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History of Grenadier Pond
Grenadier Pond is the largest of several ponds in High Park. Development in the surrounding drainage area has reduced its size from 19 ha in historical times to its present size of 14.2 ha.
Grenadier Pond is one of the areas within High Park that has been designated as an Area of Natural and Scientific Interest (ANSI) by the Ontario Ministry of Natural Resources based on a report by Steve Varga in 1989. According to this report "The wetland communities at Grenadier Pond are noteworthy at the local level for harbouring one of only two remaining lakefront marshes in the City of Toronto, the other being the Humber River Marshes...The remaining wetlands at Grenadier Pond should be protected as a locally significant lakefront marsh which still supports regionally rare wetland species."
Grenadier Pond is primarily fed by storm sewers and run-off from land to the west and east of the pond. To the south, the pond is separated from Lake Ontario by roadways, a railway and Sunnyside Beach. Water flows into a surface outflow at the southwest corner of Grenadier Pond to the Humber River, and then empties into Lake Ontario. Water from a pond to the west of Ellis Avenue (West Pond) also flows into Grenadier Pond approximately 30 m to the north of the outflow.
It is likely that the ponds were at one time separated from Lake Ontario by a sandbar (Wainio et al. 1976). During periods of high water (e.g., spring snow melt), Lake Ontario likely flooded over the bar, resulting in occasional flushing of the ponds and elevated water levels (Gartner Lee Ltd. 1995). The connection between Grenadier Pond and Lake Ontario was cut off in 1853 when the sandbar was widened with fill to accommodate the Grand Trunk Railway, and later widened further by road construction. The water of Grenadier Pond now drains through a sewer into the Humber River before finally reaching Lake Ontario. The outlet weir installed (after 1853) to regulate water levels in Grenadier Pond was modified in 1996 so that water levels could be lowered seasonally to mimic natural fluctuations.
In the 1880s Grenadier Pond was encircled by rich wetlands that provided an important stopover for many species of migrating birds. The shoreline consisted of cattails, sweet flag, grasses and shrubs. The south end of the pond was a sedge wetland that provided spawning ground and habitat for painted turtles, pike, salmon and largemouth bass. In the early 1900s, as the city grew around High Park and the demand for recreation on the pond increased, the marshlands shrank. In the 1950s a large section of the shoreline was dug up and replaced with turf grass stretching to a solid concrete edge. The plants and animals of the pond suffered.
Mapping sources indicate that the surface catchment area for Grenadier Pond was much larger historically (47.7 ha) than it is today (24.5 ha), and extended as far north as St. Clair Avenue. When the lands surrounding Grenadier Pond were developed, the drainage system was extensively channelized into storm sewers, and much of the runoff from hard surfaces was diverted out of the catchment. These changes have resulted in a substantial drop in the annual volume of water directed to the pond from groundwater contributions. Structurally, the pond has been “renovated” in successive waves of development, particularly on the eastern and western shorelines (Gartner Lee Ltd. 1995). Wainio et al. (1976) describe the land use changes that have occurred around the perimeter of Grenadier Pond since 1947, after which approximately 4.45 ha were filled to accommodate an expansion of the Queensway roadway.
Major efforts to rehabilitate Grenadier Pond began in 1994. These included fish stocking (Largemouth Bass and Northern Pike), water quality surveys, and the propagation of native shoreline plants at the High Park nursery. The restoration of the Grenadier Pond shoreline began in the southeast corner in 1995, and the southwest corner, East Cove and Maple Leaf shoreline in 1996. In 2005 another naturalization project extended the softened edge across the entire south shore of the pond. Shoreline plantings were implemented to enlarge the remnant areas of wetland remaining around the pond and to reduce the impact of waterfowl on the water quality of the pond (nutrient loading).
View of Grenadier Pond from south shore
The Ellis Ave./Grenadier Pond stormwater facilities were constructed in 2006. This included a wetland at the southwest corner of Grenadier Pond, with a forebay that can be dredged as needed, and oil separation devices on adjacent roads. The target is 75-80% reduction in suspended solids, as well as the heavy metals and bacteria that are associated with the solids. The changes are expected to result in cleaner water going into Grenadier Pond, more treatment of water flowing out of Grenadier before it reaches the lake, and reduced risk of flooding to adjacent properties. In 2007 additional restoration along the east shore of Grenadier Pond improved fish habitat through a series of underwater shoals, log cribs and root wads.
An Environmental Assessment study was conducted for Ellis Ave./Grenadier Pond stormwater project.
Compiled by: Karen Yukich
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