Climate Change Vulnerability Assessment. for Selected Stormwater Infrastructure FINAL. August 2014

Transcription

1 Climate Change Vulnerability Assessment for Selected Stormwater Infrastructure August 2014 FINAL

2 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 1 Executive Summary Introduction The Greater Toronto Airports Authority s (GTAA s) mandate is to ensure that the Airport s facilities and air services match the needs of the growing population of the GTA and south-central Ontario. The Greater Toronto Area (GTA) is a 7,125 km 2 area consisting of the City of Toronto plus the neighbouring regional municipalities of Halton, Peel, York, Durham, and their 24 constituent municipalities. Toronto Pearson is the principal airport for southern Ontario. To address this significant responsibility, the GTAA embarked on a 30-year vision for the development of Toronto Pearson in Since that time, the GTAA s primary focus has been to replace obsolete airport infrastructure in order to improve the facilities and services that Toronto Pearson has to offer the region it serves. Toronto Pearson is located 25 km northwest of Toronto s central business district in the heart of the southern Ontario region. The Airport is surrounded by a variety of industrial, commercial and residential land uses and is bound by a series of major highways and regional arterial roads. The area of land within the current operational boundary of Toronto Pearson covers 1,867 ha (4,613 acres) and encompasses airside facilities, passenger and cargo terminals, parking, access roads, business aviation, and aviation support facilities. Due to its favourable location within Canada and North America, Toronto Pearson not only serves those visiting or living within south-central Ontario, but also the growing number of passengers using the Airport as a connecting point for onward journeys. Toronto s central gateway location means that an estimated 60 per cent of North America s population is within a 90-minute flight from Toronto Pearson. PIEVC Engineering Protocol To assess the potential impacts of climate change on public infrastructure and to advance planning and prioritization of adaptation strategies, Engineers Canada and its partners have established the Public Infrastructure Engineering Vulnerability Committee (PIEVC). Co-funded by Engineers Canada and Natural Resources Canada, the PIEVC is comprised of representatives from all three levels of government as well as non-governmental organizations. The Committee oversees the planning and execution of a national engineering assessment of the vulnerability of Canadian public infrastructure to climate change. The work of the PIEVC commenced in 2007 with a scoping study to examine the current state of infrastructure, the availability of climate data, and indicators of adaptive capacity during the development of the PIEVC Protocol for infrastructure vulnerability assessment. The Protocol was subsequently evaluated through seven pilot studies, which were included in the first national assessment report completed by the PIEVC in April Based on the success of these early studies and the interest among public infrastructure stakeholders in the results, Engineers Canada is continuing to promote the application of the PIEVC protocol in additional case studies in four priority infrastructure categories: buildings, roads and associated structures, stormwater and wastewater systems and water resources infrastructure. The results of these studies will be used to continue to refine and improve the protocol and further the program goals of supporting vulnerability assessment and adoption of best practices at the national scale. The GTAA decided to undertake an engineering vulnerability assessment of infrastructure in the context of both the existing climate and future climate change, using the PIEVC Protocol. The PIEVC Engineering Protocol for Climate Change Infrastructure Vulnerability Assessment (Version 10, October, 2011),

3 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 2 hereafter referred to as the Protocol, is a step-by-step process to conduct an engineering vulnerability assessment on infrastructure due to climate change. Potential issues and concerns arising from changing climate: Airport infrastructure is considered vulnerable to the types of weather related stresses that will be exacerbated by climate change; Climate change could threaten airport infrastructure; Potential flooding of runways, taxiways, aircraft manoeuvring areas, access roads could cause operational delays and physical damage to airport property; Stormwater runoff may exceed capacity of drainage and drainage systems; Potential wind damage to terminals, navigation equipment and signage; Disruption of airport operations, ground access, services supplied to the airport; Change in de-icing operations (increase, decrease of de-icing fluid quantities); and, Different needs for snow clearance and de-icing include combination of less snow but more ice. The five steps within the Protocol carried out to complete the vulnerability assessment were as follows: Step 1 Project Definition The boundary conditions for the vulnerability assessment were determined in Step 1. A description of the infrastructure including its location, age, loads, historical climate, and other relevant factors were developed. Initially, only certain components of the drainage and stormwater management system and the Spring Creek triple cell box culvert at Toronto Pearson will be assessed in detail. Ultimately, other infrastructure at Toronto Pearson will be assessed. Step 2 Data Gathering and Sufficiency The specific features of the infrastructure to be considered in the assessment as well as the applicable climate information were identified and evaluated for sufficiency in Step 2. Step 3 Risk Assessment The interactions between the infrastructure, the climate, and any other factors that could lead to vulnerability were identified in Step 3. This included identifying specific infrastructure components, specific climate change parameter values, and specific performance goals. In this step, the infrastructure s response to the climate parameters was identified. Based on the Protocol, the overall risk value associated with an interaction between an infrastructure component and a climate related event was determined by multiplying the probability of the event occurring by the severity of the impact. Scales of 0 7 were established for the probability of the interactions occurring and the severity resulting from the interaction. The Protocol provides three alternate methods each for the probability and severity scales from which the most appropriate method for this assessment was selected.

4 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 3 Performance response categories were established based on the most likely response of an infrastructure component to contemplated climate events. The performance response categories were based on professional judgment and experience. Instead of assessing the severity scale factor of each performance response for individual infrastructure components, all the performance responses that were relevant were check marked, and only one severity scale factor was applied. The severity scale factor that was applied was based on judgment of the performance response that was most critical to the individual infrastructure-climate interaction. The following points summarize the risk assessment findings for Toronto Pearson: Out of the 11,640 interactions identified for the risk assessment, about 27% had a risk score of above 12 and were therefore considered to be relevant for further consideration during engineering analysis. No interactions had a risk score of above 36, therefore none were considered to be high risk as defined by the Protocol; About 10% of low risk interactions increased to a medium risk score as a result of climate change. The highest increases were associated with extreme heavy rainfalls, heavy rainfalls, freezing rain, ice storms, and hurricanes/tropical storms. About 10% of medium risk interactions decreased to a low risk score as a result of climate change. The highest decrease was by a score of 6. This was associated with potential future decreases in cold waves and freeze-thaw cycles. Approximately 90% of interactions maintained their risk classification. Step 4 Engineering Analysis The impact on the infrastructure and its capacity resulting from the projected climate change loads was assessed in Step 4. This included a focused engineering analysis on the relationships determined to have vulnerability in Step 3. The infrastructure-climate interactions that scored a medium risk value (between 12 and 36) in Step 3 were analyzed further under this step. The analysis included a determination of the relationship between the loads placed under both existing and future conditions and the infrastructure components and their capacity. Vulnerability exists when the infrastructure has insufficient capacity to withstand the loads placed upon it. Therefore, there is a capacity deficit when vulnerability exists. There is adaptive capacity when the infrastructure is resilient i.e. it has sufficient capacity to withstand the climate change effects without compromising the ability of the infrastructure to perform as required. The Protocol dictates that the total loading and total capacity be used to calculate the Vulnerability Ratio. In general, data was insufficient to complete the engineering analysis in the specific quantitative method prescribed by the Protocol. In determining the climate load from the results of the Climate Analysis and Projections, the units were generally represented by number of occurrences per year, or a probability of the event occurring in a given year. This definition allowed the assignment of an existing and future climate load, however made the determination of the capacity of a component impossible in any meaningful, scientific way. For example, it is impossible to determine how many ice storms the bridge deck could withstand in a given year, or to put any number to the capacity of the operation buildings and tornadoes.

5 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 4 In light of the above, experience and professional engineering judgment were utilized to estimate whether or not the component was vulnerable or not, to a singular, or multiple, occurrences of the climate parameter. Therefore, the vulnerability ratio was qualitatively assessed to being either greater or less than one. If the total capacity was estimated to be greater than the total load, then the vulnerability ratio was listed as less than one. A vulnerability ratio of less than one means that the infrastructure component was resilient and not vulnerable to the climate parameter. If the total capacity was estimated to be less than the total load, then the vulnerability ratio would be greater than one, indicating that vulnerability exists. The Engineering Analysis generally resulted in a determination of the vulnerability of the infrastructure components to a single occurrence of the climate event, rather than the probability or frequency of the event. For example, personnel could be identified as being vulnerable to a freezing rain event for both existing and future conditions, with no distinction made regarding whether personnel are more or less vulnerable in the future with an increased probability of freezing rain events, as there is no information available with which to determine whether a change in frequency would increase the vulnerability of the components. The above notwithstanding, it was possible to make a determination of the difference between existing and future risk for the components and interactions identified as vulnerable by revisiting the results of the Risk Assessment completed in Step 3. In that assessment, the probability scores did change for some climate events, from the existing to future conditions, and the associated risk scores changed as well. Based on a comparison of those existing and future risk scores for vulnerable components and interactions, the potential effect of climate change in modifying risk to those components could be determined. The following sections provide a summary of the results for Toronto Pearson. The following points summarize the vulnerabilities identified in the engineering analysis step: A total of 3199 interactions were considered in the engineering analysis step; There were 7 interactions assessed to be vulnerable; and, Generally, the vulnerabilities exist to the following climate events: Extreme Heavy Rainfall, Heavy Rainfall and 5-Day Heavy Rainfall. Step 5 Recommendations The limitations and recommendations on the observations and findings of the infrastructure vulnerability assessment in Steps 1 to 4 were determined in Step 5. The main objective of this assessment is to identify components of the infrastructure which are at increased risk of failure, damage, deterioration, reduced operational effectiveness, and/or reduced life cycle from potential future changes in climate. Additionally, the study contains recommendations for remedial action to minimize the vulnerability and/or complete further study to further quantify the risks. During the completion of Step 5, recommendations were provided for actions to be taken to address the potential vulnerabilities, or for further investigations for GTAA to determine the extent of the vulnerability. These recommendations were provided for each of the components which were determined to be vulnerable.

6 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 5 Climate Analysis and Projections The study involved an assessment of the vulnerabilities of the facilities to current climate (existing and/or historical conditions), as well as future climate change at the 2050 time horizon. This study included assessment of the existing risks and vulnerabilities associated with the current climate, assessment of future risks and vulnerabilities, and an analysis of the change between the two. The climate analysis and projections portion of this study included the establishment of a set of climate parameters describing climatic and meteorological phenomena relevant to the geographic areas of the Toronto Pearson. The following climate parameters were selected for analysis in this study: High Temperature, Low Temperature, Heat Wave, Cold Wave, Extreme Diurnal Temperature Variability, Freeze Thaw, Extreme Heavy Rain, Heavy Rain, Heavy 5-Day Total Rainfall, Rain Frequency, Wet Days, Winter Rain, Freezing Rain, Ice Storm, Heavy Snow, Snow Accumulation, Blowing Snow/Blizzard, Lightning, Hailstorm, Hurricane/Tropical Storm, High Wind, Tornado, Drought/Dry Period, Heavy Fog, Dust Storm, Frost and Acid Rain. Specific definitions for the climate parameters analyzed were established and were based on three factors: a) the usefulness of the climate parameter in determining vulnerability, b) the availability of information, and c) the ability to relate this information to a probability. In addition, two tiers of parameter definitions were established based on the nature of each specific climate phenomenon. Tier one definitions refer to commonly occurring climate phenomena and were defined as the probability of exceeding the historical average occurrence, whereas Tier Two definitions refer to extreme events and were defined as the frequency of occurrence in a given year. The most common time frame used for analysis of historical climate data was 1971 to 2000, as this is the most recent 30-year climate normal period. Wherever possible, the time frame used for future projections was the 30-year period of 2041 to 2070, or more commonly expressed as the 2050s. Assessment of vulnerability beyond this horizon was not conducted as it was agreed among the study team members that this would likely surpass the design life of the infrastructure without the undertaking of significant reconstruction or rehabilitation efforts. The level of uncertainty associated with future climate projections also increases significantly beyond the middle of this century, which would potentially call into question the usefulness of the results. The following Climate Parameters experienced no change in Probability Score from historical to future: Winter Rain, Heavy Snow, Blowing Snow/Blizzard, Lightning, Hailstorm, High Wind, Tornado, Dust Storm, Acid Rain and Heavy Fog. In addition to determining Probability Scores, known or calculated climate parameter frequencies were used as climate loads in the Engineering Analysis phase of the project. The study did not include a detailed hydrologic or hydraulic assessment of the stormwater facilities. A separate study by Cole Engineering Group Ltd is being undertaken to update the Master Stormwater Implementation Plan and Flood Risk Analysis. Through previous studies, the stormwater infrastructure have generally been found to be resilient to a variety of high inflow conditions below design magnitudes. For the purposes of this study, changes to high inflow regimes were examined only from a general, qualitative basis in the assessment in consideration of indirect or secondary effects.

7 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 6 Recommendations Some specific key recommendations from the study are as follows: GTAA should review the emergency operational plans currently in place to ensure they are adequate for all types of climate events rain, snow, ice, high winds. From this review, it would be prudent to extrapolate for the extreme events considered in this assessment to ensure operations personnel are comfortable with the safeguards in place. There were a number of climate-component interactions that had an overall low risk score under both existing and future conditions due to a low probability of occurrence, but for which impacts would be extremely severe. These risk interactions were considered to be important, since the high severities indicated the potential for a critical loss of function; it is therefore advisable to consider the potential impacts and consequences of these high-impact events, and potentially to also develop mitigation or response plans to address them. The main climate conditions involved in these interactions with low risk scores and high severities are extreme heavy rainfalls, tornados, and hurricane/tropical storms. Many of the recommendations of the study are based on assessed risk and vulnerability that are considered to remain the same or become greater as a result of the potential outcomes of climate change. However, assumptions regarding climate change outcomes were based on analysis of current climate understanding and predictive science, which in itself involves a great deal of uncertainty. It is therefore suggested that the recommendations of this study be revisited with updated climate analysis and projections if climate science is able to provide more precision or certainty in the future. Generally, the results of the engineering analysis demonstrate that the stormwater facilities have relatively low vulnerability to potential future climate change. Part of the reason for the relatively low vulnerability is the excellent condition that the stormwater facilities are in; this is due to combination of resilient design, a high quality of construction, consistent inspections and maintenance on the part of GTAA staff. The PIEVC protocol recommends that an adaptive management process be utilized to revisit the vulnerability assessment at defined intervals to incorporate new information including improved climate science and future climate projections. Considering the manner in which the climate analysis and projections portion of this study is organized, and the thorough documentation of the assumptions regarding the use of the information in the risk and vulnerability assessment, incorporating new climate-related information should be a relatively straightforward process. Additional climate parameters may also be incorporated by following the format in which the existing climate parameters are provided. The remaining portions of the study (Risk Assessment and Vulnerability Analysis) have been presented in this document according to the procedures prescribed by the PIEVC Protocol.

8 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 7 Conclusions Having utilized the protocol to assess the stormwater facilities and Spring Creek triple cell box culvert, the project team determined that, in general, the facilities have the capacity to withstand the existing and projected future climate (i.e. to the 2050s). The climate analysis revealed some changes in frequency of climate events that will result in a decrease in vulnerability for the infrastructure. With the generally higher temperatures projected for the study area, there will be less probability, or less frequency of the low temperature dependant events such as freeze/thaw, snow accumulation and cold wave. This reduced frequency of occurrence will result in a decreased potential vulnerability from the events. This can be viewed as a potential positive impact of future climate change. The climate events posing the highest vulnerability to the stormwater facilities, particularly in terms of number of components potentially vulnerable, are generally extreme events such as extreme heavy rainfalls. While this was an expected outcome, it should be highlighted that the current climate science indicates that the possibility of these events occurring is going to increase in the future. Many of the vulnerabilities exist to extreme weather events such as tornados or hurricanes, and while it is difficult to completely protect the infrastructure from events such as these, there are actions which can be taken to minimize the operational risks and prepare for the events. These include: reviewing emergency response plans, and completing operational tests where power, communication and back-up systems are lost. While the overall conclusion of the report is that the stormwater facilities are generally able to withstand expected changes in climate in the future, it will continue to be important to monitor some of the risks and vulnerabilities identified through the assessment, particularly as components continue to age. It will be important to preserve the high standard of maintenance and management that GTAA has devoted to the stormwater facilities to this point. It will also be prudent to monitor the progress in climate science so that if future projections are updated or improved, the infrastructure assessment can be revisited.

