Today I was criticized for failing to clearly set out the project objectives. Damn me, I know what we are setting out to do. “But the rest of us do not,” was the reply. And so I wrote out the project objectives in deliberate detail. And that set me writing the rest of this posting. It may be entertaining; I hope it is informative; as least it should give you some idea of the issues and events involved in mine waste disposal engineering.
(The picture above is an origami folding I did. It is supposed to be a mother elephant looking after her young son.)
As in any project, set the project objectives before you do anything else. Here are some objectives grouped according to the major activities (tasks) that are commonly used in mine waste disposal projects.
Think of the planning stage as all the work that is involved in getting management, regulators, and the public to allow you to proceed to design and construct a new or expanded mine waste disposal facility. Thus we have site selection, pre-feasibility evaluation, feasibility evaluation, environmental impact assessment, permitting, community interaction, and so on. Hence some example project objectives.
- Select a site for the waste rock dump that results in least-cost operations.
- Select a new site for the tailings impoundment that balances cost, safety, impact, and community acceptance.
- Evaluate alternative heap leach pad layouts and hence select that with the highest probability of cost-effective operation.
- Identify and procure all permits needed to expand waste disposal operations.
Design is the compilation of drawings, specifications, reports, calculations, operations manuals, and contract documents that together make up the so-called facility design. Once these documents are in place, request for proposals to construct and operate may be sent out. Alternatively the documents may be given to field operators so they may begin operations. Hence some typical project objectives.
- Prepare the full set of design documents needed to issue a request for proposal to construct and operate a new tailings facility.
- Write a new operations manual for the waste rock dump extension that is planned for the valley with the soft foundation soils.
- Design and prepare detailed cost estimates for an alternative heap leach pad operation method.
- Identify, retain, and manage consultants to prepare a detailed evaluation of alternative approaches to increasing the capacity of the tailings facility and extending is operational life by at least ten years.
Construction includes building and putting in place the components need to safely operate the facility. Generally we think of these in three categories:
- Civil Containment Earthworks. These include the initial earthworks, embankments, berms, and other facilities needed to contain the wastes. Such facilities are best constructed by an experienced earthworks contractor or focussed mine staff.
- Civil Water Management Components. These include the drains, diversion channels, liners, sediment and return water ponds that are needed to manage surface water, control seepage, and deal with runoff. Again these are generally civil works and are best constructed by experienced contractors or experienced mine staff.
- Mechanical Facilities. These include installing the pumps, pipes, and spigots needed to transfer tailings and other fluids to the facility.
Hence typical project objectives related to this phase of work.
- Construct the civil and mechanical facilities during the summer months of FY 13 & 14 so that the expanded facility is ready to receive additional waste by the beginning of FY15.
- Manage multiple consultants and contractors involved in the design-build of a new heap leach pad in difficult terrain.
- Prepared phased construction plans so that provision of civil and mechanical facilities for the new dry stack is installed timeously but no sooner than absolutely required.
The initial works are in place. Mining begins, processing proceeds, and there are wastes to be disposed of. The operational teams are ready. Waste rock is dumped from the trucks and the tailings pipes flow full to the impoundment. The heap leach pad liners and drains are ready and the ore is dumped thereon and fluids seep into the mass to emerge at the toe with valuable minerals. Operation begins. Hence some typical project objectives.
- Operate the tailings facility in accordance with relevant and applicable regulations, standards of practice, operational plans and procedures, and to the overall benefit of mine operations and protection of human health and the environment.
- Improve heap leach pad operations by implementing a continuous improvement program aimed at cutting costs by at least ten percent and production by at least thirty percent.
- Revise access road layouts and surface trafficability with the objective of reducing waste rock dump truck tire wear by fifteen percent.
- Characterize the in situ tailings properties in order to identify and evaluate alternative depositional procedures leading to increased tailings density and hence facility capacity.
- Initiate and follow-through on a program to initiate interim and partial closure works constructed during operation in order to reduce closure cost obligation
Finally the day looms large: the mine has run out of ore and closure is real. If you have been prudent, you will have undertaken closure activities during operation and all that remains is final demolition, removal, and vegetation planting. If you have not, then now is the time to plan, implement, and pay for closure. There are many things to deal with: how to finance; what standards to adopt and implement; and who will do it? Hence we have seen these closure project objectives.
- Close mine waste disposal facilities in accordance with international good practice.
- Remove unwanted equipment and prepare the site for transfer to a third party that intends to turn the site into an expensive riding stable for the rich.
- Restore pre-mining conditions and ameliorate current and long-term potential impacts to surface water and groundwater.
- Undertake interim closure premised on the hope that the price of gold will soar and the mine can be reopened.