AREA 19 STORMWATER
RUNOFF CONTROL AND
INVESTIGATION OF
CHRONIC BASEMENT
FLOODING CLASS
ENVIRONMENTAL
ASSESSMENT – PROJECT
FILE – EXECUTIVE
SUMMARY
Prepared for:
City of Toronto
Prepared by:
Stantec Consulting Ltd.
August 8, 2014
AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT – PROJECT FILE –
EXECUTIVE SUMMARY
August 8, 2014
EXECUTIVE SUMMARY
1.0
BACKGROUND, PURPOSE AND OBJECTIVES
On August 19, 2005, the City received a record amount of rainfall that resulted in
widespread surface and basement flooding. The majority of basement flooding
occurred north of Highway 401, where over 4,200 basement flooding complaints
were reported. As a result, the City approved a Basement Flooding Work Plan
requiring a comprehensive engineering review be undertaken to address
chronic basement flooding problems in over 30 separate study areas located
across the City. The subject area in this study is identified as Area 19 in the Work
Plan.
The objectives of this study are to assess the existing major and minor stormwater
systems as well as the sanitary system to identify the potential causes of
basement and surface flooding, and to identify solutions that meet the elevated
level of service criteria approved in the City’s 2006 Work Plan to reduce the risk
of future flooding. Based upon the Work Plan, the basement flooding protection
level has been set to the equivalent of the May 12, 2000 storm event for the
sanitary system, and the 100-year design storm, where feasible, for the storm
minor and major systems. In addition, the study will address stormwater runoff
quality and develop solutions to reduce the adverse effects of stormwater
entering watercourses in the study area, in order to help meet long-term water
quality objectives of the City’s Wet Weather Flow Management Master Plan
(WWFMP).
2.0
STUDY AREA CHARACTERISTICS
Study Area 19 is located in the central portion of the City and covers part of
Wards 15 and 16 completely within North York District. The area is bisected by
Sheppard Avenue and Bathurst Street, and is roughly bounded by Highway 401
to the south, Finch Avenue to the north, Dufferin Street/Allen Road to the west,
and the West Don River to the east, and covers an area of approximately 836
hectares (see Figure ES.1). There are approximately 7,056 properties
representing a population of 26,110 within Study Area 19. The predominant land
use in the study area is residential, comprising approximately 50% of the overall
land coverage. There is also a significant institutional presence (~14%) and
some limited commercial and industrial presence (~5%). Road right-of-ways
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT – PROJECT FILE –
EXECUTIVE SUMMARY
August 8, 2014
Figure ES-1 Study Area 19
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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EXECUTIVE SUMMARY
August 8, 2014
make up a large percentage of the overall area (>25%) due to the presence of
the Highway 401, the Allen Road, and associated on-ramps in the southern
portion of the Study Area.
Development of the area occurred mainly in the 1950s and 1960s with no
significant development having been implemented since 1980. Growth is
projected in the Downsview Area Secondary Plan (DASP) along with
intensification along the arterial roads of Sheppard Avenue, Wilson Avenue,
Bathurst Street, and Wilson Heights Avenue. Similar to other areas in the former
City of North York, a separate drainage system was constructed. The sanitary
sewer network, with a total length of approximately 88 km, collects
flows from several sub-trunks which discharge easterly to the West Don Trunk
Sewer, which ultimately discharges to the Ashbridges Bay Wastewater Treatment
Plant. Stormwater is collected from 22 separate sewersheds and flows into the
storm sewer systems having a total length of over 116 km, with the majority
discharging into the West Don River watercourse. The southwestern portion of
the study area drains via Area 16 to the Black Creek watershed.
2.1
EXISTING CONDITIONS
Since the development of the area, basement flooding has occurred
periodically in response to extreme storms throughout the years, including the
major events of August 1986, May 2000, July 2002, August 2005, and more
recently in July 2013.
Field investigation and inspection were conducted to identify the specific
characteristics of the study area and its drainage systems. A review was also
undertaken of the existing natural and socio-economic environments, as well as
a review of available data sources and any previous studies.
Hydrologic-hydraulic simulation models of the sanitary system and the storm
major and minor systems were developed. The models were used as a tool to
assess the hydraulic performance of the existing drainage systems, to identify
their current performance level, determine probable causes of deficiencies, and
to develop the potential remedial measures for the basement and surface
flooding issues in the study area. Annual runoff water quality simulations were
also performed for storm outfalls to gauge the pollutant reduction potential with
implementation of source, conveyance and end-of-pipe control measures in
the area (excluding the area tributary to the recently constructed Earl Bales Park
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT – PROJECT FILE –
EXECUTIVE SUMMARY
August 8, 2014
stormwater management pond facility that was evaluated in a separate 2006
EA).
