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GANSER LUJAN & ASSOCIATES <br />Hydrogeological and Environmental Consultants <br />Model results for the pre -mining topographic surface (Table 1) for the 5 -year event show <br />a value (4872.43) well below flood elevations. Thus, the modeling results indicate that <br />the Bachofer property should not be flooding with pre -mining topography at 5 and 10 <br />year flows. The model results are very similar (within 0.05 feet) at 4873.95 feet to the <br />established FIS 100 year flood elevation, which indicate that the model is well -calibrated <br />and that it is simulating real-world hydrologic conditions. <br />Discharge from the 10- year event (10,000 cfs) was also modelled to closely simulate <br />peak flows that occurred during flood events in September 2013 (10,300 cfs) and in May <br />2015 (10,500 cfs). Flooding occurred at the Bachofer house during both of these events <br />(Bachofer, 2015 Oral Comm.). As can be seen on Table 1, the model results validate <br />these events. At 10,000 cfs, the modelled water level elevation is 4874. 26, which is <br />measurably above the FIS 100 year flood plain elevation. Based on the 2008 <br />configuration of the land surface, surface water levels at this flow now cause flooding. <br />Simulations using pre -mining topography show that the water surface for 10,000 cfs is <br />4872.66, which is well below the established flood plain level at the Bachofer property. <br />Figure 6 below shows output from the HEC -RAS model for existing mining conditions. <br />These cross-sections illustrate that the surface of the flood plain is highly irregular. The <br />high areas shown below may be interpreted as berms constructed around the reservoir <br />pits to prevent flooding. Cross-section 3193.73 represents the land surface that transects <br />the Bachofer property. As can be seen on this cross-section, there are five high areas that <br />are obstructing the flood plain and precluding dissipation of the flood waters across the <br />flood plain. <br />Figure 6 <br />HEC -RAS Results <br />Existing Mining Conditions <br />2008Mining Bachofer8-12-2015 <br />RS- 470078 <br />3 <br />1 1 <br />UVW <br />EGPF3 <br />W8 PF3 <br />y <br />EGPF2 <br />WS PF2 <br />V45 PF 1 <br />Bak BY <br />2008Mining Bachofer 8-12-2015 <br />RS- 423311 <br />04- <br />4895 <br />/ <br />to <br />4BM EGPF3 <br />405 M PF 3 <br />EGPF2 <br />i48W WS PF 2 <br />w 4875EGPF3 <br />_. WS PF 1 . <br />48 <br />Bak Sm <br />0 t00D 2)OD 3000 4000 56W 0000 7000 <br />SWW(ft) <br />-8- <br />