2015-11-16_REVISION - M1985043 - Laserfiche WebLink

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also noted on maps where rock types differ as one crosses the line of movement or failure. In the case of the fault structures mapped within the permit area, these structures reflect different rock types in unconformable relation to one another as one unit(the sediments in this case) have come into contact with the granite gneiss rock due to earth forces pushing upward from deep within the crust of the earth. This contact can be viewed within the pit at a location recently exposed by mining. Recent field study in response to this technical review has noted that mining has exposed an good example of the contact point along the eastern side of the pit. The line of contact has been mapped and is shown as a red dotted line running parallel to the type cross section line. While the sedimentary rock is several feet thick at the lower end of the contact, the sediments quickly thin to only 1 foot wide at the top of the pit, surrounded and encased in granitic bedrock. It appears that the sedimentary sequence is an outlier which has been absorbed, or re -melted into the neighboring igneous/metamorphic bedrock leaving chunks of sedimentary rock now found floating within the granite gneiss basement rock complex. Granitic gneiss truncated by felsic dyke material can be viewed east of the contact zone along the dozer trail paralleling the east margin of current mining, well within the permit zone.(labeled Meta Rx on the map). The mine operator is confident that future mining will remove all of the sedimentary rock as landscape and erosion control product and entertain granite gneiss bedrock lying below and east of the current contact zone. While the contact at the southern end of the contact line shown on the map reflects movement and breakage of the sedimentary sequence at the point of contact, as one follows the contact north and east, it becomes apparent that the sedimentary rock is a sliver of material which looks to have been re -absorbed into the granitic rock mass. This is reflected in metamorphic mineralogy evident in the otherwise clastic sandstone/siltstone rock one can view outcropping along the contact line. If there is a fault zone associated with this contact of varying lithologies, it likely located east of the pit area in the area of the dozer trail paralleling the east side of the currently disturbed area. In addition, the fault line delineated by the contact mapped within the pit is perpendicular to the orientation of the highwall build out. For the above reasons, a failure plane event like Pikeview is unlikely. 6. No phreatic surface impact was included in overall slope stability analysis after a review of all water wells drilled in the area and a negative response to any known seasonal(or not) spring flow events from any location within the mine site. Meteoric water flow will have some influence on localized mine bench weathering and maintenance as well as demanding good surface drainage from storm events and snowmelt. The mine operator will have positive (+1%) drainage from all final benches to rock lined channels as is currently done at the bottom reaches of the mine site to collect and convey storm flows safely from the highwall zone to the lower portions of the site. Freeze and thaw affects will be monitored closely by field personnel and the conservative 40' wide bench geometry will allow for room to deal with any localized areas of concern due to storm derived rock deterioration at the surface. Again, at worst case scenario, rock lined channels and talus slopes of no greater than 1:1 can be employed to handle areas of extreme weathering or impact due to meteoric water flows.