HD,
The "dry stacking" area is where the non-gold, non-silver, unusable waste is placed until it can be disposed of meeting EPA rules.
This was posted by CGFIA on 14 Feb 2011:
Colorado Goldfields is developing a dry stack approach for tailings disposal at its Pride of the West Mill. Although used extensively in other parts of the world, such as Chile and Mexico, this is an innovative method of tailings disposal for the US and Colorado. Mines using dry stacking in the US include: Greens Creek, Pogo, Nixon’s Fork, and Kensington: all located in Alaska. Elsewhere TVX Gold in Montana, JR Simplot in Idaho, and Mineral Ridge in Nevada dry stack talings. “This approach to tailings disposal should remove all regulatory agency concerns surrounding the existing tailings ponds since those ponds will be reclaimed. Furthermore, and maybe even more importantly, this approach will increase the ultimate useful life and financial viability of the mill by several years,” stated Stephen C. Fearn, consulting Registered Professional Engineer for Colorado Goldfields.
Lee Rice, President & CEO of the company, described dry stack plan and its importance: “Moving forward we will develop a dry stack method of tailings disposal as part of a new permit amendment.
In a filtered tailings or dry stacking system, the mill tailings are filtered (de-watered) to remove approximately 85% of the water at the mill plant itself. The resulting material is approximately 85% solids and 15% water and can be transported by belt conveyor or trucks to a disposal area where they can be placed in an environmentally contained area and handled with earthmoving equipment.
“Utilising this approach for tailings disposal will remove some of the issues associated with our prior permit amendment, such as:
•Providing improved long term geotechnical stability of the tailings disposal area
•Reducing concerns about potential seismic activity
•Greatly reduce environmental risks of contamination of ground and surface water
•Making overall compliance with environmental regulations much more efficient and straight forward.
“We will also realise some immediate benefits from this dry stack approach, such as:
•Smaller environmental footprint for tailings disposal area
•Smaller operating area at any one time, which is easier to manage
•Vastly improved management of tailing disposal operations during winter season, which is approximately seven months of the year
•Facilitates the ability to use tailings for mine backfill to improve underground ore extraction efficiency and reduce need for additional tailings disposal area
•Conserves water use in the milling process
•Lower long-term environmental liability from possible failure of conventional tailings dam structures.
AI
