Editorial: Madness not to drain Crater Lake

When A relatively straightforward piece of engineering will enhance public safety, there can be few grounds for not using it. Certainly not when the excuses are as lame as those served up by the Government to justify its refusal to drain Mt Ruapehu's Crater Lake. These seem even more feeble as tomorrow's 50th anniversary of the Tangiwai disaster looms. More than anything, that event underlines why every possible step must be taken to defuse a potentially dangerous situation.

Sometime before 2005 a lahar is expected to overflow Crater Lake and rush down the volcano's eastern side, damaging or destroying everything in its path. Scientists calculate it could be twice as severe as the mud, ash and water slide that caused the Tangiwai tragedy. The risk, as in the past, will be mainly to infrastructure - roads, bridges and the like. This, however, can be as much a threat to public safety as if houses lay in the lahar's path.

The Government's response has been to install an electronic warning system that, all being well, will raise the alarm and allow the area to be cleared. Transit New Zealand is also upgrading the Tangiwai road bridge so that, in its estimation, the structure will be capable "of withstanding any lahar that hits it".

Nature, of course, delights in debunking such expressions of confidence. As a reason for not excavating the crater rim it is, therefore, as insubstantial as the others advanced by the Government: the argument, for example, that work at the summit would be an affront to Maori spiritual values. In fact, the mountain's original crown would not be disfigured. Today's problem dates only from the eruptions of 1995-96, which created a 7m-high barrier of material that is blocking the lake's former outlet.

The Government also argues that trench-building to allow the lake waters to trickle away harmlessly would be dangerous. Perhaps so. But engineers have suggested that a 100m-long trench could be dug by bulldozers within two weeks at a cost of only $200,000 to $300,000. Vehicle access is available and, better still, bulldozers could be flown in by heavy-lift helicopter. The damage to the Tongariro National Park could be minimised to an acceptable degree.

It is also said that a trench would not solve the problem of lahars spilling down Mt Ruapehu. That is so; there have been 60 lahars on the volcano in the past 150 years and there will be more. But a trench would remove the danger posed by this potentially deadly one.

The Government says its early warning system is the long-term solution to lahars. But such systems are not failsafe. At best they raise the alarm; they will not prevent infrastructural destruction which, if it occurred in mid-winter, could undermine the area's skiing-based economy. Worse still, they provide only a limited warning - 90 minutes in the case of a lahar heading towards the Tangiwai road and rail bridges. Local authorities have made it clear they have little confidence in their ability to evacuate the area. It seems unlikely, for example, that trampers and canoeists on the Whangaehu River could be evacuated in time.

The saving of such lives must be paramount. Modern engineering provides the means to control the lahar's release. The danger could be averted quickly, cheaply and without serious damage to the environment. Pointedly, the Government, which has at least one engineering report in its possession, has refused to dismiss a relief channel on the grounds that it would not work.

Its chosen policy carries a strong hint of refusing to ruffle feathers - and of hoping for the best. That is not only unhealthy but unnecessary. If legislation is required to achieve fast-track consent for the engineering work, so be it. If that, in turn, imperils Tongariro's world heritage status, so be it. That is a price worth paying if lives are at risk.