The NSW Government has been warned of a "huge fight' by "frightened" North Sydney residents over a plan to build ventilation shafts near schools, homes and parks in the area.
The smokestacks would pump out the exhaust fumes from a planned six-lane underground tollway, running from Rozelle to the Northern Beaches.
Secret architectural designs, marked Cabinet-in-confidence, and seen by the ABC and Fairfax Media, show plans for a smokestack and ventilation building near North Sydney Bowling Club.
Mayor Jilly Gibson joined about 250 locals on Thursday night to grill officials from the Roads and Maritime Service (RMS) about the precise location of the smokestacks.
"We want to know exactly where the stacks are going to go," she said.
James Hay, program director of the Western Harbour Tunnel and Beaches Link project, told the meeting it was still in the concept design stage.
"The exact location of the tunnel ventilation facilities has not yet been determined," he said.
RMS air quality expert Andrew Mattes said the air typically went hundreds of metres up into the atmosphere before it stopped rising.
"So the emissions from the tunnel, they dilute and they disperse typically up to a thousand times before they reach down to ground level," he said.
"Even under the worst-case conditions when they mix down quite quickly they dilute at least a hundred times."
'This will not go unchallenged'
However, residents at the meeting remained unconvinced.
"When you look at your own sensitivity buffers of 500 metres, that puts in total in the North Sydney LGA approximately 7,000 children in those sensitivity buffers in early primary, secondary schools," resident Allen Furnas said.
"What they said is ... 'this will be a problem, but you know, it's liveable', so what if seven or ten thousand kids have more pollution?"
Cr Gibson said there was a "simmering mood" in the room and residents were "frightened".
"They will not let this go unchallenged and there will be a huge fight," she said.
The Mayor cast doubt on the value of the briefing, saying she had been left in the dark since the project was announced in May.
"I don't believe those questions were adequately answered, I think there's a lot of extra information that could be given and simply isn't being given, it's not good enough," Ms Gibson said.
Former Mayor of North Sydney, Genia McCaffery, also voiced concern over the process.
"Two proposed construction sites are going to be in parkland at Waverton and yet two weeks ago we heard nothing when we were being briefed," she said.
"They're drip feeding the community little portions of information.
"The community is getting very angry and the more they pretend to consult with us the angrier we will get."
