The G3 approach uses a variety of green street practices to:
· Reduce stormwater runoff,
· Capture and infiltrate stormwater on site,
· Improve water quality,
· Reduce energy use (lighting, heating, cooling),
· Increase pedestrian safety
· Improve community aesthetics and walkability
These practices include using a Green Infrastructure approach to green stormwater management. Green infrastructure uses engineered systems that mimic natural processes to increase infiltration or filtration of runoff, reduce flows, and enhance watershed health. Examples of green infrastructure includes pervious pavements, planted stormwater infiltration areas (curb bumpouts, rain gardens, bioinfiltration areas, bioswales), and increasing street trees / urban tree canopy. Along with addressing stormwater, Green Streets reduce energy costs through the use of solar lighting, help reduce urban summer temperatures (reduced heat island effect) which means less energy use to cool buildings, and incorporate recycled materials. Examples of these practices are provided below.
Stormwater is one of the largest water challenges in urban and suburban areas. Rainwater falling on impervious surfaces such as roads, sidewalks, and parking lots is not able to soak into the soil and quickly runs off the surface. As the water runs across these surfaces it collects pollutants such as oil and grease, animal waste, metals, and nutrients. Most of this water is directed to streams and rivers untreated. In many areas this pollution concern is even greater because the rainwater entering the sewer system causes untreated sewage to be discharged to rivers. The increased water pollution from stormwater impacts human health, fish ha In the Chesapeake Bay the only growing source of water pollution is from stormwater.
Along with pollution concerns, the increase in impervious surfaces leads to increase flooding. Even small rain events can lead to flooding in highly impervious areas. High volumes of water suddenly entering streams and rivers can lead to stream bank erosion, sedimentation, and loss of stream stability. This can mean loss of property and important infrastructure such as pipes, road, bridges, and culverts.
Addressing the stormwater from streets, roads, and alleys helps reduce impervious surface which reduces pollution, reduces flooding, and the impacts of high volumes of stormwater. For instance, in the Anacostia Watershed alone there are a total of 2,574 lane miles of roadway or impervious surfaces with approximately 1,809 miles of local, neighborhood & rural roads and city streets.
EPA –What is Green Infrastructure and Green Infrastructure Elements
Downspout disconnection refers to the rerouting of rooftop drainage pipes to drain rainwater to rain barrels, cisterns, or permeable areas instead of the storm sewer. Downspout disconnection stores stormwater and/or allows stormwater to infiltrate into the soil. This simple practice may have particularly great benefits in cities with combined sewer systems.
Rainwater harvesting systems collect and store rainfall for later use. When designed appropriately, rainwater harvesting systems slow and reduce runoff and provide a source of water. These systems may be particularly attractive in arid regions, where they can reduce demands on increasingly limited water supplies.
Capturing Rainwater to Replace Irrigation Water for Landscapes (PDF) (4 pp, 39K, About PDF)
Reducing Mains Water Use Through Rainwater Harvesting (PDF) (4 pp, 1.5MB, About PDF)
Rain gardens (also known as bioretention or bioinfiltration cells) are shallow, vegetated basins that collect and absorb runoff from rooftops, sidewalks, and streets. Rain gardens mimic natural hydrology by infiltrating and evapotranspiring runoff. Rain gardens are versatile features that can be installed in almost any unpaved space.
EPA Stormwater Menu of Best Management Practices (BMPs)
EPA Stormwater Technology Fact Sheet (PDF) (8 pp, 257K, About PDF)
Planter boxes are urban rain gardens with vertical walls and open or closed bottoms that collect and absorb runoff from sidewalks, parking lots, and streets. Planter boxes are ideal for space-limited sites in dense urban areas and as a streetscaping element.
