Tunnelling toward Larrakeyah outfall closure

04 May 2011

A 1 metre wide drill has successfully tunnelled under Daly Street and is now progressing toward Wood Street, installing new sewer pipes.

These new sections of pipe will deliver sewage from the Larrakeyah catchment to the Ludmilla Wastewater Treatment Plant.

Water Services General Manager Steve McKenzie said the process was highly specialised with a drill bit made for this job.

“The tunnelling is computer controlled, boring up to 157m at a time,” he said.

“It is accurate to the design alignment and grade within 25mm.”

Glass-reinforced plastic pipes, highly corrosion-resistant, are being used for the project.

The diversion is part of the project to redirect wastewater discharged into Darwin Harbour into the Ludmilla Wastewater Treatment Plant.

"As sections of the tunnelling works are complete, we will progressively divert sewer flows from Larrakeyah to Ludmilla for treatment," Mr McKenzie said. 

"Depending on tunnelling progress we are hopeful that diversion of flow will start as early as July and will be staged over a period of months to allow for the gradual upgrade of the Ludmilla Wastewater Treatment Plant."

Upgrades at Ludmilla Wastewater Treatment Plant, to cater for the increased flows, will commence this year. 

As well as these upgrades Power and Water is progressing the environmental approvals necessary to extend the existing East Point outfall.