Imperial Beach, a working-class community in Southern California, has been identified as one of the nation's dirtiest beaches, with bacteria levels frequently exceeding state health standards. A study by the Surfrider Foundation found that 89% of samples collected at the beach over the past year contained high levels of bacteria. As of July 21, the beach remains closed to swimmers and bathers due to an "imminent health threat associated with a sewage or chemical spill," according to San Diego Coastkeeper.
The affected area spans the ocean shoreline from the south end of Seacoast Drive to north of Carnation Avenue. Imperial Beach, along with other San Diego beaches, is impacted by sewage runoff originating from Tijuana, Mexico. This issue is exacerbated by the rapidly growing population in Tijuana and inadequate wastewater treatment infrastructure on both sides of the border.
Residents have reported adverse health effects, including headaches, asthma, and rashes, following exposure to contaminated water. Airborne pollutants from the Tijuana River have also led to modified schedules at local schools during periods of high pollution.
In an effort to address the water quality crisis, a new monitoring lab was established at the coastal hub in 2025 through a collaborative initiative involving the San Diego Chapter’s BWTF Clean Border Water Now programs and the local YMCA's Camp Surf.
The Surfrider Foundation's 2025 Clean Water Report analyzed over 10,000 water samples from 620 sites nationwide. The report identified 10 "Beach Bacteria Hot Spots" across the country where bacteria levels consistently surpassed state health standards for recreational waters. These locations, representing diverse recreational areas vital to local communities, were found to pose potential risks to public health.
While Hawaii's Punaluʻu Beach Park and Moloaʻa Stream Mouth were tied for the highest contamination rates at 100%, Imperial Beach's 89% bacteria rate placed it fourth nationally. Linda Mar Beach in Pacifica, California, also appeared on the list, with a bacteria rate of 72%.
Experts suggest that aging sewer systems, some dating back to the 1970s, may be contributing to the contamination issues at some of these beaches. Water quality experts suspect leaks in obsolete sewer mains may be the culprit.