proposed 59-71 mutual street residential development...final report project name: 59-71 mutual...
TRANSCRIPT
• Proposed 59-71 Mutual Street
Residential Development
STORMWATER MANAGEMENT REPORT
Type of Document Final Report
Project Name 59-71 Mutual Street Residential Development
Project Number BRM-00605384-A Prepared By:
exp 1595 Clark Boulevard Brampton, ON L6T 4V1 Canada Date Submitted December 03, 2015
59-71 MUTUAL STREET STORMWATER MANAGEMENT REPORT
Type of Document:
Final Report
Project Name:
59-71 Mutual Street Residential Development
Project Number:
BRM-00605384-A
exp Services Inc. 1595 Clark Blvd. Brampton, Ontario L6T 4V1 Canada T: 905-793.9800 F: 905-793.0641 www.exp.com
Murray Thompson, P. Eng. Project Manager Infrastructure Division
Bey Husika, P. Eng. Senior Associate, ICI Lead Infrastructure Division
Date Submitted:
December 03, 2015
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
STORM
CONNECTION INTO
EXIST. STORM
SEWER
EXISTING 2 YEAR
STORM - PRE
DEVELOPMENT
FLOW
(m3/sec.)
CITY MANDATED
ALLOWABLE
RELEASE RATE -
POST
DEVELOPMENT
(m3/sec.)
RELEASE RATE
WITH ORIFICE
PIPE or PLATE -
POST
DEVELOPMENT
(m3/sec.)
REQUIRED ON-
SITE STORAGE
- 100 YEAR POST
DEVELOPMENT
STORM
(m3)
AVAILABLE ON-
SITE STORAGE
- 100 YEAR POST
DEVELOPMENT
STORM
(m3)
Existing 375 dia.
storm sewer0.024 0.013 n/a 26.45 33.75
SUMMARY OF CALCULATIONS
NOTES:
- THIS STORMWATER MANAGEMENT REPORT IS IN SUPPORT OF THE REZONING APPLICATION FOR THE
PROPOSED 59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT, CITY OF TORONTO
- AS PER THE CITY OF TORONTO WET WEATHER FLOW MANAGEMENT GUIDELINES 2006 - THE MODIFIED RATIONAL
METHOD USING CITY OF TORONTO IDF CURVES HAS BEEN USED TO CALCULATE RAINFALL VOLUME.
- THE TOTAL AREA OF THE DEVELOPMENT IS 0.106 Ha. THERE ARE NO EXTERNAL AREAS DRAINING ONTO THE
PROPERTY.
- THE SWM DESIGN IS BASED ON CONTROLLING THE 100 YEAR POST DEVELOPMENT STORM TO THE 2 YEAR PRE
DEVELOPMENT STORM.
- ROOF TOP CONTROL FLOW DRAINS AND ROOF TOP STORAGE HAVE NOT BEEN PROPOSED ON THIS PROJECT.
- A GREEN ROOF AND LANDSCAPED AREAS ON THE BUILDING PODIUM AND STREET TREES ARE INCLUDED IN THIS
DEVELOPMENT.THE GREEN ROOF AND LANDSCAPE COMPONENTS WITHIN THIS DEVELOPMENT ASSISTS IN THE
GOAL OF ABSORBING THE 5mm STORM STORM EVENT.
- ALL STORM WATER WILL BE CAPTURED BY PODIUM AREA DRAINS AND ROOF DRAINS AND FLOWS WILL BE
DIRECTED TO THE STORM DRAIN PIPES LOCATED WITHIN THE UNDERGROUND GARAGE. THE STORM DRAIN PIPES
WITHIN THE UNDERGROUND GARAGE WILL CONVEY AND DIRECT THE FLOWS TO A STORMWATER MANAGEMENT
CISTERN LOCATED WITHIN THE UNDERGROUND GARAGE. THE CISTERN WILL BE LOCATED MID FRONTAGE
AGAINST THE FOUNDATION WALL AT THE MUTUAL STREET PROPERTY LINE.
