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EnviroMine:  Environmental Technology for Mining


Editor:
- University of British Columbia
 
Multiple Accounts Analysis (MAA)

by: Dr. A. Robertson and S. Shaw

The MAA is utilized as part of a plan development and evaluation process dealing primarily with value assessment and impact management; focussing on operational, financial, environmental and socio-economic issues.

A detailed course on how to complete a multiple accounts analysis is available on Edumine. A summary of the MAA process, and a description of how it can be utilized in closure planning is provided here.

Introduction
The MAA is a multi-stakeholder, multi-disciplinary tool that provides the means by which evaluators can select the most suitable, or advantageous alternative, from a list of alternatives, by weighing the relative benefits and costs (or losses) of each. The method involves three basic steps:

  1. Identify the impacts (benefits and costs) to be included in the evaluation;
  2. Quantify the impacts (benefits and costs); and
  3. Assess the combined or accumulated impacts for each alternative, and compare these with other alternatives to develop a preference list (ranking, scaling and weighting) of the alternatives.

In mining, the diversity of impacts that must be considered makes integrated (combined and cumulative impacts) assessment difficult. How does one compare the 'apples' and 'oranges' in one fruit basket with the 'plums' and 'bananas' in another to decide which is the preferable. To a large extent, any comparison is subjective and depends on the flavor preference (value basis) of the analyst. It is not possible, and probably not desirable, to remove this subjectivity as each analyst seeks to have his/her value basis applied in the analysis. It is therefore an advantage if the evaluation methodology is systemized and transparent, allowing the various analysts to clearly indicate their value basis and results. If the results of analyses from two analysts are similar, despite differences in value basis, then there is likely to be consensus on the alternative selected. If results are materially different, then the root cause of the difference can be identified and discussions and/or additional studies can be focused on the material, value basis, issues to determine if a consensus resolution can be reached.

An example MAA worksheet is provided here in which a series of mine closure plans were evaluated for the Zortman mine site in north central Montana. This worksheet has been termed the MAA ledger and the text provided here will utilize this ledger in order to describe the MAA methodology. For a description of the specific alternatives assessed at Zortman, the reader is referred to the Bureau of Land Management website.

MAA Ledger of Accounts
The Ledger of Accounts is the template within which all the participants can register, or 'voice' their issues. The authors have found that structuring the 'ledger' into four broad categories, or 'accounts', under the headings of technical, project economics, environmental and socio-economics, works well for the evaluation of mining-related projects. All the various stakeholder's issues (termed 'sub-accounts') can be grouped within these main 'accounts'.

The term 'sub-account' has been defined here as any material impact or issue (benefit or loss) associated with any of the alternatives being evaluated. Examples of issues or impacts are 'dust, noise, contamination of surface water, employment opportunities' etc. Within each sub-account, indicator values of that particular issue are then defined in order to give a clear, understandable description of the impacts. An 'indicator value' is a measure or descriptor that provides the reader with some concept or 'picture' of the degree of impact, allowing the reader to measure or compare impacts between alternatives. Note that some sub-accounts have more than one indicator while others have just one.

Some indicators are straightforward and quantitative (e.g. costs can be expressed in dollars), however many indicators, particularly environmental and socio-economic indicators, are difficult to accurately describe or quantify without an enormous amount of investigation and analysis. For example, within the environmental account, the sub-account 'surface water quality protection' was identified in the example provided. The predictive values for long term water quality 'protection' are difficult to quantify since it varies in concentrations over both time and location. Therefore the indicator and measure of the surface water protection value is often, by necessity qualitative or semi-quantitative. The authors have found a classification system of 5 categories is often ideal for this type of qualitative assessment. In this example, values of 'high', 'somewhat high', 'intermediate', 'somewhat low' or 'low' were used to describe surface water quality protection. Each classification is associated with a general description of how water quality will be effected over time and at various locations about the mine site. Those closure alternatives that included measures such as installation of higher quality (infiltration barrier) covers over acid generating material, and effective seepage capture systems were given higher qualitative values than closure alternatives with less rigorous covers or capture systems based on the assessed effectiveness of the installed measures.

