Based on a 5 year mine plan and the West Angelas Deposit A – 2009 Q2 CEPN Numerical Groundwater Model Setup and Model Predictions, it was found that the existing Dewatering System at West Angelas was inadequate to maintain the water table beneath the future mine bench levels in Centre Pit North (CEPN) and Centre Pit South (CEPS).
Onyx Projects (OP) was initially commissioned to carry out a scoping study to determine the dewatering requirements for the CEPN and CEPS.
OP were further commissioned to provide:
- The engineering design for the turkeys nest, pumps, pipe work, standpipes and the tie-ins to the existing system required to dewater from the CEPN and CEPS;
- The engineering design for the pumps and pipe work for a stormwater pumping system;
- Construction implementation support and management of Contractors in collaboration with Rio Tinto Project Engineering to increase the capacity of the dewatering system by:
- Installing new dewatering bores in both the CEPN and CEPS;
- Installing a relift turkeys Nest on the saddle between central north and central south pits in order to transfer the water to the existing central north pit turkeys nest;
- Replacing the existing piping system to cater for the increase in pressures due to bench level progress;
- Installing a new waterstand system and upgrading an existing water stand installation;
- Installing a new stormwater removal system including two new relift stormwater pumps and temporary flanged piping.