The concept design undertaken by JDSi was used in development of the Feasibility Study cost estimates and on approval to progress the project, JDSi were subsequently awarded the detailed design phase.
Earthworks was based on developing a design for the CGP3 area which would then be replicated for the future CGP4 plant site thus allowing all mechanical and structural designs to be used without change as relative levels between buildings and structures were identical.
Due to the high cost of importing fill from external borrow sources the final design needed to achieve a cut to fill balance. Once plant area designs were completed, several design iterations were modelled ranging from varying level differences between the two plant sites through to fixing the level difference and raising and lowering the entire project area.
As the in-situ materials ranged from sandy gravels to clays the design also considered maximising the amount of cut in “good” material. With the assistance of the Project Geotechnical Engineers, a specification and methodology were developed to ensure the poorer clays could be effectively used in the earthworks construction.
A condition placed on the Project Approval was that no stormwater was to discharge into the surrounding environment. To achieve this the plant area drainage was designed as open swales capable of carrying a 10 year rainfall event. These drains directed stormwater to a perimeter drain sized to carry a 100 year event. Overland flows from the various plant pads were also directed to this drain which discharged into a sediment basin sized to hold the 100 year event volume. In areas where stormwater was likely to be contaminated with ore or concentrate, flows were directed to wedge pits to capture and enable recovery of the material. All stormwater is pumped to a clearwater dam and reused in the production circuit.
Earthworks, roadworks and drainage were designed to limit the amount of clearing adjacent to a public road to provide a screen and minimise the visual impact of the facility.
