This text is from Cris Ebbs book (reproduced with permission) ‘The Milwr Tunnel - Bagillt to Loggerheads 1897 - 1987’
The first people known to have mined for lead in Clwyd were the Romans. They worked those veins that outcropped at the surface on Halkyn Mountain, Meliden, Abergele and Minera and formed the ore into ingots for shipping from the coast at Flint. Following the departure of the Romans it seems that virtually no mining was taking place in the area until the 13th century, when local farmers attempted to supplement their incomes by small-scale operations, limited to shallow pit or trench-type excavations. Ore at this time could still be found at or very near the surface and mining continued intermittently along these lines until surface deposits had been exhausted around the 17th century. Flooding became a problem when deeper working was limited by the pumping technology available.
Things began to improve by the late 1600’s when increased ore prices and improved technology resulted in deeper shafts and the driving of adits to drain the workings. By the 1890’s many mines had been worked out, at least as deep as water levels, kept down by pumping, would allow. But in 1897 an amalgamation of mine companies began an ambitious scheme to drive a deep drainage tunnel from sea-level at Bagillt. This tunnel, known as the Milwr (Pronounced Milloor) or Sea-Level Tunnel was eventually driven a distance of 10 miles to Cadole near Mold by the year 1957.
It successfully drained over 50 veins and created a labyrinth of over 60 miles of interconnected passageways. At a time when low ore prices were decimating the industry, the Milwr Tunnel was cutting previously unknown veins and making profits from the systematic exploitation of known veins by the removal of ore down to, and even below, sea-level. During the 1930’s up to 650 men were employed by the mine and tunneling records were being broken.
The Milwr Tunnel was begun in July 1897 from a point 9 ft. below high water mark at Boot End near Bagillt (SJ 213 760) by the Holywell-Halkyn Mining and Tunnel Company. Two self acting flood doors were installed to prevent inundation by the sea at high tide and the tunnel headed south-west towards Herward Shaft. The tunnel gradient is 1:1000 throughout. It is initially circular in section, 8 ft in diameter with a channel for water in the floor lft 6 ins deep by 6ft wide. Rails were laid on timbers above the water channel. The tunnel walls are brick lined for 1.5 miles where the tunnel passes through shale and coal measures, but thereafter is in chert or limestone and is generally self-supporting. The tunnel south from this area changes to a square section of 8ft x 8ft. From Herward Shaft it passed through Milwr Mine for a short distance to Caeau Shaft on Caeau Mine, where driving stopped 2 miles from the portal in 1908. The tunnel, at this time, drained an average of 1.7 million gallons per day or 1200 gallons per minute. The fastest rate of tunneling was 54ft a week.
In 1913 an Act of Parliament allowed the company to extend the tunnel which reached the limit of its mineral boundary in 1919 at the hamlet of Windmill on Halkyn Mountain. Rates of advance of 40 to 45 ft a week were achieved during the early years of the first World War. A two shift system was operated; one drilling, the other for shooting (blasting) and “mucking out”. Each charge or blast gained an advance of 4 ft.
Upon reaching the companies boundary in 1919 Caeau Shaft was sealed off and all work on the tunnel was again halted. At the intersection of the Pant Lode, a flooded cavern, known locally as a loch or vugh, was cut at 6 a.m. on 5th January 1917 which caused St Winefrides Well at Holywell, 2.5 miles to the north, to run dry 11 hours later. The burst of water swept loaded trucks along the tunnel until they jammed and sand blocked the tunnel, being 2 ft deep at the entrance, seriously hampering progress for many weeks. Water levels in a number of neighbouring mines were also affected.
Following a takeover in 1928 by the Halkyn District United Mines Ltd., Caeau Shaft was re-opened and the 5000 ft to the tunnel face at Windmill was reconditioned to cope with the large volume of water now flooding the rails.
The tunnel floor was sectioned off and one side filled with debris from the face upon which the rails were laid 3 ft above the original floor. The tunnel now rapidly pushed south beneath the Catch area reaching Pen-y-Bryn Shaft in July 1929. Driving south the tunnel was now driven larger in section being 10 ft wide and 8 ft high. A water channel, known by an American mining term as “the grip”, was cut to one side of the tunnel 4 ft wide and 2 ft deep. A major branch tunnel was driven east from a point three-quarters of a mile south of Pen-y-Bryn. This was driven for one mile to Rhosesmor where Barclay’s Load and Powell’s Load yielded major deposits and were worked successfully for many years.
