Newmont’s Cripple Creek & Victor (CC&V) gold mine in Colorado operates two valley fill heap leach pads. These process areas are used to recover precious metals from ore that has been piled up on top of impermeable pads. A system of drip lines and irrigation piping around the heap distributes a leaching solution that separates the valuable metals from the ore.
One of CC&V’s heap leach pads, Valley Leach Fill (VLF1), is a 372 million ton leach pad that is more than 700 feet deep in some areas. Active stacking has been completed on VLF1, reaching the 10,400 foot elevation level (from sea level). As VLF1 was built or “coned up,” it created over 12 million square feet of side slope area, which makes up nearly 80 percent of its leachable area. While these side slopes have been leached intermittently since 1995, they will remain a significant contributor to CC&V’s production for years to come.
Side slope areas present a challenge, however, and have limited access. This makes them difficult to leach – and they have a high potential for washouts in the event that a drip line disengages from its adaptor. A washout can damage multiple benches and access roads on the leach pad, potentially creating a risk to the safety of workers and the stability of the environment.
To address this risk, leach pad metallurgist Zach Felkey developed two new excess flow valves (EFV) that can isolate flow when the pressure through a pipe increases beyond a specified set point. The “Check” and “Eddy” excess flow valves utilize two new mechanisms to achieve flow isolation. The Check EFV uses a swing check valve and a modified bushing to stop the flow of solution, while the Eddy EFV uses a tee, or wye, fitting with a ball in the side outlet of the tee. These EFVs allow for efficient operation by delivering quick interconnections to drip line adaptors while providing a reliable and robust safeguard to reduce the potential for washouts.
Side slopes present a challenge to CC&V’s operations team with their limited access and risk of washouts. With these two innovations, CC&V can have more confidence in its ability to safely and effectively leach side slopes.
Congratulations to Newmont’s Zach Felkey at CC&V for his innovative solution to address damaging washouts on leach pads!