Chapter A - Introduction - City of Pickering

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Comments in white are satisfied. Comments in orange background are not satisfied or are new comments. Comments in blue background can be addressed at the NFSSR stage. Comments in yellow are deferred due to need for hydrology model. APPENDIX A. TRCA COMMENTS ON SEATON MESPA DECEMBER 2011; MESPA TEAM RESPONSE FEBRUARY 2013 # Section # Page # in PDF TRCA Comment Action Required that this change in the flow regime will result in severe erosion of the creek during larger rain events, and thus, cannot support the removal of quantity controls on Whitevale Creek. 33. 5.5.1.2 145 It is unclear what assumptions have been made in See Appendix B, Peer Review Comments related the Regional storm analysis. For example, was to the surface hydrologic analysis, specifically AMC III conditions used in the assessment, were comments 4-6 for further details. aerial reduction factors used, etc? All parameters should be documented and discussed. 34. 5.5.1.2 145 There should be no increase in flood risk resulting from the development of Seaton. Further hydrologic and hydraulic modeling is required to demonstrate this. 35. 5.5.1.2 146 The use of natural valley storage in the flood modeling is not supported as it represents a significant deviation from the provincial approach to flood plain management. It would result in a wholesale change from floodplain management to flood storage management, and places the liability to maintain the flood storage infrastructure onto the owner (i.e. the local municipality, the region and/or the province). Our reasons are as follows: The need for Regional controls will need to be reassessed to ensure no off site impacts, once the watershed hydrology model has been updated to the satisfaction of TRCA. If off site impacts are unavoidable, then a detailed hydraulic assessment of impacts may be necessary. Further guidance from the MNR will required if this is the case. Revise to eliminate the use of “natural valley storage.” Under review. Consulting Team’s Response April 27, 2011 Update to regional storm control assessment being completed as per discussions with agencies on April 5, 2011. Comments noted and are under review as part of the regional storm control assessment. Continue to disagree, until we have the results of modelling. Action Taken MESPA December 2011 The Regional Storm Analysis is discussed in Section B5.10. Discussions with agencies have been on-going regarding modelling approach and alternative potential management scenarios, and updated existing conditions model results. These discussions are ongoing and will continue over the next few months. TRCA Comment on MESPA To be reviewed when new hydrological assessment has been completed. See response to comment #33, above. To be reviewed when new hydrological assessment has been completed. See response to comment #33, above. To be reviewed when new hydrological assessment has been completed. Team Response February 2013 No response required – 2012 Duffins Creek Hydrology Update supersedes 2011 MESPA. No response required – 2012 Duffins Creek Hydrology Update supersedes 2011 MESPA. No response required – 2012 Duffins Creek Hydrology Update supersedes 2011 MESPA. • The proposal would result in a fundamental change to how the TRCA regulates hazard lands, specifically a change from flood plain management to flood storage management, which is currently not applied at any location within our jurisdiction. • The proposal limits the ability for the TRCA, municipality, and region to make improvements to the valley corridor within any proposed reservoir (i.e. no change to the upstream valley which impacts flood storage, such as crossing modifications or reforestation). • It places management of the liability onto the municipalities. • Additional analysis will be required to determine downstream hazard limits resulting from a dam break (which the structures would be considered), and this may increase the extent of existing flood hazard lands within the City of Pickering and the Town of Ajax, increasing the TRCA Regulated Area, and introducing strict policy limitations on development and requirements for flood proofing where development is permitted. • The de-regulating of flows (routing) does not adhere to MNR guidelines. Our past experience with MNR regarding the issue have shown an unwillingness to allow routing flows through structures as it is not PAGE 9 February 2013
Comments in white are satisfied. Comments in orange background are not satisfied or are new comments. Comments in blue background can be addressed at the NFSSR stage. Comments in yellow are deferred due to need for hydrology model. APPENDIX A. TRCA COMMENTS ON SEATON MESPA DECEMBER 2011; MESPA TEAM RESPONSE FEBRUARY 2013 # Section # Page # in PDF TRCA Comment Action Required an appropriate approach to flood plain management. 36. 5.5.1.2 146 The study limit for the flood plain maps completed as part of the Existing Conditions Report does not cover the entire area slated for development. The flood plain mapping exercise should be extended to cover areas where there is no mapping to confirm the limits of development and ensure the proposed SWMFs are located outside of the flood hazard limit and buffer. We are concerned that the current plan calls for a number of SWMFs located within or within close proximity to the Regional flood plain. 37. 5.5.1.2 146 This section suggests that flood lines can be increased as long as they are contained within the NHS. The requirement in the Terms of Reference is to ensure no impacts to the Seaton NHS and downstream as it relates to flooding. The Province as the owner of the NHS needs to be aware of and accept any potential impacts. 38. 6.2 152 The proposed buffers from the SWMF and associated grading to natural features are not provided, eg.10m from woodlands, etc. per the policies in the City’s Conformity Amendment. 39. 6.2 152 The SWMF locations and outfalls will need to be reviewed in the field to ensure the locations are appropriate. Some of the proposed SWMFs may not have an appropriately safe and secure outfall given side slopes and location of the SWMF. 40. 