White Bay in Sydney’s inner west and parks on the north shore have been earmarked as potential construction sites for a $14 billion road tunnel project, which will require the disposal of more than 500,000 cubic metres of contaminated sediment.
Leaked government documents marked “Cabinet in confidence” show White Bay has been identified as the main construction site where sediment will be temporarily stored and large concrete tubes built for the Western Harbour Tunnel and Beaches Link.
White Bay is one of more than a dozen potential construction sites for the project, including St Leonards Park at North Sydney, Anzac Park at Cammeray, Flat Rock Baseball Diamond at Naremburn, the Spit Reserve at Mosman and Yurulbin Park at Birchgrove.
Most of the parks will be subject to a high volume of truck movements each day – between 60 and 120 – if they are turned into work sites.
A preliminary environmental study of the project, obtained by the Herald and the ABC, reveals planners fear community opposition to the use of parks, and the disposal of contaminated sediment and soil, could delay construction.
The cost and environmental impacts from handling, re-using or dumping spoil are “expected to be significant” due to the size of the project. Workers will also face a challenge in containing sediment plumes in the harbour during dredging operations.
Among other “key issues” identified in the report are noise and dust from 24-hour work on the tunnelling sites, sleep disturbance for nearby residents, a risk of cracking to “sensitive buildings” and road congestion from the high volume of trucks.
The project also poses a risk to more than 70 threatened species, such as turtles and little penguins.
The 14-kilometre toll road will consist mostly of tunnels that extend from an underground spaghetti junction for WestConnex at Rozelle to Balgowlah in the city’s north.
Under the preferred plan, the use of large pre-fabricated tubes for the tunnel will require the bottom of the harbour between Birchgrove and Waverton to be dredged so they can be laid in a trench.
The report warns that sediment from the harbour bed will contain a raft of contaminants ranging from dioxins to heavy metals and pesticides, a legacy of heavy industry in areas such as Rozelle, Balmain and Birchgrove last century.
About a tenth of the more than 1 million cubic metres of sand, gravel, clay and rock likely to be dredged during construction of the Western Harbour Tunnel is expected to be contaminated.
It is estimated a further 480,000 cubic metres, likely to be excavated at White Bay, will be heavily contaminated. Under the plans, about seven concrete tubes up to 120 metres long will be prefabricated at a casting yard built on about 13 hectares of government-owned land.
The casting yard, including a dry dock, will need to be dug to a significant depth to allow the tubes to be floated out into the harbour before they are laid in a trench between Birchgrove and Waverton. Barges would also transport spoil dredged from the bottom of the harbour to White Bay for temporary storage.
Because the dredged material will have a high water content, a large area will be required to dry it out before it can be loaded onto trucks and transported for disposal.
The most heavily contaminated rock, silt and sand may have to be incinerated or disposed of at landfill sites because “there may be no safe reuse possible”, the report reveals.
The government has long-term plans to develop White Bay and other harbour-front areas at Rozelle, Glebe and Lilyfield into the so-called Bays Precinct.
However, those were set back last year when Google abandoned plans to base its headquarters at a re-purposed White Bay power station.
The leaked report shows it is likely a “significant proportion” of uncontaminated sediment from the inner harbour and Middle Harbour, where a tunnel will run from Northbridge to Seaforth, will need to be dumped at sea.
The cheapest site is Sydney’s “offshore spoil grounds”, about 10 kilometres east-south-east of Sydney Heads at the entrance to the harbour. A permit from the Commonwealth will be needed to dump there.
The high number of tunnelling projects under way in Sydney – such as WestConnex, the NorthConnex road tunnel below Pennant Hills Road in the city’s north, and a new metro train line – means there is strong demand for places such as old quarry sites to dump spoil.
A spokeswoman for Roads Minster Melinda Pavey declined to answer specific questions but said the government was “doing its homework” on the project because the “community wants improved roads and public transport”.
“The project will return local streets to local communities, cut traffic congestion and deliver a new crossing of Sydney Harbour,” she said.
Mrs Pavey said a fortnight ago that a final environmental impact assessment for the new harbour tunnel and Beaches Link would be released in the next few months.
The leaked report comes a week after it emerged the state government plans to use the site of the old Balmain Leagues Club at Rozelle as a major tunnel entrance and work site during construction of the Western Harbour Tunnel. The property is likely to be taken on a 10-year lease, and returned to the owner after the tunnel project is completed.