The Trona Plant is the oldest. Over the years many changes were made to the Trona Plant with new plants constructed and others that were no longer profitable shut down. Primary borax from the Westend Plant is also refined into anhydrous borax and decahydrate borax. The Westend Plant is the second oldest operating chemical plant, starting operation in 1925 with the production of soda ash and borax. In 1955 sodium sulfate was added.
Chemical extraction is based on brine carbonation and regrigeration.
Production has been expanded several times, most recently in 1996 with the start of a new lake mining operation based on new techonolgy. The Argus Soda Ash Plant is the newest chemical extraction plant, starting operaton in 1978. It is the largest soda ash plant in the world using a process based on the carbonation of natural soda ash brines. This is separated from the brine by filtration, with the bicarb then being heated to convert it to crude soda ash. Recrystallization to purify it and final drying complete the process.