Karst Characterization of the Marshall Space Flight Center: Two Years Later

The Marshall Space Flight Center is a 688 hectare (1700-acre) NASA facility located in a karst prone area of northern Alabama. In 2005, a paper was presented at this conference discussing the local and regional karst investigation completed utilizing extensive surface and borehole geophysical techniques. The purpose of the surface and borehole geophysical investigation was to potentially identify significant karst features (conduits, dissolutioned fracture zones, cavities, etc.) and increase the opportunity for placing deep bedrock borings in areas of groundwater flow. This effort included the integration of geophysical measurements with existing well and boring data along with regional geologic information. Geophysical measurements included microgravity, multi-channel analysis of surface waves (MASW), and geophysical logging. The use of multiple geophysical methods provided supporting datasets with overlapping depths of investigation. The integrated geophysical approach to the karst characterization allowed multiple geologic variables to be assessed simultaneously with a greater level of spatial sampling than borings alone. Anomalous conditions identified in the geophysical data that correlated with other supporting data guided the location of deep bedrock borings. This current paper provides follow-up to the karst investigation previously completed presenting the results of an extensive drilling, testing and sampling program. The bedrock wells were used to acquire a suite of downhole measurements that advanced the characterization of the hydrogeologic setting at the site. The suite of measurements included geophysical logging, acoustic and optical televiewer and hydrophysical logging of selected boreholes to quantify flow. At this site, bedrock wells were often dry. The results of the integrated, multi-phase investigation provided an increased effectiveness in drilling the deep bedrock borings in areas with an improved opportunity for encountering groundwater and groundwater flow.