Sound Transit (ST) contractors recently began drilling 180-foot-deep holes in two Husky Stadium parking lots as part of the research phase for an underground light rail system, ST and UW officials said.

When they finish, operators from the two drilling rigs will have drilled about 20 holes in the E11, E12 and C12 parking lots. Drilling is estimated to wrap up during the first or second week of July.

The light rail, called U-Link, will run 3.15 miles through Capitol Hill to downtown Seattle. Most of this drilling research is for the train station, which will be built at the same level as the rail itself, about 100 feet underground.

Two on-site geologists have been studying the soil samples in 4-to-5-foot sections. Operators bring intact samples to the surface through two different drilling methods, sonic and wire-line carrying.

On-site geologist Schuyler Johnston explained that with the wire-line method, a drilling rig uses a metal cord to lower a drill attached to a metal pipe. Within that pipe is another pipe that holds the actual sample, while the outer layer excretes a clay-like mud that helps break down the soil and lubricate the drill.

The sonic, or Rotosonic, drill does not use mud but vibrates about 8,000 times per minute to aid the turning motion of the drill.

"It's basically the world's biggest vibrator," drill operator Ken Phillips said.

On average the sonic drill is faster but produces lower-quality samples, on-site geologist Nels Reese said. The sonic drill also produces less waste and can drill about twice as deep.

Vibrations and electromagnetic interference are the two major concerns of the Board of Regents. If either becomes too intense, the train could affect sensitive hospital research and equipment.

"They can impact sensitive, high-resolution machines, like MRIs," said UW project manager Andy Casillas, who has been working as a liaison between ST and the UW.

Construction could start as early as fall quarter 2008 but heavy construction, which includes beginning the excavation, will not begin until later in 2009.

Casillas said that before digging can start, builders have to relocate several service utilities such as water and electricity.

The tunnel will be made with a boring device that lays down a concrete liner as it digs.

As part of ST's commitment to minimize impact at the UW, Gray said, workers will take vibration measurements while the train is running as well as during construction.

"We've had zero complaints about vibrations as the tunnel boring machine is going under people's houses," Gray said.

The primary traffic impact will come from moving the soil out of the U-District, but they plan to transport most of it during off hours, Casillas said.

"There will definitely be added traffic," he said. "[ST will] do whatever they can to mitigate traffic impacts throughout Montlake."

ST hopes to finish U-Link by 2016, which includes two years of design, six years of construction and six months of testing.

ST media spokesman Bruce Gray said the U-Link project will cost about $1.6 billion, and ST is in the process of securing a $750 million grant from the federal government that would prevent tax increases for the project.

November's ballot will have a measure for East Link, which would expand the light rail from the UW to Snohomish County.

By 2030, an average of 70,000 people are expected to ride U-Link daily, including activity between downtown and Capitol Hill stations.

Gray said the fares have not been determined, and ST does not know if the U-Pass will be accepted on U-Link.

"It's something that we're shooting for, but because it's so far out from now, the U-Pass could be something entirely different," Gray said.