Whangamata marine oil spill deployment exercise

Report: TR 2012/26

Author: D Lovatt

About this report

This deployment exercise demonstrated the alternatives to the standard operating procedures when intercepting heavy oils entering harbours and estuaries.

In the scenario of a major release of heavy fuel oil at sea, it is unacceptable to follow standard procedure pre-Rena. This was to contain and recover the oil once the oil had entered the harbour.

Most of the NZ coastline is directly exposed to the open ocean which makes the booming of oil in the exposed open-sea area very difficult, due to swell and wave action on the boom. Oil response booms fundamentally work in flat water and in a current of less than three knots.

The only option other than letting oil enter the harbour, or using dispersants, is to intercept oil in the relatively swell protected area of the harbour entrance. Unfortunately most harbour and estuary entrances are narrow, causing high flow areas. The advantage of the narrow entrance is that the area requiring booming is very small and any deflection, such as a boom set at a very slight angle to the current, will gradually move oil laterally across the current without forcing oil under the boom. A standard boom set would be at an acute angle to the current, putting huge strain on gear, distorting the boom into a belly and forcing any oil under the boom.

The strategy of this exercise was to use very long booms set at minimal angle to the current (as much angle as possible without straining the gear or creating turbulence under the boom), while allowing any wave action.

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Whangamata marine oil spill deployment exercise [PDF, 3.6 MB]