9 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 1 Executive Summary Table of Contents Introduction... i PIEVC Engineering Protocol... i Climate Analysis and Projections... v Conclusions... vii 1.0 Introduction Overview Project Objectives Project Scope Project Team Report Layout Project Definition Overview Study Location and Area Geography Jurisdictional Considerations General Description of Infrastructure at Toronto Pearson Study Area Climate Time Frames Used for Analysis Historical Future Assess Data Sufficiency Infrastructure Data Climate Data Data Gathering and Sufficiency Overview Stormwater Facility Infrastructure General Infrastructure Components Infrastructure of Interest Spring Creek Triple Cell Box Culvert Infrastructure General Infrastructure Components Infrastructure of Interest Climate Analysis Objectives... 44

10 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Methodology TRCA Vulnerability Assessment to Climate Change for Flood Control Dams, Toronto s Future Weather & Climate Drivers Study, Toronto s Climate Change Vulnerability Assessment for Culverts, Toronto HydroElectric System Public Infrastructure Engineering Vulnerability Assessment Study, Discussion Regarding Available Climate Data & Projections Process of Probability Scoring Other Potential Changes that May Affect the Infrastructure Assessment of Data Sufficiency Risk Assessment Overview Risk Assessment Methodology Using a Spreadsheet to Document the Risk Assessment Populating Title Columns of the Spreadsheets Yes/No Analysis Populating Header Rows of the Spreadsheets Using Assessment Spreadsheet to Calculate the Risk for Each Relevant Interaction Evaluating Potential Cumulative Effects Risk Assessment Workshop Establish the GTAA s Risk Tolerance Thresholds Rank the Risks Assess Data Sufficiency Infrastructure Data Climate Data Summary of Findings Engineering Analysis Overview Step 4 Engineering Analysis Calculate the Existing Load (L E ) Calculate the Climate Change Load (L C ) Calculate Other Change Loads (L O ) Calculate the Total Load (T E ) Calculate the Existing Capacity (C E ) Calculate the Projected Change in Existing Capacity Arising from Aging/Use of the Infrastructure Calculate Additional Capacity Calculate the Projected Total Capacity (CT) Calculate Vulnerability Ratio... 79

11 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Calculate Capacity Deficit Spring Creek Culvert Assess Data Sufficiency Evaluate Need for Additional Risk Assessment Summary of Findings Complete Engineering Analysis Tables Recommendations Overview Limitations Major Assumptions Conclusions References Infrastructure Climate Data PIEVC Case Study

12 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 4 LIST OF FIGURES Figure 1.1 Climate Change Scenarios for Temperature... 1 Figure 1.2 PIEVC Process... 2 Figure 2.1 Project Definition Process Flowchart... 5 Figure 2.2 General Location of Toronto Pearson... 6 Figure 2.3 Aerial Photo of Toronto Pearson... 7 Figure 2.4 Toronto Pearson Jurisdictional Map... 8 Figure 2.5 Average Temperature at Pearson Airport ( ) Figure 2.6 Extreme Temperature Pearson Airport ( ) Figure 2.7 Precipitation at Pearson Airport ( ) Figure 2.8 Gust Winds at Pearson Airport ( ) Figure 3.1 Data Gathering and Sufficiency Process Flowchart Figure 3.2 Access to electrical system and detention tank for the Aeroquay Facility Figure 3.3 View of SWM6 stormwater detention pond (typical of dry detention ponds) Figure 3.4 View of Pond 2 stormwater detention pond (similar to Pond 4) Figure 3.5 View of Aeroquay Facility s underground storage tank Figure 3.6 Metal weir overflow plates in Cell 1 of the Moore Creek Facility Figure 3.7 Outlet from WM4A Figure 3.8 Cargo diversion chamber bypass in Moore Creek Facility Figure 3.9 Sluice gate for the SWM4 detention pond Figure 3.10 Exterior sluice gate control at Moore Creek Facility Figure 3.11 Oil/water skimmer in the Aeroquay Facility Figure 3.12 The north face of the electrical and instrumentation control building for Moore Creek Facility Figure 3.13 Electrical and instrumentation control panel in the Moore Creek Facility electrical building 27 Figure 3.14 Level indicator electronics in the Moore Creek Facility electrical and instrumental control building Figure 3.15 Gas detector electronics in Moore Creek Facility electrical building Figure 3.16 Gas detector inside Moore Creek Facility tank Figure 3.17 View of berm at Juliet Pond Figure 3.18 Locations of Toronto Pearson Stormwater Facilities Figure 3.19 Carlingview Stormwater Facility, Aeroquay Stormwater Facility and SWM Figure 3.20 Stormwater Pond 6B, Pond 2, and Pond Figure 3.21 Etobicoke Creek Facility and A Figure 3.22 Moore Creek Stormwater Facility and Spring Creek Storage Pond Figure 3.23 July 8, 2013 flooding in vicinity of SWM Figure 3.24 July 8, 2013 flooding in vicinity of SWM Figure 3.25 SWM4, SWM5, and SWM6 Facilities Figure 3.26 WM4A, FedEx Pond and Juliet Pond Figure 3.27 Inlet of Spring Creek Triple Cell Box Culvert Figure 3.28 Looking upstream inside westernmost cell of Spring Creek Triple Cell Box Culvert Figure 3.29 Channel downstream of Spring Creek Triple Cell Box Culvert Figure 3.30 Spring Creek Triple Cell Box Culvert overview Figure 3.31 Projected Change in Monthly Average Rainfall and Snowfall Figure 3.32 Projected Extreme Daily Rainfall Figure 3.33 Projected Change in Wind Figure 3.34 July 8, 2013 Rainfall Total Depth... 54

13 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 5 Figure 3.35 July 8, 2013 Maximum 60 Minute Intensity Figure 3.36 July 8, 2013 Maximum 120 Minute Intensity Figure 4.1 Risk Assessment Process Flowchart Figure 4.2 Summary of Findings Figure 5.1 Engineering Analysis Process Flowchart Figure 5.2 Projected future IDF curves compared to existing 100-year curve Figure 5.3 Model Water Surface Profile of Spring Creek Culvert for the Existing 100 and 350-year Design Storms and the Regional Storm Figure 6.1 Recommendations Process Flowchart LIST OF TABLES Table 2-1 Toronto Climate Normals ( ) Table 2-2 Design Life of Infrastructure Systems Table 3-1 Typical Stormwater Facility Infrastructure Inventory Table 3-2 Spring Creek Triple Cell Box Culvert Components Table 3-3 Summary of Extreme Weather Events for Table 3-4 Projected Future Weather Changes Compared to Recent Weather Table 3-5 Summary of Climate Parameters and Associated Probabilities Table 3-6 Prioritized Reference Documentation for Infrastructure Data Table 4-1 Probability Scale Factors Table 4-2 Severity Scale Factors Table 4-3 Sample Risk Assessment Matrix Table 4-4 Performance Response Considerations Table 4-5 Performance Response Considerations for Stormwater Facilities and Spring Creek Culvert Table 4-6 Workshop Attendees Table 4-7 Risk Tolerance Thresholds Table 4-8- Summary of Findings Table 5-1 Sample Layout of the Engineering Analysis Part Table 5-2 Sample Layout of the Engineering Analysis Part Table 5-3 Sample Layout of the Engineering Analysis Part Table 5-4 Vulnerable Components of the Stormwater Facilities (Vulnerability Ratio >1) Table 5-5 Vulnerable Components of Spring Creek Triple Cell Box Culvert (Vulnerability Ratio >1) Table 5-6 Engineering Analysis for Stormwater Facilities Table 5-7 Engineering Analysis for Spring Creek Culvert Table 6-1 Recommendations for the Vulnerable Components of the Stormwater Quality Control Facilities Table 6-2 Recommendations for the Vulnerable Components of the Stormwater Quantity Control Facilities APPENDICES Appendix A Climate Analysis & Projections Appendix B Risk Assessment Matrices Appendix C Ranked Risk Tables

14 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Introduction 1.1. Overview There is definitive evidence to suggest that the climate has changed, and is continuing to change. Climate change affects infrastructure, creating potential vulnerability in the operation and design of engineered systems. Vulnerability may exist because historic climate data is often used to form the basis of the design for public infrastructure. However, due to a changing climate, historic data used to design critical infrastructure may not reflect the climate of the future. As a result, infrastructure may be vulnerable since it may not have sufficient capacity or resiliency to accommodate the conditions created by the changing climate. Figure 1.1 Climate Change Scenarios for Temperature Source: International Panel on Climate Change (IPCC) Scenarios of Future Climate Driven by Population, Economics, and Technology Adoption The true extent of the effects of climate change may not be seen for several decades, however, given the long life of airport infrastructure, planning decisions must start now to consider these issues. The Greater Toronto Airports Authority (GTAA) decided to undertake a vulnerability assessment of infrastructure at Toronto Pearson International Airport (Toronto Pearson) with respect to the potential impacts from the existing climate and future climate change. GTAA representatives approached Mr. David Lapp of Engineers Canada. Engineers Canada established the Public Infrastructure Engineering Vulnerability Committee (PIEVC) to oversee a national engineering assessment of the vulnerability of Canadian public infrastructure to changing climate. PIEVC has developed a protocol to guide the vulnerability assessments. The PIEVC Protocol is a structured, formalized and documented process for engineers, planners and decision-makers to recommend measures to address the vulnerabilities and risks to changes in particular climate design parameters and other environmental factors from extreme climatic events. The

15 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 2 assessments help justify design, operations and maintenance recommendations and provide documented results that fulfill due diligence requirements for insurance and liability purposes. The Protocol systematically reviews historical climate information and projects the nature, severity and probability of future climate changes and events with the adaptive capacity of an individual infrastructure as determined by its design, operation and maintenance. It includes an estimate of the severity of climate impacts on the components of the infrastructure (i.e. deterioration, damage or destruction) to enable the identification of higher risk components and the nature of the threat from the climate change impact. This information can be used to make informed engineering judgments on what components require adaptation as well as how to adapt them e.g. design adjustments, changes to operational or maintenance procedures. Engineers Canada agreed to allow GTAA to use the PIEVC Protocol (Version 10 - October, 2011) for purposes of assessing its infrastructure. GTAA signed a licensing agreement with Engineers Canada Project Objectives The main objective of this study is to identify those components of infrastructure which are at increased risk of failure, damage, deterioration, reduced operational effectiveness, and/or reduced life cycle from climate changes. The nature and relative levels of risk are to be determined in order to make recommendations for remedial action and/or further study. The vulnerability assessment was based on Version 10, October 2011 of the PIEVC Protocol. There are five steps within the PIEVC Protocol, as shown in the process flowchart in Figure 1.2. Figure 1.2 PIEVC Process

16 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 3 The observations, conclusions, and recommendations derived from the vulnerability assessment can be used to effectively incorporate climate change adaptation in infrastructure design, development, and management. The Protocol provides a process to identify relevant interactions between climate and infrastructure. To assess infrastructure vulnerability to climate change, the following were evaluated: Selected Stormwater Infrastructure; Spring Creek Triple Cell Box Culvert; Historic, Recent, and Projected Climate; and, Historic and Forecasted Responses of the Infrastructure to the Climate. The following sections provide detailed descriptions and results from the completion of the five Protocol steps, as applied to the selected Stormwater Infrastructure and Spring Creek Triple Cell Box Culvert Project Scope There are considerably different types and extents of infrastructure at Toronto Pearson. A single vulnerability assessment study to address the impacts of climate change on all infrastructure at Toronto Pearson would be a massive and complex undertaking. Rather, the GTAA decided to initially undertake a pilot vulnerability assessment study, specifically addressing selected stormwater infrastructure and the Spring Creek Triple Cell Box Culvert. Completing a pilot vulnerability assessment for selected infrastructure allows GTAA to build internal capacity while undertaking the assessment; reviewing the results from the initial assessment; and then plan the next steps in adapting to climate change. The GTAA has made significant investments in its stormwater management infrastructure. The stormwater facilities were implemented coincident with re-development of Toronto Pearson and using up-to-date technologies and best management practices. A previous flood risk analysis study identified low potential for flooding that would cause either damage or delay to airport operations. However, the flood risk analysis studies relied on current stormwater management design criteria and did not account for climate change. The Flood Risk Analysis and Master Stormwater Implementation Plan are being updated separately. The updating of those studies was in part the catalyst to undertaking a vulnerability assessment to address climate change impacts. The Spring Creek Triple Cell Box Culvert is one component of infrastructure at Toronto Pearson that has previously been identified as posing a high flooding risk. It consists of a three cell concrete box culvert with each cell having dimensions 5 m x 3 m. It is located under Runway The culvert was designed to convey the 100-year design storm. The backwater effect caused by a more extreme storm event, such as a Regional Storm, would cause significant flooding risk, potentially overtopping the runway and impacting airport operations. It would also inundate the upstream Derry Road bridge under the jurisdiction of the Region of Peel. It is expected that the flooding risk and impact to operations would be heightened as a result of climate change. This vulnerability assessment study includes an assessment of the vulnerabilities of the facilities to current climate for existing conditions and to future climate change at the 2050 time horizon.

17 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 4 The study did not include a detailed hydrologic or hydraulic assessment of changed inflow regimes or the assessment of the risk of failure as a result of changes in the regime of extreme events Project Team Climate change engineering vulnerability assessment is a multidisciplinary process requiring a wide range of engineering, construction, operation, and maintenance skills and knowledge. Furthermore, the team must include deep knowledge of climatic and weather conditions relative to the project location. GTAA staff provided the primary technical and operations infrastructure knowledge. GTAA staff drove the project and were responsible for identifying and assessing the likely response of the infrastructure to projected climate change. This project was undertaken with internal resources from the GTAA, facilitated and guided by assistance from David Lapp of Engineers Canada and Alan Winter of Cole Engineering Group. Team members were as follows: Name Affiliation Job Title/Project Role Derek Gray GTAA Manager Environmental Services Chris Stewart GTAA Manager, Airside and Infrastructure Engineering Daphne De Souza GTAA Senior Environmental Officer Paul Wajda GTAA Senior Municipal Engineer Steve Thomas GTAA Senior Environmental Technician Alan Winter Cole Engineering Group Ltd. Facilitator John Chadwick Cole Engineering Group Ltd. Climate Specialist Cole Engineering was retained to facilitate the vulnerability assessment process and prepare this report Report Layout This report has been divided into the following main chapters: Section 2 Summarizes Step 1 of the PIEVC Engineering Protocol Project Definition. Section 3 Summarizes Step 2 of the PIEVC Engineering Protocol Data Gathering and Sufficiency. Section 4 This chapter describes Step 3 of the PIEVC Engineering Protocol Risk Assessment of the Stormwater Facilities and Spring Creek Triple Cell Box Culvert. Section 5 This chapter describes Step 4 of the PIEVC Engineering Protocol Engineering Analysis Section 6 This chapter presents the Main Conclusions and Recommendations of the overall study.

18 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Project Definition 2.1. Overview The objective of the first step of the Protocol is to determine the boundary conditions for the vulnerability assessment. This includes developing a description of the infrastructure including: Location of the vulnerability assessment; Infrastructure of concern; Historical climate; Time frames for analysis; Existing loads on the subject infrastructure; Age of the subject infrastructure; Jurisdictional considerations; Other relevant factors; and, Identification of major documents and information sources. Figure 2.1 provides a flowchart delineating the PIEVC process for Step 1 Project Definition. Figure 2.1 Project Definition Process Flowchart At the end of this step, data sufficiency was assessed by identifying proposed assumptions and their rationale Study Location and Area Geography Toronto Pearson is located 25 km northwest of Toronto s central business district in the heart of the southern Ontario region. The Airport is surrounded by a variety of industrial, commercial and residential land uses and is bound by a series of major highways and regional arterial roads. It is generally bounded by Highway 401 to the south, Etobicoke Creek to the west, Derry Road to the north and by Airport Road and Highway 427 to the east.

19 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 6 The general location of Toronto Pearson relative to the surrounding municipalities is shown on Figure 2.2. Figure 2.2 General Location of Toronto Pearson The area of land within the current operational boundary of Toronto Pearson covers 1,867 ha (4,613 acres) and encompasses airside facilities, passenger and cargo terminals, parking, access roads, business aviation, and aviation support facilities. Figure 2.3 presents a satellite image of the airport. The developing watersheds upstream of Toronto Pearson has a significant influence on the flood water flows experienced in the Etobicoke Creek and Spring Creek watercourses that flow through Toronto Pearson. While this geographic feature will not have an impact on the climate parameters, future climate changes may have a significant influence on the creek flood flows.

