COLE ENGINEERING GROUP LTD.

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1 CITY OF MARKHAM PROJECT FILE Stormwater Management Facilities Retrofit Municipal Class EA ES COLE ENGINEERING GROUP LTD SEPTEMBER 2015 [ Month Year ] HEAD OFFICE 70 Valleywood Drive Markham, ON CANADA L3R 4T5 T F wwwcoleengineeringca GTA WEST OFFICE 150 Courtneypark Drive West, Unit C100 Mississauga, ON CANADA L5W 1Y6 T F

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3 Statement of Conditions This Report/Study (the Work ) has been prepared at the request of, and for the exclusive use of, the Owner/Client, and its affiliates (the Intended User ) No one other than the Intended User has the right to use and rely on the Work without first obtaining the written authorization of Cole Engineering Group Ltd and its Owner Cole Engineering expressly excludes liability to any party except the intended User for any use of, and / or reliance upon, the work Neither possession of the Work, nor a copy of it, carries the right of publication All copyright in the Work is reserved to Cole Engineering The Work shall not be disclosed, produced or reproduced, quoted from, or referred to, in whole or in part, or published in any manner, without the express written consent of Cole Engineering and th e Owner ES (September 2015)

4 Table of Contents 10 Introduction 1 11 Study Background 1 12 Previous Studies and Background Data 1 13 Data Gaps 1 14 Problem / Opportunity Statement Problem Opportunity 3 15 Objectives of the Project 3 16 Purpose of the 4 20 Planning Context of the EA Planning Process 4 21 Municipal Class EA Four (4) Project Schedules Schedule B Classification Schedule B EA Process 7 22 Public Consultation 8 30 Inventory of Existing Conditions 8 31 Desktop Analysis Vegetation Fauna Designated Spaces and Species Land Use Cultural Environment Existing Stormwater Management Pond Conditions Existing Storm Sewer Infrastructure 9 32 Field Investigations Vegetation Surveys Site Visit of Potential New Stormwater Management Facility Locations Component Survey of Existing Stormwater Management Facilities Locations Screening of Stormwater Management Facilities and Uncontrolled Outlets Screening Criteria and Protocol to Identify Deficient Existing Stormwater Management Facilities Stormwater Management Facility Evaluation Screening Criteria and Protocol to Identify Potential New Stormwater Management Facility Opportunities Uncontrolled Outlet Evaluation 15 ES (September 2015) Page i

5 50 Prioritization of Stormwater Management Retrofit Opportunities Description of Prioritization Criteria Prioritization Results Development of Alternatives and Evaluation Criteria General Description of Alternatives Do Nothing Water Quality Control Erosion Control Quantity Control Temperature Control Control of Multiple Stormwater Management Objectives Summary of Alternatives Development of Evaluation Criteria Preferred Alternatives Pond Pond Pond Pond Pond Pond Pond Pond Pond Pond Pond Uncontrolled Outlet # Uncontrolled Outlet # Uncontrolled Outlet #63w Uncontrolled Outlet # Uncontrolled Outlet # Uncontrolled Outlet # Uncontrolled Outlet # Uncontrolled Outlet # Uncontrolled Outlet # ES (September 2015) Page ii

6 721 Uncontrolled Outlet # Conceptual Design of SWM Improvements General Objectives Methodology Quantity Control Quality Control Erosion Control Temperature Control Individual Conceptual Design Summaries Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Pond Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet #63w Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Conceptual Design Summary Uncontrolled Outlet # Public and Agency Consultation Public Consultation Activities through the EA Process Notice of Commencement Notice of Public Information Centre # Public Information Centre # Notice of Public Information Centre # Public Information Centre # Notice of Completion First Nations Consultation Consultation with the TRCA and MOE Consultation with the Ministry of Natural Resources 95 ES (September 2015) Page iii

7 100 Implementation of the Project Confirm EA Schedule Notice of Completion Steps to Implementation Funding Mechanisms Additional Studies Detailed Design Permits and Approvals Property Acquisitions and/or Agreements Summary of Potential Effects and Mitigation Measures Prioritization of the Implementation of Retrofits and New SWM Facility Construction Description of Prioritization Criteria Prioritization Results and Final Ranking References 107 LIST OF FIGURES Figure 2-1 Municipal Class EA Process 5 Figure 4-1 Screening Criteria for Existing SWM Facilities 12 Figure 4-2 Screening Criteria for Uncontrolled Outlets 14 Figure 5-1 Retrofit Site Prioritization Criteria 16 LIST OF TABLES Table 51 Prioritization Results 19 Table 61 Stormwater Management Objectives Achieved by Alternatives 24 Table 62 Preliminary Evaluation Criteria 25 Table 71 Summary of Alternative Evaluation Results 27 Table 81 Pond 5 Existing Conditions Hydrological Parameters 39 Table 82 Pond 5 Summary of Stormwater Management Control Achieved 40 Table 83 Pond 5 Cost Estimate 41 Table 84 Pond 24 Existing Conditions Hydrological Parameters 42 Table 85 Pond 24 Summary of Stormwater Management Control Achieved 42 Table 86 Pond 24 Cost Estimate 43 Table 87 Pond 38 Existing Conditions Hydrological Parameters 45 Table 88 Pond 39 Summary of Stormwater Management Control Achieved 45 Table 89 Pond 38 Cost Estimate 46 Table 810 Pond 39 Existing Conditions Hydrological Parameters 48 Table 811 Pond 39 Summary of Stormwater Management Control Achieved 48 Table 812 Pond 39 Cost Estimate 50 Table 813 Pond 45 Existing Conditions Hydrological Parameters 52 Table 814 Pond 45 Summary of Stormwater Management Control Achieved 53 Table 815 Pond 45 Cost Estimate 55 Table 816 Pond 47 Existing Conditions Hydrological Parameters 56 Table 817 Pond 47 Summary of Stormwater Management Control Achieved 57 ES (September 2015) Page iv

8 City of Markham Table 818 Pond 47 Cost Estimate 59 Table 819 Pond 51 Existing Conditions Hydrological Parameters 60 Table 820 Pond 51 Summary of Stormwater Management Control Achieved 61 Table 821 Pond 51 Cost Estimate 62 Table 822 Pond 55 Existing Conditions Hydrological Parameters 64 Table 823 Pond 55 Summary of Stormwater Management Control Achieved 64 Table 824 Pond 55 Cost Estimate 65 Table 825 Pond 62 Existing Conditions Hydrological Parameters 66 Table 826 Pond 62 Summary of Stormwater Management Control Achieved 66 Table 827 Pond 62 Cost Estimate 67 Table 828 Pond 73 Cost Estimate 68 Table 829 Pond 77 Cost Estimate 70 Table 830 UCO 8 Existing Conditions Hydrological Parameters 71 Table 831 UCO 8 Summary of Stormwater Management Control Achieved 72 Table 832 UCO 8 Cost Estimate 72 Table 833 UCO 55 Existing Conditions Hydrological Parameters 73 Table 834 UCO 55 Summary of Stormwater Management Control Achieved 73 Table 835 UCO 55 Cost Estimate 74 Table 836 UCO 63w Existing Conditions Hydrological Parameters 75 Table 837 UCO 63w Summary of Stormwater Management Control Achieved 75 Table 838 UCO 63w Cost Estimate 76 Table 839 UCO 66 Existing Conditions Hydrological Parameters 77 Table 840 UCO 66 Summary of Stormwater Management Control Achieved 77 Table 841 UCO 66 Cost Estimate 78 Table 842 UCO 94 Existing Conditions Hydrological Parameters 79 Table 843 UCO 94 Summary of Stormwater Management Control Achieved 80 Table 844 UCO 94 Cost Estimate 81 Table 845 UCO 103 Existing Conditions Hydrological Parameters 82 Table 846 UCO 103 Summary of Stormwater Management Control Achieved 82 Table 847 UCO 103 Cost Estimate 83 Table 848 UCO 106 Existing Conditions Hydrological Parameters 84 Table 849 UCO 106 Summary of Stormwater Management Control Achieved 84 Table 850 UCO 106 Cost Estimate 85 Table 851 UCO 112 Existing Conditions Hydrological Parameters 86 Table 852 UCO 112 Summary of Stormwater Management Control Achieved 86 Table 853 UCO 112 Cost Estimate 86 Table 854 UCO 162 Existing Conditions Hydrological Parameters 87 Table 855 UCO 162 Summary of Stormwater Management Control Achieved 88 Table 856 UCO 162 Cost Estimate 89 Table 857 UCO 176 Existing Conditions Hydrological Parameters 90 Table 858 UCO 176 Summary of Stormwater Management Control Achieved 91 Table 859 UCO 176 Cost Estimate 91 Table 101 Municipal Class Environmental Assessment Schedule 96 Table 102 Summary of Potential Required Permits 101 Table 103 Implementation Prioritization Criteria 104 Table 104 Implementation Ranking 106 ES (September 2015) Page v

9 APPENDICES Appendix A Background Data Appendix B Vegetation Investigations and Classification Appendix C Uncontrolled Outlet Field Investigations Appendix D Screening Process Details and Rational Appendix E Prioritization of Retrofit and New Construction Opportunities Appendix F Alternative Design Evaluation Appendix G Conceptual Design Calculations and Figures Appendix H Public Consultation Responses Appendix I Notice of Commencement Appendix J Notice of Public Information Centre Appendix K Public Information Centre Materials Appendix L Notice of Completion Appendix M Consultation with Review Agencies Appendix N Implementation Ranking Appendix O Statement of Limiting Conditions and Assumptions LIST OF MAPS Map 4-1 Evaluated Sites Map 7-1 Priority Sites Map Pocket Map Pocket ES (September 2015) Page vi

10 10 Introduction In 2012, the City of Markham (the City ) initiated a Schedule B Municipal Class Environmental Assessment (Class EA) to identify a prioritized list of Stormwater Management (SWM) facilities within the City for retrofit or construction to meet current SWM standards The Class EA has identified a list of 21 facilities which are the highest priority for the City A preliminary / functional design of these facilities has also been completed 11 Study Background SWM criteria in Ontario have changed vastly since the City s earliest SWM facilities were built pre-1980 The City contains approximately 111 SWM facilities, 73 of which are owned by the City The majority of these SWM facilities that have been assumed by the City were built prior to the implementation of the current SWM criteria, especially the criteria requiring temperature mitigation in coldwater watercourses As a result there are many opportunities within the City to retrofit existing SWM facilities Additionally, there are many uncontrolled outlets within the City, which provide an additional opportunity to construct new SWM facilities or controls 12 Previous Studies and Background Data A previous study, Town of Markham Stormwater Retrofit Study, was completed by the Toronto and Region Conservation Authority (TRCA) in 1999 that resulted in a retrofit pond priority list that included 10 SWM facilities and eight (8) potential new SWM facilities within the Town of Markham Completed SWM reports for the existing SWM facilities as well as additional background data provided by the City were reviewed The majority of this information was included in the City s SWMSoft database but additional SWM facility information was also provided by the City and TRCA A summary of all of the data reviewed during this study is included in Appendix A Correspondence was also received from the City regarding the status of some existing SWM facilities and uncontrolled outlets in the City These communications can be found in Appendix A 13 Data Gaps The data collected for this project is from a combination of sources including the City s SWMSoft database, the City s archives and the City s Geomatics Department, the TRCA, field investigations and site surveys Many data gaps were encountered throughout each phase of the project Examples of data gaps are: Accurate drainage area information; A complete list of all SWM ponds within the City; Studies and design reports for existing ponds (required to understand what controls the pond currently provides and the catchment characteristics used to design the pond); and, Pond inlet and outlet elevations, sizes and other characteristics ES (September 2015) Page 1

11 A large source of data gaps was the City s SWMSoft database itself Many of the ponds documented within SWMSoft had missing information, incomplete information recorded or there was no record of the pond within the database at all The following was completed to fill the data gaps: Making further data requests to the City and TRCA for information regarding specific ponds; Desktop analysis of DEM mapping and sewer mapping provided by the City to confirm drainage catchments; Desktop analysis of bathymetric pond surveys and DEM mapping to determine the storage and permanent pool provided by ponds; Completing site investigations of ponds lacking information This includes survey of key pond features and entry into maintenance holes to determine outlet controls; and, Modeling to determine whether existing ponds provide the controls required Cole Engineering has done its best to gather all the information required and available to complete an accurate assessment of the existing SWM infrastructure within the City and to provide sound and accurate retrofit recommendations However, more detailed studies may need to be completed in order to fill and/or verify missing information as these sites go to detailed design 14 Problem / Opportunity Statement 141 Problem SWM standards in Ontario have evolved significantly since the practice was made widespread prior to the 1980 s A number of the City s SWM facilities were built prior to 1990 and may not achieve the level of water quality and quantity control, or habitat protection that is up to present standards A previous Stormwater Retrofit Study conducted in 1999 by the TRCA had identified 10 priority SWM Pond retrofits, five (5) of which have been completed However, during the execution of these retrofits and expansion of the City s urban boundary, it was discovered that additional retrofit opportunities may exist Moreover, the City contains a significant population of Redside Dace, a fish species recently designated as an endangered species by the Ministry of Natural Resources (MNR) Redside Dace habitat may be negatively impacted by lower quality runoff released by SWM facilities or lack of SWM facilities that meet current criteria ES (September 2015) Page 2

12 142 Opportunity The City strives to protect, enhance, and restore Markham s natural features and green spaces as part of a vital and healthy ecosystem, and to make Markham a recognized leader in environmental standards In response to the additional SWM retrofit opportunities and to participate in the protection and recovery of Redside Dace, the City has commissioned this SWM Facilities Retrofit Study Class EA to update and prioritize opportunities to improve the management of stormwater within the City Improvements may be achieved through the retrofit of existing SWM facilities and through the construction of new SWM facilities in areas that are currently lacking appropriate controls These opportunities seek to improve watercourse water quality and water temperature control, protect / enhance aquatic and terrestrial habitat and give consideration to environmentally significant areas A prioritized list of SWM facility retrofit and new construction opportunities will be developed with consideration of the potential natural, social, economic, and cultural effects of the alternatives 15 Objectives of the Project In the summer of 2012, the City retained Cole Engineering to create a prioritized list of SWM facilities within the City of Markham with retrofit potential To be included in this list are uncontrolled stormwater outlets where SWM facilities or controls could be provided Alternatives were investigated at each of the prioritized sites to determine the optimal design of the SWM facility retrofits and new SWM facilities The objectives of this study are to: 1 Upgrade or construct new SWM facilities to meet current SWM criteria; 2 Improve the condition of the receiving watercourses within the City; 3 Improve Redside Dace habitat and populations; 4 Identify a prioritized list of SWM facilities within the City that need to be retrofit to meet current standards as well as opportunities for constructing new SWM facilities at current uncontrolled stormwater outlets; 5 Complete conceptual designs for the prioritized list of SWM facility retrofits and new facilities; and, 6 Provide recommendations for a long-term implementation program by the City ES (September 2015) Page 3

13 16 Purpose of the This documents the planning and design process and conclusions of the SWM Facilities Retrofit Class EA Study In accordance with the Municipal Class EA planning and design process, the problems and opportunities associated with this study were investigated and documented A prioritized list of SWM facilities was developed along with a long-term implementation program Next, a number of alternative solutions were identified and evaluated for each prioritized SWM facility location, leading to the selection of a preferred solution at each location This information was presented to stakeholders at two (2) Public Information Centres (PIC) The documents the Class EA process followed as well as the technical evaluation undertaken during the screening, prioritization and design processes 20 Planning Context of the EA Planning Process 21 Municipal Class EA The Municipal Class EA (2007) planning and design process was followed for this project to allow the City to meet the requirements of the Ontario Environmental Assessment (EA) Act (OEAA) for municipal infrastructure without having to either undertake an Individual EA or request a specific exemption for the project The Class EA is a planning process approved under the OEAA for a class or group of undertakings including municipal infrastructure Municipal projects included in the Class EA may be implemented without further approval under the OEAA, provided that the approved Class EA planning and design process is followed (Figure 2-1) ES (September 2015) Page 4

14 City of Markham Figure 2-1 Municipal Class EA Process ES (September 2015) Page 5

15 211 Four (4) Project Schedules Since projects undertaken by municipalities vary in their environmental effects, the Class EA classifies these projects into four (4) schedules according to their environmental significance: 1 Schedule A Projects are limited in scale, have minimal adverse effects and include the majority of municipal maintenance and operational activities These projects are approved and may proceed directly to Phase 5 for implementation without following the other phases 2 Schedule A+ Projects are limited in scale and have minimal adverse effects These projects are approved and may proceed directly to Phase 5 for implementation without following the other phases However, the public is to be advised prior to project implementation though there is no ability for the public to request a Part II Order 3 Schedule B Projects have the potential for some adverse environmental effects The municipality is required to undertake a screening process (Phases 1 and 2) involving mandatory contact with directly affected public and relevant review agencies to ensure that they are aware of the project and that their concerns are addressed Schedule B projects require that a report be prepared and submitted for review by the public and review agencies If there are no outstanding concerns, then the municipality may proceed to Phase 5 for implementation 4 Schedule C Projects have the potential for significant environmental effects and must proceed under the full planning and documentation procedures specified in the Class EA Document (Phases 1 to 4) Schedule C projects require that an Environmental Study Report be prepared and submitted for review by the public and review agencies If there are no outstanding concerns, then the municipality may proceed to Phase 5 for implementation 212 Schedule B Classification Appendix 1 of the Municipal Class EA document identifies Water and Wastewater Projects subject to Schedule B of the Class EA, including projects that seek to: 2 Establish new stormwater retention / detention ponds and appurtenances or infiltration systems including outfall to receiving water body where additional property is required 3 Establish stormwater retention / detention ponds / tanks or sanitary or combined sewage detention tanks by addition or replacement, at substantially the same location where additional property is required Since The SWM Facilities Retrofit Class EA seeks to establish new or enlarge stormwater retention ponds where additional property may be required, it is classified as a Schedule B project ES (September 2015) Page 6

16 213 Schedule B EA Process The following activities were carried out for this Study: Phase 1: Identify the Problem / Opportunity This phase involves identifying the problem / opportunity to be addressed through the study and describing it in sufficient detail to lead to a clear problem / opportunity statement Upon completion of the problem / opportunity statement, a Notice of Commencement is published to notify the public that the Class EA study has been initiated This phase is described in Section 14 Phase 2: Identify and Evaluate Alternative Solutions to the Problem / Opportunity This phase involves six (6) steps: 1 Identify reasonable alternative solutions to the problem / opportunity (Section 60); 2 Prepare a general inventory of the existing natural, social and economic environments in which the project is to occur (Section 30); 3 Identify the net positive and negative effects of each alternative solution, including mitigating measures (Section 70); 4 Evaluate the alternative solutions (Section 70); 5 Consult with review agencies and the public to solicit comment and input (Section 90); and, 6 Select or confirm the preferred solution (Section 70) Once the 21 top priority sites were identified, Phase 2 of the Schedule B EA process was applied to each site individually Confirm EA Schedule Once the preferred solution was confirmed for each of the top 21 retrofit sites, the choice of a Schedule B EA process was reviewed The results of this review are provided in Section 101 Either a Schedule A, A + or B applies to each of the 21 proposed retrofits or new SWM facilities; therefore, the Schedule B process followed in this study has satisfied the EA requirements for each of the individual retrofit / new construction projects and these projects may proceed to the implementation phase Public Record Review Period Once completed, the is placed on public record for a period of at least 30 calendar days to allow review agencies and the public an opportunity to review it During this review period, concerned individuals have the right to raise and discuss issues prior to requesting a Part II Order before the project may proceed to implementation A Part II Order requires an Individual EA to be carried out and submitted to the Minister of the Environment for review and approval The decision on whether the project should be subject to a Part II Order rests with the Minister of the Environment Assuming there are no outstanding Part II Order requests, the Municipality is able to proceed to the final phase of the process once the review period has expired ES (September 2015) Page 7

17 22 Public Consultation In order to fulfill the requirements for a Municipal Class EA, two (2) PICs were held, one (1) on March 5, 2013 and the other on December 4, 2013, at the Markham Civic Center Section 90 describes the public consultation process in detail 30 Inventory of Existing Conditions Many aspects of the existing environmental conditions within the City were inventoried or reviewed and are summarized in the sections below 31 Desktop Analysis A desktop analysis was completed using ArcGIS to view and analyze mapping data received from the City and TRCA as well as the City s SWMSoft database 311 Vegetation Ecological Land Classification and flora mapping data was obtained from the TRCA and aerial imagery was obtained from the City These data sources were used throughout the project process to assess existing vegetation conditions and develop alternatives that minimize impacts to existing vegetation Field investigations were conducted at particular sites to gain more in depth understanding of existing vegetation and habitat conditions Field investigations are discussed in Section Fauna Fauna mapping data was obtained from the TRCA and reviewed to screen for any species near the project s subject sites that are species at risk or species in consideration for at risk designation Species observed during field investigations were also noted 313 Designated Spaces and Species Environmentally Significant Area mapping data was obtained from the TRCA MNR provided an indication of whether or not the project s subject sites had the potential of impacting Redside Dace habitat This information was used in the prioritization of potential retrofit opportunities and is further discussed in Section Land Use Parcel and easement mapping data and aerial imagery was obtained from the City This data was used to determine land ownership and current land use, for example City-owned public recreational parks This information was used in the screening and prioritization of potential retrofit opportunities and was considered during the conceptual design of the retrofits This is further discussed in Sections 50, 60, 84 ES (September 2015) Page 8

