A single door

For a mining project, obtaining the environmental approval (Resolución de Calificación Ambiental, RCA) has often been half the journey. The other half was keeping it. Third parties could challenge an RCA through administrative invalidation up to two years after it was notified or published, and an interim measure of the Environmental Court could suspend it with no maximum term. For an operation that has already committed the investment, that uncertainty weighs as much as the assessment itself.

Ley 21.850, published on October 17, 2026 and known as the mega-reform, targets precisely that stretch. Its article 11 amends Ley 19.300, its article 14 amends Ley 20.600 and its article 16 changes the regime for archaeological and paleontological finds. Since the law did not set a special date for most of those provisions, they have been in force since the first day of the month following its publication, under its ninth transitional article, that is, since November 1.

A single route to challenge the RCA

The new article 20 of Ley 19.300 concentrates challenges to the RCA in the special administrative appeal (recurso especial de reclamación). If the project was submitted through an environmental impact statement (Declaración de Impacto Ambiental, DIA), the appeal is decided by the Executive Director of the Environmental Assessment Service (Servicio de Evaluación Ambiental, SEA). If it was submitted through an environmental impact study (Estudio de Impacto Ambiental, EIA), it is decided by the Comité de Ministros (Committee of Ministers), chaired by the Minister of the Environment and also made up of the Ministers of Health, Economy, Agriculture, Energy and Mining. The law keeps that committee, but requires it to meet at least ten times a year.

The appeal may be filed by the project owner, by those who submitted observations during public participation and by any person who qualifies as an interested party under article 21 of Ley 19.880. Those who submitted observations may base their appeal only on their observations and on essential procedural defects. Other interested parties may do so only on aspects that affect them directly and on those same defects. The deadline is thirty days from notification or publication of the resolution, and the RCA is presumed to be known by everyone from the moment the SEA publishes it on its website.

The authority must decide all appeals in a single act, within a strict deadline of thirty days for a DIA and sixty days for an EIA. If it fails to do so, the appellant may ask it to decide within five days, and once that period has expired any interested party may request a certificate deeming the appeal rejected. From then on, there are twenty days to file a claim before the Environmental Court, and the judicial claim may only be based on what was raised at the administrative level.

The piece that completes the design is the new article 24 bis. Administrative appeals and the review mechanisms of Ley 19.880, including invalidation, are no longer available against the RCA "on the same matters that were heard through the special administrative appeal". In addition, article 4 of Ley 21.850 reduced from two years to one the general period for invalidating administrative acts under article 53 of Ley 19.880.

That phrase admits two readings. The reading favorable to the project owner holds that, once the appeal period has expired, the RCA is closed to any administrative review, because everything that could be discussed should have been raised through article 20. In its favor, the new numeral 8) of article 17 of Ley 20.600 expressly excludes the RCA from judicial claims against invalidation resolutions. The unfavorable reading sticks to the literal text. If the exclusion reaches only the matters actually heard in the appeal, a third party who did not appeal could attempt invalidation on other matters, now within one year. This point will probably end up in the courts, and in the meantime the project owner should not consider an RCA closed just because no one appealed it.

Six months at most

Article 24 of Ley 20.600 now limits the interim measures that totally or partially suspend an RCA. They last thirty calendar days, renewable for equal periods by reasoned resolution, and may in no case extend beyond six months from when they were granted. The resolutions that grant, deny or renew them may be appealed before the Court of Appeals within ten days, and the appeal has devolutive effect only.

The limit has an exception. The court may order a new measure when it is necessary to prevent a serious and irreversible risk to the environment or to people's health, or when there is a manifest breach of the RCA, weighing the interests at stake and the proportionality of the measure. For an operation under construction, the difference between a suspension with no term and one of six months is enormous. But the rule protects the project that complies with its RCA, because in the face of a manifest breach the court retains the power to suspend it again.

