IMPERIAL BEACH, California/TIJUANA, Mexico—Each day, millions of gallons of sewage cascade through a canyon and into the Pacific Ocean just south of the U.S.-Mexican border. As any surfer in San Diego knows, summer swells that come from the south will push the toxic brew north.
Meanwhile, millions more gallons of treated and untreated sewage trickle down the Tijuana River and into the sea just north of the border.
