These are valuable, large storage depots for the many chemicals used in oil drilling, fracking, and plastic manufacturing. Texas Brine rents six caverns. Dow and Union Carbide owns others into which they have pumped fifty million gallons of ethylene dichloride (EDC). While it surprised me to learn how far down into the earth free enterprise went, such underground storage systems have long been accepted practice in the Gulf region; the National Petroleum Reserves have themselves long been stored in a similar way.
