Milwr tunnel
Encyclopedia
The Milwr Tunnel is a mine
drainage adit
running some 10 miles from the hamlet of Cadole
near Loggerheads, Denbighshire to Bagillt
on 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, 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 Company 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 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; 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.
, who feared that the proposed drainage would affect their water supply, and particularly that of 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.
Legal changes, however, 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, 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 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 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 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.
branch tunnel. This is a natural passage at least 100 metres (328 feet) deep, at least 60 metres of which is taken up by a natural lake, though probably much deeper (its full depth is still unknown; thousands of tons of waste rock were dumped into the lake over the years without affecting its level). The cavern can therefore claim to be the highest such natural cavern in the UK.
in 1992 in order to supply water to industry; 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 the old workings. Some abandoned mining equipment and several miles of the tunnel's railway system remain in-situ.
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
drainage adit
Adit
An adit is an entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, and ventilated.-Construction:...
running some 10 miles from the hamlet of Cadole
Cadole
Cadole is a village in Flintshire, Wales; the name was originally Cat hole or Cathole and the village was known as this in living memory....
near Loggerheads, Denbighshire to Bagillt
Bagillt
Bagillt is a small town near Holywell in Flintshire, North Wales. At the 2001 Census the population was recorded as 3,918.-History:http://stmarysbagillt.co.uk/...
on the Dee Estuary
Dee Estuary
The Dee Estuary is a large estuary by means of which the River Dee flows into Liverpool Bay. The estuary starts near Shotton after a five miles 'canalised' section and the river soon swells to be several miles wide forming the boundary between the Wirral Peninsula in north-west England and...
in North
North Wales
North Wales is the northernmost unofficial region of Wales. It is bordered to the south by the counties of Ceredigion and Powys in Mid Wales and to the east by the counties of Shropshire in the West Midlands and Cheshire in North West England...
Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. It was originally built to drain the lead mines beneath Halkyn
Halkyn
Halkyn is a village in Flintshire, north-east Wales and situated between Pentre Halkyn, Northop and Rhosesmor. At the 2001 Census the population of the community was 2,876.- History :...
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
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
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, the longest in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
.
It forms part of the mine drainage system that is responsible for draining Ogof Hesp Alyn
Ogof Hesp Alyn
Ogof Hesp Alyn was discovered by in 1973 in the Alyn Gorge near Cilcain, Flintshire, Wales. Reaching the end of the cave is a serious commitment requiring one pitch series and the draining of two sumps....
and leaving much of the River Alyn
River Alyn
The River Alyn is a tributary of the River Dee. The River Alyn rises at the southern end of the Clwydian hills and the Alyn Valley forms part of the Clwydian Range Area of Outstanding Natural Beauty...
between Loggerheads and Rhydymwyn
Rhydymwyn
Rhydymwyn is a village in Flintshire, North Wales, located in the upper Alyn valley...
dry during summer months.
Construction
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 WrexhamWrexham
Wrexham is a town in Wales. It is the administrative centre of the wider Wrexham County Borough, and the largest town in North Wales, located in the east of the region. It is situated between the Welsh mountains and the lower Dee Valley close to the border with Cheshire, England...
. The Company 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 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
Coal Measures
The Coal Measures is a lithostratigraphical term for the coal-bearing part of the Upper Carboniferous System. It represents the remains of fluvio-deltaic sediment, and consists mainly of clastic rocks interstratified with the beds of coal...
and shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, and unlined after the first 1.5 miles where it passed through chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
and limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, successively reaching the Pen-yr-Hwylfa, Dolphin, Drill, Coronation and Caeau veins; 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.
Extension
Objections to further work had been raised in Parliament and by residents of HolywellHolywell
Holywell is the fifth largest town in Flintshire, North Wales, lying to the west of the estuary of the River Dee.-History:The market town of Holywell takes its name from the St Winefride's Well, a holy well surrounded by a chapel...
, who feared that the proposed drainage would affect their water supply, and particularly that of the famous St Winefride's Well
St Winefride's Well
St Winefride's Well is a holy well located in Holywell, in Flintshire in North Wales. It is the oldest continually visited pilgrimage site in Great Britain....
. 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.
Legal changes, however, 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, 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 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
Pilkington
Pilkington Group Limited is a multinational glass manufacturing company headquartered in St Helens, United Kingdom. It is a subsidiary of the Japan-based NSG Group...
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 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
Courtaulds
Courtaulds was a United Kingdom-based manufacturer of fabric, clothing, artificial fibres, and chemicals.-Foundation:The Company was founded by George Courtauld and his cousin Peter Taylor in 1794 as a silk, crepe and textile business at Pebmarsh in north Essex trading as George Courtauld & Co...
, which wished to maintain 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.
Powell's Lode
The tunnel system intersects with many mines as well as several natural cave systems, including the remarkable Powell's Lode Cavern on the RhosesmorRhosesmor
Rhosesmor is a small village near Mold, Flintshire, in north-east Wales. The village lies near the parishes of Halkyn and Rhes-y-cae. The hamlet of Wern-y-Gaer is encompassed by the boundaries of the village.- History :...
branch tunnel. This is a natural passage at least 100 metres (328 feet) deep, at least 60 metres of which is taken up by a natural lake, though probably much deeper (its full depth is still unknown; thousands of tons of waste rock were dumped into the lake over the years without affecting its level). The cavern can therefore claim to be the highest such natural cavern in the UK.
Today
The Milwr Tunnel was purchased by Welsh WaterWelsh Water
Dŵr Cymru Welsh Water is a company which supplies drinking water and wastewater services to most of Wales and parts of western England.It is regulated under the Water Industry Act 1991.-History:...
in 1992 in order to supply water to industry; it still discharges an average of 23 million gallons of water per day. The tunnel is currently maintained by United Utilities
United Utilities
United Utilities Group PLC is the UK's largest listed water business. The Group owns and manages the regulated water and waste water network in the north west England, through it subsidiary United Utilities Water PLC , which is responsible for the vast majority of the group's assets and...
. 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 the old workings. Some abandoned mining equipment and several miles of the tunnel's railway system remain in-situ.