A Minnesota dam is still intact after floodwaters overcame parts of the structure and prompted officials to prepare for a potential collapse. Authorities on Tuesday initially said the Rapidan Dam faced an “imminent threat” of collapse, but later said an abutment had partially failed. The river has swelled after an onslaught of rain pummeled the Midwest. Emergency managers say the dam is unlikely to fail entirely. But the episode has sparked questions about risks and potential collapse. County officials say flooding in recent years has caused significant damage to the dam’s structure and usability.