Thursday, 7 July 2016

Gisborne line fragile and damage prone

Well with a little help from some friends I was fortunate enough to obtain a copy of Chris Woods' out of print history of the railways in Eastland, "Steaming To The Sunrise", published 20 years ago. Now this book contains a lot of detail about the history of the construction and operation of the Gisborne Line. Here is a summary of key maintenance timelines as gleaned from it along with my other sources.

  • 1938, February: Major flooding on the incomplete line washes out culverts and embankments. Eskdale bridge completely collapses. Construction camp at Kopuawhara washed away with death of 22 workers.
  • 1938, May: Repairs to previous flood damage undone by further major flooding.
  • 1955, July: 100 metres of track pushed out of alignment by major slip at Waikokopu, causing closure for 10 days.
  • 1955, end: Line diverted at Tunnel 24 due to continual movement of hillside towards sea causing tunnel lining to crack. Tunnel eventually collapsed the following year.
  • 1956, December: Major slips at both ends of Mohaka tunnel. Repeat instances in subsequent years lead to portal extensions in early 1960s.
  • 1957, August: Huge landslide at Waikokopu closes 300 metres of track. Estimated 1 million tonnes of material slid downhill after prolonged rainfall. Reconstruction work takes three months in all, with line completely closed for the first four weeks.
  • 1977, June: Major rainfall and flooding causes severe damage to 27 km of track between Paritu and Muriwai. Repairs require the shifting of some 300,000 cubic metres of soil throughout the Whareratas. The line is reopened to limited freight traffic almost two months later, but repairs to a standard suitable for passenger traffic are not completed until early 1978.
  • 1983: Storm damage closes line for two months.
  • 1988: Cyclone Bola cuts railway in 69 places with slips and washouts. Napier-Wairoa section reopens after two months of repairs. 100 metres of embankment at the south end of the Waipaoa River Bridge is washed out requiring the bridge to be extended 145 metres in total. Although the line is finally reopened after 8 months of closure the passenger services are not reinstated. Several piers under the south end of the Waipaoa bridge are badly scoured by the flooding but to save on repair costs, only the former southern abutment is underpinned with new piles. The result is a bridge with a new permanent speed restriction of 30 km/h, an axle load restriction of 14 tonnes, a weight restriction banning more than one locomotive on the bridge at a time, and regulations requiring it to be completely closed whenever the wind speed or water level exceeds certain limits.
  • 2005, May: Nuhaka Bridge collapses while under repair due to teredo infestation of wooden piles. Installation of new concrete piers allows reopening of line after some two months. 
  • 2012, May: Major weather event causes three significant washouts in the Whareratas and the embankment is undercut by ponding at Wharekakaho Stream north of Beach Loop. Kiwirail estimates repairs at a cost of around $4 million. Decides to mothball Wairoa-Gisborne section of line. Napier-Wairoa remains open but is mothballed at the end of the year due to insufficient freight traffic.
  • 2015, June: Gisborne City Vintage Railway is given operating rights over Muriwai-Gisborne section subject to completing track repairs. Replacement of sleepers and rebuilding of several small bridges is eventually completed later in the year at a cost of more than $200,000 which has to be raised from grants and other external funding sources as the railway society has no money.
  • 2016, May: Gisborne District Council estimates a cost of around $45,000 to repair potholes at a level crossing on the section of line operated by GCVR. The railway society is unable to fund the work leaving the council to pay.
  • 2016, June: Further problems at Wharekakaho Stream near Beach Loop require a long reach excavator to be brought in to unblock the culvert under the railway line.
The above are the most major of the events that have happened on the line. We know that there have been additional other times when the line has been closed for periods due to slips happening and we also know that there has been a lot of damage to the railway formation alongside the Kopuawhara Stream where a lot of weatherproofing would be essential to address this damage in years to come. In addition there is another major issue along the line at Blacks Beach near Mahia, where erosion has cut into the ground below the highway which the railway is next to. Sooner or later this will result in the railway being undercut. The state of the Waipaoa Bridge is a major issue the next time there is a really big flood in the river, and the next flood control scheme for Gisborne appears to require the bridge to be raised higher which is likely to be an unaffordable expense for Kiwirail. The hillside at Beach Loop is constantly sliding towards the sea hence the work needed at Tunnel 24.