Bedrock Hydrogeology at High Park

Oak Ridges Moraine Groundwater Program

High Park Fact Sheet


*Figure 1: Location of High Park* Figure 1: Location of High Park

As part of a stormwater management project in High Park in 2003 , the City of Toronto was decommissioning two flowing wells that were first drilled in 1959. The flowing wells were found during construction work on the existing stormwater ponds located in the northeast corner of High Park (Figures 1, 2 and 3). Well records for the deepest well indicated that bedrock had not been encountered when the well was terminated at a depth of 38.4 m below ground surface (mbgs; 126 ft bgs). Based on this, as well as on previous investigations (e.g. Eyles, 1987; Eyles et al., 1993; Gill and Greenhouse, 1996; Lewis and Sly, 1971; Rogers et al., 1961; Sharpe, 1980; Watt, 1968; White and Karrow, 1971) it was suspected that one of the main outlets of the Laurentian River (Figure 4), a significant pre-glacial bedrock valley, was located in the vicinity of High Park. Because there are few high-quality boreholes within the City of Toronto, the ORMGP study (formerly YPDT-CAMC), sought to fill this data gap by drilling a high-quality continuously cored borehole in this valley feature.

Figure 5 shows the interpreted bedrock topography across the program study area. It has been constructed utilizing all of the existing boreholes in the database that have progressed through the glacial sediments to intersect bedrock. The Laurentian Channel is thought to connect Georgian Bay to Lake Ontario and may be a significant conductor of groundwater on a regional scale. The main channel has been traced north to Nobleton, continuing northward trending west of Barrie, and up into Georgian Bay with tributaries extending as far west as the Niagara Escarpment near Caledon East. The High Park monitoring location is shown to be situated coincident with the interpreted west branch of the Laurentian Channel in the Toronto area. The detailed bedrock in the Toronto area is being re-interpreted based on newly drilled boreholes in the Toronto area.

Details regarding the sediment stratigraphy within the Laurentian valley and groundwater movement within the feature remain sketchy despite the valley having been known for over 100 years (Spencer, 1881; 1890). These details are collected and incorporated into the latest interpretation as data becomes available.

*Figure 2: High Park Area of Toronto* Figure 2: High Park Area of Toronto

*Figure 3: Northeast Corner of Hight Park* Figure 3: Northeast corner of High Park

*Figure 4: Laurentian River* Figure 4: Interpreted Laurentian river system (Figure from Coleman, 1922)

*Figure 5: Interpreted Bedrock* Figure 5: Interpreted bedrock topography for south central Ontario

A summary of events and conditions at the site is as follows:

*Figure 6: Drill Crew* Figure 6: All-Terrain drilling crew working on BH1, July 2003 (Photo by S. Holysh)

*Figure 7: Cross Section* Figure 7: West-East cross section along Bloor Street)

*Figure 8: High Park Borehole* Figure 8: High Park BH1 & PW1 geologic profile showing well installations