Wessex Water is pushing ahead with offsite manufacturing with the help of digital technology.
Digital tools used on a water treatment plant upgrade have provided a springboard for Wessex Water to explore the potential of new offsite construction approaches.
Wessex Water principal digital engineer Paul Verner explains that the real push with digital tools began with the water company's £50M project to upgrade the Durleigh Water Treatment Centre in Somerset.
Work at the site near Bridgwater started in 2019 and has now reached the handover stage – but the effects of the approach taken there could be much longer lasting than the three year build.
"We realised the large equipment could be manufactured offsite, brought in and craned into position"
The old water treatment centre had come to the end of its operational life and extensive reconstruction was needed to maintain delivery of drinking water to 44,500 people in the region. In total, 70% of the old water treatment centre has been demolished and recycled, with outdated equipment decommissioned and removed and 30% of structures repurposed and/or refurbished.
The digital delivery processes used from the outset of the project included building information modelling (BIM) in 3D, undertaken by Wessex Water's design consultant Aecom.
"One of the big outputs from the models was the realisation that we could make a lot of the large structures and tanks offsite," Verner explains.
"Because of the accuracy involved in using the 3D scans [of the site], we realised the large equipment could be manufactured offsite, brought in and craned into position."
"The idea is that you don't have to do a bespoke design solution for every problem you encounter"
Items such as tanks and large pipe sections were made in Wessex Water's offsite build facility. Accurate installation was made easier as the team had 3D scanned the existing area and used the data in the scans to ensure the new tanks and pipework would fit before it got to site.
The products were mostly made from stainless steel. A bank of nine tanks, each approximately 12m to 15m tall, was manufactured by a stainless steel specialist at its own factory and brought to site to complete. This approach increased certainty because the items could be made in a controlled factory environment where there is heating, lighting and cover from the elements that is not normally available on a construction site.
It also saved on time, cost and materials, with the 3D model developed from the scans providing improved project information accuracy along with greater certainty about associated costs, delivery timeline and risk management. In addition, offsite building means items can be manufactured in parallel with civil and construction work, which gives a direct saving on construction overheads like plant hire and temporary works costs.
"Overall, there was a realisation that these digital tools could be used effectively from multiple points of view – health and safety, sustainability and speed of build on site," says Verner.
The Durleigh project was used as a proving ground for Wessex's offsite build strategy, encouraging the development of a standard products strategy for other projects.
Standard products
Digital tools have enabled Wessex Water to continue developing these standard products for its facilities.
The products are described in 3D models and in plans, sections and schedules.
These are then shared with teams and partners on the operations side through Autodesk's BIM 360 platform so everyone involved in the project can comment on and understand the product.
"So the idea is that you don't have to do a bespoke design solution for every problem you encounter," Wessex Water strategic digital manager Adam Bear explains.
"If you can have a standard or a collection of standard products that fit together, you can drop a design in that speeds up the design and construction process."
This means less time has to be spent on site and fewer materials are used, contributing to a smaller carbon footprint as part of the delivery process. In addition, the products can be used across a range of projects.
Bear adds: "If we constantly design different solutions to the same problem, our colleagues in operations have to spend a lot of time understanding how to maintain those solutions. But if you have a standard design, the way in which it is maintained is simplified too."
These standard products are then fabricated in the offsite facilities.
Standard processes
Since the beginning at Durleigh, this uptake of digital approaches has continued to gather pace.
"From then we've moved on," Verner says. "Quite a large number of smaller projects – sub £1M – have all gone pretty much straight away onto BIM 360. They've been the teams that have forged ahead on that digital tool.
"In the last few years we've also introduced our own in house design teams and we're pushing on with designing in house, doing models in house and using the approval systems we've set up within BIM 360 and making sure the governance is adhered to."
Wessex Water now has standard document filing structures and approval processes for internal and external designers.
Some of the external designers can also upload their own models and initiate their own reviews for Wessex Water to see.
This reduces emails and increases accuracy of the items that go onto site. GPS coordinates are provided for every corner of every slab so there is no need for teams to set out dimensions with surveying equipment, saving time on site.
In addition, it has become possible to engage with construction and operations teams a lot earlier in the process.
"When we come to do design reviews, we can include ops in that so they can see what's going to be happening on their sites at a much earlier stage and even feed into the design," Verner explains.
"Often there's a tendency for that to lead to some design changes. If we can make their life better and safer as the end user, that's a great thing to do."
Overall, using a common data environment makes it possible for everyone to have access through a computer, tablet or phone.
"During lockdown even though we were physically further apart, we were in some cases working closer together because we could share models in this way," he adds. "It is a more collaborative and democratised way of working."
Different tools for different projects
Along with BIM 360, Wessex Water uses 2D tools, such as AutoCad Electrical. Different projects use different tools at different points depending on their requirements. The use of schematic 2D tools allows BIM 360's graphical models to be linked to a scheduling component.
"A model doesn't have to be 3D geometry," Bear says. "Previously we would have done drawings, then scheduling and then made sure they tied up together.
"Now you can design it once and it's described in both ways – you've got the schematic layouts which are essential for understanding the big picture and the scheduling information which is essential for ordering, purchasing and determining specifics about each individual valve and pump that you need to process."
As a water company which is an owner, operator, designer and contractor, Wessex Water is uniquely placed to implement such solutions.
"We are not only interested in the design - we are looking at the whole life cycle of the assets," Bear says.
"BIM 360 helps us with that and allows design, delivery and operation of the asset to be considered at the outset."
Source: New Civil Engineer
