20’ depth is a good start, but the big boys need 50’ and more.
about 35 ft
I don't remember where I saw the commentary, but a hat tip to the org/person that provided it. The bridge was originally designed to allow ships with drafts of 35 feet to pass under it. The shipping channel was 500 feet wide. At some point the shipping channel was widened to 700 feet and dredged to 50+ feet without adding any additional bridge pier protection..