Waste

 

Pre-operational (Planning and Design) Phase

The amount of extractive material that will arise is determined partly by the geology of the deposit and partly by the methods of excavation and processing of the mineral. At the pre-operational phase, all the sources of extractive material that will arise must be identified and quantities that will arise from each source predicted.

In relation to extractive material that arises because of inherent properties of the geology of the deposit, the following information and assessments are needed:

1. Determination of the total volume of overburden (including organic soil) that will arise, calculated by measuring the volume between the original ground surface and the rockhead surface.
2. Representative sampling of the organic soil layers so that reliable estimates of average thicknesses and top and subsoil volumes may be made.
3. Adequate representative sampling and geological interpretation of the deposit to determine the amount (if any) of material that will be excavated and rejected in situ or immediately before the crusher circuit.

In addition, an estimate will need to be made of the extractive material that will arise from processing the material either because of its geology (e.g. the proportion of silt and clay in a sand and gravel deposit) or because of market constraints (e.g. surplus fines or 'quarry dust' production that cannot be sold).

The quarry designs produced at this stage must include provision for permanent and/or temporary accommodation of these materials in tips or as backfill, taking account of minimising landscape and other environmental impacts, the need for the structures to be stable, and the need to reduce to a minimum the need to re-handle the materials (leading to excessive cost). 469

As described in A Quarry Design Handbook, L0060 there are four distinct stages in the process of designing the operation itself and quarry waste must be accounted for at every stage:

• Reserve estimation (including estimation of quantities of mineral and waste).
• Conceptual design (including refinement of design of final excavations and associated estimates of the volumes of quarry waste arisings, and design of permanent and temporary tips and related structures to accommodate the anticipated volumes of organic soils and quarry waste).
• Detailed design of final void (including permanent waste storage arrangements and deployment of materials in final restoration, whether in tips, incorporated in backfill or as soil forming or improving material).
• Phasing of operations (including detailed design of working faces at different stages of pit development and scheduling of waste material storage and permanent placement). 468

 

Continued with Operation.

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