20 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 7 Figure 2.3 Aerial Photo of Toronto Pearson Due to its favourable location within Canada, Toronto Pearson not only serves those visiting or living within south-central Ontario, but also the growing number of passengers using the Airport as a connecting point for onward journeys. Toronto s central gateway location means that an estimated 60 per cent of North America s population is within a 90-minute flight from Toronto Pearson Jurisdictional Considerations The Protocol requires jurisdictions that are applicable to the infrastructure be identified during the completion of Step 1. These jurisdictions are provided to comply with the Protocol and provide a frame of reference for readers not familiar with the governance structure. More specific laws, regulations and guidelines are identified during completion of Step 2 of the protocol. Toronto Pearson is a federally owned facility that is leased to the GTAA. Because the land is federally owned and airports are federally regulated, the facility falls exclusively under federal jurisdiction. However, not every activity that the airport authority engages in is exempt from provincial legislation. The airport authority may be subject to provincial regulation if it does not impair a vital aspect of the federal undertaking. The following federal legislation has a direct impact on activities of the GTAA at Toronto Pearson: Aeronautical Act and regulations; Navigation Protection Act; Fisheries Act;

21 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 8 Canadian Environmental Assessment Act (CEAA); Canadian Environmental Protection Act (CEPA); Transportation of Dangerous Goods Act; Workplace Hazardous Materials Information System (WHMIS); Canadian Aviation Regulations (CAR); and National Fire Code (NFC). Figure 2.4 Toronto Pearson Jurisdictional Map The following is a description of other relevant authorities and their relationship with GTAA. Provincial Government the province does not have any jurisdiction over GTAA. However, Highway 401 abuts the southerly airport property and Highway 427 abuts the easterly property limit; City of Toronto a portion of Toronto Pearson Airport is within City of Toronto. However, the City of Toronto does not have any legal jurisdiction over GTAA; Region of Peel a representative from Peel Region is a member of GTAA Board of Directors. Derry Road abuts the northerly property limit and there are regional water and wastewater municipal services that traverse the airport property. Toronto Pearson water supply is derived from Peel s Lake Based Water System and the wastewater generated at the airport is disposed in Peel s Etobicoke Creek Trunk Sanitary Sewer System;

22 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 9 Region of York a representative from York Region is a member of GTAA Board of Directors; Region of Durham a representative from Durham Region is a member of GTAA Board of Directors; Region of Halton a representative from Halton Region is a member of GTAA Board of Directors; City of Mississauga a large portion of Toronto Pearson is located within City of Mississauga. However, the City of Mississauga does not have any legal jurisdiction over GTAA; and, Toronto & Region Conservation Authority Etobicoke Creek and Spring Creek both flow through Toronto Pearson Airport and a portion of the airport drains to Mimico Creek. However, TRCA does not have any jurisdiction over GTAA General Description of Infrastructure at Toronto Pearson The following provides a general overview of the infrastructure at Toronto Pearson. Airside Facilities Runways Taxiways and ramps Aprons and aircraft manoeuvring areas Central de-icing facility Toronto Area Control Centre Passenger Terminals Terminal 1 Terminal 3 Infield Terminal

23 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 10 Groundside Transportation Access, Circulation and Parking Above-ground parking surfaces and parking structures Roadways Bridges Tunnels Elevated automated people mover (LINK) Airside and Inter-Terminal Busing Facility and Bus Maintenance Facility Airport Support Facilities GTAA Administration Building Aircraft maintenance Airport security fencing Transport Canada/Peel Regional Police Building Fire and emergency training facilities Wildlife control centre Cogeneration plant Central workshops and stores Central Utilities Plant Various compounds

24 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 11 Air Cargo and Air Carrier Support Facilities Flight kitchens and catering Fuel Tank Farm and re-fuelling facilities Aircraft maintenance hangers and facilities Aircraft waste handling facilities Drainage & Stormwater Management Facilities Catch basins, inlet structures and collection system Storm sewers Culverts Open ditches Stormwater management facilities surface and underground facilities Water quality monitoring equipment Aviation Navigational and Communication Aids Air traffic control tower Toronto Area Control Centre (ACC) Glide Path equipment Localizer equipment Doppler Very High Frequency Omni-Directional Range/Distance Measurement equipment (DVOR/DME) Terminal Surveillance Radar (TSR) Airport Surface Detection equipment (ASDE) Non-directional beacons (NDB) Electronic and visual landing aids Runway and taxiway lighting Runway and taxiway markings Runway and taxiway signage Approach and landing lighting and systems

25 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 12 Business Aviation Area Several hangars Fuelling facilities Fixed base operators Communications Main computer rooms and telecommunication closets Fibre optic, copper and coaxial cables Security system (cameras, doors, intercoms, etc.) Water and Wastewater Potable water supply Fire fighting water supply Wastewater collection and disposal Pumping stations Electrical Power Supply and Distribution Main power feeders Switchyards Load modules Distribution system Control and data acquisition systems Heating and Air Conditioning Heating systems Air conditioning systems

26 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Study Area Climate The climate surrounding Toronto Pearson is typically described as humid continental with warm, humid summers and cold winters. There are four distinct seasons. Accumulating snow can fall any time from November until mid-april. The area is under the influence of the Great Lakes and can experience lakeaffect snow. The summer months are characterized by long stretches of humid weather. Precipitation is fairly evenly distributed throughout the year, but summer is usually the wettest season, the bulk falling during thunderstorms. Generally speaking, spring and summer temperatures range from 15 C to 25 C. During winter months, the average daytime temperature, with the exception of January, the coldest month, hovers just slightly below freezing. The average yearly precipitation is about 793 mm, with an average annual snowfall of about 115 cm. Table 2-1 provides climate normals from Environment Canada for the period The climate normal is referenced instead of the normal because the latter was not readily available during the early stages of this study, and as a result the data was used for the climate analysis. Table 2-1 Toronto Climate Normals ( ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Temperature Daily Average ( C) Daily Maximum ( C) Daily Minimum ( C) Extreme Maximum ( C) Extreme Minimum ( C) Precipitation Rainfall (mm) Snowfall (cm) Precipitation (mm) Average Snow Depth (cm) Snow Depth at Month-end (cm) Extreme Daily Rainfall (mm) Extreme Daily Snowfall (cm) Extreme Daily Precipitation (mm) Extreme Snow Depth (cm) Days With Maximum Temperature > 0 C Measurable Rainfall Measurable Snowfall Measurable Precipitation Source: Environment Canada

27 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 14 The climate analysis and projections component of the study are included as Appendix A of this report Time Frames Used for Analysis This study includes an assessment of the vulnerabilities of the stormwater facilities to current climate for existing conditions and to future climate change at the 2050 time horizon Historical The time frame used for assessment for representation of historical climate data is the period This 30-year period matches the most recent climate normal period readily available from Environment Canada during the time the climate analysis was completed. The climate normals were not made readily available in time to be included in this study. Figure 2.5, Figure 2.6 and Figure 2.7 below display the average temperature, extreme temperature, and precipitation at Toronto Pearson for the period This period of time does not exactly coincide with the historical time period, but the graphs were readily available from the City of Toronto Climate Drivers Study 2012 and clearly show the trends for average temperature, precipitation and wind. Figure 2.5 Average Temperature at Pearson Airport ( )

28 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 15 Figure 2.6 Extreme Temperature Pearson Airport ( ) Figure 2.7 Precipitation at Pearson Airport ( )

29 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 16 Figure 2.8 Gust Winds at Pearson Airport ( ) Future The time frame used for future projections was the 30-year period of 2041 to 2070, or more commonly expressed as the 2050s. Assessment of vulnerability beyond this horizon was not completed in consideration of the design life of the subject infrastructure without the undertaking of significant reconstruction or rehabilitation efforts. The level of uncertainty associated with future climate projections also increases significantly beyond the middle of this century, which would potentially call into question the utility of the results. The estimated design life of the infrastructure systems are provided in Table 2-2. Table 2-2 Design Life of Infrastructure Systems System Administration/Operation Surface Detention Storage Inlet/Outlet Structures Mechanical Systems Embankments Underground Concrete Tanks (Structural) Electric Power Supply Control and Monitoring Systems Communications Safety Systems Design Life years for physical structures Indefinite for personnel, procedures, and records Indefinite 80 years (civil) 50 years > 100 years 80 years 30 years 20 years 10 years 10 years

30 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 17 The systems noted above which have anticipated design lives of 30 years or less will require significant regular upgrades to maintain their serviceability. GTAA has been adequately maintaining these facilities. However, there will be significant maintenance required in the future as the facilities approach the mid point of their anticipated design lives Assess Data Sufficiency Infrastructure Data There were no identified data gaps at this step of the study Climate Data The overall intent of the climate analysis and projections component of this study was to use readily available information to the extent possible. Appendix A contains the climate analysis and projections used in this vulnerability assessment. Much of that climate information has been sourced through the TRCA Vulnerability Assessment study for its two large dams. All assumptions made for the climate related component of this study, along with the rationale used to support those assumptions are also contained in Appendix A.

31 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Data Gathering and Sufficiency Figure 3.1 Data Gathering and Sufficiency Process Flowchart 3.1. Overview The objective of the second step is to identify the specific features of the infrastructure to be considered in the assessment as well as the applicable climate information. In this step, data was acquired from the multiple sources identified in Step 1. The acquired data was then assessed for sufficiency Stormwater Facility Infrastructure General Infrastructure Components A general list of the major infrastructure systems associated with the Stormwater Facilities and their breakdown into individual components is provided in Table 3-1. It is noted that each stormwater facility has its own unique infrastructure components and not all components listed in Table 3-1 are associated with every stormwater facility.

32 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 19 Table 3-1 Typical Stormwater Facility Infrastructure Inventory System Component Administration/Operation Personnel (maintenance/inspection) Procedures (maintenance/inspection) Emergency procedures Access to facility Access on-site Records Detention Basin Reinforced concrete tank Dry storage pond Facility building (structure only) Inlet/Outlet Structures Inlet Ditch Diversion Diversion bypass outlet Outlet Concrete weir Sanitary connection Mechanical Systems Oil/water separator Interior actuators Exterior actuators Pumps HVAC Potable water line Sluice gate valve Electric Power Supply Electrical panel Lighting Backup power Control and Monitoring Gas detection system Systems PLC/SCADA system Fire alarm Level indicators Facility alarms (Active 8 System) Communications Phone line Two-way radio Cellular phone Safety Systems Berm Administration/Operation The administration and operations were broken into seven components; personnel (maintenance/ inspection), procedures (maintenance/inspection), emergency procedures, access to facility, on-site access and records. The personnel include the GTAA employees responsible for the management, operation, and maintenance of the stormwater facilities. The ability of personnel to safely and effectively operate the infrastructure during severe weather is important to the operation of the stormwater facilities as a complete system.

33 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 20 Records refer to all hard copies and controlled/original electronically stored documents relating to the operation of the infrastructure. Operating procedures refer to all procedures related to the operation of the stormwater infrastructure, including standard operating procedures and procedures for operation during emergencies. Figure 3.2 Access to electrical system and detention tank for the Aeroquay Facility Detention Basins The sub-components of detention basins are either dry surface ponds and/or underground storage tanks. The majority of the stormwater facilities have dry surface facilities, but Aeroquay, Carlingview and Moore Creek facilities have underground reinforced concrete storage tanks.

34 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 21 Figure 3.3 View of SWM6 stormwater detention pond (typical of dry detention ponds). Figure 3.4 View of Pond 2 stormwater detention pond (similar to Pond 4)

35 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 22 Figure 3.5 View of Aeroquay Facility s underground storage tank Inlet/Outlet Structures All of the stormwater facilities have inlets and outlets. Inlets structures consist of storm sewers, ditches or diversion structures. Outlet structures consist of storm sewers, sanitary sewers, bypass structures and overflow weirs.

36 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 23 Figure 3.6 Metal weir overflow plates in Cell 1 of the Moore Creek Facility Figure 3.7 Outlet from WM4A

37 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 24 Figure 3.8 Cargo diversion chamber bypass in Moore Creek Facility Mechanical Systems Mechanical components include oil/water separators, pumps, piping, sluice gate valves, HVAC and actuators. The mechanical equipment for some stormwater facilities are below ground or in a controlled environment. Some mechanical equipment is outside and exposed to the elements of weather.

38 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 25 Figure 3.9 Sluice gate for the SWM4 detention pond Figure 3.10 Exterior sluice gate control at Moore Creek Facility

39 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 26 Figure 3.11 Oil/water skimmer in the Aeroquay Facility Embankments Most stormwater facilities are constructed considering the surrounding topography and sited in a relatively low-lying area. However, in order to provide the necessary storage volume, some facilities have earthern berms or embankments.

40 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 27 Electric Power Supply Figure 3.12 The north face of the electrical and instrumentation control building for Moore Creek Facility Figure 3.13 Electrical and instrumentation control panel in the Moore Creek Facility electrical building

41 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 28 Control and Monitoring Systems Figure 3.14 Level indicator electronics in the Moore Creek Facility electrical and instrumental control building Figure 3.15 Gas detector electronics in Moore Creek Facility electrical building

42 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 29 Figure 3.16 Gas detector inside Moore Creek Facility tank Communications Communications consist of three main components; land-based telephone, cellular, and two-way radio. Safety Systems The safety system is broken down into three components; fencing, platforms, and security fences. Fences are used principally to restrict the entrance to the airside. Platforms are used for worker access to the facility or its operating equipment.

43 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 30 Figure 3.17 View of berm at Juliet Pond Sources of information for infrastructure data included the following documents: Stormwater Management Master Plan LBPIA Operations Manual for the Carlingview Stormwater Management Facility Jan. 1999; Carlingview Environmental Management Facilities, O&M Manual, 2007; Carlingview Stormwater Facility Maintenance Procedures AMMS Etobicoke Creek Stormwater Control Facility Operations and Maintenance Manual 1 and 2, and Mechanical Maintenance Manual; LBPIA Facility Operations Manual for the Etobicoke Creek Stormwater Control Facility Jan (online); Etobicoke Stormwater Facility Maintenance Procedures AMMS Moore Creek Stormwater Facility Instrumentation Maintenance Manual 1 and 2, and Mechanical Maintenance Manual; Moore Creek SWF Electrical Manual; Moore Stormwater Facility Maintenance Procedures AMMS GTAA Aeroquay Stormwater Management Facility Operations and Maintenance Manual Vol 1&2 March 2003; Active 8 System O&M Manual; Aeroquay Stormwater Facility Maintenance Procedures AMMS WM4 Operation and Maintenance Manual GTAA Stormwater Facilities Automatic Control Programs Control Narrative April 2007 Stormwater SCADA System O&M Manual, April 2009 Fuel, Gas, Sanitary, Storm, Fire and Water Services; Reduced Record Drawings, 2008 Specific Stormwater Pond Drawings

44 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Infrastructure of Interest Figure 3.18 delineates the location of stormwater facilities throughout Toronto Pearson. A brief description of each facility follows: Figure 3.18 Locations of Toronto Pearson Stormwater Facilities Note: Boeing Stormsewer does not exist and is not part of the stormwater facilities at Toronto Pearson.

45 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 32 Carlingview Stormwater Facility This facility is located east of Highway 427, constructed underground, under a parking lot. The facility was initially constructed in 1996 and expanded in It consists of reinforced concrete storage tanks with a total 17,000m 3 of capacity for stormwater quality and erosion control purposes. The stormwater facility also provides fuel, oil and grease removal facilities. The contributing drainage area is ha. The design criteria used for sizing the underground tank was the capture and storage of runoff volume from a 25 mm rainfall event from within the catchment area. The runoff that drains to the Carlingview SWM Facility originates from the old Terminal 2, Terminal 2 apron area and the fuel tank farm. The facility discharges to a trunk storm sewer which outlets to Mimico Creek. Runoff in excess of the storage capacity by-passes the facility and discharges directly to a sanitary sewer. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure Aeroquay Crescent Stormwater Facility This facility was constructed underground and consists of an underground reinforced concrete storage tank with a volume of 7,000m 3 to provide stormwater quality and erosion control. It was constructed in The ha contributing drainage includes the Terminal 1 Building and parking garage area. The design criteria used for sizing this underground tank volume was the capture and storage of runoff volume from a 25 mm rainfall event from within the catchment area. The facility discharges to a trunk storm sewer which outlets to Mimico Creek. Runoff in excess of the storage capacity by-passes the facility and discharges directly to Mimico Creek. A quick-connect connection was recently retro-fitted that allows contaminated water to be easily extracted from the facility and disposed elsewhere. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure SWM16 Facility This facility consists of a dry surface facility with storage volume 11,240m 3 to provide stormwater quantity and erosion control. It was constructed in The contributing drainage area is ha. The catchment area includes the area between South Perimeter Road and the ends of Runways 24L and 24R. The design criteria used for sizing this surface pond was the runoff volume from a 25 mm rainfall for water quality and erosion control. The 100-year design storm was used for sizing the quantity control portion of the facility. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure 3.18.

46 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 33 Figure 3.19 Carlingview Stormwater Facility, Aeroquay Stormwater Facility and SWM16 Carlingview Stormwater Facility Aeroquay Stormwater Facility SWM16 Pond Stormwater Pond 6B, Pond 2, and Pond 4 After the GTAA took over responsibility for Highway 409 west of Highway 427, the highway was widened. These SWM facilities were constructed in 1998 and 1999 to control the stormwater quantity, quality and erosion potential of runoff into Mimico Creek. The associated contributing drainage area is ha. A SWM facility is located in Area 6B with a storage volume of 11,220m 3 to treat combined runoff from Area 6A and 6B. That facility is sized for water quality, and erosion control (25 mm rainfall event) as well as stormwater quantity control (100-year design storm). The balance of quantity control storage is provided in two of the four quadrants of the Highway 409 and Highway 427 interchange. The combined volumes for Pond 2 and Pond 4 is 10,620m 3. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure 3.18.

