Dampier Operation is Dampier Salt's biggest operation with a total operating area of over 10,000 hectares.

Dampier's salt production process begins with seawater being pumped into the first pond, Pond Zero, before undergoing progressive concentration by evaporation as it flows through successive concentration ponds. In the sixth pond, the brine reaches the "salting" point (sodium chloride saturation). At this stage it has been reduced to 11 percent of its original volume and has deposited most of its calcium. Sixty five tonnes of seawater are pumped in for every tonne of product salt. Dampier's current evaporating areas are sufficient to produce four million tonnes of a salt a year.

The saturated brine is pumped into crystallising ponds where further evaporation occurs and salt is deposited on top of a pre-formed floor of salt, which acts as a pavement for the harvesting equipment. Deposition is stopped when about three quarters of the sodium chloride has been deposited and before other dissolved salts come out of solution in significant quantities. The residual brine called bitterns contains high concentrations of potassium, magnesium and other salts and is a potential source of these minerals.

Each crystalliser is harvested once a year. Salt is removed from the drained crystallisers by mechanical harvesters and is fed directly into trucks comprising of a prime mover and two bottom dump trailers carrying loads of 120 tonnes. The harvester units, which are specifically built to Dampier Salt's requirements, harvest at a continuous rate exceeding 1,600 tonnes per hour. GPS level control equipment enables accurate control of harvester cutting depth, leaving an even surface the next year's growth of salt.

To ensure high quality salt with minimum impurity levels the salt is washed immediately after harvesting. Trucks dump the freshly harvested salt into the wash plant hoppers. The wash plant has a peak capacity of 1,200 tonnes per hour. The counter-current washing technology has been developed in-house by Dampier Salt engineers to produce lower impurities and a directly shippable product with minimal washing losses.

After washing, the product is conveyed to the 600,000 tonne product stockpiles at Dampier Salts port facility of Mistaken Island. Product salt can also be sent for direct shiploading.

The salt is reclaimed for shiploading by dozers and front-end loaders which feed the salt to a conveyor system under the stockpile. The shipping berth can accommodate vessels of up to 100,000 Dead Weight Tonnes (DWT). A fully equipped laboratory maintains stringent quality control to ensure only the highest grade of salt is produced.

Process overview

Salt field data
Current production capability 4.2 million tonnes/year
Average evaporation (fresh water) 3,400 mm/year
Average shiploading rate 2,500 - 3,000 tonnes/hour
Length of levees and causeways 112km
Average evaporation of field 420,000 tonnes water/day
Peak ship loading rate 3,300 tonnes/hour
Average rainfall 255 mm/year
Salt deposited in crystallisers 270 mm/year
Berth depth at low water 12 metres
Total operational area 10,014 hectares
Peak evaporation of field 1,000,000 tonnes of water/day