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instability and from our understanding there was no continuous movement-monitoring program <br />in place during mine operations. At these potentially unstable conditions, continued deepening <br />of the open-pit mine in Area H at the base of the west quarry wall ultimately resulted in slope <br />failure. <br />There was much emphasis placed on a "clay seam" in the mine permit and a perceived <br />improvement in slope stability once mining activities were below that elevation (the permit <br />amendment stated, "the hazard of massive landslides into the Hole caused by major slippage <br />on clay zones within the formation will be significantly reduced.'). CGS feels that the quarry <br />failure likely had little to do with an individual clay seam as the actual failure mechanism and <br />finds the 1986 MSHA report more accurately stating the primary stability issues of this mine. <br />The quarry wall failure was a combination of 1) adverse steeply inclined strata that <br />daylighted into the quarry excavation, 2) the inherent weakness of the rockmass caused by the <br />abundant discontinuities related to the Rampart Range fault zone, 3) loading the top of the <br />quarry benches with spoils from the more recent expansion and excavation into granite at the <br />top of quarry, 4) further undermining and steepening of the rock slope related to mining and <br />removal of rock in Area H (the Hole), and to a lesser extent, 5) potential rock damage at the toe <br />of the slope caused by production blasting, and 6) effects of water from the off-site drainage <br />swales. <br />The current state of the west quarry wall is, in CGS's opinion, unsafe and monitoring of <br />the rockslide should be part of an immediate action plan. A monitoring plan was mentioned in <br />the mine permit but it was not clear whether any program was being followed, or if it was a <br />manual or automatic system that could be incorporated into a warning system. No monitoring <br />data for the quarry has been reviewed by CGS. <br />Prior to removal of equipment or any work of any kind within or below the slide mass in <br />Area H or beneath the upper tension cracks and incipient scarp, ground movement instruments <br />should be installed and closely monitored for movement. This monitoring plan should be a <br />continuous monitoring system and tied to a data logging system with alarm capability. We offer <br />the following monitoring system suggestions that would fulfill this role. <br />10