As the tunnel progressed southwards to Hendre, an old shaft known as Olwyn Goch was enlarged to 12 by 12 ft 6 ins and deepened to 490 ft the bottom being 27 ft below tunnel level. It was chiefly used for raising men and materials only until the 1940’s when limestone quarried underground was raised here, Pen-y-Bryn Shaft being used for winding ore and materials. At the surface close to Olwyn Goch Shaft were the offices, changing rooms, bath houses and lamp rooms sufficient for 500 men. For ease of access, a passage was driven into the shaft from a point immediately behind these buildings. Fixed ladders, supported by platforms in the side of the shaft, also provided an alternative route to surface for the men in an emergency.
By 1938 the tunnel had reached the Pant-y-Mwyn Vein when low lead prices once again halted progress. All but 40 of the 650 men were made redundant and an era of great productivity drew to a close.
In 1939, Pilkingtons of St. Helens became interested in the high grade limestone of the mine for glass making and work began excavating large quantities of the stone, chiefly from the area to the west of Olwyn Goch shaft. Excepting the war years, this underground quarrying continued until 1969 and resulted in a series of impressive chambers, some up to 80 ft high, which if joined end to end would extend for 2 miles. Limestone output was 70,000 to 80,000 tons per annum.
During the war twenty storage chambers were sub-let by Halkyn Mines to the Ministry of Supply for the storage of T.N.T. The chambers, each about 80 ft long by 30 ft wide were scattered throughout the workings, most being in the areas of Pen-y-Bryn Shaft, the Rhosesmor Branch Tunnel the Olwyn Goch Shaft and some at the level of the Halkyn Tunnel 200 feet above. The space for storage amounts to over 16,000 cubic yards. Each chamber was fitted with a timber floor and was protected from drips by the installation of corrugated iron “roofing”. Although enormous quantities of T.N.T. were housed here, all chambers now lie empty apart from the concrete slabs that supported the timber flooring.
A jump in lead prices in 1948 prompted renewed activity at the main tunnel face and after a 10 year stoppage, it advanced south; lode 530 was discovered, which was rich in ore and provided work for 10 more years. Mid-way between Gwernaffield and Cadole during the 1950’s the tunnel struck lode 524 on the Pant-y-Buarth Vein, followed by lode 501, both rich veins which were worked until the tunnel reached its present end in 1957 at the Cathole Vein just yards before the main Mold-Ruthin road.
This lode was unproductive at this point but a feeder brought in large volumes of sand and clay with water from cavities above although no connection was made with the old workings.
No lead was mined from 1958 to 1964 when work centred on the limestone mining at Hendre. A final jump in ore prices in 1964 kept the few men busy until 1977 removing ore from the existing lodes when the workforce never exceeded 40. Thereafter work revolved around maintenance and tunnel repairs until final closure in 1987.
The lead mines of Flintshire, since records were kept in 1845 up to the first world war, produced a total of 400,000 tons of lead ore and over 100,000 tons of zinc ore. Since then, the Milwr Tunnel and associated lodes have produced an impressive 200,000 tons of lead ore and around 80,000 tons of zinc ore during its lifetime, the majority being extracted prior to 1957.
The Milwr tunnel today disgorges an average flow of 23 million gallons per day, rising to 36 million in wet weather. Two thirds of this water issues from two cave systems intersected by the workings. The chief source of one of the feeders was found in the Rhosesmor branch tunnel where Powell’s Lode was intersected with a flow of 5000 gallons per minute coming from a flooded cave passage and in 1931 a natural chamber (Powell’s Lode Cavern) was discovered.
Measuring 130 ft x 220 ft, it contains a lake to one side over 200 ft deep. Adding to this depth the height above water level of 150 ft indicated on mine plans, it can claim to be the highest natural underground chamber in Britain. In order to mine below sea level in this area a shaft was driven to a depth of 128 feet where pumps were installed capable of handling 14000 gallons per minute, the largest mine pumping complex in the UK. The lake was lowered by 120 feet but has now risen back to the level of the Rhosemor branch tunnel.
Rolling stock during the 1930’s consisted of one diesel locomotive, one tandem battery loco, two single battery locos, 360 mine cars of 18 cu ft capacity and a number of passenger cars known as man-riders. The double bogie diesel loco, first introduced in 1933, weighed 7.5 tons and was capable of hauling 60 loaded cars. The tandem battery loco comprised two separate units connected by jump leads and a swivel coupling. The combined unit weighed 5 tons and was capable of hauling 50 loaded cars. The remaining battery locos each weighed 2.25 tons and were rated at 6 m.p.h. Three hundred and ten of the mine cars were end-tippers and the other 50 were box cars. Each car was numbered, a record kept of each service or repair and servicing was carried out at a workshop at tunnel level beside Olwyn Goch Shaft. The track gauge used throughout was 22.5 inches.
