Stormwater Treatment Train

March 2, 2012

When Jean Baptiste Point du Sable built his farm as the first white settler of Chicago, IL, he never knew the Des Plaines River was a river. Because, back then, in the 1780s, it really wasn’t. He would have thought of it as a swamp.

The interplay of landscape and rain was entirely different in that day. And most Midwestern creeks and rivers that we now see on our maps–that we drive across on bridges–simply had no defined channels and banks. Pioneers slogged through them with wagons and oxen. They were not rivers as we know them today.

That was the conclusion of a hydrology study done in the early 1990s by Steve Apfelbaum of Applied Ecological Services (AES) and Dr. Luna Leopold. Their study of the Des Plaines River was based on historic data in the land survey records of the US General Land Office. And it has had an impact translating to billions of dollars in today’s American cities.

The conclusion of the study is that natural landscapes managed stormwater through infiltration and evapotranspiration (read: green infrastructure, or Stormwater Treatment Train) far more effectively than today’s urban grey infrastructure. The ultimate ramification is that restoration of green infrastructure systems can be far more cost-effective than grey infrastructure and provide multiple ecological and cultural benefits that would be otherwise forfeited.

Scientific Study: Des Plaines River Watershed

The Des Plaines River was chosen as a study watershed because of available historical data and trackable changes in watershed land uses. The river originates in southeastern Wisconsin and flows south for more than 90 river miles through agricultural, suburban, and urban landscapes through northeastern Illinois–directly through the Chicago metropolitan area. The studied watershed at the gauge station in present-day Riverside, IL, drains 620 square miles, and its eventual outlet is the Illinois River, which flows to the Mississippi River.

River flow data were collected from 1886 to 1904 due to a conflict that led to an Illinois Supreme Court case dealing with the question of whether it was in fact a navigable river. These data were compared with discharge rates from 1943 to 1990. In the late 1800s, about 40% of the watershed had been tilled or developed, contrasted with 70 to 80% of the watershed being altered by the early 1990s.

Data showed that flow rates had increased 250 to 400 times in that timeframe, and that from 1886 to 1904, for an average of 92 days per year, the system had no measurable discharge. In addition, for an additional 117 days per year, the “river” had a discharge of only 60 cubic feet per second, and equated to a depth of less than 3 inches at Riverside.

Based on these statistics, the Apfelbaum/Leopold study concluded that for over 60% of the year, the 400,000-acre watershed yielded no water or had such low flows that navigation was not possible or reliable. For another 10 to 25% of the year, the river was covered with ice.

Scientific Results: Stormwater Treatment Train

The Des Plaines River study and subsequent on-the-ground demonstrations have led to the proliferation of the Stormwater Treatment Train (STT) concept developed by Apfelbaum and his firm, AES, in the mid-1990s. One of the earliest projects, and perhaps the most acclaimed, where AES used the STT concept was the Prairie Crossing development in Grayslake, IL. Prairie Crossing is a 677-acre mixed-use residential/commercial development in the suburban Chicago area designed with more than 70% open space. Open space was designed as restored prairie and wetland with the intent of providing excellent water quality to downstream receiving waters, including the Liberty Prairie Reserve and the Des Plaines River.

Stormwater management at Prairie Crossing, and many other similar projects, utilizes upland prairie vegetation to infiltrate stormwater. These landscapes improve dramatically over time as they develop deep absorbent root systems that provide spongy soil conditions. Phosphorus is removed and sediments are trapped in the prairie landscapes as an additional benefit to infiltration and stormwater volume management.

Stormwater that flows out of these prairie areas, whether as sheet flow or directed through bioswales vegetated with native species, will eventually reach restored wetland areas where nitrogen is removed through aerobic and anaerobic processes. Finally, at Prairie Crossing, the water that reaches the created lakes in the development (read: detention ponds) is fishable and swimmable. In fact, the water that reaches Lake Aldo Leopold is clean enough to support a rare community of endangered non-game fish that most natural lakes in Illinois cannot harbor.

