By Paula White and Helen Fitanides
The results are in from last month’s stormwater monitoring at our new Booker T. Anderson bioswale! We’re seeing a 50-100% reduction in diesel, motor oil, and the heavy metals copper, lead, and nickel. This is great news for Baxter Creek, which will be much cleaner now that these pollutants are being absorbed by the plants in the bioswale.
The reduction in motor oil is particularly impressive—no motor oil was detected in the outflow. As the graph shows, 1600 micrograms per liter were removed by the bioswale.
The other pollutants we monitored and tested were pyrethroids, a type of pesticide used in flea medicine and to control termites; nutrients, such as nitrates which are commonly used in fertilizers; and pesticides. These materials were not found in the inflow. We intend to continue to monitor bioswales at this site and future sites to track their effectiveness over time. So far, our results show that bioswales are very effective in treating pollutants produced by motor vehicles, and can be a practical way to treat stormwater runoff from parking lots. Moreover, bioswales and other green infrastructure projects provide multiple benefits such as food for pollinators, flooding mitigation, heat island reduction, and they are beautiful green oases.