Portland Stormwater Solutions: Infiltration Planters
Portland Stormwater Solutions: Flow-Through Planters
Performance Assessment of Three Types of Rainwater Detention Structures (PDF) (71 pp, 5MB, About PDF)
See Rain Gardens and Green Streets
How a Stormwater Planter Box Works
Bioswales are vegetated, mulched, or xeriscaped channels that provide treatment and retention as they move stormwater from one place to another. Vegetated swales slow, infiltrate, and filter stormwater flows. As linear features, vegetated swales are particularly suitable along streets and parking lots.
EPA Stormwater Menu of BMPs
EPA Stormwater Technology Fact Sheet (PDF) (7 pp, 81K, About PDF)
Florida Field Guide to Low Impact Development (PDF) (7 pp, 209K, About PDF)
Performance of Engineered Soil and Trees in a Parking Lot ale (PDF) (7 pp, 5.7MB, About PDF)
Water Quality Benefits of Grass Swales in Managing Highway Runoff (PDF) (10 pp, 218K, About PDF
Source: Philadelphia Green Streets Manual
Permeable pavements are paved surfaces that infiltrate, treat, and/or store rainwater where it falls. Permeable pavements may be constructed from pervious concrete, porous asphalt, permeable interlocking pavers, and several other materials. These pavements are particularly cost effective where land values are high and where flooding or icing is a problem.
EPA Stormwater Menu of BMPs: Pervious Concrete
EPA Stormwater Menu of BMPs: Porous Asphalt
EPA Stormwater Menu of BMPs: Pavers
How Permeable Pavement Works
Green streets and alleys integrate green infrastructure elements into the street and/or alley design design to store, infiltrate, and evapotranspire stormwater. Permeable pavement, bioswales, planter boxes, and trees are among the many green infrastructure features that may be woven into street or alley design.
EPA's Green Streets: A Conceptual Guide (PDF) (7 pp, 5.7MB, About PDF)
Sustainable Complete Streets (PDF) (3 pp, 357K, About PDF)
Portland Green Streets Fact Sheet
Seattle Public Utilities Natural Drainage Projects
Syracuse Green Street: Concord Place (PDF) (2 pp, 220K, About PDF)
Los Angeles Green Street: Elmer Ave
The Chicago Green Alley Handbook (PDF) (24 pp, 3.7MB, About PDF)
Many of the green infrastructure elements described above can be seamlessly integrated into parking lot designs. Permeable pavements can be installed in sections of a lot and rain gardens and ales can be included in medians and along a parking lot perimeter. Benefits include urban heat island mitigation and a more walkable built environment.
EPA Case Study: Bioretention Applications (PDF) (3 pp, 133K, About PDF)
Reducing Urban Heath Islands: Cool Pavements (PDF) (39 pp, 6.2MB, About PDF)
Green roofs are covered with growing media and vegetation that enable rainfall infiltration and evapotranspiration of stored water. Green roofs are particularly cost effective in dense urban areas where land values are high and on large industrial or office buildings where stormwater management costs may be high.
Many cities set tree canopy goals to restore some of the benefits provided by trees. Trees reduce and slow stormwater by intercepting precipitation in their leaves and branches. Homeowners, businesses, and cities can all participate in the planting and maintenance of trees throughout the urban environment.
Stormwater to Street Trees (PDF) (34 pp, 2.7MB, About PDF)
NEMO Fact Sheet: Control Stormwater Runoff with Trees (PDF) (2 pp, 126K, About PDF)
Protecting open spaces and sensitive natural areas within and adjacent to cities can mitigate the water quality and flooding impacts of urban stormwater while providing recreational opportunities for city residents. Natural areas that are particularly important in addressing water quality and flooding include riparian areas, wetlands, and steep hillsides.
Conservation Fund: 10 Green Infrastructure Case Studies
Using Smart Growth Techniques as Stormwater Best Management Practices
EPA's Protecting Water Resources with Higher Density Development
Greenways & Blueways
OTHER INNOVATIVE PRACTICES
To learn more visit Philadelphia's Green Streets Design Manual
Alternative energy generation for street lighting