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Welcome

Basement Flooding Remediation and

Water Quality Improvement Master Plan

Environmental Assessment

Study Area 35

Public Information Centre #1

View displays and discuss the study with project staff

Feel free to ask questions and fill out a comment sheet

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Purpose of Tonight’s Meeting

• To introduce the problem and study approach

• To outline general factors contributing to surface and/or basement

flooding and surface water pollution

• Introduce possible alternative solutions and criteria for evaluating the

alternatives

• Outline the next steps in the study process

• Hear from you! Your input is very important.

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Purpose of Our Study

• Examine existing stormwater drainage and

sanitary sewer systems to identify the

potential causes of basement flooding

and/or surface flooding (severe ponding on

streets during extreme storms).

• Assess control measures to improve the

water quality of receiving water bodies as

per the City’s Wet Weather Flow Master Plan.

• Make recommendations to:

– Reduce the risk of future surface and

basement flooding

– Improve the quality of stormwater runoff

before it is discharged to watercourses

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Study Area 35

• Each Study Area is based on the tributary drainage areas for the sanitary and storm sewer systems.

• The storm system drains to Mimico Creek, Silver Creek, and the Humber River through 11 outfalls.

Area 41

Area 36

Area 51

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• 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,

following the Master Planning Process. We are currently in the late stages

of Phase 1.

• 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 Master

Plan Report for

30 Day Review

Notice of

Completion

We are here

PIC #2

Incorporate

Comments

PIC #1

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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;

• Consult with the public via Questionnaire and 1st Public Information Centre, to explain the

problem, introduce the objectives of the EA Study, and invite comments on resident

history of flooding and feedback on potential alternatives to reduce risk of flooding /

pollution;

• Develop computer models to:

– Analyze the causes of flooding and to estimate flows under various weather

conditions;

– Assess the impacts of stormwater runoff on water quality in receiving watercourses;

• Develop, assess and refine alternative solutions; and

• Present recommended alternative (at 2nd Public Information Centre) and finalize the

study recommendations with consideration of input from the public and review agencies.

Investigating Basement Flooding:

The Steps Involved

We

Are

Here

And

Here!

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Stormwater Pollution: The Problem

• Urbanization has altered the pathways

through which stormwater finds its way

back to rivers and lakes.

• Stormwater collects oil, dirt, pet waste and

other pollutants and carries them to rivers

and lakes.

• This results in degraded water quality as

well as:

• Impacts on fisheries and aquatic

habitat

• Reduced recreational use and

aesthetics.

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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 sewers to surcharge

and potentially back-up into basements.

Potential Flooding Factors

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During these heavy rainfalls, the ground becomes extremely wet and

unwanted water enters the sanitary system through cracks or broken pipes,

cracked maintenance hole walls, and loose joints underground. This

contributes to back-up of sanitary sewers.

Other factors related to sanitary sewer back-up include:

• Shallow groundwater table intersecting the sanitary sewer

• Downspouts connected to the sanitary sewer (directly or 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)

• Cross-connections between the storm and sanitary sewer systems

• Tree roots blocking private plumbing systems

• Grease build-up and/or blockages.

Potential Flooding Factors

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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.

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Areas of Responsibility

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Typical Rear-yard Catchbasin

Typical Sump Pump

Typical Foundation Drain

Any improvements to the

sewer and drainage system

will be made within the

City’s property such as

parks and roads.

Each homeowner is responsible for

the operation and maintenance of

drainage systems on their private

property which includes:

• Lot grading

• Front, rear-yard, or driveway

drainage and catchbasins

• Foundation drains

• Sump pumps and backwater

valves

• Private tree roots

• What you put down the drain

(no oil, grease)

• Disconnecting downspouts

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Methods for Reducing the Risk of Basement &

Surface Flooding & Improving Water 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).

