Lower Don River West Remedial Flood Protection Project TABLE OF CONTENTS. Page. Executive Summary

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1 TABLE OF CONTENTS Page Executive Summary 1.0 INTRODUCTION Purpose of the Undertaking Study Area Description Description of the Undertaking Rationale for the Undertaking BACKGROUND History of the Problem Overview of Previous Studies Conservation Authority Involvement Justification Concurrent and Related Studies PUBLIC AND AGENCY CONSULTATION Consultation History Public & Agency Notifications Information Releases Open Houses/Workshops Community Liaison Committee Technical Advisory Committee Summary of Issues and Concerns Public Information Centre No. 1 January 19, Public Information Centre No. 2 April 29, Public Information Centre No. 3 September 21, Mississaugas of New Credit First Nation Ontario Mile Corporation Raceway DESCRIPTION OF LOWER DON The Don River Watershed Lower Don River Flooding - A Historical Perspective Physiographic Description Baseline Studies Hydrologic/Hydraulic Characterization Hydrologic Analyses Hydraulic Analysis Aquatic Investigations General Fish Community Assessment Water Temperature Survey Benthic Invertebrate Sampling Water Chemistry Monitoring Terrestrial Natural Heritage Terrestrial Attributes Avian Migratory Stopover and Corridor Evaluation Cultural Resources Built Heritage i

2 4.8.2 Archaeology Socio-Economic & Land Use Existing Land Use Methodology Flood Damage Assessment Topography, Soils, Groundwater and Soil Contamination Existing Infrastructure Utility Lines Rail Infrastructure EXAMINATION OF ALTERNATIVES Approach Overview Description of Long List of Alternatives Do Nothing Flood Policy Revision Flood Protection Landform with East Bank Works & Culvert Flood Protection Landform with East Bank Works (No culvert) Wedge with East Bank Works &Culvert Wedge & East Bank Works CN Rail Bridge & Channel Widening Secondary Channel with Flood Protection Landform Floodwall/Dyke Upstream Storage Floodproofing of Individual Structures River Dredging Watershed Conservation Measures Screening of Alternatives Evaluation of Alternatives and Selection of Preferred Alternative Physical Assessment Group Biological Assessment Group Cultural Assessment Group Socio-Economic Assessment Group Engineering/Technical Assessment Group Cost Assessment Group Comparative Evaluation Summary of Evaluation FUNCTIONAL DESIGN & ENVIRONMENTAL ASSESSMENT General Refinement of the Preferred Alternative Hydro One Networks Plant Geo-Environmental/Geotechnical Investigations Bridge Extension Option for Additional Hydraulic Capacity (Selected as Preferred Option) Project Description Design Requirements for the Flood Protection Landform Provincial Context Details of the Flood Protection Landform Grading Considerations Landform Composition Construction Considerations Traffic Effects ii

3 6.4.7 Stormwater Management Utility Relocation Integration with West Don Lands Precinct Plan Details of the Remedial Works at the CN Rail Embankment General Multi-Cell Culvert Option Bridge Extension Option Identification of Preferred Option (Bridge Extension) for the CN Rail Embankment East Bank Retaining Wall/Dykes Keating Channel Dredging Modifications to the Enbridge Utility Bridge Cost Assessment of Effects and Benefits Physical Environment Biological Cultural Land Use/Socio-Economic Engineering/Technical Mitigation Strategy Project Monitoring Construction Monitoring Operation Monitoring Landscape Plan Planting Zones Demonstration Plan Pedestrian Circulation and Access SUMMARY OF FINDINGS & CONCLUSIONS Preferred Remedial Flood Protection Alternative Baseline Inventories Environmental Effects of the Flood Remediation Project Mitigation Plan Final Design & Implementation Considerations Other Considerations Bibliography iii

4 List of Tables Table Summary of Summary of Calculated Peak Flows (Future Land Use) Table Comparison of Calculated Flows Hurricane Hazel Table Regulatory Flood Levels Along the Lower Don River Table Classification of Fish Captured in the Lower Don River Table Existing Land Use in Spill Zone Table Industrial/Commercial/Industrial Flood Damage Values Table Flood Damages by Primary Land Use Table Study Area Utilities Table Screening the Long List of Alternatives Table Comparative Evaluation of Alternatives Table Ranking of Alternatives Table Summary of Alternatives Ranking by Criteria Group Table Calculated Hydraulic Conditions for the Regulatory Flood Table Weekend Delays to Via Rail Service (No Track Diversion) Table Summary of Construction Work Blocks & Associated Impacts on Train Operations for Multi-cell Culvert Option (No Track Diversion) Table Preliminary Cost Estimate for Multi-Cell Culvert Option Table Construction Sequencing & Time Requirements for Installation of the Bridge Extension Option Table Preliminary Cost Estimate for the Bridge Extension Option Table Summary of Option Evaluation Table Summary of Preliminary Costs Table Summary of Effects Table Description of Potential Effects Table Summary of Mitigation Strategies Table Flood Protection Landform Vegetation Zones List of Figures Figure Study Area Figure Component Works Figure Regulatory Floodplain along the Lower Don River Figure Floodwater Depths along the Lower Don River for the Regulatory Flood Figure Existing Land Use in the Don River Watershed Figure Future Land Use in the Don River Watershed Figure Extent of Flooding in the Lower Don River During a Hurricane Hazel Event Figure Water Surface Profile Existing Conditions Figure Seasonal Distribution of Fish Species in the Lower Don River Figure Terrestrial Natural Heritage Study Area and Community Ranks Figure Avian Migratory Stopover Evaluation Stations Figure Heritage Resources South and East of the Lower Don River Figure Existing Land Use Figure Official Plan Designation in Spill Zone Figure Flood Depths in Spill Zone iv

5 Figure Flood Protection Landform with Culvert & East Bank Works Figure Flood Protection Landform & East Bank Works Figure Wedge with Culvert & East Bank Works Figure Wedge & East Bank Works Figure Secondary Channel with Flood Protection Landform Figure Existing & Potential Storage Sites Figure Extent of River Dredging Figure Location of Hydro One Plant Figure Location Plan of Geo Environmental/Geotechnical Investigations Figure Generalized Stratigraphy Figure 6.4 -, Component Works Figure Flood Protection Landform Plan Figure 6.6A - Flood Protection Landform Cross-Sections Figure 6.6B - Flood Protection Landform Cross-Sections Figure Utilities Figure CN Rail Crossing of Lower Don River Figure General Arrangement Culvert Option at CN Rail Crossing Figure Plan Culvert Option at CN Rail Crossing Figure HEC-2 Cross Section Numbers & Location Figure Construction Staging Figure General Arrangement Bridge Option at CN Rail Crossing Figure Plan-Bridge Option at CN Rail Crossing (21.3 m Span) Figure Remedial Flood Works for the East Bank Figure Flooding Depths with in Place Figure Flood Protection Landform Vegetation Zones Figure Flood Protection Landform Vegetation Zones (Section View) Figure Demonstration Plan Figure Demonstration Plan (Section View) Figure Potential Trail Concept Plan List of Appendices Appendix A... Public Information Centre Material Appendix B... Mississaugas of the New Credit Appendix C...Correspondence with Stakeholders Appendix D... Hydraulic Modelling Details Appendix E...Aquatic Investigations Appendix F... Terrestrial Natural Heritage Appendix G...Cultural Heritage Appendix H...Geo-Environmental Study Appendix I... Rail Transportation Study Appendix J... Geo-Environmental and Geotechnical Field Investigations Appendix K...Report on Alternatives for the East Bank v