Discharge waters from coal-bed methane mining near Gillette, Wyoming have a high electrical conductivity (EC) and sodium content (high SAR). This water has been discharged on soil, causing elevated exchangeable Na contents (high ESP) and EC values to these soils. Our purpose was to characterize the extent of soil alteration, including the accumulation of Na and the effects that Na has on the soil fertility and other selected chemical and physical properties. Impacted areas have sufficient sodium accumulation to classify them as saline - sodic soils, reducing their agricultural values. The soils are Mollisols with substantial clay (montmorillonite) content. Unimpacted soils similarly have appreciable EC and ESP contents, although less than impacted areas, a feature attributed to the sodic shale parent materials. Gypsum amendments promote cation exchange reactions that alleviate the electrical conductivity and soil SAR values, promoting the regrowth of the range plants.