{"id":6041,"date":"2025-12-01T23:32:47","date_gmt":"2025-12-01T22:32:47","guid":{"rendered":"https:\/\/subterranologie.com\/milwr-tunnel-histoire-mines-galles\/"},"modified":"2025-12-18T23:53:53","modified_gmt":"2025-12-18T22:53:53","slug":"milwr-tunnel-histoire-mines-galles","status":"publish","type":"post","link":"https:\/\/subterranologie.com\/en\/milwr-tunnel-histoire-mines-galles\/","title":{"rendered":"Milwr Tunnel"},"content":{"rendered":"\n

The Incredible Epic of the Milwr Tunnel<\/strong><\/h2>\n\n\n\n

Wales hides beneath its hills an exceptional industrial heritage. Among these underground treasures, the Milwr Tunnel stands out for its scale and ingenuity. Located in the county of Flintshire<\/a>, this colossal structure was not only used for mineral extraction. Its main purpose was to drain the water that constantly flooded the galleries.<\/p>\n\n\n\n

From the romans to the first miners<\/strong><\/h2>\n\n\n\n
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The Romans were already mining lead on Halkyn Mountain, taking advantage of the deposits accessible on the surface. Later, during the Middle Ages, local farmers dug trenches to extract this precious metal, often at the request of King Edward I for the construction of his castles<\/a> (roofs, plumbing, and piping).<\/p>\n\n\n\n

By the 16th century, miners had reached depths where flooding became unmanageable. Even the arrival of the first steam engines in the 18th century was not enough to make extraction profitable compared to the high pumping costs.<\/p>\n<\/div>

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The 19th century: the milwr tunnel, a colossal project<\/strong><\/h2>\n\n\n\n

To solve this problem, the Holywell Halkyn Mining and Tunnel Company launched an ambitious project in 1897. The goal was simple but monumental: to dig a drainage tunnel starting from sea level at Bagillt. This structure was designed to extend underground, allowing the mine water to drain naturally by gravity.<\/p>\n\n\n\n

Engineers designed the tunnel with a gentle gradient of 1:1000 (1%). They even installed automatic gates at the entrance to prevent high tides from flooding the gallery. At the outbreak of the First World War, drilling teams were advancing at a relentless pace of 13 meters per week.
The starting point was Boot End, in Bagillt. The destination: Halkyn Mountain, approximately 10 miles away. Work began in July 1897. After several financial pauses, the miners didn\u2019t stop until 1957.<\/p>\n\n\n\n

At first, the tunnel workers used brick lining, as the tunnel was being dug through coal and shale. When it finally reached limestone more than a kilometer and a half in, the lining was no longer necessary.<\/p>\n\n\n\n

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\"Magasin
Magasin \u00e0 poudre explosive situ\u00e9 dans la galerie de drainage<\/figcaption><\/figure>\n<\/div>\n\n\n
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The 1917 disaster<\/strong><\/h2>\n\n\n\n

The progress of the tunnel was not without mishaps. In January 1917, the workers broke into a flooded cavern. The result was disastrous. A torrent of water\u2014about 10,500 gallons per minute\u2014rushed into the tunnel, sweeping away everything in its path.<\/p>\n\n\n\n

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WWII: strategic military use<\/strong><\/h2>\n\n\n\n

During the Second World War, the mining operations changed radically. Twenty storage chambers were subleased by Halkyn Mines to the Ministry of Supply. Their purpose: storing TNT.
Each chamber measured roughly 80 feet long by 30 feet wide and was spread across various workings. Most were located in the Pen-y-Bryn shaft<\/a> area, while several others were found along the Rhosesmor branch tunnel.<\/p>\n\n\n\n

The total storage capacity exceeded 565,000 cubic feet. Each chamber had a wooden floor, and a corrugated iron \u201croof\u201d protected it from water drips above.
Despite the enormous quantity of TNT once stored there, all the chambers now stand empty. Only the concrete bases that supported the wooden floors remain. This military chapter represents an important, yet often forgotten, part of the site\u2019s history.<\/p>\n\n\n\n

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\"Ancienne
former tnt storage room<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n
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Resumption and expansion: a new mining dynamic<\/strong><\/h2>\n\n\n\n

The Holywell Halkyn Mining and Tunnel Company was purchased in 1928 by Halkyn District Mines Ltd, reigniting a new phase of vigorous expansion. The Olwyn Goch Shaft was reached in 1931.
Underground operations required complex logistics. <\/p>\n\n\n\n

The Olwyn Goch Shaft, about 500 feet deep, served as the main lift for men and equipment. In winter, the cold was so intense that icicles formed inside the lift cage, forcing miners to run empty trips just to break them off.<\/p>\n\n\n\n


A vast railway network threaded through the galleries. Diesel and electric locomotives hauled hundreds of ore wagons, and a fully equipped workshop was installed at the heart of the network to maintain these machines.<\/p>\n\n\n\n

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