A barge broke free and went aground on Lake Michigan off the south breakwater at Sheboygan, Wisconsin.  The barge was  being pushed by the 108 meter long tugboat Donald C when heavy seas and strong winds separated the two vessels.  The Donald C was unable to regain control of the barge before it went ashore.   No reports of injuries or pollution released.  The barge is to be inspected and refloated later.  The barge was carrying a cargo of rocks bound for Manitowoc, Wisconsin.