Cox Wins US$304 Million Contract for Rosarito Desalination Plant

Cox secured a US$304 million public contract from Mexico's National Water Commission (CONAGUA) to construct the Rosarito desalination plant in Baja California. The project addresses acute water scarcity in Tijuana and Playas de Rosarito by providing an independent local supply of 190 million liters daily, mitigating regional reliance on the overstressed Colorado River aqueduct system. This milestone initiative under the National Water Plan impacts urban utility governance, municipal infrastructure developers, and industrial water consumers across the US-Mexico border region.

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Cox has secured a US$304 million contract with Mexico’s National Water Commission (CONAGUA) to construct the Rosarito desalination plant in Baja California. The award mandates the engineering, specialized equipment procurement, and construction of an initial facility capable of treating 2,200 liters per second, supplying approximately 190 million liters of potable water daily to municipal distribution networks. The infrastructure will provide an independent drinking water source for one million residents across Playas de Rosarito and southwestern Tijuana, with construction scheduled to run over a three-year execution timeframe between August 2026 and July 2029.

The project represents a major capital commitment within Mexico's national infrastructure strategy and marks a significant step in Cox's corporate expansion across Latin America. “This project reaffirms our commitment to Mexico, following the acquisition of Iberdrola Mexico, in a country where we contribute our experience in the water sector with this award,” said Enrique Riquelme, Executive President, Cox. “We continue working for the development of infrastructure that contributes to the well-being of people and the sustainable growth of the country.”

Water Stress in Baja California

The Rosarito facility forms a core priority within the federal government's National Water Plan, promoted by CONAGUA to address chronic water stress and urban supply deficits in northern border communities. The restricted procurement process followed two previous public tender attempts that were declared void in late 2025 and mid-2026 when participating commercial bidders failed to satisfy technical, legal, and financial requirements outlined by water authorities.

The development of localized seawater desalination capacity addresses structural water supply vulnerabilities in Baja California’s coastal corridor. The Tijuana and Playas de Rosarito metropolitan areas have historically relied almost entirely on surface water conveyed from the Colorado River via the Río Colorado-Tijuana aqueduct, an administrative system that supplies water to nine out of ten families in the state's coastal zone. 

However, prolonged drought conditions across the Colorado River basin, rapid regional population growth, and strict international water allocation treaties between Mexico and the United States have heightened the necessity to establish alternative municipal water sources. Federal and state authorities project that the Rosarito plant will increase total drinking water availability for the Tijuana-Rosarito urban complex by up to 45%.

Technical Details

Engineered as a multi-stage regional infrastructure project, the Rosarito facility will eventually achieve a final design production capacity of 4,400 liters per second, equivalent to more than 380,000 cubic meters (m3) of potable water daily. Upon full operational deployment of all planned industrial modules, the facility will become the largest seawater desalination installation in Latin America. Principal infrastructure components for the initial phase include the main industrial processing plant, seawater intake structures, high-pressure water conveyance pipelines, an associated pumping station, and a regional storage reservoir designed to integrate directly with municipal distribution grids.

The facility will utilize seawater reverse osmosis technology, an advanced water treatment process that forces saline water through semi-permeable membranes under high pressure to eliminate dissolved salts, heavy minerals, and organic impurities. Cox noted that modern reverse osmosis delivers high operational efficiency, superior drinking water purity, and lower energy consumption intensity compared to thermal or older desalination alternatives. The technology allows coastal urban centers to build resilient, weather-independent municipal water supplies capable of sustaining industrial, commercial, and residential demand.

The Rosarito contract expands Cox's international portfolio of utility-scale water infrastructure assets. The group operates desalination facilities across 16 countries with an aggregate production capacity exceeding 4.4 million m3 per day. Cox previously constructed the Taweelah desalination plant in the United Arab Emirates, recognized as the world's largest reverse osmosis facility with a daily output of 909,000m3, as well as the Agadir desalination complex in Morocco serving agricultural irrigation and municipal consumption.