Underwater service provider Hibbard Inshore has announced it has recently broken the record for the longest distance tunnel inspection performed by a tethered vehicle during work on the Snowy Hydro Scheme in Cooma, Australia.

Hibbard Inshore’s newest long-range vehicle, the SAAB Sabertooth, traveled over 12km in a single direction through the tunnel for a round-trip exceeding 24km, allowing the company to collect real time visual data as well as scan the tunnel with multiple types of multibeam sonar to take high density dimensional data, detect open cracks or holes, detect areas of debris buildup, detect lining failures, and identify rockfalls.

With this information, Hibbard Inshore was able to create 3D models for analysis for maintenance and comparison to future inspection data to identify trends in the condition. The Sabertooth is capable of operating as either a remotely operated vehicle (ROV) with a tether to allow for real-time data and pilot control or as an autonomous underwater vehicle (AUV) to give flexibility in various tunnel inspection scenarios.

Hibbard Inshore has inspected six trans-mountain tunnels across the Snowy Hydro Scheme to date using this method and will return in 2014 for further inspections. Previously, these tunnels needed to be drained for inspection as suitable alternatives did not exist making the task both difficult and risky in terms of potential cave-ins.

"The use of the unmanned sub for tunnel inspections now means that it can be done more frequently, more safely and without the need to shut down power stations or drain the tunnel," commented Chief Operating Officer of Snowy Hydro Ken Lister. "This multi-million dollar investment is a great outcome for the business, for the safety of our people and contractors and is part of our wider program of Scheme upgrades and ongoing maintenance".