown Courts and at Coroner’s Inquests.

On becoming HSL’s Research Technical Leader for slips, trips and stair falls, Paul continued to lead HSL’s research into these subjects, including their input into a large pan-European research project and managing the two largest research projects into slips and falls ever undertaken by HSE. He maintained responsibility for the authorisation of HSL’s slip, trip and stair fall forensic reports and represented HSE on several British Standards Committees, taking part in the production of numerous HSE Guidance documents and National Standards (such as BS7976-2 and BS5395-1) concerning slips, trips and stair falls.

He has developed a substantial list of publications in this subject area, is a long-standing, active Member of the UK Slip Resistance Group (UKSRG) and was the Editor of Issue 5 of the UKSRG Guidelines. He is a Chartered Scientist, a Chartered Physicist and a Fellow of the Institute of Science & Technology.

Paul joined Hawkins in 2009, and is a Principal Associate and Regional Manager of our Leeds Office.

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Sandra Rustomji

Chloe Duggan — Tue, 07 Jul 2026 14:22:26 +0000

Sandra is a Business Development Manager at Hawkins, with experience across sales, lead generation, marketing, and client engagement within the insurance, legal, technology, and wider professional services sectors.

She focuses on building and maintaining long-term relationships with clients and stakeholders by developing a strong understanding of their needs and connecting them with the appropriate expertise within Hawkins.

Sandra is fully bilingual in English and Spanish, enabling effective communication with a diverse range of clients and international stakeholders. She has experience working across international markets, including Europe, North America, and Latin America, within commercially driven, client-facing environments.

Her background also includes working with clients across a range of professional sectors, strengthening her ability to adapt to different industries and stakeholder requirements. She supports clients and key stakeholders by ensuring they are connected with the right experts to meet their needs.

Please contact Sandra if you have any queries or need advice on the appointment of an expert.

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Hawkins Recognised with Ninth Consecutive RoSPA Gold Award

Chloe Duggan — Mon, 06 Jul 2026 10:02:53 +0000

Hawkins has once again been recognised by the Royal Society for the Prevention of Accidents (RoSPA), securing a Gold Award for a ninth consecutive year. This 2026 recognition highlights Hawkins’ consistent and embedded approach to protecting the health, safety, and wellbeing of everyone across the organisation.

RoSPA’s awards programme is the largest of its kind globally, celebrating organisations that demonstrate exceptional performance in accident prevention and workplace safety. Now in its 70th year, the scheme assesses how effectively businesses manage health and safety through strong leadership, employee engagement, and continuous improvement.

Commenting on the achievement, Health and Safety Manager Stuart Mitchell said:

“Achieving nine consecutive RoSPA Gold Awards is a significant milestone for Hawkins. It reflects the commitment of our people to putting safety at the heart of everything we do and reinforces our belief that strong health and safety standards are fundamental to sustainable success. ”

As Hawkins continues to grow, we remain firmly focused on maintaining the highest standards of health, safety, and security for our colleagues, partners, and the communities we work with.

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Acoustic Design In School Buildings

Chloe Duggan — Mon, 22 Jun 2026 08:02:35 +0000

Acoustics is an important factor to consider when designing school buildings, because it affects the quality of communication and learning in classrooms and other spaces. Poor acoustics can make it difficult for students and teachers to hear and understand each other, leading to frustration, fatigue, stress, and reduced academic performance. Good acoustics can enhance speech clarity and create a comfortable and productive learning environment.

The UK Department of Education published the Acoustic Design of Schools: Performance Standards, Building Bulletin 93, in 2014. This set out the requirements for indoor ambient noise levels, reverberation times, and sound insulation for new and refurbished school buildings. These requirements are also linked to the Building Regulations, the School Premises Regulations, and the Independent School Standards.

