Seepage Chemistry at Yellowtail Dam-A Geochemical Evaluation of Reservoir and Seepage Water and a Bacterial Residue Collected at Yellowtail Dam, Pick-Sloan Missouri Basin Project, Montana

摘要

During 2005, a brown slimey deposit was observed collecting at some of the drain outfalls in the Foundation Gallery at Yellowtail Dam, Montana. These drains intercept foundation seepage moving through collapsed breccia layers in the Madison formation limestone (Jepsen and Witherspoon, 1948), so there is an interest in establishing whether mineral dissolution or erosion is occurring along these seepage flow paths. Samples of the slimey deposit were collected in November 2005, and the material was tested and evaluated by Doug Hurcomb, geologist, 86-68340, (Hurcomb, 2006). Hurcomb concluded that the material was bacterial, likely composed of several species of iron bacteria with minor amounts of sediment particles entrained in the biological matrix. Water samples were also collected by Jeff Lucero, GP-4500, Great Plains Regional Office, Billings Montana, in November 2005, and were analyzed by Basic Laboratory, Redding, California. A full laboratory quality control (QC) report was provided with each set of chemical analysis results, and Lucero provided an assessment of the data by email on February 10, 2006.