Project Management, Environmental Assessment, Stormwater Management. Hydrologic Modelling. Natural Heritage. Fluvial Geomorphology

Transcription

1 Welcome PUBLIC INFORMATION CENTRE # 1 KROSNO CREEK DIVERSION PROJECT February 19, :30 p.m. to 8:30 p.m. Please sign in on the sheet provided. Then feel free to walk around and view the displays. The purpose of this Public Information Centre (PIC) is to introduce you to this project, inform you of our progress to date, and obtain your comments on the project. The major elements presented today are: Study Overview Existing Conditions Alternative Solutions Preliminary Preferred Solution Next Steps The Study Team is interested in receiving any comments that you may have about the Study. Mr. Tom Dole, P.Eng. Water Resources Engineer City of Pickering One The Esplanade Pickering, ON L1V 6K7 Tel: (905) Ext: tdole@pickering.ca Mr. Steve Hollingworth, M.A.Sc., P.Eng. Consultant Project Manager TMIG The Municipal Infrastructure Group Ltd Dufferin Street, Suite 200 Vaughan, ON L4K 0C5 Tel: (905) Ext shollingworth@tmig.ca If you have any questions, our representatives will be pleased to discuss the project with you. Should you have any questions, comments, require further information or wish to be added to the study mailing list, please contact either Steve or Tom. Study Team: Project Management, Environmental Assessment, Stormwater Management Hydrologic Modelling Natural Heritage Fluvial Geomorphology Utility Coordination Archeology TMIG The Municipal Infrastructure Group Ltd 8800 Dufferin Street, Suite 200 Vaughan ON CA L4K 0C5 t f Computational Hydraulics International 147 Wyndham St. N., Suite 202 Guelph ON CA N1H 4E9 t f Savanta Inc 37 Bellevue Terrace St. Catharines ON CA L2S 1P4 t f GHD 6705 Millcreek Dr., Unit 1 Mississauga ON CA L5N 5M4 t f T2 Utility Engineers 1615 Dundas St. E. 4 th Floor Lang Tower Whitby ON CA L1N 2L1 t Archeoworks Yonge St. Unit 1029 Newmarket ON CA L3X 1X4 t f

2 Study Overview The study area covers the entire Krosno Creek Watershed and a portion of the Pine Creek watershed. Both systems eventually empty into Frenchman s Bay Krosno Creek was replaced by storm sewer systems through development in the watershed north of Highway 401, and is confined to a narrow concrete channel for a considerable distance south of Highway 401 In its current form, Krosno Creek cannot convey all of the flow from severe storms. Many properties have been impacted by flooding in the past, particularly during a severe storm in August There continue to be risks for flooding and erosion along Krosno Creek The 2009 Frenchman s Bay Stormwater Management Master Plan (FBSWMMP) recommended a diversion of flow to Pine Creek to reduce the risk of flooding along Krosno Creek were impacted from flooding The Krosno Creek Diversion Project was initiated by the City of Pickering to examine the causes of flooding in more detail, and to determine the most appropriate means of reducing the risk of flooding from Krosno Creek. 2

3 EA Process Municipal Class Environmental Assessment The City of Pickering retained The Municipal Infrastructure Group Ltd. to complete this Study in accordance with the Municipal Class Environmental Assessment process. The Study is being conducted as a Schedule C Project, encompassing Phases 1 through Phase 4 as outlined in the Municipal Engineers Association Municipal Class Environmental Assessment document (October 2000, as amended in 2007 and 2011). We are here 3

4 Existing Natural Features Fish habitat and vegetation cover are generally poor along Krosno Creek west of Sandy Beach Road The perched culvert outlet at Alyssum Street may be a barrier to fish Several protected Species at Risk can potentially be found in the Hydro Marsh, near the outlet to Frenchman s Bay A number of warmwater fish species can be found in the lower reaches of Krosno Creek 4

5 Existing Level of Service: Flooding New computer models were created, calibrated and used to predict the flow and depth and extent of flooding along Krosno Creek for a range of severe storm events. This area is the subject of a more detailed flood study prepared for the proposed development of the Downtown South lands The existing small culverts under Highway 401 and the railway and the considerable flood storage available on the south parking lot at the Pickering Town Centre significantly reduce the peak flow rates in the downstream open sections of Krosno Creek. Storm Event Buildings Impacted Estimated Flood Damages* 2 4 $130, $493, $1,685, $1,685, $1,866, $1,932,700 NOTE: The extent of flooding shown above is distinct from the Toronto and Region Conservation Authority s (TRCA) Regulatory Flood Plain. The TRCA Regulatory Flood Plain adheres to MNR Guidelines which stipulate a number of conservative assumptions regarding the effect of existing structures that can reduce flow rates in the system (SWM ponds, restrictive culverts, etc.). For more information on the TRCA s Regulatory Flood Plain, contact Chris Jones at (416) ext or cjones@trca.on.ca Average Annual Estimated Damages $390,931 *Damages Estimated as 10% of the MPAC assessed value of all properties where buildings are partially or entirely within the flood plain 5

