Open Pit Mine - Planning and Design-3rd Edition

Open Pit Mine - Planning and Design-3rd Edition

(Parte 6 de 7)

.0 OFFSITES .1 MINE DEVELOPMENT .2

.4 MILL SERVICES

.5 MILL SERVICE BUILDINGS

.6 CONCENTRATION

.01 Access Road

.04 • Primary Power

.05 • Fresh Water

- Haul Roads

.12 Equipment Erection Pad

.13 • Mine Clearing

.14 • Overburden Stripping

.15 • Waste Rock Stripping

.16 Waste Dump Development

Ore Stockpile Development

.19 Dump Drainage Control

.21 Service Roads

.2 Service Equipment

.23 Communications

.24 Mine Power

.25 Mine Shops

.26 Mine Offices

ANFO Facility

.28 Mine

Dewatering

Drainage Treatment

.32 Production Drills

.3 Shovels

.34 Dragline

Haulage Trucks .36 F/E Loaders

.37 Dozers

.38 In-Pit Crusher

.41 Mill Site Roads

Service Vehicles

.43 Communications

.4 Mill Power

Service Piping

.46 Reclaim Water System

.47 Emergency Equipment

.48 Tailings Pond

.49 Effluent Treatment

.51 Administration Building

.52 Warehouse

.53 Dry & First Aid

Emergency Power

Mill Shops

Core House & Lab

.61 Services

.62 Buildings

.63 Crushing

.64 F.O. Storage .65

Grinding

.6 Flotation .67 Tails

.68 T-F-D

.69 Cone. Storage

Figure 1.4. Typical work breakdown structure (WBS) directs for an open pit mining project (Lee, 1991).

2 Open pit initie planning and design: Fundamentals OPEN-PIT MINE PROJECT

.7 CONSTRUCTION SUPPORT

.71 Construction Management

.72 Construction Facilities

.73 Construction Equipment

.74 Construction Freight

.75 Personnel

.76 Camp & Catering

.8 DESIGN AND CONSTRUCTION MANAGEMENT

.81 Project Management

.82 Design

.83 Consultants

.84 Fees

.9 SPECIAL ACCOUNTS

.91 Overheads

.92 Owner's Team

.93 Land & Easements

.94 Insurance & Taxes

.95 Commissioning

.96 Environmental & Permitting .97

Geological Studies

.98 Mine Studies

.9 Mill Studies Figure 1.5. Typical work breakdown structure (WBS) indirects for an open pit mining project (Lee, 1991).

fosters understanding and appreciation of mutual requirements and objectives; even more importantly, it develops a shared commitment. 3. Format: a simple master time-bar schedule would be produced, displaying the study activities in a logic-oriented fashion. Brief titles and a reference number would be attached to each activity. For a simple in-house job, an operating company would probably stop at this point. However, for a major study on a new mining operation, the activity reference numbers and titles would be carried into a separate action plan booklet. Each activity would be described briefly, and a budget attached to it. 4. WBS reference: the most convenient way to organize these activities is by referencing them to the first and second levels of the WBS. 5. Number of activities: the practical limitation on the number of individual study activities would be of the order of one hundred.

Mine planning 23

Planning B • •¿-'.-V'-'-fv 3 B B

Exploration ~—1 • E _ i

Geostatistics/

Ore Reserves El 1 i •-, WB • a

Geotechnics • Oi 3 • Mine Design n

Process Design • Ancillaries Design i '• -''.--vil n Legal/Land Legal/Land

Environmental/

Permitting

Environmental/ Permitting

Economics/Financial B • i • • i ~ Id

Marketing Planning D BESSEaBB 9

Board Decision EXPLORATION f OPERATIONS

Figure 1.6. Bar chart representation for a mine feasibility/decision-making sequence (McKelvey, 1984).

Phase B. Organizing

Step 5: Identify additional resource requirements. While developing a comprehensive action plan, needs for additional resources normally become apparent.

Step (5: Identify secondary project team members.

Step 7: Develop organization chart and responsibilities. There are a number of ways to organize a project study team for a large study. A separate task force can be established by removing personnel from existing jobs and developing a project-oriented hierarchy, military style. This can work effectively, but can discourage broad participation in the evolution of the project. In a large company, a matrix system can be used very successfully, if used very carefully and with understanding. The management of a matrix organization is based on the management of intentional conflict; it works exceedingly well in a positive environment, and is an unequivocal disaster in an unfavorable environment.

