It’s been a dramatic week for Thames Water, but behind the scenes, work to replace ageing infrastructure continues. In November, the troubled water giant is expected to complete the replacement of almost 14km of water pipeline to improve customer supply of water to Swindon and surrounding areas and benefit local rivers.
Ironically, that wouldn’t be the case had the company not questioned the need to conduct an Environmental Impact Assessment (EIA) for the project.
“The EIA could easily have added another year to the programme [the Faringdon to Blunsdon Trunk Main Phase Two] before we put a shovel in the ground,” explains Jonathan Wickens, a senior project manager on the Thames Water capital delivery team. Instead, the team successfully challenged the secretary of state, obviating the need for a full EIA and speeding things up. “Because we were employing construction techniques that weren’t massively out of the ordinary and we had done before, including using an experienced contractor, we avoided the need to do a full environmental assessment.”
(Despite the challenge, Thames Water was obligated to carry out environmental and archaeological mitigation along the route of the new pipeline; archaeologists from Wessex Archaeology, working in advance of construction, uncovered the remains of a crouched burial.)
Prone to expensive leaks
Thames Water designates the Faringdon to Blunsdon link, which transfers water from Oxford’s Farmoor Water Treatment Works, as ‘high consequence’. The old 900mm diameter glass reinforced plastic (GRP) pipeline, completed in 2001, is prone to bursts, inundating local land with water and necessitating expensive repairs. Because of the faulty nature of the old pipe, water runs through it at a lower than desirable pressure and temporary abstractions are necessary to maintain supply.
“To minimise risk, we are completing each phase of the new pipeline and then decommissioning the old section to remove the burst risk,” explains Wickens. “Removing the risk along these three-to-four-kilometre sections is a big help to landowners. In the autumn we will commission the whole pipeline.” Effective engagement with the local community by contractor Kier Infrastructure and Overseas and civil engineering subcontractor CPC Civils has been important. “Kier and CPC speak to landowners on the route every day. It’s important to build up relationships because things don’t always go as planned and some of these areas get very wet.
“We’ve had bursts while we have been working that have washed haul roads away and filled up excavations.” Not only will the works boost resilience of supply, but they will also mean that several temporary abstraction licenses are dispensed with.
The investment in the pipeline is for the long-term, with capacity intended to accommodate increases in population. To ensure asset design life, steel pipework was maximised for the critical tunnel sections. Pipe wall thickness was specified at 10mm, greater than Thames Water’s 6mm standard. Based on the pH levels of the water in the pipe, this means a far superior asset design life of more than a century is theoretically achievable.
Wickens says: “We are putting in materials such as stainless steel that will last a lot longer than what was there before. The sizing has also been taken into consideration, because there is lots of development going on in Swindon, and we want the pipeline to do the job for many years to come.” The existing pipeline is also left in situ as it is decommissioned, with allowances made to ensure it could be slip lined in the future for resilience.
The project design work was done in AMP6 and one particularly high-risk section of existing GRP pipe replaced then. Wickens picked up the project in AMP7. Was there anything he would have done differently? “The contractor was appointed very early on, and then the EIA reared its head,” he says. “With projects now we’re trying to get the impact assessment and planning permission done before we award to a contractor, so we don’t end up with them standing around. We try and iron out all the potential risks.
“Having said that, it’s also important to get contractor input through early contractor involvement,” Wickens points out.
“That allows them to make suggestions about how we can do things better at the beginning. It means once we get into contract, while it may not be plain sailing, it is a much smoother ride through the construction phase.
“Fingers crossed there are less issues when we get out to site,” he concludes.
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