English: Bioretention / bioswale in median of Grange Avenue in Greendale, Wisconsin. Bioretention was constructed/planted in 2009 and photos taken September 2009. This photo shows a concrete flume or concrete apron used to drain stormwater runoff from the street pavement and curb into the bioretention area. There were minor amounts of erosion or sediment deposition at the bottom of these concrete flumes, where they enter the bioretention basin bottom. Later on, cobblestone was placed at the bottom of the flumes, to provide additional erosion protection.