Environmental Engineering FOURTH EDITION

Assessing Environmental Impact 19

Surface water^35

Ocean water

Underground water

are placed in the blocks with the magnitude above and importance below. Appropriate

blocks are filled in, using a great deal of judgement and personal bias, and then are

summed over a line, thus giving a numerical grade for either the proposed action or

environmental characteristics.

8

25 7

3 3

3 3

~ ~~~~~ ~

EXAMPLE 2.2. Lignite (brown) coal is to be surface-mined in the Appalachian

Mountains. Construct an interaction matrix for the water resources (environmental

characteristics) vs resource extraction (proposed actions).

39

Total 2

'Igble 2-2.

12

10 12

Proposed action

I Quantitv I I I IIII I I

I Temperature I 1x1 I I I I IA

Recharge

Snow, ice

In Table 2-2, we see that the proposed action would have a significant effect on sur-

face water quality, and that the surface excavation phase will have a large impact. The

value of the technique is seen when the matrix is applied to alternative solutions. The

individual elements in the matrix, as well as row and column totals, can be compared.

Example 2.2 is trivial, and cannot fully illustrate the advantage of the interaction
technique. With large projects having many phases and diverse impacts, it is relatively
easy to pick out especially damaging aspects of the project, as well as the environmental
characteristics that will be most severely affected.
The search for a comprehensive, systematic, interdisciplinary, and quantitative
method for evaluating environmental impact has led to the checkht-with-weighted-
rankings technique. The intent here is to use a checklist as before to ensure that all
aspects of the environment are covered, as well as to give these items a numerical
rating in common units.