Western Express Line recap

A number of posts have appeared in this blog last year on an idea for a Western Express rail line connecting the Main West rail line to the Rozelle Railyards and then to Barangaroo.

This topic has recently come to media attention again, as internal TfNSW documents have come to light confirming that the lines with greatest capacity constraints are the Western rail lines - which the Government's Second Harbour Crossing only indirectly improves.  This post recaps and refines ideas for a Western Express line that adds large amounts of "blue sky" capacity rather than just an incremental improvement, and examines detailed alignment and station location issues.

"Blue Sky" Western Express rail line

For many years, the Rozelle Railyards have been woefully underutilised, despite being a vast (12 hectare) infrastructure asset strategically located in close proximity to the Sydney CBD. Formerly used as a freight corridor, it became disused and then partially converted into a light rail corridor for the Inner West light rail. There have been proposals to use it as a depot for the aborted CBD Metro project and other organisations such as Ecotransit have proposed extending light rail through it under Victoria road into White Bay and then through to Barangaroo. Whilst there certainly is ample room to extend it's light rail function, my fascination with the Rozelle Railyard is the potential it has for connection into Sydney's heavy rail system.

A major flaw of the aborted CBD Metro project was that it was essentially a stand-alone line that did nothing to improve the capacity of Sydney's existing rail system and the CBD Metro would have required extensive and costly additional lines west/northwest before it actually could take passengers anywhere useful. The current light rail line has a role in local transport and connectivity, but is slow, taking 40 minutes to reach Central from the Dulwich Hill terminus due to it's tightly spaced stops and convoluted course through Pyrmont.  

A better use of the Rozelle Railyards would be to use it as a rail corridor that connects the Main West railway line (eg. at Ashfield) to White Bay and then to Barangaroo. The details of the rail corridor alignment are discussed for each section below.  Furthermore, this the Rozelle Railyard corridor is highly suitable for FastRail standards, as it has sufficient corridor width and flat grades needed to allow speeds of up to 200km/h.

Importantly, with the submerged Darling Harbour station option (detailed under Option B in subsection 3 below), the patronage of this corridor is not just limited to the Barangaroo catchment area itself, but also provides a Wynyard “substitute” station via Wynyard walk, and also provides an exit and pedestrian connection to Pyrmont. Effectively, the Option B station serves three catchment areas and not just the Barangaroo catchment alone.

1. Main West Line connection to Rozelle Railyards

Ashfield is one logical connection point. It is only 3.6km away from the western end of the Rozelle Railyards, so would be a relatively short tunnel. The average grades are approximately 2.7-2.9%, making it suitable for a heavy rail tunnel.

The other reason for using Ashfield is that it is a turnback station for inner west line trains. (There is also a carpark adjacent to Ashfield station, should it be necessary to expand turnback facilities further). An alternative to Ashfield would be a longer tunnel to Strathfield. This could allow a potentially higher speed journey as the tunnel could be made less curved and less steep.

2. Rozelle Railyards to Pyrmont

The width of the Rozelle Railyards is approximately 80m. This is more than adequate for the one or more pairs of heavy rail tracks to be added along side the existing light rail track and may even by suitable for fast rail or high speed rail use.

At Victoria road, the Rozelle Railyards narrow to approximately 30m, but the Inner West light rail tracks have branched off at this point and so the whole corridor can be used for heavy rail to pass under Victoria road into White Bay.

At White Bay, a number of alignments are possible. The alignment used by the CBD Metro proposed by the NSW Government in 2009 is shown below. (This corridor is protected under the NSW Infrastructure 2007 SEPP).  Given that Pyrmont is already serviced by light rail, White Bay would be the preferred site of a station, which could be built cost effectively as a surface grade station, or as a cut and cover underground station.  Alternatively, if fast rail speeds of 200km/h are to be achieved, the White Bay station should also be dropped, in which case trains will run express all the way through to the CBD.

3. Pyrmont to Barangaroo

A corridor from Pyrmont to Barangaroo is also protected by the NSW Infrastructure 2007 SEPP. However, unlike the former CBD Metro project, it is proposed that the “Blue Sky” Western Express tracks (in the initial stage) terminate at Barangaroo rather than continue south to Central. This is because most of the benefit derives from direct CBD North access, and it has been outlined previously that Wynyard/Barangaroo is the primary capacity-constrained station catchment, with other CBD stations less constrained. Furthermore, there is substantial incremental cost in tunnelling though CBD environments with complexities of constructing underground stations and avoiding basements, utility infrastructure and pre-existing road and rail tunnels. As a result, the greatest benefit to cost is obtained by terminating the line initially at Barangaroo.

Although two water crossings are necessary on both the west and east side of Pyrmont, both of these are under shallow water, with a water depth of approximately 10m-15m along the corridor. It is probably for the water depth reason that the CBD Metro chose the Pyrmont alignment.

At Barangaroo/Wynyard, a number of station options are possible.

Option A: Station as marked out in NSW Infrastructure 2007 SEPP

The former CBD Metro proposed an underground station below Sussex/Kent St:

Option B: Station under Darling Harbour, connecting Pyrmont Bay Park and King Street Wharf at Barangaroo South.

The advantage of this station is that it can service Barangaroo/Wynyard (the eastern exit of the station being only 100m away from Wynyard Walk) as well as Pyrmont (the western end of the station exit coming out directly in front of the Pyrmont light rail station). Additionally, it provides a pedestrian crossing from Pyrmont to Barangaroo. It also avoids complexity of tunnelling under Barangaroo.

The construction options available are either:

1.  A coffer-dam

2.  Immersed tube: a common dimension (variable length, fixed width and height) immersed tube structure could be built at a dry dock facility and then towed into place. And then finishing work being done with coffer dams.  There are two essential water crossings. A minimum span of 170m near the Anzac Bridge. A span of 320-360m forming the Barangaroo station itself (depending on the angle) and potentially another crossing of Darling Harbour near the Pyrmont Bridge of roughly 270m. Each of these could be lowered into place and then a coffer dam formed around the ends so that construction could be completed at both ends at once. (This process would simplify the need to maintain navigability). 

3.  A triplet of tunnels in ground rock underneath Darling Harbour, with the platform constructed in the middle tunnel.  This would be deeper than an immersed station above ground rock, but could possibly be cheaper to construct.