Deep-Well Injection is the disposal of liquid waste through layered steel pipes that empty thousands of feet below the earths surface. Liquid waste is injected into porous rock under several layers of impermeable rock layers to prevent contamination of fresh water aquifers. The depth of the well depends on how hazardous the waste is.
This method is not the same as fracking. Fracking involves the fracturing of rock deposits in order to extract oil or gas.