Mine Closure - Mining and the Environment: From Ore to Metal - page 804

productive purpose. In many developing countries, companies are also concerned about
the security of payments made to funds to which government agencies may have access.
Experience is that rehabilitation requirements and i nal closure costs exceed initial esti-
mates, particularly in the following areas (USDA 2004):
●

Experience is that rehabilitation
requirements and fi nal closure
costs exceed initial estimates.

Interim management of process l uids;

●

The need for and cost of water treatment;

●

Detoxii cation and rinsing of spent ore from heap leach piles;

●

Closure of tailings impoundments;

●

Removal, isolation (liners/covers) or treatment of hazardous materials (chemicals,
spent ore, waste rock);

●

Site drainage, interim and long-term;

●

Monitoring and maintenance of the mine site during and after closure;

●

Indirect costs of closure/reclamation; and

●

Lack of site-specii c information at the time of mine planning.

By necessity, most i nancial mine closure instruments are initially estimated based on con-
ceptual mine plans. Actual mine operation, however, will differ from these initial plans as
the mine evolves and new information becomes available. Actual plans should be used to
revise mine closure estimates, and mine closure funds, at regular intervals. Finally, estimat-
ing mine closure costs requires considerable judgement that can only be gained through
experience. It is fair to say that mine closure costs are often underestimated if developed by
persons with inadequate education, training or experience.
Mining is dynamic. New ore deposits may be discovered during the mine operation,
and mine rehabilitation often occurs in parallel with operations. This raises the issue of
the period covered by the i nancial mine closure provisions. For example, mine closure
bonds may cover a single year, multiple years or the entire life of a mine. Selection of the
bond period may be based upon some logical stage of mine development, e.g. construction
or reclamation of major mine facilities like tailings ponds, heaps and mine facilities. Of
course the bond period needs to rel ect regulatory requirements.
What are the mine closure costs? No single formula can be used to arrive at exact esti-
mates. Each mine is a unique situation. However, common direct and indirect costs exist.
Direct costs that relate to rehabilitation tasks can be grouped into the following eight
categories (USDA 2004):
●

Estimating mine closure costs
require considerable judgement
that can only be gained through
experience.

Interim operation and maintenance;

●

Hazardous materials;

●

Water treatment;

●

Demolition, removal and disposal of structures, equipment and materials;

●

Earthwork;

●

Revegetation;

●

Mitigation; and

●

Long-term operation, maintenance and monitoring.

Clearly the occurrence of acid rock drainage adds signii cant costs in terms of mine wastes
rehabilitation and water treatment (IFC 2002). In the case of some mines, substantial
annual expenditures may be needed, virtually in perpetuity, to neutralize acid rock drain-
age from inactive workings.
Indirect costs commonly fall into the following categories (USDA 2004):

The occurrence of acid rock
drainage adds signifi cant
costs in terms of mine wastes
rehabilitation and water
treatment.

●

Engineering redesign;

●

Mobilization and demobilization;

●

Contractor's costs;

●

Government project management;