On June 11, 2014, "Big Alma" broke through to the North Beach extraction shaft, joining "Mom Chung", which had arrived on June 2. The arrival of the TBMs marked the completion the boring operation phase. The two TBMs were to be disassembled and removed, and the extraction shaft filled in by the end of 2014. The twin tunnels were fully complete by May 2015, when Mayor Ed Lee toured the project underground. Each completed tunnel is long and in diameter, supported by 1,750 concrete rings placed during the boring operation.