Rosarito Desalination


Rosarito Desalination and Otay Mesa Conveyance and Disinfection System Project

facilities in rosarito

Facilities in Rosarito – NSC Agua SWRO Desalination Plant Proposed Site (click image to enlarge).

Plans are underway to develop a seawater desalination facility in Playas de Rosarito, Baja California, Mexico. The facility will provide a reliable, high quality drought-proof water supply for the arid regions of Northern Baja California and potentially San Diego County. A binational concept in exploration since 2005, this project could soon be a reality and would be the first of its kind as a binational water supply solution.

Project Purpose

The primary purpose of the project is to provide a new supply to the Rosarito Beach – Tijuana area. From the desalination plant the product water would be conveyed to Tijuana’s water system for distribution. Because this plant is very close to the US-Mexico border, NSC Agua and Otay have been in discussions about the feasibility of oversizing the plant and conveyance system to provide an additional potable supply for Otay.

The drought continues to be a persistent topic in California as well as in Mexico. Due to the growing need for new potable water supplies in Mexico and San Diego County, the Rosarito Beach Desalination Plant and the Otay Water District’s (Otay) Otay Mesa Conveyance and Disinfection System Project (project) could provide a new drought-proof supply of water. Otay Water District provides water service to a population of more than 220,000 people, which is expected to increase to more than 308,000 by the year 2050.

Otay is the southernmost retail water agency in the State of California and its southerly border coincides with the U.S. – Mexico international border. Part of Otay’s service area is literally at the “end of the pipe” of imported water systems including the State Water Project, the Colorado River Aqueduct, and the San Diego County Water Authority (Water Authority), that collectively cover hundreds of miles.

In accordance with the State Water Plan and the diversification efforts of Metropolitan and the Water Authority, Otay is serious about investigating water supply alternatives to the current imported system. The surface water rights within Otay’s service area are owned by other agencies and groundwater resources are severely limited by the area geology and modest precipitation. Otay also has investigated two groundwater sources, but they proved to provide a small supply at a relatively high cost. Otay has maximized the use of recycled water. It has also been successful in conservation efforts, but Otay continues to explore innovative and creative ways of diversifying its water resources, reducing our dependence on strained traditional water supplies imported from the Colorado River and the Sacramento-San Joaquin Delta. Otay will continue to work with its stakeholders to educate our customers and other residents of San Diego County about the benefits of this binational project.

Public/Private Partnership

Public/Private Partnership

Aguas de Rosarito, a private consortium that signed a 40-year definitive public-private partnership agreement with the Baja California government on August 25, 2016 to build the plant and operate it for 37 years. Under the current schedule, operations would start in late 2019 or early 2020 under an initial phase that would produce 50-million gallons a day. The companies that make up Aguas de Rosarito are NuWater of Singapore, French-owned Degremont, a subsidiary of Suez Environment, and a Mexican company called NSC Agua that is a subsidiary of Cayman-Islands based Consolidated Water.

Through a public/private partnership, Consolidated Water Co. Ltd., a publicly traded company that designs, builds, operates and finances desalination plants and water distribution systems, will develop the Rosarito desalination facility (see sidebar).

Otay Mesa Conveyance and Disinfection Facility

Otay Mesa Conveyance and Disinfection Facility (click image to enlarge).

The Otay Mesa Conveyance and Disinfection System Project includes construction of a potable water pipeline and associated facilities to convey desalinated seawater from the border to Otay’s facilities in Otay Mesa. The Rosarito desalination facility will produce up to 100-million gallons of water per day and a portion of that water will potentially be distributed to the federal and/or state agencies serving the Rosarito and Tijuana areas, and to the Otay Water District. The project will be built in two phases. Phase 1, expected to be operational by late 2019, will make available 50-million gallons or more of desalinated water to the Tijuana/Rosarito region. The second phase, expected to be completed by 2024, will potentially deliver up to an additional 50-million gallon a day of water to Tijuana and Rosarito Beach with a portion to Otay.

The water that Otay would purchase could take the place of up to 70 percent of the water it currently receives from the Water Authority’s Carlsbad Desalination Plant and from imports from Northern California and the Colorado River, potentially distributing desalinated water to two thirds of Otay’s customers.

Desalination Plant in Rosarito

Desalination Plant site in Rosarito.

Aguas de Rosarito will construct a 25-mile pipeline to move water from the new Rosarito desalination facility to serve its potential customers in Mexico and the United States. On the U.S. side of the border, Otay will construct and operate a nearly 4-mile long pipeline from the border to convey the water to its distribution center in Otay Mesa. The proposed facilities on the U.S. side also include monitoring and metering stations, a potential pump station, and disinfection facility.

