Sea water is pumped into Lake Grassmere’s main lake (700 hectares), which has no stopbanks. When the water reaches twice its normal salt content, it is pumped into a series of preliminary concentration ponds (500 hectares) and then into final concentration ponds (80 hectares). Four deep storage ponds (20 hectares) hold the strong brines over winter. The following spring these brines are pumped back into the concentration ponds. After two or three years of this cycle the brine is strong enough to be pumped into the crystallisation ponds (93 hectares) from which the salt is harvested. The reconcentration ponds (40 hectares) are used for bringing rain-diluted brine back to full strength, and the wash ponds (8 hectares) are used for washing the salt after harvest and for rewashing stockpiled salt during refining.