There are two primary objectives for this project: 1) select a geophysical method or a combination of methods to locate possible karst or subsurface anomalies ahead of the mining with the sand and clay unit in place. Once the sand and clay unit has been remove follow up with a GPR survey over areas where suspected karst or geophysical anomalies were identified; and 2) develop a routine schedule for conducting geophysical surveys to detect possible stability problems on the upper bench and quarry floor prior to the mining operations reaching suspected areas.

We propose using a scaled approach to accomplish the objectives. Different geophysical methods have different resolution; with resistivity and seismic refraction having coarse resolution and GPR having the finest resolution. Based upon the results from previous studies (Applied Geosciences, Inc) and completion of ongoing field testing of different geophysical methods, the following methods have had positive results. The results from the Applied Geosciences, Inc. surface resistivity survey appear to have located possible karst or solution features in the subsurface. The current study will follow up on the results from Applied Geosciences using surface resistivity but with closer electrode spacing to attempt to enhance both the vertical and spatial resolution. Because the seismic refraction survey on the quarry floor was successful, the technique will be tested along the same resistivity survey lines to determine the effectiveness of locating karst features or geophysical anomalies with the sand and clay unit in place. If karst features or geophysical anomalies are identified either by resistivity or seismic refraction or both, once the clay and sand unit has been remove a follow up survey using high resolution GPR will be conducted over suspect areas to confirm the presence or absence of these anomalous features.