Posting has been slow for the past week as I have been working on some technical challenges to produce the map tiles for the Okaihau and Opua lines. These have now been overcome and the tiles are now in the GIS for the historical imagery of Okaihau, Otiria, Kawakawa and Moerewa to add to the ones of Kaikohe that I already had but haven't done any work with yet. What I did get done apart from that in the last few days was the map of the Marsden Point corridor.
The Marsden Point line has been an idea in one form or another for over 100 years. Back in 1914, the government at that time surveyed a branch line to Waipu, which is a township south of Ruakaka. Construction works were undertaken over the subsequent ten years, but the line never opened. I don't have any information on the route it would have taken; it is possible it could be partly the same as the Marsden Point corridor, but since State Highway 1 is there today, we don't know if any construction works are still visible or have been absorbed into the highway or other roads after such a long time. Anyway it was abandoned.
The idea of building a line to Marsden Point itself has existed since the 1970s with the oil refinery for NZ developed there in the early 1960s. Firstly there was an idea to bring coal in to run the Marsden Point power station which had up to then run on oil, because the cost of oil had gone up, and then the development of the port was also considered in 1979, but as the port did not really get up and going at that time, there was still no real justification for a railway to be built. The NZR proposal for the line, produced in 1981, came up with a scheme for building a line which would have needed five rail bridges, two road overbridges and a tunnel.
Nothing more was heard of the idea until the early 2000s when Northport (Marsden Point) began to be developed as a replacement for the port of Whangarei. The development of the new port did not include the rail line link. Another feasibility study suggested that a 16 km branch line would be needed at a cost of $87 million. Further work was undertaken between the various parties with ONTRACK to resolve various questions and challenges and get a business case together. When Port of Whangarei finally closed in 2007 there was still no rail line, but at that time Northland Regional Council was buying up the land needed for the corridor. This was followed by ONTRACK in 2008-9 formally designated the route as a rail corridor.
However in late 2008 there was a general election and the pro-rail Labour government was defeated at the elections and replaced by a National Government which immediately put a lot of constraints and limits on rail development in general, and Kiwirail was required to stop a lot of projects they had underway at the time and develop a turnaround plan to make the business profitable. This proved to be impossible to achieve and the government continued to fund Kiwirail's losses, but the rail network around the country was run down during the nine years National was in office, and there was no more work done at that time on the Marsden Point line, whilst other parts of the Northland rail network were reduced or mothballed during that period.
With a change of government in 2017 to a Labour-Green-NZ First coalition, work has been picked up on the Marsden Point route, now expected to cost around $200 million. In addition, funding of $600 million has been provisionally allocated to renovate the rest of the Northland rail network up to 2020, subject to the business cases being developed. Another round of geological testing was completed earlier this month on the Marsden Point corridor whilst the design work and business case are being developed. This will then lead to tenders being called for the work, and if everything goes well we possibly could see the first sod being turned by the end of this year.
Because the corridor survey data has yet to be input into the Linz property parcels database, these maps are based on the map released about 10 years ago which only gave a general idea of the corridor location. Likewise the shape of the junction at Oakleigh is a question, it will probably be a triangle but I don't know what curve radius they would use. The curve I have drawn is around 200 metres radius. I can't imagine less than 150 metres radius being used for this curve; that would limit trains to a speed of 45 km/h at the junction, which is probably still quite reasonable, as they may end up being stopped for signalling purposes there anyway.
The first four images are Oakleigh station, with the historical image from 1982. Oakleigh was only ever a fairly small station with a dogbox station shelter, goods shed, loop and stockyards siding. None of that exists today except for the dogbox which seems to have survived.
So far as the Marsden Point line goes we'll start by looking at the junction. Here I have drawn a curve at about 200 metres radius and it ends up crossing the swamp, which really can't be avoided for a triangle junction, with the amount of swamp in the vicinity of the station. After that we would expect the route to be reasonably close to the highway so as to make construction through the swamp reasonably easy.
Once we are out of the swamp then the railway can take a straighter route than the highway, which is following a historical alignment that curves around. The land at this point is rolling fields so there is not really much to see at this location.
Here we have zoomed out a lot to cover a lot more distance, specifically where the line turns and crosses a hilly section of ground. This is probably where NZR in 1981 thought they should have had a tunnel. The current thinking seems to suggest this will be a cutting instead. However there are questions over the stability of the hill, and one could assume NZR thought that a tunnel (perhaps built as cut and cover) would have been a better idea to deal with landslips in cutting walls.
The last piece shows Marsden Point and roughly where the line will finish up, next to State Highway 15A. This highway was built within the last decade and does not appear on the late 2000s map that I copied the rail corridor from.