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Pre-ripping

Pre-ripping occurs between the landscaping and soil return stages of the rehabilitation process. 
 
The objective of pre-ripping is to relieve mining-related soil compaction and fracture the ground. This is important because the pit floor becomes much harder than the surrounding non-mined areas due to heavy vehicle compaction and the removal of the naturally friable bauxite ore during the mining process.
 
Research has shown that deeper ripping helps the vegetation grow into a sustainable forest by allowing roots and water to penetrate through the soil profile.
 
Alcoa has made commitments to government to pre-rip all pits and to ensure that the majority of each pit is ripped to a minimum depth of 1.2 m.  
 
More stringent internal Alcoa standards were developed to ensure these commitments are met - ripping 80% of the pit (excluding batters and waste islands) between 1.2 and 1.5 m or greater. 
 
A real-time monitoring system located in the cab of the dozer is used to monitor the area that has been ripped and the depth of ripping.   This monitoring system provides guidance and enables the dozer operator to meet target for the pit and identifies areas where rework is required prior to shifting to another location. 
 
Following pre-ripping, a grader is used to smooth and prepare the surface for the return of topsoil and overburden.
 


A Bulldozer, pre-ripping a landscaped pit using a

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A Bulldozer, pre-ripping a landscaped pit using a winged-tine.

dozer with tine.

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A winged-tine, used to pre-rip the landscaped pit, attached to the back of a bulldozer. The tine disturbs the structure of the ground beneath the soil thereby helping to relieve compaction caused by mining equipment.

Prerip

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After pre-ripping, a grader smooths the pit surface in preparation for a scraper to return topsoil and overburden.

Global positioning system.

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The global positioning system in the bulldozer cab allows the dozer operator to see real-time ripping depth.