June 9, 2015

Kirkland says green road project built to last 40 years instead of 20

Image courtesy of City of Kirkland [enlarge]

The international environmental group Greenroads gave Kirkland its highest rating for the Northeast 120th Street project, which won silver certification and earned 46 out of 118 points.

“Other projects have rated Greenroads Silver, but no project has earned 46 points,” said Dr. Jeralee Anderson, executive director of Greenroads.

Seattle-based Greenroads was formed in 2010 to advocate for sustainable road and bridge construction.

Kirkland found several ways to reduce the environmental impact of the 880-foot road extension such as LED street lighting and reusing old pavement for backfill. Crews built the road with warm-mix asphalt, rather than hot-mix, which reduces emissions and uses less energy to process asphalt.

Kirkland planted trees to protect Totem Lake from stormwater and built a 270,000-gallon concrete vault to capture and slowly release stormwater.

The street also has bike lanes and sidewalks on both sides, and there are bus stops nearby.

The city said in a press release that one of the best ways to reduce the environmental impacts of road construction is to build and repave roads less often. “One major decision right at the outset was using 40-year pavement instead of 20-year pavement,” says Jesse Thomsen, the Perteet engineer who led the street's design. “We looked at the total lifecycle cost and the benefit to the city. In the end, it didn't cost more to use Greenroads and the city got a longer lasting road.”

The primary difference between 40-year pavement and 20-year pavement is thickness. George Minassian, Kirkland streets engineer, says curbs and gutters on Northeast 120th Street were designed for thicker pavement.

More information about the project is at http://www.kirklandwa.gov under “NE 120th Extension.”