Based on the analysis completed, it was determined that the sanitary and storm
drainage systems generally have the hydraulic capacity to convey peak flows
resulting from everyday rainfall events (less than the 5-year event).
3.0
STUDY PROCESS AND CONSULTATION
The study has complied with the requirements for a Schedule ‘B’ project under
the Municipal Class Environmental Assessment (Class EA) process. A Class EA
applies to a group of projects that are permitted under the Environmental
Assessment Act as long as they follow the approved planning process. The
specific requirements depend on the type and complexity of the project as well
as the significance of potential environmental impacts. Agreements made or
commitments given the proponent to affected agencies or the public must be
followed through and implemented. If an affected agency or the public has a
concern that cannot be resolved by discussion and negotiation with the
proponent, they can request a Part II Order which may elevate Schedule B and
C projects to an Individual EA, or for Schedule B projects to become elevated to
a Schedule C project.
The residents of Area 19 have experienced surface and/or basement flooding
during extreme wet weather conditions. The project assesses the major and
minor storm drainage systems and the sanitary sewer system to identify the
causes, mechanisms and impacts of surface and basement flooding and
receiving water quality degradation. The result is the development of
comprehensive flooding remediation plans that best meet the target level of
service criteria of the City. It is anticipated that all of the sewer and surface
drainage system remediation works will be constructed within the existing road
allowance or on City property. Accordingly, this project follows a Schedule B
process.
This Project File document is intended as a summary report, documenting
Phase1 and 2 of the Class EA for this Schedule B project. The Project File is
presented for the 30-day public and agency review period.
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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EXECUTIVE SUMMARY
August 8, 2014
3.1
AGENCY AND PUBLIC CONSULTATION
A comprehensive consultation program was conducted with the following
components:
•
A Notice of Study Commencement mailed to approximately 19,000
residents and business owners within the boundaries of three study areas
(17, 18 and 19).
•
A mailing list was created and maintained over the course of the study
that included review agency contacts, local interest groups, ratepayer
associations, and all members of the public who requested to be added
to the list.
•
Two Public Information Centre (PIC) events were held, consisting of a
drop-in centre with display panels and provided an opportunity for the
public to speak with City and consultant staff. The PICs were held on July
4/5, 2012 and PIC#2 on July 9, 2013.
•
Councillor Briefings were held with staff to present and collect feedback
on the proposed solutions.
•
Throughout the duration of the study, staff from the TRCA and the City’s
internal divisions (Parks, Forestry and Recreation, Development Services,
District Operations, Engineering and Construction Services) were
consulted throughout the screening, development and evaluation of
alternatives.
•
The City maintained a project website with background information,
meeting materials, project updates and staff contact information.
4.0
EVALUATION OF ALTERNATIVES
4.1
METHODOLOGY
There are several possible remediation measures to control incidents of surface
and basement flooding, and to mitigate impacts of stormwater runoff on
receiving water quality. The methodology to develop and evaluate viable
alternatives included a long-list screening of remedial measures, followed by
development of an overall solution ‘strategy’ comprising a combination of shortmp m:\active\160700405_swm_basement_flooding\preliminary\report\area 19\project
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT – PROJECT FILE –
EXECUTIVE SUMMARY
August 8, 2014
listed remedial measures. The evaluation was undertaken using a standard pairwise weighting process where each strategy is evaluated with respect to a
number of environmental, social and economic criteria (developed with input
from PIC#1) and assigned a rating. The ratings were subsequently multiplied by
the criteria weightings and summed for each alternative to provide a total
weighted score. Given the number of constraints associated with siting of locallevel solutions and the size and interconnectivity of the solution set, an
additional evaluation of individual solutions was performed only where feasible
alternative alignments existed. These locations were further evaluated in a
similar manner to the strategies however with a risk-based approach to
determine those with the least impact to the triple-bottom-line (environmental,
social, and economic environments).
4.2
DEVELOPMENT AND EVALUATION OF ALTERNATIVES
4.2.1 Solution Strategies
Following the principles of the WWFMP, overall strategies were developed with
the hierarchical approach of source, conveyance, and end-of-pipe controls.
