Behind the bridge: SCN speaks to Queensferry Crossing contractor SES Engineering Services

Colin Walker
Colin Walker

SES Engineering Services (SES) won the mechanical, electrical and plumbing (MEP) package on the new £1.35 billion Queensferry Crossing, which opened to traffic today. The two-year contract saw SES deliver MEP systems for the bridge’s North and South approach sections, the central cable stayed bridge, its three towers and abutment buildings. To mark the opening, Scottish Construction Now asked Scotland business director Colin Walker about the project.

Can you give us an idea of your professional background/experience, outline your specific role on the project and tell us what drew you towards becoming involved in the sector?

I started my career as an apprentice electrician with Crown House and moved to NG Bailey in 1988 and by the time I left in 2010 I was managing director Scotland, responsible for a turnover in excess of £70 million.

I established SES’ Scotland office in 2010 and today our turnover is in excess of £30m. Large, technically complex and unique projects have been of significant interest to SES and none fit better, into this category, than the Queensferry Crossing.

The crossing is SES’ first foray into bridge building, why take on such an ambitious task?

SES saw a clear opportunity to prefabricate the majority of services on the bridge using Prism, its prefabrication and offsite manufacturing facility in York. Ordinarily, the offsite business is primarily aimed at services for buildings and not infrastructure, so although an ambitious project SES believed its experience meant it was best placed to deliver this technically complex and unique project.

Queensferry Crossing from north viewpoint. Image reproduced courtesy of Transport Scotland
Queensferry Crossing from the northern viewpoint

What changes has the business made to manage the unique challenges brought by a project of this scale?

The scale and logistics of the Queensferry Crossing project required a focused approach to overcome the unique challenges we were likely to encounter. From the outset, at tender stage we meticulously planned our safety and logistics management approach, resulting in a plan that is probably the most detailed plan I have ever seen.

For example, we had to plan for our teams to go to work using a boat, so they could access the towers and bridge deck. Working here brought its own challenges from a safety point of view and I am very pleased with how our team has managed these and kept and continue to keep an absolute focus on safety.

The final touches being put to the Queensferry Crossing
The structure spans 1.7 miles (2.7km) making it the longest three-tower, cablestayed bridge in the world

Another first for SES saw the firm open an offsite pre-fabrication facility away from its Yorkshire base for the first time. How crucial was this to the delivery of the project?

As the first MEP services contractor to achieve BRE Accredited BIM Level 2 Certification, SES and Prism provided true digital manufacturing functionality by marrying digital processes to limit waste, with the ability to create lean modules easily installed by engineers working offsite in Scotland.

The case for SES’ first permanent Prism base away from Yorkshire, located in a vacant factory unit on the outskirts of the construction site, was obvious, given the logistical savings allowed by lean module deliveries. Initially manned by a team of Prism staff, the factory was later handed over to an SES team of locally upskilled labour.

SES fitted services and cable trays into ‘flatpack’ steel frames at Prism in York. These were then transported to Scotland where they were assembled at the newly opened onsite Prism facility. Normally the modules would be assembled in York, but by completing the second stage in Scotland, SES significantly cut transport delivery times and costs on the project. We estimate that if we had assembled and transported the modules in York we would have required 60 lorries travelling 24,000 miles as opposed to two lorries travelling 500 miles to deliver the modules.

The final touches being put to the Queensferry Crossing
Laying out all the 23,000 miles of cabling used to support the bridge deck would very nearly stretch around the entire planet

Is it something SES would consider doing again in the future?

Absolutely, the bridge has been and continues to be a fantastic project for us. The experience and knowledge we have gained from a major infrastructure project of this stature is second to none. We fully intend to pursue more opportunities within the sector and hopefully the experience of delivering the bridge will make us stand out from our competition.

How much of a factor was SES’ extensive experience in BIM in winning the tender and how has this been utilised on the project?

SES has made significant investment in BIM and prefabrication which means we are well placed to bid for technically complex M&E projects. Having a clear focus on BIM and prefabrication enabled us to develop a prefabricated services strategy that reduced costs, programme time and the amount of labour hours spent working at height.

BIM also helped with cost predictability and waste reduction, significantly strengthening SES’ business case when tendering for the project. Reducing the amount of work at height was a huge consideration for the bridge team. Our commitment to offsite engineering dramatically reduced the need for working at height.

Queensferry Crossing on deck 23
35,000 tonnes of steel was used in the bridge superstructure

Has the increasing complexity of modern buildings helped ease the transition from SES’ usual projects to what is Scotland’s largest infrastructure investment in a generation?

Our experience in large technically complex projects across the UK has stood us in good stead for the unique challenges the bridge has brought us, so our transition to this project has been more evolutionary as opposed to revolutionary.

What steps are being taken to ensure the same corrosion problems that were uncovered on the Forth Road Bridge don’t affect its replacement?

Corrosion has been a significant and costly issue for the Forth Road Bridge which had no dehumidification system installed when it was built 50 years ago. A critical example of SES’ services installation was the pioneering use of a dehumidification system inside the box girder to reduce moisture and prevent corrosion. SES has installed dehumidification ventilation systems, which ensures the inside of the deck sections are dry and do not cause corrosion over time.

Queensferry Crossing on deck 22
Prior to the completion of the final closure sections on the deck, the balanced cantilevers which extend 322m north and south from the central tower were recorded by Guinness as the longest ever

What specific requirements come with working on such a high profile project? Have you felt public interest change with the delayed opening?

With the project being very much in the public eye it has been absolutely crucial that we maintain our professional approach and live by our company values of integrity, intelligence, performance, teamwork and respect. I am pleased to say that we have done that. The interest in the project has been outstanding with every one of our team being regularly asked how it was progressing by friends and family. To be honest the opening date hasn’t really changed people’s interest; it has always been high and remains high.

Finally, has the Queensferry Crossing whetted the appetite for SES to continue with large scale projects or will the business return to more conventional activities?

Although the Queensferry Crossing is SES’ first foray into bridge building, we have had significant experience of working on large scale, technically complex projects including the bio-containment laboratories for The Pirbright Institute, the scheme to transform Drax Power Station into the UK’s largest single renewable electricity generator, and our current £43m contract on the new £300m Defence and National Rehabilitation Centre (DNRC) at the Stanford Hall estate near Loughborough.

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