NZX-listed Genesis Energy may soon start deploying underwater drones to check the 70km of tunnels that form a crucial part of its power generation network. 

Genesis has tunnels around its power stations at Tongariro, Waikaremoana and Tekapo – one measuring 19km, the longest hydro tunnel in the southern hemisphere. 

The tunnels need to be checked every 10 years for safety and performance. 

In the past this has involved draining the tunnels before driving a team through them to take photos in dim light, with complex communication systems to ensure the inspection teams were safe, the company said. 

Accurate tunnel checks for damage and debris can take a power station out of action for up to 13 days. 

Genesis undertook a successful trial of a submersible drone was run in a 3km tunnel in Tongariro, connecting the underground Rangipo Power Station to the Tongariro River. 

The 500kg machine attached to a tether travelled the length of the 4.5m-wide tunnel taking photos and 3D sonar recordings, mapping the tunnel's interior and gathering detailed data. 

The tunnel did not require draining, the machine was remote-controlled from the surface, and the inspection was completed in less than a day. 

Genesis' chief operations officer Rebecca Larking said the successful trial marked a significant step change in the safety of tunnel inspections. 

"This technology will ensure we can complete all our tunnel inspections to a high level of assurance, without creating safety risks associated with being in tunnels for our staff and contractors," she said. 

Larking said reduced inspection time also meant its plants could resume generating electricity sooner. 

Genesis will now work with the drone's operator, Hibbard Inshore, to survey other hydro tunnels around its power schemes. 

– Staff Reporter