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Performance results from a limited number of field studies indicate that subsurface stormwater infiltration practices are effective BMPs for pollutant removal <ref>Toronto and Region Conservation (TRCA). 2009. Review of the Science and Practice of Stormwater Infiltration in Cold Climates. Prepared under the Sustainable Technologies Evaluation Program (STEP). Toronto, Ontario.</ref>. These types of practices provide effective removal for many pollutants as a result of sedimentation, filtering, and soil adsorption. It is also important to note that there is a relationship between the water balance and water quality functions. If an infiltration practice infiltrates and evaporates 100% of the runoff from a site, then there is essentially no pollution leaving the site in surface runoff. Furthermore, treatment of infiltrated runoff continues to occur as it leaves the facility and moves through the native soil. The performance of perforated pipe systems would be expected to reduce pollutants in runoff in a manner similar to infiltration trenches.
Performance results from a limited number of field studies indicate that subsurface stormwater infiltration practices are effective BMPs for pollutant removal <ref>Toronto and Region Conservation (TRCA). 2009. Review of the Science and Practice of Stormwater Infiltration in Cold Climates. Prepared under the Sustainable Technologies Evaluation Program (STEP). Toronto, Ontario.</ref>. These types of practices provide effective removal for many pollutants as a result of sedimentation, filtering, and soil adsorption. It is also important to note that there is a relationship between the water balance and water quality functions. If an infiltration practice infiltrates and evaporates 100% of the runoff from a site, then there is essentially no pollution leaving the site in surface runoff. Furthermore, treatment of infiltrated runoff continues to occur as it leaves the facility and moves through the native soil. The performance of perforated pipe systems would be expected to reduce pollutants in runoff in a manner similar to infiltration trenches.
Several studies of exfiltration systems in Ontario have examined their water quality benefits. Seasonal contaminant load reductions in the order of 80% were observed for most constituents, with the exception of chloride, in the study of the system installed in a low density residential neighbourhood in Etobicoke <ref>Stormwater Assessment Monitoring and Performance (SWAMP) Program. 2002. Performance Assessment of a Swale/Perforated Pipe Stormwater Infiltration System – Toronto, Ontario. Toronto and Region Conservation Authority, Toronto, Ontario.</ref><ref name=SWAMP/>. Perforated pipe systems that incorporate grassed [[swales]] as [[pretreatment]] have been observed to reduce loads of suspended sediment, [[phosphorus]], [[nitrogen]], copper, lead and zinc in runoff flowing from the system between 75 to 90% in comparison to a similar catchment with conventional catchbasins and storm sewers <ref>J.F. Sabourin and Associates Incorporated. 1999. Research Project for the Updated
Several studies of exfiltration systems in Ontario have examined their water quality benefits. Seasonal contaminant load reductions in the order of 80% were observed for most constituents, with the exception of chloride, in the study of the system installed in a low density residential neighbourhood in Etobicoke <ref name=SWAMP2002>Stormwater Assessment Monitoring and Performance (SWAMP) Program. 2002. Performance Assessment of a Swale/Perforated Pipe Stormwater Infiltration System – Toronto, Ontario. Toronto and Region Conservation Authority, Toronto, Ontario.</ref><ref name=SWAMP/>. Perforated pipe systems that incorporate grassed [[swales]] as [[pretreatment]] have been observed to reduce loads of suspended sediment, [[phosphorus]], [[nitrogen]], copper, lead and zinc in runoff flowing from the system between 75 to 90% in comparison to a similar catchment with conventional catchbasins and storm sewers <ref>J.F. Sabourin and Associates Incorporated. 1999. Research Project for the Updated
Investigation of the Performance Evaluation of Grass Swales and Perforated Pipe
Investigation of the Performance Evaluation of Grass Swales and Perforated Pipe
Drainage Systems. Executive Summary. Prepared for the Infrastructure Management
Drainage Systems. Executive Summary. Prepared for the Infrastructure Management
Division of the City of Ottawa. Ottawa, Ontario.</ref>. The Nepean systems were shown to release significantly less pollutants than the conventional sewer system, even after 20 years of operation<ref name=Sabourin/>.
Division of the City of Ottawa. Ottawa, Ontario.</ref>. The Nepean systems were shown to release significantly less pollutants than the conventional sewer system, even after 20 years of operation<ref name=Sabourin/>.
{| class="wikitable sortable"
|+Pollutant removal efficiencies of exfiltration systems
|-
!Practice
!Location
!Lead %
!Copper %
!Zinc %
![[Total suspended solids]] (TSS) %
!Total [[Phosphorus]] %
!Total [[Nitrogen]] (TKN) %
|-
|Soakaway||Valence, France<ref>Barraud, S., Gautier, A., Bardin, J.P., Riou, V. 1999. The Impact of Intentional Stormwater Infiltration on Soil and Groundwater. Water Science and Technology. Vol.
39. No. 2. pp. 185-192.</ref>||98||-||54 - 88||-||-||-
|-
|[[Infiltration trench]]||Various<ref>ASCE
(2000)Pollutant removal efficiencies are reported as ranges because they are based on a synthesis of several performance monitoring studies that were available as of 2000.</ref>||70 - 90||70 - 90||70 - 90||70 - 90||50 - 70||40 - 70
|-
|Grass swale/perforated pipe||North York, ON<ref name=SWAMP2002/>||75||96||93||24||84||84
|-
|Grass swale/perforated pipe||Nepean, ON<ref name=Sabourin/>||- 99||66||0||81||81||72
|-
|Grass swale/perforated pipe||Nepean, ON<ref name=Sabourin/>||> 99||> 99||90||96||93||93
|}
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[[category: performance]]