Two new artificial-turf athletic fields and a track are expected to open at Marshfield High School in August as part of a $103.9 million high school construction project. To date, the project is running on time and on budget, according to building committee cochairman Bruce Spitler. One of the fields will be part of a new stadium, also expected to open in August, and the other will be encircled by a track. The new school is scheduled to open in the fall of 2014. Workers have nearly finished erecting structural steel for the classrooms, Spitler said, and the building should be fully enclosed, with interior work underway, when the fields open this summer. “Everything’s going very well,” he said.