By adopting green infrastructure in place of some gray infrastructure, Kansas City reduced the total costs of managing its combined sewer system through 2040 by over $2 billion.
Cities spent decades building pipes and pumps to move water out fast. Hoboken tried absorbing it instead—and cut flooding by 88%.
The economic losses from disasters that are not covered by insurance continue to grow, but resilience projects are generating measurable positive returns.
By adopting green infrastructure in place of some gray infrastructure, Kansas City reduced the total costs of managing its combined sewer system through 2040 by over $2 billion.
American cities have been under federal order to fix their sewer systems for decades. About 700 municipalities across the U.S. operate combined sewer systems that collect both sewage and stormwater in the same lines. During heavy rain, water volume can overpower the pipes’ capacity, sending raw sewage into local waterways.
The Environmental Protection Agency (EPA) has issued 91 consent decrees (legally binding settlement agreements requiring cities to reduce sewer overflows) since 1998. The compliance path for cities has almost always been the same: build bigger pipes and deeper tunnels, at costs that can reach into the billions. Kansas City found a different way, which could become a blueprint for cities across the country.
Kansas City, Missouri, signed a consent decree in 2010, then did something no other U.S. city had done: negotiated a modification of the decree to incorporate green infrastructure—natural systems like rain gardens and drainage channels that absorb stormwater before it reaches the pipes—as a formal compliance strategy.
By adopting green infrastructure in place of some gray infrastructure (conventional pipes, tunnels, and storage basins), the amended consent decree reduced the total costs of managing the combined sewer system through 2040 by over $2 billion.
“The city's consent decree drives much of our green infrastructure work and investments," says Andy Shively, KC Water Deputy Director of Smart Sewer, Wastewater & Stormwater Engineering. "The city is required to capture combined sewer overflows, and green infrastructure is an effective tool for that purpose."
The modification to Kansas City's 2010 consent decree introduced an "adaptive management" process. The city has more flexibility to propose alternative projects that use emerging technologies and more cost-effective control measures. The result was a dramatic reduction in projected costs.
"Relying solely on traditional gray infrastructure—like massive underground storage tunnels—is incredibly expensive and provides minimal community co-benefits,” says Shively. “Green infrastructure captures and utilizes rainwater where it falls, which naturally decreases the volume of water rushing into combined sewer systems and can ultimately eliminate the need to build larger, cost-prohibitive tunnel systems." And the savings get passed on: "By investing in green infrastructure maintenance," Shively notes, "the city prevents stormwater from overloading the sewer system, which ultimately helps reduce overall system costs for all utility customers."
The EPA has since tracked 18 cities or counties that have woven green infrastructure into their consent decree compliance strategies, including Louisville, Kentucky, which projects initial savings of $40 million by substituting green infrastructure for gray, and South Bend, Indiana, which is saving more than $400 million through a hybrid gray-and-green approach.
These cities have realized that the cheapest way to comply with a federal mandate to stop flooding waterways with sewage is often to absorb water before it reaches the pipes. For municipalities facing the sticker shock of updating water infrastructure that’s overwhelmed by today’s severe storms, Shively’s advice is to “use green to reduce the cost of gray.” And "frame resilience investments as iterative and flexible. By using real-time data and continuous monitoring, you can optimize project performance over time, pivot when necessary, and reduce program expenses by hundreds of millions of dollars while still meeting regulatory requirements."
We also spoke with the city of Hoboken, where green infrastructure has reduced flooding by 88%. Read more about what Hoboken has done here in part one of our series on green infrastructure.
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56%
According to a survey of 107 asset owners and managers, 56% say they are engaging investees in conversations on physical climate risk and resilience. Of those, 76% say they’re asking corporations about their resilience/adaptation planning and capital expenditures.
Source: Responsible Investor.
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The Epicenter helps decision makers understand climate risks and discover viable resilience solutions. The Epicenter is an affiliated publication of The Resiliency Company, a 501(c)3 nonprofit dedicated to inspiring and empowering humanity to adapt to the accelerating challenges of the next 100+ years.
Cities spent decades building pipes and pumps to move water out fast. Hoboken tried absorbing it instead—and cut flooding by 88%.
The economic losses from disasters that are not covered by insurance continue to grow, but resilience projects are generating measurable positive returns.
From wildfire prevention to flash flood forecasting, better data is enabling earlier, more targeted decisions about risk
Early proof points are what eventually unlock scale, and they almost never look like proof when they begin. We need the compounding of resilience over time, and we need to recognize when the next disaster creates a narrow window for rapid investments in resilience—all at once.
