Caisson for Mackinac Bridge launch

The first section of the tower caissons were constructed at Alpena, MI, launched from the beach and towed by tugboat to the construction site 90 miles to the Northwest.  The "soil" was so hard that dynamite was used to break it up so drag lines could dig it out., Electronic reproduction of photograph.  The Mackinac Bridge 1954 - 1958. Mackinac Bridge Authority
Abstract/Description: The first section of the tower caissons were constructed at Alpena, MI, launched from the beach and towed by tugboat to the construction site 90 miles to the Northwest. The "soil" was so hard that dynamite was used to break it up so drag lines could dig it out.
Subject(s): Bridges--Design and construction
St. Ignace (Mich.)
Mackinaw City (Mich.)
Mackinac Bridge (Mich.)
Date Created: 1954 (approximate)