MAPPING ACID MINE DRAINAGE AT AN ABANDONED MINE SITE IN OTTAWA COUNTY, OKLAHOMA USING 3D ELECTRICAL RESISTVITY TOMOGRAPHY

The Park Walton Mine is an abandoned mining site in the western portion of the Picher Mining District, Ottawa County, Oklahoma. The site was mined for lead and zinc ores in the 1940s and 50s. Today, a 40,000 m² area is covered with waste rock and fine tailings discarded at the site as part of the mining process. Three vent shafts are present that extend into mine voids located approximately 120 m below ground surface. The vent shafts discharge water contained in mine voids to the surface during times when the underlying aquifer is overpressured. No data exist regarding heavy metal contamination at the site or the extent to which heavy metals have mobilized off-site. The present study was aimed at assessing the extent to which the shallow subsurface at the site is contaminated with acid mine drainage products using 3D electrical resistivity tomography. Electrical resistivity surveys are commonly applied to acid mine drainage studies because the products of acid mine drainage (SO₄^2- , H⁺, metal ions) cause affected waters to be highly conductive to electrical current. Initial inversion results indicated conductivity anomalies in the shallow subsurface related to fluid flow associated with contaminant transport away from the waste rock pile and vent pipe discharges. Results from this study provide insight into the hydrodynamics at the site and will be used to plan future contamination surveys and mitigation efforts.