Contaminated stormwater continues to flow from Tijuana into San Diego County

Editor’s note: This story has been updated to specify concerns related to contaminated stormwater.

Some 22 billion gallons of contaminated stormwater — which contains raw sewage — have flowed from Mexico into San Diego County since the end of December, the International Boundary and Water Commission (IBWC) reported on Wednesday.

“Transboundary flows continue down the Tijuana River from recent rains,” the IBWC, a binational entity responsible for shared water resources, said in a statement on Twitter.

“Total volume since end of December and the start of this unbroken and continuous flow is approximately 22 billion gallons,” the agency added.

Acknowledging that stormwater flows have dropped to 106 million gallons per day and continue to decrease, the agency noted that two wastewater collectors are out of service due to excessive sediment buildup. Last Thursday, flows reached 800 million gallons per day, according to the IBWC.

The wastewater influx is the result of an extended bout of winter weather, which has made a chronic cross-border sewage situation worse over the past few months.

The Tijuana River Watershed originates in the U.S. before heading into Mexico and then returning to California.

This means that “anytime they have any raw sewage discharge to the Tijuana River, it ends up in the U.S.,” Hassan Davani, an assistant professor at San Diego State University, recently told The Hill.

About 75 percent of the Tijuana River Watershed is located in Mexico, where it passes through the “densely urbanized city of Tijuana” before draining into the river and ending up in the Pacific Ocean via Imperial Beach, Calif., according to the California Water Boards.

In addition to facing storm-related wastewater flow, San Diego County has long been contending with infrastructural breakdowns that shuttle Tijuana’s wastewater north.

Most recently, an early February pipeline rupture near Tijuana led Mexican authorities to temporarily deactivate pumping stations in the local water conveyance system.

This created an acute “transboundary flow” of wastewater, the IBWC explained at the time.

About two weeks after the incident, authorities in Tijuana completed a temporary fix by diverting the flow from the broken conduit into a parallel pipeline and resuming pump operations.

As of last week, the IBWC reported that work on the main conduit was delayed due to rainfall, but the commission stressed that the bypass pipeline was still fully operational.

Several sections of the Southern California coast remain shuttered as “bacteria levels exceed health standards,” according to San Diego County’s Department of Environmental Health.

Those beaches include: Imperial Beach Shoreline, Border Field State Park and Tijuana Slough National Wildlife Refuge, as well as the Silver Strand and Coronado shorelines — both located on Coronado Island, just south of San Diego.

–Updated on March 13 at 2:09 p.m.