2008-09-17_REVISION - M1980244 (28)

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level for the wettest years? Does CC&V plan to install additional piezometers to monitor • water level elevation in the riparian areas? Please explain. Response: CC&V believes two different matters are being raised by DRMS and provides the following responses. First, DBMS is correct that CC&V has in place a pumpback system in Arequa Gulch and augments that pumped water as well as water captured by the VLF under a duly authorized augmentation plan. CC&V will update that augmentation plan as Phase 5 of the VLF is brought on line and precipitation from the area is captured. This is an operational augmentation, in that once the VLF is closed, the liner would be punctured and the alluvial recharge in Arequa Gulch would be re-established. Second, as discussed above, CC&V has conducted an extensive investigation of Grassy Valley and has determined that the proposed mining activities would not impact the hydrologic regime. Moreover, the correlation of the water level in the shallow piezometers in the Grassy Valley riparian area with the water levels in the Grassy Valley monitoring wells is illustrated in Figure 8 included as Attachment 8. The water level in PZ-3 is contrasted with the water levels in two bedrock wells: GVMW-5A (about 150 feet below ground surface) and GVMW- 8A (about 350 feet below ground surface). The plot shows that the three wells operate synchronously: when water levels are high in the alluvium that water levels are also high in the bedrock. This is consistent with the behavioral concept stated above, that water is supplied to the bedrock through the alluvium. It is also • provided to the bedrock by infiltration over the rest of the Grassy Valley catchment. Numerous piezometers and shallow monitor wells have been installed in Grassy Valley. The water levels in the alluvium piezometers are measured by pressure transducers connected to dataloggers. The monitor well water levels are measured quarterly, but more recently also have pressure transducers and dataloggers installed. Figure 1 included as Attachment No. 9 shows the close temporal correlation between the P2 piezometer peaks (infiltration of surface water and saturation of alluvium) and selected shallow monitor well peaks (infiltration and saturation of shallow bedrock). The recent pressure transducer data for GVMW-1Band P2 for 2007 and 2008 also show the close correlation. The data between the alluvium piezometers and the monitor wells correlate well for all seasons, wet or dry. CC&V does not plan to install additional piezometers to monitor water level elevation in the riparian areas. The four piezometers that are currently installed in the riparian areas are correctly located to identify potential impacts from CC&V's proposed mining activities on the riparian areas. The piezometers are located on the upper reaches of the riparian areas, which is where the reduction in Grassy Creek stream flow is predicted to occur, if at all. They provide monitoring of the potentially most affected locations in the riparian areas, and are therefore conservative. G. How come the water quality data from the DRMS compliance well labeled GVM-8A, is slightly different from those ground water monitoring wells and other monitoring and • compliance wells located within the diatreme? Please explain Response. 4 1