Southern Water detected water quality issues at one of their Water Supply Works in Hampshire on 10 November 2019, which threatened to impact the supply of water to 300,000 customers in the county. Within 24 hours, Southern Water’s Emergency Recovery Team had formulated a plan to install a temporary ultraviolet (UV) disinfection system on site and assured the DWI that it would be operational in early January 2020. With short delivery times for UV equipment, winter working conditions and Christmas holidays, this was going to be a tall order.
On 14 November they awarded the contract to Trant Engineering. “Trant were already on site, and we knew they would be able to understand the challenge and rise to it”, says John Evans, Southern Water’s Head of Project Delivery. “Aware of the criticality of fast tracking, they assigned one of their Directors to head up the contract.” Trant teamed with SNCL Atkins as design consultants. Key to completing a fast-track project is assembling and motivating a team of Client, designers and suppliers. Ashton Dewey, Trant’s Client Manager, takes up the story: “The next day we had our first weekly meeting with Southern Water’s Operations and Engineering teams, our in-house engineers, SNCL Atkins and the key supply chain. Due to the geographical spread quite a few people joined virtually and this continued throughout the project.”
Intercepting and Diverting the Water Supply
Together they formulated a plan to intercept the existing treated water delivery main and divert the water through a new UV plant and then return it to the delivery main. The works would be based around Design for Manufacture and Assembly (DfMA) modules fabricated off site while the construction team was laying the foundations. These modules included fully fitted sample kiosks, electrical panels with SCADA and telemetry links and pipework for the UV units. All would be tested prior to delivery.
To ensure that the units would fit together on site, the team prepared a 3D BIM model which was also used for the planning application. With the plan made, all that was required was the execution. “We had to think outside the box,” says Ashton Dewey, “so that we could design, plan and construct as we went along.”
While Trant’s construction team started to lay down the concrete, the process engineers agreed a design envelope for the UV units, the longest delivery equipment. It was then a question of procuring the UV units, and Xylem were able to offer a short delivery. This meant that the pipework design could be completed and purchase orders placed. The piping designers worked out a sequence that would allow the diversion through the UV system and return to the delivery mains to be completed in a single eight-hour shutdown using hot tapping. Specialist sub-contractor, Pipeline Services (UK), supplied a pre-fabricated double tee with a spectacle blind to allow commissioning.
As the pipework was being installed ready to accept the UV units, a modular steel frame building with a retractable inflatable roof was being erected around it. In the meantime, Trant’s internal Automation Control Technology team were developing a functional design specification, writing software and building the control panels to be ready for factory acceptance testing prior to delivery.
The BIM Model was continuously updated as design changes were made to progress the project and it also allowed rapid safety inductions of the site team, which peaked at over eighty. They worked 24/7 except for Christmas Day and New Year’s Day to compete the project on schedule in January 2020. The temporary emergency solution envisaged by Southern Water’s Emergency Recovery Team was designed to be easily modified to become a permanent installation.
The DWI visited the site just five weeks after the project kick-off and were reassured to find that the UV reactors were already on site, pipework installation was well advanced and the building partially erected. The last word goes to John Evans: “A project like this would normally take over a year, but we completed it in only eight weeks. It’s the power of the team coming together that makes that possible.”