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