This lock is 110 feet wide by 360 feet long. The locks are filled by a gravity system. Water leaves or enters the locks through two tunnels per lock. The main lock s tunnel is 12 and a half feet square and the auxiliary lock s tunnel is 10 feet square. A tainter valve at either end of the tunnels controls intake and outflow.
Water is taken in to the tunnels from the pool of water above the lock and let out below the lock.
The locks were complete before dam construction began so not to interfere with river traffic. In 1947, the towboat Alexander MacKenzie, in one trip, carried a cargo of 18,500 tons to St. Paul, Minnesota. This was half the annual tonnage towed by four Diamond Jo line river packets from 1900-1910. With improvements in river navigation came river transportation improvements. The slow moving, steam powered sidewheelers have been replaced by towboats that are powered by engines generating 5,000 plus horsepower.