6 Alternative Solutions Channel Improvements Description The existing undersized culverts under Highway 401 and the railway tracks restrict flow, significantly reducing peak flow rates in Krosno Creek downstream of the railway. If these culverts were replaced with much larger structures in the future, peak flow rates in Krosno Creek could increase. This alternative involves the construction of a naturalized channel corridor that could contain the peak flow in Krosno Creek if the restrictions caused by the existing Highway 401 and railway culverts were eliminated The channel would have a top width of at least 26 m. Construction of the channel would require expropriation and demolition of all of the residential properties on one side of the existing concrete lined channel Existing culverts at road crossings would need to be replaced with large bridges Benefits Flood risk would be eliminated, even if the Highway 401 and/or railway culverts were enlarged in the future A wide, naturalized channel corridor would significantly improve aquatic and terrestrial habitat Trails and other public amenities could be incorporated into the reconstructed valley corridor Costs Property acquisition Channel construction and landscaping Large bridges at Bayly Street, Morden Lane, Reytan Boulevard and Alyssum Street TOTAL COST: $24.4 Million Drawbacks Large social impact associated with the expropriation and demolition of up to 46 homes required for the channel corridor Very large and challenging construction program, many utilities (gas, communications, hydro, etc) would need to be relocated for bridges Very high capital cost Average Annual Flood Damages Existing: $390,000 Future: $ 0 6

7 Alternative Solutions Enhanced SWM Controls Pickering City Centre Description Planning is underway for significant redevelopment and intensification in the Pickering City Centre area The planned redevelopment presents an opportunity to incorporate modern, effective stormwater management controls on public and private property Recommended stormwater management criteria (from a separate study supporting the City Centre Plan) include: Enhanced Water Quality Control (80% TSS Removal) Retention of the first 5 mm of rainfall on-site Control post-development peak flow rates to predevelopment levels Sites assumed to be up to a maximum of 50% impervious for calculating pre-development flow rate The full build-out of the Pickering City Centre, with the recommended stormwater management criteria, was simulated in the computer model created for Krosno Creek Benefits Improvements to the health of Krosno Creek, as modern stormwater management practices will also improve water quality and reduce erosion Limited costs to the City, as the majority of the stormwater controls will be implemented in private developments Drawbacks The predicted reductions in flow rates and flooding will not be realized until full build-out of the City Centre Plan, which may a considerable amount of time There will only be a small reduction in flows and flooding for very large storm events Costs Most of the costs will be borne by private developers Limited costs to the City to incorporate Low Impact Development practices into road reconstruction and other public infrastructure projects, where feasible TOTAL COST: Negligible Average Annual Flood Damages Existing: $390,000 Future: $240,000 7

8 Alternative Solutions Culvert Improvements Description The existing culverts along Krosno Creek are bottlenecks in the system and contribute significantly to the current flooding problems The existing culverts at Morden Lane, Reytan Boulevard and Alyssum Street are corrugated steel pipe-arch structures, each approximately 3 m wide and 2 m high These three culverts could potentially be replaced with twin 3 m wide concrete box culverts Alyssum Street Culvert Benefits The existing culverts can be replaced relatively quickly and easily The existing culverts are reaching the end of their service life and will require replacement in the near future regardless The culvert replacements will reduce flooding and flood damages for even the most severe storm events Drawbacks Water quality and erosion in Krosno Creek will not be improved Costs Replacing the culverts at Morden Lane, Reytan Boulevard and Alyssum Street with twin 3 m wide x 1.8 m high concrete box culverts Average Annual Flood Damages Existing: $390,000 Future: $ 46,000 TOTAL COST: $1.4 Million 8

9 Alternative Solutions Diversion to Pine Creek Description The diversion of flows from Krosno Creek to Pine Creek was recommended in the Frenchman s Bay Stormwater Management Master Plan When combined with culvert improvements at Morden Lane, Reytan Boulevard and Alyssum Street, no buildings would be impacted from flooding from Krosno Creek for even the most severe storm events A number of additional improvements would be needed to mitigate the potential flooding impacts on Pine Creek Pickering Parkway Pine Creek Benefits Flood risk from Krosno Creek would be eliminated, even if the Highway 401 or railway culverts are enlarged in the future Reduced erosion in Krosno Creek and reduced pollutant loadings to the Hydro Marsh at the outlet of Krosno Creek Drawbacks Very large and challenging construction program, many utilities (gas, communications, hydro, etc.) would need to be relocated Potential impacts to flooding and erosion in Pine Creek Very high capital cost Costs Diversion Sewer (Twin 2.4 m diameter pipes) from Krosno Creek to Pine Creek, tunnelled under Liverpool Road and the Highway 401 Ramp Replacement of the Pine Creek culverts under Highway 401 and Radom Street and the Krosno Creek culverts at Morden Lane, Reytan Boulevard and Alyssum Street TOTAL COST: $30.4 Million Average Annual Flood Damages Existing: $390,000 Future: $ 0 9

