Wednesday 31 July 2019

Midland Line [4B]: Arthurs Pass-Otira 2: MRC Summit Line 2

Following on from last evening's post here is the rest of the Summit to Otira route. We are assuming plans will exist for the climb up from Arthurs Pass Station to the summit as there are many plans in the Archives collection, but few of them have been scanned as yet which will make it necessary for us to go through much of the remaining collection in the reading room whenever we have time. Of the ones that have been accessed so far we have been able to source the entire route down to well beyond Otira (at least 12 miles) and have used plans and drawn the route as far as where it comes alongside the existing route (5 miles) as the plans beyond that point are difficult to align to topography because they are so old.

Starting from the summit (the actual pass known as "Arthurs Pass") at 920 metres ASL and with a railway station marked as "Summit Station", the proposed line begins to descend towards Otira. The initial section being right alongside the highway and passing Lake Misery, the gradient here being 1 in 15.
At the 1 mile post the line has descended about 100 metres.  Shortly thereafter the location of "Kopeki Station" is reached. It's not immediately obvious why another station was needed so close to the summit. The origin of "Kopeki" is unclear, but there is also a creek of that name marked on the plans, which is what is known today as Pegleg Creek.
Kopeki Station would have been about where the road used to head up the zig zag. This notorious feature of the highway for more than 100 years was replaced in the 1990s by the present Otira Viaduct. At this point the proposed line left the proximity of the highway, understandably given the abrupt change in heights where the highway viaduct crosses the bottom of a big slip, and crossing over the top of the present tunnel it follows less undulating terrain further west.
As the proposed line crosses the slip above Park Creek it reaches the 2 mile peg. The altitude is now 740 metres, representing a descent of 180 metres from the summit.
 After crossing over the top of the present rail tunnel again, the proposed line reaches the site of "Flat Top Station". This was to have had a separate yard as a spur off the main line. The route then makes a big curve westward before it reaches the 3 mile peg, now at an altitude of around 640 metres. Again there is the question of why another station was needed so close to the previous one.
We saw this map in the previous post and here it is again. This one is scale 1:8000 (the others are scale 1:5000) to fit the entire curved section in, which would be extremely difficult to show otherwise. At 4 miles the altitude on the surface was 810 metres, underscoring the need for the tunnel to continue the descent through the hillside. Upon exiting the tunnel the 520 metre contour line is crossed and on reaching the 5 mile peg the line has descended to around 500 metres, about 20 metres higher than the present line. Considering that the present route is descending at 1 in 33 towards Otira station, the 1899 line still has to achieve very steep grades to reach Otira and there is a stretch of 1 in 22 along this section. See the comments on the previous post about the grades through the 3-5 mile section of the route. One of the old Midland Railway Co plans (drawn by the actual company) shows "Goat Creek" as the name of the station where Otira is today (at 7 miles).