In the instance of contamination in Colorado, the contamination was due to human error. The company operating the well did not case the well properly. When they attempted to fracture a tight sand formation 7,000 feet below the surface, the
protective well casing failed, and they instead contaminated groundwater 3,500 feet away through a shallower fracture system. After the incident, a report was commissioned by Garfield County to explore the hydrology and geology of the region and to “assess the vulnerability of surface water and ground water resources in the area to impacts from natural gas well-development and other human activities and to evaluate if a relationship exists between water quality variations
and lithology type.”30 Benzene was found in some of the samples, but not in the domestic water wells. Along with methane, which they were not able to definitively source from the natural gas wells, they found increased levels of chloride, fluoride, nitrate, selenium, iron, and manganese.