Okay, I have mentioned about environmental identification or inventories, let us move to the next step which is environmental assessment.
Environmental assessment is a way to quantify and calculate the projected effects that a proposed action or projects will have on environmental quality. In this point, of course we have to use a valid and solid methods to evaluate both effects of proposed projects and the effects of alternatives. These two effects may produce the same effect but different magnitude of impact. What I mean valid and solid methods here include reproducible, methodical and reasonable methods.
There are several types of methods that can be used to approach quantifying effect. We are most probably well known about check list, this is very popular because it is very simple. Another instances are interaction matrix, weighted ranking checklist. At this point we will briefly discuss checklist first.
Checklist is just a bunch of lists. What really matters are the lists fill up the methods. Checklist gathers information about potential environmental impacts. Environmental impact consists of primary and secondary impact. So this paragraph is the core of environmental assessment. The problem is you have to pick and decide carefully which one can be included as primary and which one is secondary. Primary impact is a result of direct impact of proposed project. You build a road by burning fields, this will force animals to migrate, this direct impact. After the road is built, there will be establishment of, say, gas station, food store, and this will cause the change of land use pattern, this is called indirect impact.
The checklist technique thus lists all of the pertinent factors; then the magnitude and importance of the impacts are estimated. Estimated importance of impact may be quantified by establishing an arbitrary scale, such as:
0 = no impact
1 = minimal impact
2 = small impact
3 = moderate impact
4 = significant impact
5 = severe impact
The numbers can then be combined and a quantitative measurement of the severity of the environmental impact for any given alternative. Specific characteristic of checklist is that variables are subjectively valued. In some extend this offer several drawbacks, especially when you are dealing with a high controversy project. Environmental assessment team may get interfered by a group that has monetary background over the project. However, in some cases, because of its simplicity, checklist has become a queen as it still often be used by engineers. Thus, it is one of our job to carefully choose the method we use to assess the environmental impact.