The F6 twin tunnels from Arncliffe to Kogarah will be constructed on a new route west of the present corridor, and the southern interchange will swallow sports fields dedicated to Australian servicemen who died at war.
New details were revealed in a scoping report, which said the project could take up to four years, with potential for work taking place 24 hours a day, seven days a week.
Roads and Maritime Services (RMS) submitted the report in an application for the project to be considered as a State Significant Development.
The report said, at present, all through traffic, including freight vehicles, used the Princes Highway and The Grand Parade to travel from southern Sydney to the Sydney CBD.
The volume of through traffic mixed with local traffic, resulted in substantial traffic congestion, particularly during the AM and PM peaks.
This project would relieve traffic congestion on these parallel roads, and provide improved travel times between Kogarah and the greater Sydney region.
Under the proposal, the route of the tunnels – at a depth yet to be determined – would be to the west of the long-reserved F6 corridor.
Tunnelling would take place under Arncliffe Public School, Banksia (between Princes Highway and West Botany Street), Rockdale (west of Ador Avenue Reserve and McCarthy Reserve) and Rockdale Tennis Club before emerging hundreds of metres north of President Avenue, Brighton-Le-Sands.
On-off ramps would be constructed in the Brighton Memorial Fields, adjoining Brighton-Le-Sands Public School, and Bicentennial Park East, within the existing F6 reserved corridor.
The interchange would eat into the Patmore Swamp on the southern side of President Avenue.
Brighton Memorial Fields are on land owned by the Education Department.
A weathered plaque at the entrance says the fields were dedicated in 1968 “to the men of the Australian Armed Forces who gave their lives that youth might live and play upon these fields”.
The report said preliminary environmental investigations and feedback from the community and stakeholders indicated the key environmental issues were traffic and transport, air quality, noise and vibration and biodiversity.
A range of other environmental issues were also covered, including potential for damage to heritage-listed buildings during the tunnelling process.
The report said the alignment of the tunnel was moved west because investigations revealed there were “significant challenges and adverse impacts” associated with either at-grade or viaduct construction with the original route.
Also, geotechnical conditions were not optimal for tunnel construction, the report said.
“It was found that geological conditions improved west of the corridor, and that moving the tunnel alignment would reduce construction risk and the cost of the alignment,” the report said.
The report said the depth of the tunnels would depend on further investigations into the ground conditions between Bay Street and President Avenue.
A speed limit of 80km/h would apply in the tunnels.
The report said tunnel stubs would be built to allow for connections to future stages of the F6 extension.
The report said the location of an exhaust stack at the southern end of the tunnel had not yet been decided, while the ventilation facility being constructed for the New M5 at Arncliffe would also be used for the F6.
The report said President Avenue would be widened between O’Connell Street and Oakdale Avenue to accommodate the southern interchange.
Construction could involve temporary or permanent local road closures, causing impacts to traffic and bus routes.