At least half the Newcastle-to-Sydney high-speed rail route will run underground, but the man in charge of the project says it can be built by 2037 if the government backs it.
High Speed Rail Authority chief executive Tim Parker told an industry briefing in Newcastle on Tuesday that about 50 to 60 per cent of the 165-kilometre line, or up to 100km, would be in tunnels.
The project would require 12 to 18 tunnel boring machines extracting about 10 million cubic metres of soil which could be used to "revitalise" former mine sites.
Mr Parker's presentation included a map showing tunnels up to 60km long passing under Sydney harbour, Sydney's northern suburbs and most of the rest of the mountain terrain north to the Central Coast, including beneath the Hawkesbury River and Brisbane Water.
The section between Gosford and Newcastle would be largely above ground, including on viaducts and bridges.
"We have done extraordinary bits of tunnelling around Sydney and in Melbourne and in Cross River Rail [in Brisbane," Mr Parker said.
"We're going to test that skill now and look at longer tunnels.
"This will put us up there with some of the European tunnels."
The HSRA is still investigating whether it will tunnel under suburban Newcastle to a likely "anchor station" at Broadmeadow.
Mr Parker told the crowd of several hundred industry delegates that the first construction contracts could be signed in 2027 if the federal government committed funding to the project next year.
He said the build time would be "somewhere between 10 and 12 years".
"If we get an investment decision, we'll want to move very, very quickly," he said.
He confirmed the first stage of Australia's east coast high-speed rail network would operate at speeds exceeding 250km/h, providing travel times of 30 minutes to Gosford, one hour to Sydney's Central Station and, potentially, 70 minutes to Parramatta.
"We see great opportunities to revitalise places like Gosford and Newcastle," Mr Parker said.
"They're already vibrant centres, but, wow, they could really be supercharged by this type of investment."
The HSRA is aiming for travel times of 90 minutes from Sydney to Canberra and four hours from Sydney to Brisbane and Melbourne once the rest of the 1700km network is finished in the coming decades.
The authority has started test-drilling at 27 locations under the Newcastle-Sydney route while working on a final business case to be handed to the government by the end of this year.
The Newcastle-Sydney line would have about 20 train sets with eight cars per train offering high-speed wi-fi, food and drink sales, luggage storage, pet-friendly areas and optional "premium service".
"What we expect to provide is a really good experience," Mr Parker said.
"It's a different type of product ... something that the country's ready for."
HSRA executive general manager Steve Joseph said the authority wanted to acquire "off the shelf" rolling stock with a proven track record and requiring minimal modification.
He said the HSRA would look to develop a domestic manufacturing industry to make products for the high-speed network and other rail projects across Australia.
Mr Parker, the former head of project delivery at Sydney Metro, said a 2027 start date would dovetail with the end of large underground rail projects in Sydney, Melbourne and Brisbane.
"Whilst there's a little bit of scepticism, there's also some genuine excitement, 'Let's get this going. We've got the skills in this country to do this type of project now. Let's make it happen,'" he said.
He said a rail manufacturing and maintenance industry in the Hunter could help offset the decline in mining work.
The HSRA met with Hunter local government representatives last week and is seeking Australian and international industry feedback on how to build and operate the line.
HSRA chair Jill Rossouw said national population growth, changing settlement patterns on the east coast, work-from-home arrangements and pollution goals "create the right environment for high-speed rail now".
She said high-speed trains would give people more choice in where they lived and worked while improving access to services.
"The shift to rail, including high-speed rail globally, seems unstoppable," she said.
"Around the world there are 70,000km of high-speed rail in operation and around 30,000km under construction."
Ms Rossouw said projects "of this scale and complexity do not come around very often".
"East coast high-speed rail is a long-game project that in its entirety would be delivered over multiple decades," she said.
"Its course will be shaped by the planning that we do now for the Newcastle to Sydney section."
The briefing attracted a host major international rail, infrastructure and design contractors, including Japan Railways, Siemens, Alstom, Hitachi, CPB and John Holland.
The government has committed $500 million to planning and preserving a high-speed rail corridor between Sydney and Newcastle and has asked the HSRA to produce a final business case by the end of the year.
"In Australia, we have seen a massive investment in rail infrastructure over the past decade, around $100 billion," Ms Roussow said.
"This has created an engineering and construction skills base that brings world-class construction techniques and also a workforce and a sector that is looking for certainty and ongoing opportunities."
The NSW government revealed last year that Sydney's 24km Metro West underground line, which has nine stations, would cost $25 billion.
