ALMA, Wis. — The Marquette Transportation Co. river boat Miss Doris pushed 12 barges through the Mississippi River lock at Alma on Tuesday, opening the new shipping season. The barges, from Davenport, Iowa, were bound for St. Paul, Minnesota. The Army Corps of Engineers anticipated no problem for Miss Doris upstream at Lake Pepin, which typically is the is the last part of the Upper Mississippi for winter ice to break up.