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1. Welcome
Investigation of Basement Flooding and
Stormwater Runoff Quality Control
Study Areas 21 & 23
Public Information Centre #1
View displays and discuss the study with project staff
Feel free to ask questions and fill out a comment sheet

2. Purpose of Tonight’s Meeting
• To introduce the problem and study approach
• To outline potential factors contributing to surface and/or basement
flooding and stormwater runoff pollution
• Present 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.

3. 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.

4. Study Area
• Study Area is made
up of two Basement
Flooding Areas;
21 & 23.
• Study Area is based
on the tributary
drainage areas for
the sanitary and
storm sewer system.

5. • 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
early 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

6. Municipal Class EA Planning and
Design Process
Note: This flow chart is meant to be read in conjunction with Part A of the Municipal Class EA

7. 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);
• Undertake assessment and refinement of alternatives; and
• Present recommended alternative (at 2nd Public Information Centre) and finalize the study
recommendations based on input from the public and review agencies.
Investigating Basement Flooding:
The Steps Involved
We
Are
Here

8. 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.

9. 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.
Potential Basement Flooding Factors

10. During these 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.
Other 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)
• Cross-connections between the storm and sanitary sewer systems
• Grease build-up and/or blockages.
Potential Basement Flooding Factors

11. 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.

12. 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).

13. 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 ToxinsPermeable 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

14. Potential Solutions
SOURCE CONTROLS
Sealing Maintenance
Hole Covers
Additional source control options:
• Sewer Maintenance and Rehabilitation
Involves:
• Sanitary Sewer: CCTV, smoke/dye tests, sewer cleaning, relining, and repair
• Storm System: 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.

15. 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)

16. 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

17. 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)

18. Potential Solutions
CONVEYANCE CONTROLS
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

19. 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)

20. Potential 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)

21. 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 Runoff
Quality
• Impact on Upstream,
Downstream and
Surrounding Areas
• Operations &
Maintenance
Requirements
• Basement Flooding
Prevention Effectiveness
Economic
• Capital Cost
• Operating and
Maintenance Cost

22. 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 2014 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/involved/projects/basement_flooding/sa_21_23.htm