GTA West GTA West Corridor Planning & Environmental Assessment Study – Stage 1 Overview of Environmental Conditions and Constraint Working Paper December 2010 3. NATURAL ENVIRONMENT In order to develop a broad understanding of the natural environment features and functions within the GTA West Preliminary Study Area, relevant, regional-level1 secondary source information was collected and analysed. Secondary source information was obtained primarily from the regional-level Provincial Land Information Ontario (LIO) and Natural Resource Values Information Systems (NRVIS) databases and was augmented with regional-level information from other sources (i.e., municipalities and conservation authorities), as available. The collection and analysis of secondary source information should be seen as the first step in the overall study process. Each subsequent stage builds upon the information and decisions of the preceding step. Therefore, the regional-level information collected during this step of the EA process will be carried forward to subsequent steps of the process, where it will be refined and augmented with more detailed information as needed for evaluating and selecting a preferred Area Transportation System Planning Alternative (Transportation Development Strategy), as well as for the Preliminary Planning Alternative phase. The collection and analysis of secondary source information is a dynamic process. This section will be refined as information is collected. Input will be received from and shared with the public, stakeholders, municipalities and regulatory agencies as new information becomes available. 3.1 PHYSIOGRAPHY AND LANDSCAPE The physical landscape of the Preliminary Study Area is complex and encompasses portions of seven main physiographic regions. The most well-known, the Niagara Escarpment, divides the Preliminary Study Area into two distinct areas. 3.1.1 Niagara Escarpment The Niagara Escarpment is essentially a ridge of durable cap rock over comparatively soft and extensively fractured shale and sandstones several hundred metres high in some locations. The Niagara Escarpment crosses through the middle of the Preliminary Study Area as shown on Exhibit 3-20. Through the Preliminary Study Area, the Escarpment is covered by thin till with many exposures of dolomite and shale rock cliffs visible above highly-eroded long lower slopes and is cut by numerous watercourses (e.g., Credit River). 1 Regional-level refers to information that is available and comparable across the Preliminary Study Area 17 GTA West GTA West Corridor Planning & Environmental Assessment Study – Stage 1 Overview of Environmental Conditions and Constraint Working Paper December 2010 3.1.2 West of the Niagara Escarpment Horseshoe Moraines A collection of discontinuous, individual moraine ridges occur west of the Niagara Escarpment. The local topography is irregular, sloping generally to the south and southwest, with a scattering of small, isolated knobs and equally isolated small basins (“kettles"). From the edge of the Escarpment, the moraines (such as the Paris Moraine) form a belt of moderately hilly relief passing through the west portion of the Preliminary Study Area. Associated with the moraines is a system of spillways with broad sand and gravel terraces and swampy valley floors. Within the Preliminary Study Area, the soils are coarse, stony tills with traces of red shale. Flamborough Plain A relatively level Flamborough Plain is in the southwest part in the Preliminary Study Area. The Plain is an isolated area of shallow tills overlying limestone bedrock and is characterized by numerous wetland pockets and complexes. Numerous drumlins are scattered across the plain. Guelph Drumlin Field Centering on the City of Guelph, the Guelph Drumlin Field contains approximately 300 drumlins of all sizes on a sloping plain. The stony tills of the drumlins and the deep gravel terraces of old melt water channels are covered by a shallow veneer of loam. 3.1.3 East of the Niagara Escarpment South Slope The South Slope is the southern slope of the Oak Ridges Moraine and, within the Preliminary Study Area, is located north of the Peel Plain. The South Slope is a gently rolling till plain, characterized by numerous drumlins oriented upslope. Melt water streams cut sharp valleys in the till, locally exposing the underlying sediments. Peel Plain Between Lake Ontario and the South Slope, the Peel Plain is an expansive area (encompassing the central portions of the Regional Municipalities of Halton, Peel and York and the northwestern portion of the City of Toronto), characterized by level to undulating topography with a general uniform slope toward Lake Ontario. Across this plain, the Credit River and Bronte Creek have cut deep stream valleys into the clay soils. It is also of agricultural significance due to its unique till soil. Oak Ridges Moraine The Oak Ridges Moraine is one of the most distinctive physiographic regions in southern Ontario. It extends over 160 km from the Niagara Escarpment to the Trent River, ranges in width from 5 to 15 km, and reaches an elevation of approximately 400 m in some places. The Oak Ridges Moraine forms the drainage divide between water flowing south into Lake Ontario and water flowing north. Its hummocky, knob-and-kettle surface topography reflects the variety 18 GTA West GTA West Corridor Planning & Environmental Assessment Study – Stage 1 Overview of Environmental Conditions and Constraint Working Paper December 2010 of glacial and melt water processes that led to its formation. The hills are predominantly composed of sand and gravel, but some, including the highest, are composed of till. The Oak Ridges Moraine is located in the north-eastern corner of the Preliminary Study Area as shown on Exhibit 3-20. 3.2 GROUNDWATER 3.2.1 Geology Quaternary Geology The quaternary (surficial) geology of the Preliminary Study Area consists of glacial, glaciofluvial, melt water channel, and glaciolacustrine deposits of Pleistocene age (Singer et al., 2003). Specifically, the predominant deposits are the Wentworth Till and the Halton Till. Exhibit 3-1 illustrates the general quaternary geology of the Preliminary Study Area. Wentworth Till The Wentworth Till occupies a broad tract of undulating ground in the vicinity of the City of Guelph, and east towards the Niagara Escarpment. This sandy-silt to silt-matrix till is interspersed with ice-contact and outwash deposits of sand and gravel at or near the surface. The combined thickness of these surficial deposits in this area can reach 80 m (Golder Associates Ltd, 2006). Halton Till The Halton Till occurs over much of the Preliminary Study Area east of the Niagara Escarpment, and as a thin strip along the edge and over the lower slopes of the Escarpment (Singer et al., 2003). This silt to clayey-silt till is representative of the last Wisconsinian ice advance out of the Lake Ontario basin (MOE, 2001). The reddish colour of the till is due to the colour of the underlying Queenston Shale, which makes up the parent material (CVC, 2002). Ice-contact deposits are also prevalent near Georgetown, Huttonville, and Milton, and in the vicinity of surface watercourses. Overburden thickness in this portion of the Preliminary Study Area ranges between 10 to 20 m, though it can reach 50 m in some places (Singer et al., 2003). Significant glaciolacustrine deposits are located in the vicinity of Milton and Woodbridge/Kleinburg. The thickness of the deposits is generally less than 1 m and consists of clay, silt and fine sand overlying the Halton Till. Melt water channel deposits of gravel and sand was deposited in old glacial melt water channels associated with the various ice lobes that infringed on the Preliminary Study Area. One channel system occurs along the Black River and Silver Creek, and extends to Georgetown. A second channel extends from the settlement of Albion outside of the Preliminary Study Area towards Inglewood. Below/south of Inglewood, the channel tracks beneath the East Credit River to Terra Cotta where it re-emerges and continues to Glen Williams (MOE, 2001). The thickness of the deposits associated with the melt water channels is highly variable (generally between 10 to 30 m). 19 0 5 0 \ 5 GTA West 0 \ 0 Palgrave 1 Mono Mills 0 2 53d Corridor Planning 9 y 51a a King City hw g i H And Environmental d x m . 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