It seems clear the work was done mechanically and with intent. Horecny ran logging equipment within a fish-bearing stream channel on the Little North Fork of the Nehalem River. The earthen dam on the Long Beach Peninsula was built by The Trumpeter Swan Society. That group vowed to rebuild the structure. The wetland could refill within one month.
Progress is much more difficult to achieve than destruction.
In country folklore, it is said that a master carpenter takes months to build a sturdy barn, but that a jackass can kick it down in an afternoon. The Trumpeter Swan Society took responsibility for a situation that no other group was willing to face. By contrast, whoever destroyed the earthen dam is hiding behind the veil of anonymity. We are well past the point when an incident such as this could be dismissed as trivial. It is a stick in the eye.