Permeable pavements systems and tree boxes are a common type of Green Infrastructure (GI) Stormwater Control Measures (SCMs) that are often used for mitigating the stormwater runoff. In this study two permeable pavement systems and a tree box installed along parking lanes of an urban street in Louisville, KY, were investigated to evaluate their performance on improving stormwater runoff quality. The water quality monitoring was accomplished by analysis of samples collected from stormwater runoff and the captured stormwater volume at the bottom of the permeable pavements’ sub-base reservoir and by a drain gauge (lysimeter) installed in the tree box. Pollutants investigated included total suspended solids (TSS), nutrients, dissolved metals, and bacterial contamination (E. coli). The results showed that permeable pavements significantly reduced concentrations of TSS and E. coli, as well as other pollutants such as total phosphorus and ammonia. It was also observed that the pollutant removal vi efficiencies of these two permeable pavement systems were affected by rainfall characteristics such as intensity and antecedent rainfall conditions. This work suggests that to appropriately assess the beneficial water quality components of GIs, it is essential to couple the information with a comprehensive rainfall analysis. The field investigations on GI controls were followed by a large scale lab study was conducted to mimic the observed behavior within a controlled environment. A 6-ft tall pipe (column) with the same diameter as the shafts that were implemented in permeable pavements and tree boxes (18 inches) was filled with the same aggregate layers which were used in actual GI controls. Semisynthetic stormwater runoff was introduced to the column, pollutant removal mechanism of each layer of aggregates used in the GI controls was investigated.
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Assessing the water quality benefits of green infrastructure stormwater control measures.