Tacoma Builds Award-Winning Greenroad BY ASPHALTPRO STAFF
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To minimize cold joints and maximize smoothness, Miles Resources pulled two passes side by side and used a third paver to tie in side streets.
North America has a new, high-scoring environmentally sound project thanks to porous asphalt paving design in the City of Tacoma, Washington. The Greenroads Foundation, headquartered in Washington, manages a third-party certification process that assesses the sustainability of transportation projects using the Greenroads Rating System. For 2020, the foundation has awarded the City of Tacoma’s East 40th Street Green Infrastructure Project the Greenroads Silver Certification. The project earned 54 points and met all project requirements to become the highest-scoring Greenroads project in the world. The Sandy Forks Road project in Raleigh, North Carolina, which you can read about on TheAsphaltPro website, had held this distinction since November 2017. The East 40th Street Green Infrastructure Project reduces neighborhood flooding, enhances safety and increases accessibility, replaces underground utilities including water mains and sanitary sewers, and improves water quality by 99.8 percent for 39.1 acres in the First Creek, Lower Puyallup watershed. Localized flooding previously happened along this corridor because it is a low point in the East Tacoma neighborhood.
44 // November 2020
Let’s take a look at the project’s design, execution and success. It began in 2017, when the City of Tacoma’s environmental services division let the job to prime contractor Northwest Cascade Inc. and paving subcontractor Miles Resources LLC, Puyallup, Washington, to rebuild and pave a porous asphalt on East 40th Street. Pat McBride is the estimator/project manager for Miles Resources, and provided details of the mixes and design that made the new pavement structure possible. “In Western Washington, the projects requiring porous hot-mix asphalt (PHMA) are becoming more and more common,” McBride explained. “With this trend, the City of Tacoma, several asphalt paving contractors, asphalt designers and the Washington Asphalt Paving Association (WAPA) have been constantly working to create higher quality porous asphalt designs. This project was one of the initial projects in Western Washington using designs from this group’s efforts and yielded outstanding results that have helped improve PHMA and asphalt-treated permeable base (ATPB) design and placement throughout Western Washington.”
McBride explained that the project first required the team demolish the existing hardscapes and landscaping, replacing them with environmentally driven materials that would allow stormwater to infiltrate the new roadway, new landscaping and new sidewalks with the intention of furthering the advancement of clean stormwater systems in lieu of further adding to the city’s existing stormwater systems. Replacement meant paving with environmentally sound asphalt and best practices to ensure a long-lasting pavement structure that won’t require frequent maintenance. “Miles Resources executed the 2,224 tons of PHMA and ATPB paving in two lifts over the course of two days,” McBride said. “The goal was to pave the roadway with virtually no joints, as failures tend to occur in these types of projects at cold joints.” He explained the paving team accomplished this using three pavers; two of which worked side-by-side to place asphalt down the two-lane road while a third pulled the side streets in. “This was not only aesthetically pleasing, but created a uniform looking roadway with a smooth, bump-free surface,” McBride said.
