Knight Piésold was appointed by Palabora Copper Mine (PMC) to replace the two existing gravity decant siphon systems at their Main tailings storage facility (TSF). The system infrastructure showed signs of distress. It also needed repositioning due to the future growth plans of the TSF and the pool migration. Knight Piésold was approached to put forward engineering options to address the situation.
Knight Piésold designed a low maintenance, easy to operate, and cost-effective siphon decant system that would draw supernatant water off the surface of the pool and discharge it to the main return water dam.
Knight Piésold designed the replacement system consisting of the glass fibre siphon intake head, floating HDPE outfall pipe, and the galvanised access walkways. The system comprises two siphons: one in operation and one on standby. The siphon is controlled by two vacuum pumps, one to prime the 800 diameter outlet, while the second (smaller) pump draws off air accumulating at the crest of the siphon during operation.
The siphon is broken at an air inlet located 9 m below the pool level, to prevent excessive flow in the siphon pipe, which would empty the pool on the tailings dam. The system is raised from time to time to keep up with TSF elevation growth. The system was revamped in 2017 when the siphon intake heads and the access walkways were replaced. Latest technology materials design trends were implemented.
The main roles undertaken include: