During a caving visit to Porth-Yr-Ogof on the 11 Nov 16 a 1.5ft stone dam wall was found in the tradesman’s entrance at the top of sump 4. This dam wall was found to be diverting water from the passage way leading to sump 4.

A second dam was discovered downstream from the entrance from sump 4 diverting water from the main passage into the small passageway (Sarah’s passage/rat run) leading back to the main chamber underneath the flowstone.

Both of these constructions have been dismantled however some remnants of the dam may end up in the sump.

Care should be exercised whilst operating in the area and a check of the passageway and sump 4 may be an appropriate course of action before use.

The movement of rocks to make the dam also causes the potential for the rocks to wash into areas they wouldn’t naturally end up so caution is advised.

Please take care in this section of the cave while things return to normal flow.

It is worth noting that the building of dams and diversion of water flows within a cave system is not appropriate. This is not something that users would expect to happen and creates an unnecessary risk to the many led groups of novice cavers that use cave.

Thanks to both Dan Thorne and the Soldier Development Wing for flagging this up.