GTS Technologies was contracted to provide an extensive evaluation of the subsurface geology and material quality for a major quarry expansion using geophysical methods to survey an area encompassing 330 acres. Major sections of the proposed area had unknown thickness and amounts of stiff clay that presented major excavation challenges and waste. A mine plan would be required to avoid these areas and to optimize the excavation, processing and wastage costs. Much of the acreage was not accessible to drill rigs for direct evaluation. Approximately 110 acres of the property was optioned for purchase, and the client needed to know whether to proceed with its acquisition.

GTS proposed surveying the entire site using terrain conductivity geophysics, which would enable GTS to quickly discover which parts of the site contained significant amounts of clay compared to the desired sand and gravel resource. The nondestructive, non-invasive nature of the geophysics satisfied property owners that their crops would not be destroyed by the investigation. After the terrain conductivity geophysics, several thousand feet of electrical resistivity imaging was also completed principally within the 110-acre acquisition area to provide detailed geologic stratigraphic information that could not be obtained from boreholes.



GTS established a series of profiles on 100-foot centers and collected terrain conductivity data using a Geonics EM-34RT meter coupled with a sub-meter accuracy Trimble GPS and datalogger set to collect a data point approximately every 12 feet along each profile. Over 14,400 measurement points were collected. The data were collected over three days and processed daily to show the results immediately to the client.

Four 2,100-foot electrical resistivity profiles and one 900-foot profile were completed over a 3-day period to a depth of 160 feet showing the depth and thickness of the geologic materials. These data were correlated with limited borehole information to construct geologic cross-sections and a fence diagram indicated the extent and quantity of sand and gravel resource and waste materials.

The results indicated that an extensive area (~100 acres) of the property was underlain by thick sequences of clay and relatively thin sequences of sand and gravel at depth. Most of this area was within the 110-acre new purchase. The geophysical data indicated that the proposed property acquisition should be tabled. The data also confirmed that there were rich deposits of sand and gravel in other areas of the site. This information was incorporated into a mine development plan to optimize the extraction of the resource for maximum efficiency and profit.


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METHODS
Electrical Resistivity
Terrain Conductivity
Very Low Frequency
Spontaneous Potential
Seismic Refraction
Ground Penetrating Radar
Magnetometry
Vibration Monitoring
Soil Resistance Testing


CASE HISTORIES
Archaeology
Bedrock Delineation
Ground Penetrating Radar
Groundwater Availablity
Mining 1
Mining 2
Sinkhole Investigations
Sinkhole Investigations 2
Soil Resistance Testing
Underground Storage Tanks
Vibration Monitoring




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