One of the main factors affecting classroom acoustics is the indoor ambient noise level, which is the sound level in the room when no one is speaking. This noise can originate from external sources, such as traffic, construction, or playgrounds, as well as internal sources, such as ventilation, heating and cooling systems, or other equipment. High indoor ambient noise levels can mask or interfere with the speech signal, making it harder for listeners to hear and comprehend what is being said. Low indoor ambient noise levels can allow quiet, yet audible, disturbances to be far more distracting than they usually would be. This can affect the ability of students to follow instructions, participate in discussions, and concentrate on their work.

Another factor that affects the acoustics of a classroom is the reverberation time of the space. In layman’s terms, it is the ‘echo’ in a room, but technically, it is defined as the time it takes for an impulsive sound (such as a hand clap or a balloon burst) to decay by 60 decibels. Reverberation is caused by sound reflecting off the room’s surfaces, such as walls, ceilings, floors, or furniture. Reverberation targets vary depending on the type of room and activity planned for the room. For instance, a piano rehearsal music room will not have the same requirements as a classroom, and a dining hall will not have the same requirements as an assembly hall. This is because reverberation can be detrimental to speech, especially in large or crowded rooms, but is not necessarily detrimental to music in the same way. Long reverberation times can make speech sound muffled, distorted, or ‘echoey’, reducing its intelligibility and increasing the listening effort. It can also affect the vocal health of teachers, who may have to strain their voices to speak louder or more clearly. This can affect students’ learning outcomes, especially those with hearing impairments, language difficulties, or special educational needs (SEND).

Acoustics is especially important for the design of SEND schools because many students have hearing or communication challenges, or other conditions that affect their listening and learning abilities. According to the 2010 Equality Act, all schools have a responsibility to improve their accessibility plans for pupils and staff, and this includes providing optimal acoustic conditions.

Some of the strategies that acoustic engineers can use to improve the acoustics of schools include:

Choosing a suitable location and orientation for the school building, away from noisy sources or facing away from them to minimise the impact of external noise on the school environment
DevelopmentUsing sound-absorbing materials and finishes, such as acoustic tiles, panels, or carpets, to reduce reverberation s that could be affected by sources of flooding other than rivers and the sea (for example surface water, sewers, groundwater and infrastructure failure)
Installing sound-insulating materials and structures, such as double-glazed windows, doors, or walls, to block or reduce external or internal noise
Making use of acoustic barriers or screens, such as fences, hedges, or walls, to deflect or attenuate noise from outside or inside the school
Using acoustic baffles or diffusers, such as suspended ceilings, shelves, or furniture, to scatter or redirect sound waves and improve sound distribution
Ensuring mechanical ventilation, heating, and cooling systems are quiet, well-maintained, and are acoustically treated
Using sound amplification or enhancement systems, such as microphones, speakers, or hearing loops, to improve the speech-to-noise ratio and the audibility of speech. These systems can amplify the speaker’s voice and deliver it directly to the listener, or to a hearing aid or cochlear implant.

Given the propensity to affect the quality of communication and learning in classrooms and other spaces, acoustic consideration is an essential aspect of the design of schools.

By applying the principles and practices of acoustics, acoustic engineers play an instrumental role in creating school buildings that provide optimal teaching and learning conditions for teachers and students.

If you have an acoustical related issue and need the services of our Acoustics Consultancy team, please contact us.

References

Equality Act 2010 – https://www.legislation.gov.uk/ukpga/2010/15/part/6

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Hawkins Experts Present at Crawfords MCL Surveyors Technical Forum

Chloe Duggan — Thu, 11 Jun 2026 15:58:46 +0000

Hawkins Built Environment experts recently delivered a presentation at the Crawfords MCL Surveyors Technical Forum, providing attendees with a detailed look at the forensic investigation of property damage claims linked to extreme weather and structural loading.

The session was led by Jamie Paterson, Jack Allison and Simon Bateman, who shared their combined expertise through a series of case studies examining storm-related damage, snow loading, and subsidence.

The presentation explored how forensic engineering principles are applied to determine the root cause of structural failures, with particular emphasis on distinguishing between sudden, insurable events and gradual deterioration. Using real-world examples, they demonstrated how factors such as snow loads, wind forces, water ingress, and pre-existing defects can interact to compromise buildings in complex insurance claims.

