Contractor and mining services major STRACON has announced the award of the vertical construction of the TMF (Tailings Management Facility) buttress tailings dam and the expansion of the WRF for Hudbay’s Constancia copper project in Peru, for a period of three years.
STRACON stated: “Once again, we appreciate the continued trust that Hudbay has placed in us for over 12 uninterrupted years. We will continue to contribute our expertise to achieve the success of this project and further the generation of sustainable mining.”
At Constancia, as outlined in its latest NI 43-101 technical report from 2021, copper tailings flow by gravity from the two copper rougher tailings lines, and by pumps from the cleaner scavenger tailings line, to a 75 m diameter tailings thickener, where it is thickened to 58% solids. Thickened underflow is then pumped to the tailings dam. The thickener overflow gravitates to the process water tank where it is used in the grinding and copper roughing circuits.
The tailings pumping system consists of five centrifugal pumps in series with an HDPE lined steel pipe that crosses the Chilloroya valley. The pumping station at the plant site is designed to take tailings thickener underflow and dilution water and pump the mixture to the tailings dam on the other side of the valley. The pipeline follows the haul road route to save costs, increase maintenance access and reduce land disturbance. The road is built at low slope angles, typically less than 10%. The tailings pipeline has a maximum inclination of 12%. This is less than the angle of repose of the settled solids in the slurry, which is 15°. Consequently, if there is an un-programmed shutdown, for example a power outage, the slurry can sit in the line without having to be discharged or flushed. To reduce the risk of plugs during startup, all of the pumps in the pump station are fitted with variable speed drives.
The tailings pumping train can operate with as few as three pumps in operation allowing for extended maintenance times and coordinating with mill liner changes to minimise downtime. Under a normal scheduled stoppage, process water will be used to flush the solids from the line into the tailings dam.
The Potentially Acid Generating and Non Acid Generating Waste Rock Facilities (PAG & NAG WRF) are located in the Cunahuiri Valley east of the Constancia Pit and provide storage for the PAG and NAG waste based on the updated mine plan developed in 2017. The facilities receive mine waste material from the operation of the Constancia pit and from the Pampacancha pit. Underdrain systems include groundwater underdrains to collect the water to WRF Retention.
