BIGGEST ROAD PROJECT IN YEARS READY TO OPEN

Five thousand tons of steel. Hundreds of giant, underground boulders blocking construction. Tens of millions of dollars.

After more than a decade of planning and three years of drilling, digging and pouring, one of the largest transportation projects to be completed in the region in recent years is about to open. By Friday afternoon, commuters will be streaming off an expanded Sunset Interchange on Interstate 90 into Issaquah and snaking their way north up a new, multilane road to the Sammamish Plateau.

As other regional transportation projects struggle to get off the ground, partnering parties bicker, the public grows restless and funding remains out of reach, this is a rare feat.

Despite major construction challenges and cost overruns, state planners said the interchange could be a model for how massive transportation projects could get done.

Two key ingredients: pressure for growth and a developer willing to contribute a sizable chunk of the cost.

About one-fifth of the funding for the nearly $178million interchange and road, and much of the drive, came from Port Blakely Communities, the company building a 3,250-home "urban village" called the Issaquah Highlands on the south end of the Plateau. Because of growth-management rules put in place more than a decade ago, the developer was not allowed to build until the transportation infrastructure was in place to support 6,000-7,000 new residents headed up the hill.

Though traffic in the area has been notoriously bad for years - isolating residents on the Plateau and trapping drivers in miles-long backups - it took the pressure of development to end the gridlock.

"We haven't had large-scale funding for big projects in a while," said Matt Preedy, project engineer with the state Department of Transportation (DOT), the lead agency on the interchange. "We'll be seeing a lot more of this type of thing: access to the freeway as a condition of development."

Congestion relief

Come Friday, commuters will be able to choose from three Issaquah freeway exits instead of two when they head home from Seattle or Bellevue. Planners expect the expanded interchange - which used to spit drivers onto I-90 heading east only toward the Cascades - to help alleviate heavy backups at the city's other two exits. The project also gives residents heading north to the newer half of Issaquah a straight shot.

The improvements are a package of three individual projects: the nearly $117 million interchange expansion was led by DOT; the $28 million southern section of the new six-lane Highlands Drive was built by Port Blakely; the $33 million northern section of Highlands Drive (which ends at the junction of Issaquah-Pine Lake Road and Issaquah-Fall City Road) was funded by King County.

Before the new improvements, about 60,000 cars a day entered and exited the freeway between the Front Street and Highway 900 interchanges. Now, that volume will be split three ways, Preedy said, potentially reducing dangerous exit queues that build up in the evening.

The deal allows all parties to pursue separate but linked goals: Port Blakely gets the go-ahead to build a profitable development; Issaquah can expand its tax base on newly annexed Plateau land; the state and King County provide better freeway and Plateau access without bearing the cost alone.

As part of the project, regional trails north and south of I-90 were linked. Port Blakely is "clustering" its development, leaving undeveloped 1,400 acres of public open space that local residents can still enjoy. For bus riders, King County Metro is planning a park-and-ride garage in the Highlands.

As Microsoft moves ahead with plans for a complex of up to 3 million square feet in the Issaquah Highlands, more workers from Seattle, Bellevue and around the region will benefit from better access.

"A developer certainly needs the infrastructure to sell homes, but part of it is also buying off the rest of the community to accept that growth," said Mark Hallenbeck, director of the Washington State Transportation Center at the University of Washington.

Port Blakely's involvement stems from the 1990 Growth Management Act, which gives cities the tools to restrict development until the infrastructure - roads, water, etc. - exists to support it. The concept is called "concurrency." In this case, concurrency led to the potential for traffic relief that the state otherwise couldn't afford on its own.

The agreement in this case was unusually strict: Port Blakely could build only a certain number of homes with each phase of transportation improvements. About 700 homes are open so far. When completed in 2008, the development will include stores, a movie theater and fitness center, along with about 2,500 more homes ranging in price from $175,000 to more than $800,000.

"It's good to see the infrastructure occur before development. It's exciting," said Fred Butler, Issaquah's mayor pro tem. "So many times, that hasn't happened."

Challenges and overruns

Despite enough money - a rarity in recent years - the project wasn't easy.

Soil problems, erosion controls and the discovery of hundreds of massive underground boulders caused $28 million in overruns and increased the construction estimate about 71 percent, said Ron Paananen, DOT deputy regional administrator.

The geography of the site - a mountain slope over sensitive Issaquah Creek - meant the waterway had to be temporarily diverted while fish were rescued, and crews had to struggle to keep the creek clean as they drilled, dug and poured concrete just feet away.

With so many partners - including Issaquah, King County and Sound Transit - the project required massive coordination efforts. Construction went in phases, and commuters and locals were faced with frustrating road closures.

To appease community concerns, designs, colors and building materials were selected to blend the hulking new overpass into its forested surroundings. The structural walls, for example, feature an unusual, floating leaf pattern that cost $250,000.

The key to future growth?

As developers eye what's left of buildable open space in the Puget Sound region, major contributions to transportation projects with regional implications will likely become more common, said Ivan Miller, a planner with the Puget Sound Regional Council who studies concurrency. Developers "have to play a larger role," he said. "Local funding is decreased, and if a developer wants their project done, this is what they need to do now."

Three years ago, Microsoft contributed to a similar but much smaller project at Northeast 40th Street off Highway 520, near its campus, transportation improvements critical to the growth of the software giant.

Such partnerships will be increasingly key for cities and suburbs that want to keep growth out of their congested centers. Creating a transportation network that links to population centers and regional roads is a way for cities to push into outlying areas without violating concurrency rules or stranding residents.

But it costs. Developing the transportation infrastructure to build on the Plateau ran Port Blakely about $15,000 per single-family unit, compared with $6,000 to $7,000 for most projects, said Judd Kirk, president of Port Blakely. The Issaquah section of the Plateau road leading up from the interchange - paid for by Port Blakely - cost $28 million, just over one-third of Issaquah's 2003 budget.

The costs could come in other forms as well.

New interchanges and arterial connectors allow developers to spread farther into open areas instead of building up urban cores. Even though developments like urban villages are usually considered smart growth, they can create more sprawl than six-story condominiums in the downtown center, Hallenbeck said.

Port Blakely's Kirk predicted the project will be an economic boon for the region, opening Issaquah, the Sammamish Plateau and east King County to new jobs, commercial outlets and residential growth. A project like the interchange is about more than getting from Point A to Point B, he said.

"Transportation isn't just about our convenience, it's about our economic vitality," he said. "We've been so spoiled in this region we've lost sight of that."

A 1999 economic-impact study by Idaho-based Real Estate Economics estimated the completed interchange and a completed Highlands would lead to the creation of 32,000 jobs, roughly half of which would be in the development. The completion of both projects would bring a tax benefit of $32 million annually to the state and $16 million to the city and county, in 1999 dollars, according to the study, which is being updated.

For locals, the true test may be far simpler.

"Are people looking to Issaquah to live?" asked Keith Niven, who manages development for Issaquah. "If so, then we're successful."

Natalie Singer: 206-464-2704 or nsinger@seattletimes.com