Complex sentence: In the years since the completion of the dam, the USACE stated that an estimated $1 billion in flooding damages have been prevented, and that during Hurricane Agnes in 1972, $210 million in damages was prevented, primarily to the city of Rochester.
Split into simpler sentences: In the years since the completion of the dam, the Army claims that more than $1 billion in flooding damages have been prevented. The Army claims that during Hurricane Agnes in 1972, $210 million in damages was prevented, primarily to the city of Rochester.