The methodology offered in this article is based on the Environmental and Socioeconomic Impact Assessment Model. In this case, it is a qualitative assessment based on several criteria used to create an indicator of the significance of the impact. While these instructions contain a set of mandatory minimum criteria, there is no limitation on using another assessment methodology as a complement, provided there is a technical justification for expanding the methodological framework to improve the impact identification and assessment procedure.
The methodology outlined below involves a process whose first step is the identification of the project activities considered impactful. The second step is the identification of the environmental and socioeconomic factors expected to be affected by the project activities. Finally, the third step is the measurement of the impacts identified on the identified factors. The project’s environmental assessment is a study that applies a methodology to identify the most significant environmental and socioeconomic impacts. The impact assessment should analyze the effect on the project area, both in its direct and indirect areas of influence, considering the impacts in each of the three post-investment stages of the project: a) the construction stage, b) the operation stage, and c) the closure and decommissioning stages. The project’s environmental assessment must identify the project elements that generate impacts, as well as the environmental and socioeconomic factors likely to be impacted. These factors are related to:
- Air,
- Soil,
- Surface water,
- Groundwater,
- Aquatic and terrestrial biotopes,
- Natural hazards,
- Sociological and cultural aspects,
- Landscape,
- Solid waste management,
- Liquid waste,
- Hazardous substances,
- Relations with nearby communities, and
Occupational health and hygiene factors.
For each of the activities identified as impactful, the Environmental Impact Significance Matrix (EIMM) is used. This method allows for the association of environmental and socioeconomic factors considered to be impacted. This matrix identifies negative impacts with a negative sign (-) and positive impacts with a positive sign (+). In some cases, a third character (*) indicates that a more in-depth study will determine whether the effect is positive or negative.
In an Impact Importance Matrix. Impacts are first classified by type of environment, distinguishing between physical, biological, waste, and socioeconomic environments. Each environment is broken down into components and factors.
Once the impacting activities have been identified, and the affected environmental and socioeconomic factors are identified using the Impact Importance Matrix, the impact is measured using an impact importance index. According to this methodology, “the impact is measured based on the degree of qualitative manifestation of the effect, which is reflected in what we define as impact importance” (Executive Decree 32966 – Annex 1).
The importance of the impact (I) arises from the qualitative measurement of the environmental or socioeconomic impact based on:
Degree of incidence (DI): Intensity of the alteration produced
Furthermore, based on the characterization of the effect, which is reflected in attributes such as:
- Extent (EX): Area of influence
- Time of manifestation (MO): Period of manifestation
- Persistence (PE): Permanence of the effect
- Reversibility (RV): Possibility of reversing the effect
- Synergy (SI): Potentiation of the manifestation
- Accumulation (AC): Progressive increase
- Type of effect (EF): Cause-effect relationship (indirect or direct)
- Periodicity (PR): Regularity of the manifestation
- Recoverability with compensatory measures (MC): Reconstruction by human means
Each of the attributes has a rating scale, according to the level of influence on the impact. As indicated above, the sign indicates that the impact is beneficial (+), harmful (-), or a third character (*) indicates that further studies are required to determine whether the impact is positive or negative.
- Intensity (IN) is the degree of impact and has a rating scale between 1 and 12, with 12 indicating total destruction of the environmental factor assessed and 1 indicating minimal impact.
- The extent (EX) is the area of influence of the impact. If the effect is very localized, the score is 1, but if the effect has a generalized influence, the score is 8. When the impact is partial, the score is 2, or if it is extensive, the score is 4. When the effect is in a critical location, an additional score of 4 is added to the original score. However, if in addition to being critical, it is a dangerous effect, with no possible corrective measures, no score is given but rather implies abandoning the alternative location.
- The time (MO) is the time that elapses between the appearance of the action and the beginning of the effect. If the time is immediate or less than one year (short term), the score is 4. If the time is between 1 and 5 years (medium term), the score is 2, and the effect is greater than 5 years (long term), the score is 1. Again, if any circumstance makes the moment of impact critical, 4 units are added to the score. Persistence (PE) is the length of time the effect would persist from its onset, that is, it is the difficulty for the environmental factor to return to its initial conditions. Persistence can be permanent, in which case it would be given a score of 4, or it can be temporary, in which case the score is 2. If the effects are fleeting and temporary, the score is 1.
- Reversibility (RV) is the possibility of reconstructing the affected factor, returning to the initial conditions prior to the action by natural means. If reversibility can occur in less than a year, it is scored as 1; if it occurs between 1 and 5 years, the score is 2; and if the effect lasts more than 5 years or is irreversible, it is scored as 4.
- Synergy (SI) is the simultaneous effect of two or more independent effects, which reinforce each other. When an action does not exhibit synergy, the score is 1; if it exhibits moderate synergy, the score is 2; and if it is highly synergistic, the score is 4. Synergy can be rather negative, reducing the significance of the impact.
- Accumulation (AC) is the progressive increase in the manifestation of the effect. When an action does not produce cumulative effects, the score is 1. If the effect is cumulative, the score is 4.
- Effect (EF) reflects the cause-effect relationship, which can be direct or indirect. If the effect is direct, the score is 4, while if the effect is indirect, the score is 1.
- Periodicity (PR) is the regularity with which the effect will manifest itself, which can be cyclical or recurrent, meaning that it is a periodic effect, for which a score of 2 is given; if the effects are continuous, the score is 4, and when they are discontinuous, the score is 1.
- Recoverability (MC) is the possibility of reconstructing, totally or partially, the affected factor with corrective measures. If the effect is immediately recoverable, a score of 1 is assigned, but if immediate recovery is only partial, the score is 2. When recovery takes between 1 and 5 years and is partial but mitigable, the score is 4. If the effect is unrecoverable, the score is 8, unless compensatory measures are necessary, so the final score can be 4.
The significance of the impact (I) is ultimately an index formed from the scores of the factors indicated above, with greater weights for intensity and extent.
I = ± [3*IN + 2*EX + MO + PE + PV + SI + AC + EF + PR + MC]
The significance of the impact can take final values between 13 and 100. The importance criteria applied are:
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- Impacts with significance values below 25 are irrelevant.
- Moderate impacts have significance between 25 and 50 points.
- Severe impacts range from 50 to 75 points.
- Critical effects have values above 75.
When the effect is in a critical location, an additional score of 4 is added to the original score.
However, if in addition to being critical, it is a dangerous effect, with no possible corrective measures, no score is given but rather implies abandoning the alternative location.
The criteria for determining the final significance of the environmental and socioeconomic impacts are:
- Effects with insignificant values will not be taken into account when considering corrective measures and the subsequent economic evaluation.
- Moderate effects are considered normal for the project. Many of them may not be persistent and do not require corrective measures, but analysis must be applied to determine whether some ultimately require mitigating measures.
- Severe effects are intended to be attenuated or minimized by incorporating corrective measures, but their predominant role in decision-making should not be obscured.
- Critical effects reveal the need to refrain from carrying out the impacting activity, which may mean changing the location or characteristics of the project to avoid these effects. Compensation for these effects may also be permitted, if the environmental authority so authorizes.
The analysis must incorporate an assessment of these environmental and socioeconomic factors, both in the situation without the project and in the situation with the project, since the effect specifically attributable to the project, i.e., the incremental impact, must be isolated.