18 315 Cultural Environment The Ministry of Tourism and Culture check sheets for EAs were used to screen for cultural heritage and archaeological potential This information was used during the prioritization of potential retrofit opportunities and is further discussed in Section 50 Mapping data related to heritage parcels and districts, Ontario Heritage Act designated properties, heritage buildings and registered site locations were obtained from the City Internet data searches and aerial imagery was also used to complete the review 316 Existing Stormwater Management Pond Conditions The City s SWMSoft database of SWM ponds was used to obtain information about pond location, function, style (wetland vs wet pond and online vs offline) and adjacent land use The database included photos of the pond and adjacent land and, where available, included design reports and drawings related to the pond 317 Existing Storm Sewer Infrastructure Storm sewer mapping data was obtained from the City This information was used to identify existing uncontrolled storm outlets and to access the feasibility of various concept retrofit designs 32 Field Investigations 321 Vegetation Surveys Cole Engineering undertook a vegetation survey during the weeks of October 15 to 19, 2012 and October 22 to 26, 2012 The purpose of this study was to classify the surrounding vegetation communities of select existing SWM facilities and uncontrolled area outlets where the potential for retrofit exists This vegetation survey allowed for an assessment of the site conditions which was used during the screening stage of this project, as well as an assessment of the habitat quality and opportunities for habitat enhancement which was used during the prioritization and conceptual retrofit design stages of this project The vegetation survey was completed in two (2) phases Phase 1 was an initial screening of all SWM facilities with retrofit potential and uncontrolled outlets using Aerial Photo Interpretation Any area that was determined to have natural habitat associated with it was moved into Phase 2 of the survey Examples of this natural habitat that are visible on Aerial Phase 1 photos are deciduous forests, coniferous forests, wetlands, and natural meadows Areas excluded from Phase 2 were any areas that appeared to be in manicured parks or heavily built up areas The areas that were excluded through Phase 1 can be found in Appendix B ES (September 2015) Page 9

19 Phase 2 of the survey was the field component Each site was visited and classified using the Ecological Classification of Southern Ontario (ELC) guidelines (Lee, 1998) As no in-depth soil analysis was taken at each site, the areas are classified to the ELC Community Series Community series are distinguished based on the type of vegetation cover or the plant form that characterizes the community The dominant plant species are included as well as a general soil series as found in the Soils of York Region Report published by the Ontario Ministry of Food and Rural Affairs Please refer to Appendix B for a report summarizing the findings of the Phase 2 vegetation survey as well as photos taken on site 322 Site Visit of Potential New Stormwater Management Facility Locations Cole Engineering undertook a field inspection of all uncontrolled outlets that had proceeded to the field work stage of the screening process, as described in Section 43, to document and assess site conditions that could not be determined through a desktop review Site inspections were completed on November 14, 15, 21 and 22, 2013 During the inspections the outlet structure and size were documented as well as the existing land use and site conditions that may affect the feasibility of constructing a new SWM facility at the outlet A field inspection form was used that had been developed with the City to ensure that all necessary information was consistently collected The completed field inspection forms are included in Appendix C Results of the field inspections were used to further screen the uncontrolled outlets, as described in Section 43, and during the design of the retrofit concepts, as described in Section 80 During these field investigations, it was observed that a number of the storm outfalls were in a deteriorated condition Uncontrolled outlet #8 was in a significantly deteriorated condition where a majority of the gabion baskets lining the outfall channel have failed and the stones have washed away The armouring around uncontrolled outlet #55 is also in a deteriorated condition and erosion has occurred along the outlet dispersion channel Uncontrolled outlet #66 discharges directly into the east branch of the Don River The bank of this watercourse has eroded away from the outlet structure, exposing the storm sewer pipe connection to the outlet structure It is recommended that the City expand their annual component condition assessment and inventory of SWM ponds to include stormwater outfalls 323 Component Survey of Existing Stormwater Management Facilities Locations Component surveys of the existing SWM ponds were undertaken by Cole Engineering where adequate information regarding the existing pond infrastructure was not available and was needed to complete the conceptual retrofit designs The component surveys included identification of all inlets / outlets, and measurement and survey of the size and elevation of all inlets / outlets Some topographic survey was also completed as needed to confirm the pond berm elevation and shape and other related features such as outlet swales The results were used during the development of the conceptual retrofit designs The retrofit designs are discussed in Sections 70 and 80 ES (September 2015) Page 10

20 40 Screening of Stormwater Management Facilities and Uncontrolled Outlets The existing SWM facilities and uncontrolled outlets were screened to determine which facilities may require a retrofit and where a retrofit is feasible Refer to Map 4-1 for the location of all SWM and uncontrolled outlets that were evaluated and underwent the screening process Only the sites that are feasible for retrofit are carried forward to the prioritization stage where the top 21 sites of highest priority were selected 41 Screening Criteria and Protocol to Identify Deficient Existing Stormwater Management Facilities Screening criteria was developed to determine which of the existing SWM facilities were deficient and required retrofit The screening criteria are shown below in Figure 4-1 ES (September 2015) Page 11

21 Is the pond a municipally owned / assumed pond? No Yes Has the pond No been previously retrofit to meet current SWM standard? Yes No Provides adequate sediment removal? Provides adequate erosion control? Quantity control meets site specific criteria? Temperature control not an issue (includes Redside Dace considerations)? No Yes Yes to all Are temperature control measures present? Remove from Consideration No No No No Site access feasible? No Yes Proceed to Field Work (as required) Open Space? No Public / Utility Land (parks, hydro, etc)? No Private Property with Open Space Available? No Yes Yes Yes Natural hazards impact proposed pond design? Yes Remove from Consideration No Proceed to Prioritization Scoring Figure 4-1 Screening Criteria for Existing SWM Facilities ES (September 2015) Page 12

22 42 Stormwater Management Facility Evaluation The 108 stormwater facilities that were included in SWMSoft, as well as three (3) additional facilities at the City s request that were later identified through additional background report reviews were put through the screening process Field work was completed if required to gain pertinent information Refer to Section 321 for more information regarding this field work The list of 111 SWM facilities was screened down, using the criteria shown in Figure 4-1, to 23 sites which were carried forward to the prioritization stage, which is discussed in Section 50 Detailed tracking of the screening process and rational for screening out each site is provided in Appendix D 43 Screening Criteria and Protocol to Identify Potential New Stormwater Management Facility Opportunities Screening criteria was developed to determine which of the existing SWM facilities were deficient and required retrofitting The screening criteria are shown in Figure 4-2 ES (September 2015) Page 13

23 Figure 4-2 Screening Criteria for Uncontrolled Outlets ES (September 2015) Page 14

24 44 Uncontrolled Outlet Evaluation There is a significant amount of uncontrolled outlets within the City A total of 178 uncontrolled outlets were identified by analyzing the storm sewer network (GIS file provided by the City) An initial screening was done of these uncontrolled outlets prior to the screening described below This was to eliminate the uncontrolled outlets that should not be carried forward largely based on the drainage area to the outlet location as well as space and property constraints at the outlet location Several uncontrolled outlets were removed from consideration because there was a SWM pond downstream of these locations that could provide the required controls, or because a SWM facility is proposed for a currently uncontrolled outlet that, if constructed, would provide the required controls Once these locations were eliminated, the remaining 68 uncontrolled outlets were carried forward to the screening stage The list of 68 uncontrolled outlets was screened down, using the criteria shown in Figure 4-2, to 11 sites which were carried forward to the prioritization stage, which is discussed in Section 50 Field work was completed if required to gain pertinent information Refer to Section 322 for more information regarding this field work Detailed tracking of the screening process and rational for screening out each site is provided in Appendix D 50 Prioritization of Stormwater Management Retrofit Opportunities A total of 23 existing SWM facilities and 11 existing uncontrolled outlets were identified as needing retrofit and being feasible for retrofit through the above discussed screening process These 35 sites were then prioritized based on the criteria shown in Figure 5-1 to rank the sites from highest to lowest priority Each criterion was assigned a weighting as developed collaboratively by the Project Team, the City and stakeholders A score between 0 and 1 was then assigned to each criterion for a particular site, based on the specific site conditions and existing SWM controls A sliding scale was used when assigning a score for each criterion at a site This means a partial score was assigned where applicable, for example if an existing wet pond had a permanent pool that is half the size of what is required, a score of 05 was assigned to the Quality Control Upgrade Required criterion The final prioritization score of each site is a sum of the scores assigned to each criterion multiplied by the weighting of that criterion Final prioritization score are out of 100, with a score of 100 being the highest priority and a score of 0 being the lowest priority The 21 sites of highest priority were then analyzed to determine the optimal retrofit option for each site, as discussed in Sections 60 and 70 A brief description of each criterion is provided in Section 51 and a summary of the prioritization results is provided as Table 51 in Section 52 A detailed description of the reasoning behind the prioritization score assigned is provided in Appendix E ES (September 2015) Page 15

25 Figure 5-1 Retrofit Site Prioritization Criteria ES (September 2015) Page 16

26 51 Description of Prioritization Criteria Quantity Control Upgrade Required The need for a quantity control upgrade was evaluated based on whether adequate quantity control was currently provided (2-year through 100-year storm event controlled for post- to pre- peak flow), if quantity control is required (as per the TRCA August 2012 SWM Criteria) and if there was adequate space available for a quantity control retrofit If quantity control was not provided and was required but there was not adequate space available to build a suitable SWM facility, a score of zero (0) was assigned to not artificially raise the priority of the site since the required retrofit was not feasible Information regarding the existing controls at a site was based on reports, drawings and data in the Markham SWMsoft database and reports, drawings and other records received from the TRCA or directly from the City through site specific data requests Where data gaps limited the evaluation, field inspections and site surveys were undertaken Quality Control Upgrade Required The need for a quality control upgrade was evaluated based on whether adequate quality control (Enhanced Level as per MOE 2003 Guidelines) was currently provided If quality controls were provided but did not meet the Enhanced Level, a partial score was assigned Erosion Control Upgrade Required The need for an erosion control upgrade was evaluated based on whether 48 hour detention of 25 mm of the 4-hour Chicago Storm was currently provided A partial score was assigned if less than 48 hours (for example 24 hours) of detention was provided A score of one (1) was assigned if no extended detention was currently provided Temperature Mitigation Upgrade Required A site was classified as requiring temperature mitigation if the receiving watercourse had been identified as Redside Dace habitat or potential habitat by the MNR Redside Dace is a fish species that was recently designated as an endangered species by the MNR Redside Dace require cooler water temperatures and are also negatively impacted by lower water quality If a receiving watercourse was identified as Redside Dace habitat was assigned a score of one (1), possible Redside Dace habitat received a partial score and unlikely Redside Dace habitat received a score of zero (0) Order of Magnitude Cost The order of magnitude of the cost for the construction was estimated based on the below rationale: High cost if constructing a new pond where none exists; Medium cost if significant changes to an existing pond will be required; and, Low cost if minor modifications to an existing pond will be required (such as altering the outlet structure) If high costs were anticipated then a score of zero (0) was assigned to reduce the priority of the retrofit, allowing the City s limited capital works budget to be applied to multiple projects ES (September 2015) Page 17

27 Property Acquisition Required The need for the acquisition of land or easements was evaluated based on the anticipated space required for the potential retrofit Parcel data obtained from the City was used to identify existing City owned land If land or easements may need to be acquired, for the completion of the retrofit, a score of zero (0) was assigned This reduces the priority of the site because land and easement acquisition will be costly ELC / SAR / ESA If the site was located in an area with an Ecological Land Classification that was deemed valuable, an area providing / affecting habitat for a Species at Risk, or an Environmentally Significant Area, then undertaking any works in that area was considered less favourable because the works may negatively impact the valuable environment Therefore, a lower scoring was assigned ESA, ELC, flora and fauna mapping data was received from the TRCA and reviewed by the Project Team MNR identified whether the sites on the prioritization list discharge to Redside Dace habitat areas ELCs were considered valuable if the majority of the area was populated by native vegetation Archaeological / Cultural Heritage Significance Each site was evaluated to determine if a Heritage Impact Assessment will be required in the future and if the site is of archaeological potential or if a Stage 1 Archaeological Assessment will be required in the future These evaluations were carried out using the Ministry of Tourism and Culture check sheets for EAs Data required for the evaluations was obtained from the City and internet searches The completed check sheets are included in Appendix E If future assessments will be required in the future for both Heritage and Archaeological features, a score of zero (0) was assigned This reduces the priority of the site because additional assessments are costly and if heritage and/or archaeological features are identified in the future, this could impact the SWM retrofit works at that site ES (September 2015) Page 18

28 52 Prioritization Results Table 51 below provides a summary of the prioritization results Refer to Map 4-1 (following the report) for the location of these prioritized SWM ponds and uncontrolled outlets Site ID Table 51 Prioritization Results Total Prioritization Score (out of 100) Ranking UCO UCO UCO UCO P UCO UCO P P P UCO P P P P UCO-63w UCO P P UCO P P P P P P P-111-A P P P P P UCO P P ES (September 2015) Page 19

29 60 Development of Alternatives and Evaluation Criteria 61 General The Project Team considered various SWM alternatives that could provide control of one (1) or more of the SWM objectives that are being targeted at each of the 21 subject sites SWM objectives include water quality, erosion, quantity / flood and temperature control In most cases, if there are multiple SWM objectives that need to be met at one (1) site, then a combination of various alternatives may be required to fully satisfy the objectives In Sections 621 to 626 the technical considerations and social, natural environmental and economic effects of each alternative is described The alternatives have been categorized below based on what SWM objectives they can achieve and a summary is provided in Section Description of Alternatives 621 Do Nothing The Do Nothing alternative would involve retaining existing SWM facilities in their current condition and limited functionality, and allowing various storm sewer outlets throughout the City to continue to release stormwater into watercourses without any intermediate controls This alternative does not require any action from the City and there will be no immediate financial impacts However, by not providing any or only limited SWM, there is the potential for future negative impacts to the natural condition and habitat quality of downstream watercourses, due to erosion, sedimentation or reduced water quality By postponing this beneficial work the future costs of this work may be higher and in the meantime public and/or private landowners may incur costs in the case of damages resulting from an extreme storm event 622 Water Quality Control Install Oil-Grit Separator An oil-grit separator (OGS) is a manufactured structure consisting of one (1) or more underground chambers The OGS provides water quality treatment (by separating sediment, debris and oil from the water) of stormwater collected in sewers before the water is released into a SWM facility or watercourse A flow bypass weir is often included in the design of OGS units so that low flows enter the unit, and more intense flows from larger more infrequent storm events will be bypassed The purpose of the bypass is to reduce the potential for contaminants to be re-suspended in the stormwater ES (September 2015) Page 20

30 An OGS is a relatively low cost option that can significantly enhance water quality providing TSS removal A relatively small footprint of land is required to install an OGS Also an OGS can be installed in a relatively short amount of time allowing for minimal disturbance to local public and to the surrounding ground / environment during construction The structure is underground and there are no anticipated long-term impacts on public safety or aesthetics of a public space Presently the TRCA typically considers a maximum 50% TSS removal by a stand-alone OGS, based on the results of the New Jersey Department of Environmental Protection (NJDEP) testing protocol, for units that are sized for 80% TSS removal While these units do not achieve the Enhanced level of TSS removed, these can still be an effective means of improving water quality in areas where treatment currently does not exist Where feasible it is recommended to consider a treatment train approach in conjunction with an OGS to provide enhanced quality control This should be considered at the detailed design stage Convert Existing Facility into a Wet Pond This alternative involves converting an existing dry pond or wetland (which does not provide any or only a limited amount of water quality control) into a wet pond with a permanent pool that can fully meet MOE enhanced level quality control criteria The retrofit facility can potentially be contained within the same footprint as the existing facility and incorporate existing infrastructure This reduces the area disturbed during construction, the construction time period and the cost of the retrofit in comparison to constructing a new wet pond at a site where no SWM facility currently exists Construct a Forebay Construct a forebay within an existing facility at the facility inlet This involves excavation of a deeper depression with ponded water at the inlet and can improve or fully meet water quality control criteria This retrofit alternative contains the construction within the area of an existing dry or wet SWM facility, minimizing impacts to the surrounding area Construct a Quality Control Pond Construct a quality control pond where no facility currently exists (only an uncontrolled outlet exists) A quality control pond is also known as a wet pond and includes a forebay and a separate section of ponded water that allows sediment in the storm water to settle out and be contained within the pond This retrofit will result in a change of the current land use, more extensive construction work and greater costs ES (September 2015) Page 21

31 623 Erosion Control Construct an Extended Detention Facility Construct a surface storage facility that will hold back a specific quantity of storm runoff and release over an extended period of time to reduce erosion of the receiving watercourse A stand-alone extended detention facility is a dry pond, or the extended detention facility can be constructed vertically ontop of a quality control facility (wet pond) to minimize the area utilized for SWM control A surface storage facility is less costly than an underground facility that will be discussed in Section 626 A dry pond allows for recreational use of the land during dry periods Retrofit SWM Facility Outlet to Extend the Detention Time Modify or replace the existing outlet control structure to extend the amount of time it takes for water to drain out of an existing SWM facility (wet or dry pond) The retrofit facility can likely remain the same size as the existing facility and incorporate existing infrastructure This reduces the size of the construction site and costs 624 Quantity Control Retrofit SWM Facility Outlet to Provide Additional Storage for Quantity Control Modify, replace or add outlet control structures within an existing pond to allow the pond detain and control the release of stormwater from large rainstorms If the pond does not have storage space available to store this water, the pond will need to be expanded outward and/or vertically Construction activity will be limited to the immediate area surrounding the existing facility This alternative can fully meet flood control criteria if the necessary storage volume can be provided Construct a Quantity Control Facility Construct a surface storage facility that will hold back a specific quantity of storm runoff from large rainstorms and control the release of the water into the receiving watercourse A stand-alone flood control facility is a dry pond, or the flood control facility can be constructed vertically ontop of a quality control facility (wet pond) to minimize the area utilized for SWM control A surface storage facility is less costly than an underground facility that will be discussed in Section 626 A dry pond allows for recreational use of the land during dry periods ES (September 2015) Page 22

32 625 Temperature Control Install a Bottom Draw Outlet in a Wet Pond Modifying the outlet control structure to add a bottom draw pipe is a relatively low cost method to reduce the temperature of water released from the pond Runoff captured in ponds is released from the pond through a pipe located at the bottom of the pond where the water is furthest from the sun and the coolest This retrofit involves construction within an existing or newly constructed wet pond, reducing the area disturbed during constriction Install a Cooling Trench Construct a cooling trench within an existing or new SWM facility to cool water before it is released A cooling trench is fully underground The ground surface can be covered with grass A cooling trench is a cost effective alternative to achieve temperature control and construction work is limited to a small section of the pond Aquatic and Riparian Planting at a Pond This alternative involves planting aquatic vegetation in wet ponds and/or riparian vegetation around the perimeter of wet or dry ponds to provide shade Shading the water ponded within the SWM facility reduces the warming affects of the sun This alternative is relatively low cost and provides temperature control and improves the natural aesthetics of the SWM facility 626 Control of Multiple Stormwater Management Objectives Construct Underground Storage Units Construct underground storage facilities to collect and detain stormwater runoff Underground tanks or infiltration trenches can be used depending on desired function and surrounding soil type This alternative allows the ground surface to be used for recreation purposes and parking or light traffic The ground can be covered in grass or other landscaping and the detained water can be used for irrigation This alternative can be used for temperature control, and erosion and/or flood control depending on its design Construct Bioswales Construct vegetated open channels that convey, treat and attenuate stormwater runoff In areas with appropriate soil types, bioswales can increase infiltration of stormwater runoff, reducing the need for end-of-pipe controls Bioswales can be constructed within road right-of-ways in residential and commercial areas and can provide some degree of erosion, temperature and water quality control A large network of bioswales will provide the most benefit, however; this is costly and disruptions to the public during construction will be more prominent ES (September 2015) Page 23

33 Install a Perforated Pipe System Install long infiltration trenches or linear soakaway pits within road right-of-ways These are designed to both convey and infiltrate stormwater runoff By infiltrating stormwater some degree of erosion, temperature and water quality control can be achieved and the size of end-of-pipe controls is reduced A large network of perforated pipes will provide the most benefit, however; this is costly and disruptions to the public during construction will be more prominent Plant Vegetated Filter Strips along Watercourses Plant riparian and terrestrial vegetation along watercourses to create a densely vegetated area that will treat runoff from adjacent impervious areas This alternative can provide erosion, temperature and water quality control This alternative is most effective if the vegetated area is gently sloped allowing runoff velocities to slow down and sediment to be filtered out Expand the Size of an Existing SWM Facility An existing dry or wet pond can be expanded outwards or built up vertically to increase its capacity This alternative can provide additional flood and/or erosion and/or water quality control where a facility already exists that provides some degree of such control This alternative can be a cost effective solution where moderate improvement is needed and there is available space for expansion Construction activity will be limited to the immediate area surrounding the existing facility 63 Summary of Alternatives The following table provides a summary of the SWM objectives that can be achieved by each of the alternatives A check-mark indicates which objectives can be achieved by a specific alternative shown below in Table 61 below Table 61 Stormwater Management Objectives Achieved by Alternatives Stormwater Management Objectives Design Alternatives Water Quality Control Erosion Control Quantity Control Temperature Control Do Nothing Install OGS Convert Existing Facility into Wet Pond Construct a Forebay Construct a Quality Control Pond Construct an Extended Detention Facility Retrofit SWM Facility Outlet to Extend Detention ES (September 2015) Page 24

