Favorable environmental impact for the Mar Menor's green filters, with conditions

The General Directorate of Quality and Environmental Evaluation has formulated the environmental impact statement for the project “Basic projects for green filters and semi-natural wetlands in the surroundings of the Mar Menor,” which is proceeding with conditions. The resolution, signed on September 3, 2026, is published in the Official State Gazette (BOE) no. 230, of September 17, 2026, with the reference BOE-A-2026-19403. The promoter and substantive body is the General Directorate of Biodiversity, Forests and Desertification of the Ministry for the Ecological Transition and the Demographic Challenge (MITECO).

The project falls under line 2.1 of the Framework of Priority Actions to recover the Mar Menor (MAPMM), “Restoration of ecosystems in the perimeter strip of the Mar Menor and the creation of the Green Belt,” in its April 2024 update. The request to initiate the procedure entered the environmental body on July 22, 2024, while the public information announcement had been published in the BOE on November 4, 2023. The file is processed through the ordinary procedure in accordance with Law 21/2013, of December 9, on environmental assessment (Annex I, group 9, section b).

From five actions to two

The initial design contemplated five green filters and semi-natural wetlands:

• Torre del Negro, in Cartagena: 124.73 hectares, of which 48.79 are semi-natural wetland, discharging into the rambla del Miedo.
• El Albujón, in Cartagena: 33.44 hectares, 15.87 of wetland, destined for the rambla del Albujón.
• Miranda, in Cartagena: 70.94 hectares, 31 of wetland, destined for the rambla de Miranda.
• Los Alcázares, in Los Alcázares: 11.41 hectares, 3.80 of wetland, destined for the D7 drainage canal.
• El Mirador, in San Javier: 19.85 hectares, 8 of wetland, with reuse for municipal purposes.

Following the public information process and consultations, the promoter excluded El Mirador due to a lack of definition regarding the destination of its waters, interference with a livestock route, and its lower contribution to the objectives. Regional reports detected significant impacts on the SAC ES6200006 “Open Spaces and Islands of the Mar Menor,” especially in the Marina del Carmolí, due to the effluents from Miranda and Torre del Negro; the promoter withdrew both on May 5, 2026. The procedure is therefore limited to El Albujón and Los Alcázares, which total approximately 45 hectares.

How the denitrification system works

The objective is to denitrify the waters of the quaternary aquifer of the Campo de Cartagena, reduce the over-elevation of the water table and its discharge into the Mar Menor, and improve the freshening of coastal salt marshes such as the Marina del Carmolí. The system extracts water through boreholes and pumping 24 hours a day with a constant flow of 35 liters per second, with a maximum annual volume of 1.49 hm³.

• El Albujón: 1.1 hm³/year, eight new wells and 88 photovoltaic panels with a peak power of 350 W.
• Los Alcázares: 0.39 hm³/year, six new wells, 44 panels and a circular tank of 39 m³.

The water passes through organic chip filters, preferably from citrus fruits, where it is expected to remove 75% of the nitrates; it then passes through a subsurface flow artificial wetland planted with common reed (Phragmites australis) and, finally, semi-natural wetlands, with an efficiency of 90%. The combined efficiency can reach 97.5%. The wells will be 35 to 40 meters deep and the perimeter will be revegetated with helophyte species and salt cedar (Tamarix boveana). In Los Alcázares, a salt marsh of community interest habitat 1510* is also recovered over 939 m².

Environmental conditions and monitoring

The resolution establishes 33 conditions. Among them:

• Construction may only begin once the entity responsible for operation, maintenance, and monitoring is completely defined.
• Before the works, a control plan for mosquitoes, vectors, and botulism must be developed, reported by the General Directorate of Public Health and Addictions and the General Directorate of Natural Heritage and Climate Action of the Region of Murcia.
• A study of heavy metals in the soil will be required, with leaching tests and special attention to lead.
• In El Albujón, from March 1 to August 1, only the least noisy tasks will be carried out due to the nests of the mongolian Harrier and marsh harrier; in Los Alcázares, there will be no disturbances to birds from March 1 to September 1.
• A piezometric and water quality network will be available, with a groundwater flow model coordinated with the IGME.
• Monitoring reports will be submitted to the substantive body every six months during the first five years of operation.
• Emergency plans against the risk of flooding will be drafted, with watertightness for a flood with a 500-year return period.

During the processing, the Segura Hydrographic Confederation, the Mar Menor Technical Office, the IGME, city councils, and irrigation communities provided reports, and allegations were received from environmental groups, entities, and 14 individuals.

The decision clears the environmental framework for a centerpiece of the lagoon’s recovery plan, but leaves open the question of who will assume its operation: without that prior definition, the works cannot begin. Furthermore, the conditions reinforce control over mosquitoes, heavy metals, and flow rates, the three fronts that concentrated the objections from neighbors and institutions.

Source: Official State Gazette, no. 230, of September 17, 2026, Sec. III. Other provisions, page 123381 (official reference: BOE-A-2026-19403).