The new M5 tunnel from Kingsgrove to St Peters is expected to improve air quality slightly in some areas and increase pollution by a small amount in other areas.
This is stated in an environmental impact statement (EIS) for the project, which went on public display on Friday.
"Overall the project has little net impact on air quality; however, there is a small redistribution in pollutant concentrations as a result of changes in the traffic volumes and hence emissions on the surface road network!" the EIS said.
"Emissions from the tunnel ventilation outlets have little impact on air quality outcomes."
The document said the project was expected to result in a redistribution of impacts associated with vehicle emissions.
"This will result in a small improvement (or decreased concentrations and health impacts for some areas, and a small increase in pollutant concentration in other areas'," it said.
"Potential health impacts associated with changes in air quality (specifically nitrogen dioxide and particulates) are low and essentially negligible."
The EIS said the project would result in increased traffic along King Georges Road to the south of the M5 East Motorway, Stoney Creek Road, Bexley Road to the south of the M5 East Motorway, Harrow Road, Bay Street, Forest Road, and around the southern perimeter of Sydney Park.
It said there would be decreased traffic and pollutant concentrations along the M5 East Motorway, both to the east and west of the M5 East tunnel and General Holmes Drive.
The EIS said the ventilation system had been designed and would be operated to achieve stringent in-tunnel air quality criteria.
The project design elements to reduce pollutant emissions within the tunnel would include minimal gradients, and the ventilation system would be automatically controlled using real-time traffic data covering both traffic mix and speed, and feedback from air quality sensors in the tunnel, to ensure in-tunnel conditions were managed effectively in accordance with the agreed criteria.
"The design of the ventilation system will ensure zero portal emissions," the document said. "The ventilation outlets will be effective at maintaining local air quality.
"Ambient air quality monitoring will be conducted pre-and post-operation to demonstrate that emissions from the ventilation outlets will have no detectable impact on local air quality."
Full report and reaction in the Leader next week.
Do you accept the EIS findings?