As a result of issues, such as long term water quality and/or stability of structures, which are difficult to quantify and predict, much of the assessment in this type of evaluation is necessarily based on judgement rather than deterministic analysis. This 'judgement' is often based on tools such as modeling and predictive analyses as well as on the experience of experts in the specific topic. The anticipation of behavior and assessment of performance of engineered structures, natural processes at work and environmental impacts require a sound understanding of the current technologies as well as considerable experience on a wide variety of similar projects in order to recognize and identify potential impacts, issues and risks. Therefore, having participants who are experienced with similar projects and/or dedicated to understanding and learning the realistic benefits and limitations of certain measures (e.g. cover performance) is critical to the success of these evaluations.

One of the real benefits of developing the 'Ledger of Accounts' comes from the information transfer and understanding gained during the task of filling out the ledger. It is during this stage that the determination of alternatives that may be obviously fatally flawed (i.e. do not meet threshold values such as water quality standards or cost limitations) can be identified and the alternatives either dropped from the evaluation or modified so as to preclude detailed analyses of alternatives with fatal flaws.

Once the ledger is complete, the numerical evaluation can take place. This involves the ranking, scaling and weighting of indicator values in each of the sub-accounts. The numerical evaluation includes a normalization process that allows the evaluators to compare the indicators equally, amongst themselves and between different sub-accounts.

Ranking, Scaling and Weighting
The numerical evaluation of the Zortman MAA is provided to show the Ranking, Scaling and Weighting assessment of the ledger discussed above.

Each of the alternatives being assessed is first ranked in order from best to worst with respect to each indicator being evaluated. Ranking is a simple ordered list and makes no attempt to distinguish how great the difference in impact is between alternatives on the list. In practice, there may be very little, or very large, differences in the impact from the best to the worst alternative.

Since the separation of the best alternative from the worst may be either very small or very large, a scaled value is then assigned to each alternative for each indicator. The authors have found that a 9-point scale is readily understandable and typically provides the range and discretion well suited to this type of evaluation. The best alternative for any indicator is always given a scalar value of '9'. If the second best alternative is only half as good as the best alternative, it would be given a value of '5' and so on. As an example, on the numerical evaluation worksheet for the Zortman mine, the line item assessing the stability of the North Alabama Open Pit gives scalar values ranging from '9' for Alternatives Z4 and Z5, a value of '5' for Alternatives Z1 through Z3 and a value of '7' for Alternative Z6.

To enable each evaluator or stakeholder the opportunity to introduce their value bias between individual indicators, a weighting factor is applied to each indicator (as well as to each sub-account and account). On the example worksheet, the indicator weights are shown in orange, the sub-account weights are in green and the account weights are in blue text. The process of assigning weights to the various indicators on the ledger often serves to inform all parties involved in the evaluation on two levels. First, it serves to clearly identify those issues that are most critical to each of the stakeholders. For instance, while aesthetics might be of utmost importance to one stakeholder, capital cost might be most important to another. The second level of understanding achieved in this process is that each evaluator is provided the opportunity to defend his/her weightings and more often than not, a compromise between extremes is reached as part of the assessment process. An overall understanding is achieved by all participants as the complexities of the mine sites are evaluated issue by issue and the issues assessed relative to each other.

The cumulative 'score' of one altnerative compared to another, in any one sub-account, is obtained by adding together the products of the scalar values and weights for each indicator within that sub-account category and is normalized by dividing by the sum of the weights for all the indicators in that sub-account (equation 1 below). The higher the score, the more favorable that alternative is in any one category.

Sub-Account Score = sum of Scalar Values x Weights (for each indicator in the sub-account)
sum of Weights for indicators in the sub-account.

The process of adding together the sub-account scores to obtain the account scores for the four main accounts and the overall MAA score follow the same procedure of weighting and normalization.

