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3 solutions to help fix our stormwater woes

April 14, 2021

By Colin Haggerty

The Report Card for America’s Infrastructure gives stormwater a “D” grade

The South Platte River bisects Denver, Colorado. It passes the shadows of the Denver Broncos’ Empower Field at Mile High. It is lined by about 20 parks and has popular recreational paths enjoyed by cyclists and others.

It’s also contaminated.

At times, E. coli contamination levels in the South Platte are 137 times higher than federal safety limits. But the river is popular with tubers, kayakers, anglers, and swimmers.

The South Platte River isn’t unique. It’s simply an example of why the Report Card for America’s Infrastructure recently gave stormwater a “D” grade. Every four years, the American Society of Civil Engineers release the report card. It depicts the condition and performance of US infrastructure, assigning grades based on the physical condition and needed investments.

Overall, America’s infrastructure received a C-. While solemn teenagers might claim that’s a “passing grade”, it really isn’t where it should be for our roads, airports, schools, water systems, and more.

The South Platte River flows through Denver, Colorado. The river, like many across the US, is often contaminated by E. coli from surface runoff.

The 2021 report is the first time that stormwater appears on the Report Card. As a former President of the Colorado Section of the American Society of Civil Engineers, I understand the challenges of finding funding for all our infrastructure projects. But even then, the nationwide D for stormwater is troubling.

Naturally, I’m excited to see stormwater needs recognized. What’s unique about stormwater is the variability of storm events from year to year and even season to season.

Urban flooding results in $9 billion in damages annually. As our urban areas continue to grow, it only emphasizes the need to prioritize stormwater system upgrades. Denver is one of the most paved-over cities in the US, with nearly 50% of land within the city paved or built over contributing to the detriment of the quality of our receiving waters.

The impervious surfaces in most cities—coupled with larger rainfall events associated with climate change—creates more challenges. Like in many cities, the South Platte River’s E. coli issues are mostly attributable to runoff.

There are multiple ways to improve our stormwater system. Of course, it takes funding. While federal funding has increased, it averages about $250 million annually, which still leaves a growing annual funding gap of $8 billion just to comply with current regulations.

Strategic planning and the right projects can help. Here’s a look at three ways to attack stormwater’s D grade—green infrastructure, stormwater treatment, and stormwater storage.

The Blue and Green Corridors project in New Orleans takes a holistic look at stormwater management. The is a network of 3 miles of linear green infrastructure that includes bioswales, linear wetlands, and floodable parks.

Green infrastructure: Lead with the landscape

As mentioned, Denver is one of the most heavily paved cities in the US. But it’s not alone in facing stormwater challenges. From coast to coast, green infrastructure is critical to reducing stormwater problems.

Green infrastructure emphasizes using the landscape to capture and even treat stormwater. Basically, it lets nature help take care of nature.

Unlike Denver—the Mile High City—much of New Orleans, Louisiana, sits below sea level. The city is no stranger to hurricanes, heavy rainfall, and flooding.

The Blue and Green Corridors project takes a holistic look at stormwater management and basically invites water into New Orleans’ Gentilly Resilience District. But the invitation requires an understanding that the city is “Living with Water”—a new approach to water management.

The traditional approach to stormwater management has focused on collecting stormwater runoff in a pipe network and conveying it to pump stations as quickly as possible. Over the years, the City has built higher levees and improved pumping capacity. While the pumping facilities are some of the largest in the world—our Permanent Canal Closures and Pumps project is one and was profiled by the History Channel’s Project Impossible—they are still overwhelmed by large storm events. With over 60 inches of annual rainfall and the growing risks associated with climate change, sea level rise, and subsurface soil subsidence, Blue and Green Corridors is a shift in thinking.

The Blue and Green Corridors project is a network of three miles of linear green infrastructure that includes bioswales, linear wetlands, and floodable parks.

Along the streets slated as “blue corridors,” the City will construct open recreational waterways within the wide neutral grounds (medians) between vehicle travel lanes to receive and store runoff, as well as immediately relieve stress on the pumping system, allowing it to “catch up.” On an average day, the waterway functions as a recreational amenity alongside a welcoming, park-like space. During storms, it acts as strategic storage for the drainage system. 

Along the streets slated as “green corridors,” the City will construct a variety of green infrastructure practices—such as bioswales and rain gardens—to allow stormwater runoff to be stored and seep slowly back into the ground. Where possible, the project proposes road diets to reduce impervious cover, beautify the neighborhood with landscaping, calm traffic, and build complete streets for safe walking and biking.

Similarly, Denver introduced the Ultra Urban Green Infrastructure guidelines, and they continue to adjust these guidelines to help maximize the impact of stormwater management into every site. While every city is different, these seemingly small improvements all add up to enhance our stormwater quality for all receiving waters, whether it be in the mountains of Colorado or to the bayous of Louisiana. 

The Long Beach Municipal Urban Stormwater Treatment project will intercept, divert, and treat dry weather urban runoff and the first flush of rainwater runoff. In addition to treating the stormwater, the program incorporates new wetlands into the community.

