Tank cleaning – the undercover operation

Scottish Water’s £120M Katrine Water Project aims to protect the supply of drinking water to about 700,000 customers in Glasgow as well as parts of East and West Dunbartonshire, East Renfrewshire, Renfrewshire and South Lanarkshire.

The project entails upgrading the current Loch Katrine water supply scheme through the replacement of the old treatment facility at Milngavie.

Construction of the main works at Milngavie started two years ago and is expected to be completed by December 2007. The work includes:

• Construction of a 240Ml/d direct filtration plant on existing operational land at Barrachan
• Modifications to the existing Balmore Water Treatment Works pumping station to allow the use of 150Ml/d into the Glasgow supply area
• Creating storage capacity for 160Ml of treated water – 80Ml tanks feature at Bankell Farm
• About 12km of large diameter mains being laid

The work has also entailed staff at water engineering firm Panton McLeod cleaning the massive underground service reservoir tank at Milngavie. Panton McLeod is one of a handful in the UK with the expertise to clean the hidden structures that deliver safe, clean water to millions of homes and businesses. Most people never see the infrastructure involved in the water industry, including a nationwide network of subterranean water storage tanks known as service reservoirs.

Commenting on the project and underground tank created at Milngavie, Iain Weir, managing director of Panton McLeod, says: “This is such a landmark engineering and social project for Scotland, we are absolutely thrilled to have played a part in it. There has been a lot of talk about the size and importance of the Katrine Water Project, but it is difficult to get your head round that, until you see it first hand.

“The service reservoir we cleaned is probably the biggest I have ever seen. It had two compartments and each was the size of a football pitch and around 20ft (6m) deep, and each one holds around 40Ml of water.

“The original 26 mile (42km) aqueduct linking Loch Katrine with a water treatment works at Milngavie was considered a feat of Victorian engineering genius. This new scheme is every bit as impressive. Since we are the only Scottish firm of our type, we’d have been devastated if this work had gone elsewhere in the UK.”

Water quality

Service reservoirs form part of the public water supply distribution system. Because of the incredibly strict laws on water quality, such tanks have to be meticulously and expertly cleaned at regular intervals. Cleaning and preparation is even more important when the tanks are being commissioned.

Panton McLeod, based in Melrose, has spent 15 years perfecting highly specialised cleaning methods and developing treatments which thoroughly disinfect the structures without compromising water quality.

Its services are in demand by some of the biggest water companies in the country, including privatised English giants like Severn Trent, Thames, Northumbrian and Yorkshire. On the Katrine project, the firm was also asked to carry out specialist disinfection of several major new pipelines that form part of the project and also have to meet stringent water quality standards.

These pipelines included a 5km stretch between Balmore Water Treatment Works and the new service reservoir (900mm nominal bore) and a 2.2km stretch of pipework (twin 1,100mm/single 1,400mm) between the new service reservoir and the connections into the Glasgow supply network.

Weir says: “We put a rig into the pipelines and had to carefully control the speed it travelled through.

“You have to get it just right because if it is too quick the pipe doesn’t get cleaned properly. Too slow and the chemical dose is too high.We took water quality samples around every 500m to make sure we were bang on and in total it took us ten days. We were delighted with the way the entire project went.

“The good news from our point of view is that everyone at Gleeson’s were also delighted and we hope to get further work from this.”

Already Panton McLeod, which provides a range of specialist services to the water industry, has been commissioned to provide a mini-sub, fitted with high-powered lights and cameras, to carry out a detailed survey of the bed of Craigmaddie reservoir ahead of a major pipe-laying project.

Kelton Bennett is MJ Gleeson’s site agent at the Milngavie Service Reservoir section of the Katrine Water Project. He says: “We have disinfected pipelines ourselves previously, but with the scale of work involved in disinfecting the service reservoir and associated pipework we knew it would need specialists.

“Panton McLeod came highly recommended by Scottish Water and they did everything we asked of them and more, including working through the night several times when it was necessary. They were completely on top of all safety matters and other sensitive issues, particularly when they had to carry out some work inside Balmore WTW, where it is very rare for sub-contractors to have access.

“Overall we were delighted with their performance. They did exactly what they said they would on site, properly and safely and all without a single water quality failure. We could not have asked for anything more. There will be further cleaning and disinfection work to come as part of this project and it will be extremely difficult to see past Panton McLeod to carry it out.”