Flooding Meeting
Monday July 20, 7:00 and 8:00pm
Westmount Public Library, London ON
Upon arrival residents were asked to include their contact information for follow up information and to be contacted by
staff regarding concerns related to recent storm events.
Speaker
Discussion
Virginia
Ridley
City
Councillor
Welcomed residents and introduced city staff.
John Braam
(include job
title)
Introduced staff team in attendance and provided an overview of the information to be
presented through a PowerPoint slide show.
Indicated June 23 flooding received similar rain intensity as Hurricane Hazel.
City wide the rain fell at a rate of 100mm/hour.
June 27 & 28 flooding was not as intense as June 23 rain fall.
June 27 & 28 was comparable to September 2014 rain fall.
John Lucas
(include job
title)
Displayed a ‘heat map’ – this map indicated where the most intense flooding occurred
throughout the City of London as reported by residents.
Apologized that due to current lack of resources the data that has been collected has not
yet been processed and analyzed as would typically happen.
Reviewed the normal City of London storm response plan.
Advised that, during the June 23 storm by the time the supervisor was at the first
location, the storm was done and the rain stopped. This presented issues with regard to
completing an inspection of the root cause of the flooding occurrence.
During Jun 27 & 28 storm, a call centre was set up to receive citizen calls who were
reporting property flooding conditions.
Some step a home owner should take when experiencing flooding include calling the
COL to report. Additionally a licenced plumber to evaluate the damage and possible
solutions (per the Basement Flooding Grant Program). The City does not share
information about flooded basements with insurance companies.
Environmental & Engineering Services uses the data received (calls) about flooding to
help make recommendations regarding infrastructure, including areas identified in need
of improvement. This info is reported to Council through Civic Works Committee.
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Discussed the 10 year plan with respect to sanitary/storm water sewer improvements.
Approx. $400 million is allocated to improve the sewer systems. The 10 year plan was
submitted with the most recent budget approvals (2015).
Advised that the Operations Division assists with the functionality of the sewers.
Sanitary sewers are to be flushed at least once every 2 years This removes any build up
that may be promoting flooding (grease build ups) and helps to identify problems such as
broken or damaged sections of sewer pipe.
Scott Mathers
(include job
title)
Reviewed the sewer system as it currently is in place.
Reviewed that there are several reasons why homes may experience flooding;
Advised that homes built prior to 1985 have the weeping tile that surround the home
(collecting rain water) connected to the sanitary sewer system underground. The
additional amount of rainwater entering the sanitary system puts additional pressure on
the system – this results in water (sanitary) backing up in peoples floor drains, basement
toilets etc.
Surface flooding also may have occurred – this could have been in the manner of water
coming in through window wells, cracks in the foundation, etc. Lot grading may assist
with the correction of this type of flooding.
A large portion of Ward 10’s sanitary system drains to a central pumping station and
then to the Greenway Wastewater Treatment Plant.
Briefly reviewed the Basement Flooding Grant Program and advised that homeowners
could receive up to 75% funding, should they follow through with this program.
In the Westmount area there are two storm water ponds (Pincombe Ponds) – one
collects the majority of the water run-off from the commercial plaza and the other
collects the majority of the water run-off from the residential areas. A large portion of
the Westmount area north of Southdale Road drains to the Pincombe drain.
The Picombe drain has always been considered a flood plain area by the Conservation
Authority and is susceptible to frequent flooding.
The way in which the storm and sanitary sewers flow or run was also reviewed.
John Lucas
Advised that the data that has been collected has not yet been analyzed, due to the work
stoppage (strike) as staff resources are not available to complete this large task.
Reviewed areas that the City of London can improve with communication to residents on
how to maintain and prevent a flood free home.
This includes the removal of weeping tile and installation of a Backflow Valve and/or a
Sump Pump.
Advised that a residential area of the city recently underwent a pilot project where the
entire community was removed from weeping tile and a backflow valve installed. The
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results of this pilot project were very positive – no flooding was found in these homes
with the most recent storms.