Within the strategies, high-level alternatives were derived to capture variables in
the potential make-up of the solution sets. The strategies and their alternatives
are discussed briefly as follows:
Strategy 1: Aggressive Source Control Implementation. Through application of
by-law creation/enforcement, target aggressive implementation of
source controls to that of the WWFMP ‘Enhanced’ levels in the
immediate term.
Strategy 2: Conveyance Controls. Implement conveyance infrastructure
improvements alone to improve system capacity. One alternative
is to consider implementation within the municipal road allowance
alone while a secondary alternative would consider acquisition,
either through easements or property purchase, for conveyance
through private lands.
Strategy 3: Storage Facilities. Implement storage infrastructure improvements
alone to relieve and optimize existing system capacity. Four
alternative considerations include application of in-line versus endof-pipe storage, on public versus public and private lands.
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Strategy 4: Integrated Water Quality Solutions with Source, Conveyance & EOP
Controls. Incorporate Strategies 1 through 3 in various
combinations. Alternative considerations include application of the
creation of new outfalls as part of the solution, and implementation
of dedicated interceptor sewers for diversion to centralized end-ofpipe water quality treatment facilities.
Strategy 5: Do Nothing. Maintain the Status Quo in system
performance/operation, with continued maintenance and asset
renewal programs, but no specific flood/water quality solutions.
The following is a synopsis of the evaluation:
•
Implementation of source controls alone will not meet the objectives of
flood control, and will greatly burden the public through reliance on
private improvement measures.
•
Implementation of conveyance controls alone will not meet water quality
or no-net increase to sanitary trunk sewer objectives, and will result in
larger social and environmental impacts due to the increased length
requirements of solutions, and the larger flow contributions to the
receiving watercourse.
•
Implementation of storage controls alone will partially meet the overall
objectives, at the expense of increased short and long-term maintenance
costs, greater impact to open space/natural environment due to footprint
requirements, and higher degree of technical difficulty to design/operate.
•
An integrated strategy combining opportunistic implementation of source
controls, conveyance controls, and end-of-pipe measures provides the
most flexibility for meeting the water quality and flood control objectives,
and optimizing the natural, social and economic impacts of required
projects.
•
A dedicated interceptor sewer for water quality treatment at centralized
end-of-pipe treatment facilities causes too great an environmental and
social impact at greater cost, given the sensitive natural environment
within the West Don floodplain, and need for space not owned by the
City.
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•
The Do Nothing alternative cannot meet the water quality and flood
control objectives, and would serve to continue degradation of water
quality in the receiving watercourses and the level of service experienced
in the study area.
•
Preference for implementation on municipally-owned property since this
involves lower approval needs, less cost, and greater control of
implementation scheduling; however, easement or land acquisition
should be investigated where feasible.
4.2.2 Project-Level Alignments
4.2.2.1 Sanitary System
SAN-19-01/02: Garratt Boulevard & Wilson Avenue
Two alternatives were reviewed to reduce the amount of surcharge occurring in
the Wilson Avenue sewer. Alternative 1: providing in-line storage to reduce the
amount of flow to Wilson Avenue and Alternative 2: replacing and upsizing the
entire Wilson Avenue system to lower surcharge amounts. The extent of
upgrades associated with Alt. 2 is much larger than the relatively local
improvement works associated with two storage facilities, therefore is more
expensive and has a greater social impact. Hence, Alt. 1 is preferred.
SAN-19-03/04: Westgate Boulevard / Ravine
To relieve the system surcharging to the surface down the Westgate Ravine
through to the discharge point to the West Don Trunk, in-line underground
storage (Alt. 1) and conveyance (Alt. 2) were reviewed. A large deep storage
tank at the cul-de-sac/entrance pathway to the ravine would control peak
flows to the trunk and reduce environmental impact to the ravine. While it does
not eliminate an upgrade (twinning) of the existing sanitary after the confluence
with the Timberlane sewer in the valley, it avoids the need to replace the
recently constructed sanitary sewer bypass sewers associated with the Earl Bales
Pond project. Alt. 2 increases flow to the trunk, has greater environmental
disturbance downslope and in the valley, and does not avoid the EBP upgrades.
Therefore, Alt. 2 is not preferred.
