Opawa Rail Bridge Rebuild: Is Road Widening Relevant?

Since last July, work has been underway at the Heathcote River in Opawa, Christchurch, to rebuild the double track rail bridge there. The photos below are from a recent track occupancy which was being done in order to construct a new abutment at the west (or in railway terms, south) end of the bridge. This is where the railway passes over Richardson Terrace and where historically the terrace has been a one lane road due to the position of the existing abutment of the railway bridge. The new position of the abutment, which is likely to be costing Kiwirail a significant amount of money to construct, would allow the position or width of the road to be changed. As so far it has not been possible to locate any information about this project at the Christchurch City Council web site, it is unclear exactly what the intention of the Council is in regards to this project. A request of official information from the Council is being considered to clarify this.

Richardson Terrace and Clarendon Terrace (on the opposite bank and which also passes under the rail bridge) are historically low lying roads along a tidal section of the Heathcote River. Consequently they are often flooded when a heavy rainfall coincides with a high tide. The roads have limited clearance under the Brougham Street expressway bridge and the rail bridge and therefore cannot be raised, neither can they be practically lowered unless stopbanking is constructed to hold back the river as they would be below the high tide mark. Since the quakes raised river bed levels in Christchurch, councillors have been finally forced to get their heads out of the sand and deal with the ongoing flooding problems in this area which have become much more severe, this has involved land purchases in some areas nearby and a requirement to raise the floor height of new properties which is very apparent along the Heathcote River in St Martins, for example.

If the rail bridge is lengthened as suggested, there are a few things that could happen with the extra corridor width at Richardson Terrace:

  • Widen the road to two lanes.
  • Build a stopbank to protect the existing road from flooding (pumps would also be needed to carry floodwaters away)
  • Widen the river channel to increase its capacity.

These options are rated in inverse order of sensibility. Widening the road may well be demanded by people who use this road as a rat run but the one lane section of it is so short as to be almost irrelevant, and out of all proportion to the cost involved i.e. it would not pass any reasonable BCR assessment. These two roads are not able to be used by heavy vehicles because of the height restrictions and keeping them open under the bridges is not essential in the slightest because there are a lot of other roads that connect into these roads at T intersections. Anything that addresses the flooding of the area is much more important. These roads should only be used by the people that live in them, and there’s even a question over whether anyone should be living there long term with sea level rise issues coming to the fore. In fact both roads have been temporarily closed for parts of this project, Clarendon Terrace on the far side has been completely shut for months to be used as a work site and Richardson Terrace has been blocked except to pedestrians and cyclists. This has hardly been a major inconvience to anyone.

If any more information comes to hand about what is happening with this work the blog will be updated. Here are the pictures of the overnight work, just one part of the big project that has been going for some months.

Work at the west abutment, this machine is using a post hole digger type of attachment to drill into the ground for unknown reason.
The same activity seen from alongside Brougham Street. This work was taking place on the 21st of March, 2021.
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