Testing of the SR 99 tunneling machine continues in Japan
Before a professional athlete joins a new team, he has to pass a physical.
Same goes for Bertha, the world’s largest-diameter tunneling machine. She doesn’t play a sport, of course, but digging a two-mile-long tunnel beneath downtown Seattle requires just the right combination of speed, skill and body control – all hallmarks of a world-class athlete. Which is why Bertha’s manufacturer, Japanese firm Hitachi Zosen Corporation, is putting her through the wringer as they begin the long process of transferring ownership to Seattle Tunnel Partners (STP), the contracting team that will build the tunnel.
“The SR 99 Tunnel Project belongs to the people of Washington, but the tunnel boring machine will belong to us,” said STP Project Manager Chris Dixon. “It’s our responsibility to make sure everything is working properly before we start tunneling.”
That’s just what Hitachi and STP have been doing since December, when assembly of the five-story-tall machine was completed. Bertha has undergone extensive testing in recent weeks, with testing now about 60 percent finished. She was performing well until last week, when crews discovered that something wasn’t quite right with her main drive unit, which rotates the cutterhead. It appears there was insufficient clearance between a rotating and stationary portion of the main drive unit, which resulted in damage to some of its components.
While STP believes they understand the problem and have a solution, they need to partially disassemble the machine to get a better look (it was designed and built to be taken apart for shipment). Engineers will have a fuller understanding of how to fix the problem sometime next week, after they’ve examined it further.
It’s not unusual to discover issues during factory testing, Dixon said. In fact, engineers expect it. STP is working closely with Hitachi Zosen to make sure there is a sound solution to the problem before the machine leaves the manufacturing facility in Japan.
Once engineers give the okay, Bertha will be disassembled into 41 pieces and loaded on a ship to Seattle. She’ll arrive at the port terminal to the west of Seattle’s stadiums in early spring. Crews will then reassemble and fully test her again in the pit where she’s scheduled to begin her journey beneath downtown this summer. She won’t officially become the STP’s property until she’s tunneled approximately 1,000 feet without any issues.
“Our contract with STP is structured to minimize risk on taxpayers,” said Linea Laird, WSDOT’s administrator for the Alaskan Way Viaduct Replacement Program. “More than 90 percent of STP’s work will be performed for a fixed price.”
As in any large construction project, it’s likely that some individual work items will be delivered early, while others will fall behind schedule. Bottom line: this contract has only one major milestone – tunnel opening in late 2015. That’s the sort of single-minded goal that leads to success for world-class athletes, and, we hope, world-record tunneling machines.
So get on with the rest of that physical, Bertha. The team needs you.