This was first entered by myself about 1988 and at that time it was thigh deep in water. It was found to be a straight heading for about 200 metres, passing a blocked rise on the right and a blind heading on the left. The blind heading contained the remains of a wheelbarrow. After the straight section, the level turned south for about 70 metres and then west. On the right, a short level has been made into an explosives store and this has the remains of a wooden door. After passing another short level on the left leading to a winze, the level reached a collapse. Although this could be passed, it was blocked a few metres further on by another solid collapse.
In 1994, I returned to the mine in order to descend the aforementioned winze. There was a length of timber across the level, put there for this purpose by other explorers. I considered this inadequate, however, and placed a number of bolts. The winze was found to be 48ft deep to a solid bottom, where there were a number of sections of ladder which had fallen away from the sides of the shaft. There was a window to the west into a large stope, a floor of rubble being gained after a further few feet. Here, water coming down the shaft disappeared into the floor. Progress inbye was prevented by a continuation of the collapse from the adit above. Above a bank of deads, the stope extends about 15 metres in an outbye direction. This was the limit of my earlier explorations however, towards the end of the level, a gap in the boulders draughted strongly and this was to be the subject of my recent attentions.
In the winter of 1996, I returned to the mine as part of what I was now calling my "Mid-Wales Project". The object of this was to gain access to workings not previously entered by modern explorers. The water level was now upper chest and, in the freezing weather conditions and chill factor winds prevailing at that time, this made changing out of a wet suit at the end of the day something of a feat of endurance. The object of the exercise was a dig at the draughting area at the end of the main level. This required a considerable amount of timber but the deep water, however, was to be a blessing as it was quite easy to make it up into little rafts and tow it down the level. The dig being vertical and in loose material has required special considerations. Initially it was necessary to squeeze past a boulder of slightly questionable stability. It was very tight and, although only about 8ft, I fitted a short length of electron, without which it would have been impossible to get back out. This boulder has subsequently been half chiselled away and secured with a scaffold pole plus some shoring to support the ground underneath it. Also a steep rubble slope was encountered immediately below the dig. I have consolidated this by driving in road steels to pull in a horizontal length of timber, at a place where a step is very conveniently placed. My fear was that disturbance of the rubble slope by exploration parties could compromise the integrity of the dig.
The dig leads down to the head of a stope, which has been filled with collapse material and backfill. It is the same one reached by the 48ft winze. Descending the rubble slope and ascending a slope of backfill, the horizon of the adit is regained. The horizon is made up of backfill in a stoped out area with a height of about 4 metres. Here there is a very interesting artefact, a wheelbarrow made without any legs in near perfect condition. These wheelbarrows are of a type known in Derbyshire as "Sough Barrows". The word sough is a Derbyshire name for a drainage level and Derbyshire soughs are often very confined spaces, hence the design of the barrow. The Henfwlch version, however, is somewhat larger and is fitted with a cast iron wheel.
The level continues for another 200 metres or so to end at a collapse of what appears to be dried-out mud from the surface but on the left is another winze. Before this, two blind headings are passed on the right. The first has an enamelled teapot, now almost rusted away and the second has been half backfilled. One section has extensive packwalls and, at this point, there are stubs of many tallow candles. The winze at the end was descended after some difficulty in providing a suitable belay. The walls of the level are in a soft mudstone, the same kind of ground seen at the Hafan Mine to the south-west. This is a different kind of ground to the rest of the mine. It was obviously unsuitable for bolting and I was also unable to make a satisfactory belay with scaffold poles after dragging them through the levels. My final resort was an Acro prop. The winze also required the use of electron ladder due to a slope of soft ground at the top. It was found to be 40ft and blind, being merely a trial.
Obviously the burning question is that of a possible connection with Hafan. Rather than give an opinion on this, I shall try to reiterate the facts and leave the reader to make their own conclusions. One of my colleagues has suggested that they must connect because the water running down the 48ft winze must be exiting at Hafan Deep Adit, however this is not necessarily so. David Bick states that the mines never connected and that water could be finding its way into Hafan by natural fissures. Indeed, at the end of the workings several veins can clearly be seen to take the form of natural mineralised fissures rather than solid rock.
The geological survey seems to suggest that the two mines do connect but without saying so in so many words. It describes the Henfwlch Adit as "draining the principal or Hafan shaft to a depth of 24 fathoms. About 83 fathoms further west the Bog shaft is drained by the same adit". Plotting the course of the adit on the OS map puts the collapse at my dig to correspond with the shaft on top of the hill adjacent to the quarry (NGR SN735882). This must be the principal shaft referred to by the British Geological Survey. Plotting the rest of the adit on the map takes one to a point only about 80 metres from the head of the Hafan incline, where the Hafan workings start. To add to the controversy, David Bick describes Hafan Deep Adit as being driven for 250 fathoms (500 yards)! This would most certainly take it below the horizon of the Henfwlch workings.
Exploration of the workings described is both easy and straightforward, all in there are about 600 metres of workings that can be explored without vertical techniques. On a subsequent visit I was easily able to lower the water level to belt depth so a little more work would reduce this level still further. The dig is reasonable for anyone of average build but would probably be impossible for anyone of wider girth. The 48ft winze is both safe and straightforward, the water flow can be stemmed by a little damming in the level. This mine should provide interesting exploration for many years to come.
extracted from "Henfwlch Mine Explored", Roy Fellows, SCMC Journal No.5
Last revised: 21 April 1998