EDF Energy Hydro-Electric


Project: EDF Energy Hydro-Electric Scheme

Scope: Sonar profiling and leak detection

Location: French Pyrenees Nantilla Tunnel

In September 2009, working in conjunction with Advitam of France on a project for EDF Energy R&D in the French Pyrenees, we installed a long-range hydrophone system for recording low-pressure, high-volume leaks in the 9’ diameter Hydro-Electric plant bulk water transfer tunnel.

The hydrophone, which was the first of its kind, was capable of transmitting the live audio data through 3km of cable. We designed a food-grade dye dispersant system that could be remotely actuated in the vicinity of a leak to enable the path of the leak to be assessed both visually and acoustically.

The hydrophone and dye dispersant system was mounted on a remote manipulator arm positioned on the front of the Pipe Inspection Vehicle (PIV).

The subterranean tunnel access chamber was located at around 3500’ in the Nantilla mountain range and around 4.5 tonne of plant and equipment had to be transported up a steep and winding gravel track to reach the access chamber. The tunnel was accessed via a 60m deep shaft with a 2m x 2m restriction below water level that the PIV had to negotiate before it could enter the tunnel.

The survey successfully located a high-volume leak that significantly exceed expectations on a location that the client had not anticipated, this leak alone created a stream that had run through the local village for many years. The project was a success and we found large leaks in areas where EDF had not anticipated them.

Testimonial: They built a bespoke inspection vehicle for the project to detect and locate high volume, low pressure leaks. Despite the access restrictions, the job was delivered in a timely and professional manner. Tunnel Vision proposed the most innovative solutions to perform the survey using new technologies. We then commissioned Tunnel Vision to survey two cooling pipes at the Blayais Nuclear Power Station to determine the levels of sediment and to assess the condition of the concrete. The two tunnels were 900m long with a 5m diameter and were accessed via the stop-log chambers. The surveys had to be carried out within a limited window of opportunity to meet with the Power Station operational constraints. The Tunnel Vision team were professional, organised and very helpful.

François LOISY Ingénieur Chercheur / Research Engineer, EDF R&D