6.2 152 Encroachment of SWMFs into NHS corridors should be restricted to no more than 25% of the functional corridor width. Complete a comprehensive flood study that includes areas where previous flood plain mapping was not completed. Please see Appendix B, Peer Review Comments related to the surface hydrologic analysis, specifically comments 6 for further details. Revise to state that an increase in flooding within the NHS must be assessed for impacts to natural features and functions and appropriately mitigated. Confirm that these buffers have been reflected in the matrices. This should take place as soon as possible. Site visit days should be set up well in advance. Revise the SWMF design and location to accommodate this criterion. Consulting Team’s Response April 27, 2011 Acknowledged. A separate study is being prepared to update the 2006 Seaton floodplain mapping study. Potential for increases in the NHS is being assessed as part of the regional storm control analysis. If increases are identified, increases to natural features and functions will be assessed. The buffers applied were as discussed in Section 6.2. Floodline and meander belt buffers to be added to the discussion. Acknowledged. Site visits are being undertaken, some of which will be undertaken after the MESPA is completed. This criterion impacts only a few SWMFs. Each location is under review to determine whether the 50% intrusion can be reduced. Action Taken MESPA December 2011 As discussed in Section B5.10.2, updates to the floodplain mapping completed in 2006 have been made to extend hydraulic models and floodline mapping upstream along stream reaches in Seaton. See response to comment #33, above. MESPA reflects the additional buffers and policies of the City’s Conformity Amendment (Section B6.2 and SWMF matrices). This is an NFSSR requirement. Where site visits have been completed, appropriate changes to matrices are made in the MESPA. SWM matrices are revised to address the outcome of assessment at each location. TRCA Comment on MESPA A detailed review of the geometric components of the floodplain mapping has been provided in our letter of October 19, 2012. There appears to be sections missing from the study. Not yet addressed. Comment #33 suggests no resolution has been made with the agencies yet. The flood impact analysis is subject to the revisions associated with the hydrology update. However, the current analysis involves a local increase in both flows and water levels in Whitevale Creek, which the TRCA cannot accept based on the information provided. TRCA does not agree with the arguments put forth that this is acceptable (See New Comment, above, related to Section 5.9.3.4). The proponent will have to establish that no impacts to the Seaton NHS and downstream will occur due to any changes in hydrology. If the proponent can show that these increases are acceptable to all stakeholders (Province, TRCA and City of Pickering), TRCA would expect that a figure be created outlining any changes in water levels and/or depths of greater than 0.1m within the entire study area in order to delineate all changes in the floodplain (any other possible impacts) before agreeing that no flood risk exists through a local increase. TRCA needs all of the information available to understand and accept any changes to water levels and flood depths before assessing impacts at the site level. Noted. Noted. See detailed comments on individual SWMF locations below. Duffin Heights was a completely different case and was based on a very old MESP, and the pond restricting half of the width of the corridor was a best-efforts scenario. This was largely Team Response February 2013 The comments have been reviewed and will be addressed as part of the Floodplain Mapping Update, Seaton Lands (March 2013). The Whitevale Assessment has been updated based on the 2012 Duffins Creek Hydrology Update. Refer to Section B5.3. The hydraulic model has been included as Appendix B5-C. This model provides the flood elevations for all storms for all scenarios. The Table provided in Appendix B5-C provides the change in elevation resulting from no controls on Whitevale Creek. The changes in flood elevation that are greater than 0.3m have been highlighted in red. Please note that the flows utilized in this analysis are from the 2012 Duffins Creek Hydrology Update. As such the flows are higher because the model does not include the ponds located north of Highway 407 which will have quantity controls. So it can be assumed that north of Highway 407 there will not be any changes in flood elevation. Additionally, the model does not include the proposed culvert improvements at Whitevale Road that will reduce the flood level increases. The changes in flood elevation for the 2 through 100 year storm events, spatially are very difficult to distinguish on a figure or drawing. It was felt that the analysis of the actual flood elevations and changes in flood elevation are more useful for this analysis. As such the 2-100 year flood elevations were not mapped. The reference to Duffin Heights has been removed. The few instances where the 25% target has not been met are further discussed in Chapter B6.3. Recognizing PAGE 10 February 2013
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CHAPTER A - INTRODUCTION 1.0 STUDY
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of alternatives for the arterial an
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These MESP study requirements were
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ownership of the Province. Lands ou
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Within the MESP Study Area, Ganatse
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hydrology for erosion and flood con
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It is important to note that the ME
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projects are considered pre-approve
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Table A9.2 provides a summary of th
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the Environment for Part II Order r
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• Takes into account externally p
Page 23 and 24: YORK DURHAM LINE SIDELINE 32 NORTH
Page 25 and 26: COMMENT MESPA RESPONSE (December 20
Page 33 and 34: Area Parks over 4 hectares Parks 4
Page 41 and 42: COMMENT It is noted that the first
Page 43 and 44: COMMENT dispersed in terms of date.
Page 45 and 46: COMMENT Staff agrees with this reco
Page 47 and 48: species.” COMMENT GHD should furt
Page 49 and 50: COMMENT RESPONSE REPORT CHAPTER AND
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Page 55 and 56: COMMENT 4. Section 4.0 - Phase 2 Re
Page 57 and 58: COMMENT • Section 3.0, last sente
Page 59 and 60: COMMENT Reg”, should be removed.
Page 61 and 62: RESPONSE TO CITY COMMENTS SWMF LOCA
Page 67 and 68: Comments in white are satisfied. Co
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Chapter A - Introduction - City of Pickering

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