Brine water is a byproduct of extracting oil and gas from underground. The brine water sits underground mixed up with the oil and gas, and comes up when the oil/gas in extracted. Companies have some options for disposing of the brine water (or produced water) that can contain radioactive compounds, methane and other substances - that have been trapped for thousands of years underground. They can put in open air pits (some states don't allow this), they can inject back underground or they can recycle it to use in their operations (fracking, secondary recovery water injection, etc). The industry says disposal of this water is done safely, I wonder if these residents of Louisiana think that big sink hole is safe, the insurance companies that are canceling their homeowners policies don't seem to think so.
There are these types of injection wells in VC and throughout California.