Stream Macroinvertebrate Surveys for Stibnite Gold Project, Stibnite-Yellow Pine Mining District

EcoAnalysts has conducted annual macroinvertebrate surveys since 2014 in the East Fork of the South Fork of the Salmon River (EFSFSR) and selected tributaries as part of an aquatic resources baseline study prior to the start of proposed mining operations at the Stibnite Gold Project in central Idaho.

The project, proposed by Midas Gold, Inc., is located in the Stibnite-Yellow Pine Mining District near Yellow Pine, and lies within the Salmon River Mountains near the Frank Church River of No Return Wilderness. The mining district is administered by the Krassel Ranger District of the Payette National Forest (PAF). The terrain within the project area consists of narrow valleys surrounded by steep mountains. Elevations range from 6,000 to 6,600 feet above mean sea level along valley floors to more than 8,500 feet above mean sea level in the surrounding mountains. The EFSFSR is the main drainage basin in the project area.

The purpose of this survey is to evaluate stream health and water quality based on macroinvertebrates found at the sampling sites, and to allow future repeatable studies that can track any changes to habitat conditions that may result from mining activity. Species composition and abundances at each site are used to calculate quantitative measures of biological condition (metrics) that are based on habitat preferences, feeding strategies, water-quality tolerances, and expected occurrences of different macroinvertebrates. The magnitude and variation in these metrics provide useful information for understanding the water quality and habitat characteristics of streams in the project area which EcoAnalysts reports on annually for this client.