The line winds between hills, road and river in the picturesque Lake Bathurst valley, with the minimum radius of 800m of the first few curves unfortunately not quite meeting our requirements. Despite being wedged between highway and hillside, most of the curves do not turn through a very great angle, so the deviation required to increase radius is small. In some cases it can be achieved within the existing road and rail reserve. The curves coming into Lake Bathurst are approximately 1500m in radius already, so these will require only minor adjustment.

Despite following the existing alignment closely, due to the fact that the curves will have to be rebuilt to HSR superelevation standards it will be assumed that the track will be replaced entirely by new.

Alignment design

Lake Bathurst plan – click to enlarge

Summary

The total sector cost is $59.0m, averaging $7.5m/km. This is relatively high for a sector with mainly re-used alignment, due to the decision to include a new station at the small community of Lake Bathurst. Although not economically justifiable at present, this has been done with an eye to the town’s future development potential with the arrival of the fast railway. Removing the station-related costs ($1.4m of turnouts, $8m of signalling and $5m for the station itself) would save about a quarter of the total sector cost.

The minimum radius has been raised from 800m to 1500m. Alternative, faster alignments were also considered. The first involves a modest increase in radius (to about 2000m) with a small increase in earthwork cost, and a requirement to re-route part of the highway. A 3000m radius curve (allowing TGV-style trains to travel at 300km/h) is possible, but only with an entirely new alignment on the other side of the Mulwaree river, which involves substantial lengths of bridge structure. Even at a low estimate of $15m/track-km for these bridges, it would still be perhaps $80-100m worth of bridges alone. This is a very large extra cost for a service speed which is not currently in prospect, therefore the baseline 1500m radius option was selected for this sector.

[table]
Component,Cost ($m),Percentage
Tunnels,0.0,0.0%
Bridges,2.1,3.5%
Earthworks,9.0,15.3%
Track,20.6,34.8%
S&C,17.0,28.8%
Civil works,4.8,8.2%
Stations,5.0,8.5%
Land,0.6,0.9%
TOTAL,59.0,100.0%
[/table]

Tarago exit

Section length 1780m, sector start. An R1500m curve is initiated as the alignment leaves the station precinct, necessitating a fairly deep cut into the hillside (about 850m in length and 16m maximum depth). Rejoins the existing alignment following the curve. Farm underpass required within Tarago. Switches and associated signalling required at Tarago Station.

• Earthworks
  • 850m long cut, avg. depth 10m
    • 187,000m3, $5,797,000
  • Elsewhere (930m) – fill widening, height 2m
    • 11,160m3, $179,000
• Track
  • New dual: $4,005,000
  • 2x low-speed turnouts: $1,400,000
• Signalling and Control
  • Including crossover signals: $8,226,000
• Civil works
  • 500m security fencing: $100,000
  • 1280m chainlink fencing: $128,000
  • Drainage: $356,000
  • Farm underpass: $500,000
• Land: 60wide, 1km corridor for deviation
  • 6ha @$10k/ha = $60,000

Braidwood Road deviation

Section length 1420m, starting at 1780m. A second curve of R800m must be straightened in this section. Unfortunately there is a farmhouse or shed right at the apex of the curve. While it may be possible (just) to squeeze the line in behind it, it is probably prudent to assume this building must be demolished and the entire property acquired. Toward the end of the section, the alignment begins another 1500m radius curve with very little distance for transition. According toour geometry constraints, a reverse curve transition (ie, curved to straight back to curved in the other direction) should exceed 300m in length. This should be able to be achieved here, but it may require a deeper cut toward the end of this section.

• Earthworks
  • Balanced cut-fill, whole length, depth 4m
    • 90,880m3, $1,363,000
• Track: $3,195,000
• S&C: $180,000
• Civil works
  • Chainlink fence: $142,000
  • Drainage: $284,000
• Land: Conservatively assume $500,000 to acquire entire farm (area between rail and road reserve is about 29ha, which would come to $290k if land were priced at $10,000/ha).

Lake Bathurst approach

Section length 4690m, starting at 3200m. The remainder of the sector follows the existing alignment very closely; no land acquisition is required. A fairly well-balanced cut/fill widening is required along the whole length. It will require one farm underpass, a minor grade-separation at Coven Creek Road, and a replacement of the Bongaralaby Creek Bridge. The existing bridge is 40m long with 3 equal spans; assume 3 spans of 20m. Lake Bathurst is a township that has potential for development; many empty subdivisions exist there already. Therefore it is sensible to include a station. The old station buildings from Lake Bathurst Halt no longer exist, so an entirely new one would have to be built. It would be a very small station, unstaffed and possibly stops by request only. Assume build cost $5m in addition to usual station signalling and trackwork.

• Bridge: Bongaralaby Creek
  • 3 spans of 20m; cost function 11725e^0.012*20
  • Multiplier 1.15 for triple-span; total cost $2,057,000
• Earthworks
  • Balanced widening, approx 4m avg depth.
    • 112,560m3, $1,688,000
• Track: $11,953,000
• Signalling
  • Station signals and cable: $8,596,000
• Civil works
  • 1.5km security fencing: $300,000
  • 3190m chainlink fencing: $319,000
  • Drainage: $938,000
  • Farm underpass: $500k
  • Minor grade separation: $1.25m
• Station: $5m
• Land: none required.