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Welcome

Investigation of Basement Flooding and Stormwater Runoff Quality Control

Study Areas 21 & 23

Public Information Centre #2

View displays and discuss the study with project staff

Feel free to ask questions and fill out a comment sheet

Purpose of Tonight’s Meeting

• To provide background and review the study process / findings for Study Areas 21 & 23

• To present preliminary recommended solutions to alleviate surface and basement flooding and improve stormwater runoff quality to the receiving watercourses including Wilket Creek and the East Don River

• Hear from you! Your input and comments are very important and will be considered in finalizing the preferred solutions for the study

• Outline the next steps in the study process

Purpose of Our Study

• Examine existing stormwater drainage and sanitary sewer systems to identify the causes of basement flooding and/or surface flooding (severe ponding on streets during extreme storms).

• Assess control measures to improve the quality of stormwater surface runoff as per the City’s Wet Weather Flow Master Plan.

• Make recommendations to: – Reduce the risk of future flooding – Improve the quality of stormwater runoff

before it is discharged to watercourses.

Study Areas

• The Study Areas 21 & 23 are based on the tributary drainage areas for the sanitary and storm sewer systems.

• These areas have experienced surface and basement flooding during extreme storm events (May 12, 2000, August 19, 2005, July 8, 2013 and others).

• Storm sewers in both areas primarily drain to the East Branch of the Don River. A small area drains to Wilket Creek.

• The City must meet the requirements of Ontario’s Environmental Assessment (EA) Act for infrastructure projects.

• This project requires completion of Phases 1 and 2 of the Class EA process as set out by the Municipal Engineers Association. We are currently in the final stages of Phase 2.

• The EA process is an opportunity for the public and agencies to provide input. Consultation is facilitated via two rounds of Public Information Centres (PICs).

Municipal Class Environmental Assessment Process

PHASE 1 PHASE 2

Problem Or Opportunity

Alternative Solutions

Submit Project File for 30 Day

Review

Project Completion

We are here

PIC #1 & PIC #2

Incorporate Comments

Many steps are involved in the study before solutions can be recommended. This work includes: • Collect and review background data on land use, population, soil conditions, sanitary sewer

and storm drainage systems, flooding history, and operation/maintenance records • Conduct field surveys to inventory the number of roof leaders disconnected, survey catchbasins,

identify low lying areas, and inventory storm sewer outfalls • Develop computer models to:

– Analyze the causes of flooding and to predict flows under various weather conditions – Assess the impacts of stormwater runoff on water quality in receiving watercourses

• Develop and receive feedback on potential alternatives to address the issue of flooding in each basement flooding area and improve stormwater runoff water quality before it is discharged to the receiving watercourses (1st Public Information Centre held on June 24, 2014)

• Identify and assess alternatives and present recommended solutions (2nd Public Information Centre)

• Gather input from the community and review agencies and undertake further assessment and refinement of alternatives

• Finalize EA study based on input from public and review agencies.

Investigating Basement Flooding: The Steps Involved

We Are Here

Areas of Responsibility

Typical Sump Pump

Typical Foundation Drain

Typical Rear-yard Catchbasin

Watermain

Storm Lateral

The homeowner is responsible for the operation of drainage systems on private property, including grading, front and rear-yard or driveway catchbasins, foundation drains, sump pumps, backwater valves, service laterals, tree roots, downspouts, and what you put down the drains (fats, oils, grease, non-disposable wipes, etc.).

Water Service

Roof Downspout

Catch Basin

Fire Hydrant

Rear-yard Catchbasin

Sanitary Lateral

Storm Lateral

Drainage Systems Design and Operation

• Storm sewers (minor system) drain runoff generated from everyday rainfall events, defined as the 1 in 2 year design storm (50% chance that an event of this magnitude will occur in any year).

• Streets and overland flow paths (major system) convey major rain storms that exceed the storm sewer capacity.

• Temporary ponding on streets is expected during these major rain storms.

