Nickel West Mine Closure

The erosion assessment formed part of the landform engineering scope of work for the Nickel West Mine Closure Study – Stage 2. It was intended to address gaps identified in the Stage 1 knowledge base summary. Erosion modelling analyses has been carried out for waste facilities at Nickel West’s Southern Region operations (in the Southern Region of the Goldfields). An Identification Phase Study (IPS) was also required.

The purpose of the study was to inform the process of generation and review of alternative slope options such that the selection of preferred alternative final landforms can be made and designs supported and developed (as part of future closure planning studies). The primary outcome of the IPS was the development of a preferred closure alternative, with subsequent closure studies (outside the current scope of work) comprising a selection phase, definition phase and execution phase.

The following facilities were modelled and assessed:

• Kambalda Tailings Storage Facility (TSF) KT2 as constructed and compliance profiles
• Kambalda TSF KT3A and TSF KT3B compliance profile
• Kalgoorlie granulated slag landform compliance profile
• Kalgoorlie hot slag landform compliance profiles for the Eastern slope and Southern, Western and Northern slopes of the facility of the facility
• In addition, surface water assessment scope of works for the North Region for the Nickel West IPS Mine Closure Study – Stage 2

Preliminary erosion modelling based on assumed erosion parameters has been carried out to assess the relative performance against erosion of waste rock dumps, tailings storage facilities and slag dumps at the various Nickel West Facilities. Two scenarios were considered, the as constructed profiles and the Nickel West FY 2015 mine closure plan compliance profiles. The Kambalda TSF is required to have a rock cover with no growth medium cover while the slag dumps at the Kalgoorlie smelter requires the addition of a sand over layer only.