Friday, 17 April 2009

Caversham’s Railways

Caversham is a suburb of Dunedin and I spent a week there recently. It is one of the oldest parts of the city, established in the late 1870s, and has always been bisected by a railway line. The original route south of Dunedin was single track and featured sharp curvature, steep gradients and numerous level crossings. The two tunnels at Caversham and Chain Hills were known for smoke nuisance from the steam engines and in that era their clearances would have fallen below the standards of modern day rolling stock. So it was that only some 30 years later a start was made on duplicating and regrading the railway and eliminating the crossings, which in its day was a major civil engineering and public works project. This post focuses exclusively on the Caversham section because it was here that a new double track tunnel was bored through the hill, almost double the length of the original, and a deviation of the route totalling around 3 km was constructed. I’ll start by referring to the map below and noting particular features of the old route. Another copy of this map showing the photographs which are in my Picasa web albums, appears at the end of this post. I suggest you zoom and drag the maps to see features referred to.

View Larger Map
The first question to determine is what route the old line actually took. We know, of course, where the old tunnel is located, as it still exists. However there is virtually no trace today of the route at the eastern end. The map above shows the old route as an aqua coloured line. It is a reasonable assumption that it actually followed the present highway route because that is roughly on the right level and direction. Where did the two routes join? There are two possibilities:
  • Near the South Road overbridges. The road and highway bridges are at the same level. Moreover, the elevation is 30 metres lower over a distance of 1500 metres, corresponding to the 1 in 50 gradient of the old railway at this point.
  • Near the Goodall Street bridge and the old Caversham station. There is a difference in the elevation of the railway and present highway, which possibly could be explained by the highway being constructed by building up the formation. If the new route is at an elevation of 27 metres at this location then this would allow the gradient to be maintained. Evidence for this location mainly comes from a statement that this is the position where the lines diverged, and a photo which appears to show a curve and one of the overbridges over the new route, possibly the one at Goodall Street.
The main issues which oppose the latter suggestion and favour the former are:
  • The difference in levels. At the eastern portals there is a difference in elevation of 15 metres between the two tunnels, the old tunnel being higher. This means the new tunnel was roughly at 25 metres at its eastern portal, which is lower than the 27 metres mentioned above despite the track being on an upgrade. If the new tunnel was at 25 metres elevation then the junction would be at roughly 17 metres which would not work with the 1 in 50 gradient of the old line up to its tunnel.
  • The variation from the deviation map. This document shows that the new and old routes were at the same elevation at a point around 1500 metres east of the old tunnel and just a little east of the latter day station site. The most likely location for this grade crossover is the vicinity of the South Road overbridges as suggested by the former option.
What then is shown by this photo? The bridge could be the Goodall Street overbridge crossing over the new route, but the slope appears to be wrong for this. The piling shown alongside the new track is possibly that referred to in a document on the deviation works which states that such piling was needed to stabilise a slip in the cutting of the new route. Even here a difference in levels is apparent. Despite a statement that Sydney Street was where the lines diverged, this seems impossible to sustain and in fact a significant level difference is mentioned in the same document. The best conclusion that can be drawn from this document is that the lines were already running side by side for a much longer distance, and that Sydney Street was the point at which the new line became more separated horizontally.
Another option which was considered was that the photo shows the South Road overbridge with the two lines crossing on separate bridges, but this appears very unlikely as other details are difficult to match up. The conclusion I have chosen to go with at this stage is that the routes did join somewhere near the South Road bridges. On the map I have chosen to make use of the big curve at this location, but without further research it is quite unclear where the actual junction would have been located and the map shown is really an educated guess. We do know from an old map that the South Road overbridge was part of the original route. Unlike many of the other bridges, the line was not raised at this point.