34 Table 61 Stormwater Management Objectives Achieved by Alternatives (Continued) Stormwater Management Objectives Design Alternatives Water Quality Control Erosion Control Quantity Control Temperature Control Retrofit SWM Facility Outlet to Control Major Events Construct a Quantity Control Facility Install a Bottom Draw Outlet in Wet Pond Install a Cooling Trench Aquatic and Riparian Plantings at Facility Construct Underground Storage Units (with or without infiltration) * * Construct Bioswales - Install a Perforated Pipe System - Plant Vegetated Filter Strip Along Watercourse Expand the Size of an Existing SWM Facility - * * * - * This alternative may not achieve all of the indicated SWM objectives This depends on the design of the alternative on a site-specific basis 64 Development of Evaluation Criteria Evaluation criteria were developed to reflect the definition of environment provided in the OEAA and the specific circumstances associated with this project All applicable comments were considered in the implementation of the criteria in order to correctly evaluate all instances that would affect the site, receiving watercourse and surrounding area Criteria were divided into categories, as listed below in Table 62 The criteria listed below were used for the evaluation of alternative solutions at each of the 21 top priority retrofit sites Table 62 Preliminary Evaluation Criteria Technical Constructability and accessibility Ability to meet SWM objectives, as applicable (ie quantity, quality, erosion and temperature control) Engineering best practices / innovative solution Natural Environment Impacts to wildlife and vegetation habitats Impacts / improvements based on SAR / ESA Social Impacts Requirement of easements or purchase of private lands Impacts to public and private properties due to construction and operations Effect on public safety Economic Considerations Capital costs Maintenance and operating costs Impact on future development and growth ES (September 2015) Page 25

35 70 Preferred Alternatives Using the evaluation criteria discussed in Section 64, the Project Team applied a net effects analysis to the alternative solutions discussed in Section 62, which involved the following steps: Identify potential effects; Develop and apply mitigation / compensation / enhancement measures; and, Determine net effects after mitigation measures have been applied The comparative evaluation was undertaken using a reasoned argument or trade-off method This method highlights the relative advantages and disadvantages of each alternative solution based on its identified net effects This allowed for a clear presentation of the key trade-offs between the various evaluation factors and the reasons why one (1) alternative solution is preferred over another As a result, the relative differences and key trade-offs between each alternative solution for the various factors are clearly understood, and a traceable rationale for selection of the preferred solution has been provided The details of the net effects analysis and comparative evaluation of the alternatives for each of the 21 top priority sites is included in Appendix F Refer to Map 7-1 (following report) or a map of the 21 top priority sites and their drainage areas A summary of the evaluation results is provided in Table 71 The preferred solution for each site that was identified through the net effects analysis is briefly described below in Sections 71 to 721 In most cases there were multiple SWM objectives that needed to be met at one (1) site and a combination of various alternatives was required to fully meet all of the objectives ES (September 2015) Page 26

36 City of Markham Target SWM Objectives Achieved Target SWM Objectives Flood Control Table 71 Summary of Alternative Evaluation Results Pond ID Uncontrolled Outlet ID w Erosion Control Water Quality Control Temperature Control Design Alternative N/A Do Nothing Water Quality Control OGS Water Quality Control Convert to Wet Pond Water Quality Control Construct Forebay Water Quality Control Construct Quality Control Pond Erosion Control Erosion Control Temperature Control Construct Extended Detention Facility Retrofit Pond Outlet to Extend Detention Bottom Draw Outlet in Wet Pond Temperature Control Cooling Trench Temperature Control Erosion and Temperature Control - or - Flood and Temperature Control Flood Control Flood Control Aquatic and Riparian Plantings at Facility Underground Storage (with or without infiltration) Retrofit Pond Outlet to Control Major Events Construct Quantity Control Facility ES (September 2015) Page 27

37 City of Markham Target SWM Objectives Achieved Water Quality, Erosion and Temperature Control Water Quality, Erosion and Temperature Control Water Quality, Erosion and Temperature Control Flood Control &/or Water Quality Control &/or Erosion Control Target SWM Objectives Flood Control Table 71 Summary of Alternative Evaluation Results (Continued) Pond ID Uncontrolled Outlet ID w Erosion Control Water Quality Control Temperature Control Design Alternative Bioswales Perforated Pipe System (infiltration in road right-of-ways) Vegetated Filter Strip Along Watercourse Expand Size of Existing Pond Preferred Solution Evaluated Option but not the Preferred Solution Not Applicable for this Site Targeted Stormwater Management Objective ES (September 2015) Page 28

38 71 Pond 5 The existing Pond 5 is a wet pond which provides quality and quantity control The target SWM objectives of the retrofit are erosion control and temperature mitigation The preferred alternatives are underground storage and aquatic / riparian plantings The underground storage will provide erosion control and temperature mitigation with minimal social and environmental impacts The plantings will provide temperature mitigation with social and environmental benefits 72 Pond 24 The existing Pond 24 is a wetland which provides partial quantity control The target SWM objectives of the retrofit are erosion control and water quality control The preferred alternative is an OGS for water quality control 73 Pond 38 The existing Pond 38 is a dry pond which provides partial quantity control and the target SWM objectives of the retrofit are erosion control and water quality control The preferred alternatives are an OGS for water quality control, retrofitting the existing pond outlet to extend the detention time for erosion control and expanding the size (deepening) of the existing pond to provide the storage volume required for erosion control 74 Pond 39 The existing Pond 39 is a dry pond which provides partial quantity control and the target SWM objectives of the retrofit are erosion control and water quality control The preferred alternatives are an OGS for water quality control, retrofitting the existing pond outlet to extend the detention time for erosion control and expanding the size of the existing pond to provide the storage volume required for full erosion control 75 Pond 45 The existing Pond 45 is a wetland which provides quantity control The target SWM objectives of the retrofit are erosion control, water quality control and temperature mitigation The preferred alternatives are an OGS, underground storage, a cooling trench and riparian plantings The OGS will provide quality control and the underground storage will provide erosion control and temperature mitigation prior to the existing pond The cooling trench and riparian plantings will provide temperature mitigation to water within and after leaving the pond ES (September 2015) Page 29

39 76 Pond 47 The existing Pond 47 is a wet pond which provides partial quality and erosion control The target SWM objectives of the retrofit are erosion control, water quality control and temperature mitigation The preferred alternatives are an OGS, underground storage, a cooling trench and riparian plantings The OGS will provide quality control and the underground storage will provide erosion control and temperature mitigation as a separate system from the pond The cooling trench and riparian plantings will provide temperature mitigation to water within and after leaving the pond 77 Pond 51 The existing Pond 51 is a wetland which provides partial erosion control The target SWM objectives of the retrofit are erosion control, water quality control and temperature mitigation The preferred alternatives are to convert the wetland to a wet pond, construct a forebay, retrofit the existing pond outlet to extend the detention time, expand the pond size, and install a bottom draw outlet and aquatic / riparian plantings The expansion of the pond, retrofit of the outlet, conversion into a wet pond and construction of a forebay will provide full quality and erosion control A bottom draw outlet and aquatic / riparian plantings will provide temperature mitigation 78 Pond 55 The existing Pond 55 is a wet pond which provides quality control and partial erosion control The target SWM objectives of the retrofit are erosion control and temperature mitigation The preferred alternative is installation of a cooling trench to provide temperature mitigation 79 Pond 62 The existing Pond 62 is a wet pond which provides quantity and quality control and partial erosion control The target SWM objectives of the retrofit are erosion control and temperature mitigation The preferred alternatives are retrofit of the existing pond outlet to extend the detention time for additional erosion control, installation of a cooling trench and aquatic / riparian plantings to provide temperature mitigation 710 Pond 73 The existing Pond 73 is a wet pond which provides quantity, quality and erosion control The target SWM objective of the retrofit is temperature mitigation The preferred alternatives are installation of a cooling trench and aquatic / riparian plantings to provide temperature mitigation ES (September 2015) Page 30

40 711 Pond 77 The existing Pond 77 is a wet pond which provides quantity, quality and erosion control The target SWM objective of the retrofit is temperature mitigation The preferred alternatives are installation of a cooling trench and aquatic / riparian plantings to provide temperature mitigation 712 Uncontrolled Outlet #8 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #8 are erosion control, water quality control and temperature mitigation The preferred alternative is an OGS for water quality control 713 Uncontrolled Outlet #55 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #55 are erosion control and water quality control The preferred alternative is an OGS for water quality control 714 Uncontrolled Outlet #63w The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #63w are erosion control and water quality control The preferred alternatives are an OGS for water quality control and underground storage for erosion control 715 Uncontrolled Outlet #66 The target SWM objective of the proposed new SWM facility at the existing uncontrolled outlet #66 is water quality control The preferred alternative is an OGS for water quality control 716 Uncontrolled Outlet #94 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #94 are erosion control, water quality control and temperature mitigation The preferred alternatives are an OGS for water quality control and underground storage for erosion control and temperature mitigation ES (September 2015) Page 31

41 717 Uncontrolled Outlet #103 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #103 are water quality control and temperature mitigation The preferred alternative is an OGS for water quality control By keeping the water underground (direct flow from the storm sewer system to an OGS and then to the well vegetated watercourse) further temperature mitigation is not required 718 Uncontrolled Outlet #106 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #106 are water quality control and temperature mitigation The preferred alternative is an OGS for water quality control By keeping the water underground (direct flow from the storm sewer system to an OGS and then to the well vegetated watercourse) further temperature mitigation is not required 719 Uncontrolled Outlet #112 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #112 are erosion control, water quality control and temperature mitigation The preferred alternative is an OGS for water quality control By keeping the water underground (direct flow from the storm sewer system to an OGS and then to the well vegetated watercourse) further temperature mitigation is not required 720 Uncontrolled Outlet #162 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #162 are erosion control, water quality control and temperature mitigation The preferred alternative is an OGS, and underground storage The OGS will provide water quality control The underground storage will provide erosion control and temperature mitigation 721 Uncontrolled Outlet #176 The target SWM objectives of the proposed new SWM facility at the existing uncontrolled outlet #176 are erosion control and water quality control The preferred alternative is an OGS for water quality control ES (September 2015) Page 32

42 City of Markham 80 Conceptual Design of SWM Improvements 81 General Based on the preferred retrofit options outlined in Section 70, conceptual designs will be developed and potential land or easement requirements will be assessed for the 21 retrofit sites The conceptual designs will be in accordance with City, MOE and TRCA design standards and good engineering practice The conceptual design of the preferred alternatives for each retrofit location is required to supplement the EA process and provide functional designs in sufficient detail to transition to detailed design 82 Objectives The objectives of the conceptual designs are summarized as follows: Assess the type(s) of retrofit proposed at each site; Verify if the retrofit is feasible within the subject area (ie confirm land requirements etc); Develop a preliminary / conceptual functional design of the retrofit; Confirm at a conceptual level if the proposed retrofits will meet all design criteria which consist of: Quantity Control as specified in the TRCA SWM Criteria on a site-by-site basis; Quality Control MOE Enhanced (Level 1) Protection; Erosion Control 48-hour detention of the 25 mm, 4-hour Chicago storm; Temperature Control; and, Physical Pond Characteristics and Dimensions MOE guidelines and City s guidelines Provide recommendations to consider at the detailed design stage The following guidelines were referenced for SWM design criteria: MOE SWM Planning and Design Manual (2003); TRCA SWM Criteria Draft Version 10 (April 2012), (TRCA SWM Criteria); and, City Design Criteria for Storm Drainage and SWM (April 2012) 83 Methodology The existing subject sites requiring retrofits are categorized into two (2) types: SWM Pond Retrofit (existing wetland, wet pond or dry pond); and, Uncontrolled Area Retrofit (uncontrolled outfall discharging to a watercourse) The procedure of retrofitting each site to meet design criteria requirements is discussed in Sections 831 to 841 It is noted as certain aspects of the methodology differ based on the subject site type (ie SWM Pond Retrofit vs Uncontrolled Area), a subheading is provided differentiating the procedure undertaken ES (September 2015) Page 33

43 831 Quantity Control SWM Pond Retrofit The 100-year storm event for both the 12-hour and the 3-hour AES storms was modelled The 12-hour storm had a smaller peak flow than the 3-hour AES, therefore; the 12-hour storm peak flow was used as a more conservative target flow The 12-hour storm was used when modelling the post-development peak flows for the purposes of the conceptual design of SWM facility retrofits throughout the City, as identified through this Municipal Class EA At the detailed design stage, the 12-hour SCS storm event should be modelled for all retrofit projects within the Don River Watershed, as per the TRCA Stormwater Management Criteria for the Don River Watershed The following steps outline the methodology and procedure undertaken to provide quantity control with the preferred alternative for a SWM pond retrofit: a) Drainage Area Delineation Major and minor drainage areas are delineated through existing contours and storm sewer mapping extracted from the City s SWMSoft database The major and minor drainage areas established through SWMSoft will be utilized to calculate pre-development and post-development drainage area parameters, flow directions, outlet locations and retrofit constraints The delineated drainage areas will be used for all SWM pond sizing and control sizing Drainage area plans for the 21 retrofit sites are provided in Appendix G b) Surface Generation Existing contour mapping and DEM data will be used to generate a 3D surface of the existing pond block area using Civil 3D software Existing bathymetric surveys of the existing pond will be added to the surface to further define the pond shape below the permanent water level c) Target Release Rate The pre-development release rate as set out in the existing SWM report for each existing pond will be used as the target quantity control release rate (if available) If the existing SWM report is not available, a conceptual pre-development hydrologic model will be generated to calculate the target release rate ES (September 2015) Page 34

44 d) Hydrologic Modelling Background The hydrologic model will be generated using Visual OTTHYMO Version 30 (VO3) software This modelling software allows users to model the storm effects and define the hydrologic input parameters of a given site area The main modelling inputs used in the update are described below: STANDHYD Command: An area input command mainly used for impervious drainage areas; and, Impervious area input parameters may be assigned to this command NASHYD Command: An area input command mainly used for pervious drainage areas; and, Pervious area input parameters may be assigned to this command ADDHYD Command: An input command used to add two (2) areas together ROUTE RESERVOIR Command: A command used to represent a SWM pond or control device; and, The user may input a rating curve to represent a storage-discharge relationship of a SWM pond or control device The input value for the percent imperviousness of the drainage area will be based on values provided in Section E of the Town of Markham Standard Drawing and Design Criteria, July 2003 or of the Town of Markham Engineering Standards, April 2012 Either the old or current standards will be used (based on the estimated age of the surrounding development) to maintain consistency with the standards that were used in the design of the existing SWM facility / infrastructure e) Hydrologic Model Setup Run the pre-development NASHYD command in VO3 using the City s design storms and determine the target release rate (if required); Run the post-development STANDHYD command in VO3 using the City s design storms and determine the post-development peak flow; and, Add a ROUTE RESERVOIR command to the model to represent the existing SWM pond and populate the command with a high level stage-storage-discharge table f) Resizing of Pond Outlet Adjust the stage-storage-discharge table to represent a functional control until the SWM pond meets the quantity control design objectives; Determine the additional storage required to meet quantity control design criteria and apply the preferred retrofit alternative; and, Generate conceptual plan and profile figures of the proposed retrofit and provide supporting calculations and details ES (September 2015) Page 35

45 Uncontrolled Area The methodology for retrofitting an uncontrolled area for quantity control will be similar to a SWM Pond Retrofit and follow steps (a) to (f) as per above However; the following revisions apply: (b) A bathymetric survey will not be implemented into the surface; (c) The target release rate will not be determined from an existing SWM report; (e) A new SWM pond and/or storage device will be implemented for the uncontrolled area; and, (f) A new pond outlet will be sized to meet water quantity objectives 832 Quality Control SWM Pond Retrofit a) Water Quality Sizing Based on the delineated drainage area and imperviousness, the required water quality volume to meet Enhanced Levels (MOE 2003 Guidelines) will be determined Level 1 protection consists of an 80% TSS removal requirement Dependant on the type of retrofit, either an OGS or a SWM pond with a permanent pool will be designed to meet water quality requirements b) OGS Sizing OGS devices sized to meet 80% TSS removal will be added upstream of the outlet or control If multiple OGS devices are required, they will be inserted at upstream of any discharge points c) Permanent Pool Sizing The additional permanent pool volume required to meet water quality objectives will be checked against the existing permanent pool volume in the SWM pond (if applicable) If additional volume is required, the permanent pool will be resized to provide the required volume Uncontrolled Area The methodology for retrofitting an uncontrolled area for quality control will be similar to a SWM Pond Retrofit and follow steps (a) to (c) as per above However; the following revisions apply: (c) A new SWM pond and/or storage device will be implemented for the uncontrolled area and a permanent pool will be sized if a new SWM pond is to be implemented ES (September 2015) Page 36

46 833 Erosion Control SWM Pond Retrofit a) Erosion Control Volume The 25 mm storm event will be run in VO3 during post-development conditions to determine the erosion control volume required to be detained This volume will be checked against the pond surface to determine the extended detention head b) Extended Detention Time and Orifice Sizing Utilizing the MOE drawdown calculation, SWM pond or control surface area, extended detention head and typical orifice sizing, the erosion control extended detention objective (48-hours) will be achieved FlowMaster Software will be used to confirm the orifice sizing Note that StormTech underground storage chambers will typically be used for sizing underground storage facilities However, this does not limit the design at the implementation stage to this particular product, equivalently performing products are acceptable A uniform storage area is assumed in the drawdown calculation for the StormTech underground chambers as stones below, surrounding and above the chambers are considered in the storage volume calculation; thus the overall storage tank has a uniform surface area c) Pond and Outlet Resizing If the existing SWM pond has insufficient volume to meet the erosion control requirements, the active storage will be increased and berm elevation adjusted In addition, modifications to the existing SWM pond controls (ie orifice size or invert adjustment) will be made to achieve the erosion control objectives It is noted, all adjustments to existing SWM ponds to meet erosion control requirements will be co-ordinated to ensure the existing functionality of the pond is not affected (ie quantity control etc) Uncontrolled Area The methodology for retrofitting an uncontrolled area for erosion control will be similar to a SWM Pond Retrofit and follow steps (a) to (c) as per above However, the following revisions apply: (c) A new SWM pond and/or storage device will be implemented for the uncontrolled area and the orifice will be sized to accommodate the required erosion control volume in the new SWM facility ES (September 2015) Page 37

47 834 Temperature Control SWM Pond Retrofit a) Cooling Trench Certain watercourses in the City are regulated by MNR as Redside Dace habitat and as such require lower stormwater temperatures to be discharged to the receiving watercourse Opportunities to provide temperature mitigation measures will be investigated and implemented where appropriate Where possible; a cooling trench will be implemented within the storm sewer infrastructure downstream of the existing SWM pond control b) Terrestrial Plantings Where feasible, terrestrial plantings will be recommended along the banks of existing SWM facilities to provide cooling and reduce stormwater temperatures c) Bottom Draw Outlet If adjustments to the SWM pond outlet are required to meet one of the above SWM objectives (ie quantity, quality, erosion control), a bottom draw outlet will be implemented to further reduce stormwater temperatures before discharging to the receiving watercourse Uncontrolled Area The methodology for retrofitting an uncontrolled area for temperature control will be similar to a SWM Pond Retrofit and follow steps (a) to (c) as per above However; the following revisions apply: (a) A cooling trench will be implemented downstream of the new SWM facility; (b) Terrestrial plantings will be implemented along the perimeter of the new SWM facility; and, (c) A bottom draw outlet will be implemented within the new SWM facility 84 Individual Conceptual Design Summaries The relevant background information and details of the conceptual designs are described in this section Refer to Appendix G for the drainage area plan and a drawing of each conceptual pond retrofit or new SWM facility design as well as all calculations related to the retrofit design including cost estimates ES (September 2015) Page 38

48 841 Conceptual Design Summary Pond Background Pond 5 is a wet pond located within Ashton Meadows Park, a City owned park, at the northeast corner of Woodbine Ave and Calvert Road, and discharges to Apple Creek of the Rouge River watershed The closest major intersection is 16 th Avenue and Woodbine Avenue The downstream receiving watercourse has been identified as Redside Dace habitat, as advised by MNR, therefore; the temperature of the released stormwater is a targeted parameter Background information was obtained from the following sources: The City s SWMSoft Database; Buttonville North Master Drainage Plan by Cosburn Patterson Wardman Ltd and Micheal Michalski Associates, dated July 1990; and, Addendum to the Revised Buttonville North Master Drainage Plan by Schaeffer & Associates Ltd, dated April 1997, revised June 1998 Pond 5 was designed as a quantity control pond and also provides adequate quality control for the minor drainage area The pond receives major storm discharge from Pond 6 via a flow splitter and box culvert under Woodbine Avenue, as well as minor system runoff from Woodbine Avenue and the surrounding area 8412 Criteria The objectives of the conceptual SWM facility retrofit design are to provide: Erosion Control (48-hours of extended detention); and, Temperature Control 8413 Existing Conditions The minor drainage area is comprised of residential town houses, park land and roadways The existing conditions hydrologic input parameters are summarized below Table 81 below Table 81 Pond 5 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 982 TIMP 28% XIMP 28% ES (September 2015) Page 39

49 8414 Proposed Retrofit Conditions Underground storage chambers are proposed to provide the detention storage required for erosion control Table 82 below summarizes the level of SWM control required and provided for the proposed SWM retrofit Table 82 Pond 5 Summary of Stormwater Management Control Achieved Parameter Required Provided by Retrofit Extended Detention Release Rate 48 hours 49 hours Erosion Control Detention Volume 1,175 m 3 1,175m 3 Erosion Control An underground storage chamber within the park land is proposed to provide storage for the extended detention of the 25 mm rain event A total of 1,175 m 3 of storage is required to detain the 25 mm rain event for an extended detention of 48-hours A total of 1,175 m 3 of storage can be provided based on a StormTech SC-310 Chamber with a footprint of 3,013 m 2 The following parameters were used in the storage calculations: An SC-310 Chamber with 0152 m of clear stone below and 0152 m of clear stone above the chamber has an available storage volume of /m 2 of tank footprint (as per StormTech Product Catalogue, 2011); It was assumed that the water stored below the outlet invert (in the lower 0152 m of clear stone below the chamber) will infiltrate into the ground allowing this portion of the storage facility to be considered active and available storage (but not head acting on the outlet); and, A total tank footprint of 3,013 m 2 is required to provide 1,175 m 3 of storage The tank system will have an outlet invert of m, a maximum head of 025 m and the discharge rate will be controlled by an 85 mm diameter orifice plate on the tank outlet control structure To meet erosion control criteria, a volume of 1,175 m 3 will be stored within the tank and released over a period of approximately 49-hours While the existing pond provides adequate quality control, it is proposed to include an isolator row at the inlet to the underground storage system This isolator row will act to settle out sediment before the stormwater travels through the remainder of the chambers, thus reducing the maintenance required Temperature Control Pond 5 is currently surrounded by trees however; additional trees could be planted to completely surround the pond and provide additional shading of the stored stormwater Also by temporarily storing the stormwater within the underground storage chamber, the stormwater is being protected from the warming effects of the sun Therefore, the water discharged from the underground storage tank will be cooler than the water that is currently discharged from the pond ES (September 2015) Page 40

