A major £3.4m Scottish Water project to increase the capacity of Black Esk reservoir has been completed.

The reservoir, which serves drinking water to communities throughout Annandale and Eskdale, has been raised by 2.5 metres. The height of the overflow weir has also been increased using the addition of a 'piano key weir' extension, the first of its kind in the UK. The project design and construction was undertaken for Scottish Water by Black & Veatch.

The capacity of the reservoir has increased by around 40%.

To mark completion of the project local councillors Archie Dryburgh, Denis Male and Craig Peacock were shown the new structure by Project Manager Jim Tudhope, Water Operations Manager Ian Skilling and Community Team Manager Bill Elliot.

Jim Tudhope said: "This project will significantly improve the security of the water supply from the Black Esk Reservoir. This will further enhance our ability to deliver water to customers, such as in the event of prolonged dry weather.

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"We have raised the crest of the dam by 2.5m, using clay that already existsed on site, helping to minimise costs and traffic in and out of the site. The project has also involved raising the existing spillway weir, which sits inside the body of the reservoir and to the casual observer has the appearance of a large plughole.

"To do this we have installed a circular 'piano key' extension to the weir which consists of 24 pieces of cast concrete, each the size of a portacabin. This is believed to be one of the first times such an approach has ever been undertaken anywhere in the world. The weir design adds to the operational efficiency of the reservoir, and also enhanced safety for the construction team.

"Before the project started a team visited France to research these types of weirs and to our knowledge they are always in a straight line and not circular. We have demolished part of the existing structure and recycling the steel and concrete. The concrete will be used as a sub-base for improvements we are making to the Forestry Commission road nearby. The steel will be taken off-site. We have also raised the height of the valve tower and replacing the bridge to the tower, a forestry road diversion, landscaping works and installing new valves."

Black Esk is used to supply drinking water to homes and businesses in communities such as Annan, Lockerbie, Lochmaben, Eastriggs, Gretna, Langholm, Canonbie and on the outskirts of Dumfries.

(IT)