Despite the lessons, safety lapses remain

November 19 and 24, 2010, are fateful dates in the industrial history of New Zealand.

This is when two explosions ripped through the Pike River Coal Mine, tragically killing 29 miners. The final report of the royal commission set up to investigate the cause of the disaster was made public on November 5, 2012. It is a depressing tale of safety deficiencies in the mine.

Britain went through a similar process after the Piper Alpha disaster in the North Sea in 1988. Piper Alpha was an offshore oil and gas platform which was destroyed in a fireball when a massive hydrocarbon leak ignited and 167 workers were killed. The British Government launched an inquiry, chaired by Lord Cullen, to establish the cause. To this day, the Cullen Inquiry is the most readable and disturbing account of what can go wrong if the inherent risks in any activity are not identified, assessed and mitigated.

The hydrocarbon leak was shown to be the culmination of many factors, including poor management, errors in the design and inadequate training, operation and maintenance. The aftermath of the Piper Alpha disaster brought a major change in how safety in industrial facilities was to be managed.

A key recommendation of the Cullen Inquiry was that merely declaring an industrial facility safe is not enough - management must be able to demonstrate it is safe by producing a document called the safety case. In this the hazards have to be identified and listed, along with a description of how they will be mitigated in the design, in the operating and maintenance procedures and by appropriate and regular training. The objective is to reduce the risk associated with the facility to a minimum acceptable level (judged by a set of guidelines). If required, the risk can be demonstrated to be acceptable via calculation.

The risk of an event is defined by the multiplication of two numbers: 1. the frequency with which the event can be expected to occur (that is the number of times a year) and 2. the consequence, which can be measured in terms of fatalities or cost.

For example, there is a 10 per cent probability of a major rupture of the Wellington fault within the next 100 years (1 in 1000). The consequence in terms of fatalities is estimated to be 400.

Therefore the risk today (it increases with time) of fatality due to a big earthquake in Wellington is 1/1000 x 400 = 0.4 fatalities a year. (Compare that with 12.6 road fatalities a year in Wellington).

Some risks have low frequency but terrible consequences, such as the accidental launch of a nuclear missile.

The consequences could be counted in hundreds of thousands of lives, even if the frequency of a mistaken launch is low, the risk is high because the consequence is huge. To mitigate this risk the nuclear-weaponed nations have elaborate procedures before a weapon can be launched.

Cost and risk mitigation usually go hand in hand. The risk of pedestrians being killed by cars can be eliminated if every road is completely sealed off from the pavement by huge barriers and can only be crossed by overpasses.

Clearly the cost to do this on every road would be enormous; by not doing this, society has to decide the cost limit to avert a fatality. The cost to avert a fatality is the cost required to mitigate fatality divided by the potential loss of life due to the event.

For example, if on average one person is killed every four years on a stretch of road, and the overbridge costs $1 million to install and is expected to be in place for 30 years (ignore maintenance costs in this example) then the implied cost to avert a fatality over the lifetime of the bridge is $1 million/(30 x 1/4) = $153,300. Someone therefore has to make the decision if this cost is warranted.

To its credit, New Zealand legislation was quick to take on board the lessons learnt from the Piper Alpha disaster and incorporate the key recommendations into the health and safety legislation. As a result industrial safety has improved. Nevertheless, according to the royal commission into the Pike River coal disaster, the identification, assessment and mitigation of serious risks were either not undertaken or completely inadequate.

Pike River is a wake-up call for many other industries in New Zealand where the management of safety is still unacceptably poor.

Taranaki Daily News