50 8415 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $685,20000, shown below in Table 83 The proposed SWM facility is located within the City s lands so land acquisition is not required Table 83 Pond 5 Cost Estimate Item Construction $507,50000 Engineering Fees (20%) $101,50000 Contingency (15%) $76,20000 Total $685,20000 Cost Estimate 8416 Conclusions and Recommendations The existing Pond 5 provides quality and quantity control The proposed retrofit involves constructing an underground storage chamber under an existing soccer field within City owned park land This retrofit will provide erosion control of the 25 mm rain event released over 49-hours and temperature control Detaining the storm water within an underground chamber rather than expanding the existing pond allows for the land to continue to be used as a public recreational park and for existing trees to be retained Additional trees planted around the pond are proposed to provide increased shading of the detained stormwater It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures for this watercourse The construction of the underground storage facility involves the excavation of approximately 3,500 m 3 of earth and disposal of approximately 2,870 m 3 of earth As this facility discharges to a watercourse that is Redside Dace habitat and sedimentation during construction has a significant negative impact on Redside Dace habitat, it is recommended that stringent erosion and sediment controls be implemented during construction It should be noted Pond 5 is one (1) pond in a system of seven (7) ponds for the Buttonville North Master Drainage Plan The water discharged by one (1) pond often flows into and is captured by another pond (as a number of the ponds in the system are online) Therefore; to have a lasting improvement on the temperature of the water in the watercourse, temperature mitigation measures should be taken at the other ponds within the system For example, the pond immediately upstream of Pond 5 is Pond 6 which has a large permanent pool surface area with very little shade Plantings and a cooling trench at the Pond 6 outlet is recommended to reduce temperatures within Apple Creek and the Rouge River Ponds 2, 3 and 4, located downstream of Pond 5, are online ponds with minimal shading It is recommended that trees and riparian vegetation be planted at these ponds ES (September 2015) Page 41

51 842 Conceptual Design Summary Pond Background Pond 24 is an offline wetland that was built in 1982 as a dry pond to provide 2-year post-to-pre flood control The 06 ha pond block is located within a natural creek corridor at the south-west intersection of Bronte Road and Green Lane and outlets to German Mills Creek of the Don River watershed The closest major intersection is John Street and Leslie Street The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat, as advised by MNR, so the temperature of the released storm water is not a targeted parameter 8422 Criteria The objective of the conceptual SWM facility design is to provide: Erosion Control (48-hours of extended detention); and; Water Quality Control (80% TSS removal) Quantity control is required in this section of the Don River Watershed, as per TRCA SWM Criteria (August 2012) However; there is not enough land available to provide storage for the major storm events due to the presence of mature trees which are to be preserved 8423 Existing Hydrologic Conditions The minor and major drainage areas to Pond 24 are comprised entirely of single-family residential land use and roadways The existing wetland discharges along the northeast bank of German Mills Creek downstream of Green Lane A summary of the existing condition hydrologic input parameters are included below in Table 84 below Table 84 Pond 24 Existing Conditions Hydrological Parameters Parameter 24-Minor Drainage Area 24-Major Drainage Area Size (ha) TIMP 43% 43% XIMP 43% 43% 8424 Proposed Retrofit Conditions An OGS is proposed to provide the required water quality Due to space limitations, it is not feasible to improve erosion control, as discussed further below Table 85 below summarizes the level of SWM control required and provided by the proposed SWM pond retrofit Table 85 Pond 24 Summary of Stormwater Management Control Achieved Parameter Required Provided by Retrofit TSS Removal 80% 82% Extended Detention Release Rate 48 hours 3 hours (provided by existing pond) Erosion Control Detention Volume 2,870 m 3 1,542 m 3 (provided by existing pond) ES (September 2015) Page 42

52 Erosion Control The existing pond outlet control structure is a concrete wall approximately 18 m tall with a 250 mm diameter CSP pipe through the base of the wall The concrete wall is bounded by earthen berms and gabions basket walls Given the existing conditions of the pond, Pond 24 provides an extended detention of 3-hours To avoid the removal of mature trees, the existing pond grading is to be retained The opportunity to adjust the pond outlet in order to provide additional erosion control was analyzed The pond spillway can be raised by 016 m while still providing the minimum 03 m of freeboard between the top of berm and spillway This can provide an additional 325 m 3 of storage for a total of 1,867 m 3 This volume is not adequate for storing the 25 mm erosion control storm event therefore; full erosion control cannot be provided Additionally, the pond outlet pipe would have to be reduced in size to achieve a longer extended detention With the increased storage volume of 1,867 m 3 and the minimum allowable orifice size of 100 mm, an only extended detention of 22-hours is achievable Given that the erosion control requirement cannot be fully achieved it is concluded that a retrofit for improved erosion control is not desirable for the amount of disturbance the construction of the retrofit would cause Quality Control An OGS is proposed to provide water quality treatment The OGS will be located upstream of the pond, under the boulevard within the Green Lane road right-of-way A CDS model PSWC56_68_10, or approved equivalent, is recommended and will remove 82% of TSS for the minor drainage area 8425 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $246,25000 shown below in Table 86 below The proposed SWM facility is located within the City s property therefore land acquisition is not required Table 86 Pond 24 Cost Estimate Item Construction $197,00000 Engineering Fees (10%) $19,70000 Contingency (15%) $29,55000 Total $246,25000 Cost Estimate ES (September 2015) Page 43

53 8426 Conclusions and Recommendations The recommended retrofit to provide additional SWM controls to existing Pond 24 consist of an OGS within the City owned road right-of-way This retrofit will enhance the quality control for this retrofit opportunity Expansion of the existing SWM pond was not an option due to the presence of mature trees which are to be retained It was determined that adjusting the pond outlet would provide a minimal improvement to erosion control in contrast to the amount of site disturbance and tree loss that would be required and therefore improvements to erosion control are not proposed 843 Conceptual Design Summary Pond Background Pond 38 is an offline dry pond that was built in 1985 as part of Phase 3 of the Bridle Trail subdivision to provide flood control of the 2-year storm event The pond outlets to Eckardt Creek of the Rouge River watershed The closest major intersection to the pond is Kennedy Avenue and 16 th Avenue The pond is located within the floodplain of Eckardt Creek, east of the south limit of Wrenwood Court The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat so the temperature of the released water is not a targeted parameter Existing detailed pond design information for Pond 39 was obtained from the City s SWMSoft database The primary source of information is a report titled Bridle Trail, Phase III, Town of Markham, SWM Report for Monarch Construction Limited, dated May 1985 and completed by Marshall Macklin Monaghan Ltd The as constructed drawing titled Storm Sewer Outfall and Detention Pond, Project No , Drawing No 9, dated January 20, 1988 by Marshall Macklin Monaghan Ltd was also reviewed 8432 Criteria The objective of the conceptual retrofit design is to provide: Quality Control (80% TSS removal); and, Erosion Control (48-hours of extended detention) According to the April 2012 TRCA SWM Criteria, quantity control is not required at this location since stormwater is released into Eckardt Creek (formerly Burndenett Creek) downstream of 16 th Avenue ES (September 2015) Page 44

54 8433 Existing Hydrologic Conditions The existing Pond 39 SWM facility provides post-to-pre peak quantity control of the 2-year storm event and a reduced level of control of the 5- to 25-year storm events where the peak flow is greater than in the pre-development condition The minor drainage area to Pond 38 is comprised of single-family residential land use The pond block is bounded to the north by private residential lots, to the east by Eckardt Creek, to the south by a naturalized creek corridor and to the west by parkland The existing conditions hydrologic input parameters are summarized below in Table 87 Table 87 Pond 38 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 1816 TIMP 43% XIMP 43% 8434 Proposed Retrofit Conditions Deepening the existing pond to increase the storage capacity and retrofit of the existing pond outlet is proposed to provide the extended detention storage required for erosion control An OGS is proposed to provide water quality control Table 88 below summarizes the level of SWM control required and provided for the existing pond and proposed pond retrofit Table 88 Pond 39 Summary of Stormwater Management Control Achieved Parameter Required Provided by the Existing Facility Provided by the Retrofit Facility TSS Removal 80% 0% 83% Extended Detention Release Rate 48 hours 1 hour 478 hours Erosion Control Detention Volume 2,705 m 3 1,640 m 3 2,190 m 3 Quality Control An OGS is proposed within the Wrenwood Court right-of-way and upstream of the existing pond to provide water quality treatment A CDS model PSWC56_68, or equivalent, is recommended and will remove 83% of TSS for the minor drainage area Calculations are provided in Appendix G ES (September 2015) Page 45

55 Erosion Control Retrofit of the existing pond outlet and deepening the existing pond to provide more storage is proposed to provide the required storage and drawdown time for the extended detention of the 25 mm rain event To meet erosion control criteria, a volume of 2,705 m 3 must be stored and released over a period of 48-hours The existing pond has a footprint of 2,200 m 2, provides 2,705 m 3 of storage with a maximum erosion control detention water depth of 146 m A 375 mm diameter outlet set at an invert elevation of m results in a drawdown time of 1-hour The proposed pond will have to same footprint as the existing pond to limit impacts on the natural heritage features in the valley lands A 90 mm diameter orifice plate at the pond outlet, set at an invert elevation of m provides a drawdown time of approximately 48-hours By raising the elevation of the spillway, and deepening the pond as feasible while maintaining the existing outlet invert, a maximum erosion control detention water depth of 157 m provides 2,190 m 3 of storage Although the storage volume of the pond is less than the volume of water that needs to be stored, this pond will be able to provide full erosion control This is because the runoff from the 25 mm design storm will not instantaneously arrive at the pond; rather the water will gradually arrive at the pond as other water is being released from the pond 8435 Cost Estimate and Land Availability The total estimated cost of the recommended retrofit is approximately $277,000 shown below in Table 89 below The proposed SWM facility is located within the City s lands; therefore additional land acquisition is not required Table 89 Pond 38 Cost Estimate Item Construction $221,60000 Engineering Fees (10%) $22,20000 Contingency (15%) $33,20000 Total $277,00000 Cost Estimate ES (September 2015) Page 46

56 8436 Conclusions and Recommendations The recommended retrofit to Pond 38 is a combination of an OGS, retrofit of the existing pond outlet controls and deepening the pond to increase the storage volume This retrofit will enhance the quality control for this retrofit opportunity and will provide erosion control of the 25 mm rain event which will be released over 48-hours The construction of this dry pond facility involves grading within the floodplain along the Eckardt Creek with a net cut of approximately 350 m 3 This will not have a negative impact on the flood storage available in the floodplain It should be noted that modifying the outlet of the pond may affect the pond s existing quantity control performance for the 2-year storm event During detailed design of the pond retrofit, it is recommended that these effects be investigated to ensure that the proposed outlet modifications do not negatively impact the pond s quantity control performance 844 Conceptual Design Summary Pond Background Pond 39 is an offline dry pond that was built in 1986 as part of Phase 4 of the Bridle Trail subdivision to provide flood control of the 2-year storm event The pond outlets to Eckardt Creek of the Rouge River watershed The closest major intersection to the pond is Kennedy Avenue and 16 th Avenue The pond is located within the floodplain of Eckardt Creek, immediately to the east of St Matthew Catholic Elementary School The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat so the temperature of the released water is not a targeted parameter Existing detailed pond design information for Pond 39 was obtained from the City s SWMSoft database The primary source of information is a report titled SWM Report for Bridle Trail, Phase IV, Town of Markham, dated March 1986 and completed by Marshall Macklin Monaghan Ltd The as constructed drawing titled Storm Detention Pond and Outfall, Project No , Drawing No 17, dated January 1991 by Marshall Macklin Monaghan Ltd was also reviewed 8442 Criteria The objective of the conceptual retrofit design is to provide: Quality Control (80% TSS removal); and, Erosion Control (48-hours of extended detention) According to the April 2012 TRCA SWM Criteria, quantity control is not required at this location since stormwater is released into Eckardt Creek (formerly Burndenett Creek) downstream of 16 th Avenue ES (September 2015) Page 47

57 8443 Existing Hydrologic Conditions The existing Pond 39 SWM facility provides post-to-pre peak quantity control of the 2-year storm event The major drainage area to Pond 39 is comprised primarily of single-family residential land use while the minor drainage area is mix of commercial and single-family residential land use The pond block is bounded to the north by a naturalized creek corridor, to the east by Eckardt Creek, to the south by private residential lots and to the west by St Matthew Catholic Elementary School The existing conditions hydrologic input parameters are summarized below in Table 810 below Table 810 Pond 39 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Major Drainage Area Size (ha) TIMP 48% 42% XIMP 48% 42% 8444 Proposed Retrofit Conditions Expansion of the existing pond and retrofit of the existing pond outlet is proposed to provide the extended detention storage required for erosion control An OGS is proposed to provide water quality control Table 811 below summarizes the level of SWM control required and provided for the existing pond and proposed pond retrofit Table 811 Pond 39 Summary of Stormwater Management Control Achieved Parameter Required Provided by the Existing Facility Provided by the Retrofit Facility Alternative 1 Provided by the Retrofit Facility Alternative 2 TSS Removal 80% 0% 81% 81% Extended Detention Release Rate 48 hours 04 hours 49 hours 51 hours Erosion Control Detention Volume 2,690 m 3 1,300 m 3 2,770 m 3 2,705 m 3 Quality Control An OGS is proposed within the existing pond block and upstream of the proposed pond to provide water quality treatment A CDS model PSWC56_53, or equivalent, is recommended and will remove 81% of TSS for the minor drainage area ES (September 2015) Page 48

58 Erosion Control Alternative 1 Retrofit of the existing pond outlet and expansion of the existing pond is proposed to provide the required storage and drawdown time for the extended detention of the 25 mm rain event To meet erosion control criteria, a volume of 2,690 m 3 must be stored and released over a period of 48-hours The existing pond has a footprint of 1,450 m 2, provides 1,300 m 3 of storage with a 450 mm diameter outlet set at an invert elevation of m, which results in provides a drawdown time of 04-hours The proposed pond has a footprint of 3,200 m 2, provides 2,770 m 3 of storage with a 115 mm diameter outlet set at an invert elevation of m and provides a drawdown time of 49-hours It is noted that expanding the pond will require the removal of multiple trees which was previously identified as a constraint on the land available for construction However; as this reach of Eckardt Creek (previously named Burndenett Creek) has documented erosion problems and was recommended for retrofit in the Burndenett Creek Erosion Control Optimization Study, Phase 1 Final Report, dated January 2012 by Aquafor Beech Limited, it is recommended that the pond be expanded in order to provide full erosion control Other options for extended detention storage were investigated, such as underground storage facility in the location of the existing pond, but due to the existing storm sewer elevations and the creek elevation, this option is not feasible Retrofitting the pond outlet while maintaining the existing pond grading was also investigated; this option would only provide partial erosion control with an inadequate storage volume of 1,300 m 3 and a maximum drawdown time of 11-hours Therefore, the preferred retrofit option for this location that does not require additional land acquisition, is the proposed expansion of the existing pond Erosion Control Alternative 2 Another alternative for providing erosion control is to retain Pond 39 in its current condition and build an underground storage tank under the rear yard of the adjacent St Matthew Catholic Elementary School This alternative is contingent on the City obtaining an agreement with the School Board The underground storage chamber is proposed to be located within St Matthew Catholic Elementary School lands; at the southeast corner of the rear school yard under an existing sports field A total of 2,690 m 3 of storage is required to detain the 25 mm rain event for an extended detention of 48-hours A total of 2,705 m 3 of storage can be provided based on a StormTech MC-4500 Chamber with a footprint of 2,150 m 2 The following parameters were used in the storage calculations: An MC-4500 Chamber with 023 m of clear stone below and 031 m of clear stone above the chamber has an available storage volume of 135 m 3 /m 2 of tank footprint (as per StormTech Product Catalogue, 2011); Based on Ontario soil mapping it is anticipated that the water stored below the outlet invert (in the lower 023 m of clear stone below the chamber) will not infiltrate into the ground therefore, this portion of the storage facility cannot be considered active and available storage; ES (September 2015) Page 49

59 Assuming a stone porosity of 40%, the 023 m of clear stone below the chamber has 0092 m 3 /m 2 of storage volume Therefore, the underground storage chamber will have a total of only 1258 m 3 of active storage per m 2 of tank footprint; and, A total tank footprint of 2,150 m 2 can provide 2,705 m 3 of storage The tank system will have an outlet invert of m, a maximum head of 1829 m and the discharge rate will be controlled by a 120 mm diameter orifice plate A volume of 2,705 m 3 will be stored within the tank and released over a period of approximately 51-hours Calculations are provided in Appendix G 8445 Cost Estimate and Land Availability The total estimated cost of the recommended retrofit is approximately $427,30000 shown in Table 812 below The proposed SWM facility is located within the City s lands; therefore additional land acquisition is not required The total estimated cost of the alternative retrofit design is approximately $1,409,20000 shown in Table 812 A portion of the proposed SWM facility is located within privately owned land, owned by the School Board This will require the City to obtain an agreement with the School Board The costs associated with this agreement are not included in the cost estimate as they are variable dependent upon City negotiations with the School Board Table 812 Pond 39 Cost Estimate Item Alternative 1 Pond Expansion and OGS Construction $341,80000 Engineering Fees $34,20000 Contingency $51,30000 Total - Alternative 1 $427,30000 Alternative 2 Underground Storage Tank and OGS Construction $1,127,40000 Engineering Fees $112,70000 Contingency $169,10000 Total - Alternative 2 $1,409,20000 Cost Estimate ES (September 2015) Page 50

60 8446 Conclusions and Recommendations The recommended retrofit to for Pond 39 is a combination of an OGS, retrofit of the existing pond outlet controls and expansion of the existing pond This retrofit will enhance the quality control for this retrofit opportunity and will provide erosion control of the 25 mm rain event which will be released over 49-hours Although this retrofit requires the removal of a number of trees, the proposed pond design is strongly recommended as this reach of Eckardt Creek (previously named Burndenett Creek) has documented erosion problems and was recommended for retrofit in the Burndenett Creek Erosion Control Optimization Study, Phase 1 Final Report, dated January 2012 by Aquafor Beech Limited At the detailed design stage, efforts can be made to decrease the pond footprint by further optimizing the pond grading and outlet It is recommended to conduct a detailed vegetation and tree inventory as well as a detailed topographic survey to determine the approved limit of disturbance and allowable pond block size The construction of this dry pond facility involves grading within the floodplain along the Eckardt Creek with a net cut of approximately 3,460 m 3 This will not have a negative impact on the flood storage available in the floodplain It should be noted that modifying the outlet of the pond may affect the pond s existing quantity control performance for the 2- to 100-year storm events During detailed design of the pond retrofit, it is recommended that these effects be investigated to ensure that the proposed outlet modifications do not negatively impact the pond s quantity control performance An alternative to the above described recommended retrofit is a combination of an OGS and an underground storage tank while retaining the existing pond and pond outlet in its current condition This retrofit will provide quality control meeting the MOE Enhanced Level and erosion control of the 25 mm rain event which will be released over 51-hours This alternative is more expensive than the recommended retrofit, however; TRCA support of the recommended pond expansion design comes with multiple caveats which will require the City to undertake multiple studies prior to the implementation of this retrofit Therefore, the City may prefer to purse the alternative underground storage design However, the underground storage tank must be located under the rear yard of the adjacent St Matthew Catholic Elementary School; therefore, this alternative is contingent on the City obtaining an agreement with the School Board ES (September 2015) Page 51

61 845 Conceptual Design Summary Pond Background Pond 45 is an offline wetland that was built in 1987 to provide flood control The closest major intersection to the pond is Kennedy Road and 14 th Avenue The 07 ha pond block is located within Windfield Park and outlets to a ditch within CNR land which eventually discharges to the Rouge River While the wetland inherently provides some level of quality control, the SWM facility was not designed to provide quality or erosion control so it is expected that these SWM objectives are deficient in comparison to current standards 8452 Criteria The objective of the conceptual retrofit design is to provide: Quality Control (80% TSS removal); Erosion Control (48-hours of extended detention); and, Temperature Control The downstream receiving watercourse has been identified as possible Redside Dace habitat so the temperature of the released water is a parameter that needs to be controlled According to the April 2012 TRCA SWM Criteria, quantity control is not required at this site since the stormwater is released into the Main Rouge River downstream of Major Mackenzie Drive 8453 Existing Hydrologic Conditions Both the major and minor drainage areas to Pond 45 are a mix of parkland and single-family residential land use The pond block is bounded to the north by a railway and hydro corridor, to the east and west by residential lots and to the south by municipal park land and Windfields Road The existing conditions hydrologic input parameters are summarized below in Table 813 below Parameter Table 813 Pond 45 Existing Conditions Hydrological Parameters West Pond Inlet East Pond Inlet Direct Runoff Minor Minor Drainage Minor Drainage Drainage Area Area Area Size (ha) TIMP 50% 50% 0% 50% XIMP 50% 50% 0% 50% Major Drainage Area ES (September 2015) Page 52