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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SAN-19-06/13: Bathurst St./ Ellison Ave./ Timberlane Ravine
Similar to SAN-19-03/04, this adjacent and connecting project is upstream of the
Westgate Ravine and works in tandem with the solution. Alt. 1 comprises a
combination of two in-line storage facilities: optimization of the existing Ellison
Ave. super-pipe by way of orifice control, and through new pipe on Timberlane
Avenue upstream of the ravine. Both serve to eliminate the need for major
disturbance that conveyance would require through the wooded ravine. While
more costly, the reduced impact to the downstream trunk and natural features
deems Alt. 1 more preferred than the conveyance Alt. 2.
SAN-19-09/10/15: Searle Ave./Hove St.
Alt. 1 provides a combination of upstream diversion (Searle and Maxwell) and
in-line passive storage on Hove St. to control the local hydraulic grade line on
Searle and further upstream at Waterloo Ave. where a flow split east to Bathurst
exists. The length of disturbance is much shorter than Alt. 2, which is
conveyance upgrades on Searle Ave., Hove St., and Bathurst Street (resulting
from higher HGL at flow split). In addition, the need for construction on Bathurst
Street increases traffic / commuter impacts. Therefore, Alt. 1 is preferred.
SAN-19-11: Overbrook Place
The difference between Alt. 1 and 2 is minor. Alt. 1 provides a combination of
local sewer upgrade along with in-line storage while Alt. 1 has additional
conveyance instead of storage. The resulting cost is similar; however, there is
additional traffic/access disruption and more conflicts requiring resolution for Alt.
2, therefore Alt. 1 is preferred.
4.2.2.2 Storm Drainage System
STM-19-01: Bayhampton Court
The small drainage area and sewer system at the north end of Area 19 has two
potential alternatives to relieve the trapped overland flow. Alt. 1 upgrades the
deficient storm sewers including through a short portion of wooded area while
Alt. 2 has a dedicated major system pipe to an underground storage that
avoids the wooded area. The reduced risk of less potential for tree loss is outweighed by the increased cost, long-term O&M burden, and greater
disturbance to recreational space. Alternative 1 is preferred.
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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STM-19-02: Purdon Drive
Trapped overland low point on Purdon can be conveyed by pipe increase
along its current alignment which traverses between two houses to an
upgraded outfall (Alt. 1), or by a longer route that avoids construction between
properties yet requires the construction of new outfall at Garthdale Park. The
shorter route of Alt. 1 is less disruptive, especially with trenchless methods
employed between the properties, at the expense of increased
design/constructability. Both alternatives require some disturbance to the
wooded area, however, Alt. 1 does not require construction of a new outfall.
Both options can be coordinated with watercourse rehabilitation efforts to
mitigate construction disturbances associated with the outfall. Should trenchless
construction be suitable at the detailed design stage, then Alternative 1 is
preferred, however Alt. 2 remains a feasible fall back.
STM-19-03: Arlstan Dr.
This project is in tandem with STM-19-02, whereby the trapped low point on
Arlstan is either conveyed by short pipe upgrade along the existing route via
easement between homes to an upgraded Purdon system (Alt. 1), or by a much
longer route via Blue Forest Dr. to the new Garthdale Park storm outlet.
Following the same logic as STM-19-02, the shorter and therefore cheaper and
less disruptive approach via more involved construction is preferred; however,
Alt. 2 remains a closely scored viable approach.
STM-19-06/07/09/12: Overbrook Place/Maxwell St.
Major system control can be provided by a single large storage facility (Alt. 1), or
by two smaller and spatially separated storage facilities, plus associated
reduction in connecting conveyance infrastructure. Alt. 1 is favoured due to
being more economical (one tank is easier to maintain than two), and based
on concerns from PF&R regarding high impact to recreational function of Irving
W. Chapley Park.
STM-19-44: Allen Rd. N. of Sheppard Ave.
Trapped overland flow paths on Allen Rd. are controlled via major system
storage with minor system upgrades (Alt. 1) or major system conveyance that
extends almost double the distance along Allen to south of Sheppard Ave. W
(Alt. 2). Costs are comparable, however the reduced traffic/environmental
disturbance and inability to renew existing storm infrastructure favours Alt. 1.
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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STM-19-46/47: Banting Ave./Reiner Rd.
Trapped overland low points on Reiner and Banting are controlled in Alt. 1 by a
combination of surface diversion to dry pond in Banting Park, along with
underground storage in the south portion of Banting Park. Alt. 2 requires the
extension of major system conveyance of both low points to the Wilson Heights
Boulevard connection to the deep trunk. PF&R and the public identified some
rehabilitation / bioretention efforts in Banting Park, however the footprint of the
facilities remain small and can avoid disturbance. Greater social impacts for
traffic and construction associated with the longer Alt. 2 favour the cheaper Alt.
