Monday’s groundbreaking ceremony came two weeks after American Center for Mobility administrators closed on the $1.2 million purchase of 311 acres at the former General Motors plant and World War II bomber factory in Ypsilanti Township. By December 2017, the mobility center’s administrators hope to open a 2.5-mile highway loop as part of the project’s first phase. Construction will begin in earnest in the spring, said John Maddox, the center’s CEO.