HYAK, Wash. – The sheer magnitude of it is difficult to comprehend, even in person.

More than one million tons of rock to be blasted and removed.

Three hundred cubic yards of concrete poured into individual bridge pier shafts, of which there will be a total of 74.

Six new bridges, two of which are nearly 1,200 feet long.

Huge drill bits that bore holes 9 feet in diameter for the piers. Some will reach depths of 180 feet.

All of this is taking place in a narrow, congested three-mile stretch of the most heavily traveled east-west highway in the state of Washington, where 27,000 vehicles whiz by each weekday. The number nearly doubles on weekends and holidays.

Those are some of the numbers related to the widening and other improvements to Interstate 90 east of the summit of Snoqualmie Pass, one of the largest road projects currently under way by the state Department of Transportation.

The $570 million improvement on five miles, from Hyak to Keechelus Dam, will take four years to complete. But when done, the section of I-90 will feature six newly constructed lanes, a snowshed extending across the entire freeway for a distance of 1,200 feet, and a longer area for motorists to remove tire chains.

While motorists will have a safer route and less congestion, wildlife also will benefit.

The elevated bridges will allow safe passage for bears, deer, elk, cougars and other species through the highway corridor to maintain connections to habitat and access to food sources.

Gold Creek, where one set of bridges is being constructed, is home to bull trout, listed as threatened under the Endangered Species Act. A longer span will allow the creek to spread out, creating additional habitat for bull trout.

A detour for eastbound traffic was completed last year so the current lanes can be used to stage for the new bridges – and keep traffic flowing.

“The biggest part of this job was to do this significant work constructing six bridges with the lake on one side and the mountains at the toe of a very steep hillside on the other,” said Bob Hooker, assistant project engineer for the state Department of Transportation. “This is a tricky area. The key message is we have been able to do this while keeping two lanes of traffic open.”

“It’s a big deal,” he added.

But some delays will be necessary to make this project happen. The freeway is closed in each direction for an hour Monday through Thursday to allow for blasting and removal of rock to occur.

Hooker said the blasting will continue for two more years to separate the highway from the steep hillside by as much as 120 feet in places.

This four-mile stretch of the interstate will be replaced with new concrete, which better withstands the freeze and thaw that occurs near the summit.

The current project is funded by the 9.5-cent gas tax increase the Legislature approved in 2005.