Surface positionning of an underground sump


(continued from the previous mission, surface positionning of an underground river)
Reminder: Our client wanted to realize a drilling in a karstic environment to access water resources in an underground river.

The underground river (or rather the drain) is situated 380m under the surface, and accessible after more than one kilometer of underground cave passages, mostly vertical.

The abyss opens at an altitude of 1800m in the french Alps. Explorations take place in winter, for better weather stability, and low water levels.

Opening the cave entrance under some snow

Having flunked the existing topography, we proceeded to the positioning of the siphon itself. Our underground positioning beacon is water-resistant up to 100m deep (300ft), and our diver went to ask open water to siphon the bottom tag that had been recognized 80m.

With our methodology, we have determined for our client the drilling place place with a good confidence level.

Pre-dive final check with the diver
Diving in a cave closely relates to an EVA in space: the diver is strictly on his own, with his brought oxygen supplies, with no quick return, in the complete darkness and in a ice-cold water (here, 2°C/36°F)
Positioning a cave with radiolocation
This shows both the previous topography (pale colors) and the new, repositioned with reference to the ground surface. It is clear why the previous drilling, based on the speleological topography, was a failure: it was realized 40m from the siphon. Note: data has been slightly modified to comply with confidentiality.

Read more: Continuing the exploration of a flooded gallery

Before one of the dives