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• (Page 2) ESINE ID $` OR PROSPECTING ID # - M-77-493 INSPECTION DATE 2 8 96 INSPECTOR'S INITIALS ACS OBSERVATIONS This inspection was conducted to observe the construction of a ground water cut-off wall being installed below Robinson Lake. The ground water cut-off wall is considered an Environmental Protection Facility as defined in the Hard Rock/Metal Mining Rules and "'Regulations of the Mined Land Reclamation Board. The Division recent'1~` pproved a design modification for the ground water cut-off wall to allow for the substiE . on of a 2 foot wide concrete footing for the previously approved bedrock key-way in thole locations where the cutting of a key-way has not been possible due to the extreme hardness of the bedrock. A track-hoe had been utilized to excavate the cut-off wall trench. The trench has exposed a layer of surficial fine grained soil with organics, which overlies 10-plus feet of fractured quartz monzonite. The cut-off wall contractor reports that the quartz monzonite was relatively easy to excavate. The quartz monzonite appears to be a sill overlying a massive, very hard quartzite. The quartzite surface undulates along the length of the trench, with changes in elevation of the bedrock surface of 6 to 8 feet. The low spots in the trench were filled with water and ice, so that only a small percentage of the total quartzite surface could be inspected. In the areas of the quartzite surface that could be inspected, no significant fracturing was observed. As part of the certification report for this Environmental Protection Facility, the certifying engineer must state that the bedrock foundation for the cut-off wall was inspected by a qualified individual, and that no transmissive geologic structures are present. A key-way had been cut into the quartzite exposed in the base of the trench at its east end. rr- The key-way was well in excess of the 24 inch specified minimum depth, and was approximately 12 inches wide. The specified minimum width for the key-way is 8 inches. Efforts to cut the key-way at the west end of the trench had failed due to the hardness of the quartzite bedrock. Locations where cutting of the quartzite was attempted at the west end of the trench were inspected. The contractor tried using two different Vermeer trenchers. It could be seen that the cutting blades had little affect on the very hard rock. The operator intends to carry the 24 inch wide footing across the entire length of the trench, even in those locations where a key-way has been cut. The operator further intends to maintain the top of the footing at a single elevation along the length of the trench, regardless of the undulating bedrock topography. A level footing will facilitate the application "PVC Water Stop•• or other appropriate seal between the footing and the concrete cut-off wall. The possibility of backfilling low spots in the trench, on the upstream side of the cut-off wall, with low permeability soils up to the elevation of bedrock highs within the trench, was also discussed. This would serve to direct water collected behind the cut- off wall to the pump location. It was suggested that a geomembrane be installed on top of the low permeability backfill. The Eagle Park Reservoir tailing removal project was briefly observed. A large excavator is used to load haul trucks in the bottom of the impoundment. The tailing is then hauled to the Tenmile Pond. Because of the high moisture content of the tailing, there is spillage from the haul trucks along the haul route. It waa observed that the haul route is below the elevation of the lower interceptor ditches on the Eagle River aide of the divide. As such, any run-off from the haul route would report back to Eagle Park Reservoir. The spilled tailing is periodically picked-up and hauled to Tenmile Pond. I 6 E Contact Address NAME Bryce ROm14 OPERATOR Climax Molybdenum Comoanv STREET Climax Mine. Hiohwav 91 CITY/STATE/ZIP Climax. CO 80429 cc: Carl Mount, DMG ~ CE ~ BL ~ FS ~ HW ~ HMWMD (CH) ~ SE ~ WQCD (CH) ~ OTHER