In 2019 Pantoro South Pty Ltd (Pantoro) and the Central Norseman Gold Corporation Pty Ltd (CNGC) announced a joint venture in the operation of the Norseman Gold Project (NGP), located at the town of Norseman in the Western Australian Goldfields. The project involved the development and mining of the Scotia and Cobbler pits.

What did we do for the Norseman Gold Project?

In order for the pits to be mined surplus water within the Scotia pit needed to be discharged into the adjacent Lake Dundas playa system, whilst the mining of the Cobber deposit had the potential to alter hydrological features within the adjacent Lake Cowan playa system. In order to gain approvals for this project an ecological risk assessment (ERA) was required to assess whether the proposed activities were likely to adversely effect the existing environmental values and condition of receiving environments. MBS Environmental (MBS) was thus engaged to perform a Tier 1 Ecological Risk Assessment for the proposed development which included:

• Characterising the physicochemical properties of the water to be discharged into the Lake Dundas playa system from the Scotia pit dewatering focusing on receptors such as lake sediments, associated biota, and the overall health of the lake ecosystem.
• Assessing the potential effects of the proposed Cobbler development on the lake ecosystemand lake hydrology.

The areas MBS assisted included:

• Reviewing baseline studies (e.g., flora and vegetation surveys, fauna surveys, hydrogeological studies) that detailed the environmental context for the assessment.
• Assessing the composition of Scotia pit discharge water against relevant default environmental guideline values (e.g. ANZG Freshwater ecosystem species protection, ANZECC Livestock
  Drinking Water Quality) to conduct a Tier 1 assessment.
• Calculating potential metal loading concentrations in lake sediments as a consequence of the development of the project and subsequent pit dewatering and discharge.
• Identification of key environmental values and sensitive receptors associated with the receiving environments.
• Assessing the potential risks to environmental receptors (i.e., sediment quality, flora, fauna) as a result of the release of water (e.g., volumes, potential contaminants, and stressors) into the environment following the source-pathway-receptor principle and conceptual model approach.
• Identification of management implications, based on the above, that should be considered when developing dewater discharge strategies and management plans.