The south end of the Chilean broad gauge
Transandine Railway by Mallín Chileno
History The present survey has as its objective the study of the possibility of building the transandino by Mallín Chileno, following the banks of the Bío-Bío in the section between Santa Bárbara and Lolén station on the survey by way of Curacautín. The said survey, or preliminary investigation, involves 6 kilometres of tunnels, and an adverse gradient of 17.5‰ over a distance of about 19 kilometres. It has been thought that the route by Bío-Bío with a gradient of 1% would compensate for the expenses of construction, which the steep sections of this route in front of the Callaque volocano would require.
We pass on to describe the principal features of this route.
Description of route and profile The route starts at Santa Bárbara, at a level of 224.40, to pass the foot of the sharp rise which gives access to the plain of the El Fiscal estate. It would be necessary to respect the public road, which is being built a the foot of the said rise; this can be done without great expense. The route follows on to parallel the public road towards Rapa for a considerable distance through flat land, and without appreciable earth moving. In this section the construction of bridges over the Pichi-Mininco and Collinco streams of 15 and 6 metres respectively will be necessary.
From Rapa (Km. 14), the line occupies a narrow track which remains between the foot of the side slopes and the public road, which cuts the edge of the bank of the Bío-Bío. The route in this part, although rough, involves several cuttings in hard rock but not of great volume. It will have gentle curves and gradients to reach the river crossing of the Guaiquicura [= Huequecura later on]. Here the river has a width of about 60 metres and [its valley] a depth of 30 metres. Having crossed the river, the route is located in a plane which rises gently until meeting the buildings of the Los Notos estate, at a level of 330 at Km. 22. From here there is a gradient of 1% for three kilometres through flat land, and then a horizontal length of 7+300 kilometres through equally flat land. It follows a side slope with the usual amount of earth moving, and then crosses a plain for 500 metres to reach the Agua Blanca stream, which it crosses with a low bridge of 10 metres span. This route would rise at 1%, and continue at the same gradient to the entrance to the valley of the Queco. On this route there are plains, and a length of about two kilometres of rocky outcrops. From this last point the line follows on the level until the river crossing of the Pangue. Having crossed the Queuco river at the point where this river bends abruptly to the north, and in front of the Boqui Amargo ravine [it crosses it] with a viaduct 35 metres high (three spans of 45 metres) and high embankments to give access. Having passed the Queuco, the line crosses the Callaque gateway to follow alongside the Bío-Bío, resulting in a cutting in the gateway some 20 metres deep. Then some rocky side slopes are reached for a distance of one kilometre. It then drops down on to the Pichi-Callaque table land and reaches the crossing of the Pargue at the same level of 450 [metres]. The valley of the Pargue has a length of 300 metres. It is necessary to cross it with a viaduct of three 30 metre spans, 35 metres in height with considerable approach embankments.
The location of the bridge over the Pangue will have to be carefully considered in order to reduce the cutting through the sharp rise which immediately follows, and which could be up to 25 metres deep. It is convenient to follow with the route at the foot of the side slopes, and near to the river, to keep the rising gradients to no more than 1% until the summit of La Zorra is reached
in front of the El Porvenir sawmill. Here the side slopes take a sharp change in direction, changing to a depth of more or less 70 metres. Swinging to the left, a tunnel 350 metres long is unavoidable, so the route stays on a ledge in order to give it support on the hillside.
It follows along side slopes, gentle in parts, but with rock and boulders until reaching a distance of 700 metres, and leaving the side slopes of San Pedro at a level of 475 at Km 57+300.
From here to Km. 86+000 is the most difficult part of the route. There are two solutions possible here:
1st) Follow with a gentle gradient by the Huella plain until it reaches a level of 530 in front of Lebu (meadow); to be followed by a gradient of 2% until crossing the Malla or Guaigualí stream; then level for 3+500 kilometres until reaching the summit of Palmuche, which is traversed by a tunnel 1500 metres long; then falling with a gradient of 1% to the Lepoi meadow a kilometre after crossing the Quepuca stream, which would be crossed by a three span viaduct 40 metres high and 100 metres long with buried abutments. This route mostly follows steep and rocky side slopes in which it will be necessary to use some retaining walls and possibly short tunnels.
2nd) The other route would have a gradient of 1% until passing the Malla stream, which it would cross in this case near its joining the Bío-Bío where the stream widens to 80 metres by 50 metres in depth; a viaduct of 40 metres in height and three spans of 25 metres would be required. In addition the crossing of this stream would require the construction of a tunnel 50 metres long at the approach to, and a cutting 15 metres [deep] on leaving the viaduct. Having passed the stream, the route would follow with a gentle gradient, through flat land for a distance of 2700 metres, to enter the rocky side slopes and outcrops of the Palmuche summit. This summit has its very steep flank dropping 200 metres to the river. This will make it necessary to introduce some curved tunnels with a length of about 2000 metres and to locate the line in steep side slopes for 2+500 kilometres until the Quepuca meadow is reached. The stream of the same name would require to be crossed in similar conditions to that on the other route, but with a height 10 metres lower.
This route would be more costly than the first one, but the costs of traction would be greatly reduced.
The route with the 1% gradient could not be visited along its whole length; but it can be confirmed that it would be within ground sloping at 60º to the horizontal, with lava flows, and like that part of the first route which has the 2% gradient.
From the Lepoi meadow, the route crosses a sharp rise with a tunnel 100 metres long to enter the meadows which are in front of the Lolco valley and a little before it. A kilometre from the mouth of the Lomín or Llahue discharging into into the Bío-Bío the route crosses this last river in order to be sited in the western side slope to avoid the steep rocky outcrops of the eastern side slopes and other difficult terrain of the side slope. It starts in some easy outcrops to cross a distance of 300 metres to again cross the Bío-Bío at Nitrito, in both cases using a single span of 55 metres.
