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Investigative Methods for Controlling Groundwater Flow to Underground Mine Workings

Case Studies


An image of a stream near the Charter Oak Mine.
Figure 17—A small stream originates well above the uppermost workings of the Charter Oak Mine and flows in a nearly straight path through the disturbed area. Seeps like the one in the right center are common near the workings. The uppermost adit, the Kineo, is just to the right of this photograph.

Aerial Photography

The aerial photos in the area were of limited use. The volcanic rocks that host the ore body do not have a strong joint pattern. The Dog Creek Fault (Schmidt and others 1994) follows the Little Blackfoot River (figure 18). The trace follows the valley up Hat Creek to the southwest. It is the only regional structure that has been mapped in the immediate area. The unnamed tributary to the Little Blackfoot River follows an east-west lineation. Its course also may be locally fault controlled. Vegetative changes reflecting the presence of groundwater are not evident.

Characterization and Mapping of Riparian Areas and Wetlands

A brief study of the topography and possible discharge and recharge areas indicated that the area adjacent to the Charter Oak Mine is much smaller and less complex than the area adjacent to the Elkhorn Mine. The riparian and wetland areas associated with the Charter Oak Mine are primarily downgradient from the mine along the Little Blackfoot River. One unnamed tributary to the Little Blackfoot River flows through the area. It may be a direct source of recharge to the mine. Negro Mountain, almost a mile away, forms the drainage divide to the southeast. No other tributaries or possible source areas were detected from the topographic maps or aerial photos. A preliminary field investigation revealed no springs or wet areas on the slope above the mine. The only catchment basins were from recontouring to inhibit erosion on the steep face where the workings were driven and on exploration roads high on the hill. These areas held snow in the late spring, but were not large enough to be significant. The apparent simplicity of the drainage, and the lack of distinguishable wet areas on the aerial photos, led to the decision to concentrate time and funding on the more complex Elkhorn Mine area.

A skyview of the Charter Oak Mine pointing out faults and Lineament.
Figure 18—The Charter Oak Mine is near a small tributary of the Little Blackfoot River. The stream flowing through the site may be controlled by the lineament (fracture). The mine apparently explored the Kineo vein as the main source of ore.
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