Fines Movement from Testing Bioretention Media

Stormwater bioretention basins are designed to capture and hold water for a period of time and release over time either through infiltration into sub-soil or through underdrain pipes. However, if the fines in the engineered bioretention media are washed through the profile there is the potential of clogging the underlying soil or the stone/fabric around the underdrain pipe. To test this, an undergraduate student at the University of Georgia conducted an undergraduate research project to measure the amount of fines that would be flushed from engineered bioretention media over four water application events. The set-up used six inch PVC pipe with a column of 12 inches of engineered bioretention media and sand. Water was drip irrigated through the media and sand and captured. Captured water volumes were measured and samples of the leachate was analyzed for total solids. A second experiment included a 1 inch layer of #89 stone. The tests run for the media and sand was repeated with the #89 stone below the media and sand. After each test, like with the media and sand only, the captured water was measured and a sample collected for total solids analysis. The test with the stone also analyzed the amount of sediment trapped by the stone. This presentation will provide the attendee information gained from these experiments. Results indicate that there is more fines that can be flushed from the bioretention media mix verses that of sand. At the time of abstract submission, the research including the choker stone has not been conducted but is planned for summer 2021. The presentation will provide results gained from the experiment.