Basement Flooding Remediation and Water Quality Improvement Master Plan Class EA Study Area 41

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PUBLIC INFORMATION CENTRE #1October 5, 2016, 6pm – 8pm

Basement Flooding Remediation and Water Quality

Improvement Master Plan Class EA

Study Area 41

WELCOME

WELCOMEPURPOSE OF TONIGHT’S MEETING

• Introduce the problem and study objectives

• Present information on the causes of flooding

and the impacts of stormwater runoff

• Present possible alternative measures

• Present the criteria for evaluating the

alternative solutions

• Outline the next steps in the study process

• Hear from you! Your input is very important.

Basement Flooding Remediation and Water Quality Improvement Master Plan Class EA: Study Area 41

WELCOMEPURPOSE OF THIS STUDY

• Identify potential causes of basement and

surface flooding as they relate to the City’s

infrastructure;

• Identify and evaluate flooding remediation and

stormwater quality control alternatives;

• Recommend a preferred solution;

• Prepare an infrastructure implementation plan.


• Area 41 is located in Etobicoke and is serviced by a separate

storm and sanitary system.

• This area has experienced basement and surface flooding

incidents during severe storm events on May 12, 2000,

August 19, 2005, July 31, 2012, May 28, 2013 and July 8,

2013.

Characteristics Study Area 41

Study area size 1,829 hectares

Number of properties 8,123

Sanitary trunk North Mimico Sanitary Trunk Sewer

Major receiving watercourse Mimico Creek

Number of storm outfalls 60

Study Area 41

WELCOMESTUDY AREA 41


• The City of Toronto must follow the Municipal Class Environmental

Assessment (EA) process to meet the requirements of Ontario’s EA Act

for all infrastructure projects.

• The EA Act requires the “protection, conservation and wise management

of the environment” while undergoing infrastructure enhancements.

• The EA process is also an opportunity for the public and agencies to

provide input throughout the project.

MUNICIPAL CLASS ENVIRONMENTAL

ASSESSMENT (EA) PROCESS


Master Plans are conducted under the framework of the Municipal Engineers Association (MEA) Class EA process. They are long-

range plans that identify infrastructure requirements for existing and future land use within a larger study area, through the

application of EA principals. This study is undertaken as a Master Plan.

Public Information

Centre 1: Fall 2016

• Overview of Study

• Problem Statement

• Existing Conditions

• Alternative Measures

• Evaluation Criteria

• Next Steps

Identification of Problem

or Opportunity

Evaluation of Alternative

Solutions & Identification

of Recommended

Solution

Selection of Preferred

Solution Following

Consultation Activities

Master Plan is Filed and

Posted for Public

Viewing: Winter 2017

Phase 1 Phase 2

Public Information

Centre 2: Summer

2017

• Evaluation of Alternative

Solutions

• Identification of

Preferred Solution

• Next Steps

Notice of Study

Commencement

Notice of Public

Information

Centre 1

Notice of Public

Information

Centre 2

Ongoing Public & Agency

Consultation throughout the

Study

Notice of Study

Completion

We are

here

MUNICIPAL CLASS EA PROCESS


• Collecting and reviewing background data on land use, population, soil conditions, sanitary sewer and storm

drainage systems, flooding history, and operation/maintenance records.

• Conducting surveys to inventory the number of disconnected roof downspouts; survey catchbasins; identify low

lying areas; and conduct an inventory of storm outfalls.

• Consulting with the Public (1st Public Information Centre) and receiving feedback on potential measures to address

the issue of basement and surface flooding in the study area, and to improve stormwater runoff water quality

before it is discharged to the environment.

• Developing computer models to:

- Analyze the causes of basement and surface flooding, and predict flows under various weather conditions, and;

- Assess the impacts of stormwater runoff on water quality in Mimico Creek.

• Undertaking further assessment and refining measures.

• Presenting the alternative solutions (at 2nd Public Information Centre), and finalizing them based on input from the

public and agencies.

We are

here

STUDY OVERVIEW


The many steps involved in the study before a preferred solution can be

recommended include:

Basement and Surface Flooding

• On August 19, 2005 the City of Toronto suffered from flooding of

residents’ homes and damage to watercourses due to a large storm

event.

• The City of Toronto has developed a work plan for an engineering

review to address the basement flooding concerns across 67 areas

within the city.

• Study Area 41 has been subject to basement and surface flooding

incidents during major historical storm events, resulting in damage to

properties, infrastructure, and natural features.

PROBLEM STATEMENT


• Urbanization has not only increased surface runoff and

decreased infiltration into the ground, but has also increased

the potential for the transport of pollutants via surface runoff

from streets, parking lots and other hard surfaces.

• Stormwater runoff often contains heavy metals, bacteria,

nitrates/sulfates, salt, sand, grit, oil/grease, trash, and other

pollutants.

• Pollutants in the stormwater runoff adversely impact the

water quality of the receiving watercourse, which affects

fisheries, wildlife, recreational uses, visual aesthetics, etc.

