Wastewater disposal is among the biggest challenges of fracking. Although up to 85 percent of fracking fluid remains underground, the wastewater that does return to the surface (also called "flowback water" or "produced water" or "brine") is contaminated and must be treated and disposed of. This liquid waste is frequently stored temporarily in open pits, or "misted" into the atmosphere. There are several options for permanent disposal of wastewater: (1) trucking to an industrial wastewater treatment facility; (2) trucking to injection wells deep underground; (3) reuse by recycling into another frack job. Each option has multiple environmental risks.