Learn how we have transformed critical water infrastructure in Somerset through innovative engineering, nature-based solutions and digital delivery.
Situated in Bridgwater, Somerset, the Durleigh Water Treatment Centre (WTC) is Wessex Water’s second-largest surface water treatment works.
A key part of the region’s water network, the centre treats up to 30 megalitres a day, providing clean drinking water to 44,500 residents. However, after decades of use, much of the facility had outgrown its design capacity, making it difficult to keep pace with modern demand.
To address this, Wessex Water embarked on a £50 million upgrade, in which we played a pivotal role as lead designer. Applying our multidisciplinary expertise in water engineering, digital delivery and sustainability, we helped deliver this ambitious, multi-faceted project at the scale and pace required.
The upgrade involved far more than just replacing outdated systems—it was about rethinking the entire facility to integrate nature-positive approaches and improve outcomes for both people and planet.
From outdated infrastructure to a cutting-edge facility
The Durleigh WTC sources its water from the Durleigh Reservoir, which has highly variable water quality and is often rich in nutrients, silt and sediment. In addition, seasonal challenges such as algal blooms in summer and cloudiness in winter make consistent, year-round treatment difficult.
Over the past 20 years, the raw water quality deteriorated while key equipment became outdated and inefficient, driving up operational costs.
Part of our role therefore involved designing a multi-stage treatment process capable of managing these complex water conditions while reliably delivering the highest quality drinking water.
Overcoming challenges through collaboration and digital tools
Collaboration was key to this project’s success. By co-locating on-site with Wessex Water, we fostered a ‘One Team’ culture that streamlined decision-making, accelerated project approvals and enabled us to overcome complex challenges.
One such challenge was that the upgrade involved both new construction and refurbishments. As a result, we had to ensure the new equipment – including several large structures and tanks – integrated seamlessly with the existing infrastructure.
Using 3D modelling – integrated with data from ground-penetrating radar, drone surveys and laser scans – we could precisely design new equipment to fit within existing plant configurations.
Aligned with BIM Level 2 principles
The project was delivered to the principles of BIM Level 2, which for some of the client’s team was a new delivery method. Our digital specialists played a central role in streamlining design, construction, stakeholder collaboration and running a series of training drop-in sessions.
One of the standout innovations was the creation of the “igloo” virtual reality (VR) environment. This immersive 3D space allowed stakeholders to “walk through” a digital version of the treatment centre before construction, helping teams identify design issues, assess health and safety risks and improve plant operability.
Additionally, 4D construction sequencing was used to link the 3D model with the construction timeline, providing a clear, time-based visualisation of the build process. This significantly improved stakeholder engagement and site management, enhancing both safety and efficiency.
Enhancing resilience to flooding
Given its location downstream of the Durleigh Reservoir – with the Durleigh Brook flowing through its midst – the site is prone to flooding. This necessitated a robust design to mitigate flood risk and strengthen resilience.
We conducted in-depth flood risk assessments (FRAs) to get a better understanding of how the site responds to flooding, which fed into our final designs.
Plus, by modelling various scenarios from storm events to potential brook blockages, our engineers were able to adapt their designs accordingly. For example, using advanced modelling, we demonstrated that flood risk could be managed without the need for large storm storage systems – simplifying the project and reducing costs.
Reducing onsite construction waste by 20 per cent, cutting £1.1 million in costs
Sustainability was a key consideration of this upgrade. We used off-site manufacturing and selected stainless steel instead of concrete for tanks and structures. This decision not only reduced the project’s carbon footprint but also shortened the project duration by 20 per cent and saved £1.1 million in costs, as well as reducing construction waste on site by up to 20 per cent.
The success of this off-site build approach was so significant that Wessex Water established a dedicated Off-Site Build department to apply these methods to future projects, driving faster and more sustainable delivery across the organisation.
Boosting biodiversity through nature-based solutions
As well as modernising the facility, this scheme involved constructing two wetlands to the west of the WTC. These new habitats are significantly improving water quality by naturally filtering raw water from the reservoir before it enters the treatment process.
Already, they have resulted in a near-75 per cent reduction in the amount of ammonia present in water, while phosphorus and sediments have dropped by around a third.
Plus, by reconnecting the surrounding land and river to its floodplain and restoring cultivated areas to their natural state, biodiversity has increased by between 55 and 76 per cent, according to the Natural England Biodiversity Metric.
Over time, these wetlands will become a resource for public access, further enriching the local ecosystem as the site continues to develop.
Setting a new standard for the wider UK water industry
We’re proud of our contribution to the Durleigh WTC upgrade, which was awarded the IChemE Global Water Award for optimal operation.
Environmental best practice was a key component to the project, earning it two Green Apple Environment Awards in the Habitat & Diversity and Water Management categories.
Thanks to the improved raw water quality and optimised treatment processes, energy usage on site has been reduced by up to 20 per cent – a testament to the scheme’s success.
Now complete, the revamped WTC is not only ensuring a reliable, high-quality water supply for the local community but also serves as a model for future water projects – showcasing how cutting-edge digital tools and nature-based solutions can work together to transform critical infrastructure.