Welcome KROSNO CREEK DIVERSION PROJECT PUBLIC INFORMATION CENTRE # 1 Tonight s Presentation Study Overview Background Existing Conditions Alternative Solutions Preliminary Preferred Solution Next Steps For more information, contact either of the following Mr. Tom Dole, P.Eng. Water Resources Engineer City of Pickering One The Esplanade Pickering, ON L1V 6K7 Tel: (905) 420-4660 Ext: 2156 Email: tdole@pickering.ca Mr. Steve Hollingworth, M.A.Sc., P.Eng. Consultant Project Manager TMIG The Municipal Infrastructure Group Ltd. 8800 Dufferin Street, Suite 200 Vaughan, ON L4K 0C5 Tel: (905) 738-5700 Ext. 359 Email: shollingworth@tmig.ca 1
Background Krosno Creek replaced with storm sewers during development of the area north of Highway 401. South of Highway 401, Krosno Creek is confined to a narrow concrete channel for a considerable distance In its current form, Krosno Creek cannot safely convey the flow from severe storms There was a considerable amount of flooding during a severe storm in August 2005 There continue to be risks for flooding and erosion along Krosno Creek 2
Background The Frenchman s Bay Stormwater Management Master Plan (FBSWMMP) was completed in 2009 The FBSWMMP looked at all of the watersheds draining into Frenchman s Bay, including Krosno Creek Recommendations from the FBSWMMP included a sewer north of Highway 401 to divert the flow from Krosno Creek to Pine Creek The Krosno Creek Diversion Study was initiated to investigate the causes of flooding and assess alternatives to reduce the risk of flooding in more detail 3
Municipal Class EA Process We are here 4
Natural Environment 5
Hydrologic and Hydraulic Model A SWMM5 computer model of the Krosno Creek watershed was created. Storm sewers, overland flow routes and the open channels are represented in the model The model was calibrated and verified against observed water levels and flow rates at the streamflow gauge located south of Alyssum Street 6
Existing Level of Service: Flooding The culverts under Highway 401 and the CNR significantly reduce the peak flow rates in the downstream sections of Krosno Creek The culvert at Reytan Blvd is a significant bottleneck in the system Few buildings are at risk of flooding downstream of the concrete lined section of Krosno Creek 7
Existing Level of Service: Flooding Storm Event Buildings Impacted Estimated Flood Damages* 2 4 $130,900 5 15 $493,000 10 56 $1,685,900 25 56 $1,685,900 50 62 $1,866,600 100 64 $1,932,700 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 8
Alternative Solutions Channel Improvements A wide, natural corridor could safely convey the runoff from severe storms, even if the Highway 401/CNR culverts were enlarged in the future The wide, naturalized corridor would improve fish and wildlife habitat and provide recreational opportunities Up to 46 properties would need to be acquired to implement the channel Total Cost: $24.4 Million 9
Alternative Solutions Enhanced SWM Controls The Pickering City Centre is planned for redevelopment and intensification New and re-development will adhere to modern stormwater management practices and criteria When fully built out, average annual flood damages will be reduced from $390,000/year to $240,000/year, with negligible costs for the City. Water quality and erosion in Krosno Creek will also be improved It will take a long time for full build-out of the plan 10
Alternative Solutions Culvert Improvements The existing culverts at Morden Lane, Reytan Boulevard and Alyssum Street are bottlenecks in the system. The corrugated steel pipe-arch culverts at these three crossings could potentially be replaced with twin 3 m wide concrete box culverts The culvert replacements could be constructed relatively quickly and easily The culvert replacements could reduce average annual flood damages from $390,000/year to $46,000/year Total Cost: $1.4 Million The culverts are not in good condition, and will require replacement in the near future regardless 11
Alternative Solutions Diversion to Pine Creek This was recommended in the Frenchman s Bay Stormwater Management Master Plan A large sewer would convey all of the flow from Krosno Creek to Pine Creek north of Highway 401 Pine Creek Improvements to Pine Creek would be needed to mitigate flooding impacts along Pine Creek If combined with culvert improvements on Krosno Creek, no buildings would be flooding during even the most severe storms, and even if the Highway 401 / CNR culverts were enlarged Total Cost: $30.4 Million 12
Alternative Solutions Krosno Boulevard Relief Sewer This relief sewer would divert a portion of the flow in Krosno Creek away from the most flood prone area and return the flow to Krosno Creek below Alyssum Street A 3.0 m wide x 1.5 m high concrete box sewer could be installed, though construction might be difficult The culvert replacements could reduce average annual flood damages from $390,000/year to $32,000/year, but would not significantly reduce flooding during the most severe storms Total Cost: $5.8 Million 13
Alternative Solutions Flood Proofing Rather than reducing the frequency or severity of flooding, flood proofing measures prevent floodwater from entering buildings 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 These measures are very difficult to implement, and it is very difficult to ensure they are maintained and remain effective following future home renovations Cost: $10,000 per flood prone property, on average ($640,000 to protect all 64 flood prone buildings) 14
Evaluation of Alternatives Alternative Do Nothing Natural Environment Social/Cultural Environment Technical Environment Overall Impacts Benefits Challenges Performance Impact Cumulative Impacts Benefits Cumulative Benefit No impacts, as no works are Continued erosion and No impacts, as no works are No benefits, as no works are No challenges, as no works No reduction in the frequency proposed impaired water quality in proposed proposed are proposed and severity of flooding NOT RECOMMENDED Krosno Creek Does not reduce flooding, other alternatives exist with acceptable impacts Financial Environment No direct costs Average annual flood damages: $390 Thousand Creek Improvements to Convey the Regulatory Flow Impacts to existing channel and riparian vegetation during construction Replacement of the concrete lined channel with a natural channel and wide, vegetated valley corridor Approximately 45 homes will need to be purchased/ expropriated and demolished to create channel corridor Creation of new, natural public open space, could incorporate a trail system in 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 $24.4 Million Average annual flood damages: $0 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 Minimal additional direct costs to the City for infrastructure renewal projects Average annual flood damages: $240 Thousand 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 practices, will need to bypass flow around the work areas Significant reduction in the frequency and severity of 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 $1.4 Million Average annual flood damages: $46 Thousand 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 $30.4 Million Average annual flood damages: $0 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 $5.8 Million Average annual flood damages: : $32 Thousand 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 $660 Thousand Average annual flood damages: $0 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 15
Preliminary Preferred Solution 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 16
Next Steps NOW Re-evaluate the alternative solutions based on feedback received tonight Spring 2014 Prepare preliminary designs for culvert replacements Spring 2014 Present preliminary culvert designs at PIC # 2 Summer 2014 Prepare Environmental Study Report and post for 30 day review Fall 2014 Prepare detailed designs for culvert replacements 2015 Funding to be considered in Capital Budget for 2015 Construction 17
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 watercourses Ensure that your downspouts discharge onto your lawn, and consider installing a rain barrel Keep Debris out of the Creeks Alert City Staff to debris (garbage, tree branches, ice) that may be blocking the flow in culverts and channels Call (905) 683-7575 to report debris or obstructions 18