The second question is where the Caversham station was located on the old route. The railway map drawn at the time the deviation was constructed shows that the station on each route was in a different location from the other route. The present day route’s station site (it closed around 1962) is approximately at the end of Parkside Ave, near the old gasworks. The old route’s station is shown on a 19th century map as being between Catherine St and Laing St. The street called Station Rd is something of a red herring, which may have given access to either site, being roughly halfway between both of them. It is interesting that an old railway overbridge is now located in a reserve alongside the highway near the old station site. This bridge probably came from one of the old stations. This article refers to the location of the station being moved, so it is quite reasonable to assume that there were two separate station locations as a matter of fact.
Continuing west we come to the first of what were five crossings of both routes by suburban streets (shown in light grey, along with part of the old Main South Road). Old maps of Caversham show that these streets coming off what is now Main South Road on the south side of the lines, joined up with streets on the north side, which had the same names then as on the south side, but have been renamed today. Five overbridges appear to have been constructed for the new route, as determined by the remains of abutments still present today, but the advent of the Caversham Bypass has meant that all of them except the Goodall Street structure were removed, presumably along with a significant number of houses. The latter bridge now serves only pedestrians who can also cross the highway on a new structure. The present South Road bridge is probably not original. Just west of it is the bridge that is now called Caversham Place. This was the highway bridge when built, but the motorway bypass rendered it redundant. Beyond this point, the route followed by the highway is original.
At this point both railway routes enter their respective tunnels. The new tunnel was driven by hand through sandstone. Most of it is unlined, which is unusual for a railway tunnel in New Zealand. There is some lining at the portals and for a few short stretches within the main tunnel. The new route was built as double track and originally there were two tracks in the tunnel. In the early 1980s the line was singled, and the rail has been realigned towards the centre in order to improve clearances. The old route veers off the highway to enter an approach cutting right alongside. The footpath alongside the highway is cantilevered over one side of this cutting, which is cut through sandstone (as is the tunnel itself). It is possible to walk through the cutting to the tunnel portal, which is covered with a gate. An excellent view of the portal and cutting can be obtained from the footbridge at the end of Lindsay Road, which crosses over the cutting.
At the western end of the old tunnel, access is blocked off with a high wire fence. The route then crossed what is now Kaikorai Valley Road and curved sharply round past the old Burnside Freezing Works to join the present route at Burnside station. The old Cattleyards station was next to the freezing works. The present tunnel at its western end comes out just east of Kaikorai Valley Road and north of SH1. It then passes under the Kaikorai Valley Road overbridge to enter Burnside station.
Below is the photo map showing the photos in my Picasa albums. The old Caversham railway tunnel is an interesting piece of what might be called “Lost Dunedin”. It has been disused more than 100 years and is tucked away in a hard to find location out of the way in a residential suburb. But it is still in almost the same condition as it was when abandoned in the early 1900s, forgotten but not gone. The tunnel is the main remnant of the deviation; the route on the eastern side has disappeared with the motorway construction, and on the western side there is little to see today.
At the time of writing, a four-laning proposal has been in place for the Caversham Bypass Motorway for some years. It appears the original motorway that follows the old rail route was first constructed in the 1980s. The present section of the motorway following the old rail route, including the South Road overbridge, was only constructed as two lane and a new bridge would be needed for the four-laning. Another aspect of this project is that the road will be pushed out over the top of the approach cutting on the eastern side of the old tunnel. This means that the Lindsay Road footbridge would disappear, although the tunnel itself would not be altered in any way. The change could lead to access to the tunnel cutting being blocked off altogether, as it is at the Burnside end of the tunnel, since the change would make it much more practical to achieve this. At this stage the timeframe for reconstruction of the motorway is unclear and the work might not start for at least five years.

View Caversham's Railways in a larger map
I’ll post another article or two in the next few days covering the Wingatui tunnel deviation and the rest of the route between Dunedin and Caversham. You can see all the photos here.
Online references: 1, 2, 3, 4, 5, 6, 7, 8
A Dunedin man is trying to get the tunnel re-opened for public access. His website is here
Here is an interview that was broadcast on Channel 9 around 2007.