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' interbeds parallel to primary jointing having a slick and weak character <br /> as were frequent higher in the rock mass are less common at the present <br /> ' depth of excavation. <br /> ■ The predominant dip angle of the primary joint set is usually at or <br /> slightly steeper than the approximately 35 degree inclination of the <br /> overall slope and, as a result, the joints typically parallel or plunge into <br /> the slope where the strike is sub-parallel to the slope. The joints <br /> frequently daylight, however, on the vertical and near vertical individual <br /> highwalls. Some foliation dip angles are as shallow as 15 degrees, <br /> locally, but at the depth of new final highwalls created in 1997, the <br /> strike is generally sub-perpendicular and has a more favorable <br /> orientation for stability. <br /> ■ At least two secondary joint sets are present, often orthogonal with the <br /> primary joint set and to each other. These secondary joints typically <br /> occur at intervals of one to five ft and are typically near vertical to <br /> moderately steeply dipping. They occasional!y daylight causing <br /> ' localized block and wedge failures within acceptable limits. In general, <br /> secondary joint surfaces are planar, are fresher and less weathered than <br /> the primary joints along foliation, and do not exhibit the smooth <br /> schistose or micaceous surfaces. The secondary joints are also locally <br /> ' discontinuous, terminating at primary joints. <br /> ■ Localized block and wedge failures of the outside edges of the third and <br /> ' fourth benches were previously reported as common but less prevalent <br /> than in the upper two benches. This difference in behavior was <br /> attributed to the sloped highwalls from the angle drilling, and from the <br /> ' lesser degree of weathering of the rock material at greater depth within <br /> the rock mass. This trend in improved rock quality and outboard bench <br /> edge stability with greater depth into the rock mass was observed to <br /> ' continue in 1997 with the development of the 5th and 6th benches from <br /> the top of the East Highwall. <br /> ' Based on the conditions observed with the present exposures, the rock mass <br /> exposed in new highwalls developed during 1997 is consistent with the <br /> conditions used as the baseline for analyses of the East Highwall. <br /> B. Survev <br /> ' Twenty pre-repair surface survey points (numbered 1001 through 1020) were <br /> installed (as shown on the figure in Appendix D of the 1996 Annual Report) to <br /> monitor slope movements and help analyze the failure mechanism/geometry. <br /> These original survey points were destroyed during the repair activities in late <br /> March/early April 1996. <br /> ' After the repair, 26 new surface survey points (numbered 2001 through 2026) <br /> were established to monitor the effectiveness of the repair. Through December <br /> 9 GAP ROJ E•CTS\'_0200\002\97ANNR PT.W PF <br />