Secret architectural designs, seen by the ABC and Fairfax, show the precise location of six polluting smokestacks planned for construction by the New South Wales Government.

The designs, marked "Cabinet-in-Confidence" include a previously undisclosed location for a controversial smokestack in Lilyfield Rd, Rozelle, at the southern end of the giant project.

The smokestacks, as tall as 35 metres, would pump out the exhaust fumes from a six-lane underground tollway, running from Rozelle to the Northern Beaches.

The designs show plans for a smokestack near North Sydney Bowling Club.

Shafts in inner-west, North Shore, Northern Beaches

The precise location of six smokestacks: Lilyfield Road, Rozelle

Lilyfield Road, Rozelle North Sydney Bowling Club

North Sydney Bowling Club Serpentine Crescent, North Balgowlah

Serpentine Crescent, North Balgowlah Judith Street, Seaforth

Judith Street, Seaforth Parkes Road, Artarmon

Parkes Road, Artarmon Ernest Street, North Sydney

Diagrams outline the locations of large ventilation buildings, substations, water tanks, and the final layout of pipes leading to ventilation shafts.

Lilyfield Road is adjacent to Easton Park, and within 800 metres of Rozelle Public School as well as two childcare centres — Rosebud Cottage and Lilyfield Early Learning Centre.

The tollway project was announced by Premier Gladys Berejiklian last May, when she said she was "absolutely committed to building this piece of infrastructure".

A smokestack planned for Ernest Street in North Sydney is detailed in confidential documents seen by the ABC and Fairfax.

The Government has said a detailed proposal is expected next year.

On Thursday Ms Berejiklian told the ABC that: "it is too early to confirm any design details about the project", and she will "expect a detailed proposal by the middle of next year".

Another smokestack would be located at Artarmon.

Local community groups angered

The revelation of Rozelle's smokestack plans is likely to anger local community groups, already concerned about WestConnex.

Local resident and WestConnex opponent Catherine Gammell said locals already object to three smokestacks planned nearby for WestConnex.

She said the "cumulative impacts" of the fourth stack would "be devastating for people in this area".

A smokestack would be constructed at Judith Street in Seaforth.

Ms Gammell believes the Government has kept the community "in the dark" over its highly advanced designs.

"These look like the kind of diagrams you would see in an EIS document. It certainly looks more advanced than the concept design provided by Sydney Motorway Corporation for the M4/M5 link," she said.

Cabinet-in-confidence planning documents also seen by the ABC confirm complex planning to build an extensive "Rozelle Interchange" — where ramps and tunnels will connect the Western Harbour Tunnel tollways to WestConnex and City Westlink.

The documents state data about pollution dispersal around the Rozelle chimney is unknown, and recommend detailed explorations on traffic movements and air quality to model future emissions.

Serpentine Crescent in North Balgowlah.