Microsoft is digging for a solution to the parking crunch on its growing Redmond campus. The software giant is excavating a giant pit for...

Microsoft is digging for a solution to the parking crunch on its growing Redmond campus.

The software giant is excavating a giant pit for an underground parking garage with the capacity for some 5,000 vehicles.

That’s nearly as many spots as Bellevue Square boasts and would make it one of the largest underground parking structures in the United States.

It will cover the equivalent of six downtown city blocks and go four stories deep.

The underground garage, on the west side of Highway 520 near the Northeast 40th Street exit, is scheduled to be completed by mid-2008.

Microsoft now has nearly 29,000 parking spaces spread across its corporate campus, which straddles 520 and is growing on both sides — but particularly on the west side.

In 2006, the company announced a three-year plan to expand the campus by about one-third, or 3.1 million square feet, at a cost of roughly $1.3 billion.

Parking at Microsoft has become such a hassle that the company began offering valet service for employees working in some buildings, as a temporary measure during construction.

The new garage “will go a long way to helping out with that crunch that we feel,” Microsoft spokesman Lou Gellos said. “You’re going to see a net gain here of quite a few thousand spaces.”

He added that the 5,000 new spaces will not mean 5,000 more commuters on already clogged Highway 520.

While some of the campus expansion is to accommodate employment growth, it’s also meant to alleviate existing crowding in buildings and parking lots, Gellos said.

The huge parking garage, stretching between Northeast 36th and 40th streets, will primarily serve workers in four buildings planned for the area immediately around it, as well as others nearby.

The project involves more than just parking.

“When this is done, I think people will look to that area as the center of campus,” Gellos said. “It’s being designed and built that way,” with open space, a plaza, and other architectural and artistic touches planned to make the area pedestrian friendly.

Benjamin J. Romano: bromano@seattletimes.com