Laserfiche WebLink
• Construction at the Tce Area <br />Rock was sorted and stockpiled at the rock crusher in the Colowyo East Pit and <br />along the toe of the middle dump of the Colowyo East Pit for construction of the <br />underdrain in the area of the toe. There were closer sources of rock, however, the rock <br />at those sources was not as suitable as the rock sources described above. The following <br />characteristics were sought for rock to construct the underdrain. <br />^ Well cemented, durable rock. <br />^ Angular rock that would interlock and bridge once placed. <br />^ A size distribution that contained rock that was generally between one foot <br />and six feet in diameter. By mixing this size distribution during <br />controlled placement, large voids in the underdrain were avoided while <br />porosity was maintained. <br />The excavation of the colluvial veneer at the toe resulted in an oversized <br />underdrain in that area. (Approximately 40 feet wide versus a requirement of 24 feet <br />wide). Photographs 17 through 20 show the controlled placement of the underdrain in <br />the toe area. <br />• Photograph 21 shows the size and distribution in a cross section of the underdrain. <br />Note the eight foot rod for scale. <br />Photograph 22 is also a cross section of the underdrain in the toe area to show the <br />height of the underdrain exceeds eight feet. <br />Due to the excavation at the toe and resulting oversized underdrain, the rock <br />stockpile was depleted and additional rock had to be produced to complete the head area <br />and mid-section of the underdrain. <br />Construction of the Head of the Underdrain System <br />Additional rock was produced by dozing and sorting down overshot from an <br />overburden production shot on the West side of the East Pit. This rock had the same <br />desirable characteristics as the rock that was produced for the toe area. Examples of the <br />rock sorted from the overshot are shown in photographs 23 through 25. <br />Prior to controlled placement in the head of the underdrain system, a new haul <br />road and dump areas were established with loaders and trucks. Photograph 26 shows the <br />completed lower reach of the underdrain and the haulage beginning for construction at <br />the head of the underdrain. <br />• <br />Section 2 -page 3 <br />