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Bioswales and Stormwater Greenstreets

Bioswales are planted areas in the sidewalk that collect stormwater that runs off the sidewalk and along the curb when it rains.

A bioswale may look similar to a street tree pit or a small garden, but there are some key differences. Here’s how you can tell the difference:

Bioswale Breakdown

  1. Curb inlet - The inlet allows water to flow into the bioswale as it flows down the curb toward the catch basin.
  2. Outlet - Larger bioswales also have an outlet. If the bioswale fills to capacity, water can exit through the outlet and continue into the catch basin on the street corner.
  3. Stone Strip - The stone strip allows people to step out of their cars without damaging the plants.
  4. Plants - all bioswales have plants and grasses which have been carefully selected to ensure they can survive on busy New York City streets.
  5. Soil - The soil is graded so that water ponds in the center of the bioswale.
  6. Tree Guard - all bioswales have tree guards around them that protect the plants and keep people and dogs from walking inside of it.
  7. Tree - DEP plants trees in bioswales as often as possible. Trees benefit neighborhoods by lowering temperatures in hot summer months, improving air quality, and providing habitat for birds and butterflies.

Here’s how the bioswale functions:

Stormwater greenstreets are similar to bioswales but are constructed in the roadway and are usually larger. They vary in shape and size based on the characteristics of the roadway and street corner. Stormwater greenstreets can typically collect more stormwater runoff than bioswales.

Here are the neighborhoods where we are currently planning for, designing, or constructing bioswales and stormwater greenstreets.

You may notice the following activites on your block during the design and selection process: Teams of city employees and contractors walk around the city and identify locations for bioswales and stormwater greenstreets. When they find a good locations that meet the City’s pedestrian and vehicle clearance requirements, they will spray green paint on the sidewalk.

At each potential location, the City collects and tests samples of the underlying soil to see if it can absorb, or infiltrate, the stormwater. After the test is complete the hole is capped with concrete. Suveys are also performed and engineers work with utility companies to eliminate conflicts with existing service lines.

#5 Bioswale Construction Process
Bioswale Construction Sequence Album on Flickr