Evaporation ponds are an integral part of most oil and gas industry sites today because they offer an affordable solution for the need to process and control both the production water required to flush oil and gas out of underground reserves and the flowback water that is generated from such extraction. The water that naturally surfaces during oil and gas extraction is known as “production water.” It may contain various minerals and hydrocarbons, some of which are possible carcinogens, or it may also contain radioactive debris. Retained oil in the production water makes it easily flammable, posing another risk. Flowback is the term applied to the fluid that routinely returns to the surface after it is injected into a well for the hydraulic fracturing process. Between 20 and 40 percent of that fluid is returned to the surface; it is water-based, but murky, and contains a mixture of chemicals, clay, dissolved metal ions and other semi-solids.
Because these are extremely hazardous byproducts of the oil and gas industry, a multi-step process is used to isolate and properly dispose of them. The fluids are first directed to an “acceptance pit,” where they are stored pending transfer to settlement pits. During this phase, oil is separated from the watery solution. The next step is a sludge pond, in which hydrocarbons typically float to the top where they can be mechanically skimmed and removed. Finally, any remaining water is channeled into evaporation ponds, either by gravity or piped directly from the separation chambers. Enough contaminants generally remain to require double layers of liners, sometimes separated by a layer of clay with leak monitors in place. The hazardous waster is secured by the impermeable modern lining material, and great care is taken that none escapes to harm the environment. Additional stringent requirements protect oil and gas workers from harm.
