CP17

The entrance is a large snow shaft, descended between snow and wall for the first five metres. One then finds oneself in a vast gallery 3 metres wide and 7 metres high that plunges at 40° into the bowels of the earth.

The snow is left around -15 m in favour of a floor cluttered with large blocks of ice and rock. 20 m further on opens a pretty P11. The water disappears into a meander that is too narrow. At the top of the last shaft of fifteen metres, a constriction gives access to a small upstream section: the beginning is not very inviting as it opens in the Hauterivien, but after a two-metre step, the passage into the Urgonien transforms it into a small forced conduit 1.2 m in diameter. It abruptly ends 50 metres further on against a wall and is found silted up with scree. It is interesting to note that if the forced conduit develops in the Urgonien, the water flows on the Hauterivien in a small incised channel.

At the base of the shaft, one can climb up a fossil slope that leads to a selective constriction at the top of a meander, the base being filled with scree. Behind the constriction, a ten-metre gallery cluttered with blocks leads, after another constriction, into a small watered chamber, silted up with scree and clay.

The small forced conduit 1.2 m in diameter is adorned with pretty helictites of a surprising pink.

The P11 allows one to reach an important active stream estimated at between 20 and 50 litres per second, which probably corresponds to the water that is lost in the CP26. The water disappears into a meander that is too narrow and one must climb slightly to find it a few metres further on as it plunges into a last shaft of fifteen metres. The bottom of the shaft is particularly watered and the water is lost on the one hand in a sump and on the other hand in scree. In the small watered chamber, the water arrives through a crack in the ceiling and is lost in a small sump.

The P15 is particularly arduous to rig because the spit at the head of the shaft is very difficult to reach owing to the crumbly walls that do not allow a correct handline to be set up. One must therefore climb in opposition at the top of the gallery to reach two natural anchors that then allow a delicate pendulum to be made that gives access to the spit: plan for a tall acrobat to rig this shaft.

A small tube with a weak draught leaves near the scree where the water from the bottom of the shaft is lost, but it quickly becomes impenetrable.