 |
Following the completion of gold mining and milling operations in November, 1999, the 302-acre tailings impoundment was covered with a 3-6 foot layer of clay material known as saprolite.
This material, shown here being excavated, was recovered from an area later to be developed as a wetland, linking the North and South pit lakes. Kennecott used its existing fleet of equipment to mine the saprolite material. In total, 2.2 million tons were mined between January and July 2000. |
 |
The saprolite material was loaded and hauled to the crusher, reduced in size and processed through the milling circuit. The clay material was ground to a powder and then slurried to the tailings surface using the existing distribution system. Center-point discharge was used to build a cone of clay cover material from the middle of the tailings surface outward to the edge of the impoundment. This was followed by peripheral discharge, shown here, to create a channel conduit for future surface water flows. |
 |
Distribution of the slurried clay cover material was completed in July 2000. As the water drained from the clay material via the conduit created by the cover geometry, areas were seeded using low ground pressure equipment shown at left. The cleat-marks shown in this picture were instrumental in providing adequate protection for the grass seeds from high winds, typical at this elevation, and moisture retention. An area previously hydro-seeded in May, adjacent to the central access to the center of tailings, can be seen in the middle distance of this photograph. |
 |
Despite state wide drought conditions during 2000, the growth of cover crops on the tailings clay cover surface was very successful. Moisture retention by the clay cover material was instrumental in this success.
By year-end approximately 70% of the 302-acre site was successfully revegetated. |
 |
Waste rock excavated during operations, and temporarily stored in stockpiles, has been returned to the open pits where it will be submerged beneath the rising water levels. The displacement of air within the submerged rock ensures that no acid waters can be produced from those rocks containing sulfide material. At left is an area where waste rock has been removed (right side), and rock remaining to be moved (left) and returned to the North pit. Shown below is the North pit during flooding. December 8, 2000 |
 |
 |
| Sampling of the underlying surface (shown above) confirms that all potential acid-generating rock has been removed, after which, stockpiled topsoil is spread 12”-18” deep in preparation for seeding. Wherever feasible, the land surfaces have been returned to their original profile, as can be seen from this view (right) of the former waste rock storage area at the North pit. |
 |
 |
As plant facilities are decommissioned and removed, work begins to reshape the land surface. In this view the former location of the primary gyratory crusher is being reclaimed. When complete this area will form part of a wetland system carrying stormwater run-off to the South lake. |
 |
In the view at the left, clay material was removed to provide the cover surface for the tailings impoundment. In this July 2000 picture final grading, spreading of topsoil and seeding remain to be done. |
 |
By December 5, 2000 side slope growth to stabilize the area had appeared. Planting of wetland plant species in the lower areas will be completed in 2001. |
 |
Drilling and blasting the in-situ rock at the pit rims, followed by bulldozer work, reshaped the crests of both open pits. The objective was to create finished slope surfaces no steeper than 3H:1V, thereby ensuring minimal erosion, providing a suitable surface for plant growth and safe access for wildlife. |
In the view below left, taken in June 2000, blasting has been completed on the
southeast corner of the South pit. |
Immediately shown below is the finished form of the same
area in December 2000. Work on the western end of the pit rim remains to be completed. |
 |
Looking from the west at the end of December 2000, all pit rim sloping at the South lake has been completed. Final water levels in both lakes will be 10 feet vertically above the lowest point of the 3H:1V topsoiled slope. |