The optimum, highest value creating HSR entry into Melbourne is from the east via Dandenong along 30km to The Southern Cross Terminus in the CBD. HSR tracks would be in a trench on the north side of the east/west suburban railway, also in a trench, to avoid complications of suburban tracks entering from the south from Cranbourne, Frankston and Brighton. Housing would be built over the trenches.
The HSR tracks would pass through the most southerly platforms 11 and 12 of Flinders Street Station, then around on a new viaduct on the south side of existing Flinders Street viaducts to the western side of Southern Cross Station to the HSR Terminus above Wurundjeri Drive. HSR would continue on through the Terminus to Geelong, and later Adelaide, with loops to Tullamarine and Avalon Airports.
There is a challenging issue at South Yarra Station which needs innovative engineering solutions. HSR tracks must cross over suburban track to the south side in this vicinity. There appear to be three options:
- A tunnel under South Yarra Station from the southeast, under the Yarra River, under Swan Street, under Punt Road for about 3-4km to surface on the south side of the Flinders Street yards into Flinders Street Station. This is practicable, but expensive. There would be some possibility of property value capture to offset the cost at South Yarra Station. There would also be a new short tunnel under Toorak Road for 2 new suburban express train tracks and platforms to the west next to South Yarra Station for extra capacity, to be re-arranged as required. These tracks would bridge over the Yarra River, Swan Street and Punt Road next to existing tracks. They are part of the overall cost of the HSR project.
- A viaduct arising in the cutting to the southeast of South Yarra Station, across the suburban tracks, high above Toorak Road, bridging the Yarra River, bridging Swan Street and Punt Road, to the south side of the Flinders Street yards. The viaduct would descend from a peak of some 30-40m above the existing tracks and 15-20m above Toorak Road to grade level in the yards, with a maximum gradient of 3%. This would mean a viaduct many metres above the existing railway bridge over the river. The short tunnel under Toorak Road and bridging for express trains would also be needed. High rise buildings would be constructed above South Yarra Station to the north next to Toorak Road and over the tracks to the south next to Toorak Road for value capture. There would be much objection to viaducts, especially over Toorak Road and the river. The net cost would be less than tunnelling, but it may not be acceptable.
- A project to lower South Yarra Station by 10-15m would enable HSR to cross over the suburban tracks in the cutting to the southeast and cross under Toorak Road next to the new short tunnel for express trains. HSR would then bridge the Yarra River, bridge Swan Street and Punt Road to the Flinders Street yards to the south next to express and existing bridges. The Station would be lowered stage by stage while operational. Two new tracks and platforms would be cut to the east of the Station and trains switched to the new tracks when completed. The process would be repeated for the other pair of tracks. The new express tracks would then be cut under Toorak Road to the west and the HSR next to them. Extensive high rise buildings to the north and south of Toorak Road would be constructed on foundations prepared when the tracks were being lowered. They would capture value to reduce the net cost, probably less than the viaduct and certainly less than tunnelling. There would be short term disruption, but long term benefit over the next 100 years. It would be an innovative engineering solution and the lowest net cost after extensive value capture.