The treatment system’s development required both a rigorous scientific and pragmatic engineering approach to solve the difficult site problems including, limited hydrological and chemical data, extreme precipitation and hydrological regimes, as well as a requirement to use locally sourced construction materials.
Specific design objectives included:
- Minimal financial outlay for construction
- Minimal operating costs
- Minimal maintenance and daily management
- Reduced contaminant load to meet 95-percentile discharge requirements
- Operate efficiently under the highly variable hydrologic regime
Based on available data, WorleyParsons developed a design model for a 3-stage passive treatment system. This consisted of:
- A primary waste stabilization pond with excess storm water retention
- Optional forced aeration rock drains
- Horizontal subsurface flow reed beds to remove waste
The design met all primary customer objectives and provided a simple and cost-effective option for the onsite treatment of wastewater arising from the mining operation.