As FuelBoy mentioned, 1/2 a ton(!!!) is not an acceptable amount. To put it into context, 1/2 ton is approx 600 ltrs, here in the real world any spillage over 100 ltrs has, I repeat, HAS, tobe reported to the Environment Agency as a serious spillage. I am not involved with aviation, but from what I have read on these forum the industry is severely lacking in Health, Safety and Environmental awareness in this area. Everyone here seems to dismiss fuel leakage as an everyday event, would you say that if you were driving down the high street with every other car that passed you by leaking petrol, passerbys smoking, electrical sources as you walk by the lampost etc etc. Are there no incident investigations when this happens? Is it continually ignored? One day it will turn around and bite. People may say I'm exaggerating, but Buncefield was caused by a series of two or three failsafes failing, so it DOES happen!