Street Right-of-Way

Water Level in Street to be Within Right-of-Way Limits

Sanitary Sewer to

Treatment Plant

Storm Sewer to Don River

CatchBasin

Water Level in Storm Sewer to be Below Basement Elevation up to 1 in 100 year storm (1%

chance of occurring in any year) Water Level in Sanitary

Sewer to be Below Basement Elevation

Under normal rainfall events, the storm and sanitary sewer systems operate as designed. However, during extreme storms, the following takes place: • Stormwater flow exceeds the storm sewer capacity and overloads the

system. • Directly connected roof drains, especially flat roofs, contribute significant

volumes to the sewer system. • Water remains on the surface and flows

overland along roads. • At low lying areas, water accumulates (ponds)

and enters the sanitary sewer system through manhole covers. This causes the sanitary sewers to surcharge and potentially back-up into basements.

Our Basement Flooding Findings

During heavy rainfalls, the ground becomes extremely wet and water enters the sanitary system through cracks or broken pipes, cracked maintenance hole walls and loose joints underground. This contributes to back-up of the sanitary sewers. Factors related to sanitary sewer back-up include: • Shallow groundwater table intersecting the sanitary sewer • Downspouts connected to the sanitary system through weeping tiles • Water entering the basement from the surface via window sills and reverse-

slope driveways etc. and then through basement floor drains (connected to sanitary sewer)

Our Basement Flooding Findings

Typical Causes of Basement Flooding

Note: Typical connections shown, however, private drainage systems can be more complex and each one is unique. For example, there could be interconnection between the sanitary and storm systems or other combinations of connections shown.

• Urbanization has not only increased the volume of surface runoff and decreased infiltration into the ground, but has also increased the potential for transport of pollutants from streets, parking lots and other hard surfaces to receiving watercourses.

• Stormwater runoff often contains grit, oil/grease, heavy metals (zinc, lead, etc.), bacteria, nitrates/sulfates, salt and other pollutants.

Our Stormwater Runoff Quality Findings

• These pollutants adversely impact the water quality of the watershed, affecting fisheries, wildlife, recreational uses, visual aesthetics, etc.

• There are 31 storm sewer outfalls in Area 21 and 19 in Area 23

• Most of these outfalls are ultimately tributary to the East Branch of the Don River except for five outfalls in Area 21 which flow to Wilket Creek.

Area 21 Outfall

The following criteria were used to evaluate strategies and identify the recommended solution alignments:

Evaluation of Solutions

Natural Environment • Potential Impact on

Terrestrial Systems (Vegetation, Trees, Wildlife, Stream Erosion)

• Potential Impact on Aquatic Systems (Aquatic Life and Vegetation, Surface Water Quality, Groundwater, Receiving Watercourses)

• Soil and Geology

Socio-Cultural • Effect on Urban

Greenspace (Parks, Ravines, Open Spaces)

• Disruption to Existing Community During Construction (Traffic, Noise)

• Disruption to Existing Community Post Construction (Visual Impact, Odour, Safety)

• Archaeology and First Nations

Technical • Feasibility of Control

Measure (Available Space, Accessibility, Constructability)

• Ability to Improve Stormwater Runoff Quality

• Impact on Upstream, Downstream and Surrounding Areas

• Operations & Maintenance Requirements

• Basement Flooding Prevention Effectiveness

Economic • Capital Cost • Operating and

Maintenance Cost

Methods for Reducing Basement Flooding and Improving Stormwater Runoff Quality

Source control measures involve managing stormwater where it originates (roofs, roads, driveways), before it enters the City’s sewer pipes.

Source Controls

Conveyance Controls

End-of-Pipe Controls

Conveyance control measures help to control stormwater as it travels along the drainage system (in pipes or along the road).

End-of-pipe control measures control stormwater just before it is discharged to a watercourse (stream, river, or lake).

Recommended Solutions SOURCE CONTROLS

Rain Barrels Rain Gardens Tree Planting

Residents can help reduce runoff – the water that flows from hard surfaces into the sewer system. Naturalizing your property lowers the risk of basement flooding and contributes to improving stormwater runoff quality.

