Ashbridges Bay Erosion and Sediment Control Project Conservation Ontario Class Environmental Assessment Environmental Study Report
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Ashbridges Bay Erosion and Sediment Control Project Conservation Ontario Class Environmental Assessment Environmental Study Report Toronto and Region Conservation Authority and the City of Toronto December 2014 ACKNOWLEDGEMENTS The Toronto and Region Conservation Authority and City of Toronto gratefully acknowledge the efforts and contributions of the following people participating in the planning and design phases of the Ashbridges Bay Erosion and Sediment Control Class Environmental Assessment: Alberta D’Souza, Toronto and Region Conservation Authority Angus Armstrong, Toronto Port Authority Beverly Edwards, Toronto Ornithological Club Bill Snodgrass, City of Toronto Bob Kortright, Toronto Field Naturalists Cathy Eden, Toronto and Region Conservation Authority Chris Dunn, City of Toronto Councillor Mary-Margaret McMahon, City of Toronto Councillor Paula Fletcher, City of Toronto David Hatton, Toronto and Region Conservation Authority Erica Dewell, Toronto and Region Conservation Authority Frank Quarisa, City of Toronto Gord MacPherson, Toronto and Region Conservation Authority James Roche, Waterfront Toronto James Yacoumidis, City of Toronto Joe Delle Fave, Toronto and Region Conservation Authority John Edwards, Toronto Hydroplane & Sailing Club Karen McDonald, Toronto and Region Conservation Authority Ken Dion, Toronto and Region Conservation Authority Laura Stephenson, Toronto and Region Conservation Authority Lisa Turnbull, Toronto and Region Conservation Authority Maria Zintchenko, Toronto and Region Conservation Authority Mark Preston, Toronto and Region Conservation Authority Milo Sturm, Shoreplan Engineering Nancy Gaffney, Toronto and Region Conservation Authority Nick Saccone, Toronto and Region Conservation Authority Nolly Haverhoek, Toronto Beaches Lions Club Philip Cheung, City of Toronto Rachel Lewis, Navy League of Canada Ralph Toninger, Toronto and Region Conservation Authority Rick Portiss, Toronto and Region Conservation Authority Rob Grech, Toronto and Region Conservation Authority Robert Hedley, Ashbridges Bay Yacht Club Ron Anderson, Navy League of Canada Sarah Box, Friends of the Spit Sean Harvey, City of Toronto Susan Stuart, Balmy Beach Canoe Club Ted Bowering, City of Toronto Thomas Sciscione, Toronto and Region Conservation Authority EXECUTIVE SUMMARY Ashbridges Bay is a vibrant community with a host of land and water based recreational opportunities for residents and visitors - all nestled beside the City of Toronto’s largest wastewater treatment plant. Following construction of Ashbridge’s Bay Park in the mid-1970s, sediment eroding from the Scarborough Bluffs that was transported westward began to be deposited in the eastern embayment of the Park, creating a large beach (Woodbine Beach). As the embayment filled in, a sandbar began to form offshore, causing the sediment moving within the water system to then bypass the park. A large portion of the sediment bypassing Ashbridges Bay Park is now being deposited at the mouth of Ashbridges Bay in the Coatsworth Cut navigation channel. Coatsworth Cut is located at the western boundary of Ashbridge’s Bay Park. The Bay and Cut have serviced several boating clubs since the 1930s and the general public via three public boat launches since 1977. Currently there are several hundred vessels seasonally moored in the area at local yacht and sailing clubs. Various non-motorized vessels (canoes, kayaks and paddleboards) also use the area for recreation and competitive training. In 1983, Toronto and Region Conservation (TRCA) began dredging operations at the Coatsworth Cut navigation channel to maintain safe boat passage. Maintenance dredging has been conducted 20 times in the past 30 years and is currently required on an annual basis. TRCA has been interested in undertaking remedial works at Ashbridges Bay to find a long term solution for the erosion and sedimentation issues. TRCA began the first Conservation Ontario Class Environmental Assessment (EA) study to address this issue in 2002. At the same time, a number of other planning studies were underway in the area. TRCA suspended their study while the City of Toronto completed and received approval for two EAs which will change the local shoreline to allow for enhanced stormwater and wastewater treatment for the City’s growing population. In 2009 TRCA partnered with Waterfront Toronto to re- examine the remedial solutions for the erosion and sediment issues in the area with an expanded project scope that proposed the relocation of existing boat clubs in Ashbridges Bay to a newly created land base on Ashbridges Bay Park. The study was suspended when projected costs exceeded the available budget. With a refined scope in 2013, the TRCA partnered with the City of Toronto to resume the EA study once again. The Ashbridges Bay Erosion and Sediment Control Conservation Ontario Class EA is Step 1 of the Ashbridges Bay Landform Project. This EA study seeks an erosion and sediment control solution that can be integrated into the City of Toronto’s approved facilities which lie within the waterlot south of the Ashbridges Bay Wastewater Treatment Plant. In Step 2 of this project a detailed design exercise, with input from stakeholders and the general public, will be undertaken for the landform. Although this EA has considered and ensured that the remedial solutions do not preclude opportunities for things such as public access, trail connections and enhancing coastal and terrestrial habitat, these will be explored in depth for the landform as a whole in Step 2. The objective of the Ashbridges Bay Erosion and Sediment Control Class EA is to identify a preferred solution that will mitigate erosion and sediment deposition at the harbour entrance of Coatsworth Cut in order to ensure safe navigation - while considering the various approved facilities, planning initiatives and current uses in the study area. Extensive work was undertaken in previous initiations of the erosion and sediment control studies in the area which identified a number of remedial alternatives. These alternatives were revisited with the re-initiation of this study, and, through a screening process, those that met the project scope were carried forward and subsequently refined to consider and integrate into the City of Toronto’s approved facilities (high rate treatment facility and treatment wetland). The alternatives refinement resulted in three remedial alternatives in addition to the ‘Do Nothing” Alternative being carried forward for evaluation as part of this EA study. The ‘Do Nothing’ alternative was considered to be status quo – i.e., maintaining on-going dredging as it is currently required to keep the navigation channel open. All three remedial alternatives consist of shore connected breakwaters which are designed to keep sediment from entering the Coatsworth Cut channel. The difference between these alternatives is the positioning of the main breakwater in proximity to the Ashbridges Bay Wastewater Treatment Plant's seawall gates. During heavy rainfall or snowmelt, large amounts of stormwater combine with sanitary sewage in older areas of Toronto that are serviced by combined sewers. During high flow conditions, a portion of the effluent treated at the wastewater treatment plant is discharged through the seawall gates. The remedial alternatives needed to be designed to allow for the on-going use of the seawall gates. The distinguishing features (main breakwater position) of the alternatives are as follows: Alternative 1: The main breakwater is positioned on the western side of the Ashbridges Bay Wastewater Treatment Plant’s seawall gates. Alternative 2: The main breakwater is positioned on the western side of the Ashbridges Bay Wastewater Treatment Plant’s seawall gates and a smaller breakwater is positioned on the east side of the seawall gates to act as a defector. Alternative 3: The main breakwater is positioned on the eastern side of the Ashbridges Bay Treatment Plants’ seawall gates and a secondary breakwater is positioned on the west side to form a channel for seawall gate discharge. All three of the remedial alternatives feature a smaller breakwater that is shore connected to the headland at Ashbridges Bay Park. In combination with the primary breakwaters for each alternative this breakwater defines the entrance of the new navigation channel. All of the three Alternatives also feature a cobble beach that integrates the breakwaters with the other approved City of Toronto facilities. The three remedial alternatives, along with the “Do Nothing” were evaluated against each other based on the following: Physical Environment; Natural and Biological Environment; Socio-economic Environment; Cultural Environment; Feasibility and Cost; and Technical Considerations Alternative 3 was selected as the preferred alternative as a result of the evaluation and subsequent support from stakeholders and the public. The defining factor in the evaluation was Alternative 3’s ability to have a potential positive impact on water quality in the recreational boating areas whereas Alternatives 1 and 2 could potentially have negative impacts on Phosphorus and E. coli levels. This potential positive impact with Alternative 3 is achieved by the separation of the seawall gate discharge from the recreational boating areas. Alternative 3 also offers the best integration of existing and planned City of Toronto infrastructure and will provide decades of safe navigation in Coatsworth Cut without dredging. Ashbridges Bay Erosion and Sediment Control Class EA Preferred