How much pollutant escaped into Warabrook Lagoon?
70 The Prosecutor argued that a large amount of egg waste had escaped from the black tank, possibly over many hours. The time at which the leak from the black tank commenced is unknown. The evidence of Dr Staniland that he was told the last truck left the loading bay area at 3.00 pm on 2 October 2003 is more specific than the evidence of Mr King that trucks generally used the loading bay area until midnight. Mr King did not have specific knowledge of truck movements on 3 October 2003. Accordingly, the relevant time period in which the leak could have occurred is between 3.00 pm on 2 October 2003 and 5.45 am on 3 October 2003, a period of up to 14 hours. The capacity of the black tank is approximately 6,830 litres and Mr Fitzpatrick pumped approximately 2,000 litres from the black tank. However, the amount which leaked from the black tank is unknown with the upper limit being 4,830 litres, given the tank's capacity.
71 The Prosecutor relied on Dr Joliffe's evidence, which was disputed, that the estimated volume of pollutant that escaped into Warabrook Lagoon was between 1,000 and 4,000 litres based on photographs of the plume. As Dr Joliffe stated in his report and in oral evidence this was a very difficult calculation to do with any certainty in the absence of any information about the flow rate and time of flow. Dr Staniland gave evidence which criticised Dr Joliffe's evidence in this area as lacking any scientific basis. I do not accept this part of Dr Joliffe's evidence as proving that the possible amount of pollution that escaped into Warabrook Lagoon was between 1,000 and 4,000 litres, rather his evidence should be considered speculative. I note that Dr Staniland estimated that based on the experiments he conducted the amount could be as little as 20 litres. The amount of pollutant in Warabrook Lagoon is essentially unknown in my view of this evidence.
72 The respective civil engineers gave their opinion in relation to the flow rate of the leak from the black tank and therefore the time over which the leak took place, and the likely time liquid of the nature of egg waste would take to flow to SW4 and/or SW6 and then to the GPTs and Warabrook Lagoon.
73 The evidence of Dr Joliffe was that, in his opinion, it would take 35 hours for the egg waste to drain through a 5 millimetre hole in the black tank if the tank was half full, and 55 hours to drain if the tank was full. Dr Staniland agreed with Dr Joliffe's evidence in relation to a hole 5 millimetres in diameter. Dr Staniland considered, however, that the hole in the black tank was probably 3 millimetres in diameter at the time of the leak and he calculated that the drainage rate for a hole of 3 millimetres would be 35 to 40 per cent of the drainage rate for a hole of 5 millimetres in diameter. Assuming the hole was 3 millimetres in size, Dr Staniland estimated that it would take approximately 160 hours for the black tank to drain if the tank was full. Both the experts' evidence suggests that if the leak was from a full to half full tank, it should have been obvious sometime during the day on 2 October 2003 or earlier. I consider Dr Staniland's conclusion that the hole in the tank was smaller at the time of the leak is likely. This also suggests it is likely the leak was not as large as suggested by Dr Joliffe's estimate of 1,000 to 4,000 litres.
74 The evidence of Dr Staniland suggests that the amount of the leak must be over 300 litres, that being the amount Dr Staniland estimated would fill the void under the cement next to the tank. Some additional material would then flow beyond SW1 to SW4. He estimates that the liquid would take eight to eleven hours to travel beyond SW1 to SW4, given the viscosity of the egg waste solution.