47 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 34 Figure 3.20 Stormwater Pond 6B, Pond 2, and Pond 4 Pond 4 Pond 2 Pond 6B Etobicoke Creek Stormwater Facility This facility was initially constructed in 1998 and expanded in The facility has been sized to receive all stormwater runoff from the new terminal and apron area, the central de-icing facilities, and parts of the south infield. This represents a total drainage area of ha. The new terminal and apron areas account for ha of the total drainage area. The facility has a storage volume of 56,300m 3 that provides dry surface detention storage with an artificial wetland for polishing. The design criterion used for sizing the Etobicoke Creek Stormwater Facility was the storage of the first 25 mm of runoff volume from impervious areas. All stormwater flow in excess of this is diverted directly to Etobicoke Creek. The sewer systems entering the facility are equipped with stormceptors. The Etobicoke Creek Stormwater Facility holds storm runoff as required when concentrations of glycol exceed the discharge standards of Etobicoke Creek. A connection is provided to the sanitary sewer for conveying stormwater with high concentrations of glycol to the Region of Peel Lakeview Treatment Plant. A general overview of the facility is provided in Figure The location of the facility within Toronto Pearson is provided in Figure A14 Facility This facility is a dry facility with a storage volume of 4,920m 3, providing stormwater quality and erosion control for a contributing drainage area of 48.8 ha. It was constructed in The design criteria used

48 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 35 for sizing the facility was the capture and storage of runoff volume from a 25 mm rainfall event. All stormwater flows in excess of this event are discharged to Etobicoke Creek, after cresting an overflow spillway. The area that contributes runoff to Stormwater Facility A14 comprises a portion of Runway 06R/24L, related airfield development, and a portion of the Airside Service Road. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure Figure 3.21 Etobicoke Creek Facility and A14 Etobicoke Creek Stormwater Facility A14 Moore Creek Stormwater Facility and Spring Creek Surface Facility This facility provides storage for the first 25 mm of rainfall volume for water quality and erosion control purposes. It was constructed in ,000m 3 is provided by the underground tanks, and 42,000m 3 provided in two separate surface detention ponds (Moore Creek and Spring Creek storage ponds). The underground tank consists of three storage cells. Stormwater enters the first cell, then cascades to the second and third, until the capacity is reached (12.5 mm of rainfall). Rainfall in excess of 12.5 mm bypasses the tank via a set of overflow weirs, and flows first into the Moore Creek surface detention pond (total capacity 26,000m 3 ). Overflow from this pond flows to the Spring Creek surface detention pond, which has a capacity of 16,000m 3. Rainfall in excess of 25 mm will bypass the storage facilities and flow directly to Spring Creek. A weir spillway and emergency spillway are provided to relieve flows in excess of the Spring Creek surface pond capacity.

49 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 36 These stormwater facilities capture and control the runoff generated from the Terminal 3 and apron area, parts of Runway 33R/15L, parts of Taxiway Hotel and the air cargo facilities. The total contributing drainage area is ha. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure Figure 3.22 Moore Creek Stormwater Facility and Spring Creek Storage Pond Moore Creek Stormwater Pond Moore Creek Stormwater Facility Spring Creek Storage Pond SWM4 Facility This facility consists of a dry type surface stormwater quantity control facility with a storage volume of 26,700m 3. It was constructed in The contributing drainage area is ha. The SWM facility controls the outflow to meet downstream storm sewer capacity constraints of 2.0m 3 /s (as per agreement with City of Mississauga). SWM4 was designed for the 100-year design storm event. In addition, 10,000m 3 of surface storage capacity is provided in the grassed area between existing Runway 06-24R and Taxiway D5. SWM4 does not have any freeboard associated with its storage capacity and any flow in excess of the 100-year design storm will cause ponding and flooding in the surrounding area. Figure 3.23 depicts the flooding that occurred on July 8, 2013 in the vicinity of SWM 4.

50 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 37 Figure 3.23 July 8, 2013 flooding in vicinity of SWM 4 The area that contributes runoff to SWM4 Facility comprises the GTAA administrative and maintenance facilities, including GTAA corporate administrative offices, a fire hall, Peel Regional Police/Transport Canada building, central workshops, hangar, aprons, parking lots and ground maintenance buildings. Figure 3.24 depicts the flooding that occurred on July 8, 2013 in the vicinity of Convair Drive.

51 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 38 Figure 3.24 July 8, 2013 flooding in vicinity of SWM5 SWM 5 Facility This facility consists of a dry type surface stormwater quantity control facility with a storage volume of 4,900m 3. It was constructed in The contributing drainage area is 19.4 ha. SWM5 was designed for the 100-year design storm event. The SWM facility controls the outflow to meet downstream storm sewer capacity constraints of 0.80m 3 /s. SWM5 does not have any freeboard associated with its storage capacity and any flow in excess of the 100-year design storm will cause ponding and flooding in the surrounding area. The area that contributes runoff to SWM5 Facility comprises the Airside Service Road and the groundside service road. A general overview of the facility is provided in Figure The location of the facility within Toronto Pearson is provided in Figure SWM6 Facility This facility consists of a dry type surface stormwater quantity control facility with a storage volume of 24,800m 3. It was constructed in The contributing drainage area is ha. SWM6 was designed for the 100-year design storm event. The SWM facility controls the outflow to meet downstream storm sewer capacity constraints of 0.7m 3 /s. SWM6 does not have any freeboard associated with its storage capacity and any flow in excess of the 100-year design storm will cause ponding and flooding in the surrounding area.

52 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 39 The area that contributes runoff to SWM6 Facility comprises Runway 06R/24L, taxiways, related airfield development, and the Airside Service Road. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure Figure 3.25 SWM4, SWM5, and SWM6 Facilities SWM4 SWM5 SWM6 A2 FedEx Facility This facility is a dry type surface facility with a storage volume of 6,500m 3, which provides stormwater quality and erosion control. It was constructed in It does not provide stormwater quantity control. The contributing drainage area is ha. The design criteria used for sizing the facility was the runoff volume from a 25 mm rainfall event. This stormwater facility essentially services the FedEx Distribution Facility and apron area. A general overview of the facility is provided in Figure This facility controls stormwater runoff from the business aviation facilities, Runway 15L approach area, and parts of Juliet. It was constructed in The ultimate drainage area is ha. The WM4A Stormwater Facility is for stormwater quality control and treats runoff from a 25 mm rainfall event.

53 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 40 WM4A Facility The WM4A Stormwater facility provides a storage volume of 19,400 m 3. All stormwater flow in excess of this event is discharged to Spring Creek, after cresting an overflow spillway. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure Figure 3.26 WM4A, FedEx Pond and Juliet Pond WM4A FedEx Pond Juliet Pond Juliet Stormwater Pond This facility is a dry type surface facility with a storage volume of 4,500m 3, which provides stormwater quality and erosion control. It was constructed in All stormwater flows in excess of this event are discharged to Spring Creek, after cresting an overflow structure. It does not provide storm water quantity control. The contributing drainage area is ha. The catchment area includes the Menkes Site, Skeet Club and Apron area. The design criteria used for sizing the facility was the runoff volume from a 25 mm rainfall event. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure 3.18.

54 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Spring Creek Triple Cell Box Culvert Infrastructure General Infrastructure Components A breakdown of the Spring Creek Triple Cell Box Culvert into individual components is provided in Table 3-2. Table 3-2 Spring Creek Triple Cell Box Culvert Components System Administration/Operation Structural System Embankment Component Personnel (Maintenance/Inspection) Procedures (Inspection/Maintenance) Emergency Procedures Access to culvert On-site access Security Access - gate access Records Upstream concrete Apron Upstream rip-rap Downstream apron Downstream rip-rap Upstream wingwall Downstream wingwall Cell structures Expansion joints Construction joints Baffles (for fish migration) Parapet walls 1050 culvert inlet Embankment Administration/Operation The administration and operations were broken into seven components; personnel (maintenance/ inspection), procedures (maintenance/inspection), emergency procedures, access to facility, on-site access and records. The personnel include the GTAA employees responsible for the management, operation, and maintenance of Spring Creek Triple Cell box Culvert. The ability of personnel to safely and effectively operate the infrastructure during severe weather is important to the operation of the airport as a complete system. Records refer to all hard copies and controlled/original electronically stored documents related to the operation of the infrastructure.

55 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 42 Operating procedures refer to all procedures related to the operation of the culvert including standard operating procedures and procedures for operation during emergencies. Figure 3.27 Inlet of Spring Creek Triple Cell Box Culvert Figure 3.28 Looking upstream inside westernmost cell of Spring Creek Triple Cell Box Culvert

56 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 43 Figure 3.29 Channel downstream of Spring Creek Triple Cell Box Culvert Infrastructure of Interest Spring Creek Triple Cell Box Culvert This culvert is located on Spring Creek, directly downstream from Derry Road. It was originally constructed in 1969 to convey Spring Creek under Runway 05/23 and the Taxiway Hotel extension. The structure consists of three separate concrete box culverts in parallel. Each culvert is 5.1m wide by 3.05m high and was originally 450m long. In 2001 Spring Creek culvert was extended northerly by 115m to accommodate extension of Taxiway Juliet. In 2012 the northern part of the culvert was retrofitted to provide additional support to the north portal wing walls. The culvert was designed to convey the 100-year design storm. Recent hydraulic analysis of Spring Creek reveals that the Regional Storm exceeds the conveyance capacity of the structure and will overtop the embankment and Runway 05/23. A general overview of the facility is provided in Figure The location of the facility within the Toronto Pearson is provided in Figure 3.18.

57 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 44 Figure 3.30 Spring Creek Triple Cell Box Culvert overview Spring Creek Triple Cell Box Culvert 3.4. Climate Analysis Objectives The objectives of the climate analysis and projections portion of this study were to: Establish a set of climate parameters describing climatic and meteorological phenomena relevant to Toronto Pearson Airport; and, Establish a general probability for the occurrence of each phenomenon, both historically and in the future. The term historical is defined as comprising both the existing climate as well as climate from the recent past, while the term future is defined as representing the 2050s.

58 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Methodology The List of Climate Variables A list of climate variables was developed based on climate events and change factors identified in Appendix A of the Protocol as indicated below: High Temperature Heavy 5-Day Total Rainfall Lightning Low Temperature Winter Rain Hailstorm Heat Wave Freezing Rain Hurricane/Tropical Storm Cold Wave Ice Storm High Wind Extreme Diurnal Temperature Variability Heavy Snow Tornado Freeze Thaw Snow Accumulation Drought/Dry Period Heavy Rainfall Blowing Snow/Blizzard Heavy Fog Extreme Heavy Rainfall Rain (Frequency) Acid Rain Frost Wet Days Dust Storm It was recognized at the outset of this study that other recently completed climate change studies could provide suitable climate data for use in this study. Mr. David Lapp of Engineers Canada suggested some other PIEVC studies could provide reliable climate information. Using climate data and information from other studies, potentially could reduce or eliminate the need to generate new climate projections for the Toronto Pearson study. Climate data from four recently completed studies were scrutinized, with a view to deciding whether that data would be appropriate and adequate for the Toronto Pearson study: 1. National Engineering Vulnerability Assessment to Climate Change for Flood Control Dams, Toronto and Region Conservation Authority (TRCA), December Toronto s Future Weather & Climate Drivers Study, City of Toronto, December Climate Change Vulnerability Assessment for Culverts, City of Toronto, December Toronto Hydro-Electric System Public Infrastructure Engineering Vulnerability Assessment Study, TRCA Vulnerability Assessment to Climate Change for Flood Control Dams, 2009 The TRCA study was guided by the PIEVC Protocol and developed a list of climate parameters based on climate events and change factors included in Appendix A of the Protocol. The list was further developed and revised into a more comprehensive list based on climatic and meteorological phenomena deemed to be relevant to the geographic region (southwestern Ontario) and the region s known seasonal variability. Factors dictating the selection of climate parameters, and the indices used to express them, were based on data availability of several standard meteorologically-accepted parameters in consideration of both the historical/existing record as well as future projection model output. Justification for parameter selection was also based on the parameter s potential to present

59 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 46 vulnerability to the infrastructure and its components as a result of either an extreme or persistent occurrence. Information was retrieved from Environment Canada s Canadian Climate Normals, Climate Data Online (Environment Canada, 2008), the Ontario Node of the Canadian Atmospheric Hazards Network (Environment Canada, 2009) and the Canadian Daily Climate Data (CDCD V1.02) program (Environment Canada, 2007). For these data sources, Toronto Pearson weather station data was used. Future climate projections were analyzed using climate model outputs from Environment Canada s Canadian Climate Change Scenario Network (CCCSN) Scatter Plots (CCCSN, 2007b) and Bioclimate Profiles (CCCSN, 2007a), the Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (AR4, 2007) Regional Climate Projections chapter, and scientific journal articles presenting regional and local projections and predictions. The exercise of calculating the probability of an event s occurrence (for both current and future) was already compiled in the TRCA report. A score between 0-7 was assigned to each parameter, as guided by the PIEVC Protocol. The TRCA study contained many of the climate parameters of interest to the GTAA for conducting the Toronto Pearson Vulnerability Assessment. The relevant climate analysis and projections component of TRCA large dams study is included in Appendix A of this current report. Appendix A is not a strict replication of the TRCA climate analysis and projection component, since modifications were made to various climate parameter definitions and climate parameters in addition to TRCA s study have been included in the Toronto Pearson study. Climate Specialists from Cole Engineering assisted in the development and modification of various climate parameters Toronto s Future Weather & Climate Drivers Study, 2011 The objective of the City of Toronto Weather & Climate Drivers Study was to better understand what currently influences Toronto s weather and climate. Once those influences were determined, it was necessary to know how those influences are likely to change and how severe the consequences are likely to be in the future. The City of Toronto was not content with relying exclusively on Global or Regional Climate Models (GCM or RCM) due to their coarseness of grid scale. In addition, the City wanted to use climate extremes rather than averages. The City s reasoning is that operation of critical infrastructure such as the electrical grid, water treatment plants, sewers and culverts, public transport and roads are sensitive to particular temperature and weather thresholds. Beyond these thresholds infrastructure may have reduced capacity or may not function at all. The City wanted to use local weather modeling at a much finer resolution, i.e. using 1x1 km gridded data, to include the influences of local features rather than 50x50 km coarse gridded data, "driven" by GCM/RCM model output. The study adopted a modelling approach using nested models. The results from the British Meteorological Office Hadley Centre climate model (HadCM3) were inputted into a medium resolution RCM (PRECIS) to provide results that were inputted into a fine resolution weather-climate model (FReSH). A present climate of was developed using the modelling approach, as well as a future climate of Climate projections were generated for Toronto Pearson, along with 35 other locations around the GTA.

60 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 47 The approach of adding a weather model to the climate model output to obtain more locally relevant future prediction forecasts was new and innovative when that project was conceived. The main climate parameters that were studied were: Temperature; Precipitation; Wind; and, Humidity Table 3-3 is extracted from the City of Toronto Climate Drivers Study. It summarizes Extreme Weather Events for the period These weather events are not specific to the Toronto area, but are interesting to recall and reflect upon. These weather events were not captured in the currently published Environment Canada s Climate Normals ( ). Table 3-3 Summary of Extreme Weather Events for Year Record Events 2000 Wettest summer in 53 years with 13% more precipitation than normal Driest growing season in 34 years; first ever heat alert; 14 nights with temperatures above 20 C (normal is 5 nights) Driest August at Pearson Airport since 1937; warmest summer in 63 years; fifth coldest Spring Rare mid-spring ice storm Pearson Airport used a month s supply of glycol de-icer in 24-hours Year without a summer; May rainfall in Hamilton set an all-time record; and another all-time record 409 mm rainfall was set at Trent University in July which was equivalent to 14 billion litres of water in 5 hours (a 200 year event) Warmest January 17 since 1840; January 22nd blizzard with whiteouts; warmest June ever; number of Toronto days greater than 30 C was 41 (normal is 14); August 19 storm washed out part of Finch Avenue tornadoes across Ontario (14 normal); record year of major storms; record one-day power demand of 27,005 MW due to summer heat Protracted January thaw; 2nd least snow cover ever in Toronto (half the normal amount); snowiest Valentine s Day ever; chunks of ice fell from CN Tower; 2-3 times the normal number of hot days in the summer; record latest-in-season string of +30 C days around Thanksgiving Toronto s 3rd snowiest winter ever; record for highest summer rainfall rd rainiest February in 70 years; Hamilton had a 100-year storm; one of the wettest summers on record; tornados hit Vaughan-Woodbridge area in late August; an unusually mild and storm-free November in Toronto Downtown had a record "no snow" for the first time ever first snow-free November at Pearson Airport since Toronto's earliest ever official heat wave (June 19-21) Also Three 1 in 100-year storms in Toronto in less than 13 years: July 2000, August 2005, July 2013.

61 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 48 Some of the findings from the Climate Drivers Study follow: On average in , warmer annual average temperatures of 4.4 o C are expected. For seasonal averages winter temperatures are projected to increase by 5.7 o C and summer temperatures by 3.8 o C. Extreme daily maximum temperatures are projected to increase by 7.6 o C, but extreme daily minimum temperatures are projected to also rise by 13 o C (i.e., becomes less cold). Less snow and more rain in the winters (26 fewer snow days per year) and fewer rainstorm events per year are anticipated. However, the model predicts more extreme rainstorms and marked rainfall increases in July (80%+) and in August (50%+). Precipitation - Snow and Rain Less snow and more rain in the winter 26 fewer snow days per year, 9 less in December Slightly more precipitation (snow plus rainfall) overall Marked rainfall increases in July (80%) and August (50%) Extreme rainstorm events, fewer in number but more extreme Precipitation amounts are projected to remain similar to the present for about 8 months of the year but increase markedly in July and August (with 80% and 50% increases caused by extra rainfall over present values respectively). The number of days with rain greater than 25 mm is projected to decrease while the total precipitation is projected to increase. This means that the future will see a smaller number of storm events but on average each will produce a higher amount of precipitation than occurs today. Hot and Cold Temperatures Average annual temperatures increase by 4.4 C. The projected average winter temperature increase by 5.7 C. The projected average summer temperature increase by 3.8 C. The extreme daily minimum temperature "becomes less cold" by 13 C. The extreme daily maximum temperature "becomes warmer" by 7.6 C. Winds Wind speeds will be unchanged on average Maximum wind speeds will be reduced This suggests more vertical and less horizontal motion developing stronger convective storms (in summer) meaning that there will be more clear skies and calmer periods between storms.

