Environmental Engineering Reference
In-Depth Information
each specific functional area of interest. Step two
is to propose criteria clusters. The last step is to
define specific objectives and assign them to one
or more impact category. This structure allows
end-users to select modules that best match the
specific components of their master plan project.
An example table of criteria clusters and ob-
jectives is shown in Table 4. Users may develop
their own table by defining a group for each key
functional area and developing criteria clusters
within them. Criteria clusters that matter most
will likely be emphasized in planning documents
and environmental impact assessments. Ideally,
such parameters should be defined in conjunc-
tions with project stakeholders to ensure mutual
understanding from the preliminary phases of
the evaluation.
In this example, “Group B: Airfield” is pro-
posed for the analysis of environmental impacts
specific to the airfield functional area of the proj-
ect. Within this group, criteria clusters for runways
and taxiways, GSE, noise and de-icing are defined.
Within each cluster, individual goals are defined,
such as reducing ground vehicles emissions, and
attributed to the relevant impact categories; in
this case, global warming and air quality. The
same procedure is then applied throughout the
project of interest and leads to the construction
of a table of criteria clusters and objectives.
ability of the design. End-users should ensure that
important aspects of the master plan are reflected
in the selection while also limiting parameters to a
minimum in order to ensure simplicity (Table 5).
Each indicator provides evaluation data in the
form of a decision criterion. Let
C
= {
C
j
, for j =
1,2,…,m} be this finite set of criteria. We distin-
guish two types of values: qualitative and quantita-
tive criteria. A criterion is considered qualitative
when it describes an observation expressed on a
quality scale: ranging from low to high, or bad
to good, for example. A criterion is considered
quantitative when it describes a quantity on a
numeric scale. Qualitative criteria are inherently
subjective and accurate evaluations necessarily
rely on the inclusion of quantitative measures. It
is important, therefore, to use quantitative criteria
wherever possible. These have the advantage of
being expressed in a particular unit that can then
be converted into an absolute or relative value.
Two types of scoring apply to these indicators:
for a quality index, a higher score indicates better
quality for the environment, whereas for a pollu-
tion index, a lower score is the better.
Wherever possible, several levels of indicators
with varying levels of data requirements should
be used. In our example, level 1 indicators are
generally qualitative and intended to depict rank
potential for quality improvement or pollution
reduction between alternatives—these are particu-
larly relevant when a low level of complexity is
required—whereas level 2 and 3 indicators tend
toward quantitative performance-based measures.
Quantitative measures help differentiate alterna-
tives with similar opportunities for a specific objec-
tive as they provide additional scoring information.
To illustrate the nature of performance indicators
utilized by our method, we present a set of tentative
performance indicators addressing the “Airfield”
functional area and its clusters of criteria. The role
of indicators is to report on a specific issue while
the decision criterion uses this same information
for decision making purposes. A sample scoring
Definition of Performance
Indicators and Decision Criteria
The next step is to evaluate the performance of each
alternative toward the selected objectives. The
proposed method utilizes performance indicators
as a means for collecting data. For each objective,
end-users select one or more indicators to report
on the performance of a proposal in a particular
field. The characteristics of these indicators con-
tribute highly to the accuracy and reliability of the
evaluation process. The range of indicators must
be selected so that it is useful, manageable and
effective at indicating the environmental sustain-
