The history and costings

Source: Wairoa Star Thursday 20th November 2014

 
The mothballed Napier-Gisborne rail line is the northern section of the Palmerston North/Gisborne line. It was built in the

period from the 1920’s to 1940’s and opened in 1943. It was one of the last main line rail constructions in New Zealand and built

to high engineering standards.

In March 2012 the line was damaged in the Beach Loop area with four washouts over a 4.7km section.

Repairing the culverts would cost $3.30m to $4.29 million with the Big Hut slip the most expensive at $750,000-$950,000

and expected to take six to nine weeks to complete. Repairing the south end tunnel was estimated at between $670,000-$870,000

and could take up to 10 weeks.

The May 18, 2012 KiwiRail Napier-Gisborne Line report said all four washouts occurred because culverts were inundated with flood

debris.

At the time of the weather event in March 2012, the culverts in this section of track were code-compliant and were last maintained

in May 2011, according to the report.

Detailed culvert inspections were performed once every six years and focused on the structural integrity of the culvert, inlet and

outlet. The detailed inspection also looks at the stream condition as well as blockages and debris build-up. The detailed inspection

was supported by a weekly track inspection.

After a severe weather event a special inspection was carried out in the affected area. The report concluded that because of the

susceptibility and climate inspections could be annual rather than six-yearly.

This would add a further $6000 to the inspection cost per year. The maintenance work found from the extra inspections was

estimated to cost between $40,000 and $70,000 per year.

The KiwiRail report recommended reducing line washouts due to slips and dropouts by undertaking prudent engineering works.

It said the Wairoa to Gisborne section was more vulnerable than the Napier to Wairoa section and this was reflected in the repair

estimates. In this section alone there were at least 13 embankments of similar height to those that failed and might pose a similar

risk of embankment collapse due to upstream ponding.

It noted another high-risk area needing significant work was the section of the line alongside the Kopuawhara River. A combination

of river protection, slope stability and drainage work was required along this stretch of the corridor. Removing these risks was costed

at between $0.8m to $1.5m.

The KiwiRail repair bill included a nominal amount for the Napier to Wairoa section to acknowledge there were many rivers that the

railway ran close to.

Taking into account past history, the report said major infrastructure outage due to weather every two to four years could be

expected on this line. The geography of the line made it difficult to eliminate damage against such events.

But the report stated improvements at risk areas and maintaining drains, culverts and slopes after severe weather events would limit

damage.

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