1.
STM-19-51: Cocksfield / Yeomans / Alexis Low Points
Central trapped overland low points can be controlled by linear storage in Earl
Bales Park, with conveyance by two alternatives. Alt. 1 conveys the subject low
points via dedicated major system pipe from Cocksfield via
Maxwell/Harlock/Alexis. Alt. 2 conveys the Cocksfield and Alexis/Harlock low
point via Sheppard Avenue to the existing sewer new the outfall at the bridge
crossing the West Don River, in addition to conveying the Alexis/Yeomans low
point via Alexis to a smaller storage in Earl Bales Park. The length of disturbance
to a major commuter/arterial road and the constructability challenges
(trenchless / major conflicts) outweighs the increased cost associated with the
shorter, therefore preferred Alt. 1.
STM-19-40/67/68: Wilson Ave. E./Delhi Ave.
To relieve the trapped overland flow that is overwhelming the existing storm
trunk crossing Hwy. 401 at Bathurst St., two alternatives were developed. Alt. 1
creates a deep storm tunnel with alignment along Wilson Ave east to a new
outfall to the West Don River. Alt. 2 uses several underground storage tanks
located throughout the system to control flows to the existing storm trunk. Alt. 1
involves a high degree of constructability risks associated with tunneling,
however the trenchless approach reduces the traffic disturbance. Impacts of a
new outfall were discussed with TRCA, and it was demonstrated that flows to the
flood-sensitive Hoggs Hollow area would not increase beyond those assumed by
current floodplain hydrologic/hydraulic modeling, since no new drainage area
is directed to the watercourse.
Land availability for storage facilities is extremely limited in this area, and
therefore the need for siting of tanks on institutional properties (Toronto Public
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Library parking lot, Summit Heights Public School) was needed. These properties
would require additional consultation for suitability, and initial feedback from the
TDSB indicated a high level of uncertainty with property availability. This, in
addition to the higher cost and impact to open space render Alt. 1 as preferred.
Model and Faith Avenue
Due to concerns of residents on Model and Faith Avenues in the aftermath of
the July 8, 2013 flooding, additional analysis was conducted on the collection
system including CCTV inspection and fog-testing. In addition, supplemental
sanitary model calibration was undertaken to compare against the reported
flood complaints observed from the extreme July 8 event. The CCTV inspection
of the sanitary found no signs of blockage or structural issues, and the fog-testing
revealed one flat roof contribution and potential foundation drain/rear patio
drain connections to the sanitary on Model and Faith Ave. Testing of the storm
system revealed no cross-connections. The updated hydraulic model runs
demonstrated that the local contributions to the Faith and Model sanitary were
not the cause of local flooding. Therefore, in addition to promoting home
isolation measures on the private side, including foundation drain disconnection
to sump pumps and properly connected backflow valves on the sanitary
laterals, the downstream improvements to the sanitary system and proposed
storm drainage improvements on Model/Wilson Heights Blvd. will help reduce
flood risk as per the City’s enhanced design criteria. Sanitary manhole lids at
low points will also be sealed to reduce inflow to the sanitary sewer.
4.3
PREFERRED SOLUTION
Based on the evaluation of the alternative strategies and project-level
alignment/siting scoring, Alternative 4 was selected as the preferred approach.
At the project-level, the preferred siting alignments have also been selected
based on a risk-based evaluation, grouped as Alternative 1. To help achieve
the target level of protection against surface and basement flooding, it has
been determined that upgrades to the existing drainage systems are necessary.
Figure ES.2 presents the recommended improvement works to help address the
flooding problem in Study Area 19, and improve the runoff water quality to the
West Don River.
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AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
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Figure ES-2 Recommended Solutions
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5.0
CONCLUSIONS AND RECOMMENDED SOLUTIONS
To help achieve the target level of protection against surface and basement
flooding, it has been determined that upgrades to the existing drainage systems
are necessary. The estimated 50-year life-cycle cost of these works is $237.7
million (2013 Canadian dollars), including engineering and contingencies but
excluding taxes.
The following conclusions can be drawn from the completion of this study:
•
The historic flow monitoring program was useful in the
calibration/verification of the hydrologic/ hydraulic simulation models for
the sanitary and storm sewers; however, the storm events recorded were
limited in severity and thus extrapolation of parameters to mimic extreme
storm event response was required using best engineering judgment.
