Salt ponds & salt pans

In solar salt production, brine moves through a series of shallow ponds. In the concentration ponds the sun evaporates water until the brine is close to saturation; in the crystallisation ponds the salt settles out and is harvested. An HDPE liner stops brine seeping into the ground, protects the soil and groundwater around the works, and keeps the salt away from the soil beneath.

Ponds we line

Concentration (evaporation) ponds
Crystallisation ponds
Brine storage and feed ponds
Brine ponds at desalination and industrial plants

RO reject and desalination brine ponds

Built for salt, heat and UV

Salt does not attack HDPE. Manufacturers' chemical-resistance tables rate it as little or not affected by salt water and by sodium, calcium and magnesium chloride. What shortens the life of an exposed liner is sun and heat. Specify HDPE to GRI-GM13, which requires 2–3% carbon black and a UV resistance test for each formulation, and lay out the panels and anchor trenches for the daily expansion and contraction of black sheet in the Saudi sun.

Protecting the liner during salt harvesting

Harvesting is when most damage happens. Good practice:

Keep a layer of salt (a salt floor) over the liner in crystallisation ponds, as the pond design specifies, so harvesting equipment works on the salt and not on the sheet
Build ramps and access routes so machines never cross exposed liner
Add a protection layer where the design calls for one
Inspect after each harvest and repair damage with extrusion-welded patches before it spreads

Testing and QA/QC

HDPE to GRI-GM13 with manufacturer certificates
Trial welds before production welding each day
Vacuum box and spark testing; peel and shear tests on site
Seam, test and repair records at handover

Frequently asked questions

Why line a salt pond instead of relying on a clay floor?

A natural clay floor only works where the ground is tight enough to hold brine. Where it is not, brine is lost by seepage and the ground beneath becomes saline. A welded HDPE liner makes the pond watertight whatever the soil, and gives a clean, known surface under the salt.

What liner thickness is used for salt ponds?

Thickness follows the design, the pond size and how the salt is harvested. Exposed industrial ponds in the Kingdom typically use 1.5 mm or thicker HDPE. In crystallisation ponds harvested by machine, the liner needs a salt floor or a protection layer over it, whatever its thickness.