Knowledge Bank

Bioswales are integral landscape features that concentrate, collect, and remove sediment, pollutants, and debris from surface runoff water. They are particularly beneficial in the areas of stormwater management/filtration and groundwater recharge. According to the US Geological Survey (USGS), stormwater runoff causes issues as it picks up pollutants including sediment, nutrients from lawn fertilizers, bacteria from animal and human waste, pesticides from lawn and garden chemicals, metals from rooftops and roadways, and petroleum by-products from leaking vehicles. While bioswales are a useful low-impact method of filtering these pollutants from the water and reducing its rate of flow, improper maintenance often decreases their efficiency. Most notably, the accumulation of large sediments and trash reduces a bioswale’s ability to filter contaminants. In their Operation and Maintenance of Green Infrastructure Receiving Runoff from Roads and Parking Lots Technical Memorandum, the EPA cites construction activities, unvegetated area erosion, and winter sand application as common sources of sediment in urban runoff. In the memorandum they also explain how sediment accumulates on impervious surfaces and, when routed to bioretention areas, builds up at inlets, clogs soil, and smothers plants. To help resolve these issues, concrete curb faces can be altered to collect more substantial amounts of urban sediment. Additionally, altered curb faces aid in reducing the speed of stormwater runoff, ultimately reducing strain placed on existing stormwater management infrastructure.

This project focused on designing, modeling, and testing concrete curb and apron alteration patterns to determine which would be the most effective in filtering stormwater runoff. Designs were evaluated on site based on turbidity values recorded at the beginning and end of each trial, visual cleanliness, and efficiency over multiple trials. Models that performed well in these three categories were chosen to move on to the next “round” of testing. Curb and apron designs were each evaluated separately and combined once past the initial round of tests. This process continued, with the most effective models moving forward with each round until three designs remained.

Data from tests are still being processed, but initial results are proving the curb designs to be effective in sediment collection. The research team has applied for a provisional patent on the design and is seeking further funding to conduct more tests and eventually implement designs on a streetscape.