High-resolution, terrestrial laser scanning, also known as ground-based lidar (light detection and ranging), was used to quantify the volume of mercury-contaminated sediment eroded from an outcrop of historical placer-mining debris at the confluence of the South Yuba River and Humbug Creek in the Sierra Nevada mountains, about 17 kilometers northeast of Grass Valley, California. The outcrop could not be mapped non-destructively or in sufficient detail by traditional surveying techniques. Terrestrial laser scanning was used to produce centimeter-scale, three-dimensional maps of the complex outcrop surface at the study site, which was approximately 70 meters long, 30 meters wide and 20 meters high. The outcrop surface was composed of an upper erosional area (cliff area) and a lower depositional area (colluvial slope). The study site was surveyed four times in 2 years (December 15, 2011; October 25, 2012; January 4, 2013; and November 22, 2013). For each survey, the upper erosional area and a lower depositional area were isolated and separated so that volumetric comparisons could be made.