Step 8: Develop second-level plans and schedules. Using the master time-bar, the action plan and the WBS as primary references, the enlarged project study team develops secondlevel plans and schedules, thus establishing their objectives and commitments for the balance of the study. These schedules are oriented on an area-by-area basis, with the primary team members providing the leadership for each area.

Step 9: Identify special expertise required. The project study team after reviewing their plan, with the additional information developed during Step 8, may identify a number of areas of

24 Open pit initie planning and design: Fundamentals the job which require special expertise. Such items may be packaged as separate Requests For Proposals (RFP's), and forwarded to pre-screened consultants on an invitation basis. The scope of work in each RFP should be clearly identified, along with the objectives for the work. A separate section provides explicit comments on the criteria for selection of the successful bidder; this provides the bidder with the opportunity to deliver proposals which can be weighted in the directions indicated by the project team.

Step 10: Evaluate and select consultants. Evaluation of the consultant's bids should be thorough, objective, and fair. The evaluations and decisions are made by the use of spread sheets which compare each bidder's capability to satisfy each of the objectives for the work as identified in the RFP. The objectives should be pre-weighted to remove bias from the selection process.

Phase C. Execution Step 1: Execute, monitor, control. With the project study team fully mobilized and with the specialist consultants engaged and actively executing well-defined contracts, the primary challenge to the project manager is to ensure that the study stays on track.

A number of management and reporting systems and forms may be utilized, but the base-line reference for each system and report is the scope of work, schedule and cost for each activity identified in the action plan. The status-line is added to the schedule on a bi-weekly basis, and corrections and modifications made as indicated, to keep the work on track.

1.8 CRITICAL PATH REPRESENTATION

Figure 1.7 is an example of a network chart which has been presented by Taylor (1977) for a medium sized, open pit base metal mine. Each box on the chart contains:

- activity number, - activity tide,

- responsibility (this should be a person/head of section who would carry the responsibility for budget and for progress reports), - starting date,

- completion date,

- task duration. The activities, sequential relationships and critical/near critical paths can be easily seen. Figure 1.8 is the branch showing the basic mining related activities. This progression will be followed through the remainder of the book.

1.9 MINE RECLAMATION

In the past, reclamation was something to be considered at the end of mine operations and not in the planning stage. Today, in many countries at least, there will be no mine without first thoroughly and satisfactorily addressing the environmental aspects of the proposed

Mine planning 25 project. Although the subject of mine reclamation is much too large to be covered in this brief chapter, some of the factors requiring planning consideration will be discussed. In the western United States, a considerable amount of mineral development takes place on federal and Indian lands. The Bureau of Land Management (BLM) of the U.S. Department of the Interior has developed the Solid Minerals Reclamation Handbook (BLM, 1992) with the objective being 'to provide the user with clear guidance which highlights a logical sequence for managing the reclamation process and a summary of key reclamation principles.'

The remaining sections of this chapter have been extracted from the handbook. Although they only pertain directly to those lands under BLM supervision, the concepts have more general application as well. Permission from the BLM to include this material is gratefully acknowledged.

1.9.2 Multiple-use management

Multiple-use management is the central concept in the Federal Land Policy and Management Act (FLPMA) of 1976. FLPMA mandates that 'the public lands be managed in a manner that will protect the quality of scientific, scenic, historical, ecological, environmental, air and atmospheric, water resource and archeological values.' Multiple-use management is defined in FLPMA (43 USC 1702(c)) and in regulations (43 CFR 1601.0-5(f)) as, in part, the 'harmonious and coordinated management of the various resources without permanent impairment of the productivity of the lands and the quality of the environment with consideration being given to the relative values of the resources and not necessarily to the combination of uses that will give the greatest economic return or the greatest unit output.' In addition, FLPMA mandates that activities be conducted so as to prevent 'unnecessary or undue degradation of the lands' (43 USC 1732 (b)).

The Mining and Minerals Policy Act of 1970 (30 USC 21(a)) established the policy for the federal government relating to mining and mineral development. The Act states that it is policy to encourage the development of 'economically sound and stable domestic mining, minerals, metal and mineral reclamation industries.' The Act also states, however, that the government should also promote the 'development of methods for the disposal, control, and reclamation of mineral waste products, and the reclamation of mined land, so as to lessen any adverse impact of mineral extraction and processing upon the physical environment that may result from mining or mineral activities.'

