Changes

The whisker plot figures to the right show combined stormwater effluent quality monitoring results from STEP monitoring projects conducted over a 25-year time period (between 1997 and 2021) at sites within Greater Toronto Area municipalities.<br>

The whisker plot figures to the right show combined stormwater effluent quality monitoring results from STEP monitoring projects conducted over a 25-year time period (between 1997 and 2021) at sites within Greater Toronto Area municipalities.<br>

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Median concentrations of Total Suspended Solids (TSS) in untreated stormwater and oil and grit separator (OGS) outlet locations were found to typically exceed 30 mg/L.  Median TSS concentrations at stormwater detention pond and chamber system outlet locations was found to be below 30 mg/L, but exceeded the guideline value in 36% of the monitored storm events.  Median TSS concentrations at bioretention, permeable pavement and infiltration trench outlet locations were found to be all below 30 mg/L.  TSS concentrations in effluent from bioretention was found to exceed 30 mg/L in only 15% of the 301 monitored storm events, and in only 12% of the 296 monitored events for permeable pavements.

Median concentrations of Total Suspended Solids (TSS) in untreated stormwater and oil and grit separator (OGS) outlet locations were found to typically exceed 30 mg/L.  Median TSS concentrations at stormwater detention pond and chamber system outlet locations was found to be below 30 mg/L, but exceeded the guideline value in 36% of the monitored storm events.  Median TSS concentrations at bioretention, permeable pavement and infiltration trench outlet locations were found to be all below 30 mg/L.  TSS concentrations in effluent from bioretention was found to exceed 30 mg/L in only 15% of the 301 monitored storm events, and in only 12% of the 296 monitored events for permeable pavements.<br>

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Median concentrations of Total Phosphorus (TP) in untreated stormwater and all stormwater facility type outlet locations were found to exceed 0.03 mg/L. Untreated stormwater was found to exceed 0.03 mg/L in between 96 to 98% of the 545 monitored storm events.  Stormwater detention pond or chamber system effluent was found to exceed 0.03 mg/L during 91% of the 211 monitored events. Effluent from bioretention outlet locations was found to exceeded 0.03 mg/L during 86% of the 355 monitored events.  Effluent from permeable pavement outlet locations exceeded 0.03 mg/L during 62% of the 300 monitored storm events.<br>

Median concentrations of Total Phosphorus (TP) in untreated stormwater and all stormwater facility type outlet locations were found to exceed 0.03 mg/L. Untreated stormwater was found to exceed 0.03 mg/L in between 96 to 98% of the 545 monitored storm events.  Stormwater detention pond or chamber system effluent was found to exceed 0.03 mg/L during 91% of the 211 monitored events. Effluent from bioretention outlet locations was found to exceeded 0.03 mg/L during 86% of the 355 monitored events.  Effluent from permeable pavement outlet locations exceeded 0.03 mg/L during 62% of the 300 monitored storm events.<br>