“Bertha,” the mammoth Highway 99 tunnel-drilling machine, arrived in Seattle on Tuesday from Japan. The ship is scheduled to dock Friday at Terminal 46, where 41 pieces, weighing 6,700 tons, will be unloaded over two weeks.

The green disk on deck is the rotary cutter head, the world’s largest at 57½ feet in diameter. The sections will be moved to the construction zone on flatbed trucks with as many as 96 axles and 768 tires. The drill will be assembled in a Sodo pit, where this summer it will begin the two-mile route to South Lake Union. The $2 billion, four-lane tunnel is to open to traffic at the start of 2016.

— Mike Lindblom, Seattle Times transportation reporter