Sprouting Up: PWD debuts green roof bus shelter

A rendering of the green roof bus shelter | Image via phillywatersheds.org

Today, the Philadelphia Water Department announced the debut of a new green roof bus shelter at the intersection of 15th and Market, across from City Hall. The demonstration project is part of the PWD’s Green City, Clean Water, and the Mayor’s Greenworks Philadelphia initiatives, and represents one way in which stormwater can be managed in effective and aesthetically pleasing ways.

While most of the city’s green roofs are located several stories above street level, out of site to passersby, the bus shelter’s green roof will allow those who have never seen a sprouting roof to get an up-close look. Like its larger counterparts, the roof works in a layered system that nurtures plant life, manages rain water, and in this case, protects the SEPTA patrons below. Plus, given the triple-digit temperatures we’ve experienced this week, the system’s ability to ease summer heat is an added bonus to this sustainable structure.

Part of the PWD’s fleet of tools to transform the health of Philly’s waterways, the implementation and construction of the project was made possible by collaborations with the Mayor’s Office of Transportation and Utilities, the Mayor’s Office of Sustainability, the PA Department of Environmental Protection, Titan, and Roofmeadow, Inc. (the green roof company responsible for designing, installing and maintaining the structure).

Hopefully, this project is just the first in a series of city-wide bus shelter gardens. Doesn’t the thought of standing beneath the shade of blossoming greenery make waiting for the bus seem more bearable? Dare I say enjoyable?

But wait, how does a green roof's layered system work? Learn how after the jump!

Not as complicated as it seems. Green roofs are divided into five layers, each of which plays an important role:

Vegetation layer - the vegetation layer is made up of a variety of sedum species and plugs of perennial plants. This layer is pre-grown. To protect the young green roof plants and media from blowing in the wind, a photodegradable wind net is placed over the newly planted roof.

Growing medium - the lightweight soil (media) supports robust plant growth. Media is deeper in the corners above the bus shelter steel legs, where more weight can be supported.

Capillary fabric - to enhance water retention, we've added an engineered fabric that holds and evenly distributes water.

Root barrier - base green roof layers protect the roofing from roots and mechanical damage.

Reinforcement layer - water-resistant corrugated steel roof to both protect from the elements and facilitate drainage of excess water from the back of the shelter. A rigid mat above the metal roof creates a flat surface to support the rest of the green roof layers and a plastic sheet above the rigid mat holds the majority of rain water in the soil.

For more information on the city’s water-management projects, and how you can help, visit the Water Department’s Office of Watersheds website.