Box et al., 2000:

"From the available evidence it appears that the clearance diver training conducted at Triangular Island would not generate underwater blast shock waves of significant amplitude to be injurious to mammals at distances greater than one kilometre. The greatest pressure levels recorded were from events contrived to produce maximum pressure transmission. When following normal procedures the safe distance would be much less than 1 km.

Lewis (1996) determined a "threshold" of 34 Pa.s impulse level as the level at which "no injuries" should occur for mammals diving beneath the water surface."

Box et al. (2000) reported that "the only events where impulses greater than this threshold were measured were for four events. For these events the accumulated impulse was greater than the threshold level for varying distances. One event exhibited impulse above the threshold level to a distance of nearly 1000 m from the explosives. This was the detonation of a Mk 82 bomb positioned on the western ridge of the boat channel on Big Bang Beach. The bomb was positioned further from Big Bang Beach than any other explosive during this exercise, some 150 m from the high water mark. This was at the request of the DSTO personnel to enable the measurement of a shock wave with little interference of the surrounding geography. This placed the bomb clear of the rocky point on the western end of Big Bang Beach with considerably more water over the bomb than other explosives during this exercise. The other events where impulses were measured above the threshold also had the explosives deployed in the open as opposed to in holes and channels.

The amplitude of the impulse for every event reduces with distance at a greater rate than the predictions for deep water. This is further evidence that the shallow water disrupts the blast shock wave as it propagates through the water.

The practice of deploying explosives in the natural and man-made channels and holes on Triangular Island is recommended. It is not possible to recommend maximum explosive limits on the evidence produced from this exercise but explosives quantities used during the November 1999 exercise as reported produced no significant pressure levels at distances over 1 km."

---

Citation and/or URL

Box, P., Marian, F. and Wiese, D. 2000, Shoalwater Bay Defence Training Area, Dugong Research Program, Underwater Blast Measurements, Department of Defence (Defence Science and Technology Organisation) 

Spatial Coverage

Shoalwater Bay Defence Training Area, Great Barrier Reef Marine Park.

Temporal Coverage

November 1999

Update Frequency

Other Information

None