The difficult is what takes a little time; the impossible is what takes a little longer.
—Fridtjof Nansen, Nobel Peace Prize Winner, 1922
A veritable research and development laboratory of engineering and construction, the Central Artery/Tunnel Project, famously known as the Big Dig, was the largest infrastructure project ever undertaken in the United States and the largest inner-city construction project in the world. Its degree of difficulty was far greater than that of the other megaprojects of the twentieth century, the Panama Canal, the Hoover Dam, and the English Channel Tunnel. Those projects were constructed in “greenfield” sites. There was nothing there. The Big Dig, however, was constructed in the heart of a major, operating city. In addition, the proposed roadways were to be built off of the Colonial shoreline. That meant they would be built not on consolidated soil but on filled land, which possessed undetermined strength characteristics. Due to the proximity of the harbor, the water table throughout this unconsolidated soil was between 5 and 8 feet below the level of the streets. The deepest Big Dig tunnel would have a roadway surface 120 feet below the streets.
The Big Dig turned out to be quite a dichotomy. Challenges that had never before been faced were overcome not only in the design phase but also during construction, and on a daily basis. Technologically, the Big Dig is a resounding success, ...