Consequences of slip could be ‘catastrophic’

A section of the Wairarapa line that sits perched on unstable land could have a “catastrophic” outcome on rail services if a slip were to happen.

The section of track sits 1.4 kilometres north of the Remutaka train tunnel, where there is an area of loose fill material below the railway line on the embankment.

According to documents released to the Times-Age under the Official Information Act [OIA], the risk of an event happening is medium to high and if a slip did happen, the consequences would be “critical/catastrophic”.

“The track could be undermined and potentially closed for a number of weeks, preventing rail services from running”, the OIA said.

KiwiRail said that “the risks are described in terms of KiwiRail’s ability to deliver services, not risk to life or public safety”.

KiwiRail has already completed design work to install metal piles that will be used to stabilise the track. The piles will be driven into the ground in a grid pattern.

The cost of this stabilisation work could not be disclosed due to being “commercially sensitive” and no contract is being made at this stage.

The identified section of the track has the worst final slope rating on the Wairarapa line but is not the worst on the Wellington Metropolitan Network [WMN].

Sections of the North Island Main Trunk between Wellington and Waikanae have higher final slope ratings but with a mixed risk rating due to the topography and infrastructure.

KiwiRail maintains a data set of slope risk ratings for the WMN and completes subsequent reviews and reassessments over the years, especially after weather events that may have impacted its infrastructure.

The rating system grades between very low and high but is a comparative risk rating that evaluates the likelihood of failure and potential consequences to the network and operational safety.

Saturday’s edition of the Times-Age reported that the Wairarapa rail upgrade is expected to come with a $375 million price tag once the project is completed. Still, it is unclear whether the stabilisation work on the slopes would come from this budget.

KiwiRail has been approached for confirmation on the additional expenditure and which budget it would come from.