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I ' <br />i <br />open joints occurring within what is essentially asoil-like mass; and 3) hard, coarse grained granitic <br />pegmatite veins up to 2 to 3 ft thick crosscutting the other two rock types. <br />' Joint measurements were made within and to the north of the failure area at accessible locations along <br />the upper two existing benches and highwalls. Approximately 50 joint set data points were collected <br />' , to make a preliminary assessment of rock conditions and to input to ¢reliminary design for the interim <br />slope reconfiguration. Our plan is to augment this preliminary geologic data with additional joint set <br />and rock characterization data once the interim slope reconfiguration has been established. Then it <br />' should be possible to collect considerable additional data within the active failure area in a safe <br />manner from freshly exposed outcrop. Observations can also be made at that time of any possible <br />daylighting shallow failure surfaces. <br />The joint set data collected to date are summarized graphically in Appendix A and reveal four major <br />joint orientations. These are approximately N90E, 625; S67E, 88NE to 88SW; S30E, 88NE to <br />' 83SW; and NOE, 38W. The latter north-south trending joint set that dips west into the quarry at an <br />angle roughly equal to or greater than the internal friction strength of the rock is the primary source <br />of individual bench and overall slope instability. It should he noted that the failure area is the only <br />' major pit wall in the quarry with an unfavorable orientation with respect to this joint set. <br />Observations made of the failure area in the central pit lead us to believe that a fault or shear zone <br />roughly coincides with the failure area. Rock quality to the north of the failure area is generally good <br />with typical rock blocks on the order of several feet and up to over ten feet. Within the failure area, <br />rock quality is generally not as good and typical rock block sizes are smaller; on the order of 0.5 to l <br />ft, and up to about two feet indicating a higher degree of shearing such as would be present within a <br />' fault zone. Exposure of this feature after interim slope reconfiguration should confirm the occurrence <br />and nature of the fault/shear zone which will then be mapped safely from the interim benches and <br />highwalls and any impacts to design reassessed. <br />3-02. GROUND WATER CONDITIONS <br />' No investigations have been performed by Haley & Aldrich to evaluate ground water conditions at the <br />quarry. Several wells produce usable quantities of ground water in the site vicinity and these wells <br />' are thought to be at least several hundreds of feet deep. It is clear from our site visits that ground <br />water occurs some depth below the present level of excavation in the central pit. No persistent <br />ground water seepage has been observed in the east wall of the central pit during site visits made <br />' between December 1992 and April 1993. <br />Perched ground water may occur within the ruck mass in and around the failure zone during periods <br />of heavy recharge. Indeed, snowmelt and freeze-thaw during periods of snowmelt have certainly <br />accelerated failure of the slope as the runoff infiltrated the existing tension cracks. Ground water, <br />however, is not a permanent subsurface condition and a continuous water table surface evidently does <br />i ' not exist within the slope at the elevations of concern. <br />4 <br />~ ~c T~ <br />