Jamie explored cases involving snow loading, highlighting the challenges in assessing claims where data may be limited and conditions vary significantly. He emphasised the importance of comparing observed conditions against design standards and assessing whether structural capacity may have been reduced over time due to maintenance issues or degradation.

Simon presented case studies on storm damage and rainwater ingress, illustrating how detailed investigations, often incorporating historical records, site inspections and aerial imagery, can reveal whether weather events alone were responsible or whether underlying weaknesses in the structure played a key role.

Jack concluded with a subsidence-focused case study, demonstrating how forensic analysis can establish the timing and progression of damage, which is critical when determining policy response. His presentation highlighted the importance of historical evidence and site conditions in distinguishing between ongoing ground movement and newly occurring damage.

A consistent theme throughout the session was that successful claims investigation relies on a thorough understanding of both external forces and the internal structural condition, alongside the ability to interpret multiple sources of evidence. The forum provided an opportunity for surveyors and insurance professionals to gain practical insight into how forensic investigations support decision-making in complex claims.

If you would like one of our experts to investigate a case or present to your organisation, please contact us.

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Frozen Pipes: Common Beliefs Vs Reality

Chloe Duggan — Mon, 08 Jun 2026 15:50:46 +0000

During the winter months, escape-of-water claims often arise following periods of freezing temperatures, leading to significant disruption, damage, and cost. While preventative measures such as pipe insulation and active central heating are widely relied upon, real-world incidents demonstrate that these solutions are not always as effective as assumed. Factors such as installation quality, property occupancy, and system design can all influence whether pipework remains protected or becomes vulnerable to freezing of its contents.

In this webinar, Dr Amir Hajdaei will challenge some of these commonly held assumptions by exploring how and why pipe freezing within pipework systems continues to occur despite the presence of these precautions. He will examine the limitations of typical mitigation measures and highlight the circumstances under which they may fail, and will also present a selection of real case studies, showcasing pipework and fittings that have been damaged or have failed due to freezing conditions.

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Secant Pile Walls & Basement Excavations: What Could Possibly Go Wrong?

Chloe Duggan — Mon, 08 Jun 2026 08:05:43 +0000

Basements are now routine in urban developments – from plant rooms and car parks to premium residential space. Yet “routine” should not be confused with “simple”. Underground works introduce a unique set of construction risks, which, if not properly managed, can lead to significant issues, increased costs and programme delays. When properly executed, these works enable the construction of challenging basements, even on constrained sites and in areas with high groundwater tables.

Many properties now require basement construction. In most cases, this is achieved using embedded retaining walls, especially in places with limited space with each option. Where groundwater is present, an embedded retaining wall type must be chosen that can retain the groundwater. Sheet pile, secant pile or diaphragm walls are feasible options. CIRIA C760 ‘Guidance on embedded retaining wall design’ provides selection guidance across wall types.

Secant pile walls, in particular, are widely used because they provide support in both temporary and permanent conditions and can be adapted to suit challenging sites. They retain ground and groundwater, minimise ground movement and can carry substantial vertical loads.

Basements may be routine, but they are not simple. Poor planning and/or execution can lead to significant technical issues, cost overruns, and programme delays. Due to their frequent use, this article focuses on secant pile walls – their role, what can be expected of them and the common issues associated with their design and construction.

What is a Secant Pile Wall?

A secant pile wall is a continuous wall formed by interlocking bored piles, as shown in Figure 1.

Primary piles, often referred to as female piles, are installed first, and secondary piles, also known as male piles, are drilled so that each one cuts into the adjacent primaries, creating an interlocking line of concrete. Primary piles are typically unreinforced (see Figure 2).