An inspection of the PVC pipe may be of benefit as this pipe could be blocked with debris
or even tree roots, which in turn could be assisting with the flooding.
Questions and
comments that
were brought
forward
What do Pumping Stations do?
Pumping stations collect sewer water from a low point and pump it through a
pressurized pipe to another location. Large portions of the Westmount area are collected
at the Westmount pumping station and pumped to a sewer that drains the Greenway
Pollution Control Plant.
Was Greenway over stressed during the recent flooding?
There was stress on the Greenway plant and overflows to the Thames River did occur
during the storms. The stress at the plant did not cause the basement floodings.
There was a lot of lightening and electrical activity – could it be possible that a
pumping station was hit with lightening and shut off, subsequently stopping working?
City plants and pumping stations include backup generators that kick-in if a power
outage occurs. Our investigation of the storm impacts are still underway but it this point
it appears that the basement flooding experienced in Ward 10 was not related to the
functioning of the City’s pumping stations.
As engineers, what do you see that is creating these flooding issues?
Basement flooding can be caused in a number of ways. The most common form of
basement flooding in Ward 10 is described below.
Subdivisions approved prior to 1985 have their weeping tiles connected into the
sanitary system (See Figure A). If you do not have a sump pump in your
basement, your weeping tile are likely connected to the sanitary sewer. During
large storms rainwater from private properties enter the sanitary sewer system
through these weeping tile connections. The large quantity of water in the
sanitary sewers then cause backups to occur into the basements of homes
through floor drains, showers, sinks and toilets (See Figure D).
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If backflow valves are installed, what guarantee do we have that the flooding will stop
– to expand, if 100 homes are within the neighbourhood and only 50 of them install
the backflow valve, these are the residents that need a guarantee that flooding will not
occur.
There are two objectives of the current basement flooding program: reduce the risk of
flooding for the grant applicant and to benefit the overall community by reducing the
amount of rainwater in the sanitary system. The first objective is reached through the
installation of a backflow preventer at the home of the applicant. The second objective is
achieved by disconnecting the applicants weeping tiles from the sanitary sewer system.
Weeping tile disconnection from the sanitary sewer and backwater valve installation go
hand in hand. If weeping tile are not disconnected, a flooding risk still exists as sewer
can back up into the weeping tile systems which could push water through your
foundation; resulting in water seepage into your basement.
There are many different causes of basement flooding and although the installation of a
backflow preventer will reduce the risk of a basement flooding there is not guarantee
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that the home will not be flooded in the future. Like any piece of safety equipment,
backflow preventers must be inspected and maintained regularly to ensure that they
function when you need them.
Is a certificate required from a plumber before the backflow valve is installed?
Plumbers need to get a building permit to install a backwater valve and have it inspected
by a plumbing inspector. This will ensure that it is installed properly according to Ontario
Building Code.
If a home has a backflow valve and a sump pump, why is flooding still experienced?
Without more specific information, it is impossible to know. With proper maintenance,
sump pumps and backwater valves do work. Every home in a post 1985 subdivision has a
sump pump and there are hundreds of instances where backwater valves have
functioned properly. If you have been flooded after installing a backflow preventers
installed please contact the City (519-661-2500 x 5854)
We reported an issue during the Sept 2014 flooding, however no assessment was
completed by staff then. The strike was not in effect then – what happened to my
assessment?
Most basement flooding issues can be addressed over the phone but staff are available
to meet onsite if issue cannot be resolved on the phone. To discuss your flooding issue,
please contact the City at 519-661-2500 x5854.
On the heat map it showed a hot spot, which included my home. When will this be
addressed and when does the 10 year plan take effect?
The City’s capital budget is a 10-year plan for improvements to infrastructure city-wide.
