Response team Incident Controller Graeme MacDonald says searchers – aided by spotters in a hired civilian helicopter – today once again concentrated their efforts in an area about eight nautical miles east of the Poor Knights Islands.
Working with the Navy vessel Manawanui, the searchers had by 4.30pm today recovered another 10 packages, bringing to 23 the total number recovered in the past 24 hours.
To date, it appears no packages have washed ashore on any of the islands in the Poor Knights group, or on the east coast of Northland itself. Mr MacDonald says an estimated 20 degrading packages may still be at sea, probably within a 400 square kilometre area.
The chemical at the centre of the search is used to fumigate ships and two Tauranga-based chemical experts have been based on the Manawanui for the past two days lending their expertise to the recovery programme.
Mr MacDonald says those experts have calculated a large (approximately 45,000 tonne) merchant vessel would typically use about 30 to 45 packages of the chemical at a time, a figure that ties in with the approximately 40 packages spotted at sea by a searching Air Force Orion on Sunday.
Magnesium phosphide produces a poisonous gas on contact with moisture and in cases of serious exposure can lead to increasing chest tightness, breathlessness and collapse.
Tests on the last few packages recovered today were unable to detect any gas, although earlier small, non-harmful levels of gas were still being emitted by some.
Mr MacDonald says after discussion today with the chemical experts, health, Department of Conservation, iwi and other agencies, the Whangarei-based team heading the recovery effort now considered the remaining packages pose little risk to either humans or the environment.
“This is due to a combination of factors. These include the properties of the chemical involved, the fact gas is no longer being detected, the deteriorated state and long time these semi-permeable cardboard bags have now spent in the water and the costs and staffing resources involved.”
‘When all these factors are considered together, a decision was made to stand the Manawanui down once it has returned to Marsden Pt with the recovered packages. It is expected to arrive there at about 8pm today and the material recovered will be unloaded and taken to a secure land-based hazardous chemical storage area at Marsden Pt.”
Mr MacDonald says contingencies remain in place should the recovery of more packages prove necessary over the next few days.
He says although exact figures have yet to be tallied, the costs of working to identify and recover the packages over the past several days would already have run to tens of thousands of dollars.
However, despite their belief the risk had now reduced considerably from when the first packages were encountered by boaties at the weekend, officials are still advising anyone encountering the bags not to approach them, or try to recover them.
The packages are orange flat cardboard tubes, approximately two-metres long, 150mm wide and 25mm thick. “People coming across one of these packages should telephone 111 immediately and advise the Fire Service, which will arrange for its safe removal. Alternatively, boaties encountering packages should report them to the Northland Regional Council’s 24-hour Environmental Hotline 0800 504 639.”
Mr MacDonald says some of the packages retrieved today came after sightings reported by passing boats.
The Maritime Safety Authority is today continuing its investigations into how the packages found their way into the sea and is following a number of positive leads.