It was one of the McGowan Government's key election promises — to build a new outer harbour at Kwinana to take pressure off Fremantle Port and boost Western Australia's freight capacity

And with the Roe 8 highway project now scrapped and congestion still building, industry is pressing for the massive infrastructure project to move full steam ahead.

The City of Kwinana, a key proponent for the outer harbour, is confident private sector funding could easily be found and the environmental impact of its plan for a land-backed port would be limited.

But the Government is not committing to any funding model at this stage.

Transport and Planning Minister Rita Saffioti said she would announce the makeup of a taskforce to plan the outer harbour in the next few months.

Fremantle will remain as a working port with its capacity capped. ( ABC News: Robert Koenig-Luck )

The taskforce will look at how the outer harbour would be financed, the road and rail links, environmental issues and existing capacity at Fremantle Port.

Ms Saffioti estimated it could be up to a decade before the first ships docked at the new outer harbour.

"We've talked about a period between five and 10 years, and I think that's probably realistic," she said.

The Government wants to keep Fremantle as a working port with capacity capped once the outer harbour is built, to reduce trucks on congested roads.

But industry believes the election and the cancellation of Roe 8 has put a new impetus on the outer harbour.

"The election really rammed home the importance of developing the outer harbour, and I hope we can do that in the next couple of years," said economist Cameron Edwards, director at Infranomics, which is analysing predicted trade flows at the outer harbour for the Kwinana Industries Council.

"With the cancellation of Roe 8 and the finite life of Fremantle Port, you have to move the containers down here as soon as you can.

"There's demand for raw materials, both exports and imports, bulk liquids, livestock. There's about 8-10 different modules and they need to be prioritised, as far as what volumes, when and who pays for it."

Kwinana plan to employ 37,000 people

The City of Kwinana's plan for a land-backed outer harbour, which it calls the Indian Ocean Gateway, would be built near the existing Kwinana bulk carrier terminal.

Carol Adams believes it would not be hard to attract funding for the outer harbour. ( ABC News: Nicolas Perpitch )

There would be a bulk carrier terminal and a separate container terminal, with dredging to depths of more than 20 metres to handle the biggest cargo and mining ships.

The City of Kwinana has estimated it would directly employ 37,000 people and generate indirect employment for almost 50,000 more, as well as reducing congestion by diverting trucks from Leach Highway down Rowley or Anketell roads.

Kwinana Mayor Carol Adams said several companies had already approached the council wanting to invest.

"We don't believe funding is going to be an issue given the approaches we have had from numerous bodies," Ms Adams said.

"It really comes down to the philosophical view of the Government, whether it's going to be private ownership, (or) joint ventures."

Seagrass impact 'limited'

In 2015, the City of Kwinana commissioned a preliminary environmental assessment of their proposal.

The report found the project had the potential to harm surrounding seabeds, the subtidal zone, water quality, and marine fauna — but all could be managed to differing degrees.

Ms Adams said there would be very limited impact on seagrasses.

The impact on local seagrasses is not expected to be significant. ( Sanc0067 - NOAA Photo Library (flickr) )

"The area where it's proposed, where it's land backed, is actually denuded of the seagrass," she said.

One of the key campaigners against Roe 8 agrees. Kim Dravnieks, a co-convenor of Rethink The Link, said studies had showed less seagrass in the area proposed for a land-backed port.

"If we can get the freight on to rail, get it out to the harbour, yes there'll be some losses, but we need to manage them really well and put in really good processes on the environmental side so any damage is fixed or lessened," Ms Dravnieks said.

Ms Saffioti said the outer harbour was a priority but more study needed to be done.

"We really want to make sure that as part of wider analysis, we really model the movement of containers, the movement of freight across our network and make sure we get a solution that lasts for Western Australia for the next 100 years," she said.