Officials at border hail wastewater diversion system

Mexico's discharges won't flow into U.S.

TIJUANA — Two new water treatment plants in eastern Tijuana have been praised as critical for some of the city's newest neighborhoods. But they also created a binational problem: How to keep the treated discharge from flowing across the border and harming a federally protected U.S. wetland?

Yesterday, authorities celebrated the solution – a computerized system of pumps and pipes designed to keep the treated water inside Mexican territory and deliver it to the Pacific Ocean miles south of the border at Punta Bandera.

Authorities from Mexico and the United States gathered amid tubes, pools and motors of Pump Station No. 1, a 40-year-old structure near the border fence that is now an important part of the project to divert the treated water from the United States. Officials said the solution highlighted their interdependence as they address issues in the Tijuana River watershed that spans the border.

“This is a model that we must follow in terms of cooperation between our two countries,” Baja California Gov. José Guadalupe Osuna Millán said. The state and the Mexican federal government are sharing the $5.3 million cost.

For years, cross-border sewage spills from Tijuana into San Diego County led to beach closings north of the border. While dry-weather sewage spills have largely been eradicated, wet-weather flows have continued to lead to closures.

With a combined capacity of 20 million gallons per day, the Arturo Herrera and La Morita treatment plants are key to relieving Tijuana's overburdened main facility at Punta Bandera. Arturo Herrera began operating in March; La Morita is to open later this year.

But without the diversion system, their discharges would flow into the Tijuana River channel, potentially devastating the Tijuana River National Estuarine Research Reserve in Imperial Beach. The federally protected wetland is a saltwater marsh vulnerable to freshwater flows.

Oscar Romo, coastal training director at the estuary, said the estuary's ecosystem has already been altered by some freshwater intrusion from canyons near the border. But the new system will avoid further intrusion and “would probably relieve some of those changes,” Romo said.

The new system, set to begin operating later this year, involves two parallel pipes. One will carry the treated flow to be released directly into the ocean. The second will carry wastewater for treatment at Punta Bandera. Currently all the water, treated and untreated, is sent in a single pipe to Punta Bandera.

By separating the treated water and sending it directly to the ocean, the strain on the Punta Bandera plant should be reduced.

By installing the new system, Baja California authorities are complying with a U.S.-Mexico treaty requiring that dry-weather flows not cross the border. That is necessary to obtain funding from the U.S. Environmental Protection Agency, which has spent nearly $40 million on sewage infrastructure projects in Tijuana and Rosarito Beach.

“If they were sending water across, this would be a violation of the . . . treaty,” said Doug Liden, an environmental engineer with the EPA in San Diego.

Osuna said Baja California officials eventually hope to pipe the treated water to the Valle de Guadalupe, the state's main grape-growing region, for irrigation.

“I hope that the efforts at cooperation with treated water and sewage collection systems and the environment could be achieved with public security, for contraband, weapons and cash,” Osuna said.

By Sandra Dibble

Union-Tribune Staff Writer