Saturday, 12 May 2012

Road & Rail Bridges between Reefton and Inangahua

Currently on the Stillwater Westport Line between Reefton and Inangahua there is one road-rail combined bridge, the parallel bridge at Inangahua Junction. It was built around 1925 from memory and has survived two major earthquakes in 1929 and 1968 both of which caused significant damage to the piers at their bases. There are only two other bridges of this type in NZ: the one at Westshore just north of Napier, which has a two lane road that closed to traffic some years ago, and the recently built bridge at Arahura near Hokitika which has two lanes for traffic.
There also used to be four other bridges with a shared single lane deck that had rails up the middle of it. During the 1970s and 1980s all four of these were replaced with new road and/or rail bridges. The maps below detail these four bridges and we start by heading out north of Reefton.
Coming north from Reefton the first bridge is at the Waitahu River which is the biggest of all the rivers. I understand it was bridge no. 74 on the line and was about 150 metres long. It was built by the Public Works Department in 1906 when the railway was put through north of Reefton. A flood in 1950 required a Bailey Bridge for the road while repairs were put in hand.  The new railway bridge was built in 1972 and the old bridge was then handed over to the Roads Board. It was at the end of its useful life by 1979 and had to be patched up until the present road bridge could be opened about four years later.

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Here we can see that I have chosen to guess (green route) that the old combined bridge was some distance east of the current road and rail bridges. There is some support for this with what appears to be an old rail formation on the north side of the bridge and possibly also an old road formation also on the north side. On the south side you can see nothing of the approaches of either for that location, so where the rail line went is just a guess.
Continuing north the next bridge location is just north of Cronadun station, at Boatmans Creek. This is such a small waterway that you wonder why the road rail bridge was the only option for so long. It was originally Bridge no. 76 on the line and was about 70 metres long. A new road bridge was built by 1972.

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In this case the path of the old road is pretty clear; on the south side old sealed roadway still goes most of the way, while on the north side the road still exists and is open up to nearly the end of the bridge. It looks like the road bridge was replaced first, which left NZR to keep using their rail bridge. This bridge was still nearly all wooden until the mid 90s, as you would expect if it was the original. It has since been rebuilt to make it stronger.
Third bridge is at Larry’s Creek, a larger waterway, and this bridge was built as no. 79 by the PWD in 1900 and was about 95 metres long. The bridge got damaged a few times by floods and temporary Bailey bridges had to be built a couple of times for the road traffic. One of these temporary bridges got washed out by another flood before the repairs were completed. The current road bridge was built about 1974.

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Just like at Boatmans Creek, the road bridge being replaced first left the Railways able to keep using their bridge on its original alignment. I would doubt considerably that this is still the original bridge however as it would have needed to be strengthened at some stage due to the heavy coal traffic on the route these days. The road formations to both sides are easy to see.
The last of the four bridges is where the Inangahua River is crossed at Landing. Don’t confuse it with the Inangahua Junction bridge I mentioned above. It was built by the PWD before 1914 and when the NZR took it over they had to renew a lot of the timbers because of poor quality hardwood being used. It was about 80 metres long. The Inangahua Earthquake in 1968 caused a lot of damage to this bridge. It was already being looked at for replacement but the earthquake meant it had to be patched up until new bridges could be built as a priority. The damage was mostly to the concrete abutments and piers. The abutment at the south end was so badly damaged that an extra span of 5 metres was added. The bridge got patched up from time to time throughout the 1970s and whenever this happened, road traffic had to be diverted on Browns Creek Road all the way up to Inangahua to cross the river there.

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NZR opened their new rail bridge in 1982 and handed the old one to the Roads Board. It was still in very bad shape and it just got patched up a bit more and lengthened again at the south end. Within 5 years the new road bridge was being built. It was about 1988 when the bridge was decommissioned and it was worth so little that it was slowly dismantled over the next few years. As you can see from the map, the old bridge was just to the west of the rail bridge and this meant that the highway had to make a sharp right angle turn onto it on the south side. Today the old highway on the south bank can still be seen alongside the current route. On the north side the highway had to cross over the railway line and then it went alongside it to join up with the current highway. Today the level crossing is on the south side of the river because the road bridge is now to the east of the railway. 
With all the maps this is a long post. I have some photos that I hope to post in a future blog but I won’t make any guarantees when this will happen as it is a lot of work to get them together.