I will give a very simple application of check list approach to identify the impact and gather all relevant information and value them in terms of importance and magnitude of the impacts. Suppose you are government official in your environmental agency in your city. You receive a proposed project to build a huge shopping mall in a certain area located in the center of the city, thus in a very crowded area. Identify and value the importance and magnitude of the impacts that may arise.
First thing what you have to do is listing the items that may have impact, then make a quantitative judgement concerning importance and magnitude of the impact. Now let us try to make some items.
Set up the quantitative value for importance and magnitude (scale 0 to 5 for 0 is the lightest impact and 5 the biggest impact), then multiply the value of both.
Groundwater contamination: 4 and 5 = 20
Surface contamination: 3 and 4 = 12
Air Pollution: 4 and 5 = 20
Noise: 1 and 2 = 2
Odor: 1 and 1 = 1
Traffic jam: 3 and 2 = 6
Jobs available: -2 and 3 = -6
This total of 50 can then be compared with totals of another alternative ways of actions. The jobs are positive impact because the proposed project may cause the direct and indirect recruitment. Direct recruitment such as recruiting workers, indirect employment means in the surrounding area of proposed project, there may be a new small store built to supply worker’s need, thus this will provide new employment.
To determine a FONSI, a value that indicates the lower limit of significance can be assigned to importance or magnitude. For example, if the absolute value of the items of importance and magnitude of any variable is considered significant only if that product is 10% of the total, noise and odor would not be deemed significant and need not be considered for further assessment. Alternatively, if the absolute value of importance and magnitude of a product considered significant above 5, then the same conclusion is attained.