SAN DIEGO(AP) -- U.S. and Mexican officials have dedicated the $160 million, 3.6-mile tunnel under the ocean floor that will help address the decades-long problem of untreated Mexican sewage flowing into the Tijuana River Valley, contaminating local beaches. The technically challenging project includes sections of tunnel 200 feet beneath the ocean floor, one mile of pipe on the ocean bottom, and state-of-the-art earthquake protection measures.
"The new ocean outfall is a significant step in resolving this important environmental and public health issue," said Dave Schlesinger, Director of the San Diego Metropolitan Wastewater Department, which constructed the outfall. "It's an important accomplishment that the entire binational community can be proud of."
The South Bay Ocean Outfall, which was constructed using the same technology that was used for the Channel Tunnel, or Chunnel, linking England to France, was funded by the U.S. Environmental Protection Agency and the City of San Diego.
In 1990, the United States and Mexico agreed to build an International Wastewater Treatment Plant on the U.S. side of the border to treat sewage that exceeds the capacity of Tijuana's existing sewage treatment system.
The city of San Diego and the International Boundary Water Commission jointly own the outfall, which can carry 174 million gallons per day on average and 333 million gallons per day at peak times.
Construction of the South Bay Ocean Outfall began in September 1995 under the direction of the city of San Diego Metropolitan Wastewater Department. The majority of the deep-ocean tunneling was done by a 330-feet long, 186-ton boring machine designed specifically for this project.
"The South Bay Ocean Outfall is an integral part of the international solution to the Tijuana sanitation problem envisioned in Minute 283," said John Bernal, commissioner of the IBWC. "The outfall will allow the treatment and disposal of Tijuana sewage up to the capacity of the advanced primary International Treatment Plant and relieve the U.S. from the need to use the emergency connection to the Point Loma Treatment Plant."
The outfall will discharge the treated wastewater at the end of the 3.6 mile tunnel, approximately 95 feet below the ocean surface. A diffuser then disburses the treated wastewater into the ocean at a seawater-to-wastewater ratio of 100-to-1, a ratio that complies with the California State Ocean Plan, the most stringent plan for ocean discharge in the world.
"The completion of the ocean outfall is a tribute to the continued cooperation of a host of unlikely partners on both sides of the border who share a commitment to protect their communities and the environment," said Felicia Marcus, regional administrator for U.S. EPA's westem region. "This is critical in our overall effort to stop the sewage siege and protect San Diego's beaches."
The South Bay Ocean Outfall crosses 14 fault zones and can withstand an earthquake measuring 7.5 on the Richter scale. It is buried under three grades of rock to keep the pipe in place and to provide storm and boat-anchor protection. An artificial reef that was developed as a result of the project has already become a home to local fish and other marine life.
The portion of the South Bay Ocean Outfall owned by the city of San Diego is funded by grants and sewer rates. It is part of the city's $1.9 billion capital improvement program that is improving wastewater collection, treatment, and disposal services for 1.9 million customers in the 450 square- mile service area by the Metropolitan Sewage System.
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