In 2010, the U.S Geological Survey (USGS), in cooperation with the Wind River Environmental Quality Commission (WREQC), began an assessment of the effectiveness of the existing monitoring network at the Riverton, Wyoming, Uranium Mill Tailings Remedial Action (UMTRA) site. The USGS used existing data supplied by the U.S. Department of Energy (DOE). The study was to determine (1) seasonal variations in the direction of groundwater flow in the area of the former uranium processing facility toward the Little Wind River, (2) the extent of contaminated groundwater among the aquifers and between the aquifers and the Little Wind River, (3) whether current monitoring is adequate to establish the effectiveness of natural attenuation for the contaminants of concern, and (4) the influence of groundwater discharged from the sulfuric-acid plant on water quality in the Little Wind River.