Transcript Public Information Centres

Public Information Centre Slides
July 23 and August 11, 2008
Storms
with added annotations
June 25, 2009
July 23, 2008 Storm
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August 11, 2008 Storm
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Comments on Storms
• Radar Loops show intense storms with
intensities exceeding 100 mm/hr (see
colour bar on right)
• 10 minute interval does not capture largest
peak
• Narrow band results in selective flooding
– For example, on July 23, no rain south of
Taunton
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Impacts July 23
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Impacts Aug 11(including Sanitary Basement flooding
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)
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Comments on Photos
• Overland flow on road
– From property line to property line is acceptable
– Emergency vehicle access permits no more than 300
mm (1 foot) of water
• Flow into parks is desirable
• Major – Minor Storm System
– Underground sewer handles ‘normal’ storms that
occur annually (aka minor system)
– Excess flow is handled by overland flow (aka major
system) for storms that occur only once every 10
years or less frequently
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Analysis - CLOCA
Estimates Based on Rain Gauge Stations at Specific Locations (not in direct
path of storm)
CLOCA data based on 15 minute counts of tipping buckets and is used for
stream basin analysis. Might not capture intense peaks of short duration
required for subdivision analysis. Classification of return period is based on
peak intensity and duration factors NOT total rainfall.
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Analysis – Town of Whitby (July 23)
Estimated Intensities from Radar Loop
120
Bayberry
100
Brookvalley
East Ph 3
100 yr
80
Intensity (mm/hr)
50 yr
25 yr
60
10 yr
40
Winchester
20
0
-20
0
20
40
60
80
100
120
140
-20
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Time (min)
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Analysis – CLOCA (August 11)
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Runoff
• Rain that soaks into ground does not
runoff into storm sewer
• On grass 90% typically soaks in
– 10% runoff
– Design assumes 80% to account for hard
ground; 20% runoff
– For subdivision 50% is assumed to soak into
ground
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Antecedent Moisture Conditions
from CLOCA data
Saturated ground created by several days of rain cannot absorb rainfall on
July 23, 2008 resulting in up to double the flow in subdivisions. Since
underground sewer (minor system) takes part of flow, overland flow (major
system) may be up to triple the normal flow.
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Antecedent Moisture Conditions
from CLOCA data
Saturated ground created by several days of rain cannot absorb rainfall on
August 11, 2008 resulting in up to double the overland flow in subdivisions.
Since underground sewer (minor system) takes part of flow, overland flow
(major system) may be up to triple the normal flow.
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Design Standards
• Based on Historical Storms from past century
• Underground storm sewer (minor system)
– designed for most storms
– including those that occur only every 5 years
• Flow 2/3 full with this storm
• Overland flow (major system)
– Up to storm that occurs only once every 100 years
with 25% safety factor
• In this century storms are predicted to be twice
as often and more intense
• Sanitary sewer designed for ‘Superbowl Sunday
toilet flush’ NOT for storm flows
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Result of Excess Overland Flow
• Extra depth of overland flow pushed extra
water into underground storm sewer
• For example, a double catch basin
– 50 mm (2”) => 20 L/s
– 100 mm (4”) => 90 L/s
– 150 mm (6”) => 170 L/s
– 300 mm (12”) => 400 L/s
– Based on MTO charts
•
400 L/s exceeds pipe capacity
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Result – Basement Flooding
• When underground sewer is full
– Downspouts back up
– Foundation weepers fill with water
– Water seeps into cracks in foundation
• If floor drain is connected directly
– Water flows quickly into basement
– Example: Heber Down Crescent, North Street
• Homeowners should modify plumbing to connect
floor drain to Sanitary Sewer instead of Storm
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Ancillary Sanitary Sewer Backup
• Around basement the flow from backup of storm
sewer
– Infiltrates into nearby sanitary sewer
• Through cracks in sanitary clay or plastic pipe
• Illegal* weepers attached to sanitary sewer or floor drain
– Infiltrates into basement
• Cracks in foundation and floor
• Flows to floor drain and sanitary sewer
• Downspouts ‘illegally’* connected to sanitary
sewer
– Direct flooding of smaller sanitary sewer
– *See new regional by-laws
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Analysis Pattern Observed
• Clusters of basement flooding occurred at
overland flow concentrations
– Bayberry, Downey, Rosewood, Kilbride are
very clear examples of this clustering
• Deep ditches and large inlet controls OR
double catchbasins in sag all in overland
flow route were adjacent to almost all
instances of overland flooding
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Summary
• Design data from last century would not
predict the volumes of overland flow
– Reality of Climate Change is increased
intensity and frequency of storms
• Volume increased by
– Peak intensities not measured by CLOC
– Saturated Ground
• How can we adapt to new reality?
