SALINITY AND DISSOLVED METHANE CONCENTRATIONS IN HOMEONER WELLS PRIOR TO HYDRAULIC FRACTURING

Groundwater samples from (n=203) domestic landowner wells were collected across Broome, Chemung, Chenango, Steuben, and Tioga counties to determine baseline groundwater quality in the Southern Tier of New York State. Results indicate that dissolved methane at low concentration is common in drinking water wells; 13% of homeowner wells had relatively high concentrations of methane (> 1 mg/L) and 7 wells had actionable levels of methane (> 10 mg/L). Groundwater geochemical type and the bedrock unit of completion were better indicators of elevated dissolved methane concentrations than landscape position (i.e. upland versus valley) or proximity to faults and/or lineaments. Isotopes of methane and strontium were used to determine if natural migration of methane and/or formation brines, respectively, were probable sources in domestic wells. Stable isotopes of CH₄ (¹³C and ²H) were used to determine if the dissolved methane was more likely thermogenic or biogenic. The ^86/87Sr data were used to assess the likelihood of mixing of shallow groundwater with Marcellus formation water. ^86/87Sr in water samples ranged from .710 to .713 similar to published ^86/87Sr values for produced waters and Marcellus formation water. As a result, ^86/87Sr may not be a good indicator of formation brine migration to domestic wells as a result of future hydraulic fracturing in New York.