4606: Grietas, Las
Barrio de Arriba 30T 445583 4799357 (Datum: ETRS89. Accuracy code: G) Altitude 175m
Length 267m Depth 25m
Area position

Updated 31st December 2017; 12th May; 26th September 2018

   This was first discovered as a walk-in rift cave which was explored for about 60m being stopped by an awkward traverse. Ten pitches (all blind) were subsequently explored in a passage described as "not easy with difficult traversing (at times) at roof level. The rift meets a cross rift. On the right, beyond a second pitch, a tight section is reached where only a thin person will be able to pass by traversing at the very top of the rift. The left hand branch is similar. The right arm draughts well. (Minor amendments were made to the survey, 31st December 2017.)

   Four pushing trips were undertaken in April 2018. A 20m traverse from the inlet at present mid-point crosses a 10m deep pitch. Flowing water at the base heads towards the main junction although both up and downstream passages are too small. This traverse ended at a block in the passage and was too small to follow in SRT gear. Consideration of the geology suggests that this is an inlet to the main system and that the way on is downwards at or near the main junction.
    Capping occurred at the main junction into a 3 x 2m chamber. Out of this, another similar size chamber was entered via a 3m pitch with water entering from the south-southeast and leaving in the opposite direction. Silt on the floor suggests low flow, with the flow marked by mud, also observed in the deepest pitch. The flow from the NNE inlet flows SSW towards the deep pitch but the confluence is not seen.
   It is conjectured that the flows seen are perculation water using an existing hypogenic system and there is no large, deep cave accessible from this system.
   The system has been derigged with nuts left on bolts for hangers. Note the environment is aggressive towards aluminium hangers, etc.

References: anon., 2017d (autumn logbook); anon., 2018b (Easter logbook)
Entrance pictures : October 2017
Underground pictures : October 2017
Video :
Detailed survey : December 2017 plan pdf : Easter 2018
Line Survey :
On area survey :
Survex file : December 2017