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24-737: The Sieberstollen is an adit (German: Wasserlösungsstollen ) for water drainage in Sankt Andreasberg , in the Harz mountains . It was created during mining in the Upper Harz and named after the river Sieber into which it discharges its water. The opening position is in the Sieber Valley. The first 11.7 km of the 13.1 km adit forms part of the Upper Harz Water Regale and has been declared UNESCO World Heritage Site in 2010. In

48-571: A branch tunnel accessed the Old Milwr vein. In 1908 driving stopped 2 miles from the portal at Caeau Mine, the limit of the company's mineral rights, at which time the tunnel was draining some 1.7 million gallons of water per day through the drainage channel cut in its floor. Objections to further work had been raised in Parliament and by residents of Holywell , who feared that the proposed drainage would affect their water supply, and particularly that of

72-458: A mine : in simple terms, cool air will enter through an adit, be warmed by the higher temperature underground and will naturally exhaust from vertical shafts, some of which are sunk specifically for this purpose. Most adits are designed to slope slightly upwards from the entrance so that water will flow freely out of the mine. Mines that have adits can be at least partly drained of water by gravity alone or power-assisted gravity. The depth to which

96-514: A mine can be drained by gravity alone is defined by the deepest open adit which is known as the "drainage adit". The term mine drainage tunnel is also common, at least in the United States. Workings above this level (known as "above adit") will remain unflooded as long as the adit does not become blocked. All mine workings below both the drainage adit ("below adit") and the water table will flood unless mechanical means are used for drainage. Until

120-630: Is about ten miles (16 km) long. Other examples are the Great County Adit in Cornwall, a 40-mile (64 km)-long network of adits that used to drain the whole Gwennap mining area, and the 3.9 miles (6.3 km) Sutro Tunnel at the Comstock Lode in Virginia City , Nevada . A side benefit of driving such extensive adits is that previously unknown ore-bodies can be discovered, helping finance

144-415: Is required to transport miners and heavy equipment into and out of the mine. It is also much easier to bring ore or coal out of the mine. Horizontal travel by means of narrow gauge tramway or cable car is also much safer and can move more people and ore than vertical elevators. In the past horses and pit ponies were used. In combination with shafts, adits form an important element in the ventilation of

168-420: Is said to have Hallucinogenic effects. Adit Adits are driven into the side of a hill or mountain, and are often used when an ore body is located inside the mountain but above the adjacent valley floor or coastal plain. In cases where the mineral vein outcrops at the surface, the adit may follow the lode or vein until it is worked out, in which case the adit is rarely straight. The use of adits for

192-612: The Dee Estuary in North Wales . It was originally built to drain the lead mines beneath Halkyn Mountain, which were plagued with flooding in their lower levels, but enabled the exploitation of new lodes and was variously used for the extraction of lead, zinc and limestone during its working history. It is part of a network of mines, lodes and natural cave systems – the Halkyn United Mines – that extends for up to 100 kilometres,

216-713: The Holywell Boat Level. Following takeover by the Halkyn District United Mines Ltd in 1928, the tunnel was progressively extended, reaching Olwyn Goch in 1931 and intersecting several valuable and productive new veins. Low lead prices in 1938 caused the majority of the workforce to be temporarily laid off, but Pilkington's Glass began using the tunnel to excavate high-quality limestone from 1939; this quarrying continued until 1969, creating large artificial caverns west of Olwyn Goch. Lead mining commenced again in earnest in 1948 after ore prices climbed, and

240-686: The Sieberstollen were flooded. Two years later a hydroelectric power station was installed 190 m beneath ground in the Samson Pit. It is one of two underground power stations in that pit which generate electricity from the waters of the Oderteich . The Sieberstollen is discharging its water into the Sieber. Until now the Sieberstollen is the deepest draining adit in Sankt Andreasberg. The water here

264-509: The UK. The Milwr Tunnel was purchased by Welsh Water in 1992 in order to supply water to industry; as of 1997 it still discharges an average of 23 million gallons of water per day. The tunnel is currently maintained by United Utilities . Although a complete trip through to the portal is no longer possible due to roof falls and consequent flooding in the lower sections, occasional access is permitted to cavers and mine explorers, who have mapped many of

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288-570: The adit had an overall length of 3530 m. In the following years the adit was expanded and connected to other mines. In 1804 it was connected to the Wennsglückt pit. To raise the water from adits beneath the level of the Sieberstollen flatrot systems driven by water wheels up to 12 m were used. Two of them were in the Samson Pit beneath the Sieberstollen. In 1910 mining activities in Sankt Andreasberg were stopped. All constructions beneath