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Potential 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

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Potential Solutions SOURCE CONTROLS

Replace Perforated Sanitary

Maintenance Hole Covers

Additional source control options: • Sewer Maintenance and Rehabilitation

• Involves CCTV, smoke/dye tests, sewer cleaning, relining, and repair

• Road Maintenance

• Involves street sweeping, seasonal leaf pick-up, catchbasin vacuum cleanouts

Surface Flow Path

Diversion

Pervious

Pavement

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

Sealing Maintenance

Hole Covers

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Potential Solutions CONVEYANCE CONTROLS

Description • An engineered pipe system that encourages everyday

rainfall to be infiltrated back into the groundwater table

before running down the storm sewer pipe

What Does it Involve? • Used where a storm sewer is already being replaced for

flood protection, an additional underground gravel

trench and perforated piping system is connected to

encourage infiltration

Exfiltration/Pervious Pipe Systems (Improve Stormwater Runoff Quality)

http://www.civil.ryerson.ca/urban/techno/stormwater/source/10-2-8/index.html

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Potential 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

Description • Maintain/enhance existing ditches and culverts which slow

down surface water and encourage infiltration/filtration

• Retrofit existing concrete curb and gutter streets with

grassed ditches/swales if opportunity exists

What Does it Involve? • Excavation of ditches and installation of shallow culvert

pipes where appropriate

Road Cross-Section Retrofits (Ditches) (Improve Stormwater Runoff Quality)

Local Bioretention Filters (Improve Stormwater Runoff Quality)

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Potential Solutions CONVEYANCE CONTROLS

Increase Number of Catchbasins

Overland (Major System) Control 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”

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

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Potential Solutions CONVEYANCE CONTROLS

Parking Lot Retrofit for Surface Storage

Catchbasin Inlet Controls

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

• 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)

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Potential Solutions CONVEYANCE CONTROLS

Adding New Sewers (Twinning)

Replacement of Existing Storm,

and/or Sanitary Sewers 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

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Potential Solutions END-OF-PIPE CONTROLS

Surface Wet Pond/Wetland (Reduces Flooding and Improves Runoff Quality)

Surface Dry Pond

Description • An engineered surface depression that controls the quantity of

inflowing stormwater through storage and slow release to the

receiving system

• Typically fills with water during extreme storm events and drains

within 24 to 48 hours or less

What Does it Involve? • Excavation and shaping of a suitable open space

• Addition of inlet/outlet structures

• Restoration and landscaping; signage

Description • An engineered pond or wetland with a permanent water surface

that controls the quantity and quality of inflowing stormwater

through storage and slow release to the receiving system

What Does it Involve? • Excavation and shaping of a suitable open space

• Addition of inlet/outlet structures

• Restoration and landscaping (aquatic and side-slope)

• Infrequent maintenance (sediment removal)

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Potential Solutions END-OF-PIPE CONTROLS

Oil & Grit Separator (Improves Stormwater Runoff Quality)

Underground Storage Tank (Reduces Flooding & Improves Water 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)

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The following criteria are suggested for evaluating each of the options and

identifying the recommended solutions:

Evaluation of Solutions

Natural Environment

• Potential Impact on

Terrestrial Systems

(Vegetation, Trees,

Wildlife)

• 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 Water

Quality

• Impact on Upstream,

Downstream and

Surrounding Areas

• Operations &

Maintenance

Requirements

• Basement Flooding

Prevention Effectiveness

Economic

• Capital Cost

• Operating and

Maintenance Cost

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Thank You for Attending

Next Steps

• Please fill out the comment sheet provided. We welcome your feedback!

• The study team will review and consider your comments in the evaluation of

alternative solutions.

• The next PIC is expected to be in late 2016 to present the recommended solutions.

Contact Information

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

project mailing list, please contact:

Josie Franch, Public Consultation Unit

55 John Street, Metro Hall, 19th Floor, Toronto, ON M5V 3C6

Phone: 416-338-2859, E-mail: jfranch@toronto.ca

Website: http://www.toronto.ca/bfea