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East meets West

ENGINEERING WATER Water transfer

Scotland's largest water supply improvement scheme takes a step nearer reality this month courtesy of a rare water transfer deal.

Novel water sharing agreements, just finalised between neighbouring Scottish water authorities, are crucial to the success of an environmentally sensitive plan to upgrade one of Scotland's oldest yet most important water treatment schemes supplying most of Glasgow.

Planning approval will be sought later this month for a new £98M treatment plant for West of Scotland Water's 142 year old Loch Katrine water scheme, which feeds up to 400Ml of drinking water every day from the Trossachs loch into the heart of the city. But the upgrade works will be sited close to the existing treatment plant at Milngavie, 8km north of the Glasgow city centre, and in the middle of what is now an attractive landscaped park, jealously guarded by its surrounding stockbroker belt commuters.

That these plans are expected to be approved is due not only to the client's public consultation machinery but also its innovative water share deal with adjacent authority, East of Scotland Water.

Large quantities of raw water from Loch Katrine, destined originally for the new plant, will instead be diverted to a nearby West of Scotland works at Balmore. Here it will be treated and some of the water returned down route of the Milngavie plant to feed directly into Glasgow.

The result is a 30% smaller plant at Milngavie's sensitive location, making it environmentally acceptable, more cost effective and perfectly placed for water engineers. In return, East of Scotland Water keeps some of the diverted water, supplied much more cheaply by gravity than current pumped sources from Loch Lomond.

'We would not have been allowed to build a larger plant at Milngavie and, without this deal, it would have been much more difficult to find a suitable site' says West of Scotland Water's deputy project manager Tony Martin.

'We now not only have the best overall location but the share deal saves us around £10M in total scheme costs.'

The environmental challenges stem, ironically, from the pioneering ingenuity of the original scheme's Victorian engineer John Bateman. His 1850s plan to feed some of Scotland's cleanest water from Loch Katrine along a 40km bridge and tunnel aqueduct into the heart of Glasgow saved more lives than probably any other single act that century.

This clean water replaced supplies from the city's scattered collection of local wells and the street selling of water at 'a halfpenny a stoup'. But, more importantly, it stemmed and nearly eradicated the then rampant outbreaks of cholera that had killed thousands of Glaswegians over the previous decade.

So prestigious was the scheme that Queen Victoria herself opened the reservoir and basic screening works at Milngavie; the local council promptly and lavishly landscaped the area for public use and its successor authorities slapped preservation orders on the lot.

In September last year - triggered by a European Union drinking water directive ordering that, by December 2005, even Loch Katrine water must be cleaner - contractor Gleeson was awarded a five year design and build contract for the new treatment plant. But first a site had to be found.

A just completed, year long, £2M environmental study by a 40 strong team from the client and Gleeson, plus civils consultant Montgomery Watson and process engineering advisor Thames Water, has analysed 190 permutations for the new plant, and its two water storage reservoirs, to be sited on one or more of 17 possible green belt sites.

Challenging virtually all possibilities were some two dozen environmental or physical restraints ranging from ancient woodland and nature reserves to gas pipes and the Roman's Antonine Wall.

Then, in the middle of the study, came the share deal. Just 6km east of Milngavie lies East of Scotland Water's 1960s Balmore plant. This treats water pumped via pipeline from Loch Lomond, also north of Glasgow, but destined for Scotland's east coast towns.

The Loch Lomond pipeline, and Loch Katrine's much cheaper gravity fed aqueduct supplies, cross each other. Why not, said the water companies, link them via a short connection and divert up to 280Ml/day of cheaper Katrine water to be treated at Balmore which has spare capacity ?

Around 150Ml/day of this treated water will be returned via a new 800m long pipeline to intersect the Glasgow supply downline of Milngavie. In return, East of Scotland Water will keep surplus water, so reducing its need for expensive Loch Lomond supplies.

This agreement has reduced the planned new plant from an original 390Ml/day capacity to 240Ml/day, leaving the buildings a third smaller.

The new design tipped the complex cost benefit and environmental analysis in favour of a secluded woodland site within Milngavie's own parkland.

'It is the cheapest and best solution where everyone wins, but was by no means the obvious one until we had completed the studies.' recalls Gleeson business manager Mike Barcroft. 'It was essential to start with a blank sheet of paper so we can now justify our choice.'

The only losers could be company accountants. With Loch Lomond supplies to Balmore varying depending on demand and availability, the cost equation determining which authority should recompense the other, would have demanded an annual exercise. But Scotland's planned water authority merger from three to one next year, removing all water boundaries, also removes the need for such cost balancing.

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