312-525: The beginning of the 18th century the 25 mines in Sankt ;Andreasberg had their highest output and the deepest drainage adit Grünhirscher Stollen had reached its limit. In 1716 the construction of the Sieberstollen had begun at the base of the Sieberberg mountain. The adit was driven through from two ends with hammer and pick only supported by four lightholes. When the first phase of construction had finished

336-399: The enormous cost. Adits were used in Cornwall before 1500, and were important to the tin and copper mines in Cornwall and Devon because the ore-bearing veins are nearly vertical, thus acting as ingress channels for water. Milwr tunnel The Milwr Tunnel is a mine drainage adit running some 10 miles from the hamlet of Cadole near Loggerheads, Denbighshire to Bagillt on

360-450: The extraction of ore is generally called drift mining . Adits can only be driven into a mine where the local topography permits. There will be no opportunity to drive an adit to a mine situated on a large flat plain, for instance. Also if the ground is weak, the cost of shoring up a long adit may outweigh its possible advantages. Access to a mine by adit has many advantages over the vertical access shafts used in shaft mining . Less energy

384-504: The famous St Winefride's Well . Supporters of the Milwr and District Mines Drainage Bill pointed out that mining had already been carried out in the area without substantial disruption to the area's water supply. However, legal changes passed in 1913 allowed the HMTC to continue driving the tunnel, at rates of up to 45 feet weekly, to a point beneath Halkyn Mountain by 1919. At 6am on 5 January 1917,

408-505: The invention of the steam engine this was the main restriction on deep mining. Adits are useful for deeper mines. Water only needs to be raised to the drainage adit rather than to the surface. Because of the great reduction in ongoing costs that a drainage adit can provide, they have sometimes been driven for great distances for this purpose. One example is the Milwr tunnel in North Wales, which

432-607: The longest in the United Kingdom . It forms part of the mine drainage system that is responsible for draining Ogof Hesp Alyn and leaving much of the River Alyn between Loggerheads and Rhydymwyn dry during summer months. The first phase of the tunnel was driven by the Holywell-Halkyn Mining and Tunnel Company, a consortium of local mines, under the supervision of engineer Nathaniel R. Griffith of Wrexham . The Company

456-469: The remarkable Powell's Lode Cavern on the Rhosesmor branch tunnel. This is a natural passage at least 110 metres (361 feet) from top to bottom, at least 60 metres of which is flooded by a natural lake (the full depth of the lake was never measured, and large amounts of mining debris dumped into it have since reduced its depth to 42 metres). The cavern can therefore claim to be the highest such natural cavern in

480-514: The tunnel broke into a "loch", or flooded cavern, at the intersection of the Pant Lode: 10,000 gallons of water a minute flowed into the tunnel, sweeping away trucks and seriously hampering work for some weeks. 11 hours later St Winefride's Well, where water from the Halkyn Mountain system had resurged several miles away, ran dry as the water table fell. Water was eventually restored to the well via

504-424: The tunnel to supply water to its factory at Holywell. Lead mining was still carried out sporadically from existing veins until 1977, and maintenance work continued until 1987, when the tunnel finally closed. During its period of operation the tunnel had produced around 200,000 tons of lead ore and 80,000 tons of zinc ore. The tunnel system intersects with many mines as well as several natural cave systems, including

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528-466: The tunnel was driven further south through several new lodes, in 1957 reaching a point at lode 477, the Cathole Vein, at which large quantities of sand and clay were being forced into the tunnel: no further extension was made beyond this point. In 1962, the Holywell-Halkyn Mining and Tunnel Co. Ltd, together with Halkyn District United Mines Ltd, became subsidiaries of Courtaulds , which wished to maintain

552-593: Was commenced in July 1897 at Boot End, Bagillt, from a point 9 feet below high water mark on the Dee foreshore, where self-acting flood doors were fitted. It was driven at a gradient of 1:1000, initially brick lined where it passed through coal measures and shale , and unlined after the first 1.5 miles where it passed through chert and limestone , successively reaching the Pen-yr-Hwylfa, Dolphin, Drill, Coronation and Caeau veins;

576-492: Was formed in 1896, its Secretary and Manager being John Philip Jones, and its directors listed as the Hon. C. T. Parker, H. A. Cope, J. B. Feilding, T. Snape, John Brock, Henry Taylor, and Eustace Carey. The mines involved hoped that the construction of the tunnel, by allowing them to work rich seams of ore at depth without incurring high pumping costs, would enable them to meet their low-cost international competition head-on. Tunnelling

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