Worsley Mine Development CONTINUING OPERATIONS Worsley Alumina

FACT SHEET – INLAND WATERS SEPTEMBER 2020

BACKGROUND The objective for this component The northern portion of the Primary Assessment of the environmental review is to Area (PAA) including the Worsley Mining Development maintain hydrological regimes Envelope (WMDE) and the Bauxite Transport Corridor (BTC) falls mainly within the Murray River and and quality of groundwater Tributaries Surface Water Management Area and and surface water so that over two sub-areas (Hotham and Williams Rivers). environmental values are protected. The South Dandalup Dam Catchment Area Priority 1 (P1) and Priority 2 (P2) Public Drinking Water Supply Area Within this assessment inland (PDWSA) is located along the northern boundary of the waters includes the occurrence, WMDE with these catchments managed by Department distribution, connectivity, of Water and Environment Regulation (DWER). movement and quantity of all The southern portion of the PAA lies within the Collie inland waters including chemical, Surface Water Management Area in the Brunswick sub- physical, biological and aesthetic area and is entirely contained within the Augustus River characteristics. catchment. The Augustus River is a key water feature within and downstream of the proposed Contingency Bauxite Mining Envelope (CBME) and is a tributary of the Brunswick River, which is used primarily for agricultural purposes. The confluence of the Augustus River with the Brunswick River is approximately five kilometres downstream to the west of the CBME.

Existing groundwater monitoring information indicates declining groundwater levels that is reflective of decreasing rainfall trends observed in the region over the last few decades. Where groundwater levels are measured in mining or agricultural areas the groundwater trends observed are relatively stable. This stabilisation of groundwater levels, against a declining trend in naturally vegetated locations is considered a consequence of decreased evapotranspiration due to INTRODUCTION clearing. South32 Worsley Alumina is an integrated bauxite The Hotham River and its tributaries support a diverse mining and alumina refining operation in the South number of fish and crayfish species endemic to the West of Western Australia with a proud track record south west region of WA as well as a number of spanning more than 35 years. other aquatic species. The Hotham River locally and The Worsley Mine Development is the next phase of the Murray and Williams Rivers more regionally are bauxite mining near Boddington, providing access to considered important ecosystems for freshwater fish future reserves and resources to sustain production at migration. None of the native crayfish and native fish our Worsley Alumina refinery near Collie. species recorded were considered rare or restricted in distribution. Of the fish species, Western Minnows, The project is a key enabler for Worsley Alumina to Pygmy Perch and Nightfish are the most abundant and continue to deliver benefits to the Peel and South West widespread. regions, and Western Australia more broadly, for many years to come. Data used to inform this assessment includes the The project is currently subject to a State and historical groundwater and surface water monitoring Commonwealth environmental approvals process, with databases of the Boddington Bauxite Mine (BBM) and a comprehensive environmental review undertaken and Worsley Alumina refinery, regional DWER databases and an eight-week public review period set to commence some information from the neighbouring Boddington later this year. Gold Mine. POTENTIAL IMPACTS MITIGATION Worsley Alumina has demonstrated that Potential impacts to inland waters from the impacts to inland waters from existing implementation of the project include: operations can be managed and mitigated • Changes to groundwater levels as a result of increased through the implementation of the Water clearing; Management Plan. • Decline of aquatic fauna from changes in flow regime and We will continue to employ similar water quality; management practises to manage key risks associated with the continuation of mining at • Deterioration or change in background water quality such the BBM. Worsley Alumina’s activities in the as salinity due to indirect impact of mining activities; PDWSA will be in accordance with any working • Changes to vegetation structure in Groundwater arrangements with the DWER. Dependent Ecosystems (GDEs) because of groundwater rise; The Water Management Plan stipulates the current management strategies to manage • Potential impacts on surface water and groundwater the existing operations and outlines the values through increased water use; conceptual continuation of these strategies • Riverbank erosion, sedimentation, scouring of streams or into new mining areas as the project is release of excessively turbid water because of clearing implemented. Specific controls will be riparian vegetation and alteration of surface water implemented for the design and construction drainage patterns; of the river crossing infrastructure to ensure river function is not impeded. • Contamination of groundwater and/or surface water from potential acid sulfate material and contaminants during Progressive rehabilitation and re-vegetation removal of soils and sediment at river crossings; practises of disturbed land is an important strategy that Worsley Alumina has • Contamination of surface water because of spills or implemented and will continue to implement to stormwater run-off; and ensure impacts to inland waters are minimised • Contamination of groundwater because of seepage of as a result of the continuation of mining. incorrectly stored chemicals. Successful rehabilitation can start to alleviate Potential impacts of the project are expected to reflect groundwater mounding, salinity risks, the current risk types and magnitude of Worsley Alumina’s excessive erosion and stormwater run-off at current operations. Worsley Alumina currently employs a the BBM. Progressive rehabilitation practises Water Management Plan to describe its current expected are well understood at Worsley Alumina and impacts, management, monitoring and mitigation measures will continue to be refined to ensure successful for its current operations. outcomes are achieved.

PREDICTED OUTCOME Worsley Alumina’s robust management practises for the existing operations are considered appropriate and effective for managing any potential impacts to inland waters associated with the project. Observations of Worsley Alumina’s current operations have suggested that current bauxite mining practises do not appear to cause increased salinity risks above background conditions. It is therefore expected that the project will meet the Western Australian Environmental Protection Authority’s objective for inland waters. More detailed information is provided in Section 5.5 of the Environmental Review Document.

For further information please contact us on [email protected] or visit us at www.south32.net/worsleyminedevelopment