2011-10-31_REVISION - M1976009HR (7)

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October 2011 Page 6 This also explained the apparent layers of finer sediment upstream from this location. The slide had dammed the stream and created a small lake. Once the lake filled with sediment the stream cut through the slide and eroded down through the sediment upstream leaving a gully -like course through the sediment. Because of the configuration of the stream at this location, it is likely that the stream would have eventually exhumed the old meander and continued cutting into the cliff at the back of the bench that was created by the back hoe. Stream configurations and surface indications downstream show that the stream has had very little meandering in that area. Therefore, as the stream, over the coming centuries, regains its pre -slide path it will be discharging into an area that is, so to speak, pre- adapted for that stream configuration. In other words, the current configuration is the "abnormal" geomorphic alignment caused by a landslide and the previous configuration with a westward meander is the more "normal" configuration established without a landslide. As a result, the establishment of the elevated bench and the removal of much of the landslide fill in the meander will aid the stream to regain its original course, but over a time period that will likely be much longer than the life of the mine. Examination of sediment and tree growth in the sediment upstream from the landslide location shows trees that are probably at least 150 years old. These are mainly white fir, douglas fir, with some ponderosa and lodgepole pine. There is little evidence of an earlier generation or that area having been burned in the last 50 to 100 years. These trees appear to have become established in the original sediment that filled the pond. Tree roots are exposed along the current channel indicating the channel was significantly deepened after the trees had reached mature size. Although that could have occurred from recent flooding, that does not appear to be the case as there is little evidence of major peak flows having affected this area as significantly as it affected other areas. Based on this evidence it appears the landslide probably occurred about 100 to 150 years ago at the minimum and possibly 300 to 500 years ago assuming there have been multiple slide and ponding events. Looking at just the evidence at hand and without doing a great deal more exploration a nominal age of the landslide would be around 150 to 250 years. The presence of the bench will serve two important purposes. First, as the old surface is newly exposed at the back of the bench, additional rock falls may occur and those can be caught on the bench without going into the stream. If the stream creeps westward it can deal with those rocks then rather than now. As the slope above this area where the landslide came from is now gone, landslide hazard has been eliminated. As the material above the rock wall at the back of the bench is graded and covered with overburden and soil, some sediment discharge from that can be expected. Rather than discharging directly into the stream and increasing sediment loads, the sediment will be deposited on the bench adding fines and improving the growth medium making it more suitable for establishing shrubs and trees to further control water quality in the stream. In time, that may be destroyed by the stream, but that will be a slow process rather than a fast process that produces lots of sediment. In conclusion, as it turned out the geology of this small area was found to be completely different than expected. It also reveals a more complex past and involves features commonly found in steep sided canyons such as this. More important though, working with that more complex geology created Menzer Quarry Corrective Action Amendment Exhibit D Mining Plan