62 Difference in Amount Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 49 Figure 3.31 summarizes the changes expected to occur between the period and the period Figure 3.31 Projected Change in Monthly Average Rainfall and Snowfall Source: Toronto s Future Weather & Climate Drivers Study, Pearson Airport: Change to Rainfall (mm) Snowfall (cm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

63 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 50 Table 3-4 Projected Future Weather Changes Compared to Recent Weather Source: Toronto s Future Weather & Climate Drivers Study, 2011

64 Difference in Wind Speed in km/h Amount in mm Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 51 Figure 3.32 Projected Extreme Daily Rainfall Source: Toronto s Future Weather & Climate Drivers Study, Pearson Airport: Extreme DAILY Rainfall Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Figure 3.33 Projected Change in Wind Source: Toronto s Future Weather & Climate Drivers Study, 2011 Pearson Airport: Change to Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Average Speed (km/h) Max Hourly Speed Max Gust Speed

65 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Toronto s Climate Change Vulnerability Assessment for Culverts, 2011 The climate analysis and projections required for that study followed a similar methodology as developed for the TRCA PIEVC assessment of the two large dams. The two large dams and the culverts are located in the Toronto area, and the historical data analyzed for the TRCA study remains valid, and therefore the City of Toronto utilized a similar approach. While the TRCA study used a review of numerous predictions for the future projections, the City of Toronto study used climate projection data from the City s Climate Drivers Study. Where required projection data was not available from the Climate Drivers Study, the results from the TRCA s PIEVC study for the two large dams was used Toronto HydroElectric System Public Infrastructure Engineering Vulnerability Assessment Study, 2012 Toronto Hydro-Electrical System Limited (THESL) used parts of the PIEVC protocol to complete a study they referred to as a pilot case study. The purpose of that study was to evaluate the impact of existing climate on select parts of their distribution and transmission infrastructure. The study differed from typical PIEVC studies because it focused only on the effect of the current climate and did not incorporate a future climate projection to assess how a changing climate may impact their infrastructure. In addition, the Toronto Hydro-Electric study did not proceed beyond Step 3 of the PIEVC Protocol process. The existing climate was defined by a list of parameters that were suspected to have a negative impact on the infrastructure. For the most part, these parameters were adapted from the TRCA study of the two large dams. Threshold definitions were changed in some cases to better reflect the sensitivities of distribution and transmission infrastructure. For example, the availability of temperature related design capacities prompted a change in definition of the high temperature threshold. These electrical specific thresholds would not be as well suited for stormwater facilities (Toronto Pearson study). A different approach was also taken in assigning probability scores that would not be compatible with the Toronto Pearson stormwater infrastructure. The time period used to determine probability scores was the service life of the infrastructure, while the Toronto Pearson study used a constant period of one year. Since the THESL study did not include a projection of the future climate and their thresholds had limited applicability to stormwater facilities, it was decided that it would be better to use a more fulsome source such as the TRCA study Discussion Regarding Available Climate Data & Projections The deliberations on sourcing the climate information and data involved meetings with the TRCA and City of Toronto staff responsible for the previous studies. This allowed for a clearer understanding of the climate data and assisted in the decision making process. While the climate data from the City s Climate Driver study is appealing, it was generally considered that there could be additional costs associated with generating specific data for climate parameters that were not readily available from the study (see long list of climate variables in Section ). On the other hand, the probability scoring required by the PIEVC Protocol had been completed in the TRCA study and seemed appropriate. The TRCA climate

66 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 53 data set seemed to offer all the climate parameters that the GTAA was interested in evaluating and there would likely not be any further cost associated with accessing the information. One other point that influenced the final decision to use the TRCA climate data was the methodology and approach used in the PIEVC Protocol. Specifically, the Protocol lends itself to a step-by-step process that if, in the future, the GTAA decides to update the vulnerability assessment and use a different climate data set, another data set could readily be substituted for the original data set, at the time of study update. Therefore, the primary source of climate data was the TRCA Vulnerability Assessment to Climate Change for Flood Control Dams. Data and information from the City of Toronto Climate Drivers study was also used in this study, as it provided some specific data related to climate parameters that were useful in Step 4 (Engineering Analysis). It is noteworthy that two significant meteorological events occurred during the course of undertaking this vulnerability assessment study. An extreme rainfall event occurred on July 8, 2013 resulting in a total rainfall amount of 126mm falling in about seven hours at Toronto Pearson. Working collaboratively with the City of Toronto, City of Mississauga, and the Region of Peel, Cole Engineering analyzed real time data from rainfall gauges deployed throughout the area. Figure 3.34 shows the total rainfall contours resulting from that storm. Toronto Pearson received the greatest amount of total rainfall from that storm event. Figure 3.35 and Figure 3.36 show the rainfall intensity contours for the 60 minute and 120 minute durations. These figures show that the Toronto Pearson vicinity received the highest rainfall intensity. Analysis has concluded that storm was a 1:100-year event. Toronto Pearson sustained considerable flooding throughout the airport and damages are still being remedied.

67 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 54 Figure 3.34 July 8, 2013 Rainfall Total Depth

68 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 55 Figure 3.35 July 8, 2013 Maximum 60 Minute Intensity

69 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 56 Figure 3.36 July 8, 2013 Maximum 120 Minute Intensity

70 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 57 The second significant event commenced on December 22, 2013 when two freezing rain storms hit Southern Ontario over three days, resulting in an ice storm covering the Greater Toronto Area. The steady dose of freezing rain across much of Southern Ontario turned roads and sidewalks into skating rinks, cut power to hundreds of thousands of people, and played havoc with holiday plans at one of the busiest travel times of the year. Toronto Pearson realized flight delays and cancelations. Ground crews worked under extreme weather conditions to continue operations.

71 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Process of Probability Scoring The probability scoring process is outlined in Appendix A and follows the same process used for the PIEVC based vulnerability assessment of flood control dams completed by the TRCA, Several other recent PIEVC Vulnerability Assessments have also used the same process (adapted from the TRCA study). Table 3-5 summarizes the climate parameters used in this study and the associated probabilities for existing and future climate. Table 3-5 Summary of Climate Parameters and Associated Probabilities Category Climate Parameter GTAA Climate Probabilities Parameter Definitions Ex. 'P' Fu. 'P' Projection Source Temperature High Temperature Day(s) with a max. temp exceeding 35 C 4 5 TRCA PIEVC Study Low Temperature Day(s) with a min. temp below -30 C 3 2 TRCA PIEVC Study Heat Wave Three or more consecutive days >32 C 4 5 TRCA PIEVC Study Cold Wave Diurnal Temperature Variability Three or more consecutive days with min temp. <-20 C and max temp. < -10 C 3 2 TRCA PIEVC Study Daily temp. variation of more than 25 C 3 2 TRCA PIEVC Study Freeze/Thaw 85 or more freeze-thaw cycles within one year 4 2 TRCA PIEVC Study Frost 175 or more frost days within one year 4 3 Literature Review Heavy Fog 15 or more hours with visibility <0km within one year 4 4 TRCA PIEVC Study Wind High Wind/Downburst 8 or more days with max. winds of >=63km/hr in one year 4 4 TRCA PIEVC Study Tornado Vortex extending upward from the earth's surface at least as far as cloud base (occurring near site) 1 1 TRCA PIEVC Study Precipitation Extreme Heavy Rainfall Days with rainfall > 125mm 1 2 TRCA PIEVC Study Heavy Rainfall Days with rainfall > 50mm 4 5 TRCA PIEVC Study Rain (Frequency) 23 or more days of >10mm of rain within one year 4 5 Literature Review Heavy 5 day total Rainfall A five day period receiving >100mm of rainfall 2 3 TRCA PIEVC Study Winter Rain/Rain-on- Snow Greater than 25mm of rain falling during January, February and March 4 4 TRCA PIEVC Study Freezing Rain 9 or more days with freezing rain in one year 4 6 TRCA PIEVC Study Ice Storm Severe freezing rain events 2 3 TRCA PIEVC Study Snow Storm/Blizzard 8 or more days with blowing snow in one year 4 4 TRCA PIEVC Study Heavy Snowfall Days with snowfall >10cm 6 6 TRCA PIEVC Study

72 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 59 Category Climate Parameter GTAA Climate Probabilities Parameter Definitions Ex. 'P' Fu. 'P' Projection Source Snow Accumulation 5 or more consecutive days with a snow depth of >30cm 6 5 TRCA PIEVC Study Hailstorm Days with precipitation falling as ice particles (dia. >5mm) 5 5 TRCA PIEVC Study Acid Rain Precipitation with ph of <4 2 2 Literature Review Wet Days 112 or more days with measureable rainfall >0.2mm in one year 4 5 Literature Review Other Lightning lightning strikes on the airport property within one year 3 3 TRCA PIEVC Study Hurricane/Tropical Storms Cyclones of a tropical origin with sustained surface wind speeds >63km/hr 1 2 TRCA PIEVC Study Drought/Dry Periods 10 consecutive days with <0.2mm of precipitation 5 6 TRCA PIEVC Study Dust Storm Visibility <1 km for more than an hour 2 2 Literature Review Other Potential Changes that May Affect the Infrastructure Changes in use pattern that increase or decrease the capacity of the infrastructure are: Upstream and/or downstream development and land use change; and sedimentation of the stormwater facilities. Operation and maintenance practices that increase or decrease the capacity or useful life of the infrastructure are: Pre-emptive maintenance for concrete structures such as crack repair, spalling concrete repair; Pre-emptive maintenance for steel work such as sandblasting, reinforcement and re-painting; Lubrication of mechanical components for gates and controls; Inspection and replacement of wear components in mechanical and electrical equipment; and, Periodic inspection by maintenance personnel on a defined schedule. Changes in management policy that affect the load pattern on the infrastructure are: Changes in stormwater facility operation protocol and procedures. Changes in laws, regulations, and standards that affect the load pattern on the infrastructure are: Possible changes to the regulatory flood requirements or stormwater management criteria.

73 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Assessment of Data Sufficiency Infrastructure Data The amount of infrastructure data gathered was sufficient in this step, and appeared to be of good quality and accuracy. No data gaps were identified at this stage. The prioritized referenced documentation for the infrastructure data is provided in Table 3-6 with general priority given to the most recent documentation/data. Table 3-6 Prioritized Reference Documentation for Infrastructure Data Priority Referenced Documentation 1 Engineering Drawings 2 Design Reports 3 Operations, Maintenance records 4 Maintenance Information including Equipment Manuals and Inspection Reports Climate Data The data gaps, data quality, data accuracy, application of trends, reliability of selected climate models, and the reliability of climate change assumptions are all discussed in Appendix A. 4.0 Risk Assessment 4.1. Overview The objective of the third step is to identify the interactions between the infrastructure, the climate, and any other factors that could lead to vulnerability. This includes identifying specific infrastructure components, specific climate change parameter values, and specific performance goals. An engineering vulnerability exists when the total load effects on infrastructure exceed the total capacity to withstand them, while meeting the desired performance criteria. Where the total loads or effects do not exceed the total capacity, adaptive capacity exists. Step 3 of the PIEVC Protocol involved the identification of infrastructure components which are likely to be sensitive to changes in specific climate parameters. This step focuses on qualitative assessments as a means of prioritizing more detailed Evaluation Assessment of Engineering Analysis in Step 4 of the Protocol. Professional judgment and experience was used to determine the likely effect of individual climate events on individual components of the infrastructure. To achieve this objective, the Protocol uses an assessment matrix process to assign an estimated probability and an estimated severity to each potential interaction. Figure 4.1 provides a flowchart of the process of Step 3. Risk Assessment Methodology: The default method uses a scale of 0 to 7 to establish the probability of each of the climate infrastructure interactions occurring and the severity

74 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 61 resulting from the interaction. The product of the probability and severity of the interaction is used to develop a risk value for each of the climate infrastructure interactions. Risk Tolerance Thresholds: Once the risks are calculated, tolerance thresholds have to be identified. The risk tolerance thresholds determine what risk range can be classified as low, medium, or high risk. Risk Ranks: The relationships between the infrastructure and its environment are prioritized to identify areas where vulnerability to existing climate and to potential future climate change exists. Components from the risk interactions that are identified as medium are considered further analysis in the Engineering Analysis in Step 4. These components will be the ones that show some vulnerability but that cannot be confirmed at this stage to be highly vulnerable or insensitive to a changing climate. Data Sufficiency: It is determined if assessment of specific components require data that is not currently available. If such a scenario is encountered, we will re-examine Step 1 and/or Step 2 to obtain sufficient data, if possible, to continue the assessment. If the data is not available and obtaining it is out of the scope of the Study then such findings will be documented in the recommendations made in Step 5. Figure 4.1 Risk Assessment Process Flowchart

75 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Risk Assessment Methodology To determine a value for the risk associated with an interaction between an infrastructure component and a climate related event, the protocol dictates that the probability of the event occurring is multiplied by the severity of the impact to determine the overall risk value. To develop a risk value for each infrastructure-climate interaction, scales of 0 7 are established for the probability of the interactions occurring and the severity resulting from the interaction. The Protocol provides three alternate methods; A, B, and C (shown in Table 4-1) for using the probability scale. Method A was selected for this assessment. For the severity scale, the Protocol provides two methods; D and E as shown in Table 4-2 Method E was selected for this assessment. Methods A and E were selected as they were based on non-numerical criteria, which merged well with Step 3 since it is more qualitative in nature than quantitative. It was felt that the numerical scales provided in the alternative methods would require a level of precision and accuracy that could not be supported by available data regarding climate probability and impact severity.

76 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 63 Table 4-1 Probability Scale Factors Scale Probability Method A Method B Method C 0 Negligible or not applicable <0.1% or <0.1/20 Negligible or not applicable 1 Improbable/Highly Unlikely 5% or 1/20 Improbable 1: Remote 20% or 4/20 Remote 1: Occasional 35% or 7/20 Occasional 1: Moderate/Possible 50% or 10/20 Moderate 1: Often 65% or 13/20 Probable 1:100 6 Probable 80% or 16/20 Frequent 1:10 7 Certain/Highly Probable >95% or >19/20 Continuous 1:1 Table 4-2 Severity Scale Factors Scale Method D Method E Severity 0 No effect Negligible or Not Applicable 1 Measurable Very Low/Unlikely/Rare/Measurable Change 2 Minor Low/Seldom/Marginal/Change in Serviceability 3 Moderate Occasional Loss of Some Capability 4 Major Moderate Loss of Some Capacity 5 Serious Likely Regular/Loss of Capacity and Loss of Some Function 6 Hazardous Major/Likely/Critical/Loss of Function 7 Catastrophic Extreme/Frequent/Continuous/Loss of Asset

77 Structural Design Infrastructure Functionality Serviceability Watershed, SW, and GW Operations & Maintenance Emergency Response Insurance Considerations Policy Considerations Social Effects Environmental Effects Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Using a Spreadsheet to Document the Risk Assessment A spreadsheet was developed that comprised a header row for relevant climate events. The title columns consist of relevant infrastructure systems and components, and their performance response to relevant climate change effects. Two separate matrices were established using the above noted spreadsheet for each facility to include both the existing and future risks. A sample spreadsheet for a stormwater facility is shown in Table 4-3. The complete matrices for all stormwater facilities and the Spring Creek Triple Cell Box Culvert are included in Appendix B. Table 4-3 Sample Risk Assessment Matrix Temperature Infrastructure Response Consideration High Temperature Low Temperature Heat Wave Infrastructure Component Day(s) with a max. temp exceeding 35 C Day(s) with a min. temp below -30 C Three or more consec utive days >32 C Administration/ Y/N P S R Y/N P S R Y/N P S R Operation Component Example Detention Basin Y/N P S R Y/N P S R Y/N P S R Component Example Inlet/Outlet Structures Y/N P S R Y/N P S R Y/N P S R Component Example 4.4. Populating Title Columns of the Spreadsheets The title column of the matrices was populated with the list of infrastructure systems and components. Performance response categories were established based on the most likely response of an infrastructure component to contemplated climate events. The performance response categories were based on professional judgment and experience. It is important to identify the performance response categories as it defines the associated risk. For example, the occurrence of a high temperature event for personnel is not a risk. However, its effect on personnel not being able to respond in emergency situations is a risk. The performance category for the above mentioned example would be emergency response, which is important to the analysis as it defines the risk.

