Thursday, April 20, 2006, An average day for Pat Gould is pushing his giant machine two to three inches each minute, through tons of underground clay, mud and rocks on the way through a big hill where Sound Transit's light rail trains are expected to run someday.

A worker leaves Sound Transit's Beacon Hill light rail tunnel during a media tour Wednesday. A 642-ton tunnel-boring machine, nicknamed the Emerald Mole, is digging the tunnel.

So far Gould, who runs the machine boring the Sound Transit Beacon Hill tunnel, said he's had mostly good days, encountering easily moved soil and pebbles as the 330-foot-long machine has pushed under the hill.

"It runs real well, and it goes through this stuff real nice," Gould said during a media tour of the tunnel project Wednesday. "It's very manageable."

That's good news for Sound Transit and Obayashi Corp., Sound Transit contractor and Gould's employer, if it lasts.

So far Obayashi and its big machine have drilled just 400 feet into the west side of Beacon Hill on their way east, stopping four weeks ago so crews could build the long, elevated conveyor system that will start taking drilled-out material from the tunnel next week.

They'll push a quarter-mile more before reaching the dug-out shaft of the station, just east of Beacon Avenue South at South Lander Street, by sometime in July. They're waiting to make sure one platform of the station is done before pushing through with the boring machine and moving past the station.

Once that happens, they'll add two more shifts of workers and try to hit their goal of drilling 40 more feet of tunnel each workday.

The two tunnels eventually are to exit portals at 25th Avenue South near South McClellan Street, then connect on elevated rails to the new Mount Baker Station. From there, the rail line will continue south through Rainier Valley.

So far it's been a "textbook" start to the drilling, according to Obayashi tunnel manager Steve Redmond. The giant machine pulled the material out with few hitches. Gould maneuvers the drill end of the borer with jacks, using computer-stored coordinates to stay on course.

As the drilling machine moves, robotic arms raise pre-cast concrete tunnel wall sections into place. The drilling has gone well enough that the initial set of cutters is still in use.

Heading into largely unknown material, tunnel excavation is a risky business. Gould figures as the machine advances it will hit compacted glacial till soil -- hard, sandy stuff maybe filled with rocks. Progress will slow somewhat when that happens.

It won't be the first unexpected discovery in the tunnel project. A large underground vein of sand was found at the east edge of the Beacon Hill Station, and a year ago Sound Transit had to shift the location of underground passenger platforms, passenger pathways and ventilation tunnels 88 feet to the west to avoid the unstable material.

The sand vein wasn't detected in the test borings Sound Transit performed before construction began. "It isn't all nicely laid out in there," Obayashi project director Paul Zick said, describing the underground material as "kind of a hodgepodge."

Some wet, sandy soil also has been encountered as crews dug out the shafts connecting the rails to the above-ground Beacon Hill Station. The material was stabilized using wire mesh, pipe and grout.

"We're using, so far, a predictable amount (of stabilizing materials), but you never know what it's going to be like," Zick said.

The tunnels are scheduled to be completed sometime before winter ends in 2007, and all the work, including the Beacon Hill Station, is to be done by mid-2008 according to Sound Transit. When the entire 15.6-mile light rail is finished, it will extend from the downtown Seattle Transit Tunnel to Tukwila and to Seattle-Tacoma International Airport. It will cost an estimated $2.6 billion and is scheduled to go into service in 2009.