Downspout Disconnection

Reduce Toxins Permeable Paving • Eliminate pesticide/fertilizer use • Do not let household

chemicals such as paint, oil, grease, salt, soap, etc. wash to the storm sewer

• Pick-up pet waste

Soakaway Pits Green Roofs

Downspout Disconnection SOURCE CONTROLS

The City has a By-Law making downspout disconnection mandatory in basement

flooding areas, where feasible.

Benefits of Disconnecting your Downspout: • Helps reduce the amount of stormwater

that is sent into the sewer system.

• Helps to replenish and protect the groundwater table and reduces and delays stormwater runoff – helping to prevent flash flooding in rivers and streams.

• Less stormwater in the system will help prevent wastewater from backing up into basements.

• Leads to lower energy costs at

wastewater treatment facilities – producing fewer greenhouse gas emissions.

• This bylaw came into effect December 3, 2013 for properties in basement flooding areas.

• For combined sewer service areas and properties outside basement flooding areas, this bylaw will come into effect December 3, 2016.

• If disconnection is not technically feasible or would create a hazardous condition, owners can apply to the City for an exemption.

Recommended Solutions SOURCE CONTROLS

Sealing Maintenance Hole Covers in Low

Lying Areas

Additional Source Control Recommendations: • Sanitary Inflow and Infiltration Monitoring and Investigations to plan strategic maintenance and

rehabilitation programs • Sewer Maintenance and Rehabilitation

Surface Flow Path Diversion

Pervious Pavement

These measures can also help reduce the amount of runoff entering the sewer system.

o Sanitary Sewer: CCTV inspections, smoke/dye tests, sewer cleaning, relining, and repair o Storm System: Street sweeping, seasonal leaf pick-up, catchbasin vacuum cleanouts, sewer

flushing, CCTV inspections

Recommended Solutions CONVEYANCE CONTROLS

Description • A vegetated depression and underground trench designed to

filter stormwater runoff to remove pollutants and promote infiltration/evapotranspiration

What Does it Involve? • Diversion of small overland or piped drainage areas for small

storm events • Excavation of a trench with specific soil mixture, surface

plantings and underdrain within an open area such as a boulevard or park

Recommended Locations • Investigate opportunities associated with any road

reconstruction effort, in tandem with community input

Description • Alternate method of storm sewer construction which slows runoff

during everyday rainfall and encourages filtering of pollutants through a gravel medium before entering the storm sewer

What Does it Involve? • During road reconstruction work, excavation of a trench and

reconnection of catchbasins to a new perforated pipe system

Recommended Locations • Investigate opportunities associated with any sewer / road

reconstruction projects.

Sewer Filtration Systems (Improve Stormwater Runoff Quality)

Local Bioretention Filters (Improve Stormwater Runoff Quality)


Increase Number of Catchbasins (Controls Basement Flooding)

Overland (Major System) Control (Controls Basement Flooding)

Description • The diversion of surface drainage away from low lying

areas that have no direct outlet to reduce surface ponding depths

What Does it Involve? • Addition of “speed bump” or “curb cut” to redirect

overland flow to strategic locations • Interception of road or boulevard flows to dedicated

major system sewer with large inlet grate or “curb drain”

Recommended Locations • See large maps for locations

Description • Where the storm sewer has existing capacity, add more

catchbasins to capture more flow from the surface

What Does it Involve? • Minor street excavation for installation of new

catchbasin(s) and connection to storm sewer • Curb replacement and road restoration



Parking Lot Retrofit for Surface Storage (Controls Basement Flooding)

Catchbasin Inlet Controls (Controls Basement Flooding)

Description • Installation of inlet control devices (ICDs) on catchbasins

to limit release into the storm sewer system to control back-up (surcharge)

What Does it Involve? • A plastic or metal plate / device installed inside the

catchbasin outlet (not visible from surface) • Minimal effort and time to install • Strategically keeps more water on the surface


