2020-12-21_PERMIT FILE - C1981010A (2)

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Cottonwood Spring is likely groundwater that is derived from strata shallower than the bedrock that is directly in contact with the backfill aquifer in this area. The Fox Den Spring is located on the eastern flank of Oak Gulch approximately 800 feet north of the nearest upgradient mining activity in the initial cuts of the A East pit. Mining in this area did not initially show an impact to flows at this site, however, flows have appeared to reduce each year over the past few years. This spring exists near the southern limits of the Third White Sandstone outcrop and has been thought to emanate from the Third White Sandstone. A travertine deposit has been noted to exist on the surface at the site of the Fox Den Spring. This deposit may indicate that water quality from this spring was significantly different in the past for some period, or that the source of this spring is from a deeper aquifer containing more highly mineralized water. Sulfate and TDS concentrations measured at the Fox Den spring are similar to levels documented in Third White Sandstone wells GC -2 and GP -9. It is unknown if the following explanation of a deeper source has any merit. A deeper source for the Fox Den spring would require that a permeable zone exists to transmit the water to the land surface. Though no obvious geologic structural features have been identified in the immediate vicinity of the Fox Den Spring, some subtle indications are present. A similar travertine deposit was noted to exist at springs to the east in Flume Gulch (Spring 99-2 and Spring 99-3). The alignment of these springs and the Fox Den Spring roughly paralleled a northwestisoutheast trending regional fault system, the Cedar Mountain fault system, north of the project area. This is the dominant geologic feature in the area. The Big Bottom Syncline may have smaller displacements or slips associated with it that could conceivably transmit water. This type of feature could account for flows at the Fox Den Spring. The lithologic units at Trapper have numerous layers of very fine-grained material that would be expected to have sealed any significant vertical fracture zones or displacements. However, a small displacement on the order of tens of feet may have occurred without the extensive sealing or smearing of the fracture zone associated with a larger fault. The springs in Flume Gulch (Spring 99-2 and 99-3) were near the southern limits of saturation in the Third White Sandstone aquifer and were also thought to be discharges from this groundwater system. However, TDS and sulfate concentrations measured at these features occurred at lower levels than those documented at Third White Sandstone wells GC -2 and GP -9. Spring 99-2 flowed from a vertical pipe at an old homestead location. Details regarding the installation of the pipe are unknown, however, field measurements showed the pipe extended down roughly 180 feet from the surface. The H seam is known to lie about 30 feet deep at this location. The structural model for the site indicated the pipe at Spring 99- 2 extended nearly to the M seam. Based upon this information it is possible the flow from Spring 99-2 4-238b MAY 21 2013 J a� - j�) "-) "t')°d