Understanding Bedrock Fracture Flow to Improve Groundwater Quality

Abstract

The goal in this project was to gain an improved understanding of groundwater flow through fractured limestone bedrock by using recently developed techniques. We focused on the Platteville Formation in the Twin Cities Metropolitan area, where the formation is one of the most heavily contaminated bedrock layers in the state. There were two primary activities. One was collection of a variety of geologic and hydrologic information from monitor wells. This was accomplished at two sites near the Mississippi River in Minneapolis; on the campus of the University of Minnesota, and near Minnehaha Falls. We used recently developed techniques that included borehole geophysical testing and instrumentation with multiple pressure and temperature sensors. Two monitor wells at each site were instrumented with sensors. A second activity was detailed mapping of fractures at an exposure of the Platteville Formation at the UMN campus site. Determining how water travels through the Platteville is achieved by combining the results of these two activities.