Dinorwic quarry

Walter Warwick Vivian, manager of Dinorwic, in 1896

The Dinorwic quarry, showing the major inclines, mills, levels and tramways, along with the Padarn Railway and Dinorwic Railway

The slate vein at Dinorwic is nearly vertical and lies at or near the surface of the mountain, allowing it to be worked in a series of stepped galleries . This is however not quite how the quarry developed.

The first quarrying was spread across several sites: Adelaide, Allt Ddu, Braich, Bryn Glas, Bryn Llys, Chwarel Fawr, Ellis, Garrett, Harriet, Matilda, Morgan's, Raven Rock, Sofia, Turner, Victoria and Wellington.[3] This was a situation that lasted for many years, certainly until the mid-1830s.

The 1824 railway brought transport problems. Produce from the upper quarries was not a problem, but Wellington, Ellis, Turner, Harriet and Victoria quarries were all below the level of the railway. This was a problem solved in the 1840s when the lake level railway was built, and the quarry as we know it began to take shape.

Adelaide quarry became a part of Allt Ddu, and Chwarel Fawr and Chwarel Goch became linked to it too. In the 'Great New Quarry' Raven Rock and Garret Quarries became one massive quarry, operating as an open hillside gallery quarry, with the lowest two levels being accessed by tunnels. Harriet, Morgans and Sofia quarry are all still identifiable as separate pits today, whilst Braich quarry became a large working of three contiguous smaller pits. Below this, The galleries of Victoria and Wellington were joined along the hillside, and continued downwards in two separate main workings: Wellington and Hafod Owen. Each was eventually to contain several small sinks too, some below lake level. The current form of the quarry is little different from that of the time of the Great War, save for enlarging of the actual quarry faces, and deepening of the sinks. Certainly all the main inclines were in place, very little was altered until closure.[4]

The nearby Marchlyn quarry was opened in the 1930s to provide access to the main slate vein higher up the mountain.

The quarry closed in July 1969, the result of industry decline and difficult slate removal.[2] During the 1950s/60s extraction had become difficult, because after 170 years of extraction many of the unsystematically dumped tips were beginning to slide into some of the major pit workings, and after an enormous fall in the Garret area of the quarry in 1966, production had ceased almost permanently. It was however decided that some final work could be done by clearing some of the waste from the Garret fall. This involved making an access road for more modern quarry vehicles across some of the terraces, to the rock fall. This amount of slate won by this method was small and all production stopped by 1969.

At the Receiver's instruction a public auction was arranged, intended to pay off some of the quarry's debts. The auctions were held on 12 and 13 December 1969. The auctioneer's national advertisement (in The Guardian 29 November 1969), the event was described as "An auction sale of machine tools and stocks, four Hunslet locos, and engine and boat fittings". The locomotives referred to, lots 613–616, were "Dolbadarn", "Red Damsel", "Wild Aster" and "Irish Mail". Before the bidding started, it was announced that Gwynedd County Council had placed a Preservation Order on the Gilfach Ddu workshops, and many items within it.

The first use of railways at the quarry came around 1800 when the first internal tramways were in use. These first lines were worked using horse- and hand- power. For the next seventy years the tramway system grew until it reached the point where more powerful traction was required. The first steam locomotives used were small vertical boilered locos supplied by De Winton's of Caernarfon. In 1870 the first locomotive supplied by the Hunslet Engine Company arrived at the quarry, and the majority of the locomotives that worked at Dinorwic were eventually supplied by Hunslet.[2]

Between 1935 and 1949 the Quarry acquired 22 light internal combustion rail tractors for use on the levels. Half of these were new, the other half second-hand. Their survival rate did not match those of the steam locomotives, and when the quarry closed in 1969 only three still survived.

Although a nominal two-foot gauge, the actual gauge between the rails at Dinorwic was 1 ft 10 ³⁄₄ in (578 mm)[5] in common with its neighbour Penrhyn, but fractionally narrower than the public lines of the Ffestiniog Railway or North Wales Narrow Gauge Railway which were 1 ft 11 ¹⁄₂ in (597 mm).

Louisa Hunslet works number 195 of 1877

Early steam locomotives used by the quarry, and built by De Winton & Co. But from 1870 the quarry acquired most of its locomotives new from the Hunslet Engine Company of Leeds. These were purpose built, initially using a series of Hunslet general/unclassified designs, but after 1886 these fell into one of three purpose built classes:

• Alice
• Port: larger and designed primarily to work at Port Dinorwic, although Michael never did.
• Tram or Mills: worked on marshalling duties on the Padarn–Peris Tram Line, which linked the quarry mills to the Padarn Railway for transportation to Port Dinorwic.

The quarries are now also used as an adventure rock climbing and scuba diving venue. The Blue Peris Mountain Centre, operated by Bedford Borough Council and Central Bedfordshire Council, conducts various outdoor activities at the quarries.

The Vivian quarry section has both climbing and diving sections. The diving experience has normally good visibility, with depths ranging from 6 metres (20 ft) to 18 metres (59 ft), a platform at 6 metres (20 ft), plus flooded buildings, boats, a van and a gnome garden.