Pushing cargo barges along rivers isn't necessarily easier when they're empty -- especially in windy conditions.
Instead, empty barges are more easily blown off course which is what happened near Munhall, just upriver from Pittsburgh on the Monongahela River Tuesday afternoon.
That's when a Campbell Transportation Co. towboat was blown against the riverbank as its 12 barges drifted sideways, blocking the 500-foot-wide river for about two hours.
Nobody was hurt.
Michael Monahan, Campbell's president, said empty barges ride high in the water turning them into "sailboats" when the wind blows. The National Weather Service reported winds above 20 mph, which is unusual for the Pittsburgh area.
An oily sheen was seen on the water, but no fuel spilled from the towboat.
Emergency officials said it came from oil trapped in river sediments that were churned up by the boats.