1. 00/2015 Public Information Centre Addendum to the Environmental Study Report: Millbrook Dam Tuesday, October 20, 2015

2. 2 00/2015 Hatch Ltd. Hatch is an employee-owned firm with headquarters in Mississauga, Ontario. Hatch brings significant engineering and environmental assessment experience in the rehabilitation, development, design and planning of major and minor dam related projects. Over the last 15 years we have undertaken over 300 dam safety assessments for various clients including the MNRF, CAs and various municipalities. Hatch has served clients for over six decades with corporate roots extending over 100 years and has project experience in more than 150 countries around the world.

3. 3 00/2015 What are the Project Objectives? 1. Update the Preliminary Screening of Options: Alternative 1 – Do Nothing Alternative 2 – Full Decommissioning Alternative 3 – Channel Works Alternative 4 – Reduce Probability of Failure Alternative 5 – Attenuation Alternative 6 – Increase Hydraulic Capacity 2. Update Solutions for Achieving Increased Hydraulic Capacity: Concept A – Spillway Removal and Channel Restoration Concept B – Spillway Removal and Off-line Pond Concept C – Spillway Reconstruction with Headpond Retention 3. Identify and Evaluate Various Options to Achieve the new Preferred Solution (Concept C)

4. 4 00/2015 1. Update the Preliminary Screening of Options Hatch has updated the preliminary Screening of all broadly defined, generic options as presented in the 2013 draft Environmental Screening Report (ESR) based on the 2015 Dam Safety Assessment Update Report prepared by D.M. Wills Associates Ltd. The preferred option continues to be Alternative 6 – Increase Hydraulic Capacity as was previously presented in the draft ESR, and aligning best with expressed community values.

5. 5 00/2015 What are the Project Objectives? 1. Update the Preliminary Screening of Options: Alternative 1 – Do Nothing Alternative 2 – Full Decommissioning Alternative 3 – Channel Works Alternative 4 – Reduce Probability of Failure Alternative 5 – Attenuation Alternative 6 – Increase Hydraulic Capacity 2. Update Solutions for Achieving Increased Hydraulic Capacity: Concept A – Spillway Removal and Channel Restoration Concept B – Spillway Removal and Off-line Pond Concept C – Spillway Reconstruction with Headpond Retention 3. Identify and Evaluate Various Options to Achieve the Preferred Solution (Concept C)

6. 6 00/2015 2. Updated Solutions for Achieving Increased Hydraulic Capacity The solutions for achieving increased hydraulic capacity remain the same as those presented in the 2013 draft ESR (Concepts A, B and C) and continue to incorporate: iThe community values as presented in the 2013 draft ESR iiThe need to address the problems associated with the condition of the dam Hatch has updated Concepts A, B and C to also incorporate: iiiAlignment with the findings of the 2015 Dam Safety Assessment Update Report. ivThe estimated 50-year life cycle cost of each of the Concepts, including the cost of management and major maintenance over a year 50 operation of the facilities

7. 7 00/2015 i. Community Values The following community values were identified in the 2013 draft ESR for consideration in the evaluation of potential solutions: Maintaining the size and water level of Mill Pond Headpond sediment removal and restoration of Mill Pond Maintenance of public access across the dam via a foot bridge Waterfall effect producing sights and sounds similar to existing conditions

8. 8 00/2015 ii. Dam Condition Problems The evaluation of alternatives has also incorporated the need to address the existing issues and problems associated with the current condition of the dam: seepage through the embankments deteriorating penstock intake structure

9. 9 00/2015 iii. Findings of the 2015 Dam Safety Assessment Update Report The 2015 Dam Safety Assessment Update Report was undertaken to update the 2008 Dam Safety Review for Millbrook Dam to incorporate the a number of Technical Bulletins released by MNRF in 2011 under the Lakes and Rivers Improvement Act (LRIA). The 2015 Report concluded that the hydraulic capacity of the dam needed to be increased for the new Inflow Design Flood (IDF) of 181 m 3 /s.

