Toxic runoff from Tijuana River invades Imperial Beach

The southern shoreline of Imperial Beach has been closed since November due to water pollution spilling over the border from Mexico—including about 110 million gallons of toxic stormwater runoff in the last two months.

The biggest surge came last week when nearly 57 million gallons of sewage-tainted water gushed into the United States through the Tijuana River, according to the U.S. section of the International Boundary and Water Commission. The flows consisted mainly of rainwater but also carried sewage and other pollution.

"We've had a couple wet winters that have stressed the stormwater system in Tijuana, which is at a breaking point," said Dave Gibson, executive officer of the San Diego Regional Water Quality Control Board. "We see a deteriorating sewer system that's going to be overwhelmed with more water as more residents pour into the city."

The commission's Mexican counterpart, the Comision Internacional de Limites y Aguas, constructed a sandbag berm in the main channel of the Tijuana River this month to prevent flows from crossing into the San Diego region. But the berm, as well as the agency's pumping and diversion systems at the border, have been overwhelmed by the recent rainfall.

Banned pesticides and industrial chemicals have also been found in recent months in water flowing through canyons along the border. A report compiled by U.S. Customs and Border Protection identified the pesticide DDT, hexavalent chromium and other known carcinogens in the water.

San Diego is at the end of a large watershed that starts in the mountains in and around Tijuana. When it rains, water rushes across the city, picking up trash and other pollution as it flows north, eventually into the Pacific Ocean.

Compounding the issue, makeshift communities built in the canyons just south of the border have grown in recent years, with residents emptying their trash and wastewater directly into flood-control channels that carry water to the canyons at the border.

"For millions of years, the land was excavated by the force of water, creating this pretty large canyon, and the entire city of Tijuana sits in the banks of that canyon," said Oscar Romo, a professor of urban studies and planning at the University of California, San Diego who has studied water pollution in the region. "There's no neighborhood that escapes the river."

The International Boundary and Water Commission has a collection system to divert flows in the river valley's major canyons, such as Goat Canyon and Smuggler's Gulch. Much of the polluted flows are sent to the South Bay International Wastewater Treatment plant. But the system is routinely overwhelmed in wet weather.

Imperial Beach, Chula Vista, the Port of San Diego and the San Diego Regional Water Quality Control Board have sued the federal government for allowing the situation to persist. The plaintiffs would like to see a beefed-up diversion system and funding for sewage infrastructure in Tijuana.

"The nonstop spills of sewage into the Tijuana River over the past weeks highlight the reasons why Imperial Beach, San Diego, Chula Vista, the Port of San Diego, California and the Surfrider Foundation have sued the Trump administration," Imperial Beach Mayor Serge Dedina said. "This is an environmental and public health disaster."

Lawyers for the defense argue the government isn't legally responsible for the renegade flows that escape their collection systems, pointing out that the situation would be significantly worse without its network of pumps and capture basins.

Tijuana's aging and limited sewer system has struggled in recent years to serve the region's growing population. Experts and government officials agree that hundreds of millions of dollars in infrastructure funding is needed to keep water pollution from spilling over the border.

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