62 8454 Proposed Retrofit Conditions An underground storage chamber is proposed to provide the detention storage required for meeting erosion control requirements Two (2) OGS units are proposed to provide water quality control prior to discharging to the underground chambers A cooling trench and plantings are proposed to provide cooling of the stormwater The minor drainage area was used to determine the amount of storage required for erosion control and to size the OGS units Table 814 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 814 Pond 45 Summary of Stormwater Management Control Achieved Parameter Required Provided by Retrofit TSS Removal 80% 80% and 82% Extended Detention Release Rate 48 hours 50 hours Erosion Control Detention Volume 2,920 m 3 3,160m 3 Quality Control Two (2) OGS are proposed to provide water quality treatment One (1) OGS will be located at each of the two (2) pond inlets, within the park lands A CDS model PSWC56_53, or equivalent, is recommended at the west pond inlet and can remove 82% of TSS for the minor drainage area A Stormceptor STC 9000, or equivalent, is recommended at the east pond inlet and can remove 80% of TSS for the minor drainage area The OGS units will be located prior to the proposed underground storage tank to minimize the accumulation of sediment within the storage tank and minimize the potential for the release of harmful substances into Pond 45 It is proposed to install a maintenance hole just within the City s park boundary, to divert flows into the OGS and/or the underground storage chamber Erosion Control An underground storage chamber within the park land is proposed to provide storage for the extended detention of the 25 mm rain event The chamber footprint required to achieve the necessary storage volume was based on a StormTech MC-3500 Chamber The following parameters were used in the storage calculations: An MC-3500 Chamber with 023 m of clear stone below and 031 m of clear stone above the chamber has an available storage volume of 109 m 3 /m 2 of tank footprint (as per StormTech Product Catalogue, 2011); It was assumed that the water stored below the outlet invert (in the lower 023 m of clear stone below the chamber) will infiltrate into the ground allowing this portion of the storage facility to be considered active and available storage (but not head acting on the outlet); and, A total chamber footprint of 2,880 m 2 is required to provide 3,140 m 3 of storage ES (September 2015) Page 53

63 The chamber system will have an outlet invert of m, a maximum head of 114 m and the discharge rate will be controlled by a 125 mm diameter orifice plate on the chamber outlet structure To meet erosion control criteria, a volume of 3,140 m 3 will be stored within the tank and released over a period of approximately 50-hours Stormwater stored within the underground chamber system will be released into Pond 45 The downstream 69 m section of invert diameter of a storm sewer between the maintenance hole on Grant s Place and the Pond 45 east inlet is required to be raised in order to connect to the proposed underground storage chamber There is an existing easement over this section of the sewer to facilitate this modification Since the downstream invert at the pond will remain unchanged, hydraulic impacts from adjusting the sewer will be minimized however; it is recommended that a storm sewer design sheet be developed at detail design to ensure the existing storm sewer system will not be negatively impacted by this adjustment Temperature Control Detaining water in a pond has a significant thermal effect on stormwater from the sun warming the exposed water By implementing an OGS to provide quality control, rather than a wet pond with a permanent pool, the significant thermal effects of having permanent standing water is eliminated Additionally, by providing extended detention storage underground, the warming effects of the sun are avoided Stormwater will be stored in the existing wetland downstream of the storage chambers for a period of time due to the quantity control function of the wetland The wetland contains dense vegetation that will shade of some of the stormwater However, tall trees would provide shade over a larger area of Pond 45 and are proposed along the south bank These plantings also provide a social benefit by creating a natural barrier between the SWM pond and the public using the park Additionally, a cooling trench is proposed at the outlet of the existing SWM pond to lower the temperature of water prior to discharge The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site ES (September 2015) Page 54

64 8455 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $2,159,10000 shown in Table 815 below The proposed SWM facilities and construction works are located within the City s lands or easements so land acquisition is not required Table 815 Pond 45 Cost Estimate Item Construction $1,727,30000 Engineering Fees (10%) $172,70000 Contingency (15%) $259,10000 Total $2,159,10000 Cost Estimate 8456 Conclusions and Recommendations The recommended retrofit to provide additional SWM controls to existing Pond 45 is a combination of two (2) OGS and an underground chamber system within the City s owned parkland, prior to the existing pond, as well as plantings and a cooling trench This retrofit will enhance the quality control for this retrofit opportunity, provide erosion control of the 25 mm rain event released over a minimum of 48-hours and temperature control Expansion of the existing SWM pond was not an option due to the requirement to retain the existing recreational parkland and existing mature trees Therefore, underground facilities are proposed These underground facilities provide the added benefit of protecting the detained water from the warming effects of the sun The construction of the underground storage facility involves the excavation and disposal of approximately 5,740 m 3 of earth It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures that are applicable for this watercourse 846 Conceptual Design Summary Pond Background Pond 47 is a wet pond located at the northeast corner of Roxbury Street and 14 th Avenue The pond is located within Roxbury Park, a City owned park and outlets to the Rouge River The downstream receiving watercourse has been identified as possibly being Redside Dace habitat therefore, the temperature of the released water is a targeted parameter ES (September 2015) Page 55

65 Background information was obtained from the following sources: The City s SWMSoft Database; An excerpt from Design Brief for the Extended Detention Pond Demarco / Webjo Residential Development by Schaeffer & Associates Ltd, February 1994, obtained from the TRCA; and, Technical Brief, Functional Drainage Analysis (Revised), Invar (York Limited Subdivision (19T ), Webjo Subdivision (19T-84073), Markham Road (Hwy 48) and 14 th Avenue by Fredd Schaeffer & Associates Ltd, May 1994, obtained from the TRCA Pond 47 was originally designed as an extended detention wet pond providing quality and erosion control for storm runoff from the first 25 mm of the 2-hour Chicago design storm All flows greater than 25 mm of the 2-hour Chicago design storm bypass the pond and discharge directly to the Rouge River The pond currently provides 910 m 3 of permanent pool, a drawdown time of 45-hours and has a 100 mm diameter orifice 8462 Criteria The objectives of the conceptual SWM facility design are to provide: Erosion Control (48-hour detention of the 25 mm, 4-hour Chicago storm); Water Quality Control (80% TSS removal); and, Temperature Control According to the April 2012 TRCA SWM Criteria, quantity control is not required at this location since stormwater is released into the Main Rouge River downstream of Major Mackenzie Drive 8463 Existing Hydrologic Conditions The minor drainage area is comprised of institutional, single-family and estate residential land use The existing conditions hydrologic input parameters are summarized below in Table 816 below Table 816 Pond 47 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 2301 TIMP 58% XIMP 58% ES (September 2015) Page 56

66 8464 Proposed Retrofit Conditions Underground storage chambers are proposed to provide extended detention storage for erosion control of the flows which bypass the existing pond An OGS unit is proposed to provide additional water quality control to meet TSS removal requirements A cooling trench and plantings are proposed to provide cooling of the stormwater Table 817 below summarizes the level of SWM control required and provided by the proposed pond retrofit Table 817 Pond 47 Summary of Stormwater Management Control Achieved Parameter Required Provided Existing Pond Additional Provided Proposed Retrofit TSS Removal 80% 25% of permanent 82% pool required for 80% TSS removal Extended Detention Release Rate 48 hours 45 hours 33 hours Erosion Control Detention Volume 3,570 m 3 2,600 m m 3 Erosion Control The existing pond provides 45-hours of extended detention of the first 25 mm of the 2-hour Chicago design storm which does not meet current SWM criteria of providing 48-hours for the 25 mm of 4-hour Chicago design storm An underground storage chamber is proposed to capture flow that is bypassing the existing pond and provide extended detention prior to discharging to Rouge River The underground storage chamber is proposed to be located within the park land along the existing bypass pipe A total of 3,570 m 3 of storage is required to detain the 25 mm rain event for an extended detention of 48-hours The existing pond provides 2,600 m 3 of storage for a deficit of 970 m 3 The total amount of additional storage the chambers can provide is limited by the footprint of available as well as the elevation of the receiving watercourse and of the existing storm sewers Given these constraints, a total of 810 m 3 of storage can be provided based on a StormTech MC-4500 Chamber with a footprint of 600 m 2 The following parameters were used in the storage calculations: An MC-4500 Chamber with 023 m of clear stone below and 031 m of clear stone above the chamber has an available storage volume of 135 m 3 /m 2 of tank footprint (as per StormTech Product Catalogue, 2011); It was assumed that the water stored below the outlet invert (in the lower 046 m of clear stone below the chamber) will infiltrate into the ground allowing this portion of the storage facility to be considered active and available storage; An additional 023 m of clear stone was considered below the chamber (for a total of 046 m of stone below the chamber) Assuming a stone porosity of 40%, this provides an additional 009 m 3 /m 2 of storage for a total of 144 m 3 of storage per m 2 of tank footprint; ES (September 2015) Page 57

67 An additional 045 m of clear stone was considered above the chamber (for a total of 076 m of stone above the chamber) Assuming a stone porosity of 40%, this provides an additional 018 m 3 /m 2 of storage for a total of 162 m 3 of storage per m 2 of tank footprint The top of the clear stone layer above the chamber will be at an elevation of m, which is below the invert of the storm sewer pipe connection to the maintenance hole upstream of the chamber (16799 m) Therefore; it can be assumed that the storm water will fill this upper portion of stone and this stone can be considered active and available storage; and, A total tank footprint of 600 m 2 can provide 972 m 3 of storage The tank system will have an outlet invert of m, a maximum head of 228 m and the discharge rate will be controlled by a 75 mm diameter orifice plate A volume of 972 m 3 will be stored within the tank and released over a period of approximately 33-hours Since an orifice of 75 mm in diameter is the smallest allowable size, an extended detention of 33-hours is the maximum drawdown time achievable Quality Control The existing wet pond provides some level of quality control via a 1 m deep, 910 m 3 permanent pool According to background reports obtained from TRCA, the existing pond provides adequate quality control for the volume of stormwater that is captured by the pond However; all flows greater than 25 mm of the 2-hour Chicago design storm bypass the pond and discharge directly to the Rouge River untreated and uncontrolled Also according to Table 32 of the MOE SWMPP Planning & Design Manual, 2004, a permanent pool of 3,623 m 3 is required to provide 80% TSS removal from the minor system runoff Therefore; the existing SWM system is not meeting current SWM criteria An OGS is proposed to provide water quality treatment for the stormwater that is currently not being treated and is being discharged directly to the Rouge River The OGS will be located within Roxbury Park, downstream of the existing flow splitter and upstream of the proposed underground storage chamber Locating the OGS upstream of the proposed underground storage chamber will minimize the accumulation of sediment within the storage chamber and thereby minimize maintenance requirements A CDS model PSWC56_78, or approved equivalent, is recommended and will remove 82% of TSS for the catchment area Temperature Control The proposed retrofit is an underground facility and therefore, will not increase the temperature of the discharged stormwater A cooling trench is proposed at the outlet of the existing SWM pond to lower the temperature of water prior to discharging to Rouge River The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Due to the length of the outlet pipe from the pond to the junction maintenance hole, a cooling trench up to 10 m can be installed along the existing outlet Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site It is also recommended that additional trees and plantings be installed around the perimeter of the pond to provide additional shading of the permanently stored water in the pond ES (September 2015) Page 58

68 8465 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $729,00000 shown below in Table 818 The proposed SWM facilities and retrofits are located within City s lands so land acquisition is not required Table 818 Pond 47 Cost Estimate Item Construction $583,20000 Engineering Fees (10%) $58,30000 Contingency (15%) $87,50000 Total $729,00000 Cost Estimate 8466 Conclusions and Recommendations The existing Pond 47 provides some level of quality and erosion control, however; these controls do not meet current SWM standards The proposed retrofits include an OGS, and underground storage chambers, a cooling trench and additional plantings all within City s owned lands This retrofit will enhance the quality control for this retrofit opportunity and will provide partial erosion control of the 25 mm rain event released over 33-hours Detaining the storm water within an underground chamber rather than a surface detention facility allows for land to continue to be used as a public recreational park and protects the detained water from the warming effects of the sun, resulting in cooler water being discharged to the watercourse In addition, a cooling trench at the pond outlet and additional trees planted around the pond are proposed to provide cooling of the detained stormwater These recommendations are in line with the City s efforts in preserving and enhancing Redside Dace habitat within the City s watersheds The construction of the underground storage facility involves the excavation and disposal of approximately 1,640 m 3 of earth The proposed SWM facility construction will not have an effect on the available floodplain storage along the Rouge River It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures are applicable for this watercourse 847 Conceptual Design Summary Pond Background Pond 51 was constructed as part of a subdivision south of 14 th Avenue and west of Ninth Line The pond is located to the north of Remington Parkview Golf Course The pond discharges to the Rouge River The downstream receiving watercourse has been identified as possibly being Redside Dace habitat therefore; the temperature of the released water is a targeted parameter ES (September 2015) Page 59

69 Existing detailed pond design information for Pond 51 was obtained from the City s SWMSoft database This includes the following drawings: Drawing No 4 (Project No 87-18) titled Rouge North Fairways General Plan, January 1988; and, Drawing No 44 (Project No 87-18) titled Rouge North Fairways Storm Outfall, January 1988 The drawings were reviewed to determine the existing performance of the pond and evaluate if the pond meets the current SWM criteria of the TRCA, the MOE, and the City The existing facility provides only erosion control in the form of 24-hour detention of the 25 mm storm No other controls are provided 8472 Criteria The design criteria for the pond retrofit are as follows: Water Quality Control (80% TSS removal); Erosion Control (48-hour detention of the 25 mm, 4-hour Chicago storm); and, Temperature Control According to the April 2012 TRCA SWM Criteria, quantity control is not required at this location since stormwater is released into the Rouge River downstream of Major Mackenzie Drive 8473 Existing Hydrologic Conditions The existing conditions hydrologic input parameters are summarized below in Table 819 below Table 819 Pond 51 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 6063 TIMP 62% XIMP 62% ES (September 2015) Page 60

70 8474 Proposed Retrofit Conditions Conversion of the existing wetland cell into a wet pond and expansion of the pond is proposed to provide the permanent pool storage and extended detention storage required for quality and erosion control A bottom draw outlet and plantings around the pond are proposed to provide temperature control Table 820 below summarizes the level of SWM control required and provided for the existing pond and proposed pond retrofit Table 820 Pond 51 Summary of Stormwater Management Control Achieved Parameter Required Provided Existing Facility Provided Proposed Retrofit TSS Removal 80% - 80% Permanent Pool Volume 10,133 m 3 0 m 3 10,310 m 3 Extended Detention Release Rate 48 hours 24 hours 52 hours Erosion Control Detention Volume 9,570 m 3 2,600 m 3 11,070 m 3 Quality Control It is proposed to convert the existing wetland SWM facility into a wet pond by deepening the pond and raising the outlet invert A 1 m deep permanent pool with a water elevation of m will provide the required 10,133 m 3 of permanent pool storage for quality control Additionally, a forebay is proposed to enhance the water quality control and allow for easier maintenance of the pond Erosion Control Retrofit of the existing pond outlet and expansion of the existing pond is proposed to provide the required storage and drawdown time for the extended detention of the 25 mm rain event To meet erosion control criteria, a volume of 9,570 m 3 must be stored and released over a period of 48-hours The existing pond has a footprint of 6,040 m 2, provides 2,600 m 3 of storage with a 300 mm diameter outlet set at an invert elevation of 1530 m, which provides a drawdown time of 24-hours and a maximum water elevation of m The proposed pond will be deepened; expanded and taller berms will be built to provide the required storage volume The proposed pond has a footprint of 12,560 m 2 and provides 11,070 m 3 of active storage with a 220 mm diameter outlet set at an invert elevation of m and provides a drawdown time of 52-hours Temperature Control A bottom draw outlet is proposed for the wet pond to provide temperature mitigation of the water discharged from the pond It is also recommended that additional trees and plantings be installed around the perimeter of the pond to provide shading of the permanently stored water in the pond These plantings also provide a social and environmental benefit by restoring the subject site to its current naturalized condition and allowing the SWM facility to visually blend in with the surrounding valley land ES (September 2015) Page 61

71 8475 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $507,90000 shown below in Table 821 below The pond block is located within City s lands As such, there are no additional costs associated with land acquisitions Table 821 Pond 51 Cost Estimate Item Construction $406,30000 Engineering Fees (10%) $40,65000 Contingency (15%) $60,95000 Total $507,90000 Cost Estimate 8476 Conclusions and Recommendations The existing Pond 51 provides some level of erosion control, however; these controls do not meet current SWM standards The proposed retrofits include deepening and expanding the facility, converting the existing wetland into a wet pond, retrofitting the outlet structures to include a bottom draw outlet and accommodate a permanent pool and provide extended detention and additional plantings all within City s owned lands This retrofit will provide quality control meeting the MOE Enhanced Level, erosion control of the 25 mm rain event released over 52-hours and temperature control These recommendations are in line with the City s efforts in preserving and enhancing Redside Dace habitat within the City s watersheds It is noted, the construction of the expanded pond involves building taller berms within the floodplain along the Rouge River with a net fill of approximately 1,760 m 3 This results in a decrease in the available floodplain storage volume An equivalent cut will be required within the floodplain immediately upstream of the proposed SWM facility It is recommended that a potential cut-fill analysis be investigated during the detailed design stages of this SWM facility In addition, consultation with TRCA staff should be conducted prior to implementation The existing pond outlet channel is lined with gabions Replacement of the gabions with a more suitable alternative should be considered, contingent on budgeting constraints and the condition and remaining life span of the existing gabion lining It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures are applicable for this watercourse Additionally, a study to establish the appropriate limit of the pond expansion in relation to the 25-year erosion hazard limit will be required prior to implementation ES (September 2015) Page 62

72 848 Conceptual Design Summary Pond Background Pond 55 was constructed at the southern limit of a subdivision called Rouge Fairways, located south of 14 th Avenue and west of Ninth Line The pond is located at the southernmost part of the subdivision, north of Remington Parkview Golf Course and south of Lemsford Drive The pond discharges to the Rouge River Existing detailed pond design information for Pond 55 was obtained from the City s SWMSoft database These include the following drawings and reports: Drawing No D-1 (Project No 97-E-1935) titled Rouge Fairways Subdivision, Control Flow Structure Details, As Constructed - September 2003; Drawing No PP-8 (Project No 97-E-1935) titled Rouge Fairways Subdivision, Plan and Profile, Storm Sewer Outfall from Sta to Sta , revised October 1999; Functional Servicing Report for the Draft Plan of Subdivision, Part of Part 1, 64R-7287, Town of Markham by Schaeffers Consulting Engineers, dated June 1997; and, SWM Design Plan, Major and Minor System Analysis, Rouge Fairways Subdivision, Town of Markham by Schaeffers Consulting Engineers, dated July 1998 The drawings were reviewed to determine the existing performance of the pond and evaluate if the pond meets the current SWM criteria of the TRCA, the MOE, and the City The existing facility provides only erosion control in the form of 24-hour detention of the 25 mm storm and quality control through a permanent pool Quantity control has not been provided and is not required in this part of the Rouge River watershed, based on TRCA criteria 8482 Criteria The design criteria for the pond retrofit are as follows: Erosion Control (Provide 48-hour extended detention of the 25 mm storm event); and, Temperature Control The receiving watercourse has been identified as potential habitat for Redside Dace, an endangered cold-water fish species As the TRCA is actively looking to preserve its habitat within its jurisdiction, the EA process recommends that the existing SWM facility be retrofitted to provide some form of temperature control ES (September 2015) Page 63

73 8483 Existing Hydrologic Conditions The existing conditions hydrologic input parameters are summarized below in Table 822 below Table 822 Pond 55 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 647 TIMP 43% XIMP 43% 8484 Proposed Retrofit Conditions A cooling trench is proposed to provide temperature control Due to space limitations, it is not feasible to improve erosion control, as discussed further below Table 823 below summarizes the level of SWM control required and provided by the proposed SWM pond retrofit Table 823 Pond 55 Summary of Stormwater Management Control Achieved Parameter Required Provided Existing Pond Provided Proposed Retrofit Extended Detention Release Rate 48 hours 24 hours 24 hours (no retrofit to provide additional detention time) Erosion Control Detention Volume 871 m m m 3 (no retrofit to provide additional storage) Erosion Control Based on the Functional Servicing Report (Schaeffers Consulting Engineers, June 1997), the pond was to provide 741 m 3 of erosion control volume This volume was determined using a C value of 0463 However, the pond was later modified and the as-constructed drawings show that the pond only provide 24-hours of extended detention with 660 m 3 of erosion control volume Based on the hydrology model developed by the Project Team, a volume of 871 m 3 is required to provide extended detention Because the pond currently only provides 660 m 3, it is currently undersized by a volume of 212 m 3 Outflow from the existing pond is controlled by a 90 mm orifice, located at outlet control flow structure For the 659 m 3 of erosion control volume provided in the pond, the orifice is correctly sized for 24-hour drawdown time of the 25 mm storm In order to avoid the removal of mature trees, the existing pond grading is to be retained The opportunity to adjust the pond outlet in order to provide additional erosion control was analyzed The pond s orifice could be reduced from 90 mm to the minimum allowed size of 75 mm, in order to provide an additional 10-hours of draw down for the erosion control volume that the existing pond can store (660 m 3 ) Given that the erosion control requirement cannot be fully achieved, both in terms of volume and draw down time, it is concluded that a retrofit for improved erosion control is not desirable for the amount of disturbance the construction of the retrofit would cause ES (September 2015) Page 64