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Solution
• Inlet Controls
Drawing from IPEX Brochure
– Restrict flows into the underground storm sewer
– Adaptation to new reality of extreme storms
– Recommended by recent literature and used in
several other municipalities
• Overland Flow enhancements
– Remove excess overland flow from streets by
• Lowering curbs at overland flow route
• Lowering grading of boulevard at low point
• Removing obstacles in overland flow route
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Restricting Flows
Major and Minor System – Surface and Underground Storm Sewers
Drawing from IPEX Brochure
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Comment on Overland Flow
• The additional water on the surface of the
road should be minimal
– 300 mm (1 foot) of water in a 900 mm pipe is
less than 30 mm of water on a 9 m wide road
Small increase in depth on
surface
Overland flow - Major system
curb
Large reduction in depth
In underground sewer
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Minor system
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Affected Areas – July 23, 2008
• Heber Down Crescent (AECOM Review)
– Including Torian and Montgomery south of Vipond
• Centre and North Streets
• Downey Drive
• Underwood Drive, Tremount Street, Durham Street,
*Ipswich Place, *Princeton Court
• *Bayberry Crescent (Sernas Report)
• *Helston Crescent (Sernas Report, SKA Review)
– Including Covington Drive, Corsham Drive, Hesham
Drive
• **Carnwith Condos at Croxall Drive
– Consultant reports that ICD was installed
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*not assumed, **private site
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Affected Areas – August 11, 2008
• Kilbride Drive (AECOM Report)
– Including Cahill Court, O’Malley Crescent
– Anderson and Taunton road flooding
• Rosewood Court
• Walton Court
• *Annes Street (Regional Flooding Study)
– Including McCullough Blvd, Michael Blvd, Newman
Cres, Gilbert St, Maria St, etc
• *Lupin Drive and surrounding streets
• *Walton Drive, *Donevan Crescent
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*Regional Sanitary Sewer
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Heber Down Changes
• Overland Flow
– Ditch Inlets
• Add inlet controls (about 14)
– Catch Basins
• Add inlet controls (about 10)
– Protect Properties from Overland Flow
• Cassels Road from Montgomery to Heber Down
• Montgomery at Heber Down – north east corner
– Disconnect connections at controlled inlets
– Modifications are being checked by an outside
consultant
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Centre Street West & North Street
Changes
• Overland Flow
– Add inlet controls (4 Ditch Inlets on North
Street)
– Add inlet controls (2 double catch basins on
Centre Street West)
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Downey Drive
• Overland Flow
– Add inlet controls (2 double catch basins)
• Some at Carson Avenue
– Add inlet controls (2 ditch inlets in park)
– Seal lid on catch basin cover of maintenance
hole in overland flow route
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*Un-assumed Sites
• Bayberry Crescent is not assumed
– Inlet controls are recommended by the engineering consultant at
the double catch basins in sag in the overland flow route
• Helston Crescent is not assumed
– Inlet controls and modifications to the overland flow route and
pond outfall are recommended by the engineering consultant
– Modifications are being reviewed by an outside consultant
• Princeton Court is not assumed
– Inlet controls at the double catch basin at the end of the court in
the overland flow route will be recommended and required prior
to assumption
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**Private Sites
• Carnwith Condos is a private site
– Discussions with engineering consultant and
builder have emphasized the need for an inlet
control device
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Other Flooded Areas
July 23, 2008
• Isolated reports at
– Hanson Crescent
– Tremount Street
– Durham Street
– Kimberly Drive
– Ipswich Place
– Cassels Road East
– Underwood Drive
– Hatch Street
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Affected Areas – August 11, 2008
• Kilbride Drive
– Including Cahill Court, O’Malley Crescent
– Anderson and Taunton flooding
• Rosewood Court
• Walton Court
• *Annes Street (Regional Flooding Study)
– Tributary areas
• *Lupin Drive and surrounding streets
• *Walton Drive, Donevan Crescent
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Kilbride Changes
• Overland Flow
– Catch Basins
• Add inlet controls (about 2)
– Lower Overland Flow Route