- DUE TO THE SHALLOW DEPTH OF COVER OF THE 375mm STORM SEWER ON MUTUAL STREET THE STORMWATER
MANAGEMENT CISTERN IS SITUATED LOWER THAN THE MUNICIPAL STORM SEWER AND A GRAVITY CONNECTION
IS NOT OBTAINABLE. THE CONTROLLED STORM WATER RELEASE FROM THE DEVELOPMENT WILL BE BY WAY OF
PUMPING WITH THE RELEASE NOT TO EXCEED 0.013 m3/sec. THE STORMWATER MANAGEMENT CISTERN HAS BEEN
SIZED TO PROVIDE THE REQUIRED STORM WATER QUANTITY CONTROL VOLUME. THE EMERGENCY OVERFLOW
FROM THE SWM CISTERN WILL FROM THE CISTERN MAINTENANCE ACCESS COVER.
- THERE ARE NO DRIVEWAYS, DROP OFF AREAS OR PARKING AREAS PROPOSED AND THE DEVELOPMENT ROOF
AND PODIUM FULLY ENCOMPASS THE ENTIRE PROPERTY. AS SUCH THE DEVELOPMENT IS CONSIDERED CLEAN.
NO ADDITIONAL MEASURES FOR QUALITY CONTROL ARE BEING RECOMMENDED. ALL PODIUM DRAINS AND ROOF
DRAINS WILL BE INSTALLED WITH SCREENS.
- CITY OF TORONTO REQUIRED STATEMENT; EXISTING DRAINAGE PATTERNS ON ADJACENT PROPERTIES SHALL NOT BE ALTERED AND STORMWATER RUNOFF FROM THE SUBJECT DEVELOPMENT SHALL NOT BE DIRECTED TO DRAIN ONTO ADJACENT PROPERTIES.
1
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
1
A PRE-DEVELOPMENT Hectares
0.064
0.045
0.000
0.000
0.000
0.000
0.000
0.109
B Hectares
0.076
0.000
0.000
0.000
0.030
0.000
0.000
0.106
Total Site Area
Green Roof =
Buildings (Row Houses) =
Building (Podium) =
Parking Areas, Driveways =
Landscaped Area =
NOTE: The area of the development site in the Post Development condition is reduced in size to 0.106 hectares due to
the transfer of property (0.03 hectares) to the City of Toronto for the widening of the rear Laneway.
External Contributing Area =
* Garage Driveway is under the Podium
Green Roof =
Roof Mechanical =
Total Site Area
Lawn Area =
Parking Areas, Driveways =
Roof Mechanical =
DEVELOPMENT AREA
Lawn Area =
Landscaped Area =
POST DEVELOPMENT
Reference Figure No. 1 - Site Location Plan, attached. This aerial photograph shows the existing property condition.
External Contributing Area =
Reference Drawing No. FIG-SWM-1, Stormwater Pre-Development Drainage Areas, attached.
Reference Drawing No. FIG-SWM-2, Stormwater Post-Development Drainage Areas, attached.
Reference Figure No. 2 - Development Concept, attached.
