The U.S. Environmental Protection Agency said Friday it is reviewing a petition sent by San Diego County residents and elected officials asking the federal government to evaluate whether the polluted Tijuana River Valley may be eligible for Superfund designation. The U.S. Environmental Protection Agency said Friday it is reviewing a petition sent by San Diego County residents and elected officials asking the federal government to evaluate whether the polluted Tijuana River Valley may be eligible for Superfund designation. Environment Phys.org – latest science and technology news stories