EtobicokE and MiMico creeks WatErshEds technical Update report 2010 Prepared by: Toronto and Region Conservation Authority acknowledgements The Etobicoke and Mimico Creeks Watersheds Technical Update Report was prepared by staff of the Toronto and Region Conservation Authority. Appreciation and thanks are extended to members of the Etobicoke and Mimico Watersheds Coalition, staff from watershed municipalities and government partners who provided input at various stages of the study. ©Copyright Toronto and Region Conservation 5 Shoreham Drive ,Downsview, Ontario, M3N 1S4, Canada Ph: (416) 661-6600 www.trca.on.ca ISBN 978-0-9811107-6-9 TABLE OF CONTENTS EXECUTIVE SUMMARY............................................................................................................. i 1.0 INTRODUCTION ........................................................................................................ 1-1 1.1 Technical Update Approach............................................................................................ 1-1 1.2 Report Scope and Organization...................................................................................... 1-2 1.3 Watershed Vision............................................................................................................. 1-2 1.4 Watershed Objectives, Indicators and Targets............................................................... 1-3 2.0 STUDY AREA AND PHYSICAL SETTING .................................................................. 2-1 2.1 Study Area and Location ................................................................................................. 2-1 2.2 Watershed and Subwatershed Boundaries ................................................................... .2-1 2.3 Land Use and Population ................................................................................................ 2-3 2.3.1 Current Land Use and Population....................................................................... 2-4 2.3.2 Planned Development ......................................................................................... 2-6 2.4 Climate .................................................................................................................. 2-8 2.5 Physiographic Regions.................................................................................................. 2-10 2.6 Surficial Geology and Geology ..................................................................................... 2-11 2.6.1 Scarborough Formation .................................................................................... 2-11 2.6.2 Sunnybrook Diamict .......................................................................................... 2-17 2.6.3 Thorncliffe Formation......................................................................................... 2-17 2.6.4 Newmarket Till ................................................................................................... 2-17 2.6.5 Oak Ridges Moraine and Mackinaw Interstadial Deposits ............................... 2-17 2.6.6 Halton Till ........................................................................................................... 2-17 2.6.7 Recent Deposits................................................................................................. 2-18 2.7 References….. ............................................................................................................... 2-21 3.0 GROUNDWATER QUANTITY AND QUALITY ............................................................ 3-1 3.1 Watershed Objectives, Indicators and Targets............................................................... 3-2 3.2 Objectives of Technical Update ...................................................................................... 3-2 3.3 Data Sources and Methods............................................................................................. 3-3 3.3.1 Data Sources ....................................................................................................... 3-3 3.3.2 Methods ............................................................................................................... 3-4 3.4 Existing Conditions and Interpretation............................................................................ 3-5 3.4.1 Hydrogeologic Units............................................................................................ 3-5 3.4.2 Groundwater Recharge ..................................................................................... 3-11 3.4.3 Groundwater Levels........................................................................................... 3-11 3.4.4 Groundwater Modelling..................................................................................... 3-23 3.4.5 Water Budget ..................................................................................................... 3-23 3.4.6 Groundwater Quality.......................................................................................... 3-34 3.5 Management Recommendations .................................................................................. 3-35 3.5.1 Development within former Brampton Esker Aggregate Pits........................... 3-35 3.5.2 Groundwater Recharge ..................................................................................... 3-37 3.5.3 Groundwater Levels........................................................................................... 3-38 3.5.4 Groundwater Quality.......................................................................................... 3-39 3.6 References ................................................................................................................ 3-40 3.7 Appendix 3-A: Aerial photographs of Esker Lake North taken between 1999 and 2007…………................................................................................................................. 3-42 Toronto Region Conservation, 2010 i 4.0 BASEFLOW AND WATER USE.................................................................................. 4-1 4.1 Watershed Objectives, Indicators and Targets............................................................... 4-2 4.2 Objectives of Technical Update ...................................................................................... 4-2 4.3 Data Sources and Methods............................................................................................. 4-2 4.3.1 Baseflow Data ...................................................................................................... 4-2 4.3.2 Groundwater Data ............................................................................................... 4-3 4.3.3 Surface Water Use Data ...................................................................................... 4-3 4.3.4 Streamflow and Climate Data.............................................................................. 4-3 4.4 Existing Conditions and Interpretation............................................................................ 4-4 4.4.1 Baseflow Trends .................................................................................................. 4-4 4.4.2 Measured Baseflow Findings .............................................................................. 4-9 4.4.3 Etobicoke and Mimico Creek Water Use .......................................................... 4-17 4.4.4 Summary of Findings ........................................................................................ 4-23 4.5 Management Recommendations .................................................................................. 4-25 4.6 References….. ............................................................................................................... 4-27 5.0 STORMWATER MANAGEMENT AND STREAMFLOW ............................................. 5-1 5.1 Watershed Objectives, Indicators and Targets............................................................... 5-3 5.2 Objectives of Technical Update ...................................................................................... 5-4 5.3 Data Sources and Methods............................................................................................. 5-4 5.3.1 Data Sources ....................................................................................................... 5-4 5.3.2 Method ................................................................................................................. 5-5 5.4 Existing Conditions and Interpretation............................................................................ 5-6 5.4.1 Existing Land Use................................................................................................ 5-6 5.4.2 Areas Covered by Comprehensive Stormwater Management (SWM)Plans.... 5-10 5.4.3 Existing SWM Controls ...................................................................................... 5-15 5.4.4 Stormwater Management Quality Treatment .................................................... 5-20 5.4.5 Stormwater Management Erosion Control........................................................ 5-24 5.4.6 Stormwater Management Quantity Control ...................................................... 5-27 5.4.7 Stormwater Management Retrofit Plans/ Strategies......................................... 5-30 5.4.8 Streamflow ......................................................................................................... 5-33 5.4.9 Summary of Recent Studies Relating to Stormwater Management................