Fifty-five feet below ground in the heart of downtown Ann Arbor is another world — one where construction workers toil through these chilly months to put in place the steel and concrete bones of a new underground parking structure. It's a first-of-its-kind project for Ann Arbor, and a bit of a logistical challenge for the Lansing-based Christman Co., the construction manager hired by the Ann Arbor Downtown Development Authority to complete the project. The amount of concrete being poured for the project is enough to construct a five-foot-wide sidewalk stretching for 133 miles. In fact, it's estimated it will take about 5,100 truckloads to deliver the entire 43,000 cubic yards of concrete over the course of the project. Another 9 million pounds of reinforcing steel are being embedded into that concrete. If they were laid out end to end, those bars would extend nearly 650 miles. It's also estimated that the amount of dirt excavated and removed from the site will have taken about 6,250 truckloads when all is said and done. Read the story here.