It’s clearly a swing bridge looking at the photos and GE sat view, but it sounds like it hasn’t been used as such for many years.
It certainly has a fender system and control house for a swing bridge.
According to HistoricBridges.org:
This bridge no longer opens for boats, and has not operated since 1967. An old, but still active agreement with the Corps of Engineers states that if needed the bridge must be made movable within a year of notice.
This is not a swing bridge. Never has been as far as I
know (I was raised in Skagit County in the 50's). Jim in
Burlington, Wa.
Well, it was definitely built as one...