2017-12-01_REPORT - M2007014 - Laserfiche WebLink

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within the confines of the face and the gully west of the face, which happens to also be in the area of the west permit boundary. In this part of the active pit, rock failure is most likely to be a function of loosening of rock along the bedding plane at the interface of un- blasted rock and blasted rock. Other than the zone noted along the edge of the mine bench mentioned above, no slippage or failure was evident interior to mine bench as viewed at the face or along lateral aspects of un-mined material within the active pit. It appears that the top bench and possibly the lower mine bench can be extracted with little concern of bedding plane displacement due to lack of continuity of bedrock west and above these beds. It should be noted that the N/S gullying is likely a result of tensional weakness of the dipping beds that has been enhanced by erosion over time to result in a shallow gully running more or less parallel to the working face. At least in the southern and central part of the pit, there appears to be little risk for movement other than at the immediate mining face due to blasting. At the northern end of the active mining area, the bedrock sequence is not broken at the west permit boundary by an erosional feature, although a dozer cut following the direction of dip allowed an easy path across the upper mine bench that terminates west of the west permit boundary and reflecting 15'or more thickness of bedrock above the shallow erosion feature running N/S west of the west permit boundary. In addition, a rough estimate of the thickness of bedrock up-dip and above the mining area appears to show that at least another 30'or more of bedrock is continuous with the lower bench in the active mining area below. The limit of mining at the northern end of the pit is an east/west trending gully that is well formed, more than 50'deep and 100'wide exposing not only the bedding planes of the same rock mined but sedimentary beds lying below (and above)the strata mined within the active area. This area was traversed along the un- disturbed dip slope, looking carefully for any sign of bedding plane failure, slippage, or evidence of broken rock or soils mixed with bedrock that may occur along the dip slope if movement has occurred. No evidence of bedding plane located rock movement was noted at any view point around the working face, exposed northern dip slope, or western permit boundary at the top (west side) of the permit boundary. Summary and Conclusions An inspection of the active mine site as well as surrounding un-disturbed areas resulted in no field evidence noted of bedrock instability due to geologic disposition or mass loading from up-dip rock mass. The northern end of the working pit area holds more potential for gravitational force on the mining face below than the central and southern parts of the active face. This condition could be mitigated to a degree by mining all of the overlying strata back to the upper N/S gully running parallel to the mining face. It is advised that mining face edge cleaning be continued to minimize potential rock fall from the top edge of the face as well as keeping blasting directions as much as possible at 90 degrees from strike direction. At the northern end of the active mining area, leaving deeper mine benches especially in the siltstone/clay sequence, may help to add to a factor of safety to the exposed dipping beds as they outcrop at the active mining face. Should you have any questions regarding this inspection and report, do not hesitate to contact me.