A nearly half-billion-dollar investment in new sewage treatment facilities in Tijuana could clean up perpetually polluted beaches in San Diego, U.S. and Mexican officials say. Officials from both countries signed a treaty through the International Boundary and Water Commission that commits to funding new sanitation projects during a ceremony at the Tijuana River National Estuarine Research Reserve in Imperial Beach on Thursday. The agreement pledges about $350 million in U.S. spending and $144 million from the Mexican government to replace failing sewage treatment facilities in Tijuana.