• Cahill Court - Work with home owners in easement
• Kilbride – Lower path into park
• Anderson – Lower west boulevard at creek
• Other
– Debris proof pond outlets
– Remove indirectly connected downspout connections
• Modifications are being recommended by an
AECOM, an outside consultant
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Rosewood Court
Changes
• Overland Flow
– Add inlet controls (2 double catch basins)
• Other
– Remove indirectly connected downspout
connections
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Lupin Drive and surrounding area
• Overland Flow
– Follow recommendations of consultant’s
report
• Other
– Remove indirectly connected downspout
connections (57 locations)
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Michael Blvd and surrounding area
• Overland Flow
– Follow recommendations of consultant’s
report
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*Sanitary Sewer Flooding
Regional Reports
• Region is taking the lead on all other
August 11, 2008 flooding investigations
• Town is cooperating with any required
changes to storm sewer system
• Town is advising Region of locations
where overland flow may infiltrate sanitary
sewer through maintenance hole covers
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Other Flooded Areas
August 11, 2008
• Isolated reports at many other areas are
currently under review by the Region
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Other Causes of Basement
Flooding
• Grading
– Slopes can push water toward foundation
– Unprotected openings in foundation below flood elevations can
let surface water in
– Downspout flows towards foundation wall can flood weepers
– Blocked drainage swales can cause backyard ponding against
foundation
• Blocked weepers
– For example, Old clay tiles filled with roots or silt can prevent
drainage of ground water
• High water table, natural springs, extra depth basements
(below water table) can overwhelm foundation weepers
– Extra sump pumps with backup power may be required
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Causes of Basement Flooding
See www.iclr.org
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Typically the weeping tile connects to the storm sewer.
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Handbook for reducing
Basement flooding
•
•
What to look for in this diagram (shown in red)
This diagram shows a home that is at risk of basement flooding from
infiltration flooding, overland flooding and sewer backup. In this diagram:
– The cracks in the foundation wall and basement floor are unsealed.
– Downspouts are connected to the municipal sewer system or are discharging too
close to the foundation.
– The yard is improperly graded and sloped toward the home.
– The weeping tiles are connected to the sanitary sewer lateral.
– The weeping tiles have not been maintained and are damaged.
– There is no backwater valve in place.
– The sewer laterals have not been maintained, are cracked and have loose joints.
– The storm sewer lateral has not been severed and is prone to exfiltration.
– The backfill area beside the foundation wall is uncapped.
– The sewer cleanout is uncapped and unsealed.
– There is no window well cover in place.
•
•
by Institute for Catastrophic Loss Reduction 2009
www.iclr.org
Reproduced by permission.
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Methods of Connection Sewers
•
New construction (Typical in Whitby and Brooklin since 1980s)
– Storm sewer lateral - Front downspouts, weepers
– Sanitary sewer lateral – Floor drain, other plumbing
•
Some (Bradford Court, Lynde Shores)
– Foundation Collector lateral – weepers ONLY, no storm sewer lateral
– NO downspout connection permitted
•
Ditches (Newman, Maria, Gilbert, Henry, Cochrane, Heber Down, etc)
– Sanitary sewer – floor drain, weepers, etc
– NO downspout connection permitted
•
Current or Former Septic Tank
– Basement Floor Drain goes to sump pump
•
Former Sump Pump
–
–
–
–
Sump and weepers connected to storm sewer lateral
Backwater valve is now RECOMMENDED on storm sewer lateral
Downspout connection is not normally recommended
Floor Drain should be REDESIGNED to connect to sanitary sewer
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Other Things to Check
• Clear basement floor drain
– Seepage from walls or floor or leakage from
hot water tank or water in windows or other
openings should all drain to floor drain
– Ensure a clear path from all locations to floor
drain
– Basement floor drain is connected to sanitary
sewer
• Except Heber Down Crescent, Torian Avenue, Montgomery Avenue, North Street and all
houses that originally had sumps and septic systems.
