Almost exactly 12 months ago on 24 October 2011 there was a failure of the DN 750 Maui Pipeline which runs 307 km from from the Taranaki region to the Auckland region of New Zealand. The pipe leaked as a result of pipe deformation from a slow landslip. Because the Maui pipeline is a crucial energy source for the northern part of the North Island there have been extensive investigations. The NZ Government has just released a long series of documents about the failure and its implications, available here.
There are hundreds of pages of supporting documents and so far I have skimmed just a couple. From this I will make only a couple of observations:
The main review report is not a technical document but dwells on the effects of the interruption to gas supply for the five days it took to repair the pipeline and resume operation. The economic cost of the outage was estimated at NZ$200 million, or NZ$40 million per day. There were widespread implications for the dairy industry (with flow-on environmental effects arising from farmers’ need to dispose of milk that could not be processed) and also impacts on health and disability services due to loss of ancillary functions such as heating, hot water and laundry.
I have written before about the community impacts of supply disruption, and this is another salient illustration.
The other interesting observation is the nature of the failure. I have not yet read the technical reports but this photo seems to tell a fairly clear story:
Ignore the small black arrows but look closely at the black oval. You can just see a crack where the buckle induced by the landslip has initiated a fracture along the seam weld. (The diamond-shaped piece of black tape marks the top of the pipe.) An interesting failure mode. There are many more photos in the collection of technical investigations here (125 pages and 7.6 MB). It will be interesting reading.