Welcome

Basement Flooding Remediation and

Water Quality Improvement Master Plan

Environmental Assessment

Study Area 37

Public Information Centre #1

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 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.

Purpose of Our Study

• Examine existing stormwater drainage,

combined 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 basement

flooding

– Improve the quality of stormwater runoff

before it is discharged to watercourses

Study Area

• York-Cedarvale Area

• Generally bounded by Bathurst, Dufferin, St Clair and Eglinton

• Study Area is based on the tributary drainage areas for the combined sewer system.

• 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 (October 2000, as

amended in 2007, 2011 & 2015), 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

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, combined

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, inspect combined sewer overflow structures, 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 and combined sewer overflows 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 on input from the public and review agencies.

Investigating Basement Flooding:

The Steps Involved

We

Are

Here

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.

• Relief structures in the combined system,

intended to reduce flood risk, can result in

sewer overflow to the environment.

• This results in degraded water quality as

well as:

• Impacts on fisheries and aquatic

habitat

• Reduced recreational use and

aesthetics.

Under normal rainfall events, the storm, combined 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 combined or sanitary sewer system

through manhole covers. This causes sewers to

surcharge and potentially back-up into

basements.

Potential Basement Flooding Factors

During these heavy rainfalls, the ground becomes extremely wet and unwanted

water enters the sanitary/combined system through cracks or broken pipes,

cracked maintenance hole walls and loose joints underground. This contributes

to back-up of the sanitary/combined sewers.

Other factors related to sanitary/combined sewer back-up include:

• Shallow groundwater table intersecting the sewers

• Downspouts connected to the sewer (direct 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

the sewer)

• Interconnections between the road storm and combined sewer systems

• Downstream creek and/or trunk sewer water levels

• Grease build-up and/or blockages.

Potential Basement Flooding Factors

Typical Sewer System Configuration Case 1 – Combined Sewer

Note: Typical connections shown,

however, private drainage systems

can be more complex and each one

is unique. For example, there could

be other combinations of

connections shown.

Typical Sewer System Configuration Case 2 – Partially Separated Sewer

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

combined/sanitary and storm systems

or other combinations of connections

shown.

Typical Sewer System Configuration Case 3 – Separated Sewer – Isolated System

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.

Methods for Reducing Basement Flooding

and 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), or control

combined sewer overflow discharge so that it can be treated or

re-released back into the combined sewer system for treatment

at the wastewater plant.

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

Potential Solutions SOURCE CONTROLS

Replace Perforated

Maintenance Hole Covers

Additional source control options: • Sewer Maintenance and Rehabilitation

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

• 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

Potential Solutions CONVEYANCE CONTROLS

Description • At existing combined sewer overflow locations, either to a

storm sewer or the natural environment, adjust or remove the

structure to reduce discharge during extreme events

What Does it Involve? • Redesign of underground structures such as interconnecting

pipes and weirs, to reduce or eliminate overflow

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)

Combined Sewer Overflow

Modifications (Improve Water Quality)

http://www.hkywater.org/departments/wastewater/combined-sewer-system

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

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 • In place of concrete curb and gutter, replace with grassed

ditches and a series of culverts which slows surface water

down and encourages infiltration/filtration

What Does it Involve? • Removal of curb and gutter (if existing) and reconstruction

of roadway and boulevard

• Installation of shallow culvert pipes

Alternate Road Cross-Sections (Ditches) (Improve Stormwater Runoff Quality)

Local Bioretention Filters (Improve Stormwater Runoff Quality)

Potential Solutions CONVEYANCE CONTROLS

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”

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

Potential Solutions CONVEYANCE CONTROLS

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

• 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)

Potential Solutions CONVEYANCE CONTROLS

Adding New Sewers (Twinning) (Controls Basement Flooding)

Replacement of Existing Storm,

Combined 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

Potential Solutions END-OF-PIPE CONTROLS

Wet Pond/Wetland (Controls Basement Flooding and Can

Improve Runoff Quality)

Dry Pond (Controls Basement Flooding)

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)

Potential Solutions END-OF-PIPE CONTROLS

Oil & Grit Separator (Improves Stormwater Runoff Quality)

Underground Storage Tank (Controls Basement Flooding & Can Improve

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)

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 Water

Quality

• Impact on Upstream,

Downstream and

Surrounding Areas

• Operations &

Maintenance

Requirements

• Basement Flooding

Prevention Effectiveness

Economic

• Capital Cost

• Operating and

Maintenance Cost

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

evaluation of alternative solutions.

The next PIC is expected to be held 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:

Mae Lee, Public Consultation Unit

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

Phone: 416-392-8210, E-mail: rmlee@toronto.ca

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