Starting up; early stages - Introduction to Environmental Impact Assessment - page 114

examining the number of times that an alternative exceeds the threshold of concern. For
example, Figure 4.8 shows part of a checklist developed by the US Forest Service; it
compares three alternative development proposals on the basis of various components.
For the component of economic efficiency, a benefit:cost ratio of 1:1 is the threshold of
concern; for spotted owls, 35 pairs is the threshold. In the example, alternative X causes
two thresholds of concern to be exceeded, alternative Y one, alternative Z four; this
would indicate that alternative Y is the least detrimental. Impacts are also rated according
to their duration: A for 1 year or less, B for 1-10 years, C for 10-50 years and D for
irrev e rsible
No. Questions to be considered in
Scoping

Yes/No/? Which Characteristics

of the Project
Environment could be
affected and how?

Is the effect
likely to be
significant?
Why?

7 Will the project lead to risks of

contamination of land or water
from releases of pollutants onto the
ground or into sewers, surface
waters, ground water, coastal
waters or the sea?

7.1 From handling, storage, use or

spillage of hazardous or toxic
materials?

7.2 From discharge of sewage or other

effluents (whether treated or
untreated) to water or the land?

7.3 By deposition of pollutants emitted

to air, onto the land or into water?

7.4 From any other sources?

7.5 Is there a risk of long-term build-

up of pollutants in the environment
from these sources?

Figure 4.7 Part of a questionnaire
checklist. ( Source: EC 2001b.)

impacts. Of the impacts listed, a reduction in the number of spotted owls would be
irreversible, and the other impacts would last 10-50 years (Sassaman 1981).

Matrices
Matrices are the most commonly used method of impact identification in EIA. Simple
matrices are merely two-dimensional charts showing environmental components on one
axis and development actions on the other. They are, essentially, expansions of checklists
that acknowledge the fact that various components of a development