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Building Stormwater Infrastructure to Serve as Community Amenities
Regional Stormwater Partnership of the Carolinas
Jonathan Smith, PE – Tetra Tech
February 26. 2020 Charlotte, NC
Impacts of Stormwater Runoff
Typical pre-development conditions:
Runoff = 10% Infiltration = 50%
Typical post-development conditions:
Runoff = 55% Infiltration = 15%
Traditional Approaches to the Issue
Primary Problems
Source: Mecklenburg County, City of Charlotte 4
Then We Tried Ponds and “Better” Channels
Image Credit: Tetra Tech
But Problems Persist
6
And New Problems Arose
7
Characteristics of Traditional Stormwater Infrastructure
• Pavement, Gutters, Pipes, Channels, Basins, Etc.
• Focuses on rapid removal of water
• Typically hidden or placed to avoid other infrastructure
• Out of sight/out of mind
• Limited funding
• Challenge: Doing more (function) with less ($)
8
Green Infrastructure
• "...the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters.“
• Provides several other benefits which are often described as the triple bottom line where there is a balance of demands and services provided environmentally, socially, and economically
Source : US-EPA
What if We Created Multifunctional Landscapes?
10
Bringing Stormwater into Public Space: Commercial
11
Bringing Stormwater into Public Space
12
Bringing Stormwater into Public Space
13
Bringing Stormwater into Public Space: Parks
Source: Beltline, Plancharlotte.org 14
What about Streets and Roads?
49%
29%
17%
5%
Land Area by Use in New York City
Building &Parking Lots
Streets
Parks &Open Space
Vacant Land
16%
17%
58%
6% 3%
Land Area by Use for a Residential Development
in Olympia, WA
Roof
Street
Lawn
Parking/DrivewaysSidewalk
All Transportation Surface = 26%(Impervious Surface Reduction Study. Olympia, WA, 1995)(PlaNYC Sustainable Stormwater Management Plan, 2008)
Green Infrastructure Toolbox
• Reduce Imperviousness
• Impervious Disconnection
• Rainwater Harvesting
• Green Roofs
• Bioretention
• Permeable Pavement
• Trees
Image Credit: Montgomery County, Maryland
Impervious Reduction
Image Credit: Tetra Tech, Dr. Bill Hunt
• Roadway width
• Sidewalks
• Driveways
Impervious Reduction
Image Credit: Tetra Tech, Dr. Bill Hunt
Downspout Disconnection
Image: New Columbia Neighborhood, Portland, OR. Credit: EPA
Impervious Disconnection
Image: Tetra Tech, Dr. Bill Hunt, NCSU
• Incorporate a growing media on a, typically flat, rooftop.
• Retains and filters precipitation
• Can enhance insulation function of roof surface and extend roof life
• Must consider additional weight of growing media and vegetation
Green Roofs
Image: Tetra Tech, Charlotte Stormwater Services
Rainwater Harvesting
Image: Tetra Tech
• A term that means holding back the stormwater for a short time and allowing it to have contact with plants, and soak, or “infiltrate,” into the ground.
• The process of bioretention can take several forms including rain gardens, curb bulb-outs, and planter boxes, and be incorporated in streets in a variety of ways.
Bioretention
Image: New Columbia Neighborhood, Portland, OR. Credit: EPA
Bioretention Basin/Rain Garden
Image Credit: Douglas County, Nebraska – Environmental Services
Bioretention Basin/Rain Garden
Image: Portland, OR. Credit: Kevin Robert Perry
Bioswales
Image Credit: Clean Water Services
• Linear landscape features that collect stormwater and allow the water to infiltrate
• Plants cleanse stormwater through biofiltration
• Work best along streets or parking lots.
Image: High Point Neighborhood, Seattle, WA. Credit: EPA; Toledo, OH Credit: Tetra Tech
Bioswales
Permeable Pavements
Permeable Interlocking Concrete Pavers (PICP)
Concrete Grid Pavers (CGP)
Pervious Concrete
Porous Asphalt
Plastic Reinforcing Grids (PG)
Permeable Paving
Image Credit: City of Portland Bureau of Environmental Services
The Importance of Urban Trees
• 1 mature tree can capture 50-100 gal during large storm
• Strategically placed can sage up to 56% on cooling costs
• Annually 100 trees….
