The Imperial Beach shoreline was closed to beachgoers on Memorial Day after recent rainfall pushed sewage-contaminated runoff from the Tijuana River into local beaches.
The water contact closure, initially issued on Nov. 29, was expanded on Sunday to include the shoreline from the U.S.-Mexico border to the north end of Imperial Beach and 500 feet north of Carnation Avenue, the San Diego County Department of Environmental Health (DEH) said.
The agency warned people should avoid going into the water until testing has deemed it is safe for recreational use. Signs will be posted to notify beachgoers of the closures.
Closures of the Imperial Beach shoreline are common after a storm, which can cause the Tijuna River to flow and push runoff from Tijuana into the United States. A diverter, part of an agreement between the U.S. and Mexico, is shut down during heavy rainfall, according to the DEH.
Contaminated waters can then flow northwest via the Tijuana River, which crosses the border just west of the Otay Mesa Port of Entry, through the Tijuana River Estuary and into the Pacific Ocean south of Imperial Beach.
The constant closures and contaminated flow from Tijuana has long sparked contention between the South Bay community and the International Boundary Water Commission (IBWC), the agency that manages issues that affect both the U.S. and Mexico's waters.
In September, the San Diego Water Board sued the U.S. section of the IBWC, claiming it is violating the Clean Water Act by not monitoring or stopping untreated waste flowing to the ocean.
Several San Diego municipalities have also teamed up to file a federal lawsuit against the agency.
The IBWC said they have not violated any environmental laws and have actually "reduced the problem's scale" with the construction of a San Diego treatment plant.