SAN DIEGO—Members of San Diego’s congressional delegation Aug. 28 demanded answers as to why despite the dry weather, environmental officials are reporting an increase in sewage flow and strong odors from Mexico in the Tijuana River.

Reps. Juan Vargas, Sara Jacobs, Scott Peters, all D-San Diego; Mike Levin, D-Dana Point; and U.S. Sens. Alex Padilla and Laphonza Butler, both D-Calif., called on the U.S. Department of State to pressure Mexican officials for answers on the unprecedented dry weather sewage and sediment flows from Mexico.

“We write to you to express our deep concerns regarding the significant dry weather transboundary flows in the Tijuana River Valley, reports of increased sediment coming from Mexico, and the recent increase in odors coming from the Tijuana River Valley, and to urge you to press Mexican officials to address these issues as soon as possible,” the lawmakers wrote in a letter to the agency.

The International Boundary and Water Commission (IBWC) has reported an increase in sewage flows in the Tijuana River originating from Mexico. To date, Mexico has not identified the origin of the flows.

“Community members have reported that they cannot escape the persistent smell emanating from the Tijuana River,” the lawmakers continued in their letter to Secretary of State Anthony Blinken and U.S. Ambassador to Mexico Ken Salazar. “Residents of Imperial Beach and South San Diego County have shared that the sewage odors linger all day and night, frequently causing them to wake throughout the night from the smell. These increased flows affect the lives and livelihoods of the residents living near the Tijuana River and endanger the health and safety of our communities.

“These conditions may be contributing to the oppressive odors that residents of San Diego have been living with, so it’s important that we understand what steps Mexico is taking to address the sediment and identify the source of the dry weather flows.”

The IBWC believes a sediment buildup in the river is being caused by an ongoing highway construction project in Tijuana. As of June, more than 3,815 tons of sediment and trash have been removed from the South Bay International Wastewater Treatment Plant, a nearly five-fold increase over last year, officials said. The treatment plant is located at the San Diego border near the Tijuana River.

Purple pipes for reclaimed water at South Bay International Wastewater Treatment Plant in San Diego on Mar. 14, 2023. Seen in the background are the old border fence and houses in Tijuana, Mexico. (Jane Yang/The Epoch Times)

On June 17, the IBWC reported that sediment build-up caused a surge tank pressure relief valve at the Hollister pump station to fail, resulting in a spill at the plant that released 302,000 gallons of untreated wastewater onto the public right of way. Though the spill was cleared, the pump station remains offline, and, according to the IBWC, nearly 1 million gallons of transboundary wastewater continues to flow daily through nearby canyon collectors.