5.4.1.2
Descriptive Checklists
Descriptive checklists comprise lists of environmental factors along with necessary information on measurement and predictive techniques. Adequate guidance is provided for assessment of the impacts identified by the listing. This methodology attempts to ensure adequacy of data collection by including the constituent elements of each of the potential impacts identified. Descriptive checklists are very popular amongst EIA consultants.
Descriptive checklists may be good impact identification tools. Depending on the nature of the project and the environmental setting resource requirement may be moderate to high. Impact summarisation is poor and therefore selection of preferred alternative is difficult. Because of its in-built impact identification criteria, mitigation measures can be assessed effectively
Early attempts to develop descriptive checklists include development of an environmental impact computer system (EICs) by the US. Army Construction Engineering Research Laboratory (Lee et al. 1974, Jain et al. 1973). Under this methodology the following nine functional areas of army activities are identified; construction, research and development, real estate acquisition or outleases of land, mission change, procurement, training administration and support, industrial activities and operation and maintenance. These army activities are related to attributes contained in eleven technical areas of speciality describing the environment. Each of the nine functional areas and the eleven types of attributes are further subdivided into base activities and environmental parameters respectively. About 2000 activities and 1000 parameters are identified.
Potential impacts are identified by computer assessment of various activities and attributes. Instead of a numerical scale an alphabetical rating, using A, B and C as indicators, is used to identify the level of details at which the impacts are to be assessed. Although Jain et al. (1977) called it a matrix methodology, the author considers the methodology to be a descriptive checklist because activity-attribute interactions are not properly assessed. Also this methodology describes the environmental factors under consideration in detail along with information on actual measurement and interpretation.
The significant features of this methodology are (Jain et al. 1977, 1993):
1. It is cost-effective;
2. It provides analytical models for cause effect relationships;
3. It is a comprehensive methodology;
4. The output matrix is modified based upon site specific inputs to produce a project specific input matrix;
5. It provides information regarding environmental laws and regulations; and,
6. It includes information about abatement and mitigation techniques.
This methodology has been designed for army military programs. Significant modifications of this methodology are needed before it can be applied to other situations.
Several other descriptive checklist methodologies are available. For example Canter and Hill (1979) developed a descriptive checklist for water impoundment projects. The methodology considers 65 environmental factors related to the environmental quality account used for project evaluation in the United States. The environment has been categorised as terrestrial; aquatic; air, and human interface. Each category is divided into an appropriate number of subcategories. For example aquatic environment has been subcategorised as population, habitat, water quality and water quantity. For each of the environmental factors guideline on measurement and impact prediction are provided. The factors are defined and wherever appropriate functional curves for data interpretation are given. Other examples of descriptive checklists include an approach developed by Carstea et al. (1976) for assessment of projects in coastal areas and a descriptive checklist used for transportation project (USDOT 1975).
Above discussions on non-quantitative checklists drive home the point that such methodologies can be more useful if checklists are developed keeping in mind the specific characteristics of the project under consideration. Past attempts to develop all encompassing checklists in order to enhance applicability have been found to be counterproductive.
5.4.2 Quantitative Checklists
Over the years quantitative checklists have received wide acceptability mainly because of their ability to summarise environmental impacts in terms of a single numerical value thus facilitating ranking of alternatives. However, in many cases the subjective assessments are given arbitrary numeric values to enable quantification.
5.4.2.1 Scaling Checklists
One of the first attempts to present a quantitative checklist was made by Adkins and Burke (1974). This methodology involves 'scaling' of impacts on an eleven point scale ranging from minus five to plus five. According to Canter (1996) 'scaling' refers to the assignment of algebric scales or letter scales to the impact of each alternative being evaluated on each identified environmental factor; functional relationships typically serve as the basis for these assignments.
The Adkins and Burke methodology is silent on how to measure the impacts. Scores are assigned to the alternatives in comparison to the present state of the project area, not the expected future state without project (Warner and Preston 1973). The relative impacts from alternatives can be directly compared in a table form for individual impacts or in summary form to evaluate total project impacts. In its original form Adkins-Burke scaling checklist lacked ecological considerations (Westman 1985) and was applicable only in situations dealing with the evaluation of highway route alternatives. Resource requirement for this methodology is very flexible. Because of its inherent subjectivity the Adkins-Burke scaling checklist has not been very popular.
'Environmental Assessment Procedures' developed by the United States Soil Conservation Service (USSCS) in 1974, is another 'scaling-checklist' which involves evaluation of impacts on the selected environmental factors by using a scaling system.
Since no weightage scheme is adopted all the parameters assume equal importance. Thus, if out of 'n' number of affected parameters, impact on 'm' of them be positive then the ratio of plus ratings m/n is taken as an indicator of overall impact. Algebric sum of impact ratings (IS) also indicates the overall impact.
