The U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, is investigating the distribution of saline groundwater in the Genesee River Valley near the former Retsof salt mine (fig. 1). As part of this study, paired time-domain electromagnetic (TEM) soundings and horizontal-to-vertical spectral ratio (HVSR) seismic soundings were made at 39 locations during the fall of 2016 to determine the presence of saline groundwater and depth to the bedrock surface, respectively. All measurement sites were west of Geneseo, New York, on the Genesee River valley floor north and south of the sinkhole area that developed as a result of the roof collapse and flooding of the Retsof mine in 1994 (fig. 1). An integrated analysis of the TEM and HVSR soundings with borehole logs, coupled with groundwater-sample data from previous investigations, allowed the delineation of zones of high electrical conductivity associated with saline water in the lower part of the valley fill and underlying bedrock to depths greater than 1,000 feet (ft). This article describes the TEM sounding method and its application in the ongoing investigation, presents results of the TEM analysis at two of the sounding sites, and identifies proposed sites for additional TEM/HVSR sounding data collection during the fall of 2017. Supporting data for this study are available in a separate data release (Johnson and others, 2017).