Mimico Creek

PROBLEM STATEMENT


Stormwater Runoff Quality

FLOODING REPORTS



SANITARY SEWER SYSTEM

STORM SEWER SYSTEM


• Storm sewers (minor system) convey frequent, small storms.

• Streets (major system) convey major storms that exceed the storm sewer capacity.

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

STORM DRAINAGE SYSTEM


Sanitary SewerStorm sewer to

convey frequent,

small storms

Street to convey stormwater

flows above storm sewer

design capacity

Street right-of-way

AREAS OF RESPONSIBILITY


Watermain

Storm

Lateral

Water

Service

Roof

Downspout

Catch

Basin

Fire

Hydrant

Rear-yard

Catchbasin

Sanitary

Lateral

Storm

Lateral

City’s Responsibility:Public Lands – Any improvements to the sewer

and storm drainage system to be made within the

City’s property such as parks, roads, and sewer

infrastructure.

Property Owner’s Responsibility:Private Property Improvements – Each

homeowner is responsible for the operation and

maintenance of drainage systems on private

property which includes:

• Lot grading

• Driveway, front-yard and rear-yard

catchbasins

• Foundation drains

• Sump pumps and backwater valves

• Private tree roots

• What you put down the drains (fats, oils

grease, trash, etc.)

• Disconnecting roof downspouts

POTENTIAL CAUSES OF FLOODING


Cracked

basement floor

and blocked or collapsed foundation drains

Under normal rainfall events, the storm and sanitary sewer systems operate

as designed. However, during extreme storms, the following takes place:

• Connected roof downspouts contribute to stormwater flows exceeding the storm and sanitary

sewer capacity and overloading the system.

• Water remains on the surface and flows along roads and creeks. Surface water may enter

basements due to poor lot grading or drainage, and may enter through basement doors, windows,

cracks in basement floors and walls, and reverse-sloped driveways.

• At low lying areas, water accumulates (ponds) on the surface and enters the sanitary sewer

system through manhole covers. This causes the sanitary sewers to potentially backup into

basements.

• The ground becomes extremely wet and groundwater enters the sanitary system through cracks

in the pipes underground. This can also contribute to backup of the sanitary sewers.

Other factors causing sewer backups:

• Foundation drains connected to the sanitary sewer system;

• Oil/grease dumped into sanitary sewers causing blockages.

POTENTIAL CAUSES OF FLOODING IN AREA 41


SUMMARY OF SURVEY RESULTS


Floor Drain

48%

Toilet/Sink11%

Walls24%

Window10%

Door

7%

The water appeared to enter the basement from:

(152 total responses)

Questionnaires were made available to the residents of Area 41 to gather further information about flooding

events. Out of 256 surveys received to date:

• 163 cases of basement flooding were reported

• The water appeared dirty in 80 cases, and

oily/greasy in 2 cases

• 42% of responses indicated the water having an

odour

• An odour of sewage was reported in 34 cases

• An odour of dirt/mud was reported in 43 cases

• 93 properties reported to have backwater valves

installed (40% of 232 responses)

• 42 properties reported to have sump pumps installed

(18% of 231 responses)

• A significant portion of roof downspouts have been

disconnected from the sewer

General measures are presented. Detailed alternative solutions will be developed on a case-by-case assessment of

the City’s storm drainage and sanitary sewer networks. This will take place at a later time in the Master Plan Class EA

process and will be presented at the second Public Information Centre.

• Source ControlsMeasures involve managing stormwater where it originates (roofs,

roads, driveways), before it enters the City’s storm and sanitary systems.

• Conveyance ControlsMeasures to control storm and sanitary flows travelling along the

drainage systems (in sewers or along the road).

• End-of-Pipe ControlsMeasures to control storm and sanitary flows before discharging to the

receiver (watercourse, trunk storm sewer or trunk sanitary sewer).

MEASURES TO REDUCE BASEMENT AND SURFACE FLOODING

RISKS AND IMPROVE STORMWATER RUNOFF QUALITY


Potential measures that will be considered include:

Maintaining front and rearyard drainage and

driveway catchbasins

Installing and maintaining backwater valves and

sump pumps

Installing permeable paving

Disconnecting roof downspouts

Naturalizing the property (rain gardens, green roofs) Installing rain barrels

POTENTIAL MEASURES: PROPERTY OWNER


Residents can help reduce runoff – the water that flows from hard surfaces into the sewer system.

Naturalizing your property can improve stormwater runoff quality and may reduce the risk of basement flooding.

Source control measures that can be implemented by property owners include:

• Eliminating pesticide/fertilizer use

• Ensuring household chemicals such as

paint, oil, grease, soap, etc. do not

wash into the storm sewer

• Picking up pet waste

Surface Flow Path Diversion Surface drainage is directed away from low lying areas that have no direct outlet to reduce surface ponding depths.

“Curb cuts” can be added to redirect overland flow to strategic locations.

