Sometimes, the best way to solve a problem is not to start from scratch but instead make the most of what you already have.

Manufacturers know it, and process optimization is one way they have improved productivity on the factory floor. Today, communities are learning the same lesson, with infrastructure optimization becoming an economical and effective way to address flooding and water quality issues created by stormwater runoff.

But how exactly do you optimize infrastructure? 

Consider how combined sewer overflows (CSOs), flash flooding and other runoff issues have been addressed historically. To comply with CSO regulatory guidelines, cities have invested millions, sometimes billions, of dollars in the construction of stormwater-only pipe, large tunnels, high-rate treatment facilities and major plant improvements. On the private side, developers are required to install detention basins and other stormwater storage facilities to collect and slowly release the stormwater peaks associated with major 10-year storm events. These single-purpose basins take up significant space and, for smaller rain events, offer little or no benefit.

Looking ahead, public and private groups can continue adding more stormwater storage capacity this way. But what if they instead retrofitted existing infrastructure to deliver increased flood protection or reduce CSOs — at a fraction of the cost?

That is now happening in some cases thanks to newer, more holistic approaches to watershed management. We now focus more attention on how water is captured and conveyed through a watershed. We then look for technologies we can use to create an intelligent system that mimics the natural ecosystem, while also creating more resilient stormwater infrastructure.

For example, we have begun to use data-driven technologies such as Continuous Monitoring and Adaptive Control (CMAC) that make it possible to retrofit infrastructure so as to plan for, observe and respond to storm events predictively. Developed by Boston-based OptiRTC Inc., CMAC combines National Weather Service data, stormwater detention basin water levels and a smart control valve to manage runoff from minor rain events in real time, while preserving a detention basin’s flood control benefit.

A 2018 study found that the CMAC systems at one Kansas City dry detention basin captured 92 percent of the wet-weather volume over a one-year period, effectively preventing 80 percent of that volume from entering the combined system by promoting infiltration and evapotranspiration.

The benefits to adaptive control and other smart solutions go beyond regulatory compliance. The attenuation of peak flows can minimize erosion in creeks that might otherwise experience frequent flash flooding. When equipped with CMAC systems, new detention basins often can be sized with a smaller footprint than what otherwise might be required.

CMAC — like other solutions — won’t work for every basin. Screening evaluations are needed to determine which basins would be appropriate candidates for retrofits.

Either way, they’re worth considering because the cost savings can be significant. The total cost for a CMAC retrofit, including system design and construction, is typically $150,000 or less, compared to the millions of dollars it can cost to construct a new detention basin.

And CMAC is just one of many new smart alternatives. The point is that if we look at watershed management holistically, we will find more ways to recreate Mother Nature’s own best practices. And it might save time and money while also providing greater public benefit.


Aging stormwater systems are struggling to keep up with an increase in significant rain events. Learn how regulatory requirements are addressing this and encouraging communities to invest in stormwater infrastructure management.

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Jason Garder, PE, ENV SP, is a senior environmental engineer with Burns & McDonnell. He focuses on stormwater, conveyance, collection system, site, green infrastructure and real-time control system design.