Why delays and disruption were worth it
Published on: 12 Aug 2015
Disruptive, chaotic and noisy. That was pretty much the verdict of Downend residents and traders whilst Bristol Water set about digging up local roads, taking seemingly forever. Now that the multi-million pound scheme is near completion, Downend Voice catches up with one of the leading project engineers to find out the reasons behind delays in the area and why the project will take the city into the 21st century
WE moaned about traffic hold ups and noise but one thing is certain - we’d be complaining even more if we turned on our taps and were greeted by brown water.
Thankfully, that’s no longer likely after a £22 million project by Bristol Water to renovate almost 60km of pipe which carries water around the city from reservoirs and treatment works.
The project has been extensive and time consuming with unexpected delays cropping up, largely because until engineers dug down they had little idea what would greet them. They certainly hadn’t banked on the pipe which runs through Downend to have been located three metres below the ground - two metres lower than most other pipes in the city.
The works from Kingswood to Downend formed part of the project, the others being from Knowle to Clifton; from Tormarton to Shipton Moyne; from Bedminster to Castle Park and from Barrow Gurney to Backwell.
The aim of the scheme - one of the largest ever investments in the area’s water supply - was to provide better quality water to homes and businesses throughout the city and give Bristol a water supply network fitting of the 21st century.
Iron pipes have been replaced with large blue plastic ones which, unlike the old Victorian ones, won’t corrode.
“Some of the pipes in the city have been there for up to160 years and had degraded,” explains Bristol Water project engineer Stephen Boyle.
“There were big developments in Victorian times in terms of installing water infrastructure so we compared to places like London, which also has an older network.
“The pipes we were working on in Downend weren’t as old as that, more like 50 years old, but they had been identified as needing renovation as well.”
The project which passed through the Downend area ran from Kingswood to Filton, with the section of pipe from Kingswood to Downend being almost 3km long.
“We’ve been working on that section since last year,” said Stephen.
“The project is now completed but people may still see teams on site doing some tidy up jobs but the majority of the work is now all done and the new pipe installed.”
Engineers used a process - called sliplining - where new pipe is inserted into the old pipe.
“The scheme in the Downend area has been quite challenging,” said Stephen.
“Most of the time we find pipes are laid at a depth of a metre or so below the road surface. In Downend we found the pipe to be up to three metres deep in some places. That made it quite difficult for the teams to dig down and access the pipe. That extra two metres does make it a lot more difficult. It meant we needed longer excavations, it took longer to get down to the pipe and workers needed more substantial reinforcements to keep the trench open and to keep the ground stable around it.
“It was a much bigger task and I think that was a surprise to us. Unfortunately it meant it did extend the project and we thank everybody for their patience while this work was underway and apologise for any inconvenience caused.”
So why was the pipe laid so deep?
“We don’t know exactly,” said Stephen.
“Because it was laid in around the 1960s, they probably tried to put it below everything else like existing sewers, electricity and telephone cables so everything could be kept in service while they installed it. Some of the older pipes were probably the first thing to go underground so everything else would have gone in around them.”
It was such a feat of engineering that at no time were any households without a water supply.
“This is a really important piece of infrastructure for the area because it brings water into Downend and districts from Kingswood,” Stephen said.
“While we were working we had to find other ways of getting water to people, either by taking the pipe out in smaller sections or by bringing water in from elsewhere temporarily.”
And has all that disruption and noise been worth it?
“When the old pipes were degrading internally there was a risk of people receiving sediment or water which was discoloured. This project removes that risk. It’s a water quality project so that people will continue to receive high quality water.
“We also now have a more resilient network to take us into the future.”