Porous Asphalt (PA) pavements are an increasingly adopted tool in the green stormwater infrastructure toolbox to manage stormwater in urbanized watersheds across the United States. This technology has seen particular interest in western Washington State, where permeable pavements are recognized as an approved best management practice per the National Pollutant Discharge Elimination System (NPDES) municipal stormwater permit. Stormwater effluent concentrations from six PA cells were compared with runoff concentrations from three standard impervious asphalt cells to quantify pollutant removal efficiencies by porous asphalt systems. Additionally, the effects of maintenance and pavement age on pollutant removal efficiencies were examined. Twelve natural and artificial storms were examined over a five-year period. Street dirt and pollutant spikes were added to the pavements prior to some storm events to simulate high loading conditions. Results from this work show that porous asphalt pavements are highly efficient at removing particulate pollutants, specifically coarse sediments (98.7%), total Pb ( 98.4%), total Zn (97.8%), and total suspended solids (93.4%). Dissolved metals and Polycyclic Aromatic Hydrocarbons (PAH) were not significantly removed. Removal efficiencies for total Pb, total Zn, motor oil, and diesel H. improved with the age of the system. Annual maintenance of the pavements with a regenerative air street sweeper did not yield significant pollutant removal efficiency differences between maintained and unmaintained PA cells.
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