Evolution of the Stormwater Treatment Train

Mike Sands, Ph.D., ecologist and environmental team leader at Prairie Crossing, has conducted dozens of environmental studies documenting the water quality and ecological benefits of the Stormwater Treatment Train in his neighborhood. The endangered species fish restocking program at Lake Aldo Leopold is just one example. But he also initiated a rain garden program to strengthen the “source control” aspect of the STT concept. According to hydrologist Doug Eppich, Ph.D., P.E., of AES, who helped Apfelbaum develop the concept, this is indicative of the evolution of its functionality.

“For years the focus of stormwater management by the engineering community was for flood control,” says Eppich. “Water quality wasn’t really part of the equation. So you designed for the 100-year storm.

“When we developed the Stormwater Treatment Train, the emphasis was toward the minor, very frequent storm events, using natural ecological systems for both water-quantity and -quality improvements. We understood that natural systems were stingy–that they held onto the water rather than dispensing it to lower elevations. And we understood the value of source control, but that was a difficult issue at the start.

“Today, the STT projects I’ve been involved with are incorporating source control much more, which I think has been the most important evolution in the concept. You want to hold the rainwater where it falls. So infiltration basins, rain gardens, green roofs, pervious paving, and such are important for that aspect.”

Site-specific tests throughout the US have shown that such source control techniques have tremendous potential for water-quality improvement, flood control, groundwater recharge, and other benefits. In a Burnsville, MN, experiment, for example, rain gardens were established in one neighborhood–one rain garden per every other home–while none was built in a nearby neighborhood. Stormwater runoff was monitored in before-and-after conditions, with results showing a 90% reduction in runoff within the rain garden neighborhood as compared to the conventional neighborhood.

Not incidentally, these green techniques are considerably less expensive than their grey counterparts. A rain garden is estimated to be one-quarter the cost of a buried concrete stormwater storage vault. And there are other positive aspects. In Philadelphia, when vacant lot landscapes in the New Kensington community development were converted to green infrastructure, property values increased significantly. Additionally, many public officials believe the job creation opportunities inherent in a green infrastructure framework are massive, and basically unexplored.

Big Picture STT

Site-specific STT is now proven to benefit water quality in downstream waters, but could there be area-wide benefits for applying the concept to large metropolitan areas–where most of us live?

In fact, yes. And it is coming to fruition in several areas–where mometro areas that are initiating green infrastructure programs with important stormwater management benefits.

In advocating for natural resource protection and conservation master planning for the City of Chisago, MN, AES principal ecologist Kim Chapman wrote in 2006: “A functional conservation system includes a region-wide approach to stormwater management. In this approach, new stormwater storage and conveyance systems are minimized (as is cost), Best Management Practices are employed, and a multi-purpose, regional system for managing surface runoff is designed that is expected to meet and exceed water quality and quantity standards. In addition, the regional stormwater management system provides opportunities for a wide-ranging trail system, and habitat connections between important natural areas and buffers along streams, ponds, lakes, and wetlands. This approach benefits the quality of all surface waters.”

One early attempt to scale up the concepts and conservation values of the STT was sponsored in the Kansas City metro area by the Mid-America Regional Council (MARC), with funding from USEPA. MARC worked closely with AES to inventory all natural resources in the 3,000-square-mile Kansas City metro area. With GIS modeling and field studies to validate and calibrate the modeling, the natural resources inventory was then used to create an objective method for prioritizing areas for inclusion in a green infrastructure plan.

“This information is being applied in various planning contexts including MetroGreen, a plan for 1,144 miles of interconnected public and private open spaces, greenways, and trails designed to link our nine counties,” says Tom Jacobs, MARC’s environmental program director. “Other uses include watershed and stormwater management, transportation planning, and land-use planning for new developments and redevelopment.”

