karson_
I don't think the boundary for the Arsenal is correct. Federal government only owns the actual island + both dams. The actual waterway looks like it is owned by the either state DNR. Sylvan Island is 100% owned by the city and is a park.

https://ricogis.maps.arcgis.com/apps/webappviewer/index.html?id=f53cd25919f0443080b68c45e3144741   
&
https://maps.usgs.gov/padus/