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Bruce Park Landslide Project No. 25-196 <br />Bowie Mine #2 <br />0 seismic event, the water wave produced due to the landslide entering the lake would have to be <br />in excess of 10 feet high to reach the dam crest. Using average slide dimensions and <br />estimations of water depth offshore, maximum water wave amplitudes were estimated using the <br />procedures presented by Slingerland (1982). Based on our analysis, to generate a 5-foot high <br />water wave across Terror Creek Reservoir, the existing landslide would have to accelerate to a <br />velocity of 2 feet per second before entering the reservoir. We estimate the slide is currently <br />moving at 0.00000004 feet per second. With an anticipated peak seismic ground acceleration <br />of 0.034g, we do not believe the seismic energy is sufficient enough to accelerate the landslide <br />to a velocity greater than 2 feet per second causing a water wave across the reservoir large <br />enough to compromise the dam. <br />CONCLUSIONS AND RECOMMENDATIONS <br />Based on our investigation and analyses, we conclude the following: <br />• The fine-grained nature of the landslide materials poses a low risk for liquefaction. It <br />is appears there is a low potential for the landslide to move as a high velocity debris flow. <br />• If the estimated volume of the landslide was to completely displace into the reservoir, we <br />expect it would raise the reservoir level only about 1 to 2 feet. We estimate the reservoir <br />was designed with at least 10 feet of free board on the dam. <br />• The anticipated seismic events are relatively small (<4.OML) and would likely not <br />accelerate the landslide to a rate that would cause a water wave large enough to <br />compromise the dam. Our analysis indicated the landslide would have to accelerate <br />several thousand times the current rate to produce a wave at least a 5 feet high. <br />In summary, we do not believe the global stability of the existing landslide would be <br />significantly reduced due to the mining activity planned near Terror Creek Reservoir. The slight <br />reduction in global stability would likely not cause a catastrophic slope failure large or fast <br />enough to compromise the integrity of the Bruce Park Dam. <br />LIMITATIONS <br />This study was conducted in accordance with generally accepted geotechnical <br />engineering practices in this area for use by the client. The conclusions and recommendations <br />submitted in this report were based upon the data obtained from exploratory borings, a <br />preliminary field reconnaissance and previous investigations performed by others. We should <br />8