74 Temperature Control An 8 m long cooling trench is proposed along the existing 1200 mm diameter pipe to cool the stormwater before being discharged into the Rouge River The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site 8485 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $31,25000 shown below in Table 824 below As the cooling trench will be entirely underground, no expansions of the existing pond block are required As such, there are no additional costs associated with land acquisitions Table 824 Pond 55 Cost Estimate Item Construction $25,00000 Engineering Fees $2,50000 Contingency $3,75000 Total $31,25000 Cost Estimate 8486 Conclusions and Recommendations The recommended retrofit to provide additional SWM controls to existing Pond 55 is a cooling trench located within the City owned parkland The cooling trench will provide temperature control of the water discharged into the Rouge River Expansion of the existing SWM pond was not an option due to the presence of mature trees which are to be retained It was determined that adjusting the pond outlet would provide a minimal improvement to erosion control in contrast to the amount of site disturbance that would be required and therefore, improvements to erosion control are not proposed 849 Conceptual Design Summary Pond Background Pond 62 was constructed at the northern limit of the Armadale Community subdivision, located north of Steeles Avenue and east of Markham Road The pond is located at the northern most part of the subdivision, south of Parkview Golf Course and north of Bethany Street The pond discharges to the Rouge River Existing detailed pond design information for Pond 62 was obtained from the City s SWMSoft database Based on the information available in this database it was determined that the Pond is comprised of a large forebay, a main cell and wetland cell Water enters the wetland cell through two (2) outlets from the main cell and then is released into the Rouge River from a single outlet in the wetland cell The data were reviewed to determine the existing performance of the pond and evaluate if the pond meets the current SWM criteria of the TRCA, the MOE, and the City The existing facility provides erosion control in the form of 24-hour detention of the 25 mm storm and quality control through a permanent pool The facility provides adequate quantity and quality controls ES (September 2015) Page 65

75 8492 Criteria The design criteria for the pond retrofit are as follows: Erosion Control (Provide 48-hour extended detention of the 25 mm storm event); and, Temperature Control The downstream receiving watercourse has been identified as possible Redside Dace habitat so the temperature of the released water is a parameter that needs to be controlled 8493 Existing Hydrologic Conditions The existing conditions hydrologic input parameters are summarized below in Table 825 below Table 825 Pond 62 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 2376 TIMP 62% XIMP 62% 8494 Proposed Retrofit Conditions It is proposed that the pond s outlet structure will be modified to provide a longer detention of the 25 mm storm event, that a cooling trench be constructed at the outlet and that additional trees be planted around the pond to provide temperature control Table 826 below summarizes the level of SWM control required and provided for the existing pond and proposed pond retrofit Table 826 Pond 62 Summary of Stormwater Management Control Achieved Parameter Required Provided Existing Facility Provided Proposed Retrofit Extended Detention Release Rate 48 hours 24 hours 48 hours Erosion Control Outflow from the existing pond is controlled by a 13 m wide by 10 m high orifice, the location of which is shown in Figure 62-1 It is proposed that this orifice be replaced with a 10 m wide x 03 m high orifice, which would increase the detention time of the 25 mm storm to 48-hour Temperature Control Although the existing pond has a well-vegetated wetland cell, further modifications could be made to provide more temperature control for the pond Additional plantings along the perimeter of the wetland cell have been proposed One (1) of the twin 2440 x 1525 concrete culverts at the pond s outlet is proposed to be modified to include a cooling trench The cooling trench would provide some additional temperature control prior to discharge The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site ES (September 2015) Page 66

76 8495 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $52,50000 shown below in Table 827 below No expansions of the existing pond block are required As such, there are no additional costs associated with land acquisitions Table 827 Pond 62 Cost Estimate Item Construction $42,00000 Engineering Fees (10%) $4,20000 Contingency (15%) $6,30000 Total $52,50000 Cost Estimate 8496 Conclusions and Recommendations Proposed works involve the modification of the pond outlet, installation of a cooling trench and additional tree plantings around the pond These modifications will increase the pond s detention time of the 25 mm storm to 48-hours and lower the temperature of the water discharged to the Rouge River It should be noted that modifying the outlet of the pond may affect the pond s quantity control performance for the 2- to 100-year storm events During detailed design of the pond retrofit, it is recommended that these effects be investigated to ensure that the proposed outlet modifications do not negatively impact the pond s quantity control performance The detailed design and construction of the Pond 62 outlet retrofit and cooling trench placement should be co-ordinated with the Denison Street and Kirkham Drive extension project, which currently proposes to expand Denison Drive overtop of the existing Pond 62 outlet 8410 Conceptual Design Summary Pond Background Pond 73 was constructed as part of the East Cathedral Community subdivision, located east of Woodbine Avenue and north of Major Mackenzie Drive The pond itself is located in the northern portion of the subdivision, north of Vine Cliff Boulevard and west of Hazelton Avenue The pond discharges to a tributary of the Rouge River Topographical information was obtained from the City Existing detailed pond design information for Pond 73 was obtained from the City s SWMSoft database The primary source of information regarding existing controls in the pond is a report titled SWM Design Brief, Woodbine Mackenzie Developments Limited, East Cathedral Community, dated May 2002 and completed by Stantec Consulting ES (September 2015) Page 67

77 The data was reviewed to determine the existing performance of the pond and evaluate if the pond currently meets existing SWM criteria of the TRCA, the MOE, and the City The existing facility provides sufficient erosion control, quantity, and quality control: Erosion control (94-hour extended detention of the 30 mm storm event); Quantity control (post-to-pre control of peak flows for all storms up to and including the 100-year event); Quality control (sized to provide Level 1 protection (80% TSS removal) in accordance with the MOE SWMP Manual through a permanent pool); and, Temperature (this watercourse has been identified as possible Redside Dace habitat) Criteria The downstream receiving watercourse has been identified as possible Redside Dace habitat so the pond will be retrofit to provide temperature control of the released water Proposed Retrofit Conditions Although the existing pond has a bottom draw for temperature control, it is proposed that the existing pond be retrofit to provide additional temperature control A cooling trench is proposed at the outlet of the existing SWM pond to lower the temperature of water prior to discharge The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site Outflow from the existing pond is controlled by an existing 157 mm orifice; the cooling trench is proposed downstream of the orifice control Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $28,00000 shown below in Table 828 below No expansions of the existing pond block are required As such, there are no additional costs associated with land acquisitions Table 828 Pond 73 Cost Estimate Item Construction $22,40000 Engineering Fees (10%) $2,24000 Contingency (15%) $3,36000 Total $28,00000 Cost Estimate ES (September 2015) Page 68

78 84105 Conclusions and Recommendations Minor retrofits are required for the pond to provide additional temperature control Proposed works involve the installation of a cooling trench and the modification of the existing outlet structure to tie into the cooling trench 8411 Conceptual Design Summary Pond Background Pond 77 was constructed as part of a subdivision south of Major Mackenzie Drive East and west of Kennedy Road The pond is located to the west of Angus Glen Boulevard and to the east of the Angus Glen Golf Course The pond discharges to Bruce River, a tributary of the Rouge River Existing detailed pond design information for Pond 77 was obtained from the City s SWMSoft database These include the following reports and drawings: SWM Pond Design Brief, Angus Glen Village Secondary Plan (OPA 19), Extended Detention / Quantity Pond (Pond A), Cosburn Patterson Mather, May 1996 (Revised June 1996); SWM Pond A Certification and Assumption, Angus Glen Subdivision, City of Markham, Ontario; Drawing No 701 titled Angus Glen Subdivision SWM Facility, July 1996; and, Drawing No 702 titled Pond Section, Angus Glen Subdivision, June 1996 The reports and drawings were reviewed to evaluate the existing performance of the pond and determine if the existing SWM Pond meets the SWM criteria as outlined by TRCA, the MOE, and the City The existing SWM facility provides sufficient quality, quantity, and erosion control The existing sediment forebay and permanent pool provides the required 80% TSS removal The active storage in the pond provides sufficient storage and an orifice plate controls discharge from the pond to Bruce River at pre-development rates for all storm events up to the 100-year storm The orifice also provides 48-hour extended detention of the 25 mm storm event Criteria The downstream receiving watercourse has been identified as Redside Dace habitat so the pond will be retrofit to provide temperature control of the released water ES (September 2015) Page 69

79 84113 Proposed Retrofit Conditions A cooling trench is proposed at the outlet of the existing SWM facility to lower the temperature of the water prior to discharge to Bruce River The cooling trench is an underground structure of buried stone Water is cooled as it passes through the structure as the stones are not exposed to the warming effects of the sun Further assessments are required at the detailed design stage to determine the optimum size of the cooling trench for the site Due to the length of the overflow channel from the pond to the river, a cooling trench up to 60 m can be installed within the existing proposed pond block However; it is unlikely that such a large structure is required for the SWM facility Further assessments are required to determine the optimum size of the cooling trench for the site, at the detailed design stage It is also recommended that additional riparian vegetation be planted around the perimeter of the pond to provide additional shading of the stored water during and after a rain event Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $40,00000 shown below in Table 829 below As the cooling trench will be entirely underground, no expansions of the existing pond block are required As such, there are no additional costs associated with land acquisitions Table 829 Pond 77 Cost Estimate Item Construction $32,00000 Engineering Fees (10%) $3,20000 Contingency (15%) $4,80000 Total $40,00000 Cost Estimate Conclusions and Recommendations As the existing pond provides sufficient quality, quantity, and erosion control, no major retrofits have been proposed for the SWM facility Proposed works involve the installation of a cooling trench downstream of the outlet control structure as a means of temperature control Plantings of additional riparian vegetation have also been proposed for the pond These recommendations are in line with the City s efforts in preserving Redside Dace habitat within the City s watersheds 8412 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled outlet #8 is located immediately north of Highway 7 within a natural creek corridor and outlets to Rouge River The closest major intersection to the uncontrolled area is Highway 7 and Woodbine Avenue ES (September 2015) Page 70

80 84122 Criteria The objective of the conceptual SWM facility design is to provide: Quality Control (80% TSS); and, Temperature Control The downstream receiving watercourse has been identified as Redside Dace habitat so the temperature of the released water is a parameter that should be controlled According to the April 2012 TRCA SWM Criteria, quantity control is not required at this site because the stormwater is being released into the Main Rouge River downstream of Major Mackenzie Drive Erosion control would be beneficial however; there is not enough acceptable land available to construct a facility that would provide a significant amount of storage for erosion control Construction of a facility within the City owned valley lands adjacent to the existing uncontrolled outlet was investigated but construction of a new SWM facility within the valley lands is not supported by the TRCA Existing Hydrologic Conditions The minor drainage area is a mix of parkland and residential land use (comprised of single-family) The outlet discharges at the west bank of the main Rouge River channel, north of Highway 7 The only land appropriately located within the drainage area for construction of a significant SWM facility is limited to a green watercourse corridor that is bounded by the Rouge River, residential properties and Highway 7 The constructible land is further limited due to the presence of mature trees within the watercourse corridor which are to be retained Construction of a facility within the City owned valley lands adjacent to the existing uncontrolled outlet was investigated but construction of a new SWM facility within the valley lands is not supported by the TRCA The existing conditions hydrologic input parameters are summarized in Table 830 below Table 830 UCO 8 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 100 TIMP 47% XIMP 47% ES (September 2015) Page 71

81 84124 Proposed Retrofit Conditions An OGS unit is proposed to provide water quality control prior to discharging to the Rouge River The minor drainage area was used to size the OGS unit Table 831 below summarizes the level of SWM control required and provided by the proposed retrofit Table 831 UCO 8 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 79% Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet A stormceptor STC 14000, or equivalent, is recommended and is sized to remove 79% of TSS for the minor drainage area Temperature Control Detaining water in a SWM pond would have a significant thermal warming effect on stormwater As the stormwater is not proposed to be stored and will not be exposed to the sun for an extended period of time, it is expected that thermal mitigation will not be required Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $486,96000 shown in Table 832 below The proposed pond block is located within the City s lands, therefore; additional land acquisition is not required Table 832 UCO 8 Cost Estimate Item Cost Estimate Construction $162,40000 Engineering Fees (10%) $16,20000 Contingency (15%) $24,40000 Total $203, Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #8 is an OGS This retrofit will enhance the quality control for this retrofit opportunity 8413 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #55 is located immediately south of Park Brook Place within a City owned park and trail system and outlets to the East Branch of the Don River The closest major intersection is Henderson Avenue and John Street ES (September 2015) Page 72

82 84132 Criteria The objective of the conceptual SWM facility design is to provide: Quality Control (80% TSS) Quantity control and erosion control would also be beneficial however; there is not enough acceptable land available to construct a facility that would provide a significant amount of storage for quantity or erosion control Construction of a facility within the City owned parkland adjacent to Henderson Avenue and Forest Park Crescent was investigated but construction of a new SWM facility within the valley lands is not supported by the TRCA The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat so the temperature of the released water is not a targeted parameter Existing Hydrologic Conditions The minor drainage area is comprised entirely of single family residential land use and roadways The major drainage area is a mix of golf course greens and single family residential land use The outlet discharges at the north bank of the east branch of the Don River, upstream of Henderson Avenue The existing conditions hydrologic input parameters are summarized in Table 833 below Table 833 UCO 55 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 477 TIMP 56% XIMP 56% Proposed Retrofit Conditions An OGS unit is proposed to provide water quality control Table 834 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 834 UCO 55 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 81% Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet A Stormceptor STC 9000, or equivalent, is recommended and can remove 81% of TSS for the minor drainage area ES (September 2015) Page 73

83 84135 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $147,20000 shown below in Table 835 below The proposed OGS unit is located within the road right-of-way so land acquisition is not required Table 835 UCO 55 Cost Estimate Item Construction $117,70000 Engineering Fees (10%) $11,80000 Contingency (15%) $17,70000 Total $147,20000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #55 is an OGS within the Park Brook Place road right-of-way This retrofit will enhance the quality control for this retrofit opportunity 8414 Conceptual Design Summary Uncontrolled Outlet #63w Background Uncontrolled Outlet #63w is located immediately south of Proctor Avenue within a City owned park and outlets to the East Branch of the Don River The closest major intersection is Henderson Avenue and Doncaster Avenue Criteria The objectives of the conceptual SWM facility design are to provide: Erosion Control (48 hours of extended detention); and, Water Quality Control (80% TSS removal) The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat so the temperature of the released water is not a targeted parameter Quantity control would also be beneficial however; there is not enough land available to construct a facility that would provide a significant amount of storage for quantity control ES (September 2015) Page 74

84 84143 Existing Hydrologic Conditions The minor drainage area is comprised of commercial and residential land use and roadways The existing conditions hydrologic input parameters are summarized below in Table 836 below Table 836 UCO 63w Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 481 TIMP 62% XIMP 62% Proposed Retrofit Conditions Underground storage chambers are proposed to provide the detention storage required for erosion control An OGS unit is proposed to provide water quality control Table 837 below summarizes the level of SWM control required and achieved by the proposed SWM retrofit Table 837 UCO 63w Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 83% Extended Detention Release Rate 48 hours 51 hours Erosion Control Detention Volume 8,250 m 3 3,645m 3 Erosion Control Underground storage chamber within the park land are proposed to provide storage for erosion control A total of 8,250 m 3 of storage is required to detain the 25 mm rain event for an extended detention of 48-hours The total amount of storage that can be provided is limited by the footprint of available land to build the chamber, as well as the elevation of the receiving watercourse and of the existing storm sewer pipes Given these constraints a total of 3,645 m 3 of storage can be provided based on a StormTech MC-4500 Chamber The following parameters were used in the storage calculations: An MC-4500 Chamber with 0305 m of clear stone below and 0305 m of clear stone above the chamber has an available storage volume of 135 m 3 /m 2 of tank footprint (as per StormTech Product Catalogue, 2011); It was assumed that the water stored below the outlet invert (in the lower 0305 m of clear stone below the chamber) will infiltrate into the ground allowing this portion of the storage facility to be considered active and available storage; and, A total tank footprint of 2,700 m 2 can provide 3,645 m 3 of storage The tank system will have an outlet invert of m, a maximum head elevation of m and the discharge rate will be controlled by a 130 mm diameter orifice plate on the tank outlet structure A volume of 3,645 m 3 will be stored within the tank and released over a period of approximately 51-hours The outlet of the storage tank is limited by the requirements to achieve the extended detention necessary for erosion control Since the underground chamber will not be able to store the full volume of runoff from the 25 mm event, some of the stormwater will be released from the chamber via an overflow, and therefore; will not be detained for an extended period of time ES (September 2015) Page 75

85 Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet The OGS will be located within the Proctor Avenue right-of-way, prior to the proposed underground storage tank to minimize the accumulation of sediment within the storage tank and minimize the potential for the release of harmful substances into the watercourse A CDS model PSW100_80, or equivalent, is recommended and can remove 83% of TSS for the minor drainage area Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $2,679,70000 shown below in Table 838 below The proposed underground chambers are located within the City s lands so land acquisition is not required Item Table 838 UCO 63w Cost Estimate Construction $2,143,70000 Engineering Fees (10%) $214,40000 Contingency (15%) $321,60000 Total $2,679,70000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #63w is a combination of an OGS within the right-of-way and an underground chamber within the City s owned park lands This retrofit will enhance quality control and provide partial erosion control of the 25 mm rain event released over 51-hours Detaining the storm water within an underground chamber rather than a surface detention facility (pond) allows for the land to continue to be used as a public recreational park and protects the detained water from the warming effects of the sun, resulting in cooler water being discharged to the watercourse The construction of the underground storage facility involves the excavation and disposal of approximately 6,600 m 3 of earth The proposed SWM facility will not have an effect on the available floodplain storage along the Don River It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures are applicable for this watercourse The detailed design and construction of the new SWM facility is to include a means of protecting the bank of the Don River during construction and should identify the optimal outfall location to minimize negative impacts Additionally, the implementation of this new SWM facility should be coordinated with the West Thornhill Stormwater Flood Remediation Study which involves increasing the size of some existing storm sewers to provide flood remediation ES (September 2015) Page 76

86 8415 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #66 is located east of Pinevale Road within a natural creek corridor and outlets to the East Branch of the Don River The closest major intersection is Steeles Avenue East and Bayview Avenue Criteria The objective of the conceptual retrofit design is to provide: Water Quality Control (80% TSS removal) The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat therefore reducing the temperature of the released water is not a targeted parameter Although uncontrolled outlet #66 does not currently provide any SWM controls, water quality is the only targeted criteria since there is not adequate space available for a facility that would provide substantial quantity or erosion control Existing Hydrologic Conditions The minor drainage area to the existing uncontrolled outlet #66 is comprised entirely of single family residential land use and roadways The outlet discharges at the south bank of the east branch of the Don River, north and upstream of Henderson Avenue A summary of the existing condition hydrologic input parameter is included below in Table 839 below Table 839 UCO 66 Existing Conditions Hydrological Parameters Parameter 66-Minor Drainage Area Size (ha) 133 TIMP 43% XIMP 43% Proposed Retrofit Conditions An OGS is proposed at each outlet to provide the required water quality control Table 840 below summarizes the level of SWM control required and provided at the uncontrolled outlet Table 840 UCO 66 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 83% ES (September 2015) Page 77

87 Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlets The OGS for uncontrolled outlet #66 will be located at the east end of Pinevale Road, immediately upstream of an existing maintenance hole A CDS model PSWC56_53, or equivalent, is recommended and can remove 83% of TSS for the minor drainage area Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $227,50000 shown in Table 841 below The proposed OGS are located within the City s lands It is assumed that an easement along the storm sewer alignment of uncontrolled outlet #67 already exists, allowing for maintenance of the proposed OGS Table 841 UCO 66 Cost Estimate Item Construction $182,00000 Engineering Fees (10%) $18,20000 Contingency (15%) $27,30000 Total $227,50000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #66 is an OGS within the Pinevale Road right-of-way This retrofit will enhance the quality control for this retrofit opportunity The soil type in this area is conducive to infiltration, therefore it is recommended that any new construction or reconstruction within the area includes infiltration measures Installing infiltration measures such as perforated pipes or bioswales is not a recommended retrofit option because of the high cost and large construction area during installation; however, if they are implemented along side other construction projects these factors are reduced The implementation of this new SWM facility should be coordinated with the West Thornhill Stormwater Flood Remediation Study which involves increasing the size of some existing storm sewers to provide flood remediation 8416 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet Site #94 consists of two (2) separate uncontrolled outlets within the Village in the Valley neighbourhood in Markham Uncontrolled outlet 94w takes drainage from the west, including stormwater discharged by Pond 65 and Pond 66 The outlet discharges to Font Hill Creek on the northwest corner of Toogood Park Uncontrolled outlet 94e takes drainage from the south, discharging to Font Hill Creek on the northeast corner of the park Font Hill Creek flows east and joins Bruce Creek, a tributary of the Rouge River ES (September 2015) Page 78

88 The subdivision was constructed in the 1980s The SWM Report titled Master Drainage Plan: PD1-3 Area in Unionville outlined that quantity control was to be provided for the subdivision through the use of dry ponds on parks within the neighbourhood The report, however; also specified that erosion and quality control would not be necessary As such, existing SWM controls in the area do not meet current TRCA standards and have been proposed to be retrofitted SWM information for Facilities #65 and #66 were obtained from the City s SWMSoft database These include the following reports: Revised Detailed Analysis of the Drainage Systems for Village in the Valley, Phase 10, Unionville, Andrew Brodie Associates Inc, August 1986; and, Master Drainage Plan, PD1-3 Area in Unionville, Andrew Brodie Associates Inc, January 1980 The reports were used to evaluate existing drainage patterns and levels of control Storm sewer information for the area was obtained from the City s SWMSoft Database Criteria The objectives of the conceptual SWM facility design are to provide: Erosion Control (48 hours of extended detention); Water Quality Control (80% TSS removal); and; Temperature mitigation The downstream receiving watercourse has been identified as potential habitat for Redside Dace so the temperature of the released water is a targeted parameter Existing Hydrologic Conditions Pond 66 provides storage for minor system flows (up to the 5-year storm) in a superpipe located underneath the park within John XXIII Catholic School The peak flow from the superpipe for the 5-year storm is 255 m 3 /s As previously mentioned, no erosion, temperature, or quality control are provided in the area The minor drainage area to the existing uncontrolled outlet #94w is comprised of roadways, single family residential and institutional land use The minor drainage area to the existing uncontrolled outlet #94e is comprised of roadways and single family residential land use A summary of the existing condition hydrologic input parameter is included below in Table 839 below Table 842 UCO 94 Existing Conditions Hydrological Parameters Parameter 94w-Minor Drainage Area 94e-Minor Drainage Area Size (ha) TIMP 43% 43% XIMP 43% 43% ES (September 2015) Page 79

