A number of significant changes were made to the Johnsonville line to allow more modern trains to run. In time, this work means Johnsonville commuters will be able to enjoy the new Matangi trains.
All seven tunnels on the line have been made larger, by lowering the level of the track and widening the sides of the tunnels, which will enable the new and bigger trains to run. Clearances under two bridges have also been adjusted.
The three crossing loops have been lengthened and platforms extended, which will allow longer trains to run.
Rebuilding a railway line is difficult because the trains cannot be diverted to another route. The line has to be closed some of the time while work is carried out. To cause the least disruption it is better to do that at night or during quiet holiday periods.
From the end of December 2008 to early February 2009 buses replaced trains on the Johnsonville line so the tunnels could be upgraded. Advantage was taken of the line closure to complete maintenance and renewals work at the same time.
CONSTRUCTION TIMELINE September - December 2008
Tunnel walls strengthened in readiness for the floors to be lowered. Two access roads formed at Trellisick Park and Kaiwharawhara Rd and a retaining wall built at the south end of the Wadestown crossing loop. Maintenance and renewal work.
LINE CLOSURE 28 December 2008 - 7 February 2009
Rail and ballast removed from all 7 tunnels before the rock floor was dug out, lowered and the ballast and rail re-laid. Ngaio Gorge rail bridge lowered and the level of the track lowered under the Raroa St footbridge. Extension of three crossing loops. Upgrade and extension of three platforms. Re-lay surface of the Fraser Avenue and Simla Crescent level crossings.
During 2009 and 2010 - Extension and upgrade of remaining station platforms Upgrade of overhead power lines. Installation of new substation at Ngaio Station.