Cambrian Cave Registry

L: V:20	Pwll Derw, Oak Hole, Pwll Derwen (in error) NGR: SN 94133 12371 339 m.asl Powys , Northern Outcrop - Central (Penwyllt to Penderyn)			map using leaflet map:
Sink
Access	Enter the land under the fence at BM 1110, 45 metres North of the Ystradfellte signpost.
Description	A very large collapse feature about 280 metres around, taking a stream in the Western corner, which sinks in many places. It is about 15 metres deep and lies on the fault line running through the Hepste valley below the bridge.
History	WSG 1968; Mike McCombe, Jon Jones 2004
Hydrology				Tests
Conservation
Gallery
^{Alan Bowring} 2007	^{Brendan Marris} 2009
Survey

References
WSG Bull 5(8),76-77, Tony Jones, Scratching in South Wales
Pelobates 53, Allan Ockenden, 1988
WSG Bulletin 9(8) 1997 Duncan Minty, Hydrological Investigations in the central Brecon Beacons
Descent 171, p.13, Martyn Farr, Attacking Pwll Derw
Descent 181 p.14 (2005) Digging Pwll Derw
Croydon CC Pelobates 90, 2014. Adrian Paniwnyk, Caves of the Mellte Valley Update
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Cambrian Cave Registry entry 616			© Caving Wales ⓗ Ogofa Cymru