An international environmental organization awarded the City of Kirkland on April 24 with the highest rating it has ever administered. Greenroads gave Kirkland’s Northeast 120th Street project its silver certification for earning 46 out of the organization’s 118 total points.

“Other projects have rated Greenroads Silver, but no project has earned 46 points,” said Dr. Jeralee Anderson, Executive Director of Greenroads. “The City of Kirkland made a commitment right from the start to make this as green as possible and it shows. That’s a testament to Kirkland’s commitment to sustainability.”

Kirkland earned those 46 points by seizing on several opportunities to reduce the 880-foot road extension’s environmental burden. Kirkland is using L.E.D. technology for street lighting. It reused old pavement for backfill and it built the road with warm-mix asphalt, rather than hot-mix asphalt, which both reduced emissions and the energy to process the asphalt by 50 to 100 degrees. To protect Totem Lake from the gushes of stormwater, Kirkland used trees to soak up some of that stormwater. It also built a 270,000-gallon concrete vault to capture and slowly release stormwater.

The street will also help reduce vehicle emissions by offering residents a variety of ways to travel. The extension features bike lanes and sidewalks on both sides, as well as nearby bus stops.

One of the best ways to reduce the environmental burden 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. For the City of Kirkland, the entire project was a winner.”

The primary difference between 40-year pavement and 20-year pavement is the pavement’s thickness. George Minassian, Kirkland’s streets engineer, says Kirkland was able to incorporate into the Northeast 120th Street design that additional thickness by specifying the heights of the road’s curbs and gutters around the pavement’s additional thickness.

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

For more information about the project, go to www.kirklandwa.gov and search “NE 120th Extension.”