Lt. Justin Westmiller said the bridge operator was tested at the scene of Sunday's accident and found to have a blood-alcohol level above Michigan's legal limit of 0.08 percent.
The Herbert C. Jackson was hauling 23,000 tons of iron pellets up the Rouge River to Dearborn's Severstal North America plant. The Interlakes Steamship Co. owns the ship.
The impact heavily damaged the bridge, but no people were hurt.
Westmiller said the ship was repaired and allowed to resume its travel.