Potentially catastrophic structural failures last winter at America’s tallest dam left managers literally in the dark, despite years of federal urging to consider bolstering cameras and other monitors to give them time to alert the public in an emergency. State records reviewed by The Associated Press reveal for the first time the difficulty Oroville Dam managers had gauging the evolving dangers for 188,000 people downstream. On Feb. 12, as floodwaters washed away the second of two failing spillways, nightfall left managers struggling to observe what was happening at the half-century-old dam. State water officials scrambled to borrow cameras and helicopter rides from other agencies to get a look. Separately, federal regulatory documents show that since at least 2011, the panel that oversees U.S. hydropower dams expressed concern that Oroville and adjoining structures along the Feather River needed cameras and other monitors to spot structural failures.