Other contaminants are lighter than water and float on top, such as petroleum products like jet fuel and gasoline. Locating the contamination can be difficult. The ability of technology to find contaminants in ground water is limited. Samples from ground water wells do not always provide enough information about the extent of ground water contamination. Other devices for detecting contaminants and identifying variations in the underground rock and soil can also help, but only to a certain degree.
Technology has limitations.
Treatment technologies are limited in their ability to clean up an aquifer, even if the location of the contaminants is known. Frequently, ground water is cleaned by pumping it to the surface for treatment. After contaminants have been removed, the water is discharged back into the ground or to a stream or river. Even then, some contamination remains in the aquifer, which can continue to contaminate the ground water. Contaminants that cannot be pumped to the surface with the water must be treated underground, making cleanup more difficult, expensive, and time consuming.