It was scheduled for completion on 30 September 2022,[4] although delays related to disposal of contaminated soil have pushed back its opening until at least 2025[1] and its cost may be as high as $11.9 billion.

The final plan is for eastbound traffic using the Western Distributor to exit the West Gate Freeway via a tunnel portal near Williamstown Road.

It said rapid traffic and population growth suggested the need for both corridors in the long term, but identified the southern route as the one that would produce benefits earlier and greater over time than the northern one.

Pathway 1 (the southern route) addresses current needs ... it would also permit enhanced planning for the northern corridor in a more considered timeframe to optimise land use in the west and provide certainty to industry and residents.

[39] Traffic projections in the EES for the tunnel and road link revised patronage levels from those contained in the business case, with a significant increase in truck estimates.

[48] The council's submission was harshly critical of the EES, describing it as fundamentally flawed because it failed to investigate and document relevant alternatives for the project.

The IAC said the project was likely to impose significant constraints on the urban renewal area at E-Gate in West Melbourne, primarily through the elevated Wurundjeri Way extension and said a "demonstrably superior outcome" should be possible.

It said the project should aim to contribute to improvements in air quality and recommended that pollution control equipment be installed on the tunnel ventilation system.

"[56] The Minister for Planning, Richard Wynne released an Assessment Report of the West Gate Tunnel Project, concluding the Environment Effects Statement process, on 27 November 2017.

[64] In June 2021 the Victorian Ombudsman confirmed she was pursuing complaints about the study, with the state government refusing to release a final report from the process.

The longer tunnel was expected to take about 18 months to bore, with 1.5 million cubic metres of rock and soil needing disposal at landfill sites.

[70][71][72] The presence of contaminated soil from past industrial use in the project area and its impact was raised during the EES hearings and final Inquiry and Advisory Committee report.

[73][74] In mid-2019 the joint venture responsible for building the project—CPB Contractors and John Holland—reportedly sent Transurban a letter of intent, claiming they were confronted with a force majeure event, an unforeseeable circumstance that made it impossible to fulfil the terms of their contract, because of difficulties in disposing of soil contaminated with PFAS.

[78] Transport Infrastructure Minister Jacinta Allan said the companies needed to resolve the situation without government involvement and said the presence of contaminated soil was known before the contract was signed.

[71] As the dispute continued, John Holland chief executive Joe Barr warned the construction industry was "teetering on the edge of collapse" because major contractors were not making money.

[81] Relationships between the contract partners descended to a new low in June 2020 when Transurban sought a Supreme Court injunction to stop what it claimed was a premature attempt by the tunnel builders to start arbitration over contaminated soil.

[82] Concerns over the possible disposal site of the contaminated soil sparked protests in Bacchus Marsh[83] and Werribee[84] in early 2020 but industry sources claimed much technical and planning work would be required before dump locations were finalised and it might be six months before they could receive waste.

[90] All three were ultimately approved by the Planning Minister in March and April 2021 and the Hi-Quality site was selected by the project managers in June 2021 to accept the contaminated soil.

[93] Transurban conceded in February 2021 that difficulties in securing soil disposal sites as well as lags in approvals and preparatory works meant a 2023 completion date for the project was no longer achievable.

[94] The state government eventually reached a deal in December 2021 with builders to end the construction stand-off, saying the deal would see Transurban contribute an extra $2.2 billion towards costs, while CPB John Holland would give up all of its profit margin and make significant losses, but would cost Victorian taxpayers an extra $1.9 billion and has further delayed the completion date into 2025.

[1] After a damning report by the Victorian Ombudsman in May 2022, the Environment Protection Authority acknowledged it had failed to engage in a meaningful way with the community during the process of selecting a site for contaminated tunnel spoil.

[96] In August 2020 it was revealed about 460 of the concrete components, weighing up to 160 tonnes, would be too big for the railway tracks and would instead need to be trucked to Melbourne via 52-metre long, five-metre high "superload" freight vehicles travelling at 25 km/h.

Residents in towns on the route, including Longwood and Locksley complained after they were warned to expect as many as five loads a week for two years, travelling at night.

[99] A report by the Victorian Auditor-General's Office on the operation of market-led proposals tabled in November 2019[12] criticised the West Gate Tunnel project, which at that time it valued at $6.7 billion,[100] concluding the government had approved the new tunnel without sufficient proof that Transurban's market-led proposal demonstrated value for money and "unique qualities".

The report said Treasury Department officials failed to warn the government that extending CityLink tolling could "create an unintended monopoly advantage for Transurban".

It said Treasury officials also failed to properly consider a range of alternative project options, or other ways–apart from extending Transurban's tolling on CityLink–to pay for the new road.

"The business case was not sufficiently comprehensive and so undermined one of its key purposes–to provide confidence to decision-makers that they are selecting the right investment option," the audit said.

The report said including the Monash Freeway upgrade "lacked a convincing rationale" and coupled with a series of other abnormal additions might have inflated the project's benefits on paper.

[106] Maribyrnong City Council voted in July 2019 to advocate for truck bans on Williamstown Road and urged the state government to begin design and development of an alternative north–south freight route outside of residential areas.

It claimed the project could hinder public transport usage and accessibility and also asserted that it would do nothing to improve the east–west capacity of the M1 corridor because the "pinch point" of the CityLink tunnels would remain its main determinant.