Environmental impact statement and Environmental assessment

The general principle of environmental impact assessment has been explained in previous post. Three outcomes resulted from judging the proposed project are FONSI, EA and EIA. EA and EIS document generally consist on three parts, introduction, description of proposed project and alternatives and description of the environment affected by the proposed actions.

The introduction part of the document will state overview of the project, the purpose, alternative actions, summary of important environmental aspects and the methods of assessment being used. The description of proposed actions and alternative will describe the actions, lists of stage conducted for the project. In this part, alternatives are also mentioned, including a “no-action” alternatives as well. Statement also include the projected actions if the project is not done.

The core of the EIS document is actually located on this part. The name of this part is description of the environment affected by the proposed action or project. Suppose there is one proposed action with another alternatives, each of these actions will contain the lists of environment will likely to get affected by particular action and alternatives. The measurement of the effect is defined by EIU, Environmental Impact Unit. The formula of EIU is as follows:


PIU = Parameter Impact Unit
EQI = Environmental Quality Index

The description of the environment affected by the proposed project contains lists of environmental parameters such as ecology, aesthetics and environmental pollution and human health. This list is grouped according their characteristics. For example, ecology may comprise of species or microorganisms live in the location of the proposed project, ecosystems etc. Several examples are shown below.

– Species and populations
– habitat
– wetlands and

– land
– air
– biota (biology)
– water
– object of historical or cultural significance

Environmental pollution and human health
– water
– air
– land
– noise

– jobs created or lost
– property values

If you heed on lists above, they are still in general. Therefore, we usually have to make more detail lists or specific subtopics. For example in environmental pollution and human health, there is water item, we identify the quality of water such as BOD (Biological Oxygen Demands) or DO (Dissolved Oxygen). If we focus on air, it may have specific subtopics such as sound or odor.

Each of these items will be assigned a numerical rating to each of them, which is called EIU. You already know the formula to obtain EIU, we have to obtain PIU and EQI. Environmental Quality Index (EQI) is a ratio between the present value and the predicted value after the project. For example DO in surface water where the project is located and may interrupt the quality of the surface water, at present after laboratory test DO is, say 8 mg/L, the predicted DO after the project is 2 mg/L, thus the ration is 2/8, equals 0.25. Each listings has to be assigned this EQI. If you are dealing with quantitative items such as odor or aquatic life, you may assigned the scale from 0 to 1. To assign the EQI for items that have natural qualitative characteristics you may want to convert them into quantitative one. For example, cost spent for population around project location with current odor or sound qualitative condition and with the predicted condition. The EQI will then be tabulated for each items.

Next step is to assign weights for each item, usually by distributing 1000 PIU. The distribution of PIU is usually chosen by the decision maker. The number of 1000 PIU is subjective depends on the committe of decision maker, this it is possible as well to assign 10 or 100 PIU.

I want to make a very simple example, suppose the proposes project is to build shopping malls on an empty spot in the center of city near the river. Next step is to list the areas of environmental impact. They are:

– water appearance
– DO
– odor
– turbidity
– suspended solid
– aquatic life

We have to determine the condition before project and prediction after project and then calculate the ratio. The list below follows the order: items, condition before project (unitless;mg/L), condition after project, EQI.

– Water appearance, 10, 4, 0.4
– DO, 8 mg/L, 2 mg/L, 0.25
– odor, 10, 5, 0.5
– turbidity, 15 NTU, 30 NTU, 0.5 (as higher NTU means more turbidity, thus the ratio is 15/30)
– suspended solid, 20 mg/L, 2000 mg/L, 0.01
– aquatic life 10, 4, 0.4

The qualitative items such water appearance, odor and aquatic life are assigned value from 10 to 1 in which lower value means degradation of environment. The EQI is weighted by 10 PIU in this example and the EIU is calculated. We assign PIU for each item as follows:

– water appearance, 1 PIU
– DO, 2 PIU
– odor, 1 PIU
– turbidity, 2 PIU
– suspended solid, 2 PIU
– aquatic life, 2 PIU

Total is 10 PIU.

Now we calculate the EIU based on the following order: item, PIU, EQI, EIU.

– water appearance, 1 PIU, 0.4 EQI, 0.4 EIU
– DO, 2 PIU, 0.25 EQI, 0.5 EIU
– odor, 1 PIU, 0.5 EQI, 0.5 EIU
– turbidity, 2 PIU, 0.5 EQI, 1 EIU
– suspended solid, 2 PIU, 0.01 EQI, 0.02 EIU
– aquatic life, 2 PIU, 0.4 EQI, 0.8 EIU

Total EIU is (0.4 + 0.5 + 0.5 + 1 + 0.02 + 0.8) 3.22 EIU. So we have obtained total EIU of a proposed action, now analogue with this method, we calculate the total EIU for other alternatives. Total EIU for each action is then compared to each other. Better action is indicated by higher EIU.

2 thoughts on “Environmental impact statement and Environmental assessment

Leave a Comment