Hunter Water has worked since February to replace a 300-metre stretch of the Chichester trunk gravity main beneath the Hunter River at Osterley, with the project completed in the first week of October. 

The original main, which stretches for 90-kilometres and links Chichester Dam with Newcastle, was completed 91 years ago.

This included the Hunter River Tunnel, a 200-metre long section used to maintain the pipes which ran under the Hunter River from Osterley to Duckenfield.

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While the main has been upgraded over the years, the Hunter River Tunnel deteriorated to the point where it was no longer safe for employees to access to make any future repairs to the pipes.

Hunter Water laid two new pipelines beneath the river to bypass the historic tunnel and connect the existing pipework on either side, in a project worth $8m. 

The new pipes were laid using a method called horizontal directional drilling, saving the need for any new tunnel or trenching.

A Hunter Water spokesperson said the crossover between pipes went smoothly with minimal disruption to services. 

“The upshot is that it’s providing a more reliable water supply to homes across the Hunter,” the spokesperson said.

“You don’t want a situation where employees have to access an unsafe tunnel to do repairs on the main.”