South Wales Caves

Ogof Fawr Cave Description

Ogof Fawr is a recently discovered cave (map), having being entered by the diggers after a concerted period of excavation. The site has been long known as a large stream sinks at this site and in view of the potential was named Ogof Fawr (large cave) another small site lower down the valley was called Ogof Fechan (little cave). The irony was that after prolonged digging very little cave was found at Fawr, but Fechan yielded a sizeable stream cave. The site has been dug over several periods, but after two years of digging the team led by Tony Donovan discovered a sizeable cave at Fawr in 2008 and exploration continues. This cave is formed in steeply dipping beds of limestone and is out of character with most caves in South Wales. In many ways it is similar to Ogof Fechan as the cave is extremely flood prone and most passages are covered in a thin film of mud making the cave feel very oppressive. It cannot be understated how at risk of flood this cave is, with debris found up to 2m above the cave sink after heavy rain. In wet weather the cave completely floods in large sections, this is a cave to avoid in unsettled weather. The cave is very near a National Grid gas storage facility so security is very tight and exploration is still underway so please contact the diggers before visiting this site.
The stream sinks in a cliff face in a very large depression, flooding causes the original entrance route through boulders to rearrange regularly, a new drier entrance has been engineered near the cliff face at the back of the depression. A descending passage following the dipping beds of limestone drops you a scaffolded shaft that leads to a further crawl and climb down in lower bedding planes. This finally drops via a short climb down into the top of a chamber, in which close by on the right hand wall by a large boulder is a rope climb down. From the bottom of the rope climb you find a small passage leading off on the right. This brings you into a second chamber where you traverse across loose boulders to descend near the right hand wall. This steeply descending passage is then followed to meet the water further down and continues to a junction with a large flat topped boulder in the centre. Ahead the water descends a narrow rift to enter a large steeply descending chamber. The water sinks in the boulders at the top of the chamber, at the bottom end of the chamber a climb down through mud covered boulders leads back to the stream which quickly disappears into a boulder choke. In wet weather water backs up here very badly, the whole chamber filling up with water, foam can be found over the flat topped boulder back at the junction. From the junction a passage leads off to the right and continues for a long distance as a linear passage cutting across the dip of the rock. The whole passage is covered in a thin film of mud and it is clear from this and damage to the conservation tapes that much of this passage floods in wet weather. A section of this passage contains fine mud covered calcite formations before the passage assumes a more phreatic tube and passes under an impressive rock bridge. From here the passage passes a through faults and more unstable rock past several squeezes to follow a hole in the floor and a low level crawl. This then enters a more phreatic section of passage after a fault is passed where the route splits several times most passages joining back together. At the end of this most open section of passage a boulder choke is passed dropping between rocks into more passage. Now the passage is more controlled by bedding planes and in places high and low level routes are possible in the same bedding plane. The cave ends in a wide low section of cave with layers of rock that have peeled off from the ceiling.
This whole cave is very unstable and extremely flood prone - treat with due care