Potash evaporation ponds At the Intrepid Potash Mine in Moab, Utah are blue ecaporation ponds. It produces a salt that is used by farmers as fertilizer. The salt is pumped to the surface and dried in solar ponds in 300 days. The water is dyed blue to reduce the amount of time it takes fot the potash to crystallize. Darker water absorbs more sunlight and heat.