Exploring controls on halogen and methane occurrence in groundwater of New York State

Abstract The expansion of unconventional oil and gas development (UOGD) by means of horizontal drilling and high-volume hydraulic fracturing has been accompanied by concerns regarding the potential impacts to water resources and public health. The ban on UOGD in New York State (NYS) allows natural processes that control groundwater chemistry and dissolved methane to be evaluated without complications that could arise in regions impacted by prior unconventional shale gas development. We evaluated the controls on the occurrence and spatial variability of methane, chloride, bromine, and iodine, covering much of NYS and encompassing a range of underlying bedrock geologies. Groundwater samples were collected from 108 domestic and public supply wells. Methane concentrations in groundwater ranged from