By Adam Carey
Hundreds of metres of new elevated rail will be built through Melbourne's outer north when the South Morang line is extended to Mernda.
Three rail bridges, including an 800-metre rail bridge over the planned Mernda town centre, and two rail underpasses, will be built.
The eight-kilometre rail extension is due to open in 2019, with two new stations.
A potential third station at Hawkstowe Parade may be built also, with tenderers to be invited to submit a price for what this will cost. There are two short-listed bidders.
An 800-metre rail bridge over the planned Mernda town centre.
Jacinta Allan, the Minister for Public Transport, said the government had listened to the advice of experts in opting for a reference design that mostly favoured bridges over rail trenches.
She rejected the suggestion the rail bridges were another example of a sky rail, saying they would be regulation rail bridges.
"As part of the project, we didn't want to create additional level crossings," Ms Allan said.
"There are five points where we need to address the rail line going over or under roads or creeks along the corridor, and so there are two locations where the road will be going under and there are three locations where the rail will be going over."
Ms Allan gave reporters a different answer when asked three weeks ago if the Mernda extension would be a "sky rail" design, responding with a definitive "No" and saying there was just one point where a bridge would be required.
"There is I think one spot along that eight kilometres where there is a creek and that obviously has to be crossed by the train line and one of the designs proposed there is a rail bridge, consistent with hundreds and hundreds of rail bridges across rivers and creeks and roads across the public transport system," Ms Allan said at the time.
Elevated rail designs to remove level crossings have been controversial for the government, most notably the so-called sky rail through the south-east.
Darren Peters, a spokesman for the South Morang and Mernda Rail Alliance, said the community had been emphatic in stating its preference for rail trenches instead of bridges.
"Everyone was expecting a rail bridge over the creek but certainly at community meetings the public responded unanimously for rail to go under at Hawkstowe Parade and the great majority were for rail to go under at Mernda," Mr Peters said.
He queried if rail bridges were simply the simpler and cheaper option.
"This rail line will still be here in hundreds of years, so we've got to have the best solution."
But he said the rail line was urgently needed, with Plenty Road increasingly congested
Kevin Devlin, the Level Crossing Removal Authority chief, said a mixture of high groundwater levels and hard basalt rock made tunnelling difficult.
Much of the area through which the rail line will be built is reclaimed swampland.
When asked if bridges were a cheaper option, Mr Devlin said: "No, it's a solution that delivers for the government's budget of $600 million."
The former Napthine government also took a promise to extend the rail line to Mernda in the last election, but at a $700 million cost.
The bridges will be five to six metres high.
A new network of bus routes will be put in place to service the new stations, and new bike paths.
The terminus station at Mernda will have 1000 car parking spaces.