End in sight for Glasgow's Katrine Water Project
Six years after planning permission was submitted, Scottish Water's huge Katrine Water Project is nearing completion. And it will supply Glasgow with a state-of-the-art water supply."It is a work indeed which surpasses the greatest of the nine famous aqueducts which fed the city of Rome. And amongst the works of ornament or usefulness for which your city is now distinguished and will hereafter become famous none, I venture to say, will be counted more credible to your wisdom, more worthy of your liberality, or more beneficial in its results than the Loch Katrine Works."
This is what John Frederic Bateman, chief engineer on the Loch Katrine Water supply scheme, said of the project in 1859. That scheme involved the construction of a dam on Loch Katrine, 42km of aqueduct, a similar length of trunk mains, 74km of distribution pipes and the Mugdock storage reservoir at Milngavie, near Glasgow.
Loch Katrine has supplied Glasgow with high-quality drinking water for more than 140 years. Bateman recommended using the loch to the House of Commons after Glasgow suffered a second outbreak of cholera in the late 1840s.
Changes to UK and European water quality standards are the main driver behind the Katrine Water Project (KWP), the largest water treatment scheme in Scottish Water's current £1.8B investment programme and which will provide Greater Glasgow with a state-of-the-art water supply. Bateman's quotation could also apply to this project, now nearing completion six years after planning permission was submitted.
Black & Veatch (B&V) is the main contractor on the project. It had been MJ Gleeson until its acquisition in 2006 by B&V, which comprises linked elements across the Milngavie, Strathblane and Balmore area. Other key players on the project include MWH, Thames Water, EC Harris, ERM and Scottish Water Solutions.
The KWP has entailed constructing a new direct filtration plant to supply Greater Glasgow with 240Ml of drinking water daily; modifying the existing pumping station at Blamore WTW; and providing an extra 160Ml of treated water storage capacity.
Associated work also includes laying 12km of large-diameter mains and building facilities for filter backwashing, washwater recycling and chemical dosing.
Mark Allan, senior contract manager at B&V, is overseeing the project.
Construction of the main treatment works at Milngavie started in March 2004. Allan says several sites were appraised, with cost, environmental impact and technology - gravity or pumps - being the main parameters. About 115-120 options were costed.
A pilot plant was set up at the existing Milngavie works so that water could easily be drawn from from the Craigmaddie and Mugdock reservoirs. The pilot plant, which worked for a year, was designed to treat up to 31m3 of water an hour and could operate 24 hours a day.
The pilot plant processes were scaled-down versions of those that could be used at the new water treatment works (WTW). These were rapid gravity filtration, dissolved air flotation / rapid gravity filtration and immersed membrane filtration. These trials were to establish the effectiveness of the proposed treatment processes through all four seasons in order to select the most appropriate method.
Direct filtration, which has a conditioning phase and a filtration stage, was selected as the most suited to the Loch Katrine water.
Water is drawn from the reservoirs and dosed with lime to get a stable pH and provide the best conditions for the aluminium sulphate and polymer, which are added to maximise flocculation. The coagulated water passes through mechanically mixed flocculation tanks and then flows under gravity to the filtration columns.
The filtration medium is antracite / sand to ensure operational efficiency is maintained. The filter columns are cleaned by upflow backwash twice daily. Allan says that "getting the chemistry right is vital. This is the critical element for us".
After the filtration columns, the water passes through Orthophoshoric Acid - to prevent leading in the pipe. Sodium Hypochlorite is added to disinfect the filtrate, which gets another dose of lime to adjust the pH. Finally, Orthophoshoric Acid is added to remove any lead in the old pipe network from entering the supply.
Allan adds that in supplying the 240Ml/d of drinking water only 6-8l/s is returned to the sewer. "This indicates how clean the water is." He says that all installation is complete. "We now just need to put front-end chemicals through to see how they work."
Plant takeover is scheduled for early September when a variety of tests will be carried out to "iron out any teething problems". The works will officially be opened next May.
Planning permission for the site came with 55 conditions, including movement times for lorries. There were also the logistical challenges of getting equipment in at the right time, and at the right place.
Allan explains: "This is most probably the most intricate [project]. There's a lot of stacking - it looks like a single-storey building but it's all below ground. Storage becomes a premium for moving equipment around."
Building the bulk of the facility underground was in order to make the WTW as unobtrusive as possible to the local community.
In fact, keeping the local community informed throughout the construction process has been important. B&V has held monthly forums, and Allan says there has been positive feedback from the local community. He adds that it is important to be "up front and open with the community".
B&V has won the contract to oversee the Edinburgh Drinking Water Project. This scheme, on a greenfield site, involves building a new WTW at Glencorse, and replacing ageing mains and storage tanks.
But Allan believes that jobs along the scale of the Katrine Water Project and that planned for Edinburgh will become "fewer and fewer" with the next AMP period concentrating on capital maintenance. He feels that the majority of contracts will be around the £10-12M mark.