VIDEO: A teen charged with second-degree arson in the Madison County Bridge fire pleaded guilty Monday, a Madison County court clerk said. Alivia Bergmann, 19, of Des Moines told a judge that she helped start the fire that destroyed the iconic covered Cedar Bridge in Madison County on April 15. Bergmann was one of three teens arrested following the fire. Alexander Hoff, 17, of West Des Moines was originally charged with first-degree arson, but the charge was dropped to second-degree arson. Joel Davis, 18, of Norwalk was also charged with second-degree arson. Both Hoff and Davis will be tried as adults.