The salt settlement tanks are the second filtration process that the estuary water meets after being pumped from the barge.  Having been pumped into the primary filter tanks allowing plankton and sea animals to be sieved out, the water is pumped into the secondary tanks or 'settlement tanks' and left to do exactly what the name suggests - 'Settle'. The process allows dirty and sand to drop to the bottom of the tank whilst free from impurity water can be released into the salt pans.