East Humber River at Langstaff Road Rehabilitation Project Project Plan City of Vaughan Toronto and Region Conservation Authority May 30, 2014
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East Humber River at Langstaff Road Rehabilitation Project Project Plan City of Vaughan Toronto and Region Conservation Authority May 30, 2014 Waterfront Office, 1 Eastville Avenue, Toronto, Ontario M1M 2N5 Acknowledgements Toronto and Region Conservation Authority gratefully acknowledge the following people for their contributions to the East Humber River at Langstaff Road Rehabilitation Project. Michael McNamara City of Vaughan Melanie Morris City of Vaughan Robert O’Hara City of Vaughan Imran Khan GHD Jeff Doucette GHD Mark Heaton Ministry of Natural Resources Emily Funnell Ministry of Natural Resources Ashour Rehana Toronto and Region Conservation Authority Maria Parish Toronto and Region Conservation Authority Mark Preston Toronto and Region Conservation Authority Marnie Krokos Toronto and Region Conservation Authority Matt Kenel Toronto and Region Conservation Authority Matthew Johnston Toronto and Region Conservation Authority Mike Puusa Toronto and Region Conservation Authority Moranne McDonnell Toronto and Region Conservation Authority Nick Saccone Toronto and Region Conservation Authority Patricia Newland Toronto and Region Conservation Authority Ralph Toninger Toronto and Region Conservation Authority Rudra Bissoon Toronto and Region Conservation Authority Susan Robertson Toronto and Region Conservation Authority i EXECUTIVE SUMMARY Toronto and Region Conservation Authority (TRCA) continues to work towards ensuring healthy rivers and shorelines, greenspace and biodiversity, and sustainable communities. One key step in this process is the design and implementation of erosion control works for projects. The East Humber River at Langstaff Road Rehabilitation Project is being completed in accordance with the Class Environmental Assessment for Remedial Flood and Erosion Control Projects (2013) or Class EA, with the objective of reducing risk to life and property, as per the mandate of Conversation Authorities, under the Conservation Authorities Act (R.S.O. 1990). The erosion problem along this section of the East Humber River was first identified to TRCA in 2004 when City of Vaughan staff expressed concern over the close proximity of the erosion scar to their public Works Yard (herein referred to as the “Works Yard”). Following a visual inspection by TRCA staff, it was recommended that remedial works be undertaken to repair the scar; however, no funding was secured and the erosion continued unabated. With the progression of erosion impacting the Works Yard property, TRCA retained Geomorphic Solutions Ltd. to conduct a geomorphic assessment and erosion risk analysis of the East Humber River near the Works Yard in late 2010. Geomorphic Solutions reported that the erosion was likely triggered by straightening of the channel upstream of the site between 1960 and 1966. As a result, this shifted the channel thalweg significantly which changed the meander form of the river and increased lateral migration throughout the project area. As a result of this migration, the erosive forces of the river have been directed towards the Works Yard. The July 8, 2013 storm event further accelerated site erosion and undermined the fence and a portion of the parking lot at the Works Yard. Slight changes in river morphology have concentrated erosive actions to the downstream portion of the scar and the bowstring bridge. This change on site was significant enough to warrant additional surveying works and additional design details for the preferred alternative. A Notice of Intent formally initiating the project under the Class EA, was published in Vaughan Weekly on May 30, 2012. Furthermore, letters were sent to possible interested persons from the City of Vaughan Council members, Aboriginal groups, community groups, and government regulatory agencies. There was no interest in the Project following the notices. As such, a Technical Steering Committee (TSC) comprised of TRCA, City of Vaughan and Ministry of Natural Resources (MNR) representatives was created to review conceptual options and provide guidance on the overall design. The preferred solution, determined through the Class EA process for this project, includes stabilizing the east bank with a vegetated stone buttress and rootwads. This bank protection will extend downstream from approximately mid-scour to the concrete abutment of a bowstring bridge that is currently closed to the public due to safety issues. The west bank will have a similar treatment protecting the area upstream of the bridge abutment to ensure the river planform does not change and place Langstaff Road at risk. Following the thirty (30) day public review period of this Project Plan and the successful resolution of any concerns received during the review period, TRCA intends to finalize the detailed design of the preferred solution and obtain the necessary approvals required to proceed to the implementation phase of this project. ii Table of Contents 1.0 INTRODUCTION .................................................................................................................... 1 1.1 Relationship of the Undertaking to the Environmental Assessment Act ......................... 1 1.2 Purpose of the Undertaking .................................................................................................. 4 1.3 Site Description ...................................................................................................................... 4 1.4 General Description of the Undertaking .............................................................................. 7 1.5 Rationale for Undertaking ..................................................................................................... 8 2.0 BACKGROUND ...................................................................................................................... 8 2.1 History of the Problem ........................................................................................................... 8 2.2 Identification of Previous Studies ...................................................................................... 10 2.2.1 Geomorphic Assessments ................................................................................................ 10 2.2.2 Planning Documents ......................................................................................................... 10 2.2.3 Aquatic and Terrestrial Habitat Reports ........................................................................... 11 2.2.4 Socioeconomic and Cultural Heritage Studies ................................................................. 12 2.3 Stage 1 and 2 Archaeological Assessment ........................................................................... 17 2.4 Justification of Conservation Authority Involvement .............................................................. 17 3.0 BASELINE ENVIRONMENTAL INVENTORY ...................................................................... 19 3.1 Existing Site Conditions ...................................................................................................... 20 3.1.1 Physical Environment ....................................................................................................... 20 3.1.2 Biological Environment ..................................................................................................... 23 3.1.3 Cultural Environment ........................................................................................................ 30 3.1.4 Socioeconomic Environment ............................................................................................ 31 3.1.5 Engineering/Technical Environment ................................................................................. 32 4.0 EVALUATION OF REMEDIAL ALTERNATIVE OPTIONS .................................................. 33 4.1 Description of Preliminary Concepts ...................................................................................... 33 4.1.1 Preliminary Option 1 - “Do Nothing” Alternative ............................................................... 33 4.1.2 Preliminary Option 2 – Local Armouring without Channel Infilling .................................... 35 4.1.3 Preliminary Option 3 – Local Armouring and Downstream Protection without Channel Infilling 37 4.1.4 Preliminary Option 4 – Minor Realignment Works ............................................................ 39 4.2 Evaluation of Preliminary Concepts .................................................................................. 41 4.3 Selection of the Preferred Alternative ................................................................................ 43 4.4 Refinement of the Preferred Alternative ............................................................................ 43 5.0 ENVIRONMENTAL SCREENING ......................................................................................... 43 5.1 Detailed Environmental Analysis of the Preferred Alternatives ...................................... 43 5.1.1 Physical Environment ....................................................................................................... 47 5.1.2 Biological Environment ..................................................................................................... 47 5.1.3 Cultural Environment ........................................................................................................ 48 5.1.4 Socioeconomic Environment ............................................................................................ 49 5.1.5 Engineering/Technical