Diving in Rhiwbach Slate Mine

A series of exploratory dives were carried out in 2015 after being granted permits by CAL to see what existed in the lower flooded level. 200m of line was laid (cumulatively) from two separate dive bases. A rough survey was started and a far more accurate one is currently in progress by the divers concerned.

The dives that took place this year (2nd-3rd April 2016) confirmed suspicions that the two separate dive bases connected underwater. Also, a number of artefacts were found and photographed (see CAL gallery). The state of preservation on some being excellent, but left untouched for future visitors and posterity. The flooded levels have now all been explored and are ongoing with permanent line being laid and connection to a further sump (now named 'no fins sump') likely. Diver noted presence of oil on the surface in a remote air bell. Max depth -15m (note: Dive Base 1 sump drops to -30m, but the way on at the discovered adit level is at -15m). Visibility circa 5m on the inward phase. Near zero in places on exit as the mine is very silty. A pair of 300 bar 7's used. A separate exploration dive was undertaken a day later with potential for a further significant connection.

A note concerning cylinder choice... A pair of 300 bar 7's are adequate for a worthy dive, although larger cylinders are an advantage. The main factor is the kit carry to the adit entrance. With some creative equipment packing, the walk to the adit entrance can be accomplished in two trips. Water temp requires a drysuit. However it's worth pointing out that the walk is steep in places and covers a distance of approx 1.7km each way.

The divers also wish to reiterate the dangers of diving in mines. A healthy fear of potential collapse coupled with some personal research of mining techniques goes a long way in prolonging ones life. Particular attention must be paid in large chambers (wet and dry!) where the roof span is considerable. All airbells must be viewed as toxic.


Update 24.12.16

Dive Team: John Carter, Paul Marvin
Support: Sue Marvin

Follow up dive to previous visit (see CDG July 2016 No. 200 newsletter). Intention, further route finding towards surface sump pools (see survey) thereby creating a traverse. Divers entered from dive base 1 and followed previously laid route into kettle passage at a constant depth of 15m. Tied in to line and headed at a rough perpendicular to try and find any ongoing passage (an old abandonment plan suggested there would be, and a quick recce dive in July confirmed a 'black void'). Passageway soon came into view. 130m of new line put into (what is apparent now on the survey), a wide chamber containing various artefacts, including a small slate 'caban' (or hut). The chamber also contained a small short side passage that leads back to dive base 1 (the main working pit 30m deep containing A frame 'blondins').

The old abandonment plan on the CAL website has taken some time in making sense of as it doesn't differentiate with dry and lower flooded levels, and cannot be always taken as actual. However, the dives to date have now started to make sense of it all and an underwater survey produced. Ongoing passage leading to the bottom of a collapsed incline and heading towards sump pools 2 and 3 is the next objective. Divers experienced 6m viz on the way in, zero in places on exit. Previous visits have noted that dive base 1 visibility is affected by rain fall, whereas sump pools 2 and 3 are not. Both divers used a pair of 7 litre cylinders.


Update 12.7.17

Dive Team: John Carter, Paul Marvin
Support: Sue Marvin

60m of line laid in passage heading towards (according to abandonment plan) intersecting incline passage. A large debris pile appeared which partially blocks the passageway (passable on the right hand side), which heralded the find of the intersecting incline passage high on our right. Divers cautiously advanced but soon retreated due to fine rolling silt and loose slate raining down turning the visibility to zero. Tied off and left reel to be carried on another dive.

This left the divers with plenty of gas (air) to do further exploration of the main dive base 1 pool, to see if the sunken bridge as filmed by Aditnow members on YouTube could be found, after a lot of searching at various depths in the area explained to us by the aditnow members the divers believe that this now must have collapsed and is sitting at the bottom.

They did however make a good discovery in finding a old wire rope ladder that leads down to another adit tunnel which leads into the chamber where the hut is and what is now a short cut for us on further exploration making now a lot more of sense of this area, there was also a vent hole found which now explains the huge eruption of air that surface support experienced when divers were down.

Please note any divers diving in here, we have left equipment under the water and that it is not lost and should not be removed it is to save time on our next visit.

© Paul Marvin, Sue Marvin & John Carter