The Union River flows southerly from Graham Lake, through Ellsworth, to Union River Bay, which is one of four northern arms of Blue Hill Bay and is located about 12 miles northwest of Bar Harbor. The use of the waterway from Ellsworth to Blue Hill Bay is limited to small recreational boats and a modest number of lobster boats.
Initial work in a 3.75-mile reach of the river, from the head of Union River Bay to Ellsworth, was completed in 1873 when the Corps removed sunken ledges, boulders, and sawdust. This gave the channel a depth of three feet and a width of 150 feet. The Corps also placed a spindle on the outer extremity of a sunken ledge at Fullerton Point.
The existing project, completed in 1911, involved removing additional ledges and boulders in the reach from Union River Bay to Ellsworth. This provided the channel with a depth of six feet and a width of 120-200 feet. Obstructions in the river were also removed, giving that section of the channel a depth of four feet.