Permeable Pavement in the Northwestern United States: Pollution Source or Treatment Option?

Permeable pavements can be an effective stormwater mitigation technique, but there are concerns that polluted stormwater may contaminate groundwater as stormwater infiltrates through the soil beneath the pavement. This research evaluates the pollutant removal capabilities of pervious pavements using pervious cement concrete (PC) and porous asphalt concrete (PA) cylinders. Stormwater collected from an outfall was used to perform three tests. The influent and effluent were analyzed for metals, semi-volatile organic compounds (SVOCs), phosphorus, and turbidity. Average percent removal for metals were 37–63% except for zinc, which had an average export of 21% for pervious cement concrete and 52% for porous asphalt concrete. Only 10 of the SVOCs tested had an influent concentration above detection levels. Complete removal (below detection levels) was observed for benzo(a)anthracene, benzo(a)pyrene, chrysene, and indeno(1,2,3-cd) pyrene. Average removals for benzo(b)fluoranthene, benzo(g,h,i)perlyne, fluoranthene, phenanthrene, pyrene, and bis(2-ethylhexyl)phthalate were 63–96%. No significant removal was observed for total phosphorus and reactive phosphate. All contaminant concentrations were below drinking water limits except lead, which would likely be removed in the soil layer below the pavement. This study indicates permeable pavements can effectively remove stormwater contaminants and protect groundwater as a drinking water source.