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Building Sustainability from the Ground Up

Green Infrastructure in the Central Addition

To get a good grasp of what green infrastructure is all about, let’s start with rain. If you’ve ever walked through a forest during a rainstorm, you’ve probably noticed that the plants and soil are nature’s way of capturing all the rain that falls. The forest acts as a sponge, catching rainfall on leaves and absorbing water into the soil and vegetation.

Now let’s say you were walking in that same rainstorm in downtown Boise, or any urban setting. When we develop land and construct buildings, we replace trees and soil with roofs and pavement, which disturb natural function, decreasing the places rainwater can be absorbed and filtered. The result is called stormwater runoff. Instead of water being absorbed into the ground and vegetation, runoff is channeled to the nearest water body, in this case the Boise River.  Not only does runoff increase the risk for flooding, but all that water collected on streets, roofs and parking lots flows unfiltered to the river, picking up whatever it collects along the way, including harmful pollution like trash, bacteria and chemicals.

Thankfully, cities are embracing innovative tools to better manage stormwater runoff. Utilizing a new approach called green infrastructure, cities are implementing practices to make our urban environment work more like the forest.

Boise’s first LIV District in the Central Addition was designed to act as a laboratory to allow the city, residents and businesses to test some cutting-edge sustainability practices. If you’ve noticed construction around Broad Street recently, you likely saw the installation of green infrastructure. At the heart of the LIV District, Broad Street represented an opportunity to not only rebuild a street, but to invest in technology that will result in a cleaner river. Let’s look at some of Broad Street’s “greener” features:

Tree planted in planter along a street with sidewalks

Streetscape Design

Streetscape Design

Broad Street highlights a design that features a narrow street with an additional row of street trees and planting areas. The trees and plants catch the rainfall and use it for the water that they need to grow.  Narrow streets also mean less pavement, or impervious surface that can collect and channel runoff into the Boise River. By incorporating more green space, trees and vegetation, Broad Street’s streetscape is not only visually appealing, but brings sustainable practices to downtown Boise.

Street level photo of pavers with gaps where water can filter.

Permeable Pavers

Permeable Pavers

The next time you’re riding your bike, parking your car, or taking a walk down Broad Street, pay attention to the parking lanes along the street. Permeable pavers provide a solid, street surface with gaps where water can filter between the pavers and into the underlying soil. As simple as it sounds, these pavers offer a model for streets and parking lots across the city, resulting in a cleaner Boise River going forward.

Bulldozer shovel dumping dirt into ground on top of Silva Cells that allow stormwater runoff under sidewalks

Silva Cells

Silva Cells

Trees along Broad Street use a new product, known as Silva Cells, which are hiding in plain sight below the sidewalk. Instead of the typical hard-packed dirt under sidewalks that has limited ability to absorb water, Silva Cells offer a space for special planting soil to filter pollution from stormwater runoff.  The additional space below the sidewalk also allows trees to grow larger and healthier. Broad Street is built on some amazing innovation right under your feet.

Together, the combined green infrastructure can manage and filter over 180,000 gallons of stormwater runoff from public streets and private properties in an area approximately 10 City blocks in size.  This new concept for managing runoff was made possible by the innovation and collaboration that is a keystone of the LIV District.

To learn more about the Central Addition, Boise’s first LIV District, check out this post.

Published: September 14, 2017