2010-02-02_REPORT - M1973021 (2)

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Further, no features were observed that are anticipated to cause large block size failures. Markland orientation data indicates very low probability of wedge or toppling failures. Markland orientation data also indicates a low probability of plane failure; the plane failures are most probable on the foliation surface when it dips out of the highwall face at greater than approximately 38 degrees. The foliation orientation at several locations has the potential for plane failure. However, from observations in the field, any blocks loosened in this area will be limited in size and are anticipated to be caught on the bench below the highwall. These results are similar to previous geotechnical addendum data. Therefore, other projected failures are estimated to be limited to raveling of smaller blocks in localized areas. These localized failures are not anticipated to extend further than the bench width. 5.0 CONCLUSIONS 5.1 North Quarry The observed condition of the slopes within the North Quarry appears to be stable. Observations of the North Quarry include: • No large scale failures in the past year. • Minor accumulations of slough material and small rocks. • Nearly all material was contained on adjacent bench surfaces with very little evidence of material accumulation at the bottom of the North Quarry (observed before the transfer of water from the Central Quarry). 5.2 Central Quarry The observed condition of the slopes within the Central Quarry appears to be stable. Observations of the Central Quarry include: • No large scale failures in the past year. • Minor accumulations of small rocks (up to 1 1/2 feet diameter) on bench surfaces. • Nearly all material was contained on the adjacent bench surfaces with very little evidence of the material proceeding down slope to subsequent benches or into the water storage reservoir. • The stabilized slope in the northeast section of the Quarry did not exhibit any instability or large erosional features. • The highwall face adjacent to the haul road did not exhibit any instability or large erosional features. -8- Morrison Quarry Annual Report 2009 February 2010 P:\23514\133-23514-10003\Deliverables\Deliv-0l-Annual Report\Annual_Report_2009_Geotech, 1-25-10.doc