Saturday, 5 January 2013

On the Otago Central trail [4]

Continuing in the vein of the first article but starting from the Cromwell end here are some highlights from the maps so far.
Looking at Cromwell again here is the slightly revised layout showing as we can see a small portion (100 metres or so) of the former railway route which is still visible and out of the water. There has been a bit of speculation elsewhere about how to interpret landform shapes around the vicinity of Cromwell station with suggestions the inlet is the turntable pit. I don’t believe any interpretation can be reached, there was probably a shape in the hill because most of the location of Cromwell is now underwater. I believe there is public access to this small length of formation.
This is a bit further back up the Gorge. The headland to the left where the rail line curves away from the highway is, I believe, another piece of former rail formation at about 200 metres altitude. It is useful to note here that the gradient profile of the line was not a steady climb uphill. It was quite a sawtooth type of profile which was caused by constructing it closely alongside the road and therefore following the highs and lows of the road profile. Therefore it is possible this close to Cromwell (this location is about 2.5 km from Cromwell and, for further reference, directly opposite the Cairnmuir Slip) to have got a height seven metres higher than Cromwell station. This is also a length of about 100 metres and there appears to be public access with a road going around it. However as yet I don’t have any aerial images (unlike at Cromwell itself) to confirm this was the location of the railway.
Chatto Creek station is to the west (in railway terms) of Tiger Hill and in steam days, special trains were often worked between Omakau and Chatto Creek to move the tonnage over the hill which was a significant bottleneck, being a long 1 in 50 gradient. The bridge 76a on the left is in the Chatto Creek ballast pit. The actual extent of the bridge or where a siding would have run isn’t really clear to me at this time. Tiger Hill is basically the three large curves you can see although the grade started a little further east, basically the road overbridge No.74a. That bridge was built in the mid 1960s and replaced a level crossing.
Omakau was itself a significant station at one point and included an engine shed and turning triangle as shown on this diagram. These are of course long gone but the goods shed still stands although now on private land in what used to be the railway yard.
There are two more pictures I want to include in this post before I wrap up. These are the sites of two possible realignments of the line. Improvements of this nature were rare on any branch line, as they struggled to pay their way. For example the Hyde accident disaster site was at a 180 metre (6 chain) curve, unheard of on a main line except maybe in a yard, but quite acceptable on a branch with its lower speeds. Towards the end of NZR days, the speed limit on the Central was 50 km/h from Wingatui to Kokonga and 40 km/h from there to Clyde. Although, by the time the line closed, most major bridges had speed restrictions of 15 km/h put on them, probably because of deferred maintenance. So the kinds of routine improvements seen on mainlines were virtually unknown on branches. And yet, we have two possible realignments shown below.
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On the left the one we can see there is pretty definitely confirmed by land boundaries, but no more. This is about 1 km east of Omakau. One of the frustrations of GE coverage of this area is heavy cloud cover, but Bing Maps has good views, which confirm that on the ground there is no trace of any previous formation to be found. The curve particularly at the bottom would have had to be outside the normal embankment profile making it possible that it would be levelled by a landowner. On the right, this one is based on actual knowledge that a deviation took place somewhere in this area east of the Poolburn Viaduct. Firstly in Dangerfield & Emerson 3rd edition page 28 we have a reference to an unstable hillside near Poolburn where a small deviation was later required. Secondly, travelling on an excursion train in 1989, in the area, the commentary told us there had been a realignment in the 1950s due to unstable ground. Looking at the GE coverage this appears to be the most likely location for a realignment between there and Auripo (originally called Poolburn).
There was of course a more tangible realignment at Prices Creek and that will be covered in a subsequent post.