10 Alternative Solutions Krosno Blvd Relief Sewer Description The existing culverts along Krosno Creek at Morden Lane, Reytan Boulevard and Alyssum Street are bottlenecks in the system and contribute significantly to the current flooding problems The relief sewer on Krosno Boulevard would divert a portion of the flow in Krosno Creek away from these culverts and return the flow to Krosno Creek downstream of Alyssum Street A 3 m wide x 1.5 m high concrete box sewer could be installed along Morden Lane, Krosno Boulevard and Alyssum Street Krosno Boulevard at Morden Lane Benefits Significant reductions in flooding and flood damages, particularly for the small to moderate storms considered Costs 3 m wide x 1.5 m high concrete box sewer from Morden Lane to downstream of Alyssum Street Drawbacks Potential conflicts with numerous connections from houses to the watermains and sanitary sewers adjacent the relief sewer Limited reductions in flooding and flood damages for the most severe storm events considered Water quality and erosion in Krosno Creek will not be improved Average Annual Flood Damages Existing: $390,000 Future: $ 32,000 TOTAL COST: $5.8 Million 10

11 Alternative Solutions Flood Proofing Flood Proofing Rather than reducing flow rates or flood levels in Krosno Creek, this alternative involves retrofitting flood prone buildings to prevent water from entering the building Flood proofing measures could include re-grading or berming to prevent water from reaching buildings, or installing water-tight doors and windows on buildings likely to be exposed to flood water. Buildings Currently at Risk of Flooding Benefits Flood proofing can prevent flood damages from future severe storm events Costs Approximately $10,000 per flood prone property, on average TOTAL COST: $660,000 to protect all 66 flood prone buildings Drawbacks Difficulties in ensuring all flood prone buildings are appropriately flood proofed Challenges to ensure the flood proofing is maintained and remains effective following future home renovations No reductions in flooding, no improvements in water quality and erosion in Krosno Creek Average Annual Flood Damages Existing: $390,000 Future: $ 0 11

