In April 1963, members of the California Water Pollution Control Association’s (CWPCA) San Diego Section reported on what was then seen as a major milestone: Mexico’s completion of the first stage of a wastewater reclamation and disposal system for the rapidly growing city of Tijuana. The article that follows captures the optimism of its time—the belief that engineering solutions, international cooperation, and water reuse could finally bring a long-standing cross-border pollution problem under control.
Photo by Abelardo L. Rodriguez
More than sixty years later, the Tijuana–San Diego watershed reminds us that water quality challenges are rarely solved once and for all. Untreated and partially treated wastewater from Tijuana still intermittently crosses the international boundary via the Tijuana River, affecting communities, ecosystems, and coastal waters in Southern California. Many of the pressures described in 1963—population growth, limited infrastructure, and sensitive receiving waters—remain central today, compounded by aging systems, storm-driven flows, and climate stressors.
At the same time, the response has grown far more sophisticated. Binational agencies and federal, state, and local partners are now investing billions of dollars in treatment plant expansions, interceptor repairs, diversion facilities, and watershed-scale controls. These efforts reflect a broader understanding that the challenge is no longer simply wastewater disposal, but long-term resilience in a shared and highly urbanized basin.
Read in this light, the 1963 article is not a historical artifact, it is a foundation. It documents early recognition of issues that continue to shape water quality management today and reminds us that lasting solutions require sustained commitment across generations.
Mexico Completes First Stage of Tijuana Reclamation System (San Diego Section, CWPCA Newsletter, April 1963)
Control of a persistent international pollution problem dating back to the 1920’s was achieved this past year when the Mexican Federal Government placed in operation what is eventually to become a wastewater reclamation system capable of handling the entire flow of the city of Tijuana, Mexico. San Diego’s sister city to the south is expected to ultimately generate 20 MGD of industrial and domestic wastes.
Tijuana lies immediately south of the U.S.-Mexican international boundary, which is the southern city limit of San Diego. The development of the City of Tijuana is primarily on hillsides which drain to the Tijuana River. The Tijuana River flows from Mexico into the United States and empties into the Pacific Ocean approximately one mile north of the international boundary, about five miles after entering the United States.
A large portion of Tijuana is not sewered (connected to a sewer line) now, nor is there a complete water distribution system. Water is supplied from an impoundment on the Tijuana River, from wells drilled in the river, and through a 16-mile aqueduct, which was completed late in 1962. Available water supplies are quite limited, and in fact, prior to the completion of the aqueduct, consumption of water and its attendant wastewater production decreased, although the population continued to increase.
In the late 1920’s, the lands on both sides of the border were sparsely inhabited and devoted to agriculture. Sewage from Tijuana was discharged directly into the Tijuana River and flowed across the border into the United States, causing objectionable conditions in this country. A community septic tank was constructed in 1928 to serve Tijuana and allowed for population growth to 5,000 people.
Sewage Contaminated Water-Border Field State Park / Imperial Beach, San Diego, California Photo by Tony Webster
The discharge of wastes from the septic tank continued to cause concern to the residents of the U.S. During the 1930’s an agreement was entered into between the County of San Diego and the federal governments of the United States and Mexico to construct and operate an outfall sewer which would collect wastes from both Tijuana and the community of San Ysidro in the United States and discharge these wastes into the Pacific Ocean near the mouth of the Tijuana River.
As is typical of most of California, the population “exploded.” The flow in the International Outfall Sewer reached 4.5 MGD of almost raw sewage, and beaches in the United States were quarantined as a result. The flow of sewage from Tijuana was about 4.3 MGD, while that from San Ysidro was 0.2 MGD, reflecting the difference in rate of growth of these communities.
At the urging of local, state, and federal American agencies and due to the extremely severe water shortage, the Mexican Federal Government decided to construct facilities to transport all of the wastewater produced in Tijuana to an agricultural area 16 miles south of the international boundary, where these waters would be used consumptively. The initial construction program consists of 3,800 feet of 42-inch diameter concrete pipe leading from the old treatment facility to the lower of two pumping stations. Each pumping station is constructed to house eight 2,000 gpm pumps. Force mains are two parallel asbestos cement pipes — one 24 inches, and one 20 inches in diameter — 14,000 feet long. There is an open channel and three siphons crossing deep ravines, 8.1 miles in total length, terminating in a drop section leading to the Pacific Ocean.
The pumping facilities are constructed to lift a maximum of 8,000 gpm against a total head of over 400 feet. The static head is 377 feet; 180 feet is the difference in elevation between the two pump stations. Power is provided to the pumps by 220 HP diesel engines connected through right angle drives. The lower pump station has a settling basin with comminution facilities included. This permits the use of small-clearance pumps which were necessitated by the high lift.
The eight miles (13 kilometers) of open channel terminate at a point 5.6 miles below the international boundary. Since the canal follows a hydraulic grade line, it is considerably longer than a comparable pipeline. The open channel is designed to carry a maximum flow of 30.6 MGD. As originally constructed, the channel was unlined except where crossing culverts. Subsequent use showed the need for additional areas to be lined. This work is progressing as time and money permit. The discharge of septic sewage into the upper end of the canal caused an odor problem, which was alleviated by installing about 500 meters (1,500 feet) of concrete pipe, thereby moving the venting area away from habitation.
Waste enters the ocean in a small bay six miles below the international border. There is a well-defined, visible sewage field approximately 1,000 feet long and 500 feet wide. Bacteriological sampling is conducted by the Mexican government with the advice of American health agencies. Five stations are sampled, the most distant being 0.3 miles south of the border. From the more than fifty samples that have been collected, it does not appear that polluting material reaches bathing waters off the United States.
Due to the water shortage in the Tijuana area, prior to the completion of the new aqueduct, sewage production had fallen to approximately 1.5 MGD. The greater availability of water is causing a gradual increase in wastewater production, and it is now about 2.5 MGD. The completion of the canal system to the areas where the wastewater could be profitably reclaimed for agricultural use may be delayed until the volume increases enough to justify the investment needed to transport and distribute the waters.
The Mexican Government is to be commended for their forward-looking approach in multiple use of waters in an area of water scarcity.
What’s Changed Since 1963?
Then (1963):
Now (2020s):
Continued population growth
What Hasn’t Changed:
My Profile
