Exploration and underwater survey of a flooded gallery deep undersurface

(This mission follows our previous mission surface positioning of a sump)


Our client wanted to realize a drilling in an underground river in a karst environment. The methods previously used had proved unsuccessful.
The underground river (or rather the drain) is accessed by a siphon after more than one kilometer of cave passages at a depth of 380m (1200ft) .

Our work

Having repositioned the existing cave topography and in the light of new underwater-gathered data, we agreed with our client to continue exploring the siphon beyond the known limits for a better estimation of the volume of available water in the reservoir.

The dive was to take place in very cold water 2°C (36°F) to an unknown depth and unknown extent.
Our diver has used a closed-circuit rebreather, which recycles the exhaled air and automatically injects the amount of oxygen consumed. This equipment allows a dive time for more than 4 hours, and strongly reduces the risk of decompression sickness

Fully equipped diver, with CCR rebreather and bail-out tank
Olivier Testa

During several dives several times shortened because of the many difficulties inherent in this environment (cold, extreme humidity causing the failure of electronic equipment, clay omnipresence which clogs the mechanical elements of our devices), we were able to continue exploration siphon for over 200m. This confirmed the quantity of water available, and considerably increased the size of the reservoir capacity and extension..

Start of the dive with an avalanche of mud
Mud covers all the walls of the sump. When immersing, the diver provokes an avalanche of mud leading to a zero visibility during the first 50m of the dive
Olivier Testa

A second series of dives allowed us, by a new protocol with four positioning dives, to position the sump with an accuracy of less than 2 m, for subsequent drilling. Our waterproof radiolocation beacon has perfectly fulfilled its role by continuously operating for more than 48 hours, at a depth of 40m in the icy water.

Exploration and positioning of the underground drain
This map shows in blue the sump explored by our diver, the proposed drilling site, that was later positioned
for confidentiality reasons, data have been slightly altered
NOT Engineers
Pascal Orchampt proceeding to the last tuning of the radiolocation transmitter
The beacon, 100m-proof, prefectly worked during 48h in the icy water
Olivier Testa