A new guide from the Center for Neighborhood Technology, a Chicago-based think tank, seeks to shed some light on what has been a murky area: defining the value of using green infrastructure to manage stormwater and sewer systems versus traditional gray tunnels and reservoirs.

“The Value of Green Infrastructure” guide, the culmination of a research effort that was funded in part by the Environmental Protection Agency and the non-profit clean-water advocacy group American Rivers, is designed to fill an information gap that some sources say has hampered the widespread adoption of green infrastructure practices in cities across the United States.

“Establishing a framework for calculating the benefits of green infrastructure is a first, key step in making it a mainstream practice,” says Danielle Galet, infrastructure strategist at CNT and one of the principal authors of the guide.

Green infrastructure includes green roofs, rain gardens, bioswales, infiltration trenches and permeable pavement and is being used increasingly by municipalities as a component of their water management systems. For example, Chicago, Indianapolis, Philadelphia, Seattle, Portland, Ore; and others have incorporated at least some green infrastructure components into their water systems. But some say many communities have not fully embraced the concept because of a lack of hard data quantifying the full benefits.

Galet says most communities do not consider all the benefits of green infrastructure—including energy savings, less polluted stormwater runoff and reduced greenhouse-gas emissions—when performing cost-benefit analyses to determine the approach they should take. The benefits go above and beyond the basic storwmater control benefits, which are assumed to be equal to a similar investment in gray infrastructure, she adds.

The guide includes equations designed to help municipalities put in data specific to their communities to determine the value and benefits of building green.

“When you can assign economic value to the wide array of green infrastructure benefits, [then] planners, builders and city officials can accurately evaluate the advantages of these approaches for managing stormwater in their communities,” Galet says.

“I’d say it’s a good tool—definitely not overly simplistic—that summarizes a quality methodology for how to value green infrastructure,” says Stephan Laroque, a principal economist with Omaha, Neb.-based HDR.

Betsy Otto, vice president for conservation and strategic partnerships at American Rivers, says the guide should be helpful to municipalities in deciding “where, when and to what extent green infrastructure practice should be incorporated into their planning.”

Just the Beginning

Galet acknowledges that the guide is a starting point. It probably underestimates some of the benefits, such as community livability and reduction of the heat-island effect, Galet says, and more real-world research is needed.

“This is a very strong beginning framework. Now we want to take it out in the field and start tweaking it based off” input from communities, she says.

Brian Marengo, principal water technologist at the Philadelphia offices of Englewood, Colo.-based CH2M Hill, agrees that the best information will come from experience. “The more real-world examples we get, the more apparent the benefits will become,” he says.