Stormwater treatment: Clean it and use it

Miles of golden sand beaches—an iconic image of Southern California. Unless that photo is taken after a rainstorm. Then those beaches are covered in muck washed from community stormwater drains, into the Los Angeles River, and ultimately onto the Pacific beaches. Heal the Bay’s Beach Report Card gives most beaches in the Los Angeles region As and Bs during the dry summer months. In the wetter seasons, those grades plummet to Ds and Fs.

Why? Stormwater pollution.

The Infrastructure Report Card notes that under the National Pollutant Discharge Elimination System (NPDES) program, stormwater systems must reduce the discharge of pollutants from runoff. While improving water quality is a priority, from 2010 to 2018, the length of impaired rivers and streams increased from about 424,000 miles to more than 588,000 miles.

An innovative solution to the Los Angeles region’s stormwater challenges is the Long Beach Municipal Urban Stormwater Treatment (LB-MUST) Project. The city’s storm drain system—like most around the globe—contains bacteria, hydrocarbons, metals, and trash. By intercepting, diverting, and treating the dry weather urban runoff and the first flush of rainwater runoff, the new LB-MUST facility will reduce or eliminate pollution that would otherwise discharge into the Los Angeles River and spread onto beaches and into the ocean.

In addition to treating the stormwater, the program incorporates new wetlands into the community, which will be filled and sustained with reclaimed water from the treatment facility. Production of an alternative water supply will replace potable water for nearby park irrigation, and a visitor’s center focusing on public education as well as a LEED and Envision-certified treatment facility are part of this innovative program. The LB-MUST facility uses state-of-the-art ceramic ultrafiltration and photocatalytic technology to treat collected stormwater.

The new facility, which is under construction, has an initial capacity to treat two million gallons per day (MGD) of stormwater, with the potential to expand to treat four MGD.

These types of facilities are becoming increasingly more common as communities struggle with how to efficiently treat stormwater before discharging. Seattle Public Utilities is prepping to kick off their own version with the South Park Water Quality Facility Project that will treat stormwater from the South Park neighborhood before discharging to the Duwamish River. Even the City and County of Denver are now piloting the use of UV treatment to mitigate E. coli and other contaminants before discharge.

Urban flooding results in $9 billion in damages annually. As our urban areas continue to grow, it only emphasizes the need to prioritize stormwater system upgrades.

Stormwater storage: A solution for combined sewer overflows

Many cities have combined sewer systems, which collect stormwater runoff along with sewage and wastewater from homes and businesses within the same pipe network. The systems send the rainwater and sewage to treatment plants.

And they work great most of the time.

The problems come up during intense storms. During heavy rain, water levels can surpass the capability of the sewers or treatment plants. When that happens, the system gets overwhelmed and the flow needs somewhere to go—which often is directly into local streams and rivers. It creates a combined-sewer overflow—it’s unpleasant and unhealthy for the environment and people.

One solution is storing the stormwater until the rainfall event passes.

In 2020, the Ottawa Combined Sewage Storage Tunnel opened, improving the City’s ability to handle large storms. The system’s two tunnels add 1.5 million cubic feet—about 18 Olympic-sized swimming pools—of storage to Ottawa’s sewage capacity. Once the wet weather event is over, the combined sewage is treated as normal.

It really is that simple.

But combined sewage storage tunnels (CSST) offer additional benefits. Many stormwater systems in the US are at or beyond their intended lifespan. Of course, upgrading large networks of aging systems that are under our streets is a costly challenge.

A CSST can improve operational flexibility and redundancy of existing sewers by providing relief to older systems. Without a backup, sewer systems must be bypassed during inspection, which is expensive and disruptive. A CSST provides an additional route or backup for some existing major collector sewers. With a CSST in operation, the ability to inspect and repair older infrastructure connected to the system is easier.

The Ottawa Combined Sewage Storage Tunnel helps protect the Ottawa River from combined-sewer overflows, improving the city’s ability to handle large storms.

Challenges to improving our grade

Our urban areas will continue to grow, so replumbing our stormwater infrastructure is critical to protect our communities from costly urban flooding and improve water quality. We see that a combination of gray, green, and natural infrastructure works best.

The challenges we face are many: Few dedicated funding sources, complicated governance structures, aging assets, stringent water quality regulations, and climate change. And that helps explain our D grade. But there is hope—whether it’s a unique approach to living with water in New Orleans, Long Beach’s new facility that will clean and reuse stormwater, or finding ways to store combined sewage overflow.

We don’t all see the impacts of stormwater problems—the South Platte River in my backyard is a perfect example—but we are impacted. Now that stormwater has a place on the Report Card for America’s Infrastructure, we have four years to improve our grade.

  • Colin Haggerty

    As wet weather sector lead, Colin maximizes client access to our stormwater, flood control, stream restoration, and water quality experts. He’s helped restore several waterways, develop stormwater quality systems, and implement stormwater conveyance.

    Contact Colin
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