Where IS = total impact score,
EIi= Environmental impact on ith parameter (i=1, 2, ....n) EIi may be positive or negative depending on the nature of impact.
Average impact is estimated as IS/n and is used as another index of impact due to an alternative.
Impacts are assessed for all the alternatives under consideration. There is no explicit criteria for ranking of alternatives and hence ultimate selection of alternative is left to the wisdom of decision makers.
Most checklists now employed have gone beyond this level of sophistication to include not only the magnitude but also the importance of the impact (Scheckels 1980).
Variants of scaling checklist include 'ranking' or 'rating' checklists. Ranking checklists provide explicit criteria to rank the alternatives in terms of their 'ability to satisfy the environmental factors under consideration' (Rau 1980). Ranking allows ordering of alternatives relative to each environmental factor considered. If 'n' number of environmental parameters are considered against an alternative then the most important impact likely to be caused by the alternative, would be assigned rank of n. A rank of n-1, may be assigned to the second-most-important impact and so forth. However, the greatest demerit of a ranking checklist is that it does not enable one to distinguish incremental differences among alternatives. When more than one environmental parameter is considered ranking of alternatives can be done by adding the ranks for each parameter and then by ordering the total obtained for each alternative. Ranking checklist thus assumes equal importance for each parameter considered. Moreover its failure to take into account the magnitude difference for various alternatives render it unfit as a tool for comparison of alternatives.
'Rating checklists' involve the use of a pre-defined rating scheme. Usually relative importance of each of the environmental parameters is considered. Importance rating of environmental parameters involves assignment of importance numbers to the parameters. The technique has been sophisticated by involving normalisation of importance rating using a mathematical procedure (Canter 1996). Impact on an environmental parameter, to be caused by an alternative, is rated by combining the 'impact rank' of the alternative with the 'relative importance' of the parameter. For selecting the best alternative the ratings may be added to obtain a 'total score'. The alternative with least total (adverse) impact is chosen as the most favourable. Perhaps the most important inadequancy of the rating scheme lies in its inability to recognize the incremental differences among rankings. This can be overcome by determining the magnitude of the impact in terms of a 'commensurate scale' and then combining this magnitude with the "parameter importance unit". Methodologies incorporating such techniques are termed 'weighting-scaling' methodologies.
Descriptive checklists comprise lists of environmental factors along with necessary information on measurement and predictive techniques. Adequate guidance is provided for assessment of the impacts identified by the listing. This methodology attempts to ensure adequacy of data collection by including the constituent elements of each of the potential impacts identified. Descriptive checklists are very popular amongst EIA consultants.
Descriptive checklists may be good impact identification tools. Depending on the nature of the project and the environmental setting resource requirement may be moderate to high. Impact summarisation is poor and therefore selection of preferred alternative is difficult. Because of its in-built impact identification criteria, mitigation measures can be assessed effectively
Early attempts to develop descriptive checklists include development of an environmental impact computer system (EICs) by the US. Army Construction Engineering Research Laboratory (Lee et al. 1974, Jain et al. 1973). Under this methodology the following nine functional areas of army activities are identified; construction, research and development, real estate acquisition or outleases of land, mission change, procurement, training administration and support, industrial activities and operation and maintenance. These army activities are related to attributes contained in eleven technical areas of speciality describing the environment. Each of the nine functional areas and the eleven types of attributes are further subdivided into base activities and environmental parameters respectively. About 2000 activities and 1000 parameters are identified.
Potential impacts are identified by computer assessment of various activities and attributes. Instead of a numerical scale an alphabetical rating, using A, B and C as indicators, is used to identify the level of details at which the impacts are to be assessed. Although Jain et al. (1977) called it a matrix methodology, the author considers the methodology to be a descriptive checklist because activity-attribute interactions are not properly assessed. Also this methodology describes the environmental factors under consideration in detail along with information on actual measurement and interpretation.
The significant features of this methodology are (Jain et al. 1977, 1993):
1. It is cost-effective;
2. It provides analytical models for cause effect relationships;
3. It is a comprehensive methodology;
4. The output matrix is modified based upon site specific inputs to produce a project specific input matrix;
5. It provides information regarding environmental laws and regulations; and,
6. It includes information about abatement and mitigation techniques.
This methodology has been designed for army military programs. Significant modifications of this methodology are needed before it can be applied to other situations.