Sewer replacement projects will not change your basement flooding risk. The primary
cause of basement flooding in Ward 10 was a result of the sanitary sewer becoming
overloaded with too much storm water from the numerous weeping tile connections
from each home. In this circumstance, the age of the sewer is not the cause. At this
time, the only way to reduce your risk of a future flooding event is to disconnect your
weeping tile from the sanitary sewer and install a backwater valve.
If backflow valves are installed, will relief be felt community or city wide?
In order to reduce the risk of flooding in your home, the weeping tile must be
disconnected from the sanitary sewer in addition to the installation of a backflow valve.
This will help protect your home from a future flooding event. To achieve a community
impact, many, many weeping tiles must be disconnected from the sanitary to remove a
sufficient amount of water to prevent the sewer from backing up.
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With respect to storm water ponds, what is the plan for the area south of Southdale Rd
W – will we see ponds in this area as well?
There are currently drain improvements four additional stormwater ponds planned
south of Southdale Road. In most cases the basement floodings in Ward 10 were caused
by backups in the sanitary sewer system and not the storm sewer system; therefore
improvements to the storm system (building ponds and cleaning out the downstream
channel) will not reduce the likelihood of future basement floodings.
My house was built after 1985 and has no weeping tile – how did my house flood?
All homes are constructed with weeping tile. If you do not have a sump pump in your
basement, your weeping tile will be connected to the sanitary sewer. Subdivisions
approved before 1985 will include houses built after 1985. It is not uncommon to own a
home built in the mid to late 80s with weeping tiles connected to the sanitary sewer.
If you live in a much newer home, it is likely that you were flooded when the sanitary
sewer backed up as shown in Figure D below. This backup occurred when a large
amount of storm water entered the sanitary sewer network from the weeping tiles of
other homes in your area. These homes would have been constructed in developments
approved after 1985.
With respect to the grants that are available, will engineers take into consideration the
lot grading and include some of the costs associated with the correction of lot grading
into the funding that is available?
Lot grading changes are not currently part of the grant program for residential
properties. Please visit the City’s Basement Flooding Grant Program webpage for more
information on the Grant Program.
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I have contacted Risk Management to submit a claim. They have refused the claim
even after improvements have been completed on my home (for ex. Backflow valve
installation) – why?
The City is responsible for ensuring that the sewer system is maintained on a regular
basis. Basement flooding most often occurs due to the sewer system being overwhelmed
by rainwater from the weeping tiles of private homes. Unless residents undertake work
on their own homes, the risk of future basement flooding will continue. As the severity
and frequency of inclement weather increases, municipal sewers will increasingly exceed
the limits of earlier time designs. Unfortunately there is no immediate remedy to the
infrastructure short comings. The system is designed for capacity considered acceptable
based on expected conditions at the time of construction.
The infrastructure in my area was replaced about 5 years ago, since then we have
experienced flooding. Prior to the infrastructure being replaced, we did not experience
any flooding.
The primary cause of basement flooding in Ward 10 was a result of the sanitary sewer
becoming overloaded with too much storm water from the numerous weeping tile
connections from each home. In this circumstance, the age of the sewer is not the
cause. So, the infrastructure replacement 5 years ago did not eliminate the weeping tile
connections to the sanitary sewer, so your basement flooding risk is still present.
Regarding frequency of flooding, intense storms hit different areas in different years. As
the timing, size, and location of storms are unpredictable, it is not possible to predict
where or how often a flooding will affect your home. You could go years without being
affected by a storm and then be flooded twice in one year. If you are at risk of basement
flooding, the City urges you take advantage of the grant program.
The City of London is continuing to build and put pressure on these out dated
infrastructure systems.
When new development occurs within an area, it is paramount to the City that there is
no impact to existing homeowners. As shown during the presentation the new
commercial area along Wonderland discharges directly to the Westmount pumping
station and does not contribute to the basement flooding that occurred throughout the
Ward 10 area. The new residential area south of Southdale Road drains south and is
pumped to an area that was not impacted by basement flooding.
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