This system of interlocking primary and secondary piles creates a hard/soft or hard/firm secant wall. The difference between the two wall types is the concrete strength in the primary piles. If the secant wall is used as temporary works only, there is no need for durability or strength requirements for the unreinforced pile, and non-structural concrete may be used. Due to advances in rig power and the cost of using secant walls as temporary works only, hard/soft secant walls have become less common compared with hard/firm secant walls where the primary pile often consists of a low-grade structural concrete, such as a C8/10.

However, in very deep excavations and in response to additional structural requirements, it may be necessary to also reinforce the female piles (see Figure 3). This combination then becomes a hard/hard secant wall which uses high grade structural concrete in both primary and secondary piles.

Secant walls can be constructed using various techniques:

The choice of technique depends on the project requirements, especially permissible tolerances, retained height, depth of interlock required and prevailing ground conditions, see Figure 4. Interlock is the length of wall over which the secondary piles cut into the primary piles. This distance is of particular importance for groundwater exclusion.

Achievable tolerances and typical depth of interlock are defined in the ICE Specification for Embedded Retaining Walls (ICE SPERW) in Table B1.4 and partially reproduced below in Table 1. Whilst the verticality of wall and depth of achievable interlock increase from CFA towards RBP, so does the cost, complexity and the timeframe to install the secant wall.

Advantages of Secant Pile Walls

There are numerous reasons why secant pile walls are often the preferred solution for basement construction:

1. Space Efficiency in Constrained Sites

Urban basements are frequently built tight against property boundaries or adjacent structures. This makes secant walls ideal for city-centre projects where every metre counts.

2. Groundwater Management

Secant walls provide an effective horizontal water barrier when installed correctly. This is particularly valuable where high water tables or sensitive neighbouring assets are present. However, they do not necessarily mitigate vertical groundwater flow into the excavation and should be used in conjunction with a groundwater management strategy (CIRIA C750 ‘Groundwater control: design and practice’).

3. Structural Versatility

Secant walls can serve both as temporary excavation support and as part of the permanent basement structure, reducing duplication of work. They can be designed to carry substantial loads, making them suitable for deep basements and complex load cases.

4. Adaptability

Secant pile walls can be constructed using a variety of piling techniques to address a range of retained heights, tolerance requirements and ground conditions. Secant walls can also adapt to accommodate many footprint shapes. This flexibility makes secant walls a practical choice for many UK ground profiles.

Where Things go Wrong

On paper, secant pile walls look like the perfect solution: strong, versatile, and great for tight sites. But in the real world, things do not always go to plan. Here are the most common issues we see and why they matter.

Misalignement

Secant walls depend on the interlock between primary and secondary piles. However, piles (typically secondary piles) can become misaligned for a variety of reasons, see Figure 5.

Some common root causes for misalignment are given below:

> Primary concrete too hard, causing the secondary pile to deviate into ‘softer’ soil. This is often caused by inadequate or untested concrete mix design and is most commonly seen in CFA walls.

> Incorrect sequencing. Sequencing is of particular importance in CFA secant walls. If the sequence is not planned properly, or disrupted due to site changes or plant breakdowns, the concrete in the primary piles may become too hard, resulting in the defect described above.

> Incorrect technique chosen for interlock requirements. Due to the significant increase in costs from CFA to CCFA and RBP, the interlock limits of CFA are frequently pushed. Joints, especially in standard CFA augers, create a degree of flexibility and make it easier for piles to deviate from the vertical. To minimise this risk, having fewer joints in the auger is better.

> Obstructions in the ground, either natural (such as boulders) or man-made (in the form of old foundations or walls etc.), can cause piles to deviate from their intended position and verticality. RBP techniques are best placed to deal with obstructions in the secant wall alignment and should be chosen if obstructions cannot be removed prior to secant wall construction.

Misaligned piles can affect projects in multiple ways. If the interlock between primary and secondary piles is broken, unwanted soil and water can ingress into the excavation, which will require immediate remedial works (typically through resin injection).

