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failures. Its recommendations include: detailed site investigation; state-of-the-
art procedures for design, construction, and operation; routine monitoring;
safety audits; and occasional specialist reviews.
Experience elsewhere indicates the desirability of corporations developing
an impoundment or tailings management system that addresses policy,
commitment, planning, implementation, checking, corrective action, and
management review. The guidelines developed by the Mining Association of
Canada (MAC, 1998) are an example. Coal operators are integral stakeholders
in risk management and reduction. The committee suggests that coal operators
develop an industry-wide procedure for evaluating impoundment management
systems that could be adapted to specific properties and corporations.
RISK ASSESSMENT AND MANAGEMENT
In response to the basin failure at Inez, Kentucky ( Sidebar 1.12 ), MSHA
and a number of state agencies have initiated surveys to assess the risk
associated with current impoundments. The committee agrees that identification
of those impoundments within the existing inventory that have the greatest risk
of failure has significant value. However, the two classification systems MSHA
currently uses (see Chapter 1 ) are not consistent with accepted definitions of
risk. The risk associated with a failure is defined as the product of hazard (the
potential for a failure to occur) and the consequences of that failure (loss of life,
costs of repairing damage to structures or facilities, environmental impacts). An
impoundment could have relatively low risk if consequences of a failure were
low even though the probability of a failure was moderate. On the other hand,
an impoundment with a low probability of failure could be assigned high risk if
the consequences of failure, in terms of danger to human life, damage to
valuable structures or the environment were large. The pair of MSHA
classification systems currently use the term hazard in a way that is not
consistent between the two classifications system. In the first classification
scheme, which deals with potential impacts of embankment failures, the term
hazard refers to the consequences of failure. That classification system makes
no attempt to assess the probability of a failure event for individual
embankments. The second classification scheme, which deals with basin
failures, comes closer to the standard definition of a risk assessment. That
system includes an assessment of the proximity of underground workings and
the potential for a failure that would lead to a release of water or slurry from the
basin area into underground mine workings. In addition, the
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