Fact Sheet, August 1995

Background

Since the 1930's, raw sewage flowing into the United States from Mexico has posed a serious threat to public health and the environment in the South Bay communities of San Diego. This problem has gradually worsened over the years with the substantial growth of Tijuana's population and industrial sector. Although interim measures by the U.S. and Mexican governments have been effective on a short-term basis, untreated wastewater still flows into the Tijuana River valley today. In July 1990 the U.S. and Mexico agreed to build an International Wastewater Treatment Plant (IWTP) on the U.S. side of the border as part of a regional solution. This facility, now under construction, will treat sewage flows that exceed the capacity of the existing Tijuana sewage treatment system. In doing so, it will play a key role in restoring the environmental quality of the Tijuana River valley and safeguarding the health of its residents.

Project Description

The international treatment plant will be located on a 75-acre site just west of San Ysidro near the intersection of Dairy Mart and Monument roads. Construction of the IWTP's major components is being carried out in phases, with work already begun on the advanced primary treatment facilities. Additional components will include facilities for more stringent secondary sewage treatment and systems to divert canyon sewage flows into the treatment plant. The advanced primary treatment facilities use chemicals to accelerate the settling out of wastewater solids. Traditional secondary treatment facilities further treat the wastewater with a biological process that introduces microbes to break down the remaining organic matter. Once completed, the IWTP will treat an average of 25 million gallons per day (mgd) of wastewater to a secondary level, with the ability to treat an additional 50 mgd to the advanced primary level during peak flows.

Treated wastewater from the plant will be conveyed through an underground pipeline to the Pacific Ocean, where it will be discharged through a diffuser approximately 3.5 miles offshore at a depth of 95 feet. The 2.3 mile land-based section of the pipeline, known as the South Bay Land Outfall, has already been built. The South Bay Ocean Outfall, which extends the pipeline to its offshore discharge points, begins construction in late 1995.

IWTP Project Construction Timeline

	Begin:	Complete:
Site Preparation	July 1994	February 1995
Advanced Primary Treatment Facilities	July 1995	March 1997
Secondary Treatment Facilities	Following completion of SEIS
South Bay Land Outfall	August 1991	March 1994
South Bay Ocean Outfall	Late 1995	June 1998

Project Cost and Funding

The total cost of the IWTP and its ocean discharge system is about $400 million. Funding for the overall project is being provided by the U.S. and Mexican governments, with funding assistance for the ocean outfall provided by the City of San Diego.

Environmental Studies

In accordance with federal environmental regulations, the International Boundary and Water Commission and the U.S. Environmental Protection Agency completed an environmental impact statement and several environmental assessments to evaluate impacts associated with construction and operation of the IWTP. Because the advanced primary treatment facilities of the IWTP are scheduled for completion prior to the secondary treatment facilities and the South Bay Ocean Outfall, an interim discharge of the effluent is being considered

A supplemental environmental impact statement (SEIS) is currently being completed to evaluate options for discharging treated effluent before the other facilities are completed. A second SEIS will be prepared to evaluate alternative secondary treatment methods. The public will have an opportunity to provide input on these important environmental documents.

U.S.- Mexico Partnership

The U.S. and Mexico have formed a partnership to develop and implement a solution to the Tijuana-San Diego border wastewater treatment problem. This partnership, which has resulted in design and construction of the IWTP, involves the efforts of several agencies, including:

U.S. Environmental Protection Agency (U.S. EPA)--The U.S. EPA administers the majority of the project funding and serves as overall coordinator of the project.
International Boundary and Water Commission, United States and Mexico Sections (IBWC)--The IBWC is a century-old agency established by the governments of the U.S. and Mexico to resolve those differences that arise from the application of their boundary and water treaties, doing so through a joint international commission located at the border. The IBWC serves as the design and construction manager for the IWTP and the design manager for the South Bay Ocean Outfall.
City of San Diego, Metropolitan Wastewater Department (MWWD)-The City will serve as the construction manager for the South Bay Ocean Outfall, and has agreed to purchase up to 40 percent of capacity in order to discharge treated wastewater from the South Bay Water Reclamation Facility and any future wastewater treatment facilities that may be built in the South Bay.
State of California, State Water Resources Control Board WRCB)--The SWRCB serves as a technical advisor to the IWTP policy committee.

For More Information

Over the next several months, public input will play an important role in evaluating interim discharge options as well as secondary treatment options. If you have any questions or concerns about the project, please contact:

U.S. Environmental Protection Agency
San Diego Border Office
(619) 235-4769

International Boundary and Water Commission
San Ysidro Field Office
(619) 662-7600

Fact Sheet, August 1995

IWTP Project Construction Timeline

Project Cost and Funding

Environmental Studies

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