Flashback: The construction of Melbourne’s City Loop

The construction of Melbourne’s underground rail system – the City Loop – was an ambitious project that achieved many milestones. It is now an essential cog in the city’s public transport network.In 2014, 222.5 million journeys were taken on Melbourne’s metropolitan train network.

Many of these passenger journeys will have taken place on Melbourne’s underground rail system – the City Loop.

For more than 30 years, the City Loop has been an integral part of the Victorian capital’s public transport network.

Like the soon-to-be-commenced Melbourne Metro Rail Project, it set out to change the face of public transport in the city centre.

The Melbourne Metropolitan Town Panning Commission recommended the construction of an underground city railway as early as 1929. However, it wasn’t until 1969, when the Melbourne Metropolitan Transport Plan was released and supported the need for an underground rail loop, that the concept became a reality.

In February 1971, the Melbourne Underground Rail Loop Act was passed and the Melbourne Underground Rail Loop Authority (MURLA) was set up to build the network.

The proposed railway was an underground extension of the existing suburban rail system. A tunnel section would run under La Trobe and Spring Streets and join up with the tracks alongside Spencer Street Station (now Southern Cross Station) and Flinders Street Station, subsequently forming a loop around the city.

Three new underground stations were included in the ambitious project. These were Parliament, Museum (now Melbourne Central) and Flagstaff stations.

Four separate tunnels, each with an average length of 3.74 kilometres, were to be constructed using different methods of excavation, including a tunnel boring machine (TBM), cut and cover and other mining methods.

On 22 June 1971, after all the preliminary planning was complete, the first sod was turned in the middle of Jolimont Yard, which is now the site of Federation Square.

Tunnelling works underneath the city began in June 1972. The TBM used for some of the excavation work, affectionately known as ‘The Mole’, was built by former engineering firm Jaques Limited. It undertook boring on the Burnley group of lines until September 1977. The remaining tunnels were constructed and progressively brought into service from January 1981 to April 1985.

A new, 722-metre double track precast concrete box girder viaduct was built next to the existing quadruple track Flinders Street Viaduct. This was to replace capacity for non-City Loop trains. Construction began in 1975 and was completed in 1978.

Of the new stations to be brought online, Museum Station was the first. It was built using the cut and cover method with a maximum depth of 29 metres and was operational by January 1981.

Parliament Station, the deepest of the three new stations, was next. The site was excavated at a maximum depth of 40 metres using mining methods and opened in January 1983.

Flagstaff Station was built at a maximum depth of 32 metres through mining methods and brought into service in May 1985. The opening of Flagstaff Station signaled the end of the project’s extensive schedule of works

Roughly 900,000 cubic metres of earth was excavated in the construction process and 300,000 cubic metres of concrete was poured to form the stations and line the tunnel walls.

The total length of the tunnels in the underground loop is 12 kilometres. Ten kilometres of which are circular tunnels, and the remaining two kilometres are box tunnels.

Limited services began on the new network following the completion of Museum station, and an official opening ceremony by then state Transport Minister Robert Maclellan in December 1981. The Melbourne City Loop came into operation progressively as the last stations and tunnels were opened to the public, right up until Flagstaff station was finished in 1985.

The construction of Melbourne’s iconic City Loop network was a lengthy process, but it has provided an essential service for travellers, commuters and locals alike making their way around Victoria’s iconic capital.

Image courtesy of: Public Record Office Victoria’s Railways Photographic Collection

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