STTs for CSO Reduction

A major incentive for many metro regions is to use STT concepts to reduce or eliminate the dreaded combined sewer overflows (CSOs) that plague more than 700 communities with combined storm and sanitary sewers. But of course, there are multiple benefits to green infrastructure programs–Leave No Child Inside and others–and significant funding is being directed toward these programs.

One of the leaders in this movement is the Milwaukee Metropolitan Sewerage District (MMSD), which launched its Greenseams program in 2001. The goal of the long-term project was to identify, protect, acquire, and restore open spaces in the upland areas that drain into downtown Milwaukee and Lake Michigan. Three different watersheds collide in downtown Milwaukee, and a decade ago, MMSD leaders concurred that upland drainage areas were critical to reducing flooding and CSOs and to improving water quality in Lake Michigan.

Kevin Shafer, P.E., executive director of MMSD and chair of the Urban Water Sustainability Council, spoke recently at the Urban Water Sustainability Leadership Conference of the Clean Water America Alliance. A major focus of the event in Milwaukee was to illustrate how metropolitan areas are embracing green infrastructure and increasingly integrating their grey infrastructure with green systems for infiltration and wetland detention to keep stormwater out of their sewerage systems. Shafer highlighted the Milwaukee region’s green infrastructure efforts such as its green roof program, rain barrel and rain garden programs, and public reporting on its green efforts through its website.

Shafer reported that in the last decade, MMSD has worked with The Conservation Fund (TCF) to purchase more than 2,300 acres for infiltration and reduction of nonpoint-source pollution. Objectives, he said, were not only for flood reduction, but also for water-quality improvement and open space preservation. For this conservation plan, AES teamed with TCF to design and evaluate STTs that helped prioritize and target properties that have subsequently been acquired by the Greenseams program.

MMSD is also engaged in projects to remove 1960s-era concrete lining in streams and replacing the channels with meandering naturalized channels, including riparian wetlands and prairie buffers that will provide for STT functionality.

“This region was designated a Global Compact City (for water) by the United Nations, and we won a leadership award for an ongoing commitment to addressing stormwater impacts through green infrastructure by the Great Lakes and St. Lawrence Cities Initiative,” says Shafer. “What we’ve learned through the years is that regional collaboration is absolutely key to protecting and conserving water resources. We’ve got 28 member communities, and we do nothing alone.”

Cleveland, OH, has embarked on a similar green infrastructure program designed to control discharges of untreated wastewater into the Cuyahoga River and Lake Erie–annual discharges on average of 5 billion gallons a year in the Northeast Ohio Regional Sewer District. The district plans to spend $42 million in the next eight years on neighborhood “green” projects that include partnerships with the city’s redevelopment efforts as well as projects that will be fully funded and operated by the district.

District officials want to transform 1,000 acres of unused highly impervious urban landscape–parking lots, roadways, and abandoned buildings–into green spaces designed to capture and clean stormwater naturally and keep it out of the sewer system.

In Cleveland, the 81-square-mile CSO area is more than 80% impervious, according to Kellie Rotunno, the district’s director of engineering and construction, and it generates 36 billion gallons of stormwater runoff annually.

The district’s original 25-year plan had centered on spending nearly $3 billion to engineer and build seven massive underground tunnels to store combined storm and sanitary water until it could be pumped back to the surface and processed in a wastewater treatment plant. Now, however, these grey construction projects may be swapped, in part, for green ones, depending on the success of projects in Cleveland and other cities within the district.

“All in all, we’re pretty excited to have $42 million to spend on green infrastructure projects around Cleveland,” says Rotunno. “It’s going to take a lot of little green pieces, and fitting them all together to get the results we need. The key is to repurpose vacant land–to redevelop properties in blighted neighborhoods as green infrastructure in partnership with neighborhood revitalization efforts, which will provide multiple benefits.”

The Cleveland vision is akin to a vision developed by the Philadelphia Water Department. Both are aimed at multiple goals. Not only are they directed toward goals for flood reduction, water quality, open space, recreation, and urban wildlife ecology, but they also have important cultural and education components.

