The natural gas mining method known as hydraulic fracturing or "fracking" is another major source of water usage and a serious source of contamination. The EPA estimates one well in a coal bed can require anywhere from 200,000 litres to more than 1 million litres while a horizontal well in a shale formation can use between 7.5 million to 19 million litres of water.
The EPA estimates anywhere from 15 to 80 per cent of water is recovered. There are several ways of disposing of the water used in the process. It can be stored underground in impermeable injection wells that prevent it from leaking into the environment or in steel tanks or pits; recycled for use in another fracturing well; or treated and discharged back into the water supply. Because of its high salt content, the waste water is often also bought by municipalities for use in de-icing and dust suppression on roads.
Although the fluid used in fracking is mostly water, some acids, emulsifiers and other chemicals are added to make the water more viscous and effective at fracturing the rock. These include guar gum, boron, zirconium, titanium, iron and polyacrylamide.
