Report - - Dorothea Slate Quarry, Wales, June 2011 | Industrial Sites | 28DaysLater.co.uk

Report - Dorothea Slate Quarry, Wales, June 2011


Conquistador d'Wolverton
28DL Full Member
The Explore

My girlfriend and I were enjoying a relaxing holiday in North Wales, when I suggested that we go for a walk around a ‘lake’ in the Nantlle Valley, knowing only too well that the area was formerly the home of extensive quarrying. Furthermore I’d heard rumors of the existence of a moth-balled Cornish beam engine, hidden somewhere amongst this forlorn monument to the Welsh mining industry. The challenge to locate it has commenced and the game was afoot.

gf: at last a nice country walk that doesn't involve climbing fences!

me: You're not wron..... oh what do we have here? Appears be an old abandoned quarry, this isn't on the map!

gf: hmmmm

My attempts to lure the lady into an explore with the promise of industrial ruins and the wonders of a couple of fine examples of Lancashire boilers did not pay off, however she kindly waited for me as I set about the precarious charade of entering the engine house.
Sadly I didn’t have my tripod, so I had to make best use of the internal fixtures and fittings, compromising the variety of photographs I would like to have taken.

I have a huge fondness for the texture of slate, and the north Welsh landscape. Despite the scale of the former industry, I’m amazed at how well these buildings fit into their landscape, seemingly having been carved out of the grounded and molded into a form.


Across the north west corner of Wales a band of Cambrian slate was formed about 500 million years ago, this ‘compacted mud’ has been extensively mined over the past 200 years, and Wales was once home to some of the World’s largest slate quarries. Dorothea slate quarry in the Nantlle Valley was one of the deeper quarries, and hence required the removal of huge volumes of water at enormous cost. When compared to Dinorwic, Dorothea was a far more expressive affair. Furthermore all the waste rock had to be removed too, whereas at Dinorwic it was far easier to dispose of it straight after blasting. This removal of waste rock was an added impunity to time and efficiency. The first quarry in the Nantlle valley was at Cilgwyn in the fourteenth century, and up until the industrial revolution the valley was home to many small quarries dotted in the hill sides.
Dorothea opened in 1820 and grew from a series of smaller older workings, and over the ensuing decades grew into the large flooded quarry seen today. By the 1840’s the quarry was producing 5,000 tonnes per annum, rising to 17,000 tonnes by the 1870s. However as the quarry deepened the issue of removing the water became more taxing, until a flood in 1884 resulted in a number of fatalities. Remedial steps were taken by diverting the nearby river, however these were only a temporary fix so in 1904 work began on a Cornish beam engine in order to remove more water.

The beam engine was built by Holman Brothers, and was the last but two such engine ever to be built! It is also believed to be the newest Cornish beam engine in existence. The engine was designed to pump 10 gallons per second from a depth of 500ft. The engine had a glorious 45years of service, but was eventually replaced by a 60Hp electric pump in 1951. The engine is Grade II listed, but there are no plans to restore it in the foreseeable future.

The quarry was also home to a number of steam powered aerial ropeways, designed to remove slate more quickly from the deep quarry. Almost no trace of these structures remain. The Quarry finally closed in 1970, outliving the mighty Dinorwic, despite it’s more complex situation.














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