Several other descriptive checklist methodologies are available. For example Canter and Hill (1979) developed a descriptive checklist for water impoundment projects. The methodology considers 65 environmental factors related to the environmental quality account used for project evaluation in the United States. The environment has been categorised as terrestrial; aquatic; air, and human interface. Each category is divided into an appropriate number of subcategories. For example aquatic environment has been subcategorised as population, habitat, water quality and water quantity. For each of the environmental factors guideline on measurement and impact prediction are provided. The factors are defined and wherever appropriate functional curves for data interpretation are given. Other examples of descriptive checklists include an approach developed by Carstea et al. (1976) for assessment of projects in coastal areas and a descriptive checklist used for transportation project (USDOT 1975).
Above discussions on non-quantitative checklists drive home the point that such methodologies can be more useful if checklists are developed keeping in mind the specific characteristics of the project under consideration. Past attempts to develop all encompassing checklists in order to enhance applicability have been found to be counterproductive.
5.4.2 Quantitative Checklists
Over the years quantitative checklists have received wide acceptability mainly because of their ability to summarise environmental impacts in terms of a single numerical value thus facilitating ranking of alternatives. However, in many cases the subjective assessments are given arbitrary numeric values to enable quantification.
5.4.2.1 Scaling Checklists
One of the first attempts to present a quantitative checklist was made by Adkins and Burke (1974). This methodology involves 'scaling' of impacts on an eleven point scale ranging from minus five to plus five. According to Canter (1996) 'scaling' refers to the assignment of algebric scales or letter scales to the impact of each alternative being evaluated on each identified environmental factor; functional relationships typically serve as the basis for these assignments.
The Adkins and Burke methodology is silent on how to measure the impacts. Scores are assigned to the alternatives in comparison to the present state of the project area, not the expected future state without project (Warner and Preston 1973). The relative impacts from alternatives can be directly compared in a table form for individual impacts or in summary form to evaluate total project impacts. In its original form Adkins-Burke scaling checklist lacked ecological considerations (Westman 1985) and was applicable only in situations dealing with the evaluation of highway route alternatives. Resource requirement for this methodology is very flexible. Because of its inherent subjectivity the Adkins-Burke scaling checklist has not been very popular.
'Environmental Assessment Procedures' developed by the United States Soil Conservation Service (USSCS) in 1974, is another 'scaling-checklist' which involves evaluation of impacts on the selected environmental factors by using a scaling system.
Since no weightage scheme is adopted all the parameters assume equal importance. Thus, if out of 'n' number of affected parameters, impact on 'm' of them be positive then the ratio of plus ratings m/n is taken as an indicator of overall impact. Algebric sum of impact ratings (IS) also indicates the overall impact.
Where IS = total impact score,
EIi= Environmental impact on ith parameter (i=1, 2, ....n) EIi may be positive or negative depending on the nature of impact.
Average impact is estimated as IS/n and is used as another index of impact due to an alternative.
Impacts are assessed for all the alternatives under consideration. There is no explicit criteria for ranking of alternatives and hence ultimate selection of alternative is left to the wisdom of decision makers.
Most checklists now employed have gone beyond this level of sophistication to include not only the magnitude but also the importance of the impact (Scheckels 1980).
Variants of scaling checklist include 'ranking' or 'rating' checklists. Ranking checklists provide explicit criteria to rank the alternatives in terms of their 'ability to satisfy the environmental factors under consideration' (Rau 1980). Ranking allows ordering of alternatives relative to each environmental factor considered. If 'n' number of environmental parameters are considered against an alternative then the most important impact likely to be caused by the alternative, would be assigned rank of n. A rank of n-1, may be assigned to the second-most-important impact and so forth. However, the greatest demerit of a ranking checklist is that it does not enable one to distinguish incremental differences among alternatives. When more than one environmental parameter is considered ranking of alternatives can be done by adding the ranks for each parameter and then by ordering the total obtained for each alternative. Ranking checklist thus assumes equal importance for each parameter considered. Moreover its failure to take into account the magnitude difference for various alternatives render it unfit as a tool for comparison of alternatives.
'Rating checklists' involve the use of a pre-defined rating scheme. Usually relative importance of each of the environmental parameters is considered. Importance rating of environmental parameters involves assignment of importance numbers to the parameters. The technique has been sophisticated by involving normalisation of importance rating using a mathematical procedure (Canter 1996). Impact on an environmental parameter, to be caused by an alternative, is rated by combining the 'impact rank' of the alternative with the 'relative importance' of the parameter. For selecting the best alternative the ratings may be added to obtain a 'total score'. The alternative with least total (adverse) impact is chosen as the most favourable. Perhaps the most important inadequancy of the rating scheme lies in its inability to recognize the incremental differences among rankings. This can be overcome by determining the magnitude of the impact in terms of a 'commensurate scale' and then combining this magnitude with the "parameter importance unit". Methodologies incorporating such techniques are termed 'weighting-scaling' methodologies.