Mine Tailings Dam Raise

The Red Dog Mine, located in Alaska’s DeLong Mountains, has operated since 1989 and is renowned for its high-grade zinc-lead-silver deposits discovered in the late 1960s. Operating in a remote Arctic environment, the mine faces logistical challenges due to seasonal ice conditions, requiring specialized infrastructure.
 
Its operations emphasize environmental stewardship and regulatory compliance, focusing on sustainable mining practices and community engagement. These principles were integrated into the subsequent project phases aimed at expanding the mine, ensuring that growth was managed responsibly and in alignment with these core values.

To enhance its tailings dam infrastructure in Alaska’s Arctic environment, the Red Dog Mine embarked on significant geotechnical construction and mine remediation projects. The primary focus was raising the tailings dam to increase the capacity of the tailings pond, a crucial step required under a permit to open a new mining pit and continue operations for approximately another 30 years. This expansion aimed to accommodate increased production and storage requirements for tailings, ensuring compliance with stringent safety and operational standards while supporting ongoing extraction activities. The project also prioritized maintaining operational capability and readiness for future growth.

The project team completed work on three phases of the main tailings dam raise, including Stage VIII (2011), Stage IX (2013) and Stage X (2016).  Stage VIII, involved constructing approximately 18,000 square feet soil-attapulgite cutoff wall, 560 feet long and up to 34 feet deep, to initiate the expansion along the wing wall of the main tailings dam. This phase also included tying into an existing geomembrane curtain wall within the main tailings dam to transition into the new soil-attapulgite cutoff wall.  Stage IX focused on constructing an additional 18,000 square foot section soil-attapulgite slurry wall tying into the end of the Stage VIII cutoff wall. In Stage X, the project team completed the final 690 linear foot section of the extension of the soil-attapulgite cutoff wall.

The project involved careful planning to transport equipment from the Port of Seattle to the ice-bound Port of Red Dog.  This included specialized equipment, such as a Komatsu PC 1250 long reach excavator, batch plant, ancillary equipment and supplies including a contingency of spare parts.  The total time to transport from Seattle to the Port of Red Dog was approximately 3 weeks depending on weather.  Once the equipment arrived at the Port, it was loaded onto trucks and hauled 50 miles up the mine road to the mine site.

In general, each phase involved excavation up to 34 feet into moderately weathered bedrock and frozen subsurface soils and mixing and placing backfill using specialized materials, such as attapulgite and kaolin clay. Each cutoff wall was capped with a soil-slag-cement backfill to act as protective cover over the top of the cutoff wall.  Work was completed by working up to 12 hours per day and 7 days per week.  Each phase of the project was completed within a stringent 5-week timeframe during a limited construction season between July and August. It was critical to complete the project on time to meet the milestone deadline for transport out of the mine before winter and encroaching sea ice shutdown the Port.

Even with logistical challenges, our team completed each phase of the project on time and within budget. We strictly followed safety and environmental standards, using advanced geotechnical construction and mine remediation techniques to strengthen the mine’s operational integrity.  This timely and cost-effective geotechnical construction and mine remediation ensured readiness for future dam raise phases, reinforcing ongoing safety and operational enhancements.

The results from these phases highlighted our team’s crucial role in improving seepage control and supporting the mine’s expansion. Despite the challenges of the remote location and limited construction windows, Forgen completed each phase of the project on time and within budget. Our expertise in geotechnical construction and mine remediation was essential in protecting the mine’s operational integrity and ensuring it met environmental standards for future work.