1999-08-23_HYDROLOGY - M1999051

• Permit No: M1999051
• IBM Index Class Name: HYDROLOGY
• Doc Date: 8/23/1999
• Doc Name: Surface & Ground Water Monitoring Plan
• From: TRC Hydro-Geo Consultants
• To: DRMS
• Media Type: D
• Archive: No

A qualitative environmental risk assessment
can be used to describe the risks associated
with the development of a new mine and to make
an evaluation of the adequacy of its design for
environmental protection. The relative
magnitude of risk associated with selected
failure modes and exposure /consequence scenario
assessments is the final result of a qualitative
risk assessment. These failure modes are based
on site specific areas and components, and
mining and construction phases.
The four steps of a risk assessment (hazard
assessment, exposure assessment, consequence
assessment, and risk characterization) are used
in the development of a qualitative risk
assessment. Relative magnitudes (using a five
point scale of negligible to high) for each
step, can be quantified in a qualitative risk
assessment. Development of the descriptors for
the relative magnitudes in each step is a very
important part of a qualitative risk assessment.
The success of a qualitative risk assessment
depends on the adequacy of the information base
and the subjective judgements made in each step.
The quality of the risk assessment is,
therefore, dependent on the experience of the
assessors.
A mining project in a sensitive coastal
environment is presented as an example to
demonstrate the application of a qualitative
risk assessment.
INTRODUCTION
Environmental impacts from mining operations
have been a significant factor in the last
century. This was especially the case prior to
the development of a better understanding of
environmental processes and the potential
impacts of acid rock drainage (ARD), and
associated heavy metals, or the uncontrolled
disposal of tailings and waste rock (Smith,
1987). Much care has been exercised over the
last two decades in designing and operating
mines to limit the environmental impacts as far
as possible. All new mines are specifically
designed with mitigative methods to manage such
potential environmental impacts. Attention is
directed to ARD impacts, safe disposal of mine
waste rock and tailings, transportation and
storage of chemicals and fuels, and final
reclamation.
A qualitative risk assessment can be used to
address all project systems and activities that
may potentially pose a risk to the environment.
QUALITATIVE ENVIRONMENTAL RISK ASSESSMENT FOR
MINE DEVELOPMENT
Dirk Van Zyl, P.E., Ph. D.
Principal, Golder Associates, Inc.
Denver, Colorado
Samuel Bamberg, Ph.D.
RA Consultants
Aurora, Colorado
19
Chapter 3
It can systematically assess if the control
and management systems designed for protection
of sensitive ecosystems are adequate. The
results of the assessment can help to identify
key elements in the project that pose higher
risks due to uncertainties in design. These
assessments can then be used to make
recommendations to further manage and reduce
risks as the project is developed.
QUALITATIVE RISK ASSESSMENT
The general principles of a risk assessment
are well summarized by Kaplan and Garrick
(1981):
"In analyzing risk we are attempting to
envision how the future will turn out if we
undertake a certain course of action (or
inaction)." Fundamentally, therefore a risk
analysis consists of an answer to the following
three questions:
► What can happen? (i.e. what can go wrong ?)
► How likely is it that that will happen?
. If it does happen what are the
consequences ?"
Risk assessments can be performed using
various levels of sophistication depending on
the amount and accuracy of data available. A
qualitative risk assessment uses descriptors
throughout to express the level of risk. The
definitions of the descriptors are presented in
terms of the magnitude or concentration of
contaminants.
The results of a qualitative risk assessment
can be used to:
a) Document the evaluation and decision -
making process. Although differences of
opinion may exist about the definitions of
the descriptors, the process is well -
documented;
b) Express the relative risk associated with
specific activities or design elements;
and,
c) Select those failure modes or release
mechanisms that may result in significant
risks. These mechanisms can then be
further developed in quantitative risk
assessments.
A qualitative risk assessment can be
performed in a systematic approach using four
steps (Van Zyl, 1987):