Having sufficient interlock is not only important where it can be seen, i.e. above excavation level, but also below this level to guarantee sufficient water cut-off to make the excavation safe and free of running water. Groundwater entering the excavation from the bottom can destabilise the soil and, in extreme cases, cause uplift failures which should be considered in the geotechnical design of the basement (BS EN 1997-3:2025 – Eurocode 7 – Geotechnical design. Geotechnical structures). To avoid these, the design of the basement should be accompanied by a groundwater management strategy (CIRIA C750 ‘Groundwater control: design and practice’).

In severe cases, a misaligned pile (shown in Figure 5) can impact the spatial requirements of the basement, e.g. the position of liner walls. In these cases, either the out-of-position pile or the secondary element will require structural modification, potentially impacting layouts, available space or structural capacity of the secant wall itself.

Water Ingress

For the avoidance of doubt, secant walls are rarely found to be perfectly watertight. Due to the number of joints between primary and secondary piles, secant walls are vulnerable to water ingress. Damp patches and beads of water (individual droplets of water) are to be expected and do not constitute a defect. The size of damp patches, however, should be less than 4m² per patch, or less than 10% of the visible face of the wall (refer to ICE SPERW 3^rd Edition, Clause B1.9.1 for further details). Weeping water, i.e. where the water runs down the face of the wall, is not acceptable.

Water ingress may occur even if there is no visible sign of misaligned piles. An allowance should be made in the construction programme to permit the piling contractor to deal with leaks through resin injection or other sealing methods.

It is also important to understand that secant walls are classified as Type B protection against water ingress (see BS8102:2022, Table 1) and alone cannot provide a performance level better than Grade 1b (no seepage, damp areas from internal and external sources are tolerable) in accordance with BS8102:2022, Table 2.

Protrusions

Protrusions refer to irregularities on the exposed face of a secant wall after excavation, see Figure 8. Instead of a vertical surface, the wall may have protrusions extending beyond the face of the wall into the excavation. Whilst this is not a structural defect, it can have consequences for follow-on trades and potentially the construction programme.

Protrusions frequently occur in

> Loose natural granular soils or soft clay deposits

> Poorly compacted or poorly graded backfill after obstruction removal (often associated with the removal of an old basement).

> Certain ground conditions where over flighting is a risk associated with CFA techniques (refer to FPS Guidance paper ‘CFA Piling: Preventing ground & rig instability through over-flighting’).

Protrusions in soft/loose/insufficiently compacted ground cannot easily be controlled by the piling contractor. The piling contractor is only responsible for the removal of protrusions in excess of 100mm thickness (ICE SPERW 3^rd Edition, Clause B11.4.2). It is therefore important to allow sufficient time in the construction programme to deal with protrusions, although it is structurally permissible to leave protrusions in place unless they interfere with waterproofing or finishing works.

Concrete Defects

Concrete quality is critical for durability and long-term performance of secant pile walls. Defects can occur during placement and often remain unnoticed until later stages. Using a trialled and tested concrete mix design from established concrete suppliers and undertaking concrete performance testing, are effective ways to minimise the risks of defects. How the concrete is handled on site, for example, avoiding changes to concrete properties through the addition of water, and ensuring the timely and appropriate placing of concrete in accordance with the relevant standards, such as BS EN 1536, ICE SPERW, EFFC Tremie Guide is also of vital importance. Inadequate base cleaning or support fluid exchange, poor tremie practice (RBP only) or concrete supply interruptions can also affect the final product.

Some common concrete defects in secant walls include:

> Shadowing/mattressing, refers to situations where concrete does not flow adequately around the reinforcement bars and leaves ‘shadows’. This defect only occurs in rotary piles.

> Inclusions in piles, which are a common problem and are often the result of inadequate concrete workability. They consist of entrapped materials that differ from the specified concrete and can originate from the surrounding ground (soil or groundwater), poorly cemented material from the original segregated concrete, and may also contain drilling fluids (if used during construction). Inclusions occur more frequently in rotary bored piles as the concrete is placed after the installation of the reinforcement cage and must flow around the bars, but can also occur in CFA or CCFA piles when the concrete has lost its workability.