Results
For the example provided, the relative scores for the alternatives evaluated can be assessed on an account by account basis or by total MAA score. In summary, the scores were as follows:

Alternative Z1
Alternative Z2
Alternative Z3
Alternative Z4
Alternative Z5
Alternative Z6
Technical Account
7.5
6.7
6.5
8.1
8.8
7.1
Project Economics
5.7
8.7
7.9
4.9
4.2
6.7
Environmental
8.1
6.5
6.9
7.9
8.0
8.1
Socio-economics
6.0
6.1
6.1
7.0
7.5
6.8
     
     
     
     
     
     
MAA Score
6.9
6.9
6.8
7.1
7.3
7.3

While the individual account scores show some significant differentiation between alternatives, the overall MAA scores are fairly similar. While this is not always the case, it is often that at least two of the alternatives result in relatively similar scores. In order to differentiate the scores from one another somewhat, a discrimination value filter can be applied. This value is shown in the 'grey' columns on the numerical evaluation worksheet. In this example, the discrimination value has been set to 20% so that for any one issue or indicator, if the difference between the 'best' and 'worst' alternative's scalar value x the weight for that indicator is less than 20% of the maximum difference, then the issue is deemed 'non-discriminating' or ND and can be 'zero-ed' from the numerical evaluation (i.e. applied a weighting of '0'). As can be seen on the worksheet, a number of indicators can be flagged as non-discriminating, in particular within the technical account in which engineering standards are typically applied to all alternatives and therefore the differences are often limited.

This 'filtering' was applied to the Zortman example, with the following results:

Alternative Z1
Alternative Z2
Alternative Z3
Alternative Z4
Alternative Z5
Alternative Z6
Technical Account
7.3
6.5
6.2
8.1
8.8
6.8
Project Economics
5.7
8.7
7.9
4.8
4.3
6.7
Environmental
7.9
6.1
6.6
7.6
7.6
8.1
Socio-economics
6.0
6.1
6.1
7.0
7.5
7.0
     
     
     
     
     
     
MAA Score
6.8
6.7
6.6
7.0
7.2
7.2

Again, the results show that Alternatives Z5 and Z6 score higher than the other alternatives. Both of the sets of scores shown above are those numerical results when costs are not considered a limitation. However, as is often the case, the costs between alternatives is large and generally the more money that is spent, the better the alternative is likely to be. A cost-benefit type evaluation can be completed using the MAA to determine if additional expenditures provide commensurate improvements. The MAA score (excluding costs) can then be plotted against the cost of the alternative resulting in a cost-benefit graphic. Figure 4 below is such a plot for the Zortman example.

It becomes clear that while alternatives Z5 and Z6 scored very similarly in the complete MAA scores, the cost difference is substantial. In this type of a graphic, it is often seen that a significant benefit, or increase in MAA score can be achieved with any of the reclamation and closure alternatives. Occasionally, a more costly alternative results in a less desirable result (such as Z1 in the example). The red dot in the upper left of the plot was included to show where the ideal alternative would plot, i.e. that which resulted in a perfect MAA score for the cost of the available bond money. Alternative Z6 plots closest to this 'ideal alternative' and would be a logical selection for the prefered alternative. The options with higher scores (Z4 and Z5) are only marginally better and involve reclamation/closure costs which are several times higher. For more details about the reclamation at the Zortman mine, the reader is referred to the the Bureau of Land Management website.

Figure 4. MAA score versus total cost for the Zortman reclamation alternatives.

Utilization of the MAA
The MAA process described briefly here, has been utilized for a number of purposes in practical applications, including:

  • identification of information gaps and data needs from which studies can be developed;
  • provides a framework in which all stakeholders can identify and discuss the issues of importance to them;
  • provides an objective and simplified basis on which sensitive issues can be discussed;
  • provides a defensible and transparent tool with which decision makers can evaluate the positive and negative impacts of available alternatives; and,
  • can provide a framework for describing alternatives considered, evalauation basis and conclusions for inclusion in other documents (e.g. EIS, EA, permit applications etc).

The perspective view of the MAA process completed at the Zortman and Landusky mines, from other stakeholders, in the form of the project manager, regulatory agency and technical advisor to an adjacent Indian Tribe, is provided in the paper by Shaw et al., 2001. An overview paper for using the MAA with regards to sustainability optimization is also available (Robertson and Shaw, 2004) The reader may also complete his/her own MAA using the MAA management tool provided on EduMine.

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