The State Opposition says it would do all it can to prevent the closure of Riverside Drive if it wins the state election.
He has promised to try and renegotiate some of the contracts already in place if he wins next month's state election.
"I would love to see Riverside Drive and those roads stay open," he said.
"It's a matter of what you can do. We know that contracts have been signed, we also know, as has happened from time immemorial, that there can be renegotiation of those."
Mr McGowan says any savings would go towards parking at hospitals.
The Premier Colin Barnett has criticised the proposal.
"It wouldn't be an Elizabeth Quay, it just wouldn't meet the concept," he said.
"The whole idea is opening up the river and the city together, so actually having a wide expanse of water.
"If you left Riverside Drive there, what you would have would be a pond in the city.
"Not much point in that."
Mr Barnett says changing the contracts would be expensive and keeping Riverside Drive would fundamentally change the development.
He says Mr McGowan is yet to clearly outline his position on the overall project.