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A Multi-Phased Approach for Deep Tunnel Detection at a Gold Mine Remediation Site

Multi-phase surface and crosshole geophysical investigations, including time-domain dipole-dipole resistivity and frequency domain Mise-a-la-Masse (MALM) surveys, were conducted on the Captain Jack Project, an EPA Superfund remediation site located near the town of Ward, Colorado. The Project area consists of an abandoned gold mine comprised of the Big Five Tunnel, the Dew Drop Tunnel, and the Niwot Crosscut.  Access into the mine workings is from the Big Five Portal, but extends approximately only 900 feet before a collapse prevents further exploration into the tunnels. Historic data suggests that the Big Five tunnel follows the NE-SW mineralized trend for more than 2000 feet, before intersecting the Niwot crosscut which connects the big Five to the Columbia vein to the North. The Dew Drop Tunnel is up-dip of the Big Five, following the same mineralized structure.The objectives of the first phase of the geophysical program (June 2011) was to characterize the geology of the host rock and the mineralized fault zone, as well as to determine the location of the tunnel system, if possible. Time-domain resistivity results indicated a high resistivity background with lower resistivity fluid conduits, but were unable to image deep enough to detect the mine tunnel. Initially, the MALM was used as a reconnaissance survey, with large distances between the lines covering the overall trend of the Big Five and Dew Drop tunnels. However, MALM data also showed potential to optimize the placement of drill holes meant to intersect the geologic structure associated with the mine, or intersect the tunnel itself.

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Client :

Energy Producers Ltd

Date :

April 21, 2017

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