Repairs are underway after a pipe containing raw human sewage burst about 60 metres beneath the Brisbane River.
Urban Utilities said all human waste was contained within an underground tunnel and none of the untreated effluent had leaked into the river itself.
The company said wastewater services would continue as normal, but it would need to replace a 600-metre stretch of two underground pipes.
The temporary bypass will allow workers to replace the two damaged pipelines. (Supplied: Urban Utilities)
Next week the company will start building a kilometre-long temporary pipe to funnel the waste, allowing workers to enter the tunnel and replace the old pipes.
The Bulimba-Hamilton siphon carries around 150,000 people's waste from the south side of Brisbane to the Luggage Point Resource Recovery Centre for treatment.
Paul Arnold says the siphon was an under-appreciated piece of Brisbane's infrastructure. (ABC Radio Brisbane: Kenji Sato)
Urban Utilities chief executive Paul Arnold said he expected the temporary pipe to be up and running by early next year.
"The siphon is … perhaps the city's most important but hidden piece of infrastructure," Mr Arnold said.
"It's been in place for the last 70 years and has served us well, but it's reached the end of its service life.
"It's now important for us to take the opportunity for us to renew it so it can continue to support the people of Brisbane for the next 70 to 100 years."
While major works continue, certain sections of the Brisbane River will be sectioned off with buoys and speed limits will apply for boats.
The area around the barge will be sectioned off to other boats. (Supplied: Urban Utilities)
The work will be done from a barge which will start near the Bretts Wharf Ferry Terminal at Hamilton and then move diagonally across the river to Bulimba over the coming months.
Mr Arnold said if everything went to plan, there should be no major disruptions to Brisbane's ferry services.
He said the company was working with RiverCity Ferries, Maritime Safety Queensland, and Brisbane City Council to minimise disruption to river users.
Scuba divers will be deployed to oversee pipe laying.
Specialist divers will be dispatched for underwater works. (Supplied: Urban Utilities)
Urban Utilities spokesperson Michelle Cull said one of the two pipes burst on January 16 this year when workers were attempting to replace the second pipe, which was offline.
Ms Cull said once the temporary pipeline was connected, workers would fix the breakage so that both pipes could be removed and replaced.
Lucy Collier says this is a critical project. (ABC Radio Brisbane: Kenji Sato)
She said the company currently did not know when the two pipes would be up and running again.
"At this stage, we're unable to provide a time frame for when the project will be completed as we first need to assess the pipes, tunnel, and complexity of repairs once we can safely access the tunnel," Ms Cull said.
Brisbane City Council Morningside Ward Councillor Lucy Collier said this was a crucial upgrade for the growing city.
"One of the most important issues that people raise with me as a local representative is ensuring that infrastructure keeps up pace with growth in our community," Cr Collier said.
"I support the provision of new and improved essential infrastructure, like the Bulimba-Hamilton siphon project."