The operator of the dredger is digging blind with only the help of mechanical sensors on the machine. Because the equipment floats on top of the river, a daily check of the depth of the river must be done to ensure they are pulling out the correct amount of material.
If you’ve crossed the Lake Street Bridge recently and looked to the south, you may have noticed a large machine working in the middle of the Mississippi.
The rig is a dredger, busy clearing sediment from the river to ensure that boats can navigate the channel without getting stuck.
The channel will be dug 200 feet wide and 12 feet deep, and will remove approximately 38,800 cubic yards of sediment from the river. “To get some perspective a large dump truck can probably hold 15 yards and a barge can hold 200 cubic yards,” notes Dan Cottrell, channel maintenance coordinator for the the U.S. Army Corps of Engineers. To meet the completion date of October 19th, the team needs to fill 10 barges per day. The barges travel to the 35W bridge, where the sediment is being stored.
The Corps is responsible for making sure that the channel is clear for passage and maintains the river from Minneapolis to Guttenburg, Iowa. “Last year was a record dredging year (since 1972), with more than 1.5 million cubic yards removed from the river. On average, the Corps removes 880,000 cubic yards,” said Cottrell.