ERR Guideline on Geotechnical Considerations for the Extractive Industry

DR ELIZABETH GIBSON, General Manager of the CMPA provides a report on the workshop.

The meetings were convened on 10 May 2019 and 14 June 2019 by Earth Resources Regulation, DJPR (ERR), with representatives from CMPA (Basil Natoli, BCA Consulting and Elizabeth Gibson) and a nominated geotechnical engineer Sanjive Narendranathan, (GHD) and CCAA to develop a guideline on geotechnical considerations for the extractive industry. Karen Sonnekus (Senior Geotechnical Engineer, ERR) was asked to develop a guideline by John Mitas (former Chief Inspector of Mines, ERR) in 2011 on commencing employment with ERR. ERR is looking for a practical and useful guideline for the extractive industry that complies with the MRSD Act 1990 (part 1 2 (b) (i)). The CMPA Guideline for Working Safely with Geotechnical Risk in Quarries was distributed to the attendees to assist with ERR’s guideline development.

The following issues were discussed:

• Terms of reference: The guideline will apply to open pit quarries and terminal and rehabilitated batters. It will not apply to open pit mines, operational batters or dam embankments. Stockpiles and waste dump slopes may be also be included. The intent is to complete the guideline by 30 June 2019.
• ERR versus WorkSafe: Conflicting or wrong advice may be given by WorkSafe and so representatives need to be included in the development process. WorkSafe attended the second meeting with a view to having a consolidated guideline.
• Geotechnical Risk Zones (GRZ): Reference to GRZ may be removed
• Greenfield sites: The concept that a full geotechnical assessment on a Greenfield site is not particularly useful until the site is opened was recognised by ERR.
• Complexity: ERR stated that that the extractive industry generally does not need the level of complexity that mines require.
• Safe and stable: Batter gradient will be process driven and not specified, for example, 1:3.
• Geotechnical review: It was proposed that a simple review (for a non-complex site) be conducted to determine whether a geotechnical assessment is required.
• Slimes dams: ERR is proposing a register of slimes dams that have been capped. ERR is going to rely on CMPA’s Slimes management guideline once draft (in 4-6 weeks) has been reviewed.

The focus of the 2nd meeting was to discuss the Draft Geotechnical guideline for terminal and rehabilitated slopes (7 June 2019).

The following issues were discussed:

• Simple sites (definition still to be determined): A letter from a competent person to proponent that a full geotechnical stability assessment is not required. A standard proforma letter will be in the proposed guideline. It was estimated that this would cost the proponent ~$1K.
• Complex sites (definition to be determined): A geotechnical stability assessment conducted by a competent person is required. For a greenfield site an initial geotechnical stability assessment will be conducted and will be dependent on information available and the professional opinion of the geotechnical engineer. A full geotechnical stability assessment may be required once the site has been opened.

Further updates will be given as the Guideline is developed

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