White River, UT Seep Geophysical Surveys and Assessment
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Complaints and observations have been received by the Utah Department of Environmental Quality and EPA Region 8 concerning a black ooze along the bank of the White River and suspected association with local natural gas extraction wells. Prior investigations of the water quality reveal no hydrocarbon constituents, elevated electrical conductivity and thermal response. No investigations had been done to characterize the subsurface representation of these seeps and assess their subsurface correlation.. The objective of this project was to geophysically assess the subsurface representation and potential source of the black material visually evident along a bank of the White River south of Vernal, UT. Surface frequency domain electromagnetic induction and electrical resistivity tomography surveys were performed with data collected over a two day period. Results indicate a deep subsurface geoelectrically resistive feature trending northwest to southeast with a high electrical conductivity surface presentation. The strike of this resistive feature is in agreement with known gilsonite veins. Support from prior surface investigations indicate the high electrical conductivity surface feature is likely due to biogeochemical reactions under oxic conditions interacting with fine grained gilsonite material. We conclude the geophysical surveys imaged a deeper gilsonite vein that is being altered at the surface through biogeochemical interactions driven by geothermal upwelling through the gilsonite vein. These surveys suggest the source of the black material at this seep along the White River is likely naturally occurring gilsonite.