❓ Question regarding the stability testing of Alcoa's tailings dams in WA, prompted by a media report. The Minister's answer outlines testing procedures, but declines to table specific reports, citing WorkSafe regulations and Alcoa's public disclosures.
AnsweredQoN 2227Legislative Council
QuestionView source ↗
I refer to Peter Milne's article in WAtoday, on 2 September 2024, 'Alcoa's mountains of red mud fail to pass stability checks', and I ask: (a) what testing has been done on each of the 21 tailings areas across Alcoa's three Western Australian sites, Pinjarra, Wagerup and Kwinana, respectively; (b) what were the results of this testing in (a); (c) could the Minister please table the reports from this testing in (a); (d) if no to (c), why not; and (e) were the tests, and any subsequent reports, done by an independent consultant and subsequently peer-reviewed by another independent consultant?
AnswerView source ↗
Answered
27 November 2024
Responded by
Leader of the House representing the Minister for Mines and Petroleum
Response time
10 days
a) A combination of tests are conducted at the tailing facilities, including:
1. Laboratory tests to assess the mechanical properties of the tailings
2. Laboratory tests such as consolidation, triaxial, and cyclic triaxial tests to examine compression characteristics and tailings strength
3. In-situ testing of the facilities to confirm material and water behaviour meets the design assumptions
4. Chemical tests on water and soil also help assess dam embankment safety.
b) Individual test results are assessed and validated by various methods including specific design analysis software with testing ongoing at Alcoa to increase confidence levels in material behaviour for design safety improvements.
c) No, these reports are not held by the Department.
d) Under the Work Health and Safety Act 2020 and Work Health and Safety (Mines) Regulations 2022, Western Australian mining operations are required to complete due diligence in design, construction, operation, and closure of the facilities to ensure they remain a safe and stable structure. WorkSafe Mines Safety does not have a record of every investigation report or test results that is completed for each mine site in Western Australia. An overview of findings by external consultants to conform to the Global Industry Standard in Tailings Management for the Alcoa Residue Storage Areas is available online at Alcoa’s website.
e) Stability analysis of the embankments have been undertaken by independent consultant and the Engineer of Record* (EoR).
1. Laboratory tests to assess the mechanical properties of the tailings
2. Laboratory tests such as consolidation, triaxial, and cyclic triaxial tests to examine compression characteristics and tailings strength
3. In-situ testing of the facilities to confirm material and water behaviour meets the design assumptions
4. Chemical tests on water and soil also help assess dam embankment safety.
b) Individual test results are assessed and validated by various methods including specific design analysis software with testing ongoing at Alcoa to increase confidence levels in material behaviour for design safety improvements.
c) No, these reports are not held by the Department.
d) Under the Work Health and Safety Act 2020 and Work Health and Safety (Mines) Regulations 2022, Western Australian mining operations are required to complete due diligence in design, construction, operation, and closure of the facilities to ensure they remain a safe and stable structure. WorkSafe Mines Safety does not have a record of every investigation report or test results that is completed for each mine site in Western Australia. An overview of findings by external consultants to conform to the Global Industry Standard in Tailings Management for the Alcoa Residue Storage Areas is available online at Alcoa’s website.
e) Stability analysis of the embankments have been undertaken by independent consultant and the Engineer of Record* (EoR).
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