As a result of inclusions, concrete cover becomes inadequate requiring remedial work. If the inclusions are extensive, they may also provide additional pathways for water ingress (though the reduction of interlock) and may require the down-rating of pile/wall capacity.

What to Expect

Many disagreements occur when expectations between parties are not aligned. The points below summarise what can reasonably be expected:

Secant pile walls are not fully watertight

Secant pile walls manage groundwater inflow, but they do not provide completely dry basements. Damp patches or minor seepage are common and should be anticipated. Flowing water or concentrated leaks, however, are unacceptable and usually indicate defects requiring remedial works. Waterproofing should always follow BS 8102:2022 guidance, with allowances for remedial sealing such as resin injection.

Damp spots do not mean defects

Clients often expect a completely dry basement. In reality, even with a well-built secant wall, some moisture may appear. This is normal and should be addressed through the waterproofing strategy, not treated as a defect.

Overbreak is common

Expect some irregularity on the exposed wall face after excavation. Overbreak often occurs in loose granular deposits, soft clays, or poorly compacted backfill from obstruction removal. Whilst it does not present a structural problem, it complicates waterproofing and finishing works. Extra trimming or patching may be needed, which can affect programme and cost.

Straightness varies by technique

Walls formed using rotary bored piling (RBP) tend to achieve better verticality, greater interlock and straighter faces than those installed with CFA methods. However, while these advanced systems deliver superior alignment, they come at a higher cost.

Consequences for Projects & Claims

When secant pile walls do not perform as expected, the impact is rarely minor. Even small defects can significantly affect the programme and budget. The following outcomes are typical:

Remedial Waterproofing

If water ingress occurs, the leaks are usually treated by polyurethane or acrylate gel injection. This treatment generally stops the leak but can be very disruptive. Injection requires specialist contractors, access to the affected areas, and often multiple visits. Blocking one leak often causes others to appear, meaning costs can increase quickly, and programmes become delayed.

Additional Surface Preparation

Whilst overbreak may be more of a cosmetic problem, it can mean that the wall face is not ready for waterproofing straight away. Trimming, patching, or applying thicker coatings adds time and labour. These tasks are rarely in the original programme, so delays are common.

Structural Downgrades

In rare cases, if tolerances or concrete quality fall short, the wall’s structural capacity may need to be reassessed. This can lead to redesigns, additional props, or strengthening measures, all of which add cost and complexity.

Programme Delays and Cost Overruns

Every remedial step, whether sealing leaks or smoothing surfaces, pushes the schedule out. Waterproofing trades cannot start until the wall is prepared, and follow-on activities like slab casting or fit-out are held up. Claims for delay and disruption are common in these scenarios.

Bottom line: Defects, even cosmetic ones, can have significant commercial consequences. Early planning, engagement with relevant specialists, realistic tolerances, robust quality control, and allowances in programmes are the best approach to avoid subsequent issues.

From our experience, it is essential to follow these steps to minimise issues on site or disputes:

> Define the waterproofing performance grade early (BS 8102:2022) and appoint the waterproofing specialist at the concept stage.

> Select the right wall type for depth, deflection limits and groundwater context (CIRIA C760).

> Make allowances for realistic tolerances (ICE SPERW).

>Plan groundwater management: combine secant cut‑off with dewatering where required; design for uplift; protect adjacent assets (CIRIA C750).

Conclusion: Why Early Attention Matters

Secant walls make complex basements possible, but they are not an “install and forget” solution. Misalignment, protrusions, water ingress, and concrete defects are all common issues that can lead to extra work, cost, and programme delays. Most “problem basements” are not the result of a single catastrophic error – they often stem from a series of small, foreseeable mismatches between design assumptions, construction tolerances, and waterproofing expectations. Addressing those early is far cheaper than dealing with issues later. Standards and guidance exist; the key is to use them proactively.

