Old records have emerged indicating that potentially dangerous substances, including radioactive materials, may have been buried under a Berkeley waterfront park. Now, the State of California is ordering the city to begin testing. It started in January when the City of Berkeley got a letter from the State’s San Francisco Bay Regional Water Quality Control Board. The letter said that archive records had turned up about the now-defunct Stauffer Chemical Company’s dumping of industrial waste in five local landfills. One of them is now Cesar Chavez Park at the Berkeley waterfront.  The records show that, between 1960 and 1971, more than 11,000 tons of material were sent to the Berkeley site, including something called “alum mud,” a waste product of aluminum processing that often contains radioactive elements. The question is…is that what’s under the ground at the park?