Some of the best environmental projects also save money. This post at The Atlantic’s Cities blog highlights urban green infrastructure such as permeable pavement projects, including a recent study finding that they can also be economical:
Looking at 479 case studies of green infrastructure projects around the U.S., the report finds that the majority of projects turned out to be just as affordable or even more so than traditional “grey” infrastructure. About a quarter of projects raised costs, 31 percent, kept costs the same and more than 44 percent actually brought costs down.
Here’s the logic: suppose you are, as Chicago is doing, using permeable concrete now when repaving alleys. Permeable concrete is more expensive than traditional concrete, but because it allows rainwater to return to groundwater, it reduces the water flow into storm drains, the sewer system, and wastewater treatment facilities. So you have to evaluate the higher construction costs versus the lower wastewater treatment cost and other reduced costs of storm runoff, including lower operating and maintenance costs. As reported in the post:
The costs of traditional infrastructure are especially pronounced in cities and regions with combined sewer systems that collect both sewage and stormwater. During heavy rainfall, these systems are often overwhelmed, pouring sewage-laden water into drinking water sources and greatly increasing water treatment costs.
Technologies like permeable pavements and rain gardens can capture, naturally treat and filter stormwater back into the ground, preventing overflows and reducing reliance on treatment centers. Chicago’s existing green infrastructure, including its green alleys, diverted about 70 million gallons of stormwater from treatment facilities in 2009, according to the report.
I can attest to the existing strains on the sewer/storm runoff system in Chicago; we live just off of a main north-south surface street, and after a heavy rain like last night’s there are substantial pools of water backed up onto the street around several of the storm drains (my neighborhood hasn’t had our alleys repaved yet). Moreover, this runoff frequently overflows from the sewer system into Lake Michigan, leading to beach closures on the days following rainstorms. I could channel my inner John Whitehead to do a travel-cost estimate of the value of the lost recreation, which reinforces the value of permeable concrete. One thing we don’t know yet, though, is if it’s as durable as traditional concrete, or if it depreciates more quickly.
All of this reminds me that I have to get the KP Spouse moving on that rain barrel …