Philadelphia has embarked on what appears to be the nation’s most aggressive green infrastructure program to manage its combined sewer overflows of approximately 13.5 billion gallons a year. Philadelphia intends to reduce those discharges by 7 billion gallons in the next 25 years with an investment of $2.5 billion in improvements–about 70% of them being green infrastructure projects.

 Instead of an expensive, invisible deep-tunnel solution, the green infrastructure projects envisioned by Marc Cammarata, director of the Philadelphia Water Department Office of Watersheds, are aboveground, visible, and aesthetically pleasing, and they can improve property values.

“There are even studies linking it to crime reduction,” he adds. “I think the key here is we have a huge opportunity to give something back to the ratepayers.”

Apfelbaum, one of the authors of the STT nearly 20 years ago, shakes his head and smiles in amazement. “Who would have thought the concepts of managing rain where it falls would bring about a reduction in urban criminal activity? It shows how healthy natural areas truly affect the quality of our lives in many important ways.”

Stormwater Parks and Stream Daylighting

As a theme for urban parklands, stormwater is becoming a rock star. Saylor Grove is a 3.25-acre park within Philadelphia’s renowned Fairmount Park system. In 2006, the Philadelphia Water Department constructed a 0.70-acre stormwater treatment wetland in the park to address the impact of urban runoff and bank erosion along the Monoshone Creek, a major tributary to Wissahickon Creek.

The wetland is located at the terminus of a 156-acre urbanized watershed and filters a large portion of the watershed’s approximately 70 million gallons of annual stormwater. The wetland system is designed to filter nonpoint-source pollutants and reduce the peak stormwater flow rates and volumes. Water enters the wetland from a daylighted stream that was formerly piped under the park and from stormwater that is diverted from the storm sewer system.

“While Saylor Grove is outside our CSO area, the goal, again, is to mitigate the effects of urban stormwater runoff while creating an amenity for the community at the same time,” says Cammarata.

Cincinnati is planning a similar stream daylighting strategy in its Sustainable Infrastructure program, which is an integrated watershed planning approach in response to its consent decree to reduce CSOs. The Metropolitan Sewer District (MSD) of Greater Cincinnati has evaluated numerous priority watersheds of the Lower Mill Creek. While many watersheds were found to have opportunities for source control to reduce stormwater from entering the system, one watershed in particular, Lick Run, provided an opportunity to remove natural flow and stormwater from the sewer pipe where it was diverted in 1910.

The 19-foot sewer pipe drains stormwater and sewage from a 2,800-acre area on Cincinnati’s west side. During a typical rainfall event, no drop of rain enters Mill Creek from the 2,700-acre Lick Run watershed without first going through the CSO structure. The 19-foot sewer operates as it was designed to do more than 100 years ago, but the needs and desires of the community have changed since then.

The Lick Run CSO structure allows approximately 1.7 million gallons of CSO to enter Mill Creek annually. Because of the extent of sewage overflow, USEPA ordered the district to fix the problem with a $244 million underground storage tunnel.

As an alternative, using STT concepts to emulate historic conditions, Cincinnati’s proposed daylighting of Lick Run is a $122 million project designed to reduce the flow of 800 million gallons of CSO to Mill Creek annually. The project will require the acquisition and removal of many buildings within a 6-block area.

Understanding watershed conditions and the source of our CSO problems is critical to the development of solutions,” says Mary Lynn Lodor, environmental program manager for the district. “By taking a source control approach to addressing stormwater, which is a major part of the problem, MSD can develop long-term sustainable solutions that can serve the community better and also serve as a foundation for community revitalization.

“Water quality is an important consideration to Mill Creek, which has had numerous impacts–not just CSOs but also habitat, legacy pollutants, and other causes of nonattainment. Taking a watershed-based approach, utilizing water-quality features and treatment train concepts, allows better, integrated solutions to emerge.

