While large-scale green infrastructure projects such as roof gardens or permeable streets are often characterized as being hugely expensive, a new study, co-authored by the American Society of Landscape Architects, American Rivers, the Water Environment Federation, and ECONorthwest, set out to compare the costs of such projects with traditional infrastructure projects.
According to Berg, in "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."
Paying particular attention to the benefits of green infrastructure projects to cities with combined sewer systems, the study found significant cost savings for early adopter communities. Furthermore, as Berg notes, "by allowing natural processes to take over the work we've been building infrastructure to handle, operations and maintenance costs also fall. The report concedes that some maintenance on green infrastructure will still be required, but that it is significantly less than what's required by traditional infrastructure."