If you are facing secant wall performance questions, planning a deep basement, or navigating a claim, Hawkins can help – from early risk reviews and design due‑diligence to independent failure analysis and expert evidence. We translate complex geotechnical issues into clear advice and defensible conclusions for clients, contractors and insurers.

About the Author

Yvonne Ainsworth is a Chartered Civil Engineer and Principal Associate at Hawkins, with over 25 years’ experience in geotechnical and structural engineering. Her career includes senior roles delivering complex foundation and retaining wall projects, including secant and diaphragm wall construction on major UK infrastructure schemes. Yvonne is widely recognised for her expertise in piling, ground engineering and resolving high-risk technical challenges, with experience directly relevant to the behaviours, risks and performance of secant pile walls discussed in this article. She brings specialist insight into design, construction methodologies, and failure investigation in complex ground conditions.

References

BS 8102:2022 – Protection of below ground structures against water ingress — Code of practice

BS EN 1536:2010 (+A1:2015)- Execution of special geotechnical works – bored piles

BS EN 1997-3:2025 – Eurocode 7 – Geotechnical design. Geotechnical structures

CIRIA C750 – Groundwater control: design and practice, second edition, 2016

CIRIA C760 – Guidance on embedded retaining wall design, 2017

EFFC Guide to Tremie Concrete for Deep Foundations, 3^rd Edition,2024

FPS Guidance Paper ‘CFA Piling: Preventing ground & rig instability through over-flighting’, 2014

ICE Specification for Piling and Embedded Retaining Walls, 3^rd Edition, 2016

The post Secant Pile Walls & Basement Excavations: What Could Possibly Go Wrong? appeared first on Hawkins Forensic Investigation.

Hawkins and ALA Attend Asia-Pacific Claims Convention

Chloe Duggan — Fri, 29 May 2026 14:49:19 +0000

Hawkins was well represented at this year’s Asia-Pacific Claims Convention in Phuket, with colleagues contributing technical expertise, strengthening industry relationships, and highlighting our capabilities across the Asia-Pacific region.

David Reid Rowland, a Mechanical Engineer based in the Hawkins Singapore office, delivered a presentation titled Understanding Escape of Water Incidents. His session provided a comprehensive overview of the causes, impacts, investigation methods, and strategies for the mitigation and prevention of such events.

Key points from David’s presentation included:

> Common causes of water escape incidents: Including failures of hot and cold water systems, HVAC pipework, and sprinkler systems, often linked to installation or workmanship issues, corrosion, material degradation, pressure surges, and manufacturing defects.

> Real-world case insights: Demonstrating how issues such as poorly installed joints, chemical incompatibility (e.g. Chlorinated Polyvinyl Chloride (CPCV) degradation), contamination, and unintended sprinkler activation can lead to significant losses, sometimes months or years after installation.

> Impact of water damage: Highlighting the impact on buildings, Monitoring & Evaluation systems, equipment, and stock, as well as create secondary risks such as electrical faults, corrosion, and contamination, depending on the water source.

> Importance of rapid assessment and forensic investigation: Including contamination identification, determining appropriate remediation (clean, repair, or replace), and minimising business interruption through informed decision-making.

> Prevention and mitigation strategies: Including correct installation practices, routine maintenance, material compatibility checks, leak detection systems, and measures to control pressure surges and flood risks.

David’s presentation emphasised the value of early intervention and proactive risk management in reducing damage, cost, and operational disruption.

Also attending the conference was Shimin Zhuang, a Civil Engineer working across the Singapore and Hong Kong offices. Shimin played an active role at the exhibition, engaging with delegates and discussing Hawkins’ multidisciplinary capabilities and experience across complex engineering investigations.

Hawkins was further supported by Zac Oliver of A.Lamb Associates. Zac, Regional Director of ALA’s newly opened Melbourne office, joined the team in connecting with attendees and exploring collaborative opportunities between Hawkins and ALA.

The conference provided an excellent platform to share knowledge, engage with industry peers, and reinforce Hawkins’ strong presence across the Asia-Pacific region.

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