89 84164 Proposed Retrofit Conditions Due to the large size of the catchment draining to Outlet 94w (approx 932 ha), a very large SWM facility will be required to provide sufficient storage to meet the erosion control requirement for the subdivision As the existing area has been fully built out, there exists an opportunity to construct an underground SWM facility beneath the existing Toogood Park An existing walkway bisects the park in two (2) with the northern portion of the park containing an existing playground and tennis court, while the southern portion is primarily open space After consultation with City s staff, it was determined that it is in the best interest of the City to construct the proposed underground SWM facility only on the south portion of the park Runoff will enter the SWM facility from two (2) different directions Flows currently discharging out from outlet 94w will be spilt via a flow splitter in a proposed maintenance hole such that a portion of the flow is discharged to Font Hill Creek and the remainder is redirected to the storage tank under the park The flow splitter is necessary to maintain baseflow to Font Hill Creek An OGS unit will be installed upstream of the flow splitter so that all runoff from the west will be treated The system from the east has existing pipes underneath the park, leading to outlet 94e Existing pipe sections from the southern portion of the park will be removed to accommodate for the proposed underground storage chambers The underground chambers will connect back to the existing system at the northern portion of the park and discharge to the creek through the existing outlet 94e Table 843 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 843 UCO 94 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 80% to 84% Extended Detention Release Rate 48 hours 48 hours Erosion Control Detention Volume 12,100 m 3 3,300m 3 Quality Control Stormwater will be pre-treated with OGS units prior to entering underground storage chambers One (1) OGS unit, a CDS model PMSU40_45 (or equivalent), will be required to treat runoff from the south and east that are currently discharging to outlet 94e, and will provide the required 80% TSS removal One (1) OGS unit, a CDS model PSW100_100 (or equivalent), will be required to treat runoff from the west that is currently discharging to outlet 94w, and will provide 84% TSS removal ES (September 2015) Page 80

90 Erosion Control The storage required to provide full extended detention of the 25 mm storm is approximately 12,100 m 3 The underground storage chambers will provide approximately 3,300 m 3 of storage, meaning the proposed system will only provide about a quarter of the required storage However; due to the space restrictions, providing some erosion control brings improvement to the uncontrolled outlets An orifice plate (150 mm) will be placed downstream of the facility to control the release rate for the required 48-hour drawdown time Temperature Control The underground storage will also provide temperature control as the underground chambers and granular fill will be cooler than outside temperatures in the summer Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $21 million shown below in Table 844 below As the SWM facility will be entirely underground, no expansions of the existing park are required As such, there are no additional costs associated with land acquisitions Table 844 UCO 94 Cost Estimate Item Construction $1,679,00000 Engineering Fees (10%) $167,90000 Contingency (15%) $251,90000 Total $2,098,80000 Cost Estimate Conclusions and Recommendations Proposed works involve the installation of an underground SWM facility under the existing Toogood Park The proposed facility will provide quality, erosion, and temperature control not provided by existing infrastructure A significant portion ($109 million) of the cost is related to the installation of the underground storage chamber Another significant portion of the total cost ($056 million) is related to the installation of OGS units to provide sufficient quality control for the watercourse Some modifications of the existing storm sewers will also be required Infiltration opportunities utilizing the underground storage tanks should be investigated at detailed design Additionally LIDs within the treatment train approach, such as rain gardens, infiltration trenches, ect, should be investigated at the detailed design stage ES (September 2015) Page 81

91 8417 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #103 is located just north of the pedestrian bridge within the City s owned Park at the north-east corner of Main Street Unionville and Carlton Road within City The closest major intersection is 16 th Avenue and Warden Avenue Uncontrolled outlet #103 outlets to Bruce Creek of the Rouge River Watershed The downstream receiving watercourse has been identified as possible Redside Dace habitat, as advised by MNR, so the temperature of the released storm water is a targeted parameter Criteria The objectives of the conceptual SWM facility design are to provide: Water Quality Control (80% TSS removal); and, Temperature Mitigation Erosion control would also be beneficial however; there is not enough land available, due to densely planted trees, to construct a facility that would provide adequate storage for erosion control Existing Conditions The minor drainage area is comprised of institutional and single-family residential land use The outlet discharges at the north-east bank of Bruce Creek, downstream of main street Unionville The existing conditions hydrologic input parameters are summarized below in Table 845 below Table 845 UCO 103 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 4664 TIMP 44% XIMP 44% Proposed Retrofit Conditions An OGS unit is proposed to provide water quality control The minor drainage area was used to size an OGS Table 846 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 846 UCO 103 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 80% ES (September 2015) Page 82

92 Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet It is proposed to install the OGS within the road right-of-way of Main Street Unionville as the remainder of the storm sewer is surrounded by dense tree cover A CDS model PSW100_60, or equivalent, is recommended and can remove 80% of TSS for the minor drainage area Temperature Control Detaining water in a SWM pond will have a significant thermal warming effect on stormwater As the stormwater is not proposed to be stored and will not be exposed to the sun for an extended period of time, it is expected that thermal mitigation will not be required Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $533,75000 shown below in Table 847 below The proposed OGS is to be located within the City s lands so land acquisition is not required Table 847 UCO 103 Cost Estimate Item Construction $ 427,00000 Engineering Fees $ 42,70000 Contingency (15%) $ 64,05000 Total $ 533,75000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #103 is an OGS within City owned Main Street Unionville road right-of-way This retrofit will enhance the quality control for this retrofit opportunity 8418 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet Site #106 is located in the Unionville Estates neighbourhood of Markham The outlet discharges to Berczy Creek, located upstream of Toogood Pond The outlet takes drainage from the south and the west, an area totalling approximately 22 ha consisting mainly of single family housing There are no existing SWM facilities or controls for the outlet ES (September 2015) Page 83

93 84182 Criteria The design criteria for the pond retrofit are as follows: Quality (Provide 80% TSS removal as per MOE guidelines) According to the April 2012 TRCA SWM Criteria, quantity control is not required at this site because the stormwater is being released into the Berczy Creek downstream of Warden Avenue Erosion control would also be beneficial however there is not enough land available, without tree loss, to construct a facility that would provide adequate storage for erosion control Existing Hydrologic Conditions The contributing drainage area is 2376 ha in size, with an average imperviousness of 62%, based on City standards The existing conditions hydrologic input parameters are summarized in Table 848 below Table 848 UCO 106 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 2376 TIMP 62% XIMP 62% Proposed Retrofit Conditions The installation of an OGS unit has been proposed to provide the required controls for this site The minor drainage area was used to size an OGS Table 849 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 849 UCO 106 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 82% Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet It is proposed to install the OGS in the location of an existing storm maintenance hole, underneath the park pathway to treat the entire minor drainage area as the remainder of the storm sewer is surrounded by dense tree cover A CDS model PSWC56_78, or equivalent, is recommended and can remove 82% of TSS for the minor drainage area Temperature Control Detaining water in a SWM pond will have a significant thermal warming effect on stormwater As the stormwater is not proposed to be stored and will not be exposed to the sun for an extended period of time, it is expected that thermal mitigation will not be required ES (September 2015) Page 84

94 84185 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $262,50000 shown in below Table 850 below As the proposed works are located entirely in public lands, there are no additional costs associated with land acquisitions Table 850 UCO 106 Cost Estimate Item Construction $210,00000 Engineering Fees (10%) $21,00000 Contingency (15%) $31,50000 Total $262,50000 Cost Estimate Conclusions and Recommendations Proposed works involves the installation of an OGS unit to enhance quality control The OGS unit will be located within City parkland, in the location of an existing storm maintenance hole underneath the park pathway 8419 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #112 is located immediately south of 16 th Avenue, approximately 150 m east of Village Parkway within City s parkland and outlets to Berczy Creek of the Rouge River Watershed The closest major intersection is 16 th Avenue and Warden Avenue The downstream receiving watercourse has been identified as Redside Dace habitat, as advised by MNR, so the temperature of the released storm water will be a targeted parameter Criteria The objectives of the conceptual SWM facility design are to provide: Water Quality Control (80% TSS removal); and, Temperature Mitigation Erosion control would also be beneficial however; there is not enough land available, due to densely planted trees, to construct a facility that would provide adequate storage for erosion control ES (September 2015) Page 85

95 84193 Existing Conditions The minor drainage area is comprised entirely of paved roadway The outlet discharges at the south-west bank of Berczy Creek, immediately downstream of 16 th Avenue The existing conditions hydrologic input parameters are summarized below in Table 851 below Table 851 UCO 112 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Size (ha) 169 TIMP 100% (entire drainage area is paved road) XIMP 100% (entire drainage area is paved road) Proposed Retrofit Conditions An OGS unit is proposed to provide water quality control The minor drainage area was used to size the OGS Table 852 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 852 UCO 112 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 81% Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet The OGS will be located within the 16 th Avenue right-of-way A Stormceptor STC 6000, or equivalent, is recommended and can remove 81% of TSS for the minor drainage area Temperature Control Detaining water in a pond has a significant thermal warming effect on stormwater As the stormwater is not proposed to be stored and will not be exposed to the sun for an extended period of time, it is expected that thermal mitigation will not be required Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $120,70000 shown below in Table 853 below The proposed OGS is to be located within the City s lands so land acquisition is not required Table 853 UCO 112 Cost Estimate Item Construction $ 96,55000 Engineering Fees (10%) $ 9,65000 Contingency (15%) $ 14,50000 Total $ 120,70000 Cost Estimate ES (September 2015) Page 86

96 84196 Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #112 is an OGS within the 16 th Avenue right-of-way This retrofit will enhance the quality control for this retrofit opportunity The proposed OGS will not have an effect on the available floodplain storage along Berczy Creek Note that at the implementation stage coordination with York Region will be required as the OGS is proposed to be located in within the right-of-way of a Regional Road (16 th Avenue) 8420 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #162 is located south of James Walker Court within a natural creek corridor and outlets to the Lower Rouge River of the Rouge River watershed The closest major intersection to uncontrolled outlet is Highway 7 and Main Street Markham Criteria The objective of the conceptual SWM facility design is to provide: Erosion Control (48 hours of extended detention); Water Quality Control (80% TSS removal); and, Temperature Control The downstream receiving watercourse has been identified as Redside Dace habitat, as advised by MNR, so the temperature of the released water is a targeted parameter Quantity control would also be beneficial however; there is not enough land available to construct a facility that would provide a significant amount of storage for quantity control Existing Hydrologic Conditions The minor drainage area to the existing uncontrolled outlet #162 is comprised entirely of single family residential land use and roadways The major drainage area that drains towards the location of the uncontrolled outlet #162 is a mix of single family residential land use, roadways, commercial and industrial land use The outlet discharges along the north bank of Rouge River, immediately east (and downstream) of Main Street Markham Due to accessibility concerns, the land available for construction of a SWM facility is limited to the existing area adjacent to James Walker Court that does not have dense tree cover The existing conditions hydrologic input parameters are summarized in Table 854 below Table 854 UCO 162 Existing Conditions Hydrological Parameters Parameter 162-Minor Drainage Area 162-Major Drainage Area Size (ha) TIMP 68% 70% XIMP 68% 70% ES (September 2015) Page 87

97 84204 Proposed Retrofit Conditions An underground storage facility is proposed to provide the detention storage required for erosion control and an OGS is proposed to provide water quality control Table 855 below summarizes the level of SWM control required and provided by the proposed SWM retrofit Table 855 UCO 162 Summary of Stormwater Management Control Achieved Parameter Required Provided Level of Quality Control Enhanced Enhanced Extended Detention Time 48 hours 24 hours Erosion Control Detention Volume 377 m m 3 Erosion Control Underground storage chambers within the TRCA land adjacent to James Walker Court are proposed to provide storage for the extended detention of the 25 mm rain event A total of 377 m 3 of storage is required to detain the 25 mm rain event The underground storage facility depth is limited by the existing storm sewer infrastructure, therefore the outlet of the storage facility must have an invert of m to tie into the existing storm sewer A total of 378 m³ of storage can be provided based on a StormTech SC-740 Chamber with a footprint of 565 m The following parameters were used in the storage calculations: An SC-740 Chamber with 015 m of clear stone below and 015 m of clear stone above the chamber has an available storage volume of 067 m³/m² of tank footprint (as per StormTech Product Catalogue, 2011); It was assumed that the water stored below the outlet invert (in the lower 015 m of clear stone below the chamber) will infiltrate into the ground allowing this portion of the storage facility to be considered active and available storage; and, A total tank footprint of 565 m² can provide 378 m³ of storage The tank system will have an outlet invert of m, a maximum head of 091 m and the discharge rate will be controlled by a 75 mm diameter orifice plate A volume of 378 m³ will be stored within the tank and released over a period of approximately 24-hours Since an orifice of 75 mm in diameter is the smallest allowable size, an extended detention of 24-hours is the maximum drawdown time achievable Quality Control An OGS is proposed to provide water quality treatment prior to discharging the proposed dry pond The OGS will be located at the end of the cul-de-sac on James Walker Court A Stormceptor STC 5000, or equivalent, is recommended and will provide 80% TSS removal of the minor drainage area Temperature Control Detaining water in a SWM pond would have a significant thermal warming effect on stormwater As the stormwater is not proposed to be stored and will not be exposed to the sun for an extended period of time, it is expected that thermal mitigation will not be required Additionally, the underground storage will also provide temperature control as the underground chambers and granular fill will be cooler than outside temperatures in the summer ES (September 2015) Page 88

98 84205 Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $332,70000 shown below in Table 856 below The proposed underground storage SWM facility is located within TRCA lands The costs associated with this agreement are not included in the cost estimate as they are variable dependent upon City negotiations with the TRCA It is assumed that the City currently has an easement over the existing storm sewer that is within TRCA lands Table 856 UCO 162 Cost Estimate Item Construction $266,20000 Engineering Fees $26,60000 Contingency (15%) $39,90000 Total $332,70000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #162 is a combination of an OGS located at the south end of James Walker Court and an underground storage chamber within TRCA owned lands adjacent to the south end of James Walker Court A permanent easement within the TRCA lands will be required Land, habitat improvements or other forms of compensation may be part of negotiations with the TRCA This retrofit will enhance quality control and will provide erosion control of the 25 mm rain event released over 24-hours Detaining the storm water within an underground chamber rather than a surface detention facility (pond) protects the detained water from the warming effects of the sun, resulting in cooler water being discharged to the watercourse The construction of the underground storage facility involves the excavation and disposal of approximately 600 m 3 of earth The proposed SWM facility will not have an effect on the available floodplain storage along the Rouge River It is recommended that an erosion study of the adjacent watercourse be undertaken to confirm the appropriate erosion control measures are applicable for this watercourse Additionally consultation with MNR should be undertaken to screen for species at risk or of concern and to provide species-specific SWM control guidelines related to endangered species or species at risk ES (September 2015) Page 89

99 8421 Conceptual Design Summary Uncontrolled Outlet # Background Uncontrolled Outlet #176 is located immediately south-east of Green Lane within a natural creek corridor (which is identified in the GIS information provided by the City as City s owned parkland) and outlets to Markham Creek of the Don River Watershed There are no marked trails or recreation infrastructure within this parkland The closest major intersection is Leslie Street and Green Lane The downstream receiving watercourse has been identified as unlikely to be Redside Dace habitat, as advised by MNR, so the temperature of the released storm water is not a targeted parameter Criteria The objectives of the conceptual SWM facility design are to provide: Water Quality Control (80% TSS removal) Quantity control is required in this section of the Don River Watershed, as per TRCA SWM Criteria (August 2012) However; there is not enough land available to provide storage for the major storm events due to the presence of mature trees Erosion control would be beneficial however; there is not enough acceptable land available to construct a facility that would provide a significant amount of storage for erosion control Construction of a facility within the City owned valley lands adjacent to the existing uncontrolled outlet was investigated but construction of a new SWM facility within the valley lands is not supported by the TRCA Existing Conditions The minor and major drainage area is comprised entirely of single family residential land use and roadways The outlet discharges at the south-west bank of Markham Creek, immediately downstream of Green Lane The existing conditions hydrologic input parameters are summarized below in Table 857 Table 857 UCO 176 Existing Conditions Hydrological Parameters Parameter Minor Drainage Area Major Drainage Area Size (ha) TIMP 43% 43% XIMP 43% 43% ES (September 2015) Page 90

100 84214 Proposed Retrofit Conditions An OGS unit is proposed to provide water quality control The minor drainage area was used to size the OGS Below in Table 858 below summarizes the level of SWM control required and provided by the proposed SWM controls Table 858 UCO 176 Summary of Stormwater Management Control Achieved Parameter Required Provided TSS Removal 80% 81% Quality Control An OGS is proposed to provide water quality treatment of the water discharged by the storm sewer outlet The OGS will be located within the Green Lane right-of way, prior to discharge into the Don River A CDS model PSWC56_53_10, or equivalent, is recommended and can remove 81% of TSS for the minor drainage area Cost Estimate and Land Availability The total estimated cost of this retrofit is approximately $227,50000 shown below in Table 859 The proposed SWM facility is located within the City s lands so land acquisition is not required Table 859 UCO 176 Cost Estimate Item Construction $182,00000 Engineering Fees (10%) $18,20000 Contingency (15%) $27,30000 Total $227,50000 Cost Estimate Conclusions and Recommendations The recommended retrofit to provide SWM to uncontrolled outlet #176 is an OGS within the Green Lane right-of-way This retrofit will enhance the quality control for this retrofit opportunity ES (September 2015) Page 91

101 90 Public and Agency Consultation 91 Public Consultation Activities through the EA Process The general public, residents, property owners, agencies, etc, were given a variety of opportunities throughout the project for learning, sharing, and responding by means of the following points of public contact The Municipal Class EA requires the Proponent to undertake two (2) mandatory points of public contact during Phase 2 (Alternative Solutions) for a Schedule B project The Project Team has exceeded the mandatory number of public contacts, with the following opportunities for comment provided: Notice of Commencement; Notice of PIC #1; PIC #1; Notice of PIC #2; PIC #2; and, Notice of Completion Public comments were welcome throughout the EA process Any public comments received are included in Appendix H 911 Notice of Commencement The Notice of Commencement was prepared and distributed to stakeholders and review agencies and issued on September 20, 2012 In addition, the notice was posted on the City s website and published in the local newspaper The Markham Economist & Sun on September 20, 2012 The purpose of the notice was to inform the public and stakeholders that a Class EA study had been initiated in the City The notice provides background information including the purpose, objectives and process It also notifies the public about the consultation process consisting of two (2) PICs Furthermore, the contact information for the City s main project contact and Cole Engineering s Project Manager were made available to the public to engage any initial feedback on the project A copy of the Notice of Commencement is provided in Appendix I 912 Notice of Public Information Centre #1 Notice of the first PIC was mailed directly to residents and stakeholders on the mailing list on February 11, 2013 The notice was also accessible to the general public via posting on the City s website and publication in the local newspaper The Markham Economist & Sun on February 14 and 21, 2013 The notice provided a project description, description of work completed to date, information regarding the PIC, and a request for comments and input Contact information for City s main project contact and Cole Engineering s Project Manager was also provided to encourage the submission of comments A copy of the Notice of PIC #1 is provided in Appendix J ES (September 2015) Page 92

102 913 Public Information Centre #1 Two (2) PICs took place during the project The first PIC was held on March 5, 2013 It was attended by 10 people mostly consisting of City residents and one City councillor The Project Team including representatives from Cole Engineering and the City were in attendance to answer any questions that participants had The PIC presented the following elements: Study overview and background; Overview of the Municipal Class EA Process; Problem / opportunity statement; Screening of existing SWM facilities and outlets to identify opportunities for improvement; Prioritization of opportunities for SWM improvements; Alternative solutions being considered; Evaluation of alternative solutions; Identification of the preferred solutions; and, Next steps The display panels presented at the PIC can be found in Appendix K The PIC sign-in sheet and comment forms can be found in Appendix H It is noted that multiple comments were received after the PIC as a result of the PIC All received comments and responses are provided in Appendix H 914 Notice of Public Information Centre #2 Notice of the second PIC was mailed directly to residents and stakeholders on the mailing list on November 19, 2013 The notice was also accessible to the general public via posting on the City s website and publication in the local newspaper The Markham Economist & Sun on November 21 and 28, 2013 The notice provided a project description, description of work completed to date including a summary of what was presented at the first PIC, information regarding the second PIC, and a request for comments and input Contact information for City s main project contact and Cole Engineering s Project Manager was also provided to encourage the submission of comments A copy of the Notice of PIC #2 is provided in Appendix J ES (September 2015) Page 93

103 915 Public Information Centre #2 The second PIC was held on December 4, 2013 It was attended by six (6) people consisting of City residents The Project Team including representatives from Cole Engineering and the City were in attendance to answer any questions that participants had The PIC presented the following elements: Study background and problem / opportunity statement; Summary of the study progress since the first PIC; Location of the top priority sites; Summary of the evaluation of retrofit and new SWM facility alternatives and the identification of the preferred alternative(s); Design concepts for SWM facility retrofits and for new SWM facility construction; and, Next steps The display panels presented at the PIC can be found in Appendix K The PIC sign-in sheet can be found in Appendix H It is noted that no comments were received 916 Notice of Completion The Notice of Completion informs stakeholders of the completion of the Class EA and provides the locations where stakeholders can review the completed The notice also informs the public of the 30 day review period associated with the conclusion of the EA process During this review period, concerned individuals have the right to raise and discuss issues prior to requesting a Part II Order before the project may proceed to implementation A copy of the Notice of Completion is provided in Appendix L 92 First Nations Consultation A letter and Notice of Commencement was sent to the Chief of the Mississaugas of the New Credit First Nations on December 17, 2012 A response from the Mississaugas of the New Credit First Nations was not received ES (September 2015) Page 94

