• Terratec

Contaminated soil delays Melbourne West Gate TBMs 23 Apr 2020

Jonathan Rowland, TunnelTalk

Two 15.6m diameter Herrenknecht TBMs procured by the CPB Contractors-John Holland JV to excavate the twin tubes of the West Gate highway in Melbourne are assembled but lying idle following issues with the management of contaminated soil. The ground through which the TBMs will bore is contaminated with carcinogenic chemicals known as per- and polyfluorinated alkyl substances, PFAS. The first machine was due to begin excavation on the 4km long tube in mid-2019 after arriving in Melbourne from the Herrenknnecht factory in China in March. The cutterhead, as the last assembly component of the first TBM was reported as lifted into the Footscray launch shaft in August 2019. The second mega TBM arrived in March 2019 for the second 2.6km twin tube but tunnelling by either is yet to begin (Fig 2).

Contaminated ground holds up West Gate TBMs
Contaminated ground holds up West Gate TBMs

PFAS have been used for decades in a range of non-stick, water- and fire-repellent and stain resistant products. Recently, the health implications of PFAS exposure have raised concern, as the chemicals resist physical, chemical and biological degradation and are readily leached into groundwater from where they may enter the food chain.

“Historically, PFAS was an unregulated contaminant and was considered fill material,” said Scott Carlton, Chief Executive of Transurban, the client organisation developing the project under a public private partnership with the State Government of Victoria. In a conference call in February with financial analysts he explained that that arrangement has been evolving over the last few years with the result that a spoil management plan for the project is now required by the State EPA, Environmental Protection Authority. “Everyone has been aware of the issue for a long period of time,” said Carlton. “It was discussed in the environment effects statement, EES, and the way the EPA is looking to manage it has been evolving.”

The West Gate Tunnel Project EES was prepared for Transurban by AECOM and geotechnical assessment was undertaken by Golder Associates with GHD engaged as the technical advisor to the State on the project. The Aurecon-Jacobs JV is the design engineering is undertaken for the CPB-John Holland JV (CPBJH).

Fig 1. Route of the new West Gate highway
Fig 1. Route of the new West Gate highway

The EPA did not respond to requests for comment for the article but in its submission to the 2017 EES, the EPA had warned that PFAS have recently been the “focus of health and environmental investigations” and subject to “increased environmental regulatory focus”. It also noted that there were “limited options available in Victoria for managing or disposing of PFAS-impacted waste”. In 2019, the EPA updated its regulatory stance on PFAS in an interim position statement, following the publication of a national environmental management plan (NEMP) for PFAS in Australia in 2018. Preparation of an NEMP update is underway.

The challenge is to find a disposal site that can take the PFAS-contaminated muck and in the quantity and at the speed with which it will be produced. “We have been working with the contractor, the EPA and the State to try and find a solution,” said Charlton, but “at the moment, there is no site capable of taking the spoil”.

As a result of the issues, Transurban said in January 2020 that it had received documentation from the CPBJH that purported to terminate its contract as it relates to “issues in respect of the presence, classification and disposal of PFAS within the project site”, with the JV agreeing to continue to work on other aspects of its West Gate project contract.

Fig 2. New highway comprises two tubes of 2.8km and 4km long
Fig 2. New highway comprises two tubes of 2.8km and 4km long

CPBJH declined to comment for the article and the contract appears to remain in place, despite the January notification. In an emailed statement to TunnelTalk, Transurban said that, although details of contractual discussion were “a matter for the project parties”, CPBJH was now “working to finalise plans to tunnelling and secure sites for the safe management of tunnel soil”. That process was said to be still underway and that “no decisions have been made”.

This was confirmed by the Major Transport Infrastructure Authority of the State Government, which said in a statement that a tender process to source an appropriate site for disposal of the PFAS-contaminated spoil was currently being carried out by the project partners. Meanwhile, construction has been continuing at the portal locations with tunnel excavation to start as soon as a long-term sustainable solution to the disposal of the spoil is finalised. The TBMs have been assembled and are on standby to be ready to start once a solution is found.

Northbound portal at junction with the M1 highway
Northbound portal at junction with the M1 highway

Sites bidding to provide the disposal facility would need to seek relevant planning and EPA approvals, which will set the limit of PFAS that can be stored safely, Transurban said in an early April update. “As it stands, we are currently reviewing the project,” said Charlton in the February analysts call. “The contractor has informed us that the project is unlikely to be completed by the end of 2022 due date. We are working closely with our project partners to implement opportunities that would enable us to deliver the project on time.”

Construction is ongoing on other elements of the project, including the widening of the surface highway, the construction of a bridge over the Maribyrnong River and new connections to the city and to the CityLink highway to the south east of the Melbourne city centre (Fig 1). To date, about AUD$2 billion has been spent on the project.

Transurban is also involved in the development of the NorthConnex and WestConnex highway projects in Sydney, both of which include significant underground works. In addition to the problems with the West Gate project, Transurban is facing economic pressure from the current COVID-19 pandemic which has seen traffic on the company operated toll roads in Melbourne, Sydney, Brisbane and North America fall dramatically. As a result, the stockmarket-listed company has withdrawn its second-half dividend guidance.

References

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