Milwr Tunnel

Length : 10miles!

Entrance grid ref : SJ 213760

No. of entrance shafts : Tens-Hundreds!


The Milwr tunnel is basically a drainage tunnel started from a point on the coast near Bagillt and driven inland for a distance of approximately 10 miles, dewatering all of the mines and caves in the area. The driving of the tunnel also revealed new Lodes of ore.


The Milwr tunnel was started in 1897 from Boot End near Bagillt, and driven inland. A tunnel was also sunk and driven to meet the inland driving. The tunnel progressed inland towards Caeau, and onwards to the Pen y Bryn shaft (SJ202707). This shaft is 800feet deep!. Further onwards, the bottom of the Olwyn Goch shaft was reached.

In 1917, the tunnel drained the Halkyn mountain system, which had previously resurged at St. Winefrides well in Holywell. This didn't do much for those who held beliefs in the waters of the well. The well has now has water restored from the Holywell Boat Level.

By 1939, Limestone was being mined for Pilkingtons glass. The tunnel finally stopped being driven in 1957 at SJ205628.

The water draining through this tunnel caused the River Alyn to dry up, and the caves Hesp Alyn and Poachers to empty.

An examination of the map near Halkyn mountain shows countless shafts, some of which do enter the Milwr Tunnel.

Entry to the Milwr tunnel

To gain entrance to the Milwr tunnel, you have to join the Grosvenor caving club, who are the only people allowed down under some act of parliament, as the tunnel is now owned by the water companies.

Return to caving page.

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All images (C) 2005 - 2017

Last modified on: 25th August 2017 by email the webmaster

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