Saint Anthony Falls - Locks and Dams

Locks and Dams

St. Anthony Falls was the upper limit of commercial navigation on the Mississippi until two dams and a series of locks were built between 1948 and 1963 by the United States Army Corps of Engineers. The locks make commercial navigation possible above Minneapolis but, since the locks in Minneapolis are smaller than most of the locks on the river, the practical limit for many commercial tows is further downriver. A smaller number of barges go to Minneapolis.

Completed in 1963, the upper St. Anthony Falls dam is a horseshoe-shaped hydro-electric dam 93 feet (28 m) in height. The upper pool has a normal capacity of 3,150 acre feet (3,890,000 m3) and a normal level of 799 feet (244 m) above sea level. The navigation channel required alteration of the historic Stone Arch Bridge, which now has a metal truss section to allow ships to pass below.

Completed in 1956, the Lower St. Anthony Falls dam is a gravity-type hydro-electric dam 60 feet (18 m) in height, consisting of a 275 foot (84 m) long concrete spillway with 4 tainter gates. The lower pool (sometimes called the intermediate pool) has a normal capacity of 375 acre feet (463,000 m3) and a normal level of 750 feet (229 m) above sea level.

The pool below the lower dam has a normal level of 725 feet (221 m) above sea level.

The upper and lower locks are each 56 feet (17 m) wide by 400 feet (122 m) long.

The current around the spillway/falls is often swift and dangerous. In 1991, a small boat drifted too close and fell over one part of the dam. One person onboard was killed, and one had to be rescued by helicopter. Rescues at the site are usually much less dramatic, but continue to happen occasionally.