Ogof Fechan, Ogof Fach

NGR: SN 97065 09730
301 m.asl

Rhondda Cynon Taff , Northern Outcrop - Central (Penwyllt to Penderyn)
map using leaflet map:
Sink Cave
Access From Penderyn take the turning opposite the Lamb Hotel towards Cwm Cadlan. Follow the road along the Cwm until it reaches the farm of Wernlas. A track leads past the farm, crosses a stream and then peters out. Head across the field towards a gate in a stone wall. Beyond the gate bear right and descend to the floor of the valley where a stream sinks at the base of a small rock outcrop. The entrance to the cave is below corrugated sheets near the top of the outcrop. Access Permission to visit the cave should be obtained from Wernlas farm.
Description An interesting and sporting cave, most of which is active streamway with very few side passages. The muddy entrance shaft leads to a small chamber. The stream can be heard to the left but the way on is to the right through boulders in the floor to a narrow rift. A climb down the rift leads to a crawl which in turn leads to the streamway. A section of fine streamway then follows until the water disappears on the right. A low crawl straight ahead leads into Sand Chamber. Bearing left across the chamber, Inlet Stream Passage comes in from the left while under the right-hand wall a hole leads down through boulders to the stream. After a very short distance the water disappears again and a distinctive crawl developed in a shale band is followed to the right. The crawl rejoins the streamway after about 10 m at the bottom of a steep water chute. Downstream, a low section of passage is followed to a small waterfall into a chamber. Beyond the chamber is the Wet Crawl or First Canal. This is a hands and knees crawl in water leading to a large chamber with a high mud bank on the left-hand wall. The stream flows through the chamber which gradually loses height to the start of the Canal, this being another hands and knees crawl in water but this time much longer, about 45 m. At the end of the Canal, the water again disappears to the right but straight ahead is the West Rift, a narrow passage with some fine calcite formations and deep water at the end leading back into the streamway. Downstream the passage soon becomes blocked by a large boulder choke which is passed by going to the top of the choke and then up through a small hole into an aven. The way on then leads to another aven and then much crawling and scrambling over and under boulders follows. The route gradually works its way back to the stream and then to Sump 1. Sump 1 goes off to the left of the sump pool but it can be bypassed via a duck straight ahead. There is a line running through the duck to a narrow cross passage on the other side. A short distance to the right beyond the duck there is a tight awkward climb up which emerges in the floor of a high level passage. In one direction the passage ends after a very short distance while in the other direction it leads for about 55 m to Waterfall Chamber. By crossing the chamber and following the left-hand wall leads to the large an impressive streamway. Upstream after about 30 m is the downstream end of Sump 1 while downstream the passage gradually becomes lower to end at Sump 2 after about 76 m. SUMP 2 IS ONLY PASSABLE TO DIVERS AND IS 15 M LONG There were food dumps and survival bags in the terminal choke in case of the canal flooding.
History Monmouth School CC in 1950's. Extended by OUCC in 1965, Extended by WSG in 1970
SAM: GM520
WSG (1972)
OUCC Proc. 4, 1965, p.22
WSG Bulletin, Vol.6, 9. Survey
p.103 diving
WSG Bulletin, Vol.7, Geoff Bull; Dave Everett (1972), pp.93-98
Descent 14
Caves of South Wales, Stratford, T. , 1995
Cadw Most of the cave, but not the entrance, is under the site of a mediaeval hamlet which has Scheduled Ancient Monument status.
Brendan Marris Caves of South Wales
Cambrian Cave Registry entry 695
© Cambrian Caving Council ⓗ 2017