For almost a quarter-century, government and private research agencies dumped drums of radioactive waste into the waters just west of San Francisco’s Golden Gate Bridge — and now the waste is leaking into the Gulf of Farallones National Marine Sanctuary. Federal officials say they don’t have enough money to determine the extent of the damage; so far, scientists have studied only 15 percent of the disposal site and found that most of the radiation levels are not dangerously high. Still, environmentalists are calling for more research to study the effect of the radiation on marine life — not to mention the rest of the food chain. Perhaps most troubling, no one has any idea of how to clean up the mess, because the drums were dumped over 540 square miles of water from 300 to 6,000 feet deep, and many are so badly corroded that any attempts to move them would spread the waste further. That’s grim news for the 1,225 square-mile marine sanctuary, which surrounds the Farallon Islands, a national wildlife refuge that is home to 36 species of marine mammals.