Ashbridges Bay Treatment Plant Outfall Conceptual Design & Receiving Water Assessment ICMC Meeting #3 March 2015
MEETING AGENDA • Introduction of ICMC & Project Team • Meeting Objective • Project Background • Evaluation of Alternatives • Project Implementation • Achieved Outcomes • Discussion 2
INTRODUCTIONS • Personal Introductions • Project Team CH2M HILL – Prime consultant for outfall modelling Hatch Mott MacDonald – Outfall conceptual design Baird – Lake modelling and sediment modelling Previous ICMC Meetings • March 2012 – Background and Project Approach October 2013 – Preliminary Evaluation of Alternatives 3
MEETING OBJECTIVE Meeting Objective To obtain ICMC input on the draft conceptual outfall design. 4
PROJECT BACKGROUND 5
WHY ARE WE LOOKING TO REPLACE THE EXISTING OUTFALL? • The existing outfall was constructed in the late 1940s and has insufficient capacity • The existing outfall does not meet current regulatory standards • For these reasons a commitment to the public was made to replace it 6
PROJECT OBJECTIVE & SUCCESS FACTORS • Project Objective Deliver a conceptual design for a new outfall that meets regulatory acceptance and improves nearshore water quality in Lake Ontario • What are the important success factors for the project? Achieve regulatory endorsement and acceptance on the Conceptual Design Gain stakeholder understanding Develop an economically and environmentally feasible solution
PROJECT OBJECTIVE & SUCCESS FACTORS • Your key success factors Reduce impacts on the natural environment Effective stakeholder process Fulfills EA commitments Timely project completion (From March 2012 ICMC meeting)
EVALUATION OF ALTERNATIVES 9
EVALUATION PROCESS We were here at the last ICMC meeting in October 2013 We are now here 10
SCREEN OUTFALL CONFIGURATIONS Recap from previous meeting • Configurations based on 1986 preferred alignment which is clear of buried valley and ridge features • “Must Have” Screening Criteria included: • Mixing performance • Water quality at water treatment plant intakes • Water quality at recreational beaches • Longer outfall lengths met mixing and water quality criteria Outfall Lengths that 2700m 3500m Passed Screening 11
DEVELOP OUTFALL ALTERNATIVES Construction Approaches • Tunnel Construction Open Cut • Construction • Hybrid Construction 12
ASSESS OUTFALL ALTERNATIVES Evaluation Criteria Criteria Categories: • Technical – Ease of implementation, operation and maintenance Natural – Aquatic systems, terrestrial systems, air quality • • Social – Public health, safety of plant and construction workers, quality of life Economic – Life-cycle costs • 13
ASSESS OUTFALL ALTERNATIVES Tunnel Construction • No dredging required - minimizes social and natural impacts • Fewer permits • Less complex to construct 14
ASSESS OUTFALL ALTERNATIVES Open Cut Construction • Shoreline excavation and shallow water dredging – high social and natural impacts • More permit requirements • Construction limited by weather and timing windows 15
ASSESS OUTFALL ALTERNATIVES Hybrid Construction • Dredging in deeper water – fewer social and natural impacts • Moderate permit requirements • A portion of construction is limited by weather and timing windows 16
RECOMMENDED ALTERNATIVE 3500m Tunnel Single tunnel • Similar to 1986 Concept • 7.0m internal diameter • • 3500m length • Tunnel Boring Machine (TBM) in bedrock 61 vertical “tunnel risers” • 61 diffuser ports • 17
RECOMMENDED ALTERNATIVE 3500m Tunnel 18
RECOMMENDED ALTERNATIVE Cost Estimate and Schedule Total Project Cost (2020 CAD) $340M Total Estimated Project Duration 7.3 years Design Construction Tender Completion Award Project 2015 2016 2017 2018 2019 2020 2021 2022 19
ACHIEVED OUTCOMES 20
INCREASED OUTFALL CAPACITY • Capacity shortfall of existing outfall has been addressed New outfall peak capacity will be 3,900 million litres per day • • Outfall is designed to not discharge through seawall gates to Ashbridges Bay 21
IMPROVED NEARSHORE WATER QUALITY PROPOSED OUTFALL
EA CONDITIONS HAVE BEEN MET EA Condition Is the Condition Met? Condition (1) – Document effluent quality for YES blended effluent during secondary bypass events. Condition 10 (ii) – Meet Provincial Water Quality YES Objectives (PWQO) at the edge of the mixing zone Condition 10 (iii) – Mitigate impacts on the Island YES and Harris WTPs Condition 10 (iii) – Eliminate need for seawall gates YES Condition 10 (viii) – Mitigate impacts on the YES beaches and shoreline Condition 12 – Mitigate impacts on fish and fish YES habitat 23
COMMITMENT TO THE PUBLIC • Met with the ICMC at each stage of this project • We will finalize the conceptual design after receiving your input 24
DISCUSSION 25
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