Jersey Water has conducted a co-ordinated exercise off the headland near the desalination plant to locate the entrance of a 1960s sub-sea tunnel.
Working with Ports of Jersey and the Government’s Infrastructure and Environment Department, the utility used fluorescent green tracing dye and an overhead drone to pinpoint the tunnel entrance, which is some 40 metres offshore.
The tunnel is used to move sea water from the shore to the desalination plant. It was hand-tunnelled by miners in 1969 who intentionally collapsed the entrance on completion. While the tunnel remains in operation, the exact entrance point was previously unknown. Jersey Water needed to locate the entrance to access the tunnel and assess its condition as part of the utility’s longer-term plans to upgrade the desalination plant.
Passers-by may see a temporary patch of green off the shoreline. Jersey Water can assure members of the public that the green dye used in this exercise is biodegradable and does not pose any health or environmental risks.
Mark Manton, Head of Production Operations, said:
“The exercise was successful in locating the precise entrance to the submerged seawater tunnel. It was a great team effort from Jersey Water, Ports of Jersey and the Infrastructure and Environment Department. Being able to assess the condition of the tunnel entry point is a crucial stage for us in developing our designs for increasing the desalination plant’s capacity, to ensure future water resources for the Island.
We used a safe, biodegradable green dye to highlight the tunnel entrance. Using fluorescent dye in this way is common practice in exploratory environmental studies so the public should not be concerned if they see any residual green seawater in the area. It is not in any way harmful to the environment or marine habitat and soon dissipates.“
Ports of Jersey’s Electro-mechanical Team Leader, Darren Roberts, said:
“We were pleased to support this project by going out on one of our RIBs and using our Remotely Operated Vehicle for underwater survey work.”