•
Infiltration and inflow experienced in the monitored sanitary sewersheds is
typical for the vintage of the infrastructure (1950-1970s) with a large
degree of connected foundation drains. As part of the detailed design
process, opportunities for pipe/manhole rehabilitation and/or private
property disconnection measures should be further investigated.
•
The main causes of basement and surface flooding include overloading
of storm sewers, surcharge of sanitary sewers caused by excess inflow and
infiltration and pipe bottlenecks, lack of a continuous major system,
trapped overland flow paths causing surface flooding, pockets of high
groundwater table, and blockage in sewers and street catchbasins.
•
Source control measures alone will not significantly reduce
basement/surface flooding (approximately 13% reduction in annual
outflow volume), however, will contribute to the improvement of water
quality of the receiving West Don River.
•
The preferred remedial measures consist of a combination of source
control measures, conveyance improvements, and storage elements in
the storm and sanitary collection systems.
•
With the implementation of the preferred sanitary remedial measures, the
sanitary sewer system can safely convey the May 12, 2000 design storm
event under 2031 anticipated population growth (including the
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Downsview Area Secondary Plan), within City criteria with no net increase
to peak flows received in the West Don Sanitary Trunk Sewer.
•
With the implementation of the preferred storm remedial measures, the
storm drainage system can convey both the major and minor systems
during the 100-year design storm within City criteria.
•
The storm capacity improvement measures including the new outfalls, will
not alter the existing floodplain in the sensitive Hogs Hollow area, since the
proposed storage measures act to decrease peak flow to the existing
outfalls, and no additional flow from other drainage areas has been
diverted to the river.
•
In addition to the existing Earl Bales Park stormwater management water
quality pond, there exists one additional opportunity for an end-of-pipe
facility downslope of Maxwell Park. Further consultation with the City and
TRCA is required to confirm feasibility of this location, as it has been
recommended that the site remain undisturbed and in situ until the
proposed impact is cleared of any further archaeological concerns.
•
With the application of enhanced source controls, conveyance controls
and the Maxwell end-of-pipe facility, the collective annual pollutant
reduction from outfalls not discharging to Earl Bales Park in Area 19 is 26%
TSS, 23% Total Phosphorus, 23% Copper, and 21% E. Coli. These measures
along with the Earl Bales facility and implementation of the
recommendations throughout the Don Watershed, will help meet the
objectives of the WWFMP.
•
The recommended improvement works to help address the flooding
problem in Study Area 19 is estimated at a capital cost of $195.6 million
(2013 Canadian dollars), including project delivery allowance and
contingencies, excluding taxes.
•
The recommended solutions within Parks and Open Spaces may affect
potential archaeological sites, therefore a Stage 2 Assessment is required
for these projects as outlined in the Conceptual Designs. All other projects
within municipal right-of-ways do not require Stage 2 works.
•
The Schedule ‘B’ Class EA process has been fulfilled through public
consultation including two PICs, agency consultation, and the submission
of this project file document.
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5.15
AREA 19 STORMWATER RUNOFF CONTROL AND INVESTIGATION OF CHRONIC
BASEMENT FLOODING CLASS ENVIRONMENTAL ASSESSMENT – PROJECT FILE –
EXECUTIVE SUMMARY
August 8, 2014
The following recommendations are made with respect to this study:
•
City to proceed with short-term local measures including sealing of
sanitary maintenance hole covers at low points in the road,
implementation of inlet control devices and overland diversions where
sufficient major system conveyance exists, continued promotion of the
residential roof downspout disconnection program, and continuation of
the City’s infiltration and inflow reduction and operations and
maintenance programs.
•
City to continue promoting the Basement Flooding Protection Subsidy
Program and the Fat, Oils and Grease public education initiatives.
Implementation of the measures included in this program will provide
protection to most residences and will enhance the performance and
level of protection provided by the remedial measures in the preferred
alternative.
•
City to proceed to detailed design of the preferred remediation measures
and commence implementation as capital budget permits. Liaison with
all review and approval agencies and the public to be conducted as
part of the design process.
•
Continued monitoring of rainfall-runoff response across the City, including
review and analysis of new basement and/or surface flooding complaints.
•
Investigate reconfiguration options of storm outfalls to reduce sediment
build-up and blockage.
•
The Maxwell Park siting opportunity for a stormwater management water
quality facility should be investigated further with the TRCA to determine if
the impact of the facility footprint can be cleared of any further
archaeological concerns.
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