Oamaru's Own Big Bang

Contributor Graeme Ferris relates a gripping story about efforts to fortify Oamaru harbour.

Most of us have heard of the big bang theory that emiment British astronomer Fred Hoyle considered totally ridiculous and spent many years of his life opposing.

There were however absolutely no theories surrounding our own little Oamaru harbour big bang, but they happened, one of them with sad consequences.

The first harbour quarry big blow-out occured one Tuesday afternoon in August 1938 and the associated earth tremor shook buildings over a large area of town. Several substantial harbour sheds including the engine shed and blacksmith's shed were wrecked by this shot which brought down 150,000 tons of rock and rubble to be used for harbour breakwater armouring.

The second big bang was indeed a large blow-out and I recall, even though about two miles distant, rushing outside to try and see just where and what this huge November 1943 noise was all about. After all, we were in the midst of WW2.

At the harbour quarry, two people were killed by the falling rock from this 1943 blow-out, one, a harbour board employee, the other, an employee of the then waitaki electric power board. Both victims were sheltering in a purpose-made slit trench located adjacent to the north west corner of the quarry, almost exactly where the eighty one year old Stothert & Pitt Ltd steam crane sits, the trench about as far away from the blasting tunnel as possible, yet still remaining in the quarry area.

For the second time in five years, the area resembled a bombsite with the sheds as far away as the carpenter's shop on Cross Wharf being riddled with holes. Once again, these harbour sheds were repaired or rebuilt with salvaged corrugated iron. Much of it from sheds now no longer required.

The Harbour Board was appropriately silent on the disaster and the quarried rock, as engineers had previously correctly told them, was totally unsuitable for the use they proceeded with in armouring the seaward side of the breakwater.

By 1956 the first batch of 20 tetrapods for breakwater protection was ready to be placed in position by the board's aging steam crane and apart from the later vertical drilling of the quarry face, no further blasting at the harbour board's quarry took place.

The random placing of this small number of tetrapods for breakwater protection proved to be an expensive failure, their correct designed interlocking placements being by the thousands, not hundreds, and certainly not tens.

The tetrapod saga continues in 2007 with the proposed random placement of almost 200 mostly recently constructed 15-tonne concrete tetrapods plus a few leftover concrete cubes, a legacy of previous patch-up days.

Graeme Ferris