Changes

As can be seen in the corresponding boxplot the mean performance removal efficiency of the OGS practices monitored are well below the suggested guideline of 30 mg/L (Canadian Water Quality Guideline (CWQG), or (background (assumed at <5 mg/L)+ 25 mg/L for short term (<24 hour) exposure) (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>; (TRCA, 2021<ref>TRCA. 2021. Spatial Patterns (2016-2020) and Temporal Trends (1966-2020) in Stream Water Quality across TRCA’s Jurisdiction Prepared by Watershed Planning and Ecosystem Science. https://trcaca.s3.ca-central-1.amazonaws.com/app/uploads/2021/10/29113334/2016-2020-SWQ-Report-v11_FINAL_AODA-FA.pdf</ref>).

As can be seen in the corresponding boxplot the mean performance removal efficiency of the OGS practices monitored are well below the suggested guideline of 30 mg/L (Canadian Water Quality Guideline (CWQG), or (background (assumed at <5 mg/L)+ 25 mg/L for short term (<24 hour) exposure) (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>; (TRCA, 2021<ref>TRCA. 2021. Spatial Patterns (2016-2020) and Temporal Trends (1966-2020) in Stream Water Quality across TRCA’s Jurisdiction Prepared by Watershed Planning and Ecosystem Science. https://trcaca.s3.ca-central-1.amazonaws.com/app/uploads/2021/10/29113334/2016-2020-SWQ-Report-v11_FINAL_AODA-FA.pdf</ref>).

The median value of the 91 samples taken was '''44.50 mg/L''' whereas the mean was '''64.60 mg/L''', with a '''61%''' guideline exceedance.  Given the age of of these practices and the dates monitoring took place, these systems will likely need major maintenance and/or rehabilitation if not full replacement, as they near the end of their working lifecycle, especially given forthcoming Ontario guidelines on removal efficiencies, set to release later in 2023 ([https://ero.ontario.ca/notice/019-4971#supporting-materials Low Impact Development Stormwater Management Guidance Manual]0.

The median value of the 91 samples taken was '''44.50 mg/L''' whereas the mean was '''64.60 mg/L''', with a '''61%''' guideline exceedance.  Given the age of of these practices and the dates monitoring took place, these systems will likely need major maintenance and/or rehabilitation if not full replacement, as they near the end of their working lifecycle, especially given forthcoming Ontario guidelines on removal efficiencies, set to release later in 2023 ([https://ero.ontario.ca/notice/019-4971#supporting-materials Low Impact Development Stormwater Management Guidance Manual]). Read more about the performance efficiency of these specific OGS installations located within TRCA's watershed here, in the following document - [https://sustainabletechnologies.ca/app/uploads/2013/03/OGS-ES.pdf Performance Assessment of Two Types of Oil & Grit Separator for SWM in Parking Lots] (SWAMP, 2004<ref>Stormwater Assessment Monitoring and Performance (SWAMP) Program. 2004. Performance Assessment of Two Types of Oil and Grit Separator for Stormwater Management in Parking Lot Applications – Markham & Toronto, Ontario. Report prepared for - Ontario Ministry of Environment, Toronto and Region Conservation Authority, Municipal Engineers Association of Ontario, and The City of Toronto. Published: July, 2004. Retrieved from: https://sustainabletechnologies.ca/app/uploads/2013/03/OGS_entire-report.pdf</ref>).

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