In 2000, a different kind of wetland was built in the Lower Duck Pond. Its major function is to clean stormwater entering from Spring Creek. Separated from the rest of the Lower Duck Pond by a berm, the wetland contains cattails and other aquatic plants that help remove pollutants from water while providing habitat for wildlife.
Based on this model and other studies, a number of stormwater management facilities were constructed in the High Park/Ellis Avenue area in 2006 as part of the City’s Wet Weather Flow Master Plan. One of these facilities, located on the west shore of Grenadier Pond just north of the southwest cove, combines a sedimentation forebay with a wet pond/wetland area. The stormwater treated in this facility is expected to be cleansed of up to 80% of its suspended solids and associated heavy metals and bacteria before entering the pond.
In urban areas, the carrying capacities of the storm and combined sewer systems vary widely. One common factor is that the systems have difficulty handling the runoff from very infrequent and intense storms. Storm sewers are designed to intercept road drainage, through roadside catch-basins, during wet weather conditions and convey this runoff to the nearest receiving water body. However, because of the amount of impervious surface areas within urban areas, the runoff volumes and flow rates are substantially increased. In addition, wash-off from these hard-surface areas contains an enormous amount of contaminants. Area watercourses are impacted both by the physical and chemical stresses created by the flows. During dry weather, storm sewers can also be a direct source of contamination as a result of accidental or deliberate chemical spills to roadside catch-basins.
To reduce the environmental impact of storm sewer discharges, the City has embarked on a number of initiatives, including:
High Park "Jewel" brochure
WATER: STRATEGIC DIRECTIONS, City of Toronto, February 2000
See also Grenadier Pond
City of Toronto's Wet Weather Flow Management Master Plan - Environmental Assessment Study relating to Ellis Ave./Grenadier Pond projects: