Eighty percent of the United States’ produced water, high salinity water from oil and gas formations brought to the surface during extraction processes, is generated in states west of the 98th meridian and frequently discharged to surface waters through the National Pollutant Discharge Elimination System (NPDES). Studies on produced water disposal in Pennsylvania found elevated sediment NORM downstream of NPDES facilities accepting oil and gas wastewater, compared to background levels. Recent radium studies lack a focus on Western states where surface disposal of oil and gas produced water is more commonly practiced and beneficial reuse permit exemptions for irrigation and agricultural livestock watering allow minimal treatment prior to surface disposal. In Wyoming alone, approximately 600 oil and gas NPDES facilities are permitted to discharge produced waters to streams. Water and sediment grab samples were collected during two sampling events in 2016 at 26 sites along two perennial rivers and one ephemeral tributary in a remote region of Wyoming. Sites sampled include both upstream and downstream of seven NPDES discharge facilities. Statistically significant increases were determined for sodium, sulfate, chloride, and calcium downstream from discharges. Sediment samples at the point of discharge were elevated in radium 226, with one facility as high as 23 pCi/g. Though these radium levels are much lower than in Pennsylvania, they are elevated above the 5pCi/g action level threshold set by EPA and pose important considerations from a human health and environmental standpoint as to what elevated NORM levels mean for stream health and bioavailability in aquatic systems. Additionally, sediment push tube cores were collected at five discharge facilities and analyzed in 4 cm intervals for radium 226 and 228. Interestingly, radium 226 levels peak at a depth of 10-20 cm creating implications for future radium sampling methods and capturing the entire extent of radium contamination.

Investigating enhanced sediment radium levels at NPDES facilities in Wyoming with a comparison to Pennsylvania

255th National Meeting (2018)

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