The Maui natural gas pipeline remains at risk of being ruptured by landslides or erosion at a total of 59 different locations, a just-released Government report warns.
It adds that 11 of the locations are considered high risk - and these do not include the spot at Pukearuhe where the pipeline failed in October last year at a $200 million cost to the economy.
Even though the site of the failure has had special work done to help prevent another failure in the short-to-medium term, a 25-metre section of the pipeline remains on the edge of the landslide which is continuing to move, the report warns.
Now, the Government has ordered the 35-year-old pipeline's owner and operator to develop an improved management plan for the whole line, which runs from Oaonui to Huntly, by the middle of next year.
That will particularly apply to the section of the 307km line between Urenui and Otorohanga, where it crosses some of the most inhospitable terrain in New Zealand.
Energy and Resources Minister Phil Heatley said it was critical the lessons learnt from last year's pipeline rupture were acted on, so that can consumers could have confidence in the country's gas system.
"I'm confident that assessments of why the outage occurred are sound and that the action taken to strengthen the system for managing gas outages are sound," he said.
"They will help ensure a resilient gas system."
Pipeline owner Maui Developments Ltd said that given the importance of the pipeline to New Zealand's economy, it was now focused on learning everything it could from the incident.
"In this context, as well as immediate remediation work at Pukearuhe we are updating the safety management study and pipeline integrity management plan."
The company's statement added that the Maui pipeline had operated without major incident for more than 30 years which reinforced the effectiveness of existing risk management practices.
"MDL, however, recognises that in the light of the rupture, gas consumers might require renewed assurances that pipeline risk is still well managed."
The Maui pipeline is one of New Zealand's most important pieces of energy infrastructure.
It carries nearly 75 per cent of the country's total gas supply.
When the pipe ruptured, it took five days to repair and caused massive disruption north of Taranaki where all non-residential customers were ordered to stop using gas.
The Business, Innovation and Employment Ministry (Mobie) has estimated that the gross economic cost of that disruption was $200 million.
Most of those costs were concentrated on the dairy industry, which had to dump 48 million litres of milk, and large industrial plants.
The review has confirmed that the rupture was caused by a large slow-moving landslide, and that the land in the immediate area is continuing to move.
No defect or flaw in the pipe line itself contributed to the failure.
- Taranaki Daily News