Brisbane City Council's $1.7 billion Northern Link tunnel has received state government approval, paving the way for work to begin later this year.

The two parallel twin-lane tunnels will run underground from the Toowong roundabout, connecting the Western Freeway to the Inner City Bypass.

Construction is set to start in December and, when completed, will be Brisbane's third toll tunnel, after the Clem7 and Airport Link.

Infrastructure Minister Stirling Hinchliffe said 34 conditions had been imposed on the project by Co-ordinator General Colin Jensen after 28 months of evaluation.

"The Northern Link road tunnel is obviously a major piece of infrastructure that will have a positive impact on improving traffic flows in Brisbane, " Mr Hinchliffe said.

"Its construction will need to be managed carefully to minimise any adverse impacts on local residents and the environment."

Mr Hinchliffe said the Coordinator-General and the Department of Infrastructure and Planning spent 28 months thoroughly assessing the council's environmental impact statement and associated materials.

Mr Jensen said the conditions in the evaluation report were the most extensive and stringent ever for a transport infrastructure project in Queensland.

He said the conditions included issues which had been raised with Clem7 and the Airport Link tunnels.

Those included air quality issues and the excavation of rock from the tunnel.

Mr Jensen said conditions governing air emissions from the ventilation outlets would be covered directly by an environmental authority set by the Department of Environment and Resource Management.

"Another major concern raised in the submissions was the air quality levels from the two ventilation outlets. One is proposed at each end of the tunnel," he said.

"During construction, rock excavated from the tunnels will be transported to Mt Coot-tha Quarry by a conveyor belt.

"Any changes to the conveyor route proposed recently by council will be subject to further separate assessment once council has completed its tender process.

"Conditions governing air emissions from the ventilation outlets will be covered directly by an environmental authority set by the Department of Environment and Resource Management."

The Federal Government has chipped in $500 million to the $1.7 billion project, which is projected to provide 1400 jobs during construction and 85 jobs when it is running in 2014.

Council's opposition leader Shayne Sutton yesterday questioned the financial implications on Brisbane ratepayers of the project.