CHA 15-2

Two entrances are available. The upper entrance is fairly narrow and opens onto a descending gallery that soon branches; the first passage downward is too narrow to pass, the second is obstructed a little further on. It is now used to store equipment.

The lower entrance has been enlarged to allow passage; it is now the more visible one. a horizontal gallery gives access to a ramp descending to the left, then to a horizontal gallery heading to the right. At the bottom of this straight section, a widened area allows one to turn around.

a gradual rise in discharge of the springs is observed. When CHA 18-5 is in flow it is still possible to pass, whereas the lower part 10 m from the entrance is entirely flooded when the water flows out through CHA 15-3.

With a flow of 2 l/s at CHA 18-2, water can be heard at the bottom of the cavity with a sound like a pressure pipe. When CHA 18-5 is in flow, a waterfall sound is heard at the bottom.

Roland Poitrey observed that when the flow of the Dranse at the Vacheresse station (https://www.rdbrmc.com/hydroreel2/station.php?codestation=260) reaches 8 m3 it is no longer possible to enter the cavity.