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As can be seen from Table 4, and as plotted in section in Figure 7 included as Attachment 8, <br />• the entire section is essentially drained. The maximum head measured is 130 feet in GVMW- <br />13A, which is 600 feet deep. Nearby, at GVMW-13B, at a similar depth, the head in the well <br />is less: 26 feet. At a similar depth GVMW--11A is dry, because it is in the diatreme <br />(comprising tertiary phonolite and breccia). <br />Put in hydrological terms, the diatreme is drained, and in turn appears to have drained the <br />water out of the Precambrian rock in the Grassy Valley area. Mining the unsaturated rock can <br />draw no more water from the bedrock mass than is currently seeping through it. Accordingly, <br />mining can have no incremental effect on water transfer out of the riparian areas or the <br />alluvial aquifer in Grassy Valley. <br />Moreover, the riparian areas in Grassy Valley will not be affected when mining extends <br />beyond the elevation of the alluvial aquifer due to the following observations: <br />1. The diatreme currently acts as a very large "mine" from the point of view of water, <br />already drawing water from the Grassy Valley area and delivering it eventually <br />through the diatreme rockmass to the regional ground water table intersected by the <br />Carlton Tunnel. No mining proposed within the MLE Project Application area has <br />the potential to exert a greater demand for water on the system. <br />2. The alluvial aquifer is close to the input end of the ground water flow system, and <br />while changes in flow from the riparian area can affect downgradient (bedrock) areas <br />with respect to water levels, nothing that occurs in the bedrock can affect the water <br />• supply of the overlying and upgradient riparian areas. <br />If there is something that could be classified as the "worst case scenario" it is the scenario that <br />presently exists: the riparian areas would be drained by flow to the diatreme. All of the <br />piezometer data show that the alluvial aquifer routinely drains into the underlying <br />unsaturated bedrock and is partly replenished by infiltration of precipitation. Accordingly, <br />the "worst case scenario" is in fact the status quo, and no mining activity that does not <br />directly excavate or cover the riparian areas can change that status quo. The MLE Project <br />Application does not propose to excavate or cover the riparian areas. <br />The effect of mining within the catchment of Grassy Valley may be to reduce slightly the flow <br />of surface water down portions of Grassy Creek. This flow is already sporadic and small, both <br />with respect to the total water flux into the valley alluvium, and with respect to maintenance <br />of the riparian vegetation in the valley. Reductions in this flow can have no impact on the <br />riparian vegetation. To ensure that this assessment is correct, CC&V proposes to monitor flow <br />and ground water levels in Grassy Valley during and after mining. <br />F. DRMS has observed in the past 16 years some shallow alluvial flows that no longer flow <br />once the valley leach facility expanded. DRMS expects for example, when VLF 5 is <br />completed, drainage from AG-1 to dry up due to the placement of the valley leach in its <br />head waters. At present the drainage from AG-1 and the South under drain is pumped <br />back as make up water for the existing valley leach facility, but drainage from Grassy <br />• Valley is utilized by down stream landowners,. As such, CC&V has to assume worst case <br />scenarios to satisfy long term impacts to the hydrologic balance. How does the shallow <br />piezometer water levels in the riparian area, correlate with the GW monitoring welts water <br />