PORTAGE, Ind.—Indiana Dunes National Park closed its beaches and a northwest Indiana water utility shut down an intake facility after an orange substance apparently spilled from a U.S. Steel plant into a Lake Michigan tributary, a mayor said. Portage Mayor Sue Lynch said she began receiving calls about 5:50 p.m. Sunday reporting that an unknown substance had appeared in the water near the outfall of the U.S. Steel Midwest plant in Portage and then traveled toward Lake Michigan along the Burns Waterway, about 30 miles east of Chicago. “Now it’s all the way across the width of the channel into the open area, the mouth of the ditch,” Lynch said Sunday evening. A message seeking comment from U.S. Steel was left Monday morning by The Associated Press. Lynch told The (Northwest Indiana) Times she wasn’t sure what the substance could be, but an employee from the Portage Marina had collected …