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What Can Home Owners Do?
• Disconnect downspouts
– ALL Rear downspouts except for Townhouses
– Temporarily disconnect Front downspouts until your plumber verifies
that storm water from your roof cannot infiltrate to sanitary plumbing
– Downspouts connected to Sanitary Sewer must be disconnected –
contact Region
– Direct downspouts to splash pads away from house
• Protect Openings from surface drainage
– Use window wells
– Use sealed windows and doors near ground
• Slope patios and driveways away from your foundation (2% slope)
• Do not raise the grade along property line
– Leave a minimum 0.60 m (2 feet) buffer
– Remove obstacles
– Watch out for driveway widenings, walkways between house,
landscaping which have all been shown to cause basement flooding
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Downspout Disconnection
• Sanitary Sewer lateral has no capacity to
handle flows from downspouts
• Storm Sewer lateral can handle about ½ of
a roof and not more than 100 m² (1000 sf)
– Exception – all of a small townhouse roof
• Flows from downspouts can directly enter
basement under some conditions
– Through infiltration and direct or indirect
sanitary sewer connections
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If You Were Flooded
• Consider installing sewer backflow preventers on sewer line from
basement floor drain
• Disconnect your downspouts
– Cost is less than $15 per downspout
• Have your storm and sanitary sewer lines inspected by a plumber
– Sanitary can be inspected from basement cleanout
– Storm can be inspected from downspout connection to storm
• Town (storm) and Region (sanitary) is responsible for blockages
outside of the property
– If your plumber finds this type of blockage, call us
• Home owner is responsible for blockages inside the property lines
• Clean out your foundation weepers
– May require a dig up to access weepers
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Sewer Backflow Preventer
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No Plumbing Permit Fee for
Installation*
• To encourage the proper installation of
backflow preventers
– Town will effectively waive Plumbing Permit
Fee
– *A grant equivalent to the cost of the plumbing
permit will be given at the time of application
– *Grant is only available for one year
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Warnings – Backflow Preventers
• Inside installation only effective at
preventing flooding from basement floor
drain
• Outside installation on storm sewer is
possible but not if floor drain and
foundation weepers connects to storm
sewer
• Improper or poorly maintained installation
may result in basement flooding
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Other Sources of Information
• City of Toronto – Wet Weather Flow
Management and other documents
– www.toronto.ca
• City of Edmonton – Homeowner’s Guide to
Flood Prevention
– www.edmonton.ca/for_residents/ForHousehol
ds/Homeowners_Guide.pdf
• Institute for Catastrophic Loss Reduction
– www.iclr.org
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Five Quick, Inexpensive Ways To
Get You Started
City of Edmonton
•
1 Plug the leaks.
– A ladder, silicone, and time are all you need to seal holes or cracks in your eaves
troughs, downspouts, extensions, sidewalks, patio and driveway.
•
2 Repair or replace downspout extensions.
– This might be a matter of simply putting down the extension that’s already there
or putting back the splash pad. Purchasing and installing extensions or splash
pads is inexpensive but very important in getting water away from foundation
walls.
•
3 Clean your eaves troughs and downspouts.
– The downspout extensions have little value if leaves, and other debris are
preventing water from getting down the downspout. A gloved hand (or garden
spade), ladder and garden hose are what you need to get the job done.
•
4 Backfill under steps and decks.
– This is often the weak spot in lot grading. Dirt and some shovel work is all it takes
to fill the depression and get the ground sloping downhill away from the house
again.
•
5 Top up sunken areas around the foundation.
– Ground around your basement settles over time. Raising that up with some dirt
and shovel work will re-establish a positive grade again at little or no cost.
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Contacts
• Town of Whitby Public Works
• Arthur Smith 905-430-4300 x 2227
• Antony Manoharan 905-430-4300 x 2346
• Emergency Sewer Backups
– Town Operations Centre 7:30 am to 4:00 pm
• 905-668-3437 (Storm related)
– Region Works Dept 8:00 am to 5:00 pm
• 905-668-7711 (Sanitary related)
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