78 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 65 The following performance response categories were considered in Table 4-4: Table 4-4 Performance Response Considerations Performance Response Keyword Potential Infrastructure Response Structural Design (Design) Safety Load carrying capacity Overturning Sliding Fracture Fatigue Serviceability Deflection Permanent deformation Cracking and deformation Vibration Foundation design considerations Infrastructure Functionality (Functionality) Level of effective capacity (short, medium, long term) Equipment (component selection, design, process and capacity considerations) Infrastructure performance (performance) Level of service, serviceability, reliability Materials performance Watershed, Surface Water, and Groundwater Erosion along watercourse (Environment) Erosion scour of associated/supporting earthworks Sediment transport Channel realignment/meandering Change in water quantity Change in water quality (water quality) Change in water resources demands Change in groundwater recharge Change in thermal characteristics of water resource Operations and/or Maintenance Structural aspects Equipment aspects Functionality and effective capacity Emergency Response (Emergencies) Storm, flood, ice, water damage Insurance Considerations (Insurance) Rates Policy Considerations (Policies) Codes Public sector policy Guidelines Intergovernmental communications Social Effects (Social Effects) Relevant social effects

79 Structural Design Infrastructure Functionality Serviceability Watershed, SW, and GW Operations & Maintenance Emergency Response Insurance Considerations Policy Considerations Social Effects Environmental Effects Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 66 A summary of the identified performance response considerations for the corresponding infrastructure components for the selected stormwater facilities and Spring Creek Triple cell box culvert is provided in Table 4-5. Table 4-5 Performance Response Considerations for Stormwater Facilities and Spring Creek Culvert Infrastructure Response Consideration Infrastructure Component 4.5. Yes/No Analysis The next step of the process is to assess the potential for adverse interactions between each climate parameter and each infrastructure component. At this stage of the process, the team is not assessing the magnitude of the risk. Rather, this is a second stage of screening. If the team determines that there can be an adverse interaction between a climatic parameter and an infrastructure component, the interaction is retained within the process for further risk analysis. If the team determines that there may be no material adverse impact, the interaction is eliminated from further risk assessment analysis Populating Header Rows of the Spreadsheets The header row of the matrices was populated with the list of climate parameters provided in Section Definitions for each of the climate parameters were also provided below the header row. Under each climate parameter, title sub-columns were created as follows: Y/N (Yes/No). This field is marked Y if there is an expected interaction between the infrastructure component and the climate effect, and N if not. Relevant or irrelevant for further consideration. P (Climate Probability Scale Factor). This value reflects the probability of the respected climate variable occurring within the time horizon of the vulnerability assessment. S (Response Severity Scale Factor). This value reflects the expected severity of the interaction between the climate phenomena and the infrastructure component. R (Risk Score). This is calculated as P multiplied by S. This risk value is used to determine how the interaction will be assessed in the next steps of the Protocol. The value of R is also helpful in determining the priority of recommended actions, but is not to be solely relied on.

80 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Using Assessment Spreadsheet to Calculate the Risk for Each Relevant Interaction Instead of assessing the severity scale factor of each performance response for individual infrastructure components, all the performance responses that were relevant were check marked, and only one severity scale factor was applied. The severity scale factor that was applied was based on judgment of the performance response that was most critical to the individual infrastructure-climate interaction. The cells under the P column were populated as described in Section 3 (Section 3.4, Climate Parameters) and Appendix A, under the Probability Scoring subsections for each climate parameter. A summary table of the probability scores is provided in Table 3-6. The cells under the S column were populated using engineering judgment from GTAA staff with specific knowledge of the infrastructure. The Risk for each infrastructure-climate interaction was calculated using the following equation: R = P x S Where: R = Risk P = Probability of the interaction S = Severity of the interaction The final risk assessment matrices are included in Appendix B Evaluating Potential Cumulative Effects The cumulative impact of combining or sequencing climate events was evaluated to assess the possibility of these combined events yielding a higher compound event. However, since the information available for the individual climate events was limited, it was identified early on that it would be even more difficult to obtain information on a combination of the individual climate events, especially in a future scenario. Nevertheless, it is noted that the severities would increase for combined events. The following climate parameters that were evaluated may be considered as combined/sequenced events: Heat Wave consecutive days of high temperature Cold Wave consecutive days of low temperature Extreme Diurnal Temperature Variability difference between extreme high and low temperature Freeze Thaw sequence of diurnal temperatures varying between above freezing and below Heavy 5-Day Total Rainfall consecutive days of heavy rain Winter Rain combination of heavy rain and low temperatures, frozen ground or snow on ground Freezing Rain combination of rain and below freezing temperatures Ice Storm combination of heavy rain, below freezing temperatures Blowing Snow combination of snow (on ground or falling) and high wind

81 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 68 Snow Accumulation sequence of heavy snow events Hail normally occurs in combination with heavy rain and high wind Hurricane/Tropical Storm combination of heavy rain and high wind 4.9. Risk Assessment Workshop This evaluation was complemented by a Risk Assessment Workshop which was held at the FESTI facility at Toronto Pearson on October 9, This gathering brought together representatives from the Engineers Canada, Transport Canada, Toronto and Region Conservation Authority, Credit Valley Conservation, City of Mississauga, Region of Peel and others. The workshop consisted of an overview presentation by Derek Gray of GTAA, David Lapp of Engineers Canada on the PIEVC Protocol and Ryan Ness of TRCA on the climate information. All participants were provided with a workbook, which included the workshop agenda, selected presentation slides, scale factors, and the risk assessment matrices. The workshop participants were split into two groups, and each group had the task of assessing Spring Creek Triple Box Culvert. That facility was deemed a Special Case and it was considered worthy of further assessment by workshop participants. Due to time limitations, each group worked only on the assigned infrastructure components of the matrix. A list of participants is provided in Table 4-6. Table 4-6 Workshop Attendees Name Affiliation Project Role/Job Title Derek Gray GTAA Manager Environmental Services Chris Stewart GTAA Manager, Airside Infrastructure and Engineering Daphne De Souza GTAA Senior Environmental Officer Paul Wajda GTAA Senior Municipal Engineer Mike Riseborough GTAA Director Aviation Infrastructure, Energy and Environment Steve Thomas GTAA Senior Environmental Officer Marcos Zambrano GTAA Environmental Technician Randy McGill GTAA Associate Director, Corporate Sustainability Marc St Jean GTAA Associate Director, Business Performance, Aviation Services David Lapp Engineers Canada Manager, Professional Practice Rebecca Earl Transport Canada Communications Advisor Chandra Sharma TRCA Watershed Specialist, Etobicoke-Mimico & Senior Manager, Climate Programs Don Haley TRCA Ryan Ness TRCA Manager Water Resources CVC Lincoln Kan City of Mississauga Manager, Environmental Services Jeremy Blair City of Mississauga Storm Drainage Programming Engineer John Nemeth Shawn Taylor Jeff Hirvonen Region of Peel Dillon Alan Winter Cole Engineering Facilitator

82 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 69 The groups were constructed with the following considerations, where possible: Management and Operations staff were assigned to separate groups; Each group had a member who was well versed with the climate analysis; and, Each group had a moderator and a recorder Establish the GTAA s Risk Tolerance Thresholds The risk tolerance thresholds were reviewed, and are provided in Table 4-7. These thresholds are the same as those provided in the Protocol. While the Protocol provides default thresholds, it is important to note that they are not fixed. There was discussion around the possibility of altering these thresholds, however in the end it was decided that the thresholds suggested in the Protocol would be used. Upon review of the risk assessment, the thresholds appeared reasonable. Table 4-7 Risk Tolerance Thresholds Risk Range Threshold Response <12 Low Risk No immediate action necessary Medium Risk Action may be required Engineering Analysis may be required >36 High Risk Immediate action required Low risk interactions represent no immediate vulnerability. Based on professional judgment, the potential climate change vulnerability associated with the infrastructure component is very low. Therefore, no further action is necessary. Medium risk interactions characterize a potential vulnerability. Based on professional judgment, the potential climate change vulnerability associated with the infrastructure component does exist, and further engineering analysis may be necessary to provide a clear determination of the vulnerability. High risk interactions characterize an identified vulnerability. Based on professional judgment, the potential climate change vulnerability associated with the infrastructure component is identified, and immediate action may be required. As noted, the qualitative nature of the risk assessment process is based on engineering and professional judgment. The documented results represent a consensus amongst the workshop participants for a particular interaction. However, the initial discussion on a specific climate variable infrastructure component interaction would usually begin with some participants reflecting opinions of a lower severity and others a higher severity.

83 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Rank the Risks Complete and Comparison matrices are provided in Appendix B Each matrix includes the existing risk score, the future risk score, and the difference between the existing and future risk scores. Furthermore, all the medium risk interactions are highlighted in yellow. The low risk interactions are those that are not highlighted. No high risk interactions were identified in this assessment. A summary of the findings is provided in Table 4-8. Figure 4.2 shows graphically the ranking of facilities according to level of risk. Appendix C contains a full summary of the ranked risks according to each facility Assess Data Sufficiency Infrastructure Data Since Step 3 was more qualitative in nature, the data available for assessment use was sufficient, particularly where non-numerical, engineering and other professional judgment-based screening was applied Climate Data The historical climate analysis and future climate projections were conducted using data from the TRCA PIEVC study, as listed in Table A-4. Toronto Pearson weather station data were used. All assumptions are clearly stated within Appendix A and the TRCA PIEVC Study Final Report.

84 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Summary of Findings Table 4-8- Summary of Findings Total Infrastructure Risk Interactions Carlingview Facility Moore Creek Facility Etobicoke Creek Facility Spring Creek Culvert Low Risk Interactions Medium Risk Interactions High Risk Interactions Flagged Interactions* Existing Future Existing Future Existing Future Existing Future Aeroquay Facility Existing Future Pond 2 Existing Future Pond 4 Existing Future SWM6 Pond Existing Future SWM4 Pond Existing Future WM4A Pond Existing Future Juliet Pond Existing Future B Pond Existing Future FedEx Pond Existing Future SWM5 Pond Existing Future SWM16 Pond Existing Future SWMA14 Pond Existing Future TOTAL Existing Future * Note: Flagged Interactions are when P=1 and R=7 and vice versa.

85 Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Existing Future Number of Interactions Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 72 Figure 4.2 Summary of Findings Carlingview Facility Moores Facility Etobicoke Creek Facility Spring Creek Culvert Total Interactions Low Risk Interactions Medium Risk Interactions High Risk Interactions Existing Risk Future Risk Aeroquay Facility Pond 4 Pond 2 SWM6 Pond SWM4 Pond WM4A Pond Juliet Pond 6B Pond FedEx Pond SWM5 Pond SWM16 Pond

86 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 73 The following points summarize the risk assessment findings for: The risk assessment identified 4378 interactions as low risk interactions for existing conditions and 4063 for future conditions. There were 1442 medium risk interactions identified for existing conditions and 1757 identified for future conditions. No interactions were identified as high risk for existing or future conditions. It was identified in the risk assessment that 457 interactions that were identified as low risk for the existing conditions, but which changed to medium risk for future conditions, as a result of climate change, based on current understandings. On the other hand, there were 142 interactions that were identified as medium risk for the existing conditions, but which decreased to a low risk score for future conditions, as a result of climate change, based on current understandings. The interaction between storage facility and heavy rain received the highest risk score for both existing and future conditions. The interactions with the greatest risk scores in ranked order are provided in Appendix C.

87 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Engineering Analysis 5.1. Overview The objective of the fourth step is to assess the impact on the infrastructure and its capacity from the projected climate change loads. This includes a focused engineering analysis on the relationships determined to have medium vulnerability to climate change in Step 3. Figure 5.1 Engineering Analysis Process Flowchart provides a visual of the Step 4 process. Figure 5.1 Engineering Analysis Process Flowchart When the infrastructure has insufficient capacity to withstand the loads placed on it, it is considered to be vulnerable; it is resilient when the capacity is sufficient. The total loading of the infrastructure is calculated by combining the existing loads and future loads from climate change and other factors, using the following formula: LT = LE + LC + LO, Where: LT is the projected total load on the infrastructure LE is the existing load on the infrastructure LC is the projected load on the infrastructure resulting from climate change LO is the projected load on the infrastructure resulting from other changes

88 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 75 The total capacity is calculated by combining the existing capacity with any changes in the future as the infrastructure matures, or as retrofits or upgrades provide additional capacity, using the following formula: CT = CE - CM + CA, Where: CT is the projected total capacity of the infrastructure CE is the existing capacity of the infrastructure CM is the projected change in infrastructure capacity as a result of age / use CA is the projected additional capacity of the infrastructure The total loading and total capacity can then be used to calculate important indices such as the Vulnerability Ratio (VR) and the Capacity Deficit (CD), as follows: Vulnerabilities occur when VR is greater than 1 and when VR is less than 1, the infrastructure component has adaptive capacity. The capacity deficit is the required amount of capacity that must be added to the infrastructure to mitigate the vulnerability Step 4 Engineering Analysis The infrastructure-climate interactions that scored a risk value between 12 and 36 in Step 3 were analysed further under this step. The analysis included a determination of the relationship between the loads placed under both existing and potential future conditions on the infrastructure and its capacity. The results of this step are provided in Table 5-6 and Table 5-7 located at the end of this chapter. These Engineering Analysis Tables consist of the following fields: Infrastructure Component: lists all components that are included in interactions with risk scores between 12 and 36. Climate Variable: lists all climate parameters corresponding to the infrastructure components that are included in interactions with risk scores between 12 and 36. Basis of Determination/Data Source: provides a definition, description, justification, or data source upon which the values in the cells are based upon. Existing, Climate, Other, and Total Loads Existing, Maturing, Additional and Total Capacities Vulnerability Capacity Deficit Comments/Data Sufficiency

89 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 76 A sample of the Engineering Analysis table is provided in three parts by Table 5-1, Table 5-2 and Table 5-3. Table 5-1 Sample Layout of the Engineering Analysis Part 1 Infrastructure Component Administration/Operations Personnel Climate Parameter Existing Load (L E) Calculation of Total Load (L T) Climate Load Timeframe L C Other Load L O Total Load L T = L E + Lc + L O High Temperature >0 n/a > 0.75 Basis of Determination/Data Source Day(s) with a max. temp exceeding 35 C Projected increase Probability increase from '4' to '5' Freezing Rain ~ >0 n/a >1.25 Basis of Determination/Data Source 9 or more days with freezing rain in one year Projected increase Probability increase from '4' to '6' Table 5-2 Sample Layout of the Engineering Analysis Part 2 Infrastructure Component Administration/Operations Climate Parameter Existing Capacity C E Calculation of Total Capacity (C T) Maturing Capacity C M Additional Capacity C A Total Capacity CT = C E - C M + C A Personnel High Temperature C E> L T n/a n/a C T> L T Basis of Determination/Data Source Engineering Judgement Engineering Judgement Freezing Rain C E> L T n/a n/a C T> L T Basis of Determination/Data Source Engineering Judgement Engineering Judgement Table 5-3 Sample Layout of the Engineering Analysis Part 3 Infrastructure Component Administration/Operations Personnel Climate Parameter Vulnerability (VR) V R = L T/C T Capacity Deficit (CD) C D = L T - C T High Temperature V R< 1 0 Basis of Determination/Data Source Engineering Judgement Engineering Judgement Freezing Rain V R< 1 0 Basis of Determination/Data Source Engineering Judgement Engineering Judgement Comments/Data Sufficiency Personnel may experience some discomfort but will likely still be able to perform their usual duties. Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed.

90 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 77 The following sections provide more information on the parameters involved in this step of the Protocol Calculate the Existing Load (L E ) The existing load was based on the historic probabilities determined using the methods documented in Section 3, and applied in Section 4, Risk Assessment. The value of the existing load was the number of occurrences per year that corresponded to the historic probability determined for the interactions. If a specific value was available for the number of occurrences, then that value was considered the existing load. However, if no specific value was available then an estimate was provided by selecting the high value from the range of number of occurrences that corresponded to the probability score assigned to that interaction. As shown in the example provided in Table 5-1 the number of occurrences of high temperature, as defined in Appendix A is Hence, this value of 0.54 was used as the existing load. However, in the case of freezing rain, no specific value was provided from the analyses documented in Appendix A for the calculated number of occurrences. It was assigned a probability score of 4, and justified accordingly. In this case, the high value from the range of number of occurrences per year corresponding to a probability of 4 was used. Table A-1 shows that the range of number of occurrences per year corresponding to a probability of 4 is 0.25 to Therefore, the high value of the range i.e was used as the existing load. The high value of the range was selected since it represented the worst case scenario, which would result in a more conservative analysis Calculate the Climate Change Load (L C ) The intention of the climate change load parameter is to provide a numerical value that describes how a specific climate parameter changes as a result of climate change. Obtaining an exact value however proved to be difficult since available literature rarely projected information in a form that was compatible with the climate parameters used by this study. Previous PIEVC vulnerability assessments approached this difficulty by providing an estimate of the climate change load based on the future probability score assigned and its corresponding number of occurrences range. In this study however, no estimate of the climate change load was provided. Instead, the climate change load simply indicated whether the climate parameter would increase, decrease, or remain the same based on the climate analysis. If an exact value was available then it would be used, however no exact values were available from the climate analysis. This method was preferred over the previous method since it better represented the accuracy of the climate change load. The validity of the new method was deemed appropriate since it did not change the end result of the vulnerability ratios. As shown in the example provided in Table 5-1, the future probability score for high temperature was increased from the historic probability of a 4 to a 5. In this case, the climate change load was entered as >0 to demonstrate that high temperature events are expected to occur more frequently in the future. Similarly, if an event was expected to occur less frequently then the climate change load would be entered as <0 and as zero if no change in frequency is expected. The rationale for this methodology is consistent with the one used for the calculation of the existing load. The climate change loads for all the interactions included within Step 4 are provided in Table 5-6 and Table 5-7 located at the end of this chapter.