When a modification returns to the SEIA

Few activities modify their facilities as much as mining. A growing waste dump, a new mining front or a change in the plant often raise the question of whether the change requires a new environmental assessment within the environmental impact assessment system (Sistema de Evaluación de Impacto Ambiental, SEIA), usually through a relevance consultation (consulta de pertinencia).

The new final paragraph of article 10 of Ley 19.300 provides that modifications to a project with a favorable RCA, whose works are carried out in the same assessed area, will require a new assessment only if there is a substantive modification in the magnitude or extent of the impacts, and that those involving only a technological improvement will not require it. The same provision entrusts the SEIA regulation with regulating those circumstances. Until that regulation is issued, the new legal rule will coexist with the definition of project modification in the current regulation, Decreto Supremo N° 40 of 2012, which refers to significant changes (cambios de consideración). Until the SEA sets a criterion, relevance consultations will remain the prudent path.

A faster lane, at the project owner's choice

The new article 25 septies creates a special regime that the project owner may opt into by declaring so when submitting the project. Under that regime, a DIA allows a single round of clarifications, corrections or additions, and an EIA up to two, the second being exceptional and reasoned. Sectoral agencies must confine themselves to what the project owner submitted, without adding new requirements. In parallel, the new letter a) of article 81 gives the SEA technical stewardship of the assessment and instructs it to consider only relevant opinions, issued within each agency's competence and within the deadline.

The special regime rewards projects that are submitted complete, with a solid baseline. With fewer opportunities to correct, a gap that was previously cured in a second or third addendum may now end in a rejection. For a mining EIA, opting into this regime is a strategic decision best made before submission.

Archaeological and paleontological finds

In the north of the country, a paleontological find can halt an operation for months. The new article 26 of Ley 17.288 keeps the obligation to give immediate notice to the Technical Secretariat of the Consejo de Monumentos Nacionales (National Monuments Council), but limits the stoppage to the specific area of the find and allows activities to continue in the other sectors. The Secretariat may send staff within five business days, and the Council has twenty calendar days from the notice to decide whether an authorization is required. If it does not rule, the interested party may request a certificate that the deadline has expired, and from its issuance the Council is barred from ruling, unless human remains or bones are involved.

The new article 26 bis exempts minor interventions from authorization, with a simple notice on the Council's platform, but the criteria for qualifying them depend on a regulation that the Ministry of Cultures must issue within six months. Falsely declaring that an intervention is minor carries fines of ten to five hundred UTM (Unidades Tributarias Mensuales, an inflation-indexed Chilean monthly tax unit) and, if damage occurs, a prison sentence.

What the Constitutional Court left out

The original bill included compensation for the holder of an annulled RCA, determined by an arbitral tribunal. The Constitutional Court declared those provisions unconstitutional in its judgment of August 26, 2026, in joined cases 17.828-26, 17.829-26 and 17.832-26. Even so, articles 12 and 13 and the fourteenth transitional article of the published law still regulate that procedure. The Contraloría (Office of the Comptroller General), when reviewing the legality of the promulgation decree, warned that those provisions have no purpose and suggested that Congress regulate the matter. In practice, the holder of an annulled RCA has no special compensation procedure and remains subject to the general rules on State liability.

What we do not know yet

How will the new rules apply to the assessments and appeals that were under way on November 1? The law does not say, and the criterion of the Ley sobre Efecto Retroactivo de las Leyes (Law on the Retroactive Effect of Laws), under which deadlines that have already started to run and proceedings already initiated are governed by the previous law, will have to be adapted case by case. What will the new regulation understand by substantive modification and by technological improvement? Will the courts read article 24 bis as a complete closure of the RCA or only a partial one? In addition, the SEIA reform bill, Boletín N° 16.552-12, is still before Congress and could change part of these rules again.

With the mega-reform, an RCA is exposed to dispute for less time and through fewer routes. There are also fewer opportunities to correct the assessment along the way, and that makes it more valuable than ever to get it right from day one.