10. 10 00/2015 iv. Estimated 50-Year Life Cycle Costs Solutions for Achieving Increased Hydraulic Capacity and “Do Nothing” Alternative 2013 Construction Costs 2015 Construction Cost 50-Year Life Cycle Cost 1 Concept A: Spillway Removal and Channel Restoration $ 3,090,000$ 3,077,550$ 3,637,000 Concept B: Spillway Removal with Off-Line Pond $ 3,249,000$ 3,214,000 $3,781,000 Concept C: Spillway Reconstruction with Headpond Retention $ 2,948,000 $ 3,311,000 $ 3,973,000 2 Do Nothing N/A $ 4,886,000 Notes: 1 – 50 year life cycle cost includes cost of dam safety management program 2 – 50-year life cycle cost for Concept C is based upon a 30m Ogee Crest Weir and Harden Embankment Dam.

11. 11 00/2015 The Preferred Solution Remains Unchanged Based on Hatch’s updated solutions for achieving increased hydraulic capacity, the preferred solution remains: Concept A – Spillway Removal and Channel Restoration Concept B – Spillway Removal and Off-line Pond Concept C – Spillway Reconstruction with Headpond Retention

12. 12 00/2015 What are the Project Objectives? 1. Update the Preliminary Screening of Options: Alternative 1 – Do Nothing Alternative 2 – Full Decommissioning Alternative 3 – Channel Works Alternative 4 – Reduce Probability of Failure Alternative 5 – Attenuation Alternative 6 – Increase Hydraulic Capacity 2. Update Solutions for Achieving Increased Hydraulic Capacity: Concept A – Spillway Removal and Channel Restoration Concept B – Spillway Removal and Off-line Pond Concept C – Spillway Reconstruction with Headpond Retention 3. Identify and Evaluate Various Options to Achieve the new Preferred Solution (Concept C)

13. 13 00/2015 3. Identify and Evaluate New Spillway Options Several options to increase the spillway discharge capacity at Millbrook Dam were considered. Self-regulating overflow weirs such as a: Straight weir Labyrinth Weir Piano Keys Weir Gated spillways such as: Obermeyer spillway gates Vertical lift gates Radial gates Fuse-Plug spillway Fuse-Gate System Reducing the probability of dam failure through embankment dam hardening Raising embankment dam crest to allow for higher IDF reservoir level Lowering of the weir crest to increase the head and discharge capacity

14. 14 00/2015 3. Identify and Evaluate New Spillway Options The following criteria were also considered in Hatch’s evaluation: Safety and protection downstream Reliability and accuracy of the flood prediction Loading conditions including seismicity, ice, and sediment Potential for debris (i.e. ice) blockage Duration, amount and frequency of spill Geology, ground topography and river bathymetry Various dam types Operational considerations (i.e., remoteness of the site, experience of the owner, etc). Potential effects on the environment Costs (construction and operations)

15. 15 00/2015 Hatch’s Recommendation: 30m Ogee Weir Spillway and Harden Embankment Dam, with Headpond Retention at Existing Level Based on Hatch’s evaluation of the various options, this has been determined to be the most cost-effective option to comply with ORCA’s requirements under the LRIA, and align with the community’s values as documented within the 2013 ESR. Design ParameterPreferred Option 2013Preferred Option 2015 Width of Weir36 m30 m Spillway DesignSharp Crest Weir & Stepped Spillway Ogee Weir Chute Spillway & Hardened Embankment Dam Mill Pond Water Level0.5 m reduction in water level Maintain existing pond Sheet Pile InstallationRequiredNot Required Design Comparison: 2013 vs 2015 Preferred Options

16. 16 00/2015 Existing Dam

17. 17 00/2015 Graphical Rendering of Recommended Option

18. 18 00/2015 General Arrangement

19. 19 00/2015 Ogee Weir Spillway On Ogee weir spillway is designed to conform with the profile of a sheet of water as it overflows.

20. 20 00/2015 Hardening of an Embankment Dam Hardening of an embankment dam involves the application of an erosion control “blanket” comprised of concrete blocks, locked together and embedded with high strength geogrid.