91 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Calculate Other Change Loads (L O ) Other change loads refer to the change in load arising from other change effects on the infrastructure. An example of an other change load would be the intensification or development of the area upstream of the Spring Creek Triple Cell box culvert. Since it was difficult to represent other change loads in the same manner, or unit, as the existing and climate change loads i.e. based on probabilities, generally no quantifiable value could be assigned Calculate the Total Load (T E ) The total loading of the infrastructure is calculated by combining the existing loads and future loads from climate change and other factors, using the following formula: LT = LE + LC + LO, Where: LT is the projected total load on the infrastructure LE is the existing load on the infrastructure LC is the projected load on the infrastructure resulting from climate change LO is the projected load on the infrastructure resulting from other changes As previously mentioned, the climate change load (LC) was generally not assigned an exact value in order to better represent its accuracy. For similar reasons, and out of necessity, a new method was developed to calculate the total load. The total load was calculated based on the future probability score assigned. Depending on whether the probability increased or decreased, the total load was stated to be greater or smaller than the appropriate occurrence range limit corresponding to the future probability score. As shown in Table 3-5, the probability of high temperature is expected to increase from a 4 to a 5. A probability score of 5 describes climate parameters that occur between 0.75 to 1.25 times per year. Based on this occurrence range, the total load was entered as >0.75. This method was thought to better reflect the accuracy of the total load and was deemed appropriate since it did not impact the final vulnerability ratios Calculate the Existing Capacity (C E ) Since it was difficult to represent the existing capacity of the components in the same manner or units as the existing and climate change loads i.e. based on probabilities, no quantifiable value could be assigned. A qualitative description was provided, where available, in the Engineering Analysis Tables. An example is provided in Table Calculate the Projected Change in Existing Capacity Arising from Aging/Use of the Infrastructure Similar to the existing capacities, it was difficult to represent the maturing capacities in the same manner or units as the existing and climate change loads i.e. based on probabilities. Therefore no

92 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 79 quantifiable value was assigned, instead a qualitative description was provided, where available. An example is provided in Table Calculate Additional Capacity The additional capacities were also difficult to quantify based on probabilities, which were used to quantify the loads. A qualitative description was provided, where available, in the Engineering Analysis Tables. An example is provided in Table Calculate the Projected Total Capacity (CT) The total capacity is calculated by combining the existing capacity with any changes in the future as the infrastructure matures, or as retrofits or upgrades provide additional capacity, using the following formula: CT = CE - CM + CA, Where: CT is the projected total capacity of the infrastructure CE is the existing capacity of the infrastructure CM is the projected change in infrastructure capacity as a result of age / use CA is the projected additional capacity of the infrastructure For this study, the total capacity was qualitatively described as being either greater or less than the total load, based on engineering judgment. The capacities were determined based on whether the infrastructure component is able to withstand the current climate conditions, and the response of the infrastructure to similar climate events that have occurred in the past, which are represented by the existing loads. The change in load was then compared to the existing load, and if the change was not considered to be relatively significant, then the infrastructure was determined to have adaptive capacity. Similarly, engineering judgment was applied to all the subsections that follow, where it has been indicated that a qualitative assessment was carried out. The qualitative assessment is provided in Table 5-6 and Table 5-7 located at the end of this chapter. Examples are provided in Table Calculate Vulnerability Ratio The Protocol dictates that the total loading and total capacity be used to calculate the Vulnerability Ratio (VR), as follows: Due to the difficulties in calculating the capacities of the infrastructure components, the vulnerability ratio could not be quantitatively calculated but was based largely on engineering judgment and understanding of the historic performance of the stormwater facilities and Spring Creek culvert.

93 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 80 Therefore, the vulnerability ratio was qualitatively assessed on being either greater or less than one. If the total capacity was estimated to be greater than the total load, then the vulnerability ratio was listed as less than one. A vulnerability ratio of less than one means that the infrastructure component was resilient and not vulnerable to the climate parameter. If the total capacity was estimated to be less than the total load, then the vulnerability ratio would be greater than one, indicating that vulnerability exists. Examples are provided in Table 5-3. The vulnerability ratios for all the interactions requiring engineering analysis are provided in Table 5-6and Table 5-7 located at the end of this chapter. Components that are considered vulnerable are summarized in Section Calculate Capacity Deficit The total loading and total capacity is also used to calculate the Capacity Deficit (CD), as follows: The Capacity Deficit is the difference between the total load and the total capacity. As discussed in Section 5.1 if the total load is greater than the total capacity, then there exists a capacity deficit. A capacity deficit always exists where there is vulnerability, i.e. a vulnerability ratio of greater than one. For this study, since there was no quantitative data for the total capacity, the capacity deficit could not be quantified. If the vulnerability ratio was greater than one, then the capacity deficit was stated to be greater than zero. The capacity deficit was given a value of zero if the vulnerability ratio was less than one. Examples are provided in Table Spring Creek Culvert In light of observations made during the July 8th 2013 extreme rainfall event and analysis available from hydraulic models, Spring Creek Culvert was suspected to have a higher risk associated with extreme heavy rainfalls than the risk matrices indicated. Regardless of the risk scoring, a decision was made to perform an engineering analysis on the culvert specifically for extreme rainfall events. It is noted that this diverges from typical protocol since the severity was only ranked a 5 and the future probability a 2. However, this divergence was deemed appropriate given the above stated information. As previously discussed, future climate projections anticipate rainfalls will be less frequent in general but will be more intense when they do occur. Consequently, extreme rainfall events may occur more frequently. For Spring Creek Culvert, this means that its capacity will likely be tested more often and in some cases exceeded. Spring Creek Culvert currently has sufficient design capacity to convey a 100-year design storm. Climate change projections indicate that the 100-year storm will likely occur more frequently in the future. IDF curves developed by Toronto s Future Weather and Climate Driver Study Volume 1 suggest that by the 2050 horizon the 100-year storm may occur every 25 years for short duration storms and every 5 years for long duration storms (see Figure 5.2) A frequency shift of this size would have a major impact on the performance of the culvert and would also introduce complications upstream.

94 Intensity (mm/hr) Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 81 Figure 5.2 Projected future IDF curves compared to existing 100-year curve IDF Comparison Current 100 yr Future 100 yr Future 25 yr Future 5 yr Future 100 yr Future 25 yr Future 5 yr Duration (hours) Source: Toronto s Future Weather and Climate Driver Study Volume 1 The hydraulic model developed for Spring Creek Culvert suggests that a 100-year storm will not exceed the capacity of the culvert or cause any significant problems upstream (refer to Figure 5.3). However, the 350-year storm is expected to exceed the capacity of the culvert, and although it is not expected to overtop the runway, it will likely overtop Derry Road upstream. In the future, the 100-year storm may be similar in intensity to the current 350-year storm and would consequently bear the above-mentioned risks.

95 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 82 Figure 5.3 Model Water Surface Profile of Spring Creek Culvert for the Existing 100 and 350-year Design Storms and the Regional Storm

96 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 83 It is also important to mention that the current hydraulic model assumes there are no obstructions in the culvert cells. During a 100-year storm, it is conceivable that debris from upstream could block one of these cells, resulting in a reduced capacity. Based on the analysis outlined above, Spring Creek Culvert was considered to be vulnerable to extreme heavy rainfall events in the future. This vulnerability is provided in Table 5-7 at the end of this chapter Assess Data Sufficiency In general, data was insufficient, to complete the engineering analysis in the specific method prescribed by the Protocol. In determining the climate load from the results of the Climate Analysis and Projections, the units were generally represented as a number of occurrences per year, or a probability of the event occurring in a given year. This definition allowed the calculation of the existing load and the climate load, however made the determination of the capacity of a component impossible in any meaningful, scientific way. For example, it is impossible to determine how many ice storms the wooden deck or the sluice gate at SWM 4 could withstand in a given year, or to put any number to the capacity of the electrical supply grid to a tornado. In light of the above, experience and professional engineering judgment was utilized to estimate whether or not the component was vulnerable to a singular occurrence or multiple occurrences of the climate parameter. This resulted in a qualitative assessment of vulnerability Evaluate Need for Additional Risk Assessment The need for reassessing the risk profile and conducting a revised risk assessment, i.e. repeating Step 3 was not identified Summary of Findings The complete results of the Engineering Analysis step can be found in Table 5-6 and Table 5-7. The analysis was completed according to the methods set out in the PIEVC Protocol. These methods do not explicitly consider the difference between existing or future vulnerability, but instead focus on whether the component is vulnerable to the net of the existing load, plus future climatic load. As a result, the assessment of vulnerability reflects only the future condition. However, in the case of the stormwater facilities, a review of the interactions assessed as vulnerable, or having a Vulnerability Ratio greater than one, indicated that these interactions would also be judged as vulnerable in the existing condition. This is not surprising, given the nature of the climate events and the lack of quantitative information with which to calculate the Total Capacity of virtually all of the infrastructure components considered. The Engineering Analysis generally resulted in a determination of the vulnerability of the infrastructure components to a single occurrence of the climate event, rather than the probability or frequency of the event. For example, personnel could be identified as vulnerable to a freezing rain event for both existing and future conditions, with no distinction made regarding whether personnel are more or less vulnerable in the future with an increased probability of freezing rain events, as there is no information available with which to determine whether a change in frequency would increase the vulnerability of the components.

97 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 84 The above notwithstanding, it was possible to make a determination of the difference between existing and future risk for the components and interactions identified as vulnerable by revisiting the results of the Risk Assessment completed in Step 3. In that assessment, the probability scores did change for some climate events, as shown in Table 3-5, from the existing to future conditions, and the associated risk scores changed as well. Based on a comparison of those existing and future risk scores for vulnerable components and interactions, the potential effect of climate change in modifying risk to those components could be determined. The following sections provide a summary of the results for the stormwater facilities. A total of 1699 medium risks were identified for all stormwater facilities combined. To reduce this number to a more manageable level, a condensed engineering analysis was performed by grouping facilities that had similar components. The condensed analysis considered 44 medium risk interactions. As mentioned in Section , the risk assessment results did not consider extreme heavy rainfall events a medium risk for water quantity control ponds. Given observations made during the recent July 8, 2013 rainfall event and the projected IDF curves in Figure 5.2 a decision was made using engineering judgement to consider this interaction as vulnerable. With the addition of this vulnerability, there were six interactions assessed to be vulnerable, i.e. they have a Vulnerability Ratio of greater than one. These vulnerabilities are provided in Table 5-4. Table 5-4 Vulnerable Components of the Stormwater Facilities (Vulnerability Ratio >1) Infrastructure Component Detention Basin Quality Ponds with bypass (Vegetated & Concrete Ponds) Quality Ponds without bypass (Vegetated & Underground Tanks) Quantity Ponds (Vegetated & Concrete Ponds) Climate Parameter Interaction Heavy Rainfall Heavy 5-Day Total Rainfall Heavy Rainfall Heavy 5-Day Total Rainfall Extreme Heavy Rainfall Comments The capacity of water quality stormwater facilities will be exceeded when rainfall exceeds the design capacity (25 mm). However, the facility will likely not lose functionality since it is equipped with a bypass. Functionality of the water quality component of stormwater facilities without a bypass may be impaired when rainfall exceeds the design capacity (25 mm) of the detention basin, due to reduced particle settling time and potential resuspension. The projected increase in intensity of rainfall events may result in the capacity of quantity ponds being exceeded. The effects of an exceeded capacity for some quantity ponds (e.g. SWM 4) are unclear and may have unfavorable consequences. Inlet/Outlet Structures All inlets, outlets, ditches, diversion chambers, weirs, etc. Extreme Heavy Rainfall The maximum capacity of these components will very likely be exceeded during an extreme heavy rainfall. In the future, these events are projected to occur more frequently.

98 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 85 For Spring Creek culvert, a total of 58 medium risks were identified. To reduce this number to a more manageable level, a condensed engineering analysis was performed by grouping similar components. The condensed analysis considered 15 medium risk interactions. There was only one interaction that was assessed to be vulnerable, i.e. a vulnerability ratio of greater than one. This vulnerability is provided in Table 5-5. Table 5-5 Vulnerable Components of Spring Creek Triple Cell Box Culvert (Vulnerability Ratio >1) Infrastructure Component Structural System The culvert Climate Parameter Interaction Extreme Heavy Rainfall Comments Projected increases in the intensity and frequency of extreme heavy rainfalls may result in the culvert s capacity being exceeded more frequently, and while Runway will likely not overtop during the future 100-year design storm, Derry Road upstream of the culvert may overtop Complete Engineering Analysis Tables The condensed engineering analysis tables for the stormwater facilities and Spring Creek culvert are provided in Table 5-6 and Table 5-7 below.

99 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 86 Table 5-6 Engineering Analysis for Stormwater Facilities Infrastructure Component Climate Parameter Calculation of Total Load (L T) Calculation of Total Capacity (C T) Vulnerability (VR) Administration/Operations Existing Load (L E) Climate Load Time frame L C Ot he r Lo ad L O Total Load L T = L E + Lc + L O Existing Capacit y C E Matu ring Capa city C M Additi onal Capaci ty C A Total Capacity CT = C E - C M + C A V R = L T/C T Capacity Deficit (CD) C D = L T - C T Comments/Data Sufficiency Personnel High Temperature >0 n/a > 0.75 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may experience some discomfort but will likely still be able to perform their usual duties. Basis of Determination/ Data Source Day(s) with a max. temp exceeding 35 C Projected increase Probab ility increas e from '4' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Low Temperature <0 n/a < 0.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may perform their duties slower than usual. In the future these Basis of Determination/ Day(s) with a min. Projected Engineering Engineering Engineering extreme cold events may occur less Data Source temp below -30 C decrease Judgement Judgement Judgement frequently and should not be an issue. Probab ility decrea se from '3' to '2' Engineer ing Judgem ent Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Days with rainfall > 50mm Projected increase Probab ility increas e from '4' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Freezing Rain ~ >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source 9 or more days with freezing rain in one year Projected increase Probab ility increas e from '4' to '6' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Ice Storm >0 n/a >0.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Severe Freezing Rain events Projected increase Probab ility increas e from '2' to '3' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Snow Storm / Blizzard ~ n/a ~0.5 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source 8 or more days with blowing snow in one year No projectio n available Workin g assum ption Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may have difficulty finding any valves/hatches covered in snow that have not been sufficiently marked. Basis of Determination/ Data Source 5 or more consecutive days with a snow depth of >30cm Projected decrease Probab ility decrea se from '6' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement

100 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 87 Hailstorm n/a 1.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Days with precipitation falling as ice particles (dia. > 5mm) No projectio n available Workin g assum ption Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Personnel Lightning n/a C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source lightning strikes on the airport property within one year No projectio n available Workin g assum ption Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Hurricane/Tropical Storm >0 n/a >0.05 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will not likely be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Cyclones of a tropical origin with sustained surface wind speeds >63km/hr Projected increase Probab ility increas e from '1' to '2' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Detention Basins Quantity Ponds (Vegetated & Concrete Ponds) Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The detention basin will likely not reach its maximum capacity (100yr). However, the basin will be partially full. Basis of Determination/ Data Source Heavy 5-Day Total Rainfall Basis of Determination/ Data Source Winter Rain/Rain-on Snow Days with rainfall >50mm Projected increase Probab ility increas e from '4' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement >0 Projected increase n/a >0.1 C E> L T n/a n/a C T> L T Engineering Judgement V R< 1 Engineering Judgement 0 Engineering Judgement The detention basin will likely not reach its maximum capacity (100yr) during this event. However, the basin will be partially full. A five day period receiving >100mm of rainfall Probab ility increas e from '2' to '3' Engineer ing Judgem ent n/a 0.33 C E> L T n/a n/a C T> L T V R< 1 0 The rain will melt snow creating additional runoff. The detention basin will likely not reach its maximum capacity (100yr). Depending on the distribution of winter rain, the basin may contain a considerable amount of water.

