Environmental Impact Assessment (EIA)

When is an Environmental Impact Study legally required

Under Spanish and EU environmental regulation, projects are assessed through one of two routes:

Ordinary environmental assessment — applies to large-scale projects (major infrastructure, energy installations above certain thresholds, heavy industry, open-pit mining, among others). These projects always require a complete Environmental Impact Study (EsIA) and conclude with a formal Environmental Impact Statement (DIA in Spanish).

Simplified environmental assessment — applies to smaller-scale projects and to larger projects that partially affect Natura 2000 network sites. Under this route, the developer submits an environmental document; after consultations, the environmental authority decides whether the project must go through ordinary assessment or whether a simpler environmental impact report is sufficient.

In practice, many projects that enter through the simplified route end up being redirected to ordinary assessment, which forces a complete EsIA to be drafted from scratch. Correctly identifying the applicable route from the outset is one of the areas where a specialised consultancy avoids wasted time and duplicated work.

Minimum content of an Environmental Impact Study

An EsIA compliant with Spanish and EU regulation must include, as a minimum:

• Description of the project and its actions, including construction, operation, decommissioning and, where applicable, restoration phases.
• Examination of technically viable alternatives, including the zero alternative (no action), with justification for the option adopted.
• Environmental baseline inventory of the surroundings: physical, biotic, perceptual, socioeconomic environment and cultural heritage, identifying sensitive elements.
• Identification and assessment of impacts on each environmental factor, during construction and operation, distinguishing direct, indirect, cumulative and synergistic impacts.
• Preventive, corrective and compensatory measures specific to the project, not generic boilerplate.
• Environmental Monitoring Programme with measurable indicators, sampling frequencies, alert thresholds and reporting protocol.
• Non-technical summary understandable to the general public.

Where a project may affect a Natura 2000 network site, the EsIA must also include an appropriate assessment of the effects on the site, as required under EU habitats regulation.

How the EsIA fits into the procedure

The EsIA is a document drafted by the developer, not the decision that approves or rejects the project. The simplified sequence is as follows:

1. Optional scoping request — the developer asks the environmental authority to define what the EsIA must contain.
2. Drafting of the EsIA — the stage where the consultancy is involved.
3. Public information period — a minimum statutory period during which any person may submit comments.
4. Consultation with affected authorities and interested parties.
5. Technical review of the file by the environmental authority.
6. Environmental Impact Statement (DIA) — the administrative decision published in the corresponding official gazette.
7. Project authorisation by the substantive authority, conditioned by the DIA.

The DIA typically remains valid for several years from publication for the project to begin execution, unless a justified extension is granted.

Realistic procedure timelines

Statutory deadlines and real-world timelines rarely coincide. Spanish regulation sets a reference period of a few months for the environmental authority to issue the DIA under ordinary assessment, extendable for justified reasons. In practice, the timelines we observe tend to fall within these ranges:

• Ordinary assessment: between 10 and 20 months from the start of the procedure to publication of the DIA, depending on the region, sector and quality of the submitted file.
• Simplified assessment: between 4 and 9 months to the environmental impact report.

The factors that most often extend these timelines are requests to correct deficiencies due to an insufficient EsIA, well-founded objections submitted during the public information period, and the need for additional reports from river basin authorities, cultural heritage bodies or biodiversity authorities.

Common mistakes that delay or derail an EsIA

Based on our experience processing files across Spain, the recurring reasons why an environmental authority requests corrections — or issues an unfavourable DIA — are:

• Insufficient examination of alternatives: the zero alternative is mentioned without justification, and the technical alternatives presented are cosmetic variants of the option already adopted.
• Environmental baseline inventory without a complete annual cycle for fauna, especially birds and bats in wind and solar projects.
• Non-systematic impact assessment, without a justified matrix or explicit assessment criteria.
• Generic corrective measures copied from other files, not specific to the project or its surroundings.
• Environmental Monitoring Programme without measurable indicators, alert thresholds or an action protocol.
• Missing appropriate assessment for Natura 2000 network sites when the project directly or indirectly affects a protected site.
• Omission of cumulative and synergistic impacts with other projects being processed or already built in the same area.

Anticipating these points when drafting the EsIA is what differentiates a file that is resolved on time from one that gets caught in a loop of corrections.

How we work at Ideas Medioambientales

More than 25 years drafting environmental impact studies, a multidisciplinary team (biologists, environmental scientists, archaeologists, engineers, geographers), our own fieldwork with proven methodologies, and coverage across all of Spain from our offices in Albacete and Madrid. We hold ISO 9001, ISO 14001 and ISO 45001 certifications.

We do not promise favourable outcomes — that decision rests with the environmental authority — but we do guarantee technical rigour, methodological defence of the file, and support throughout the public information and correction stages.

If you need help with the procedure, get in touch.