www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 23 The permeability of the EGV and surrounding rocks and calculated water levels indicate a well-connected aquifer system, and that the aquifer is fully connected along strike in the area investigated. • Drawdown during mining will probably propagate longitudinally along strike. • There is potential to impact any streams or shallow groundwater north or south of the currently defined strike limits of the EGV if it continues in these directions. The western hanging wall EGV system is conceptualised to form a flow barrier. • Propagation of mining induced drawdown in the EGV aquifer westwards will likely be limited essentially protecting shallow groundwater and streams in these areas from mining impacts. As this corresponds with the location of the headwater springs this conclusion is significant. • Further definition of the full longitudinal extent of the western EGV system to the north and south is required to assess the extent of these connections. Shallow groundwater conditions directly overlying the EGV system are currently unknown. This is considered a key data gap in the site conceptualisation. 5.3.7. T-STREAM GROUNDWATER SYSTEM Two test holes were advanced to intercept the T-Stream vein, WKP-104 and WKP-03D, with WKP-104 specifically designed to intercept the T-Stream vein beneath the area where it outcrops in the stream itself (Figure 5-4). A total of four hydraulic tests were completed in this borehole. Figure 5-4: Schematic cross section of WKP-104 (left) and WKP-03D (right) (after FloSolutions) The following observations are made: • Hydraulic conductivity values are much lower than the EGV ranging from 9.8E-8 to 4.1 E-6 m/s from packer tests in WKP-104 and very low values of 3.0E-08 and 6.8E-09 m/s from two infiltration tests in WKP-03D. • Hydraulic conductivity values in the hanging wall rhyolite flow dome are quite low. • Two of the three zones tested in the hanging wall were dry, with the shallowest test indicating confined conditions. • The test in the footwall has slightly higher K and a deeper water table. • Water levels for the two deeper VWPs are at or approaching the VWP elevation, with negative pressures indicating dry or limited water conditions in the hanging wall and vein system. The deeper water table detected in one footwall test interval is clearly disconnected from any overlying groundwater system, as evidenced by dry VWPs in the vein itself and in the hanging wall overhead.
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