We may not have long, flowing capes or wear our underwear on the outside of our pants (at least not in any offices that enforce a dress code), but civil engineers are superheroes. You heard me right. Civil engineers are superheroes, but we’re the planet-protecting kind. And, due to the lack of vengeful Kyrptonian war criminals or radioactive spider bites involved in our day-to-day lives, you may have not realized it until about four sentences ago. But don’t just take my word for it. The proof, as they say, is in the stormwater runoff. Or, more appropriately, it’s in the lack of stormwater runoff. Development Happens As undisturbed land is transformed to meet the needs of the burgeoning human population, we watch forest, field and stream give way to pavement, park and building. And when pavement replaces vegetation, the land loses its ability to keep water on-site, which means it can no longer filter it, slow it down and allow it to seep into the ground. The result is an increased amount of stormwater runoff, as well as the amount of contaminants that will flow from the site during rain events—both of which can negatively impact downstream properties and waterbodies.
To help illustrate, envision a 120-foot by 50-foot wooded plot of land—the size of a tennis court. If a storm drops three inches of rain uniformly across this area, which is the approximate amount of rain associated with a one-year storm in the Long Island area, this wooded plot of land would slow down, infiltrate and filter the vast majority of the rainwater. But what if that land were cut, cleared and paved over? If that same storm dropped the same amount of rain onto this brand new parking lot, without open areas or vegetation to slow down and infiltrate the water, almost all of it—we’re talking 1,500 cubic feet—would run off of the site and onto the downstream property. To put it into perspective, if that 1,500 cubic feet of water were converted to say, beer, it would have taken Andre the Giant (who purportedly was capable of drinking 119 12-ounce beers in one sitting) a little more than 1,005 sittings to finish all of it. Not only is that a lot of sitting, but it’s also a lot of stormwater runoff. Somebody should probably do something about that. Enter the Civil Engineer As civil engineers, we implement measures to help manage stormwater quantity and quality into our design. We use different methods—some of them sustainable—to control runoff peak rate and volume, and we incorporate features to try to remove nitrates, phosphates, suspended solids, and even heavy metals from runoff.
The end result is a developed site that more closely resembles a natural one from a stormwater perspective, which ultimately means that there will be less water and fewer contaminants leaving the site. Methods for managing stormwater can be as simple as reducing the amount of new pavement proposed for a project, or as creative as designing a stormwater wetland system to treat runoff from areas with high concentrations of pollutants. Systems can be designed to capture, store, treat and re-use runoff in building systems to help reduce utility costs, or they can be configured to infiltrate runoff into the ground to recharge aquifers. Measures can be incorporated into buildings in the form of green roofs or green walls, or into the parking lots themselves as porous pavement or paver systems.
For every stormwater runoff problem that the combined menace of impervious surfaces and storm events presents, the civil engineer can come up with an effective solution that meets the needs of the developer and works within the constraints of the site. It may not be one of the three-dimensional superpowers on display at the local multiplex this summer, but finding creative ways to manage stormwater runoff will benefit our planet, not only today, but for years to come. So, take my advice the next time you find yourself standing in the middle of a soon-to-be-developed lot on a dark and stormy night, when the lightning’s crashing and the thunder’s rolling and the rain’s coming down in sheets as thick as lead. Before the ground is paved over and the contaminants accumulate and the neighbors’ properties are flooded, go ahead and call a civil engineer. The future depends on it. Sean Callahan, P.E., LEED AP is a Senior Project Engineer for H2M’s Civil Engineering group. You can reach Sean at email@example.com.