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→Performance
===Water Quality===
===Water Quality===
Like other stormwater practices, the water quality performance of permeable pavements is closely tied to the reduction of runoff volumes through infiltration, However, permeable pavements are also very effective stormwater runoff filters. Most sediments and associated contaminants are trapped within the surface pores or gravel filled joints between the pavers. A five year study of three permeable pavement surfaces in Vaughan showed total suspended solids (TSS) concentration reductions between 88 and 89% [https://sustainabletechnologies.ca/app/uploads/2016/02/KPP-Ext_FinalReport_Dec2015.pdf/ (Van Seters and Drake, 2015)]. Other STEP studies in the Greater Toronto Area have displayed similar results, with only 7% of 181 permeable pavement effluent samples having TSS concentrations above 30 mg/L (median = 7 mg/L)[https://sustainabletechnologies.ca/app/uploads/2015/06/SynthesisWaterQuality_Statistics_May2015.pdf/ TRCA, 2015].
Like other stormwater practices, the water quality performance of permeable pavements is closely tied to the reduction of runoff volumes through infiltration. However, permeable pavements are also very effective stormwater runoff filters. Most sediments and associated contaminants are trapped within the surface pores or gravel filled joints between the pavers. A five year study of three permeable pavement surfaces in Vaughan showed total suspended solids (TSS) concentration reductions between 88 and 89% [https://sustainabletechnologies.ca/app/uploads/2016/02/KPP-Ext_FinalReport_Dec2015.pdf/ (Van Seters and Drake, 2015)]. Other STEP studies in the Greater Toronto Area have displayed similar results, with only 7% of 181 permeable pavement effluent samples having TSS concentrations above 30 mg/L (median = 7 mg/L)[https://sustainabletechnologies.ca/app/uploads/2015/06/SynthesisWaterQuality_Statistics_May2015.pdf/ TRCA, 2015].
Another group of studies of permeable pavements examines the quality of water infiltrated through soils beneath the installations. In these studies the quality of infiltrated water is used as a measure of the potential for contamination of groundwater. One such study of a permeable interlocking concrete pavement installed in a college parking lot in King City, Ontario, showed that stormwater infiltrated through a 60 cm granular reservoir and 1 metre of native soil had significantly lower concentrations of several typical parking lot contaminants relative to runoff from an adjacent asphalt surface [https://sustainabletechnologies.ca/app/uploads/2013/03/PP_FactsheetSept2011-compressed.pdf/ (TRCA, 2008)]. These results are consistent with research on the quality of infiltrated water from permeable pavements in Washington<ref name="example2" /> and Pennsylvannia<ref name="example1" />. As with all stormwater infiltration practices, risk of groundwater contamination from infiltration of runoff laden with road de-icing salt constituents (typically sodium and chloride) may be a concern in lands designated as source protection areas. Chloride ions are extremely mobile in the soil and are readily transported by percolating water to aquifers.
Another group of studies of permeable pavements examines the quality of water infiltrated through soils beneath the installations. In these studies the quality of infiltrated water is used as a measure of the potential for contamination of groundwater. One such study of a permeable interlocking concrete pavement installed in a college parking lot in King City, Ontario, showed that stormwater infiltrated through a 60 cm granular reservoir and 1 metre of native soil had significantly lower concentrations of several typical parking lot contaminants relative to runoff from an adjacent asphalt surface [https://sustainabletechnologies.ca/app/uploads/2013/03/PP_FactsheetSept2011-compressed.pdf/ (TRCA, 2008)]. These results are consistent with research on the quality of infiltrated water from permeable pavements in Washington<ref name="example2" /> and Pennsylvannia<ref name="example1" />. As with all stormwater infiltration practices, risk of groundwater contamination from infiltration of runoff laden with road de-icing salt constituents (typically sodium and chloride) may be a concern in lands designated as source protection areas. Chloride ions are extremely mobile in the soil and are readily transported by percolating water to aquifers.