The final sector on the Canberra Line is the run into Goulburn, a major regional centre for which access is a priority. The existing line diverges from the Main Southern Line just south of the city, however existing radii are tight at approximately 240m. There are several options for high-speed entry into Goulburn using elements of the existing corridor. Goulburn Station is a grand, two-platformed Federation-style station and is currently part of the Sydney intercity train network. Additionally it is the current site of the XPT fleet’s maintenance facilities, and it is therefore a likely contender for the location of the maintenance facilities for the new high-speed tilting trains.
The total cost of the sector is $79.9m, at an average of $10.9m/km. This is excellent value for a substantially-new sector, and reflects the fact that it follows the gentle gradient of the existing Braidwood Road corridor. Although there are two bridges, the spans are short, keeping the cost-per-metre low. Minimum radius for the sector was increased from 240m to 2000m (possibly slightly higher depending on exact alignment), which allows tilt-trains to travel at up to 290km/h, and non-tilting TGV-style trains to travel at 250km/h.
A faster alignment slightly to the west of the favoured alignment could be considered; it has the advantages of a larger radius curve (3000m), utilising a greater length of existing track on approach to Goulburn (including the section under the Hume Highway, thus negating the need for a new, major grade separation), but it has the disadvantages of requiring a large bridge (about 140m mainspan, meaning it would be at least twice the cost), and passing very close to an historic homestead. Capital cost is likely to be comparable, however in order to minimise the visual disruption of an area of natural and historic beauty, the eastward option will be selected.
Another option considered was an alignment even further west, which achieves a radius of over 5000m. However it would require either a tunnel or a very deep cutting (~40-50m) as well as the demolition of dozens of homes in an historic district of Goulburn. Additionally, it is unlikely that the high speeds obtainable on this alignment would be allowed on the through-tracks of Goulburn Station, due to the proximity of passengers on the platforms. It would essentially require a rebuild of the entire station. For this reason the westernmost alignment is not considered a realistic option.
1 – Deviation start
Section length 1300m, sector start. The line leaves the existing alignment onto a R2000m curve on a low embankment, transferring after about 700m to a moderately deep cutting (12m at its deepest point). The new alignment passes very close to an existing farm shed; it will be assumed that this needs to be demolished and replaced. One farm underpass is required.
- 680m fill, 2.5m high: $539,000
- 620m cut, average 7m deep: $2,556,000
- Track: $2,925,000
- Signalling & Control: $165,000
- Civil works
- 2600m chainlink fence: $130,000
- Drainage: $260,000
- Farm underpass: $500,000
- 40m corridor: 5.2ha @ $10,000/ha = $52,000
- Replacement farm shed: $100,000
2 – Fifth Mulwaree crossing
Section length 1050m, starting at 1300m. The bridge is 550m long, with 27 equal spans of 20m in length (although the riverbed is about 40-50m wide at this point, it is not deep and pylons could easily be built upon it). Also includes two approach embankments (one long and one short).
- Bridge – 550m, mainspan 20m
- Cost function 11725e0.012*20
- Total cost $16,396,000
- 360m fill, 5m high: $561,000
- 140m cut, 4m high: $161,000
- Track: $2,363,000
- Signalling & Control: $133,000
- Civil works
- 1000m chainlink fence: $50,000
- Drainage: $100,000
- 40m corridor: 4.2ha @ $10,000/ha = $42,000
3 – Next to Braidwood Road
Section length 1600m, starting at 2350m. The existing corridor for Braidwood Road runs in an approximate arc, perfect for co-utilisation with a rail alignment! The road reserve will need to be widened to accommodate the railway (assume by 40m). Earthworks are minimal; assume an average 1m-deep cutting along the entire section.
- 1600m cut, 1m deep: $291,000
- Track: $3,600,000
- Signalling & Control: $203,000
- Civil works
- 3200m chainlink fence: $160,000
- Drainage: $320,000
- 40m corridor: 6.4ha @ $10,000/ha = $64,000
4 – Sixth Mulwaree crossing
Section length 1100m, starting at 3950m. The bridge is a single-span segmental concrete bridge of 60m mainspan, similar to the design of the adjacent Thornes Bridge. The bridge is flanked by two approach embankments of about 2.5m in height, and each about 500m in length. One farm underpass and one minor grade separation are required.
- Bridge – 60m, mainspan 60m
- Cost function 19541e0.005*60
- Total cost $3,165,000
- 1040m fill, 2.5m high: $655,000
- Track: $2,475,000
- Signalling & Control: $140,000
- Civil works
- 2200m chainlink fence: $110,000
- Drainage: $220,000
- Farm underpass: $500k
- Minor grade separation: $1.25m
- 40m corridor: 4.4ha @ $10,000/ha = $44,000
5 – Goulburn sidings
Section length 2250m, starting at 5050m. A new underpass must be built under the Hume Highway between the existing Sloane St and Braidwood Road underpasses; this will be assumed to be the equivalent of two major grade separations (one for each carriageway of the highway). Subsequently after about 500m the line joins the Main Southern Line between Sydney and Melbourne, continuing into Goulburn Station. The existing state of the trackbed is good, and it will be assumed that no works will be required on drainage improvements. Goulburn Station will require only minor renovation, but a major park-and-ride facility of 500 parking spaces has been planned to encourage commuting. A possible future development would be to redesign the eastern side of the station (currently taken up by sidings) to allow full-speed transit by very fast trains, as transit between the passenger platforms is unlikely to be allowed at very high speeds.
- Earthworks – excavating the Hume embankment!
- 210m cut, 4m deep: $242,000
- 450m new dual track: $1,013,000
- 1800m dual upgrade: $2,700,000
- 2x high-speed turnouts: $3,000,000
- Signalling & Control
- Cables and balises: $286,000
- Station signals: $8,000,000
- Civil works
- 4500m chainlink fence: $450,000
- 450m Drainage: $90,000
- 2x major grade separations: $10m
- 500m utilities relocation: $288,000
- 500m site clearance: $62,500