Great floating plug of the Colden...

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Dave Smalley’s investigation of Noah Dale dam starts with a story and an oddity in the landscape, as he explained to Hebden Bridge Local History Society.

The story is of a catastrophic collapse of the neglected dam at the head of Colden Water in the 1930s which carried the core of the dam downstream, writes Sheila Graham.

The oddity is the mound of earth which stands close to the breached dam wall and has been identified as the ‘plug’. But big mounds of earth don’t just float. Dave was determined to find a more convincing explanation.

The dam itself was built between 1805 and 1810 so that water supply could be guaranteed to the spinning mills of the Colden Valley. Dave established that the original dam was well built but shallow, unable to hold enough water to supply all the mills. The owners took an enormous loan of £7000 in 1810 but in 1826 needed to invest in making the dam bigger. This raised the wall using rather shoddy engineering, probably the cause of the dam’s ultimate failure.

The original dam made use of existing landscape features, but diverted the course of the Colden. The odd knoll is not a ‘floating plug’ but just part of a larger mound that was cut through by the navvies to keep the Colden flowing well.

Stories have always suggested that the dam, still decaying a century later, burst because of a serious rain storm – but the rainfall statistics don’t support this theory. It seems the owners decided to dismantle it, probably by collapsing a tunnel.

Dave’s talk was a masterclass in showing how archaeology, geology, engineering, detective work in archives, analysis of photographs and simply tramping through bleak boggy moorland combine to add to our knowledge of the past and bring history to life.

The society’s talks start again in September, info at www.hebdenbridgehistory.org.uk