2015-01-16_PERMIT FILE - M2015001 (2)

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Tegre Corporation Job No. 3124JS057 The north and east property boundaries extend along the edges of the mesa. The excavation operations will lower the ground surface elevation and mesa height. Therefore mining operations will not impact off-site areas to the south and east of the gravel pit. The mining operations will result in excavation slopes along the north and west property boundaries. In these areas maximum allowable slope inclinations should be established so that potential slope failures do not extend beyond the limits of the proposed gravel pit. For the short-term condition, the excavation side slopes and embankments should have a minimum factor of safety against deep-seated slope failures of 1.5 in order to reduce the potential for slope failures occurring outside of the gravel pit limits. The short-term condition is for the case during mining operations where the side slopes will remain unsupported for less than about 4 months and the excess pore water pressures do not have time to dissipate. The maximum slope inclination for short-term excavations is presented in Table 4 for various excavation depths. For the long-term condition, the excavation side slopes and embankments should have a minimum factor of safety against deep-seated slope failures of 2.0 in order to reduce the potential for slope failures occurring outside of the gravel pit limits. The long-term condition represents the case that will occur following mining operations where the site is reclaimed. The maximum slope inclination for long-term excavations is presented in Table 5 for various excavation depths. 7.0 LIMITATIONS This report has been prepared assuming the project criteria described in Section 2.0. If changes in the project criteria occur, or if different subsurface conditions are encountered or become known, the conclusions and recommendations presented herein shall become invalid. In any such event, WT should be contacted in order to assess the effect that such variations may have on our conclusions and recommendations. The recommendations presented are based entirely upon data derived from a limited number of samples obtained from widely spaced borings. The attached logs are indicators of subsurface conditions only at the specific locations and times noted. This report assumes the uniformity of the geology and soil structure between borings, however variations can and often do exist. Whenever any deviation, difference or change is encountered or becomes known, WT should be contacted. 10