101 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 88 Basis of Determination/ Data Source Greater than 25mm of rain falling during January, February and March Projected no change No change in probabi lity Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Quantity Ponds (Vegetated & Concrete Ponds) Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation contributes to snowmelt runoff during the spring. As Basis of Determination/ 5 or more Projected Probab Engineer Engineering Engineering Engineering currently designed, the detention basin Data Source consecutive days decrease ility ing Judgement Judgement Judgement will likely not reach its maximum with a snow depth decrea Judgem capacity (100 yr). A future decrease in of >30cm se from ent snow accumulation would have a '6' to '5' positive effect on the detention basins. Quality Ponds with bypass (Vegetated & Underground tanks) Heavy Snowfall n/a 2 C E> L T n/a n/a C T> L T V R< 1 0 The heavy snowfall may have an impact on scheduled maintenance/ inspection Basis of Determination/ Days with snowfall Limited Workin Engineer Engineering Engineering Engineering of the basins. However, since this type Data Source >10cm Projectio g ing Judgement Judgement Judgement of work is unlikely to be performed n assum Judgem during winter, the basins will not be Informati ption ent significantly impacted by a heavy on snowfall. Drought/Dry Periods >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 A drought may have a slight impact on the vegetation aspect of the basin. Basis of Determination/ 10 consecutive Projected Probab Engineer Engineering Engineering Engineering However, vegetation will likely have Data Source days with <0.2mm increase ility ing Judgement Judgement Judgement sufficient regular exposure to rainfall of precipitation increas Judgem since the total yearly precipitation is not e from ent expected to change significantly. '5' to '6' Heavy Rainfall >0 n/a >0.75 C E< L T n/a n/a C T< L T V R> 1 >0 The basin s maximum capacity (25 mm) will likely be exceeded more often. However, the treatment of the first 25 mm will likely be unaffected since the facility is equipped with a bypass. Basis of Determination/ Data Source Days with rainfall >50mm Projected increase Probab ility increas e from '4' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Rain (Frequency) ~ >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The basin may be required to treat small rainfalls more frequently. This could Basis of Determination/ 23 or more days Projected Probab Engineer Engineering Engineering Engineering result in sediment deposits accumulating Data Source of >10mm of rain increase ility ing Judgement Judgement Judgement faster than anticipated. Current within one year increas Judgem maintenance practices will likely remain e from ent sufficient. '4' to '5' Heavy 5 Day Total Rainfall >0 n/a >0.1 C E< L T n/a n/a C T< L T V R> 1 >0 The basins maximum capacity (25 mm) may be exceeded by this event.

102 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 89 Basis of Determination/ Data Source Winter Rain/RainonSnow Basis of Determination/ Data Source A five day period receiving >100mm of rainfall Projected increase Probab ility increas e from '2' to '3' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement However, the treatment of the first 25 mm will likely be unaffected since the facility is equipped with a bypass n/a 0.33 C E> L T n/a n/a C T> L T V R< 1 0 The rain will melt snow creating Greater than 25mm of rain falling during January, February and March Projected no change No change in probabi lity Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement additional runoff. The detention basin will likely not reach its maximum capacity (25mm). Depending on the distribution of winter rain, the basin may be partially full. Quality Ponds with bypass (Vegetated & Underground tanks) Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation contributes to snowmelt runoff during the spring. The Basis of Determination/ 5 or more Projected Probab Engineer Engineering Engineering Engineering detention basins may approach or reach Data Source consecutive days decrease ility ing Judgement Judgement Judgement full capacity (25 mm). A future decrease with a snow depth decrea Judgem in snow accumulation would have a of >30cm se from ent positive effect on the detention basins. '6' to '5' Heavy Snowfall n/a 2 C E> L T n/a n/a C T> L T V R< 1 0 The heavy snowfall may have an impact on scheduled maintenance/ inspection Basis of Determination/ Days with snowfall Limited Workin Engineer Engineering Engineering Engineering of the basins. However, since this type Data Source >10cm Projectio g ing Judgement Judgement Judgement of work is not likely to be performed n assum Judgem during winter, the basins will not be Informati ption ent significantly impacted by a heavy on snowfall. Drought/Dry Periods >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 A drought may have a slight impact on the vegetation aspect of the basin. Basis of Determination/ 10 consecutive Projected Probab Engineer Engineering Engineering Engineering However, vegetation will likely have Data Source days with <0.2mm increase ility ing Judgement Judgement Judgement sufficient regular exposure to rainfall of precipitation increas Judgem since the total yearly precipitation is not e from ent expected to change significantly. '5' to '6' Quality Ponds without bypass (Vegetated) Heavy Rainfall >0 n/a >0.75 C E< L T n/a n/a C T< L T V R> 1 >0 The basin s maximum capacity (25 mm) will likely be exceeded more often. Reduced treatment functionality is likely Basis of Determination/ Data Source Days with rainfall >50mm Projected increase Probab ility increas e from '4' to '5' Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement as water flows through the facility. Where possible, a retrofitted bypass could mitigate this risk. Rain (Frequency) ~ >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The basin may be required to treat small rainfalls more frequently. This could Basis of Determination/ 23 or more days Projected Probab Engineer Engineering Engineering Engineering result in sediment deposits accumulating Data Source of >10mm of rain increase ility ing Judgement Judgement Judgement faster than anticipated. Current within one year increas Judgem maintenance practices will likely remain e from ent sufficient. Heavy 5 Day Total Rainfall Basis of Determination/ Data Source Winter Rain/Rain-on Snow '4' to '5' >0 n/a >0.1 C E< L T n/a n/a C T< L T V R> 1 >0 The basin s maximum capacity (25 mm) may be exceeded by this event. Projected Probab Engineer Engineering Engineering Engineering Reduced treatment functionality is likely increase ility ing Judgement Judgement Judgement as water flows through the facility. increas Judgem Where possible, a retrofitted bypass e from ent could mitigate this risk. A five day period receiving >100mm of rainfall '2' to '3' n/a 0.33 C E> L T n/a n/a C T> L T V R< 1 0 The rain will melt snow creating additional runoff. The detention basin

103 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 90 Basis of Determination/ Data Source Greater than 25mm of rain falling during January, February and March Projected no change No change in probabi lity Engineer ing Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement will likely not reach its maximum capacity (25mm). Depending on the distribution of winter rain, the basin may be partially full. Quality Ponds without bypass (Vegetated) Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation contributes to snowmelt runoff during the spring. The Basis of Determination/ 5 or more Projected Probab Engineer Engineering Engineering Engineering detention basins may approach or reach Data Source consecutive days decrease ility ing Judgement Judgement Judgement full capacity (25 mm). A future decrease with a snow depth decrea Judgem in snow accumulation would have a of >30cm se from ent positive effect on the detention basins. '6' to '5' Inlet/Outlet Structures All inlets, outlets, ditches, diversion chambers, weirs, etc Heavy Snowfall n/a 2 C E> L T n/a n/a C T> L T V R< 1 0 The heavy snowfall may have an impact on scheduled maintenance/ inspection Basis of Determination/ Days with snowfall Limited Workin Engineer Engineering Engineering Engineering of the basins. However, since this type Data Source >10cm Projectio g ing Judgement Judgement Judgement of work is not likely to be performed n assum Judgem during winter, the basins will not be Informati ption ent significantly impacted by a heavy on snowfall. Drought/Dry Periods >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 A drought may have a slight impact on the vegetation aspect of the basin. Basis of Determination/ 10 consecutive Projected Probab Engineer Engineering Engineering Engineering However, vegetation will likely have Data Source days with <0.2mm increase ility ing Judgement Judgement Judgement sufficient regular exposure to rainfall of precipitation increas Judgem since the total yearly precipitation is not e from ent expected to change significantly. '5' to '6' Extreme Heavy Rainfall >0 n/a >0.05 C E< L T n/a n/a C T< L T V R> 1 >0 The maximum capacity will very likely be exceeded during this event. In the future this is projected to occur more frequently. A separate study is currently underway to determine the consequences of this event. Basis of Determination/ Data Source Days with rainfall >125mm Projected increase Proba bility increa se from '1' to '2' Enginee ring Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The maximum capacity will likely not be reached. The projected increase in Basis of Determination/ Days with rainfall Projected Engineering Engineering Engineering frequency of this event will likely have no Data Source >50mm increase Judgement Judgement Judgement significant impact. Heavy 5 Day Total Rainfall Proba bility increa se from '4' to '5' Enginee ring Judgem ent >0 n/a >0.1 C E> L T n/a n/a C T> L T V R< 1 0 The maximum capacity will likely not be reached. The projected increase in

104 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 91 All inlets, outlets, ditches, diversion chambers, weirs, etc. Mechanical Systems Oil/water separator, all actuators and pumps, ventilation system, valves, etc. Basis of Determination/ Data Source A five day period receiving >100mm of rainfall Projected increase Proba bility increa se from '2' to '3' Enginee ring Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement frequency of this event will likely have no significant impact. Rain (Frequency) ~ >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The components will perform as designed. An increase in rain frequency Basis of Determination/ 23 or more days Projected Enginee Engineering Engineering Engineering may slightly accelerate deterioration of Data Source of >10mm of rain increase ring Judgement Judgement Judgement the infrastructure. However, current within one year Judgem inspection and maintenance practices ent will expose and replace damaged infrastructure as required. Proba bility increa se from '4' to '5' Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation contributes to snowmelt runoff during the spring. The Basis of Determination/ 5 or more Projected Proba Enginee Engineering Engineering Engineering components capacity will likely not be Data Source consecutive days decrease bility ring Judgement Judgement Judgement reached. A future decrease in snow with a snow depth decrea Judgem accumulation would have a positive of >30cm se ent effect on these components. from '6' to '5' Winter Rain/RainonSnow Basis of Determination/ Data Source n/a 0.33 C E> L T n/a n/a C T> L T V R< 1 0 The rain will melt snow creating Greater than 25mm of rain falling during January, February and March Projected no change No chang e in proba bility Enginee ring Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement additional runoff. The components will likely not reach their full capacity. Depending on the distribution of winter rain, the components may be partial full at times. Freezing Rain ~ >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 The projected increase in freezing rain events may interfere with regular Basis of Determination/ 9 or more days Projected Proba Enginee Engineering Engineering Engineering maintenance/inspection schedules. The Data Source with freezing rain increase bility ring Judgement Judgement Judgement maintenance/inspection will only be in one year increa Judgem delayed. se ent from '4' to '6' Heavy Snowfall n/a 2 C E> L T n/a n/a C T> L T V R< 1 0 Heavy snowfall may interfere with regular maintenance/inspection Basis of Determination/ Days with snowfall Engineering Engineering Engineering schedules. The maintenance/inspection Data Source >10cm Judgement Judgement Judgement will only be delayed. Limited Projectio n Informati on Worki ng assum ption Enginee ring Judgem ent Low Temperature <0 n/a < 0.1 C E> L T n/a n/a C T> L T V R< 1 0 Low temperatures may reduce usability of some mechanical parts (e.g. manual exterior valves). Minor delays in maintenance/ inspection of exterior parts may also be expected. This event is projected to become less frequent and Basis of Determination/ Data Source Day(s) with a min. temp below -30 C Projected decrease Proba bility decrea se from '3' to '2' Enginee ring Judgem ent Engineering Judgement Engineering Judgement Engineering Judgement will likely have an insignificant impact on the overall functionality of the mechanic systems.

105 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 92 Low Temperature <0 n/a < 0.1 C E> L T n/a n/a C T> L T V R< 1 0 Low temperatures may reduce usability of some mechanical parts (e.g. manual Basis of Determination/ Day(s) with a min. Projected Proba Enginee Engineering Engineering Engineering exterior valves). Minor delays in Data Source temp below -30 C decrease bility ring Judgement Judgement Judgement maintenance/ inspection of exterior parts decrea Judgem may also be expected. This event is se ent projected to become less frequent and from will likely have an insignificant impact on '3' to the overall functionality of the mechanic '2' systems. Oil/water separator, all actuators and pumps, ventilation system, valves, etc. Freezing Rain ~ >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 The projected increase in freezing rain events may interfere with regular Basis of Determination/ 9 or more days Projected Proba Enginee Engineering Engineering Engineering maintenance/inspection schedules. The Data Source with freezing rain increase bility ring Judgement Judgement Judgement maintenance/inspection will only be in one year increa Judgem delayed. se ent from '4' to '6' Heavy Snowfall n/a 2 C E> L T n/a n/a C T> L T V R< 1 0 Heavy snowfall may interfere with regular maintenance/inspection Basis of Determination/ Days with snowfall Engineering Engineering Engineering schedules. The maintenance/inspection Data Source >10cm Judgement Judgement Judgement will only be delayed. Limited Projectio n Informati on Worki ng assum ption Enginee ring Judgem ent Blowing Snow / Blizzard n/a 7.8 C E> L T n/a n/a C T> L T V R< 1 0 A blizzard may interfere with regular maintenance/ inspection schedules. The Basis of Determination/ 8 or more days Engineering Engineering Engineering maintenance/ inspection will only be Data Source with blowing snow Judgement Judgement Judgement delayed. in one year Limited Projectio n Informati on Worki ng assum ption Enginee ring Judgem ent Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation may interfere with maintenance/ inspection in areas which Basis of Determination/ 5 or more Projected Proba Enginee Engineering Engineering Engineering are not cleared of snow (e.g. WM4A Data Source consecutive days decrease bility ring Judgement Judgement Judgement valve). The maintenance/ inspection with a snow depth decrea Judgem would only be delayed, and could still be of >30cm se ent performed if necessary. from '6' to '5'

106 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 93 Table 5-7 Engineering Analysis for Spring Creek Culvert Infrastructure Component Administration/Operations Climate Parameter Calculation of Total Load (L T) Calculation of Total Capacity (C T) Vulnerability (VR) Existing Load (L E) Climate Load Other Timeframe L C Load L O Total Load L T = L E + Lc + L O Existing Capacity C E Maturing Capacity C M Additional Capacity C A Total Capacity CT = C E - C M + C A V R = L T/C T Capacity Deficit (CD) C D = L T - C T Comments/Data Sufficiency Personnel High Temperature >0 n/a > 0.75 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may experience some discomfort but will likely still be able to perform their usual duties. Basis of Determination/ Data Source Day(s) with a max. temp exceeding 35 C Projected increase Probability increase from '4' to '5' Engineering Judgement Low Temperature <0 n/a < 0.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may perform their duties slower than usual. In the future these extreme Basis of Determination/ Day(s) with a min. Projected Probability Engineering Engineering Engineering Engineering cold events may occur less frequently and Data Source temp below -30 C decrease decrease from Judgement Judgement Judgement Judgement should not be an issue. '3' to '2' Engineering Judgement Engineering Judgement Engineering Judgement Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Days with rainfall >50mm Projected increase Probability increase from '4' to '5' Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Freezing Rain ~ >0 n/a >1.25 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source 9 or more days with freezing rain in one year Projected increase Probability increase from '4' to '6' Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Ice Storm >0 n/a >0.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Severe Freezing Rain events Projected increase Probability increase from '2' to '3' Engineering Judgement Snow Storm/Blizzard ~ n/a ~0.5 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source 8 or more days with blowing snow in one year No projection available Working assumption Engineering Judgement Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Personnel may have difficulty finding any valves/hatches covered in snow that have not been sufficiently marked. Basis of Determination/ Data Source 5 or more consecutive days with a snow depth of >30cm Projected decrease Probability decrease from '6' to '5' Engineering Judgement Personnel Hailstorm n/a 1.1 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Days with precipitation falling as ice particles (dia. >5mm) No projection available Working assumption Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Lightning n/a C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source lightning strikes on the airport property within one year No projection available Working assumption Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement

107 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page 94 Structural System Hurricane/Tropical Storm >0 n/a >0.05 C E> L T n/a n/a C T> L T V R< 1 0 Personnel will likely not be able to work under these conditions. Their regular duties will only be delayed. Basis of Determination/ Data Source Cyclones of a tropical origin with sustained surface wind speeds >63km/hr Projected increase Probability increase from '1' to '2' Engineering Judgement All rip rap Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The projected increase in storm intensity may result in rip-rap being disturbed more Basis of Determination/ Days with rainfall Projected Probability Engineering Engineering Engineering Engineering often than usual. Regular maintenance Data Source >50mm increase increase from Judgement Judgement Judgement Judgement would only have to be slightly adjusted to '4' to '5' accommodate for this. The culvert Heavy Rainfall >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The culvert will likely not reach full capacity during a heavy rainfall. The projected Basis of Determination/ Days with rainfall Projected Probability Engineering Engineering Engineering Engineering increase in frequency of this event will Data Source >50mm increase increase from Judgement Judgement Judgement Judgement likely result in the culvert being partially '4' to '5' filled more frequently. Rain (Frequency) ~ >0 n/a >0.75 C E> L T n/a n/a C T> L T V R< 1 0 The culvert will perform as designed. An increase in rain frequency would likely have an insignificant impact on the culvert. Basis of Determination/ Data Source 23 or more days of >10mm of rain within one year Projected increase Probability increase from '4' to '5' Engineering Judgement Heavy 5 Day Total Rainfall >0 n/a >0.1 C E> L T n/a n/a C T> L T V R< 1 0 The maximum capacity will likely not be reached. The projected increase in Basis of Determination/ A five day period Projected Probability Engineering Engineering Engineering Engineering frequency of this event will likely result in Data Source receiving >100mm increase increase from Judgement Judgement Judgement Judgement the culvert being partially filled more of rainfall '2' to '3' frequently. Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement Snow Accumulation <0 n/a <1.25 C E> L T n/a n/a C T> L T V R< 1 0 Snow accumulation contributes to Basis of Determination/ Data Source 5 or more consecutive days with a snow depth of >30cm Projected decrease Probability decrease from '6' to '5' Engineering Judgement Engineering Judgement Engineering Judgement Engineering Judgement snowmelt runoff during the spring. The culvert's capacity will likely not be reached. A future decrease in snow accumulation would have a positive effect on this component.

108 Toronto Pearson Infrastructure Climate Vulnerability Assessment Page Recommendations 6.1. Overview The objective of Step 5 is to present limitations and recommendations on the observations and findings of the infrastructure vulnerability assessment in Steps 1 to 4. Figure 6.1 Recommendations Process Flowchart Relevant limitations include those associated with the following: Major assumptions; Available infrastructure information and sources; Available climate change information and sources; Available other change information and sources; Uncertainty and related concepts; and, Other relevant limitations.