Sealing Maintenance Hole CoversMaintenance hole covers with perforations in low lying areas are sealed to reduce the amount of stormwater runoff entering the sanitary sewer system and reduce the risk of sanitary sewer capacity overload.

These source control

options help to:

reduce the risk of

basement flooding

improve stormwater

runoff quality

POTENTIAL MEASURES: SOURCE CONTROL


Replacement of Existing Storm and/or Sanitary Sewers

Existing storm and/or sanitary sewers with inadequate capacities to convey the required flows are replaced with larger pipes.

Construction of New Sewers

Existing sewer pipes remain in place and a new sewer pipe is installed to provide additional flow capacity.

These conveyance

control options help to:

reduce the risk of

basement flooding

improve stormwater

runoff quality

POTENTIAL MEASURES: CONVEYANCE CONTROL


Oversized Storage Pipes

New oversized pipes are constructed to temporarily store water and help relieve overloading of the storm and/or sanitary sewer system.

Catchbasin Inlet Control Catchbasin inlet controls are installed to limit stormwaterrunoff entering the storm system.

Increasing CatchbasinCapacity For existing storm sewers having capacity, the number of catchbasins are increased to capture more flow from the surface.

These conveyance


reduce the risk of

basement flooding

improve stormwater

runoff quality



These conveyance


reduce the risk of

basement flooding

improve stormwater

runoff quality



Infiltration/Exfiltration Systems

Stormwater conveyed in storm sewers can be released underground via

perforations (small holes) in the pipe to recharge the water table.

Bioretention UnitsBioretention units are plant and soil based, and provide low impact treatment and infiltration, for treating stormwater runoff in developed areas. These can be implemented in open areas such as ditches, boulevards or parks.

BioswalesBioswales are landscape elements designed to remove silt and pollution from stormwater runoff. These are designed with specific soil mixtures, surface plantings and underdrain within open areas such as ditches, boulevards or parks.

Pervious PavementPervious pavement is designed to allow percolation or infiltration through the surface into the soil below where the water is naturally filtered and pollutants removed.

These conveyance


reduce the risk of

basement flooding

improve stormwater

runoff quality



Underground Storage Tanks/Shafts

Dry Ponds Temporary storage of flows can be provided underground using tanks/shafts (for storm and sanitary systems), or above ground using dry ponds (storm drainage only). Once there are adequate flow capacities in the sewer systems, the flows from these storage facilities will be gradually released. Furthermore, underground storage tanks or shafts can be designed to provide treatment for stormwater through settling.

These end of pipe control

options help to:

reduce the risk of

basement flooding

improve stormwater

runoff quality

POTENTIAL MEASURES: END-OF-PIPE CONTROLS


Wet Ponds/ Constructed WetlandsWet ponds and constructed wetlands are basins that have a permanent pool of water throughout the year to store runoff during and after storm events. They treat and filter stormwater runoff through settling and through nutrient uptake by plants and other aquatic organisms.

Oil/Grit SeparatorsAn oil/grit separator is an underground structure connected to the storm sewer to improve stormwater quality by removing contaminants such as grease, oil, mud, sand and trash.

Wet ponds/constructed

wetlands help to:

reduce the risk of

basement flooding

improve stormwater

runoff quality

Oil/grit separators help to:

improve stormwater

quality


POTENTIAL MEASURES: END-OF-PIPE CONTROLS

Natural EnvironmentPotential impacts on:

• Terrestrial systems (vegetation,

trees, wildlife)

• Aquatic systems (aquatic life

and vegetation)

• Surface and groundwater

• Soil and geology

• Receiving water quality

Socio-Cultural• Land use impacts (parks, ravines,

open spaces)

• Disruption to existing community

during construction (traffic, noise)

and post-construction (visual

impact, odour, safety)

• Potential impacts to

archaeological and cultural

resources

• Impacts to First Nations

Technical • Effectiveness in reducing surface

and basement flooding and

improving stormwater runoff quality

• Feasibility of implementation

(available space, accessibility,

constructability, approvals)

• Potential impacts on upstream,

downstream, and surrounding area

infrastructure

• Impacts on operating and

maintenance requirements

EVALUATION CRITERIA


Economic• Capital cost

• Operating and

maintenance

costs

Alternative solutions will be evaluated

based on their ability to address the

Study’s purpose, stakeholder input,

and their potential impacts.

Evaluation criteria being considered

include:

Thank you for attending this Public Information Centre.

Next Steps• Please fill out a comment sheet.

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

• The recommended solution will be presented at the Public Information Centre #2 (Summer 2017).

Contact InformationIf you have additional questions or comments please contact:

Ms. Josie Franch

Public Consultation Unit, City of Toronto

Metro Hall, 19th Floor, 55 John Street

Toronto, ON M5V 3C6

Tel: 416-338-2859

Fax: 416-392-2974

TTY: 416-338-0889

Email: [email protected]

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


NEXT STEPS AND PROJECT CONTACT

Government & Nonprofit

Basement Flooding Remediation and Water Quality Improvement Master Plan Class EA Study Area 41