The water that returns from fractured wells, both the water that is injected to fracture the well and the water from the formation itself carries with it substances that can be harmful to human health and the environment. These substances include chemicals from the hydraulic fracturing process and the compounds formed from their interactions with each other and reactions with substances present in the Marcellus formation itself. Water present in the Marcellus formation contains heavy metals and radioactive materials, volatile organic compounds and high levels of total dissolved solids, mostly salts. Instances of contamination of groundwater by some of these compounds have been documented in other areas of the country