From Nitrito to the junction with the route by Curacautín, to near Lolén station (Km. 77+600), the route presents few difficulties, and the general gradient is that of the river. The route will lie at about 15 or 20 metres above the level of the river, passing through gentle plains and side slopes but with steep slopes in a few short lengths as is shown on the longitudinal section.
Among the most important works the following are worthy of mention in this last section:
Veta tunnel , 200 metres long
Bridge over the Río Llanquén, 1 span of 30 metres.
Bridge over the Río Ranquil, 1 span of 30 metres.
Bridge over the Río Pehuenco, 1 span of 30 metres.
Bridge over the Río Rahue, 1 span of de 50 metres.
Bridge over the Río Bío-Bío, 1span of 50 metres & 1 span of 25 metres.
To finish, it may be stated that the route can be carried-out using in only a few places the minimum radius of 300 metres and in these places it will not be possible to ease it without a disproportionate cost.
APPROXIMATE COST OF LINE
A) Infrastructure In order to establish with greatest certainty the cost of the infrastructure, I believe it convenient to gather together the various lengths of the route of equal or similar amounts of earth moving, expressing this as flat land or gentle side slopes, in steep side slopes of between 45° and 60°, and in [rocky] outcrops.
1st) Category.—Infrastructure in level land and gentle side slopes: Km.
These types make up a total length of 93+900
2nd) Category—Infrastructure in lands, in side slopes of 45º to 60º and rough ground with much earth moving:
These summed give 44+850
3rd) Category.—Infrastructure in outcrops:
Between Km. 37+200 & 39+100 2 000
At Km. 49+000 1 000
Palmuche side slopes 2 500
In front of Llahue 300
In front of Km. 101 500
In front of Km. 131 150
Total of 3rd category 6 450
The earth movement of the Los Angeles to Santa Bárbara line may be used here where the volume of cut amounts to 5 m3 per metre of line, increased by 50%; giving 7.5 m3 × 93+900
A length of 44+850 Km. At 45 m3 per running metre for line in side slopes between 45º and 60º, increased by 30% to take account of the small tunnels and retaining walls which will be needed here; giving 59 m3. We then have
59 m3 × 44,850 = 2 646 150
Embankments 2 646 150
Deals with providing a platform in side slopes between 60º and 70º and rocky faces. Retaining walls and short tunnels will be required. Taking this into account the volume per running metre which would normally be 67 m3 should be increased to 100 m3. We then have in 6+400 Km. 6400 × 100 640 000
Embankments 640 000
Cuttings 3 990 400
Embankments 3 990 400
This earthmoving gives a total of $ 18 355 840
MAJOR ENGINEERING WORKS
The major metal bridges along the line and their costs are as follows:
Pichi-Mininco bridge 1 span 10 metres. $ 30 000
Huequecura bridge 1 span 60 metres. 280 000
Agua Blanca bridge 1 span 10 metres. 30 000
Perquenco bridge 1 span 10 metres. 30 000
Queuco viaduct 3 span 45 metres. 700 000
Pangue viaduct 3 span 30 metres. 500 000
Malle viaduct 3 span 25 metres. 320 000
Quepuca viaduct 3 span 30 metres. 650 000
(Llahue) bridge 1 span 55 metres. 240 000
(Nitrito) bridge 1 span 55 metres. 260 000
Lianquén bridge 1 span 30 metres. 105 000
Ranquil bridge 1 span 30 metres. 105 000
Penhuenco bridge 1 span 30 metres. 105 000
Rahue bridge 1 span 50 metres 240 00
Bío-Bío (Lonquimay) bridge 1 span 50 metres
1 span 25 metres 310 000
SUM $ 3 905 000
MAJOR ENGINEERING WORKS
Minor engineering works $ 3 996 000
Diversion of water courses and ditches 88 500
Diversion of roads 100 000
Fencing 885 000
B.—Superstructure of the way:
Permanent way $ 4 505 600
Telegraph line 126 195
Level crossings 30 000
Stations .— 8 Station buildings at $ 126 221 each $ 1 009 768
Signals .—8 28 800
Distant signals 3 040
Surfacemen's houses N.º 14 238 000
Tunnels $ 4 372 500
SUMMARY OF ESTIMATE IN CURRENT MONEY
1) Earth works $ 18 355 840
2) Major bridges 3 905 000
3) Minor engineering works 3 996 000
4) Diversion of water courses and ditches 88 500
5) Diversion of Roads 100 000
6) Fencing 885 000
B.—Superstructure of the way:
1) Permanent way 4 505 600
2) Telegraph line 126 195
3) Level crosings 30 000
4) Stations and signals 1 041 608
5) Surfacemen's houses 238 000
Tunnels 4 372 500
Sum $ 37 644 243
Contingencies 15% 5 646 636
Total in current money $ 43 290 879
Or a cost per kilometre of $293 500
Estimate in gold of 18 pence. Steel material. Length of line
Km. 147+500 at 131 093 gold of 18 pence gives $ 19 336 000
Before finishing off, I consider it appropriate to draw attention to the situation whereby the length of the line by the Bío-Bío amounts to 147+500 Km., whereas, measuring the route on the map, it amounts to 126 Km. This appreciable difference is explained by the series of twists and turns of the river, principally in the last section; but it is more accurate to say that the distance has been measured on the ground with a pedometer, and that due to the interruption of the roads beside the river and to the series of summits which it has been necessary to surmount the distance in many cases could only be estimated. Nevertheless, it has been left without correction in order to take account of unforeseens which always grow in this type of survey.
Santiago 8 January 1924