In 2016, Environmental Engineers International was commissioned by the Indigenous Land Corporation (ILC) of Commonwealth of Australia to develop a stormwater management plan and design an evaporation pond for the Roebuck Live Export Depot in Broome, Western Australia.
The Department of Environment and Regulation had established a moderate risk of the worksite’s current system discharging nutrient rich stormwater from cattle holdings into groundwater and nearby water bodies. In which case, this would cause severe damage to the local eco-system by damaging plant growth and increasing toxicity of local river systems. Undoubtedly, this risk will only increase with any further expansion of the worksite.
Through 1D modelling, analysis of the 10-year average reoccurrence index (ARI) and worksite soil testing EEI were able to assist in creating a design report for a sitewide stormwater management system. This enabled Roebuck Export Depot to employ an appropriate evaporation pond to manage any oncoming rainfall. Evaporation ponds are generally constructed in order to prevent contaminated water stream from a process or catchment area from mixing with the natural water system. Solar energy is utilised to slowly evaporate the stored pond water, concentrating solid contaminants and allowing for their efficient removal.
Figure 1: Soil Sample Analysis
EEI recommended Roebuck Export Depot to implement a sedimentation pond prior to the evaporation pond to cater for site specific issues such as silting. This significantly reduced the ongoing maintenance requirements and costs of the project for the client.
EEI was also able to save the client capital costs by undertaking a risk assessment of the ponds constructed as unlined posts. The site soil permeability was higher than the required amount, indicating that the ponds would usually have to be lined. However, EEI looked closely at the depth to groundwater, phosphorus retention of the soil, the pond’s ability to foster conversion of ammonium nitrogen and recommended a exemption for the client. This exemption was approved by the department of environment and regulations, which saved the client a large capital and operating costs of lining the required ponds.