Nevada Division of Environmental Protection, Las Vegas. 209 pp, 2017

This technical memorandum describes the results of the geophysical pilot test (GPT) conducted for the remedial investigation of the downgradient study area located in Henderson, Nevada. The overall objective of the investigation was to identify subsurface pathways within the downgradient study area through which perchlorate-impacted groundwater enters the Las Vegas Wash (LVW). The location of paleochannels and other potential preferential flow pathways is important to the understanding of perchlorate mass flux to the LVW outside the study area. While limited geophysical surveys have been conducted in the area, uncertainties remain as to the locations of these channels in the vicinity of the LVW. The GPT consisted of evaluating three geophysical systems, including the feasibility of employing the systems under constrained access conditions, costs, and their effectiveness at identifying the top of the Upper Muddy Creek formation and paleochannel geometry. The GPT results will serve as the basis for the forthcoming plan to select the optimal approach for a full-scale geophysical survey of reaches of interest along the LVW within the downgradient study area. https://ndep.nv.gov/uploads/env-sitecleanup-active-bmi-nert/geophysical-pilot-test-2017.pdf