Seattle Tunnel Partners will pour its final concrete pillar next week to complete an access pit along the waterfront, so the front end of stuck Highway 99 tunnel machine Bertha can be extracted and repaired.
Workers from Malcolm Drilling are building a ring of 73 pillars, some 120 feet deep, near the foot of South Main Street. Another 11 new pillars near the ring will help support a huge crane, to be assembled this fall. Current plans are to hoist the entire 2,000-ton front end as one piece, then separate the components at the surface. Hitachi-Zosen, the machine manufacturer, will replace the main bearing, surround it with tougher seals, and reinforce the rotary drive system with extra steel ribs and plates.
During September, groundwater will be pumped away, before the soil is scooped out from inside the ring. Bertha will then grind forward and break through the south side of the ring, exposing its cutter head to open air.
The Washington State Department of Transportation posted an update Thursday, along with a six-minute video featuring Seattle Tunnel Partners (STP) director Chris Dixon and color diagrams of the new drill parts.
Bertha ground to a halt in early December, after the front end overheated and grit appeared in the bearing grease. The 57 1/3-foot wide drill is supposed to resume its journey to South Lake Union by March 2015. Work continues on the two portals and maintenance building. More than $1 billion has been paid to STP already, in a $1.44 billion contract, not including any cost overruns borne by the contractors, the state’s taxpayers, or both.
A barge docked this week at Terminal 46, to assist STP workers adjusting the overhead conveyor system, said state spokeswoman Laura Newborn. After digging resumes, the conveyors will drop dirt on barges, to be shipped to a quarry near Port Ludlow.