It’s a job that requires focus, preparation – and an ability to endure claustrophobic conditions.

Once every three years, a team of hard-hatted specialists negotiate their way through a cramped, 2.5 kilometre-long tunnel located deep underground, in order to evaluate the integrity of one of the Sunshine Coast’s most important bulk water pipelines.

The pipeline, which was built in the late 1980s, allows raw water from Baroon Pocket Dam’s storage to travel through the Blackall Range to the Landers Shute Water Treatment Plant in Palmwoods.

Seqwater Asset Engineer Daniel Roche said the triennial inspection was a necessary step in ensuring water supply security on the Sunshine Coast.

Mr Roche said the inspection was undertaken by a small team of specialists including geotechnical and civil engineers.

“During these inspections we are not only looking at the condition of the pipeline but also the rock walling of the tunnel,” Mr Roche said.

“The tunnel was excavated through sandstone by drill and blast techniques. It runs a straight line between the base of the intake tower and the exit portal.

“The tunnel is about 2.6 metres high and 2.5 metres wide and gets pitch black after 50 metres or so inside, so you have to be comfortable with confined spaces.

Mr Roche said if there were any concerns with the condition of the tunnel or pipeline, a renewal program would be launched to resolve those issues.

“Advances in technology have made it easier to detect potential issues and solve them before they have much of an impact,” Mr Roche said.

“For example, we can now use laser scanning to create a 3D model of the tunnel which helps us identify and record any cracks appearing in the tunnel that might not have been there before or movement within the rock.

“This pipeline is not only important for the Sunshine Coast; it’s also a critical component in South East Queensland’s Water Grid.

“In order to maintain this critical link, it’s vital that inspections and repairs can be undertaken on the pipeline and that the tunnel is a safe environment to access and work in.

Baroon Pocket Dam, built across Obi Obi Creek, was completed in 1989 and is 370 metres long. At full capacity the dam storage holds 61,000 megalitres of water and is the main water storage for the Sunshine Coast.