The wastewater treatment lagoons serving the Olympic Dam mine site had reached the end of their workable life as they did not have sufficient volume for the site population and there were known to be sinkholes in the base of the secondary lagoon. As part of the definition phase of the project, BHP Billiton was seeking a detailed design of a low cost solution that would satisfy environmental requirements.
Tonkin Consulting was engaged to design and document the preferred solution, to a detail suitable for tender and construction. Schedules were also developed for various stages of the project for integration into BHP Billiton’s master schedule. Tonkin Consulting was also responsible for facilitation and participation in a HAZOP/HAZID/HAZCON workshop with BHP Billiton stakeholders.
The preferred solution as determined by BHP Billiton was primary treatment followed by disposal via evaporation. Tonkin Consulting sized the lagoons based on baseline populations, “shutdown” populations, local climatic conditions, lagoon freeboard and minimum detention times. The horizontal and vertical layout of the lagoons was designed based on proposed future works on the site, existing services and achieving a relatively even “cut-to fill” ratio for earthworks.
Other features of the design include provisions for leakage detection (in accordance with EPA requirements), solar-powered flowmeters, lagoon liners, access roads, fencing, accessible valve installations and a rising main inlet structure.
Supporting documents to the design will include a technical specification, design report, maintenance schedule and decommissioning plan.
The focus during design was on producing a solution that was robust, safe and fit for purpose.