This project supports Otay’s mission statement, “To provide high value water and wastewater services to the customers of the Otay Water District in a professional, effective, and efficient manner” and Otay’s vision, “A District that is at the forefront in innovations to provide water services at affordable rates, with a reputation for outstanding customer service.”

Environmental Process and Documents

The crossing of the U.S. border by a water pipeline is subject to the Presidential Permit process, which includes a rigorous, transparent and objective environmental review. The Otay Water District’s Otay Mesa Conveyance and Disinfection System Project (project) is subject to environmental review pursuant to the California Environmental Quality Act (CEQA) and consistent with the National Environmental Policy Act (NEPA). Otay is the CEQA Lead Agency and the United States Department of State (DOS) is the federal lead agency for the proposed project. Otay is responsible for approving the expenditure of public funds for the proposed project and DOS is responsible for determining whether the proposed project serves the National Interest pursuant to Executive Order 11423, as amended, and if so, issuing a Presidential Permit to allow the pipeline to cross the international border. Otay and DOS prepared a joint EIR/EIS that identified and assessed potential environmental impacts, mitigation measures, and alternatives associated with the proposed pipeline project.

The Rosarito desalination plant also was subjected to environmental impact analysis as projects under Mexico’s environmental law, Ley General del Equilibrio Ecológico y la Protección al Ambiente (LGEEPA), which translates as the General Law for the Ecological Equilibrium and Environmental Protection.

Counterpart Agencies in Mexico/U.S.

Counterpart Agencies in Mexico/U.S. (click image to enlarge).

Cisco Consultoria Ambiental, an environmental consulting firm in Mexico, prepared a Manifestación de Impacto Ambiental (MIA), the Mexican equivalent of an Environmental Impact Statement, for each project of the following projects:

  • Rosarito Desalination Plant
  • Rosarito – El Florido Aqueduct
  • El Florido – Otay Aqueduct

The MIAs have a public notice period for receipt of comments similar to what is required for U.S. CEQA and NEPA documents. According to the Secretariat of Environment and Natural Resources (SEMARNAT) Resolution approving the MIAs, “no public comments, information requests, complaints, lawsuits, or written comments of any kind were submitted by a member of society, government agency, or organization in reference to the project.”

The three MIAs together provided clearance under LGEEPA for the construction and operation of the plant and connecting pipelines up to the U.S. border.


To view executive summaries in Spanish, click here.

Water Quality

water quality assurance

Project process schematic for water quality assurance (click image to enlarge).

The Otay Water District (Otay) has sought the assistance and early input of the California State Water Resources Control Board Division of Drinking Water (DDW) in helping Otay evaluate the feasibility for a unique new water supply opportunity. It would entail Otay’s purchase, at the U.S.-Mexico international border, of desalinated seawater produced in Mexico and conveyed to the border by a public-private partnership of Mexican agencies and a private developer (Aguas de Rosarito). Otay would convey the water from the border into its distribution system, providing water quality monitoring and additional disinfection as determined necessary.

Recognizing that such a project will require rigorous safeguards and review to ensure the protection of public health, Otay has been consulting with DDW on the regulatory requirements for permitting this project and to comment on the safeguards suggested that may be appropriate for a reliable, economical, and high quality water supply. This new water supply, just as any other potable source including surface water from lakes, the Claude “Bud” Lewis Carlsbad Desalination, and City of San Diego’s Pure Water Program, will meet the same high quality standards required by the DDW. This water supply will:

  • Comply with the California Safe Drinking Water Act.
  • Comply with the “Surface Water Treatment Rule” and “Long Term 2 Enhanced Surface Water Treatment Rule” including microbial and disinfection by-products rules.
  • Meet the pathogen log removal requirements established by DDW.
  • Comply with the “Public Health Security and Bioterrorism Preparedness Act” including preparing an emergency response plan.
  • Include ultrafiltration and microfiltration pretreatment, reverse osmosis treatment, disinfection, and post-treatment as part of the plant design process.
  • Monitored through the pipeline design and Operations Monitoring Plan to avoid potential contamination.
  • Include additional treatment after border crossing, most likely ultraviolet (UV).

Resources State Water Resources Control Board – Division of Drinking Water Programs

Estimated Schedule

EPA Notice in Federal RegisterSept. 2, 2016
DOS 30-day period for NI public comments beginsSept. 14, 2016
EPA 30-day notice period endsOct. 3, 2016
DOS 60-day period for NI Fed Agency comments beginsOct. 15, 2016
DOS 60-day period for NI Fed Agency comments endsDec. 15, 2016
DOS publishes ROD/NID in Federal Register*Dec. 22, 2016
DOS 15-day period for ROD/NID complete*Jan. 6, 2017
DOS issues Presidential Permit (May 16, 2017)By Jan. 27, 2017
Phase 1 – 50 MGDBy end of 2019
Phase 2 – additional 50 MGDBy end of 2024