▪ Remove 53 tons of CO2
• 430 lbs of other air pollutants
Credit US-EPA 30
Function % of Precipitation
Interception 20
Transpiration 10
Urban Tree Functional Concepts
• Benefit increases exponentially with tree size
• Conifers > deciduous
• Wider canopy shape is better
• Impact is more significant when canopy covers impervious rather than pervious
Credit US-EPA 31
Green Streets
32
Other Benefits of Green Infrastructure
• Desk workers who can see nature from their desks experience approx. ____% less time off sick.
▪ 5%
▪ 15%
▪ 25%
Other Benefits
• Study of green space amenity values related to customers’ price valuation, participants priced goods ____% higher in landscaped districts.
▪ 3%
▪ 9%
▪ 12%
Green and Complete Streets: Benefits
• Reduce Stormwater Flow
• Improve Water Quality
• Enhance Pedestrian Safety and Comfort
• Reduce Urban Heat Island Effect
• Reduce Carbon Footprint
• Beautify Neighborhoods
• Catalyst for Redevelopment
Image Credit: Montgomery County, Maryland
Improve Water Quality
• Reduce impervious surfaces
• Retain trees
• Remove pollutants
▪ Settling
▪ Filtration
▪ Infiltration
▪ Plant uptake and evapotranspiration
Image Credit: Washington DC Department of Transportation
Reduce Stormwater Flow
• Peak flow rates
• Flow volumes
• Duration of erosive flows
▪ Reduce impervious surfaces
▪ Retain trees/plant new trees
▪ Promote infiltration
▪ Peak flow attenuation
Image Credit: Philadelphia Water Department
Enhance Pedestrian Safety and Comfort
• Complete street design
▪ Calm traffic
▪ Improve comfort and safety for pedestrians and cyclists
Image : Hoboken, NJ. Credit: EPA
Reduce Urban Heat Island Effect
• Decrease hard surface areas that absorb and radiate heat with vegetative cover
▪ Lessen the amount of radiation absorbed by the surface
▪ Decrease ambient air temperature
▪ Lower energy demands needed to cool urban areas
Image : Seattle, WA. Credit: EPA
Reduce Carbon Footprint
• Encourage a shift in the way people choose to commute through:
▪ Safer pedestrian environments
▪ Bike facilities
▪ Beautified streetscape
Image : Indianapolis Cultural Trail. Credit: EPA
Beautify Neighborhoods
• Increase amount and variety of vegetation
• Introduce alternative materials and orientation for roads and sidewalks
• Improve pedestrian experience
• Enhance the character of the community
Image : Portland, OR. Credit: Kevin Robert Perry
Catalyst for Redevelopment
• Opportunity to create a green infrastructure network that can serve as enjoyable open space in a neighborhood
• Create a unique sense-of-place
• Being “green” can be a positive selling point
Image : NOMA Neighborhood, Washington, DC. Credit: EPA
Other Benefits of Green Infrastructure
• Desk workers who can see nature from their desks experience approx. ____% less time off sick.
▪ 5%
▪ 15%
▪ 25%
Other Benefits
• Study of green space amenity values related to customers’ price valuation, participants priced goods ____% higher in landscaped districts.
▪ 3%
▪ 9%
▪ 12%
Other Benefits
• People make more walking trips when they are aware of natural features, and judge distances to be greater than they actually are in less green neighborhoods.
▪ True
▪ False
Image : Navy Yards, Washington, DC. Credit: EPA
Sidewalks
Existing Street Green Street
Intersections
Credit: Philadelphia Water Department
Image : Navy Yards, Washington, DC. Credit: EPA
Intersections
Image : Kansas City, MO. Credit: BNIM Architects
Intersections
Medians
Credit: Virginia DOT
Medians
Portland, OR (EPA)
Washington, DC (EPA)
Portland, OR (Kevin Robert Perry)
Alleys
Before:
• Alleys flooded without connections to the city stormwater drains.
After:
• Water infiltrates through permeable pavement or infiltration basins, alleviating basement flooding of adjacent properties as well as reducing alley runoff.
Image : Chicago, IL. Credit: CDOT
Thank You