- site. Ogof Hesp Alyn - Cave of the Dry Alyn
- date. current (water levels permitting)
- location. covered shaft on riverbank downstream from Cilcain Bridge, Pantymwyn
- activities. 2018 extension to Razor Rift, and re-rigging of pitches. Given the difficulty in reaching the end of the cave (not for the faint hearted), there is interest in other caves close to Penysarn including the expanding Leete Cave and Boxer Pot that might link to OHA
- access. OHA was discovered by NWCC in 1974; there are no access restrictions, but care should be taken regarding the serious long-term flooding potential
- background. OHA is a deep phreatic system that has been drained (for much of the year) by lead mining in the last 200 years, but which previously discharged the summer flow of the River Alyn sinking at Loggerheads; the thick mud fills are slowly washing down via various shaft systems into deeper routes of drainage leading ultimately to the Llyn-y-Pandy Lode close to the Milwr Tunnel; this deeper drainage system below and upstream of the known limits of OHA has yet to be entered, posing the greatest challenge for North Wales cavers