Transcript Slide 1

21st-Century Water Solutions:
How U.S. Cities are Using Green Infrastructure
to Curb Stormwater Runoff and Resulting
Combined Sewage Overflows
Stormwater Runoff is a Symptom
• Impervious surfaces, and therefore runoff, increase
with development
• Need to address the problem: development
• Green infrastructure practices can address 21stcentury development challenges
Green Infrastructure is a Solution
A cost-effective, sustainable, environmentally friendly
approach to wet weather management
Benefits include
- reduced volume of stormwater runoff
- reduced water treatment needs
- reduced grey infrastructure needs
- reduced flooding
- improved water quality
Chicago’s Progressive Agenda
One of the world’s largest wastewater collection/Rx
systems coupled with development
• 1970 start for $3.4B tunnel storing 2.5B gallons
• Green Roof program 1+ million square feet
• Green Alleys replace asphalt with permeable paving
• Green Technology Center
Milwaukee Measures its Plan
• 14-38% reduction in annual CSO volume with
downspout disconnection, rain barrels, and rain
gardens in residential areas
•22-76% reduction in annual CSO volume with green
roofs, rain gardens, and green parking lots in
commercial areas
6
Philadelphia is the Pioneer
• Invest more in green than grey infrastructure
• Rely on green infrastructure for most of required
overflow reduction
• Include enforceable requirements for city retrofit
• Leverage investments from the private sector to
help satisfy pollution reduction requirements
Summary of Literature
• Grey infrastructure mitigation is limited to end-ofpipe problems
• Green infrastructure offers opportunity to develop
new areas and retrofit existing developed areas—and
provide multiple benefits
• Growing evidence that in many cases its equally or
more economically efficient