12 Alternative Do Nothing Natural Environment Social/Cultural Environment Technical Environment Overall Impacts Benefits Impacts Benefits Challenges Performance Cumulative Impact Cumulative Benefit No impacts, as no works are proposed Continued erosion and impaired water quality in Krosno Creek No impacts, as no works are proposed No benefits, as no works are proposed No challenges, as no works are proposed No reduction in the frequency and severity of flooding NOT RECOMMENDED Does not reduce flooding, other alternatives exist with acceptable impacts Creek Improvements to Convey the Regulatory Flow Impacts to existing channel Replacement of the concrete Approximately 45 homes will Creation of new, natural and riparian vegetation during lined channel with a natural need to be purchased/ public open space, could construction channel and wide, vegetated expropriated and demolished incorporate a trail system in valley corridor to create channel corridor reconstructed valley corridor Will be challenging to secure property for channel, significant construction effort to create channel, construct bridges and relocate utilities Flooding will be contained in corridor, no flood damages even if 401/CNR culverts enlarged NOT RECOMMENDED Significant costs to implement, challenges to secure property and significant impacts to owners of 45 homes to be purchased and demolished for construction of the channel Enhanced SWM Negligible impacts, as works will be located in existing developed sites and road right-of-ways Potential improvements in water quality and erosion in Krosno Creek Negligible additional impacts anticipated during redevelopment and infrastructure replacement Promotion of low-impact and sustainable development practices Will be incorporated into new developments, but will take a long time for widespread implementation Small reduction in the severity of flooding downstream of Bayly Street for large storm events RECOMMENDED Not recommended as a stand-alone solution to address flooding, but recommended to enhance water quality and erosion in Krosno Creek Culvert Improvements Limited, temporary impacts to Krosno Creek during construction Fish passage enhanced through replacement of perched culvert at Alyssum Street Short term impacts during construction No benefits anticipated Standard construction Significant reduction in the practices, will need to bypass frequency and severity of flow around the work areas flooding, will be considered in Regulation mapping RECOMMENDED Cost effective solution, few environmental impacts, will be recognized by the TRCA in future flood plain mapping updates Complete Diversion to Pine Creek with Krosno Creek Culvert Improvements Impacts to open space north of Highway 401 for storage creation, increased erosion in Pine Creek, limited, temporary impacts to Krosno Creek during construction Potential improvements in water quality and erosion in Krosno Creek Short term impacts during construction, potential impacts to archaeological resources 1 Could incorporate a public trail system in the Pine Creek valley Requires tunnelling under Liverpool Road, significant challenges to mitigate impacts on flooding in Pine Creek (i.e. Highway 401 Culvert replacement) No flood damages in Krosno Creek, even if 401/CNR culverts enlarged NOT RECOMMENDED Significant costs and potential impacts to Pine Creek Krosno Boulevard Relief Sewer Limited impacts to Krosno Creek at the inlet and outlet locations Continued erosion and impaired water quality in Krosno Creek Short term impacts during construction, easements may be required for inlet, outlet No benefits anticipated Potential conflicts with sanitary service connections, susceptible to freezing Significant reduction in the frequency and severity of flooding NOT RECOMMENDED Significant reduction in flooding with few environmental impacts, but not as cost effective as Culvert Improvements Flood Proofing No impacts, as all works will be within existing residential lots Continued erosion and impaired water quality in Krosno Creek Requires homeowners to install and maintain flood proof doors and windows No benefits anticipated Significant challenges to implement and maintain flood proofing retrofits to private homes Flood damages should be prevented, but flood levels in Krosno Creek will not be reduced NOT RECOMMENDED Frequency and severity of flooding is not reduced, difficulties in implementing and ensuring long term effectiveness of flood proofing measures Least Impact / Greatest Benefit Greatest Impact / Least Benefit 1 A Stage 2 Archaeological Assessment would be needed to confirm the presence or absence of archaeological resources in the area east of Pine Creek 12 Evaluation of Alternatives Financial Environment No direct costs Average annual flood damages: $390 Thousand The Do Nothing option is always investigated in the Environmental Assessment Process, in the event that all other alternatives result in unacceptable impacts In this case, doing nothing would mean allowing flooding to continue, and acknowledging and accepting the risk and the potential damages to flood prone buildings and infrastructure during future severe storms. $24.4 Million Average annual flood damages: $0 Minimal additional direct costs to the City for infrastructure renewal projects Average annual flood damages: $240 Thousand Recommended for future development to further reduce flood risk $1.4 Million Average annual flood damages: $46 Thousand Preliminary Preferred Alternative $30.4 Million Average annual flood damages: $0 $5.8 Million Average annual flood damages: : $32 Thousand $660 Thousand Average annual flood damages: $0

13 Preliminary Preferred Alternative Culvert Improvements Replace the existing corrugated steel pipe-arch culverts at Morden Lane, Reytan Boulevard and Alyssum Street with twin 3 m wide x 1.8 m high concrete box culverts The combined effect of the preliminary preferred alternative is a reduction in average estimated flood damages from $390,000 per year to $46,000 per year, to be achieved with a capital cost of approximately $1.4 Million The planned re-development in the Pickering City Centre area, with the recommended stormwater management controls, will further reduce flooding in Krosno Creek Up to 8 homes will remain at risk of flooding in a 100 year storm after the culvert replacements are constructed. The feasibility of site specific solutions for these homes, such as flood proofing, will be explored during subsequent phases of this study This area is the subject of a more detailed flood study prepared for the proposed development of the Downtown South lands NOTE: The extent of flooding shown above is distinct from the Toronto and Region Conservation Authority s (TRCA) Regulatory Flood Plain. The TRCA Regulatory Flood Plain adheres to MNR Guidelines which stipulate a number of conservative assumptions regarding the effect of existing structures that can reduce flow rates in the system (SWM ponds, restrictive culverts, etc.). For more information on the TRCA s Regulatory Flood Plain, contact Chris Jones at (416) ext or cjones@trca.on.ca 13

14 Next Steps November 2012 TMIG retained to undertake the Krosno Creek Diversion Project Class Environmental Assessment February 2013 Notice of Study Commencement published in the Pickering News Advertiser and mailed to residents and businesses in study area February 2014 Public Information Centre # 1 Present Study Overview, Existing Conditions, Alternative Solutions and Preliminary Preferred Solution Spring 2014 Public Information Centre # 2 Present Preliminary Designs for Culvert Replacements and other study updates Summer 2014 Final Study Posted for 30 Day Public Review Period Fall 2014 Detailed Design Funding to be considered in Capital Budget for 2015 Construction 14

15 Things You Can Do to Prevent Flooding Clear the gutters and catchbasins on the street near your house Don t blow yard waste (leaves, grass clippings) into the street or creeks Alert City Staff to debris (garbage, tree branches, ice) that may be blocking the flow in culverts and channels Call (905) to report debris or obstructions Keep Debris out of the Creeks Ensure that your downspouts discharge onto your lawn (at least 1.2 m away from basement walls), and consider installing a rain barrel 15