Description • Installation of ICDs in parking lots to store stormwater on

surface • Installation of roof drain controls to store stormwater on

large flat roof areas

What Does it Involve? • Retrofit of City-Owned property (where physically

possible)

Recommended Locations • Where opportunities exist


Adding New Sewers (Twinning) (Controls Basement Flooding)

Replacement of Existing Storm and/or Sanitary Sewers (Controls Basement Flooding)

Description • Increase the size of the sewer pipe by replacing the old sewer with a

larger pipe

What Does it Involve? • Road excavation within City limits • Removal of old sewer and structures (manholes & catchbasins) and

disconnection of sewer service line(s) • Placement of new sewer, reconnection of sewer service line(s) and

restoration of road and boulevard


Description • Increase the capacity of the sewer system by adding another sewer

pipe in addition to the existing pipe

What Does it Involve? • Road excavation within City limits • Replacement of old structures (manholes & catchbasins) and

reconnection of sewer service line(s), if necessary • Placement of new sewer, reconnection of sewer service line(s) and

restoration of road and boulevard



Stormwater Tunnel to New Outfall (Controls Basement Flooding)

Underground Oversized Storage (Controls Basement Flooding)

Description • Increase a portion of sewer pipe by replacing the old sewer with a

larger ‘super-pipe’ to provide temporary storage of water • Once sewer capacity is available, water is gradually released

What Does it Involve? • Road excavation within City limits • Removal of old sewer and replacement/placement of new sewer

and restoration of road and boulevard


Description • Relieve the capacity of the sewer system by adding a new deep

sewer pipe to divert a portion of flow to a new outfall

What Does it Involve? • Tunnelling deep underground with trenchless technology to avoid

traffic disruption associated with normal open trench excavation • Periodic access shafts requiring temporary road excavation with

City limits during construction • Construction of a new storm outfall to watercourse, underground

storage facility, or surface pond facility


Recommended Solutions END-OF-PIPE CONTROLS

Oil & Grit Separator (Improves Stormwater Runoff Quality)

Underground Storage Tank (Controls Basement Flooding & Can Improve

Stormwater Runoff Quality)

Description • An underground tank or pipe that controls the rate of

inflowing sanitary or stormwater through temporary detention and slow release to the receiving sewer, reducing the potential for flooding

What Does it Involve? • Excavation and construction of tank or pipe, including inlet

and outlet structures • Infrequent maintenance (monitoring, clean-out)


Description • An underground separation tank that takes the place of a

conventional manhole and provides a measure of treatment for small drainage areas

What Does it Involve? • Similar to a manhole, minor street excavation for installation

of structure • Road restoration • Annual maintenance (vacuum clean-out)

Recommended Locations • Distributed throughout study area.

Recommended Solutions STORMWATER QUALITY IMPROVEMENT OPPORTUNITIES

• Where soils have high permeability, overlapping sewer projects will consider Local Bioretention Filters and Sewer Filtration Systems.

• Oil and Grit Separators (OGS) are placed in highly paved locations.

• There are no opportunities for new end-of-pipe pond / tank facilities due to space.

Thank You for Attending We welcome your feedback. Please fill out the comment sheet provided.

• Following this PIC, the study team will review and consider your comments in the finalization of the preferred solutions.

• The Project File that documents the study’s findings and recommendations is expected to be available for a 30 day review period in the summer of 2015.

• The City will implement the recommended solutions pending completion of the Environmental Assessment, future regulatory and budgetary approvals, and coordination with other planned infrastructure projects in these areas.

Contact Information For more information on this study, to provide your comments, to be placed on the

project mailing list, or to receive a copy of these boards please contact: Josie Franch, Public Consultation Unit 55 John Street, Metro Hall, 19th Floor

Toronto, ON M5V 3C6 Phone: 416-338-2859, E-mail: [email protected]

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quality of stormwater

causes of flooding

basement flooding area

study process purpose

issue of flooding

study process findings

impacts of stormwater

storm sewer systems