Between Alma, Wisconsin and Kellogg, Minnesota, USA (June 2009)
The United States Army Corps of Engineers (USACE) operates a series of twenty seven locks and dams along the Upper Mississippi River between St. Paul, Minnesota and Granite City, Illinois (near St. Louis). Lock and Dam Number 4 is one of the furthest upstream, as signified by its low number (map)
Commerce
USACE manages this system of locks and dams to make sure the upper stretch of the Mississippi River is navigable to commercial vessels. Most are dry bulk cargo barges that carry wheat and other commodities from these breadbasket states to markets worldwide. Others deliver coal upriver to the power plants that provide electricity throughout the Midwest.
The Corps maintains a water level of at least nine feet which is necessary for safe navigation of these heavily-laden vessels. The Mississippi River, if allowed to flow naturally, would not guarantee the proper depth necessary all the way up to Minneapolis throughout the year. USACE constructed an elaborate system of locks and dams to deal with the situation. Water pools behind the dams to the required depth and locks allow boats to bypass the dams. Waterborne commercial transportation thus takes place more than two thousand miles into the North American interior.
Easy to Watch
Lock and Dam Number 4 spans between Alma, Wisconsin and Kellogg, Minnesota, with the actual lock on the Wisconsin side of the river. There are a number of locks that can be accessed from the Great River Road (State Road 35 in this stretch), but at this spot it is amazingly convenient to watch a lock in action. There’s even a parking lot provided right along the road in the middle of town.
From there it’s as simple as walking onto the pedestrian overpass over the railroad tracks and down to a viewing platform right next to the action. We came upon the site at a particularly lucky moment as the lock prepared for the entry of a raft of barges push by a tugboat preparing for its journey past the obstacle.
Passing Through the Lock
This particular lock stretches 600 feet long and 110 feet wide. It provided just enough space for a raft of nine barges — three wide and three long — plus the tugboat Deana Ann, to enter into the slot. We were watching as this raft headed downstream.
The lock was at its lowest water level, having just disgorged another vessel heading south. Two massive steel doors swung shut and the lock filled with water in only a few moments. The upper doors swung open, the tugboat and its barges pushed into the slot, and the assembled flotilla was lowered. Now at downriver level, the tugboats and its barges moved beyond the dam. It would travel another fifteen miles before encountering the next lock.
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