Residents confirm tsunami sirens failed

Community feedback on last month's tsunami siren test at Papamoa has backed up anecdotal evidence the sirens were too quiet.

Tauranga City Council planning engineer Barry Somers said the response from survey forms delivered to neighbourhoods in the vicinity of the test showed that the sirens were "pretty quiet" and not widely heard.

The sirens were one of two models shortlisted by the council after pressure cranked up for the city to do more about the tsunami threat following Japan's devastating earthquake last year.

Mr Somers said the biggest risk to lives in coastal Bay of Plenty was the short-notice tsunami, such as that generated by a big shallow earthquake on the Kermadec Trench north of East Cape.

Papamoa's test on June 1 was part of a "due diligence" process needed to evaluate the supplier's specifications. "It would be fair to say that it did not meet our expectations in terms of noise levels."

The next step towards Tauranga getting a tsunami warning system would be decided by the council later this month. It will include a full report on the June 1 test and an assessment of the other shortlisted siren, an example of which already warned residents living in the small beach settlement of Omaha, north of Auckland.

Papamoa's test involved mounting the sirens on cherry pickers at the corner of Palm Beach Boulevard and Sovereign Drive and the corner of Papamoa Beach Rd and Alexander Place.

Mr Somers said the test showed that the system would not reach the noise levels the council needed to achieve of a minimum 75 decibels to 80 per cent of the population. Doubts about the efficiency of electronic hooter sirens has prompted Tauranga City Council member Bill Grainger to reiterate his support for sirens of World War II.

A modern version of the air-raid siren has been promoted by Wellington engineering company Tactical Tooling as offering the answer to Tauranga's tsunami warning problems.

Company design engineer Gary Lewis said the firm originally designed electronic hooter systems but quickly discovered that, due to laws of physics, they were doomed to failure as they could never be entirely successful at long distances. He had looked at a traditional wartime siren and discovered it had an ability to generate a shock wave that had the same shape as thunder or the boom from a supersonic aircraft.

The company claimed it could achieve coverage of Tauranga using six sirens at $10,000 each, at an estimated total installed cost of $100,000.

Mr Grainger shared Mr Lewis' enthusiasm for war-siren technologies. "When a tsunami is coming in, what do people want? They want to hear something, no matter how loud it is," he said.