Golden jubilee for ‘jewel in the crown’ reservoir

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FIFTY years ago this month, HRH Princess Alexandra was in Tynedale to officially open the ‘new’ £5.5m Derwent Reservoir.

The 3.5 mile long dam that can hold up to 11,000 million gallons of water (or 625 million bath fulls), was the culmination of a huge feat of civil engineering that took six years to complete.

And much of the reason for its resounding success was, according to Northumbrian Water’s Kevin Miller, down to the ingenuity of the key engineer on the project, Neil Buchanan.

Indeed, Mr Miller, who is Derwent’s current supervising engineer, describes the scheme as Mr Buchanan’s ‘finest hour’.

“I look after a lot of dams and for me, Derwent Reservoir is the jewel in the crown of Northumbrian Water because it just looks like a natural lake,” he says.

The dam’s designers certainly took advantage of the local topography and the water is surrounded by rolling hills and farmland so that visitors could easily believe it had always been a feature of the landscape.

But it didn’t happen without some imaginative thinking.

The major obstacle for the engineers was the presence of two aquifers (massive natural underground water stores) where they had planned to build the ‘seal’ of the dam.

The reservoir was formed by an earth dam across the River Derwent, a tributary of the River Tyne, and it forms the county boundary between Northumberland and County Durham.

“The options were to pump out the water – an expensive job, using large amounts of electricity – or to use freezing techniques to freeze the water around the excavations thus allowing work to proceed in the dry,” said Mr Miller.

“But Mr Buchanan’s idea was to make the seal upstream, which was very unique.”

Also, rather than importing materials from ‘borrow pits’ to build the dam wall – with all the transport costs that would have entailed – they used the material they excavated from the basin to construct it.

These techniques went into an important report called ‘The Ruffle, Rowe and Buchanan’ paper which became a must-read reference for all engineers.

“It’s used all over the world as a benchmark of how to overcome obstacles such as those encountered at Derwent,” said Mr Miller.

The dam was a joint scheme between Durham Water Board and Sunderland and South Shields Water Company and today it is cared for by Northumbrian Water.

It continues to supply up to 140 million litres of drinking water every day to households in Durham, Sunderland and South Tyneside. Water from the reservoir flows through 2.2 miles of pipeline to a treatment works at Mosswood and from there, travels 27 miles to people’s taps.

The dam is not only a valuable water source however. As David Hall, Northumbrian Water’s head of leisure, strategy and transformation, points out: “It’s not just a source of water for us, it’s a fantastic asset in a beautiful location that provides so much for the local area.

“The recent ‘Tour of the Reservoir’ cycle event (organised by Tyne Valley Cycling Club) brought more people than ever to the reservoir and provided a spectacular backdrop for the races.

“There is a popular sailing club based there too and it’s also home to one of our premier, and most popular, fisheries with lots of bank space and the chance to catch trout weighing up to 15lbs.

“It’s located in the North Pennine’s Area of Outstanding Natural Beauty (AONB) and is home to a fantastic array of wildlife.

“It’s an amazing place and you can often see soaring buzzards, red kites and fishing ospreys as well as red squirrels, rabbits, stoats and weasels there.

“We’re immensely proud of it and we wish this well-loved landmark of the North-East a very happy 50th birthday!”

To mark the reservoir’s anniversary last Tuesday, Mr Buchanan, who went on to work on Kielder Dam during the 70s, was presented with two framed letters from HRH Princess Alexandra and the reservoir’s visitors’ book, signed by the princess and Mr Buchanan at the opening, before he acted as her official guide.

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