(NewsNation) — Federal officials have approved a $600 million plan that would help Southern California treat sewage flowing into the state from Mexico.

The United States Section of the International Boundary and Water Commission announced an expansion for the South Bay International Wastewater Treatment Plant in San Diego, which has been handling the flow of untreated water from the Tijuana River.

Officials estimate that in the past five years, the river carried at least “100 billion gallons of untreated sewage, industrial waste, and urban runoff (that) have spilled into the Tijuana Estuary and the Pacific Ocean via the Tijuana River and its tributaries.”

In 2023, the Los Angeles Times reported that the amount of contaminated water hit a high in 2023, with more than 44 billion gallons pumping across the U.S.-Mexico border.

“The health and environmental hazards created by this pollution has contaminated Southern California’s air and water for too long, and I’m committed to fighting for more federal resources to address this crisis with the urgency it demands,” said Sen. Alex Padilla, D-Calif., in a press release.

The rehabilitated and expanded plant would be able to process up to 75 million gallons of wastewater each day, according to the commission — at least double its current capacity.

Padilla, along with other California officials, secured funding in March for the project’s critical repairs.

Construction is estimated to finish in 20 months, though the maximum timeline for the project is five years. The plant should remain operational during the repairs.

Frank Fisher, a spokesperson for IBWC, told SFGate in an email the project will “improve the lives of communities on both sides of the border.”