“We’re developing opportunities to separate and convey the flow in a hybrid grey and green bioengineered system that enables us to install a variety of features in stormwater parks. Last year, we did a cost analysis on a deep tunnel versus a three-pronged wet-weather strategy of source control, conveyance, and storage/product control. The three-pronged wet-weather strategy emerged as a more cost-effective solution–one that allows us to “˜right-size’ the grey infrastructure–and it provides a much better product for the ratepayers.”

Technical Aspects and Ecological Underpinning

AES is currently partnering with TCF to update and add scientific underpinning to the Chicago Wilderness Green Infrastructure Vision (GIV), originally drafted in 2004. One of the goals of the GIV 2.0 project, according to Will Allen, TCF director of strategic conservation, is to establish a network of interconnected “core areas” and “hubs” of well-functioning natural areas that will contribute to ecosystem services such as clean water, flood control, carbon sequestration, and recreational opportunities.

“At the regional scale, the network will provide important buffer lands that contribute to high water quality and supply,” wrote Allen. “At the site/urban scale, green infrastructure enhances neighborhoods and downtowns through environmentally sensitive site design techniques, urban forestry, and non-engineered stormwater management systems that reduce the environmental impact of dense urban settlements.”

The project is a significant GIS effort, merging the talent of AES’s and TCF’s GIS staffs with ecological science and a strong understanding of historic landscape and stormwater management conditions to reestablish a network of natural areas that provides multiple benefits. Once again, the data of the Des Plaines River study and its STT conclusions are impacting the future development and quality of life of the entire Chicago region.

Funding Through Stormwater Utilities

At the Clean Water America Alliance conference, it was noted that the establishment of stormwater utilities has risen by 45% in the past four years, with 36 states and the District of Columbia charging stormwater utility fees to their residents. Some utilities, such as that established by the City of Minneapolis, MN, in 2005, offer credits for management of stormwater quality and quantity.

Credits are typically for infiltration or detention strategies that attempt to emulate the historical landscape conditions prescribed by the Stormwater Treatment Train. Fees are also often used for projects that provide STT benefits through green infrastructure projects.


In 1993, Apfelbaum’s white paper on the Des Plaines River, “The Role of Landscapes in Stormwater Management,” led to the realization of the historic role on how healthy ecological systems managed stormwater. Apfelbaum postulated that through ecological restoration, landscapes can again manage stormwater to add water-quality benefits.

And today, nearly 20 years later, it is being demonstrated in hundreds of projects, large and small, in industrial, commercial, and residential developments; in new highway construction projects and highway retrofits; in redevelopment of urban blighted areas; and in corporate campuses and office parks. It has also been demonstrated in public parks that had previously been storm-sewered, where visitors now enjoy what they believe to be natural landscaping. They are actually STTs in disguise!

In a more recent treatise penned by Applied Ecological Services titled “Treating Water as a Precious Resource,” the authors assert, “Water is one of the most coveted and yet vilified resources on earth.” The paper documents that, in urban areas, we catch our rainwater in gutters and drains and flush it down pipes to ditches and rivers. However, during seasonal mid-summer dry spells, we enact ordinances to conserve the same water that we so readily sent to the Gulf of Mexico earlier in the year. Our contradictory relationship with water has historical roots as deep as our nation’s.

But today it seems we’re hearing accounts from throughout the country that cities and agencies that are charged with water management have gotten the message. Water is a precious resource, and it can be managed from an ecological perspective.

Green trumps grey, today. Stormwater management need not be engineered with concrete and steel. And the multiple, cumulative quality-of-life benefits available through such a scientific, ecological perspective are far superior for a society that has, in the Clean Water Act of 1972, expressed its yearning for swimmable, fishable, drinkable waters.

Stormwater Treatment Train is a trademark of Applied Ecological Services Inc. Greenseams is a trademark of the Milwaukee Metropolitan Sewerage District.
About the Author

Jack Broughton

Jack Broughton is with Applied Ecological Services in Brodhead, WI.

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