Posted By Malcolm Fryer Hi I would not claim to be fully competent in this area but would comment that visual inspection will normally reveal any tell tale signs of integrity failure. Pesonally i am a great fan in the case of outside bunds of looking after heavy rain to see if the bund holds water. Whilst exterior bunds are a nuisance from the cleansing point of view if they don't hold a little water then you probably have a problem. Hydraulic test? Well the tank would need to be virtually empty whilst you filled the bund and then monitored loss. In addition you would then need to tanker away the hazardous waste. Hope this assists. Malcolm