ROAD CONSTRUCTION/County constructs arterial as part of road network
The King County (Wash.) Department of Transportation (KCDOT) is constructing the North Sammamish Plateau Access Road, which will connect plateau residents to Interstate 90. Known as the North SPAR, the project is part of a network that also includes a new interchange on I-90 and the South SPAR, which will connect I-90 to a high-density community.
Seattle has experienced phenomenal growth for 20 years, and that has been particularly true on the Sammamish Plateau, located 20 miles east of the city. During the 1980s, the 43-square-mile area was located entirely in unincorporated King County. However, by 2000, the population had quadrupled, and local government had been split between the county and two suburban cities.
The plateau is centrally located between I-90 and State Highway 520 — the most direct routes into Seattle from the eastern suburbs. As the area’s population has soared, interstate access has remained the same.
“We knew the area needed another connection to I-90,” says Harold Taniguchi, director of transportation for KCDOT. “Growth put the existing roadways close to capacity, but the intensity of the growth combined with changing land use made it harder to plan future projects.”
In the 1990s, King County officials decided to construct an expressway to I-90 through what was then an undeveloped area known as Grand Ridge. The county hired New York-based Parsons Brinckerhoff to conduct an environmental impact study in 1998, but, as the study progressed, both Grand Ridge and the Plateau changed dramatically: Residential and industrial development spread to the area, and Sammamish and Issaquah expanded their boundaries onto the Plateau.
Realizing that the county could not have an expressway running through a high-density, residential development, officials reconsidered the expressway plans. “The situation continued to change even after the environmental impact study was completed,” says Linda Dougherty, manager for the King County Road Services Division. “[Because of the increased development,] we needed to form partnerships to construct a corridor that would serve multiple needs and multiple jurisdictions.”
As a result, King County formed an inter-local agreement with Issaquah, the State Department of Transportation and Seattle-based Port Blakely Communities, a residential developer constructing a high-density community in Grand Ridge. Issaquah and Port Blakely have partnered to build the South SPAR, and the state is constructing the new I-90 Interchange. All four partners have an integral role in design, permitting and construction of all parts of the SPAR network.
King County started work on the one-mile-long North SPAR last spring by creating a couplet to separate traffic traveling through the Issaquah Highlands town center. The county also has re-channeled, re-signaled and re-aligned a busy Plateau intersection. KCDOT expects to complete work on the $30 million North SPAR project by fall 2003. When complete, the North SPAR will consist of four lanes with a left turn lane, curb and gutter, and a shared pathway for bicyclists and pedestrians.
