While we didn’t know we needed it, Tom Hanks gave us a pretty comprehensive list of the different types of rain in the 1994 film, Forrest Gump. “We been through every kind of rain there is. Little bitty stingin’ rain, and big ol’ fat rain, rain that flew in sideways,” he described. But it’s not only the type of rain that can vary so greatly. Stormwater Management – that is, what we do with the stormwater runoff from rain and other precipitation as it accumulates on our streets, land, and waterways – varies between regions, states, and municipalities. Even close geographic neighbors, such as Minneapolis and Chicago, can have very different management strategies.
Joey Abramson, P.E., CFM is a Water Resources Engineer who joined the Civiltech Water Resources team in the fall of 2021 after moving from Minneapolis. After spending most of his life in the Twin Cities metropolitan area, including the last 8 in the Water Resources wing of the consulting engineering world, Joey decided to pack it up and start a new chapter in Chicago.
The three major components of everyday Stormwater Management are volume control, rate control, and water quality. Volume control is a method to reduce the total amount of stormwater runoff leaving a drainage area after a rainfall event – think a kiddie pool instead of an Olympic sized swimming pool. Rate control is reducing the flow of runoff – think a garden hose versus a fire hose. Water quality is ensuring the runoff leaving a site is clean. These three components govern most of stormwater management.
The fundamental approach to engineering projects span geographic boundaries. What is the goal of the project? Who is driving the project and who is affected by it? How do we communicate these items effectively? What are the environmental, economic, social, and logistical constraints of the project? Joey sees each engineering project as a unique opportunity to fluidly compose a solution from concept to reality. “The art of engineering involves balancing all of these constraints while at the same time making it feel like the constraints are not even there.”
Rate Control
In both Chicagoland and the Twin Cities, controlling the rate of runoff is highly important. By limiting the rate of runoff leaving a site, we can alleviate downstream flooding, erosion, and sedimentation issues that would otherwise accompany construction activities. When a new road or development proposes to increase impervious surfaces and thereby reduce the ground’s natural ability to absorb rainfall, this can cause increased stormwater runoff leaving the site. This increased runoff must be controlled to reduce the possibility of downstream impacts. A major way to achieve this is to create detention ponds, whose function is to allow the firehose of high flows to fill up a storage area – such as a pond or even underground storage chambers – that will have discharge the water at a more garden hose rate. A major difference in Chicago is that there is often less physical room to create these ponds in such a densely developed City, though that is true to an extent in the Twin Cities as well. Therefore, the mitigation for keeping rates controlled in Chicago is often applied on the front end – that is, new developments should not increase impervious surfaces.
Volume Control and Water Quality Treatment
In addition to reducing the risk of downstream flooding, controlling the volume of stormwater runoff leaving a proposed project site helps also has benefits to groundwater and the cleanliness of the runoff that does leave the site. Joey explains “in urban stormwater engineering, there is a concept of the ‘first flush’ which refers to the first amount of runoff that starts to drain into our street drains. This ‘first flush’ picks up and transports the dirt, oil, debris, and other sources of pollutants from roads, lawns, and roofs into our drainage systems.” With this in mind, regulations often require that the first flush is retained on site and allowed to infiltrate into the ground. This way, the dirty runoff gets cleaned by natural filtering through the ground, in a process called infiltration. This is the primary method of providing volume control for stormwater runoff. However, there are many conditions that do not allow for such a practice due to concerns about contaminating the groundwater.
If volume control is not an option, another major method to improve the water quality of stormwater runoff is through the use of sedimentation ponds. These permanent ponds allow for the dirty runoff to settle out before discharging downstream. Just like a pool that accumulates dirt and gets cleaned periodically, stormwater ponds get excavated and restored every decade or so to maintain their pollutant removal abilities.
Chicago’s Mystique
As a bright-eyed kid (and then college student, and then semi-adult) from Minneapolis, Joey often viewed Chicago from afar with a quiet sense of awe. Chicago is home to arguably the most iconic water resources engineering feat in US history – the reversing of the Chicago River in 1900. That one might actually be a little difficult to explain using the same kiddie pool, fire hose, etc. metaphor framework. Suffice it to say, it was an enormous civil engineering undertaking that we still benefit from today. And there are many more engineering gems that Joey enjoys about the Chicagoland area. “I miss the Twin Cities,” Joey explains, “but I am very excited for the challenges and opportunities that Chicago offers.”