Tiohtià:ke (Montreal), 25 September 2026—On 22 September 2026, an organization established in Mexico that requested protection of its identity, filed a submission with the Secretariat of the Commission for Environmental Cooperation (CEC) under Chapter 24 of the Canada-United States-Mexico Agreement (CUSMA). The Submitter asserts that Mexico is failing to effectively enforce its environmental laws with respect to the assessment of the environmental impacts of the Margarita Maza dam, also known as the Mujer Solteca dam. The dam is intended to supply drinking water to the State of Oaxaca in Mexico.

In submission SEM-26-009 (Margarita Maza Dam Project), the Submitter asserts that the construction of the dam began on 10 June 2026, before the regional environmental impact statement (manifestación de impacto ambiental — MIA) was approved. In particular, the Submitter claims that the Ministry of the Environment and Natural Resources (Secretaría de Medio Ambiente y Recursos Naturales — Semarnat) did not respond to their request for a public consultation of the project and did not follow the procedures and timelines for public participation established in applicable environmental laws.

The Submitter further alleges that the environmental impact statement does not identify the protected species that would be affected by the project and does not consider effects on the ecological flow of the water body where it will be located, nor the risks of building the dam in a seismic zone. The Submitter states that they requested, without success, information on the land use change (cambio de uso de suelo), on the approval of the affected agrarian community, and on the prior, free and informed consent of affected agrarian communities. Although the Attorney General for Environmental Protection (Procuraduría Federal de Protección al Ambiente — Profepa) received complaints about the project, the Submitter states that it relied on a site inspection carried out on 9 December 2025, before construction began. The Submitter contends that Profepa should inspect the project during the construction phase in line with precautionary and preventive principles.

The Submitter cites provisions from the General Act of Ecological Balance and Environmental Protection (Ley General del Equilibrio Ecológico y la Protección al Ambiente — LGEEPA), the LGEEPA Regulations on Environmental Impact Assessment (Reglamento de la LGEEPA en Materia de Evaluación del Impacto Ambiental), the General Act on Sustainable Forest Development (Ley General de Desarrollo Forestal Sustentable — LGDFS) and its regulation, as well as the Mexican Official Standard NOM-059-SEMARNAT-2010.

The Secretariat will review the submission and determine, within 30 days, whether it meets the requirements of CUSMA Article 24.27 (1), (2), and (3).

To learn more about the SEM process and for more detailed information on this matter, please consult the registry page for submission SEM-26-009 (Margarita Maza Dam Project).