Adding “green” to the definition of complete streets

Perhaps not surprisingly, Cascadia’s coastal metropolises are among the leading cites experimenting in this vein. Critical needs—cleaning salmon-supporting waterways and preparing for more severe rainfall from climate change—have steered the region toward innovation to capture, store and clean street runoff. But those cities are not alone. Philadelphia in 2016 released a Green Streets Design Manual that explicitly expounds on the city’s 2012 Complete Streets Design Handbook. That historic city’s effort to bring nature to the right-of-way is central to the Green City, Clean Waters plan to convert 10,000 acres of impervious pavement to rain-water absorbing greenery, under a 25-year project to slash combined sewer overflows and comply with federal law.

One of the architects of the Philly program was Mami Hara, who became general manager/CEO of Seattle Public Utilities (SPU) in 2016. “We were trying to prove that green infrastructure can perform the technical needs for stormwater, but we also wanted to demonstrate other important values,” she said.

People feel better, and even behave differently, when nature softens the city. “We didn’t design to prevent crime,” said Hara. But when social scientists studied the phenomenon, “They found that areas where we implemented the program brought down crime.”

Denver began to rethink its approach to streets as long ago as 2008 with an initiative that came to be known as Living Streets, said Crissy Fanganello, the city’s director of transportation and mobility. The city adopted a complete streets policy and began installing protected bike lanes and retrofitting larger streets to reduce speeding and provide refuges for people on foot. Then came a post-recession development boom, with growing numbers of people walking and biking in the city’s denser neighborhoods. Even as the intensity of development increased, the city also was under the gun to stop dumping polluted runoff into the South Platte River.

Although agencies responsible for transportation, utilities and trees and open space tend to work separately when it comes to funding, Denver officials realized that would no longer be good enough. Over the last two years, experts from the various agencies formed a new joint initiative and with the city’s engineers developed a ground-breaking guide to retrofitting streets in “ultra-urban” areas. “The pollution removal value of green infrastructure is well established,” Fanganello said. “We want to help prove nationally that it also can have a traffic calming and safety benefit on our streets.”

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In the city’s River North arts district, known as RiNo, work already is under way along 15 blocks of Brighton Boulevard to convert a barren stretch of hardscape into an inviting place to walk, bike or wait for the bus. A first phase of the project is catching half the stormwater runoff, while a second is designed to capture every drop. Along the way, the boulevard will be lined with varying “amenity zones” that can include tree trenches, landscaped planting strips, benches for resting and art to contemplate. The trees provide shade for those on foot, while plantings will separate cars from bikes and bikes from pedestrians.

“The tight, green, complete street is the next frontier,” Maryman said. “The marketplaces of both ideas and products are helping.” With the growing demand for such streets, new technologies such as the load-bearing soil cells are emerging to make it possible to provide good growing soil for trees beneath a sidewalk, extending the areas for planting and the life of trees and sidewalks, he said.