Obscure Box

Thoughts from inside the obscure box

January 25, 2012

How much oil was spilled in the Brisbane River?

Posted by : Michael Lund
Filed under : Media, Observation, Radio

If you were listening to the ABC's PM program last night then its report would have made you think it was an even more catastrophic event than it was in the first place.

See this line from reporter Imogen Brennan in "Environmental concerns after oil spill in Brisbane River" (Tuesday 24 January 2012).

IMOGEN BRENNAN: Five thousand tonnes of oil spilled into the Brisbane River yesterday morning, when a cargo ship was being refuelled by another boat.

How much?

The oil was lost when the live animal cargo ship GL Lan Xiu was being refuelled by the vessel Valiant III, at Hamilton Number 4 Wharf, according to a statement by Maritime Safety Queensland.

Various online databases of international shipping - such as MarineTraffic.com - record the actual dead weight tonnage of the Panama registered vessel at 3,254 tonnes - that's the actual amount it can carry.

So any attempt to load 5,000 tonnes of oil would have done more than cause the environmental damage already concerning authorities and environmentalists. It would have probably sunk the vessel too.

How the ABC came to report that "five thousand tonnes of oil was spilled" is a valuable lesson in Maths for Journalism.

Back to that statement "Maritime Safety Queensland responding to small oil spill" (Tuesday 24 January 2012) which reports a more modest estimate of the amount of oil lost.

About five tonnes of fuel oil spilled during a ship refuelling operation at Hamilton Wharf this morning shortly after 6.45 am.

Later the same day it issued another statement "Oil spill response continues" which gives details of the oil clean up, this time in litres.

About 16 000 litres of oily water was recovered yesterday, with another 10 000 litres of oily water recovered this morning.

So the confusion probably comes from somebody reading both statements, noticing the numbers but not the different unit of measurements.

It's something I always stress in lectures I've delivered on Maths for Journalists. Always double-check any numbers and the units, and always make sure you are comparing like with like.

Another thing I always stress is to have some familiarity with the numbers you report on, and if you don't have that familiarity then find out, so you get a feeling for when something doesn't add up

For the record, one litre of water weights one kilogram, and 1,000 litres of water weights one tonne. That means 5,000 tonnes of water would equate to about 5-million litres and that's enough to fill two Olympic sized swimming pools.

Okay, so oil is lighter than water - that's why it floats - but the figure would be too different for oil.

Would a ship really be loading that much oil?

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All thoughts and comments here are the honestly held personal opinion of Michael Lund and are based on the information available at the time of publication.