Natural Solutions: Make Your Next Sed Basin an Aquatic Biofilter

April 24, 2012

The next time you need a sedimentation basin, consider adding more benefits than just trapping eroding sediment. Instead, think about vegetating the banks and waterline with native plants that will attract interesting wildlife, add aesthetic value, green up your footprint…and save you money.

A typical landfill sedimentation basin falls short of its full potential in many ways. These basins can function better and be so much more than a dirt tank or a barren pool of murky water that allows some of the solids to settle. If aquatic, emergent, and shoreline vegetation is planted in these basins, they become living biological filters that feed off the nutrients coming in. They grow and become efficient over time. They can repair themselves, and provide homes for contaminant-eating microorganisms. Vegetation in these basins reduces erosion, allows more water to infiltrate into the ground, slows the velocity of water to allow more sediment to be removed, filters the water, and provides other values to the site. Best of all, these benefits and others give cost savings back to the landfill.

A great example of such a vegetated biofilter basin is at the Zona Rosa mixed-use development in Kansas City, MO. Though this project is capturing sediment that erodes off a commercial and residential development project, the primary function is the same as in a landfill: to trap sediment before it leaves the site and pollutes downstream water resources. The Zona Rosa system includes sediment trap plunge pools, aquatic vegetation filters, emergent plants (heads in the air, feet under water) in the shallow water shoreline zone, and basin slopes covered with native plants.

The 3-acre detention basin in the Zona Rosa development was initially built as a conventional sedimentation basin with an industrial-size floating skimmer made of PVC. Not only did it look like a mud hole (because, in fact, it was a mud hole), it provided no additional benefits and, in fact, required significantly more maintenance than a biofiltration basin. In 2005, the sed basin was converted to the existing detention basin with native plant enhancements, a unique undersized submerged outlet that allows smaller storm events to be held within the basin, and an emergency overflow to handle the 100-year storm event.

About the Author

Jason Dresma

Applied Ecological Services Ecologist Jason Dremsa provides field services for environmental projects in the Kansas region.