In accordance with the National Environmental Policy Act (NEPA), an environmental document will be prepared for those mineral actions which propose surface disturbance. The requirements and mitigation measures recommended in an Environmental Assessment (ERA) or Environmental Impact Statement (EIS) shall be made a part of the reclamation plan.

It is a statutory mandate that BLM ensure that reclamation and closure of mineral operations be completed in an environmentally sound manner. The BLM's long-term reclamation goals are to shape, stabilize, revegetate, or otherwise treat disturbed areas in order to provide a self-sustaining, safe, and stable condition that provides a productive use of the land which conforms to the approved land-use plan for the area. The short-term reclamation goals are to stabilize disturbed areas and to protect both disturbed and adjacent undisturbed areas from unnecessary or undue degradation.

26 Open pit initie planning and design: Fundamentals Figure 1.7. Activity network for a feasibility study (Taylor, 1977).

Mine planning 27

Feasibility report Volumes:

1. Geology, ore reserves & mining 2. Metallurgy 3. Capital & operating cost estimates 4. Legal, finance & marketing 5. Summary & economic analysis

28 Open pit initie planning and design: Fundamentals

Figure 1.8. Simplified flow sheet showing the mining department activities.

1.9.3 Reclamation plan purpose

The purposes of the reclamation plan are as follows: 1. Reclamation plans provide detailed guidelines for the reclamation process and fulfill federal, state, county and other local agencies requirements. They can be used by regulatory agencies in their oversight roles to ensure that the reclamation measures are implemented, are appropriate for the site, and are environmentally sound.

2. Reclamation plans will be used by the operator throughout the operational period of the project and subsequent to cessation of exploration, mining, and processing activities. In turn, responsible agencies, including the BLM, will use the reclamation plan as a basis to review and evaluate the success of the reclamation program.

3. Reclamation plans should provide direction and standards to assist in monitoring and compliance evaluations.

1.9.4 Reclamation plan content

The reclamation plan should be a comprehensive document submitted with the plan of operations notice, exploration plan, or mining plan. A reclamation plan should provide the following:

1. A logical sequence of steps for completing the reclamation process. 2. The specifics of how reclamation standards will be achieved. 3. An estimate of specific costs of reclamation. 4. Sufficient information for development of a basis of inspection and enforcement of reclamation and criteria to be used to evaluate reclamation success and reclamation bond release.

The reclamation plan shall guide both the operator and the BLM toward a planned future condition of the disturbed area. This requires early coordination with the operator to produce a comprehensive plan. The reclamation plan will serve as a binding agreement between the operator and the regulatory agencies for the reclamation methodology and expected reclamation condition of the disturbed lands and should be periodically reviewed and modified as necessary.

Although the operator will usually develop the reclamation plan, appropriate pre-planning, data inventory, and involvement in the planning process by the regulatory agencies, is essential to determine the optimum reclamation proposal. Most determinations as to what is expected should be made before the reclamation plan is approved and implemented.

It is expected that there will be changes to planned reclamation procedures over the life of the project. Any changes will generally be limited to techniques and methodology needed to attain the goals set forth in the plan. These changes to the plan may result from oversights or omissions from the original reclamation plan, permitted alterations of project activities, procedural changes in planned reclamation as a result of information developed by on-site revegetation research undertaken by the operator and studies performed elsewhere,

Mine planning 29 and/or changes in federal/state regulations. Specific requirements are given in the next section.

In preparing and reviewing reclamation plans, the BLM and the operator must set reasonable, achievable, and measurable reclamation goals which are not inconsistent with the established land-use plans. Achievable goals will ensure reclamation and encourage operators to conduct research on different aspects of reclamation for different environments. These goals should be based on available information and techniques, should offer incentives to both parties, and should, as a result, generate useful information for future use.

1.9.5 Reclamation standards

An interdisciplinary approach shall be used to analyze the physical, chemical, biological, climatic, and other site characteristics and make recommendations for the reclamation plan. In order for a disturbed area to be considered properly reclaimed, the following must be complied with:

1. Waste management. All undesirable materials (e.g. toxic subsoil, contaminated soil, drilling fluids, process residue, refuse, etc.) shall be isolated, removed, or buried, or otherwise disposed as appropriate, in a manner providing for long-term stability and in compliance with all applicable state and federal requirements:

(Parte 6 de 7)

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