Changes

===Water Quality===

===Water Quality===

[[File:TSS - permeable pavement.JPG|200px|thumb]]

[[File:Permeable_pavement_TSS.png|200px|thumb]]

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].<br>

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].<br>

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[[File:TP - permeable pavement.JPG|200px|thumb]]

[[File:Permeable_pavement_TP.png|200px|thumb]]

The two box plot figures to the right show combined stormwater effluent quality results from STEP monitoring projects conducted over a 12-year time period (between 2005 and 2017) at sites within Greater Toronto Area (GTA) municipalities.  Total Suspended Solid (TSS) effluent concentration results for permeable pavement practices represent the combined results from 4 sites in the GTA and a total of 296 monitored storm events.  Median TSS concentration was found to be 8.95 mg/L and exceeded the Canadian Water Quality Guideline of 30 mg/L (CCME, 2002<ref>Canadian Council of Ministers of the Environment (CCME). 2002. Canadian water quality guidelines for the protection of aquatic life: Total particulate matter. In: Canadian Environmental Quality Guidelines, Canadian Council of Ministers of the Environment, Winnipeg</ref>) during only 12% of the 296 monitored storm events.  Median TP concentration was found to be 0.04 mg/L and exceeded the Ontario Provincial Water Quality Objective (PWQO) of 0.03 mg/L (OMOEE, 1994<ref>Ontario Ministry of Environment and Energy (OMOEE), 1994. Policies, Guidelines and Provincial Water Quality Objectives of the Ministry of Environment and Energy. Queen’s Printer for Ontario. Toronto, ON.</ref>) during 62% of the 300 monitored storm events.  In comparison, median TP effluent concentration for permeable pavements in the International Stormwater BMP Database was found to be 0.100 mg/L, based on 447 monitored storm events (Clary et al. 2020)<ref>Clary, J., Jones, J., Leisenring, M., Hobson, P., Strecker, E. 2020. International Stormwater BMP Database: 2020 Summary Statistics. The Water Research Foundation. [https://www.waterrf.org/system/files/resource/2020-11/DRPT-4968_0.pdf</ref>, which is also above the Ontario PWQO of 0.03 mg/L.  These results indicate that the design of permeable pavements draining to phosphorus-limited receiving waterbodies should include practices or design variations to improve [[Phosphorus]] retention. This could involve including a media filter manufactured treatment device as part of the treatment train design. An example of a design variation to improve phosphorus retention is including an additive to the permeable pavement base aggregate layer to improve phosphorus retention (Ostrom and Davis, 2019)<ref>Ostrom, T.K. and Davis, A.P. 2019. Evaluation of an enhanced treatment media and permeable pavement base to remove stormwater nitrogen, phosphorus, and metals under simulated rainfall. Water research, 166, p.115071.</ref>.<br>

The two box plot figures to the right show combined stormwater effluent quality results from STEP monitoring projects conducted over a 12-year time period (between 2005 and 2017) at sites within Greater Toronto Area (GTA) municipalities.  Total Suspended Solid (TSS) effluent concentration results for permeable pavement practices represent the combined results from 4 sites in the GTA and a total of 296 monitored storm events.  Median TSS concentration was found to be 8.95 mg/L and exceeded the Canadian Water Quality Guideline of 30 mg/L (CCME, 2002<ref>Canadian Council of Ministers of the Environment (CCME). 2002. Canadian water quality guidelines for the protection of aquatic life: Total particulate matter. In: Canadian Environmental Quality Guidelines, Canadian Council of Ministers of the Environment, Winnipeg</ref>) during only 12% of the 296 monitored storm events.  Median TP concentration was found to be 0.04 mg/L and exceeded the Ontario Provincial Water Quality Objective (PWQO) of 0.03 mg/L (OMOEE, 1994<ref>Ontario Ministry of Environment and Energy (OMOEE), 1994. Policies, Guidelines and Provincial Water Quality Objectives of the Ministry of Environment and Energy. Queen’s Printer for Ontario. Toronto, ON.</ref>) during 62% of the 300 monitored storm events.  In comparison, median TP effluent concentration for permeable pavements in the International Stormwater BMP Database was found to be 0.100 mg/L, based on 447 monitored storm events (Clary et al. 2020)<ref>Clary, J., Jones, J., Leisenring, M., Hobson, P., Strecker, E. 2020. International Stormwater BMP Database: 2020 Summary Statistics. The Water Research Foundation. [https://www.waterrf.org/system/files/resource/2020-11/DRPT-4968_0.pdf</ref>, which is also above the Ontario PWQO of 0.03 mg/L.  These results indicate that the design of permeable pavements draining to phosphorus-limited receiving waterbodies should include practices or design variations to improve [[Phosphorus]] retention. This could involve including a media filter manufactured treatment device as part of the treatment train design. An example of a design variation to improve phosphorus retention is including an additive to the permeable pavement base aggregate layer to improve phosphorus retention (Ostrom and Davis, 2019)<ref>Ostrom, T.K. and Davis, A.P. 2019. Evaluation of an enhanced treatment media and permeable pavement base to remove stormwater nitrogen, phosphorus, and metals under simulated rainfall. Water research, 166, p.115071.</ref>.<br>

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