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Mexicali, Baja California: Wastewater and Treatment Project for the Mexicali II Service Area

Project Location and Description

EPA is considering authorizing the award of a Border Environment Infrastructure Fund (BEIF) grant to the Comisión Estatal de Servicios Publicos de Mexicali (CESPM), the local utility, for construction of a force main, pump station, new wastewater treatment plant (WWTP), and purchase of emergency pumping equipment. Mexicali, a municipality of around 800,000 people, is located just south of Calexico, California in Baja California, Mexico.

Purpose and Need for the Proposed Action

Wastewater generated by the Mexicali II service area was originally intended to be treated at a proposed new wastewater treatment plant in El Choropo, but this plant was not built because of public opposition from local residents. Consequently, approximately 14-16 million gallons per day (mgd) of untreated wastewater continues to enter the New River. This river originates 20 river miles south of the border, and travels 65 river miles through Calexico and the Imperial Valley, before emptying into the Salton Sea.

The new proposal by Mexico is to build this Wastewater Treatment Plant in a relatively uninhabited area known as Las Arenitas, located approximately 33 km (20.6 miles) south of the border. The pipeline, pump station, and WWTP will be sized to treat and convey 20.1 mgd (880 lps) to accommodate flows until the year 2014. A pumping station will be constructed, and 19 km (11.8 miles) more pipeline will be installed, given the increase in distance to the new location of the wastewater treatment plant.

The treated wastewater will be discharged south of the New River drainage basin, into a tributary of the Rio Hardy, which empties into the Colorado River Delta. The wastewater will therefore no longer enter the New River. This will result in a reduction of flows to the New River at the border of about 11% and a decrease of flows into the Salton Sea of about 1%. This will also reduce total phosphorous and orthophosphate loadings to the Salton Sea by 10% and loadings of total suspended solids (TSS) and biological oxygen demand (BOD5) in the New River at the International boundary by over 40% and 60% respectively.

EPA's involvement in the Mexicali project is part of a national commitment to improve environmental conditions along the U.S.-Mexico border. EPA participates in the development and implementation of water supply and wastewater infrastructure projects in coordination with the Border Environment Cooperation Commission (BECC) and the North American Development Bank (NADBank). BECC is responsible for certifying projects so that they comply with sound technical, environmental, financial, and public participation principles. NADBank administers the BEIF grants for projects that have been certified by BECC and approved by EPA.

In compliance with the National Environmental Policy Act (NEPA), EPA prepared an Environmental Assessment (EA) that analyzed the potential environmental impacts of the proposed project. Based on a review of the EA, EPA determined that the project will not have significant environmental impacts and prepared a Finding of No Significant Impact (FONSI). Both the EA and FONSI were available for public review and comment for a 30-day period that closed September 9, 2003. EPA has prepared a Response to Comments for comments received during the public review period. After fully considering these comments, EPA determined that the project will not have significant environmental impacts. The FONSI was signed by the Regional Administrator on December 10, 2003.

To view the EA, Response to Comments and signed FNSI, please click on the links below.

Contact Information

For further information about these documents, contact:S

Su Cox (cox.susan@epa.gov)
EPA Region 9 (WTR-4)
75 Hawthorne Street
San Francisco, CA 94105
Phone: (415) 972-3555
Fax: (415) 947-3537

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