WATER QUALITY SURVEY OF SALINE SPRINGS THAT RIM THE WILLISTON BASIN

Water quality in areas of oil and gas production is important for addressing environmental and public health concerns. The Williston basin in North Dakota and Eastern Montana has extensive oil and gas production, but little publically available water quality assessments. There are numerous saline springs that rim the basin. Hyper saline basin brine from depth may mix with shallow groundwater and affect water quality. This study sampled springs and some shallow groundwater in the basin to test for basic water quality parameters and for evidence of basin brine discharge. Water samples were collected throughout the Williston Basin (August 2015). The sample locations spanned an area that extended from the center of the basin to the far eastern and western edges. Samples were selected for laboratory analysis based on initial in-situ measurements of electrical conductivity and pH. The source and quality of the water was determined using alkalinity, isotopes, anion ratios, and metal ion concentrations. Initial laboratory analysis did not indicate that there is evidence for “older” deep brine waters based on chloride to bromide ratios that ranged from undetectable levels to 4.523 mg/L. These results are indicative of “younger” waters that were discharged from a relatively shallow hydrologic flow system. Water quality varied across the basin with several locations showing high concentrations of SO₄ (up to 2708.20 mg/L) and elevated levels of trace metals. As a result of these findings additional inquiry focused on possible explanations for high concentration of SO₄ throughout the basin.