2009-05-12_REVISION - C1981025 (8)

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2. Ground Water Monitoring Ground water monitoring was accomplished at the two piezometers D-IA and D-2A, and includes the parameters of water level, temperature, pH, and conductivity. Piezometer D- 1 A is located in North Thompson Creek alluvium in proximity of the foot of the mine waste pile. Piezometer D-2A is located in the same alluvium, but upstream (North Thompson Creek) a short distance from the mine waste pile area. This groundwater monitoring was terminated with the approval of Technical Revision 23 on February 23, 2004. There is no groundwater monitoring in the Middle Thompson Creek drainage or at the loadout site (Roaring Fork River). Ground water points of compliance (wells) are required for an operation that has the potential to negatively impact the quality of ground water. The bedrock ground water at the North Thompson Creek Mine is in formations whose permeability is too low for mine leachate to significantly infiltrate into the rock; therefore, there is no potential for negative impact, and consequently a compliance point is not required for the bedrock formations. The absence of potential for negatively impacting bedrock ground water indicates the mine is in compliance with the Basic Standards for Ground Water in bedrock formations. Leachate seeping from the mine's refuse pile has the potential for negatively impacting the alluvium downgradient (southeast) from the refuse pile. The mine monitors North Thompson Creek alluvial ground water in well D-IA. This well is within the expected flowpath of leachate, should leachate flow from the refuse pile to the alluvium. Well D- lA meets the qualifications of a compliance point. A leachate plume in the alluvium can be expected to extend no more than 1,000 ft. downgradient from the refuse pile, owing to the laterally discontinuous nature of the alluvium and dilution of alluvial water by flowing stream water. If this 1,000-ft. distance is considered to be the "specified area", as this term is defined in the Basic Standards for Ground Water, then the alluvial water can be tentatively classified as water of Limited Use and Quality because within this specified area, the North Thompson Creek alluvial water is of such small volume that it is not currently used and is unlikely to be used in the future. The Basic Standards have no water quality standards for the Limited Use and Quality classification; therefore, the mine is in compliance with the Basic Standards for Ground Water in alluvial formations, at the location of well D- IA. As stated above, all groundwater monitoring was terminated with the approval of Technical Revision 23 on February 23, 2004. E) Stream Buffer Zones Pre-law surface or underground mining activities within 100 feet or through perennial streams or streams with a biological community within the permit areas were recognized in the PAP. The approved reclamation plans included restoration of original stream channels, a requirement that water quality and quantity shall not be adversely affected, and a requirement that appropriate riparian vegetation was to be reestablished. Recognized pre-law areas of North Thompson Creek C-1981-025 Permit Renewal 05 12 May 2009 16