<sod >Nearly 200,000 people were ordered to be evacuated as California authorities try to fix America's tallest dam that could unleash uncontrollable floods if it fails.< eod>< sod > Nearly 200,000 people remained under evacuation orders on Monday as California authorities desperately battle stop a collapse at the nation's tallest dam that could unleash 100 foot of uncontrolled flood waters if it fails.< eod>