By 1936 the tunnel face was about a mile south of Rhydymwyn and with an average of 150 men underground at each shift, distributed in a number of different lodes over some six miles, a system of traffic control became necessary. Generally two small locos, one at lode 675 beneath Rhosesmor and the other at the main tunnel face, acted as feeders supplying loaded cars to a larger loco which then took a full train to Pen-y-Bryn Shaft for processing.
Charging of the locos’ batteries was done at the surface at Pen-y-Bryn until later years when a charging bay was installed underground at Olwyn Goch shaft beside the compressor chamber. Ultimately the number of diesels in use was increased to three together with a number of Eimco rocker shovels to cope with production from the limestone workings below Hendre from the 1940’s. These machines used for rock loading were compressed-air operated wheeled shovels mounted on the rails and positioned between the broken rock and an empty car.
Prior to final closure the workforce of no more than 10 men based at Olwyn Goch was kept busy sealing off a number of lode and tunnel junctions, to prevent falls from the stopes above blocking the main tunnel. Many open surface shafts were capped for safety reasons and much of the underground machinery was brought to surface and sold for scrap. The last miners to see the bottom of Olwyn Goch Shaft were hauled out of the shaft on 10th December 1986.
The cage guide wires were cut at the shaft top on 13th February 1987 and the shaft was sealed with a large concrete plinth not long after.
The headframe and 1930’s winding gear were dismantled and taken for re-erection to Dolicothau mining museum in Mid Wales. The mineral lease finally expired 4 years later in April 1991, mineral rights reverting back to their owner, the Grosvenor Estate.
Today the condition of the main tunnel is generally good. The northern older section from the portal to Pen-y-Bryn Shaft contains a number of roof falls and consequently deep water in places. The section from Pen-y-Bryn to Cathole Lode has suffered little since closure except for a few slabs of shale fallen from the tunnel roof. The Rhosesmor branch tunnel has also suffered no serious collapse. Many of the lodes however have failed to escape the ravages of time. Waste rock was frequently stacked on timbers high in the stopes and where these have deteriorated and fallen away, unsupported boulder piles can be seen high above tunnel level. In lode 656, severe ground movement has occurred since it was mined, resulting in car-sized boulders perched precariously at varying heights throughout the main stope. Whilst these lodes are extremely unstable, many others could be regarded as negotiable by those with knowledge and experience of mine exploration. However, little remains in most of these stopes and it is difficult finding safe routes up into the more interesting ‘old mans’ workings, generally 200 - 300 ft above tunnel level. However, all access points into the mine have now been sealed off and a sturdy grille fitted across the portal.
Although it was general policy to remove all equipment from exhausted lodes, a surprising amount still remains scattered throughout the workings today. The railway track from Pen-y-Bryn to within half a mile of Cathole Lode and along the Rhosesmor Branch is completely intact totaling over 6 miles. At Olwyn Goch Shaft in the main tunnel lie two diesel locomotives, a loaded train of about a dozen cars, a double bogey rail transporter and a diesel supply truck for supplying the locos. The compressor chamber in this area was turned into a workshop in later years and although most equipment was removed, much in the way of spanners, jack-hammers, work-benches and fittings still remain, although dry-rot is rapidly taking effect. The charging bay beside the workshop is almost complete and exhibits a battery loco connected ready for charging.
At Pen-y-Bryn Shaft there are two man-riders and a covered truck used for the conveyance of one of the managers specially constructed for the purpose. The limestone workings west of Olwyn Goch also contain up to 40 mine cars together with several Eimco shovels. Many examples of timberwork exist in the form of ladderways and ore chutes throughout the workings and not to be overlooked are the several places used by the miners for discarding rubbish. At such places can be found old boots, cigarette packs, old tins, newspapers etc. dating back to the 1930’s. Other items of interest include a compressed air cement mixer in the main tunnel north of lode 656 and the onsetters cabin at Olwyn Goch Shaft, looking much like it did prior to closure. Oilskins hang on a hook on the wall, an old magazine rests upon the desk and a Billy-can sits on the table possibly forgotten by the last men out.
Little remains on the surface as all headframes have now gone and all shafts connecting with the tunnel have been sealed off. At Olwyn Goch Shaft the office buildings remain, together with a few milling sheds but their contents were removed prior to closure.
In November 1992 the Milwr Tunnel was purchased by Welsh Water as a water source for local industry. As they required access to the tunnel for maintenance, the Olwyn Goch Shaft ladderway was made safe. Welsh Water have also allowed access to the tunnel and associated mine workings. This is administered by the Grosvenor Caving Club under strict conditions imposed by Welsh Water.
- The Milwr Tunnel - Bagillt to Loggerheads 1897 - 1987, Cris Ebbs, ISBN 0 9522242 0 8
- Grosvenor Caving Club