104 93 Consultation with the TRCA and MOE Multiple stakeholder meetings were held throughout the project, at key milestone in the project completion A representative from both the TRCA and the MOE was present at all of the stakeholder meetings Meeting minutes from the stakeholder meetings are provided in Appendix M Also all notices were mailed directly to representatives at the TRCA and MOE On June 3, 2013 the project team consulted the TRCA for preliminary feedback regarding the high-level concepts for the retrofit designs, prior to proceeding with a more in-depth design of the retrofit concepts On October 6, 2013 the Project Team submitted the completed retrofit concept designs including details such as figures, calculations and report discussion regarding the designs Following the TRCA s review of the submitted designs, City and TRCA staff performed site visits of each of the submitted sites and the TRCA later submitted written comments regarding the proposed design at each site A consultation meeting was held with TRCA staff and the project team on November 5, 2013 to discuss the design concepts for the top priority sites in detail The meeting discussion focused on key sites where the design would be significantly impacted based on the TRCA s written comments A copy of the TRCA s comments, the Project Team s responses to the comments and the meeting minutes are provided in Appendix M 94 Consultation with the Ministry of Natural Resources All notices were mailed directly to a representative at the MNR On December 5, 2012 a request for Species at Risk pre-screening was submitted to MNR The Project Team worked with the MNR to receive information regarding potential impacts to Redside Dace, which was vital to the screening and prioritization of retrofit opportunity sites, while protecting sensitive information about Redside Dace locations ES (September 2015) Page 95

105 100 Implementation of the Project 101 Confirm EA Schedule Once the preferred solution was confirmed for each of the top 21 retrofit sites, the choice of a Schedule B EA process was reviewed The results of this review are provided in below Table 101 below Either a Schedule A, A + or B applies to each of the 21 proposed retrofits or new SWM facilities, therefore; the Schedule B process followed in this study has satisfied the EA requirements for each of the individual retrofit / new construction projects and these projects may proceed to the implementation phase Table 101 Municipal Class Environmental Assessment Schedule Site ID EA Schedule A A+ B C P P P P P P P P P P P UCO UCO UCO-63w UCO UCO UCO UCO UCO UCO UCO Notice of Completion The last step of the Schedule B Class EA process following documentation of Phases 1 and 2 involves issuing a Notice of Completion to review agencies and the public and providing the for review for a period of 30 calendar days Following the end of the review period for the, if there are no outstanding Part II Order Requests, the City may proceed to Phase 5 of the Class EA process to complete the contract drawings and tender documents This undertaking requires a number of permits to be acquired before construction can begin, as described in Section 1031 In order to satisfy the notification requirements, a Notice of Completion will be mailed to each of the previously contacted individuals in the project mailing list who wished to be further involved in the project The notice will inform stakeholders and the general public of the project s completion, including the preferred solution and their rights regarding the Part II Order provisions ES (September 2015) Page 96

106 103 Steps to Implementation Prior to the construction of any of the proposed SWM facility retrofits or new SWM facilities there are several steps to implementation of this project: Funding availability to be determined by the City Council; Additional studies undertaken, where applicable; Preparation of detailed design and contract drawings; Obtain the required permits; and, Property acquisitions and/or agreements to allow works on private property, where applicable 1031 Funding Mechanisms The City currently funds stormwater management capital projects and operations and maintenance through various sources Below is a list of the potential funding sources for stormwater retrofits for the City: Development charges; Tax base (lifecycle reserve fund); Cash-in-lieu from development or redevelopment areas; Cost sharing with developers in cases where there is developable land within the drainage area of the retrofit or new SWM facility; Stormwater fees; SWM user fees charged to new development or re-development; The TRCA partnership; The Regional Municipality of York partnership; The Federation of Canadian Municipalities Green Municipal Fund this fund provides grants to develop plans and conduct feasibility studies as well as below-market loans in combination with grants to support the implementation of capital projects; Provincial Funding Programs: As published in the MNR s Redside Dace Recovery Strategy (February 2010), the Province of Ontario intends to support actions focusing on the protection and restoration of Redside Dace habitat and populations; Ministry of the Environment Great Lakes Guardian Community Fund; and, Ministry of the Environment Ontario Community Environment Fund Federal funding programs: Infrastructure Canada Gas Tax Fund this fund provides long-term predictable funding to municipalities for building and revitalizing public infrastructure that will create positive environmental results; Infrastructure Canada Green Infrastructure Fund this fund supports projects that promote cleaner air, reduced greenhouse gas emissions and cleaner water; and, Infrastructure Canada Building Canada Fund this fund supports projects related to public infrastructure projects owned by Provincial, territorial and Municipal governments aimed to create a cleaner environment, and strong and prosperous communities ES (September 2015) Page 97

107 Retrofits may be funded by different sources and in combination with other works depending on the benefits associated with integrated design, approvals and implementation Water quality retrofits may be integrated with other projects such as flood control upgrades, or other capital works such as road widenings For example, OGSs can be substituted for new manholes in projects involving storm sewer upgrades Flood control upgrades are currently funded by the stormwater fee and federal gas tax grants Water quality retrofits such as existing pond outlet modifications and plantings can be integrated with planned operation and maintenance activities Pond operation and maintenance activities are currently funded by the taxes base (lifecycle) Several retrofits provide erosion prevention benefits through the addition of extended detention storage Erosion prevention can defer or lessen the extent of downstream erosion repairs in watercourses where runoff from existing development is uncontrolled In the report to Development Services Committee on March 28, 2010 (report dated March 21, 2010) entitled Funding of Stormwater Management Retrofit Projects, it was noted that The remediation of erosion in watercourses can be achieved through a combination of controlling stormwater discharge from ponds and direct in-stream works Currently in-stream erosion repair works are funded 65% by development charges and 35% by the tax base (lifecycle) Considering integration with other projects and funding sources, possible funding sources for the implementation of SWM retrofits include: i) tax base (life cycle reserve fund) - where retrofits such as outlet modifications and plantings can be integrated with existing operation and maintenance activities; ii) development charges - where retrofits provide an erosion control function, or may offset residual impacts of upstream development that cannot be mitigated on-site; and, iii) stormwater fees - where typically water quality retrofits can be integrated with storm sewer upgrades City staff should confirm the applicability of development charges funding for erosion control projects, and integrate funding for other retrofits, where applicable, as part of ongoing operation and maintenance and flood control activities ES (September 2015) Page 98

108 1032 Additional Studies If, during implementation, new infrastructure is proposed within the valley or retrofit works will significantly impact natural heritage features, several detailed studies will be requested by the TRCA to further evaluate the environmental impacts to the valley, prior to issuing a permit The TRCA is to provide a list of the necessary studies if the City wants to pursue this option The detailed design phase for many of the pond retrofits and a number of the new SWM facilities will require a number of studies, which may include: Detailed vegetation survey and assessment; Geotechnical investigation; Utility locates; An erosion study of the watercourse receiving discharge from the top priority sites (where erosion control measures / improvements are proposed) should be undertaken to confirm the appropriate erosion control measures for the watercourse; and, A study to establish the appropriate limit of the Pond #51 SWM facility expansion in relation to the 25-year erosion hazard limit 1033 Detailed Design This Class EA determined that the proposed SWM facility retrofits or new SWM facility construction is feasible, as described in Section 84 However, a detailed design of the new SWM facility or retrofit at each of the sites is necessary before construction can proceed Unique site-specific implementation considerations have been provided in Section 84 There is a number of implementation and detailed design considerations that apply to a majority of the sites, which includes, but is not limited to: All of the sites will require at least a Stage 1 Archaeological Assessment and/or a heritage impact assessment (refer to Appendix E for completed screening check sheets); Detailed topographic survey; Detailed vegetation survey; The implementation of Low Impact Development (LID) measures should be considered at the detailed design stage (please refer to the Low Impact Development Stormwater Management Planning and Design Guide) LIDs can be implemented in addition to the recommended stormwater measures proposed to utilize a treatment train approach to maximize the desired stormwater management targets MNR provided a very basic level of screening to identify sites which may be associated with Redside Dace habitat only Site-specific species at risk screening under the Endangered Species Act, 2007, must be undertaken once the site has proceeded to implementation; Environmental Impact Study; All sites that are identified by MNR to have the potential to affect Redside Dace habitat should include stringent erosion and sediment control measures in the construction design Strict inspection and enforcement of erosion and sedimentation control measures should be taken during construction as sedimentation during construction has a significant negative impact on Redside Dace habitat; ES (September 2015) Page 99

109 All underground storage facilities within park land and sports fields should incorporate a means for the City to use the stored water for irrigation purposes, wherever feasible Additionally, infiltration of the stored water should be considered This will be contingent on the existing groundwater elevation and soil types present at the site; Construction erosion and sediment controls; The location of existing underground utilities and infrastructure The location of OGS units or other new infrastructure within the road right-of-way is contingent on the location of existing underground services; Planting and restoration work must be planted as per the TRCA Post-Construction Restoration Guidelines and the TRCA SWM Pond Planting Guidelines, as applicable; and, The detailed design should avoid the removal of trees wherever reasonable and should not include the removal of mature trees The layout of infrastructure should be based on a detailed tree survey Construction detailing and phasing of the Pond 24 retrofit should consider avoiding any negative impacts to the slope adjacent to the proposed OGS location The existing outlet channel of Pond 51 is lined with gabions Replacement of the gabions with a more suitable alternative should be considered, contingent on budgeting constraints and the condition and remaining life span of the existing gabion lining The detailed design and construction of the Pond 62 outlet retrofit and cooling trench placement should be coordinated with the Denison Street and Kirkham Drive Extension Project, which currently proposes to expand Denison Drive overtop of the existing Pond 62 outlet The detailed design and construction of the new SWM facility at Uncontrolled Outlet #63w is to include a means of protecting the bank of the Don River during construction and should identify the optimal outfall location to minimize negative impacts The detailed design and construction of the new SWM facility at Uncontrolled Outlets #63w and #66 should be coordinated with the West Thornhill Stormwater Flood Remediation Study which involves increasing the size of some existing storm sewers to provide flood remediation ES (September 2015) Page 100

110 1034 Permits and Approvals The proposed construction may require permits from several agencies including the TRCA, the MNR and the MOE as summarized below in Table 102 below Table 102 Summary of Potential Required Permits Agency Approval Mechanism Notes TRCA Permit under OReg 166/06 Regulation is under S 28 of the Conservation Authorities Act Department of Fisheries and Oceans Authorization under the federal Fisheries Act The TRCA is a partner in this Class EA and has been consulted throughout the entire process Permit application will be made during the detailed design process As a result of amendments to the Fisheries Act dated November 25, 2013, partnership agreements between the TRCA and DFO are no longer in effect Proponents must ensure projects meet DFO requirements utilizing a selfassessment process It is not anticipated that Harmful Alteration, Disruption or Destruction of fish habitat is to occur during implementation of the proposed retrofits However, if this was the case an authorization from the DFO would be required It is anticipated that the cool water fisheries window will apply, which means that in water works can only occur between June 15 and September 15 However, the timing window may differ between sites (for example if Redside Dace are present) MNR Endangered Species Act, 2007 It is anticipated that an approval or letter of advice under the Endangered Species Act will be required for a number of the sites since the preliminary screening provided by MNR has identified that a number of the sites have the potential to impact the habitat of the endangered species Redside Dace MOE Environmental Compliance Approval / Certificate of Approval Amendment An amendment to the existing Certificate of Approval (C of A) will be required for retrofitted SWM facilities that have a C of A An Environmental Compliance Approval (ECA) will be required for all newly constructed SWM facilities ES (September 2015) Page 101

111 1035 Property Acquisitions and/or Agreements Property or easement acquisition and/or land use / access agreements will be needed prior to construction of a number of the new SWM facilities or SWM facilities retrofits Some of the conceptual designs depend on placing infrastructure within lands not currently owned by the City This includes the construction of a new underground storage facility within TRCA owned land at uncontrolled outlet #162 and the construction of an underground storage facility within School owned lands as part of the retrofit of Pond #39 Where construction of the retrofit will impact Regional Roads, or where a facility will be located within the right-of-way of a Regional Road, co-ordination with York Region will be required This applies to uncontrolled outlet # Summary of Potential Effects and Mitigation Measures Effects on Built and Cultural Heritage Landscapes or Archaeological Resources All of the sites will require at least a Stage 1 Archaeological Assessment and/or a heritage impact assessment prior to implementation to ensure that built and cultural heritage landscapes or archaeological resources are not impacted Utilities and Servicing To avoid impacting existing utilities and underground services, locates must be obtained prior to construction Locates should also be obtained during the detailed design of the retrofit / SWM facility so that the design can be modified as necessary to avoid impacting utilities or other underground services Some designs require modification to or tying into existing storm sewers Storm sewer locations, size, material and elevations should be verified during the detailed design phase to avoid construction delays Site Clearing and Preparation Clearing of vegetation, including brush and potentially trees, will be required at some sites for the construction of the retrofit or new SWM facility Detailed vegetation surveys are to be taken to identify trees and significant vegetation that should be protected during construction The retrofit / SWM facility design should be modified as necessary to avoid the removal of trees Protected vegetation should be clearly marked during construction Construction staging areas should be strategically located to reduce hazards and disruption to the public during construction, to reduce the risk of pollutants or sediment entering watercourses or sewers and to reduce impacting existing infrastructure or natural heritage features Effects on Adjacent Land Uses Adjacent land uses may be impacted by noise during construction This can be mitigated through an appropriate construction management plan, including restrictions on construction hours Staging areas are to be located such that there are no impacts on adjacent land uses wherever feasible Where needed, easements, land use agreements or the purchase of private property, will be obtained prior to construction The proposed retrofits / new SWM facilities will not have a long term negative impact on the usability of adjacent land ES (September 2015) Page 102

112 Effect on Public Safety SWM facilities can cause a drowning risk to any members of the public that enter a SWM facility The detailed design of any new above ground SWM facilities or retrofit of above ground SWM facilities should include the appropriate safety features to reduce hazards and risk to the public This can include fences, signage and other means of deterring the public from entering a SWM facility Construction of the SWM facilities can create hazards to public including open pits during excavation and moving construction equipment These hazards can be mitigated through signage, fencing off construction areas from the public and choosing access routes which will minimize the exposure of public to construction activities Effects on Traffic Flow Construction works within the right-of-way, the storage of equipment or materials within the right of way and site access off of roadways all have the potential to negatively impact traffic flow Appropriate traffic controls will be required to mitigate traffic impacts Traffic controls are to be developed during the detailed design of the retrofit / new SWM facility Erosion and Siltation Appropriate erosion and sedimentation controls will be needed during construction and are to be developed during the detailed design of the retrofit / new SWM facility All sites that are identified by MNR to have the potential to affect Redside Dace habitat should include stringent erosion and sediment control measures Stringent inspection and enforcement of erosion and sedimentation control measures should be taken during construction as sedimentation during construction has a significant negative impact on Redside Dace habitat Effects on Fish and Wildlife Appropriate isolation measures and dewatering techniques should be used wherever work is be done in or near a watercourse or wet pond to ensure that fish are not harmed or otherwise negatively impacted during construction The area disturbed during construction should be minimized to minimize impacting terrestrial habitat Effects on the Receiving Watercourse Construction or modification of outlets adjacent to a watercourse will cause some level of disturbance to the watercourse bank and adjacent bed Appropriate erosion and sedimentation controls must be implemented during construction to ensure that the watercourse downstream of the site is not impacted The area of disturbance during construction should be minimized as much as feasible and should be restored immediately once construction near the watercourse is completed Effects on Groundwater Negative effects on groundwater are not anticipated Underground storage chambers may be designed to provide a means for water to infiltrate into the ground, providing groundwater recharge Restoration Site restoration is to be to City and TRCA standards or better Planting and restoration work must be planted as per the TRCA Post-Construction Restoration Guidelines and the TRCA SWM Pond Planting Guidelines, as applicable ES (September 2015) Page 103

113 105 Prioritization of the Implementation of Retrofits and New SWM Facility Construction The implementation of the SWM retrofit or new SWM facility construction at the 21 priority sites has been prioritized based on the criteria shown in Table 103 below and ranked to provide a recommended order in which the retrofits should be implemented Each criterion was assigned a weighting based on the importance of the criterion A score between zero (0) and one (1) was then assigned to each criterion for a particular site, based on the specific site conditions and details of the retrofit / new SWM facility design The final prioritization score of each site is a sum of the scores assigned to each criterion multiplied by the weighting of that criterion Final prioritization scores are out of 100, with a score of 100 being the highest priority and a score of zero (0) being the lowest priority It is recommended that retrofits of existing SWM ponds be completed at the same time as scheduled maintenance of the pond This will provide a cost savings to the City as the pond will only have to be dewatered once and restoration work will only be needed once Therefore, after the prioritization scoring was completed, the order of implementation ( ranking ) was determined primarily based on the anticipated date of other works at the site, for example pond maintenance or other infrastructure projects, and secondarily based on the prioritization score All sites where other works are anticipated to be occurring within the next 10 years were assigned top ranking This includes sites P-5, P-47, P-62, uncontrolled outlet #63w and uncontrolled outlet #66 These top sites where then ranked based on the date of the anticipated sites The remaining sites (where no other works are anticipated, or where other works are anticipated to occur more than 10 years in the future) where given lower rankings, based on their total implementation prioritization score A brief description of each criterion is provided in Section 1051 and a summary of the prioritization results and recommended implementation order is provided in Section 1052 A detailed description of the reasoning behind the prioritization score assigned is provided in Appendix N Table 103 Implementation Prioritization Criteria Criterion Category Criterion (score) Weighting out of 100 Economic Consideration Capital Cost 40 Size of Treated Drainage Area 15 Number of SWM Objectives SWM and Environmental Benefit Achieved 15 Unique Benefit (SWM, Environmental, Social, etc) 10 Social Impacts Ease of Implementation 20 ES (September 2015) Page 104

114 1051 Description of Prioritization Criteria Capital Cost New SWM facilities or retrofits that have a higher estimated capital cost were assigned a lower prioritization score to reduce the priority of the site, allowing the City s limited capital works budget to be applied to more projects Size of Treated Drainage Area A new SWM facility or retrofit that will treat / control a larger drainage area was assigned a higher prioritization score to increase the priority of the site This will focus the City s implementation efforts on projects that will benefit the greatest volume of water Number of Stormwater Management Objectives Achieved A new SWM facility or retrofit that will provide multiple types of SWM controls (flood, erosion, water quality and/or temperature control) was assigned a higher prioritization score to increase the priority of the site This will focus the City s implementation efforts on projects that will provide more SWM benefits Unique Benefits A new SWM facility or retrofit that meets the needs of unique and/or site needs that have been identified for a site was assigned a higher prioritization score to increase the priority of the site This will focus the City s implementation efforts on projects that will provide benefits to unique and specific needs that have been identified for that site Ease of Implementation The ease of implementation considers whether additional studies, land acquisitions or easements will be required prior to the detailed design and/or construction of the new SWM facility or retrofit, all of which make implementation more challenging Additionally, if co-ordination with other projects that have an overlapping subject area, or other groups that use the subject land (for example sports leagues in parks) will be needed then the implementation is more challenging Sites with the most challenging implementation were assigned a lower prioritization score to reduce the priority of the site This will focus the City s implementation efforts on projects that can more quickly be implemented and will require fewer resources to implement ES (September 2015) Page 105

115 1052 Prioritization Results and Final Ranking A summary of the prioritization results and recommended implementation order (ranking) is provided in Table 104 below Table 104 Implementation Ranking Site ID Total Prioritization Score (out of 100) Ranking P P UCO UCO-63w 34 4 P P P UCO P UCO P P UCO UCO UCO P UCO UCO UCO P P ES (September 2015) Page 106

116 110 References Toronto and Region Conservation Authority (1999) Town of Markham Stormwater Retrofit Study Ministry of the Environment (2003) SWM Planning and Design Manual Toronto and Region Conservation Authority (2012) SWM Criteria Version 10 ES (September 2015) Page 107

117 Evaluated Sites Legend Stormwater Management Facilities Stoufville Creek Uncontrolled Outlets River 84 Creek 83 Major Road 73 City Boundary Bruce Creek Robinson 140 Creek Mount Joy Creek Mills German Creek Rouge River Don River (East Branch) 63W 63E Little Rouge Creek Eckardt Creek Markham Creek Pomona Creek 8 Beaver Creek Markham SWM Facility Retrofit Study Municipal Class EA November 2013 Morningside Creek Evaluated Sites n/a SCALE MAP 1,800 Meters 4-1

118 Priority Sites Legend Priority Uncontrolled Outlets Uncontrolled Minor Drainage Area Elgin Mills Rd E Woodbin e Ave Hwy 404 Uncontrolled Major Drainage Area Priority Stormwater Management Facilities Stormwater Facilities Minor Drainage Area Little Rouge Creek Stormwater Facilities Major Drainage Area Creek d Major Mackenzie Dr E River Mccowa nr Warden A ve Kennedy Rd P-73 City Boundary Hwy 48 P-77 Major Road P-5 UCO-106 P-38 Bruce Creek P-39 UCO-103 Eckardt Creek Robinson Creek Hwy 7 E UCO-8 Main St S Beaver Creek UCO-94 Main St N 16th Ave UCO-112 Mount Joy Creek Hwy 407 German Mills Creek UCO-176 P-45 P-47 14th Ave P-24 Markham Rd Don River (East Branch) P-51 P-62 P-55 Markham SWM Facility Retrofit Study Municipal Class EA November 2013 Priority Sites UCO-63w UCO-66 Steeles Ave E Don Mills Rd Rouge River Markham Creek UCO-55 UCO-162 9th Line Pomona Creek Leslie St Bayview A ve Yonge S t Morningside Creek SCALE 800 1,600 Meters MAP 7-1