2
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
2
A
Drainage Area
Pervious Area
(C=0.25)
Hectares
Pervious Area
(C=0.45)
Hectares
Pervious Area
(C=0.60)
Hectares
Impervious Area
(C=0.90)
HectaresSubTotal A x C
Buildings (Row
Houses)nil nil nil 0.064 0.058
Parking areas and
Drivewaysnil nil nil 0.045 0.041
Total AxC 0.098
0.900
B POST DEVELOPMENT BUILT FORM = Combined Drainage Run-Off Co-efficent
Drainage Area
Pervious Area
(C=0.25)
Hectares
Pervious Area
(C=0.45)
Hectares
Pervious Area
(C=0.60)
Hectares
Impervious Area
(C=0.90)
HectaresSubTotal A x C
Building Podium nil nil nil 0.076 0.068
Parking Areas,
Drivewaysnil nil nil nil 0.000
Lawn Area nil nil nil nil 0.000
Landscaped Areas nil nil nil nil 0.000
Green Roof nil 0.03 nil nil 0.014
Roof Mechanical nil nil nil nil 0.000
Total AxC 0.082
Combined Drainage Run-Off Co-efficent 0.773
NOTE:
Combined Drainage Run-Off Co-efficent
PRE DEVELOPMENT BUILT FORM = Combined Drainage Run-Off Co-efficent
The proposed green roof within the new development provides soft areas for absorption, evaporation and
evapotranspiration where none presently exists. With the addition of the green roof the Pre Development
condition is improved on, with the Post Development runoff co-efficient being reduced from 0.900 down to
0.773
COMPARISON BETWEEN PRE AND POST DEVELOPMENT RUNOFF COEFFICIENT C
C = (Sum AxC)/A =
C = (Sum AxC)/A =
3
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
3
4
Intensity I = 21.8 / T EXP 0.78 = 88.2 mm/hr (City of Toronto Wet Weather Flow Guidelines November 2006 - IDF
equation - 2 year)
Run off coefficient C = 0.50
Q = CiA/360 m3/sec
ALLOWABLE RELEASE RATE TO 375mm MUNICIPAL STORM SEWER ON MUTUAL STREET
Q = CiA/360 m3/sec
The allowable discharge rate from the 59-71 Mutual residential development based on the City of Toronto Wet Weather
Flow Guidelines 2006 using a two (2) year return period will be as follows:
Drainage Area = 0.109 Hectares
BACKGROUND
The site is currently comprised of low rise residential houses fronting onto Mutual Street with asphalt, stone and
concrete driveways and parking areas in the rear of the buildings adjacent to the municipal laneway, which is situated to
the east of the property. Reference Figure No. 1 - Site Location Plan. The existing Pre-Development site runoff co-
efficent is C = 0.90 as calculated above in Section 2(a) and as detailed on the Pre-Development Drainage Areas Plan -
FIG-SWM-1. Currently there are no known SWM controls within the site and all storm flows leave the site as overland
flow and these storm flows are captured by the adjacent municipal road catchbasins, which inturn discharge into an
existing 375mm diameter concrete municipal storm sewer located within the Mutual Street road allowance. The 375mm
municipal storm sewer continues north on Mutual Street and into a 450mm storm sewer pipe which continues north on
Mutual Street to Dundas Street East. At Dundas Street East the 450mm storm sewer pipe connects and discharges into
a 1.45 metre x 1.1 metre concrete box Trunk Storm Sewer.
Intensity I = 21.8 / T EXP 0.78 = 88.2 mm/hr (City of Toronto Wet Weather Flow Guidelines November 2006 - IDF
equation-2 year)
As the Pre-Development runoff C is greater than 0.50, the runoff co-efficent is limited to C = 0.50
Run off coefficient C = 0.90
The existing discharge rate into the 375mm dia storm sewer fronting the 59-71 Mutual Street Development Site from the
property for the two year (2) storm event is:
Q = CiA/360 = 0.024 m3/sec
Time of concentration T = 10.0 minutes = 0.166 hours
Drainage Area = 0.106 Hectares (Development property becomes smaller by 0.03 ha due to land transfer from laneway
widening)
Allowable Release Rate from the Property is Q = CiA/360 = 0.013 m3/sec
Time of concentration T = 10.0 minutes = 0.166 hours
Reference Figure No. 3 - Mutual Street storm sewer as-built plan and profile, attached.
4
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
5
5.1
6 CITY OF TORONTO - RAINFALL - DURATION - FREQUENCY
7 POST DEVELOPMENT RAINFALL STORAGE CALCULATION
7.1
7.1.1
Modified Rational Method - Mass Curve Calculation
Q = storm flow volume = m3/sec
T = storm duration = hours
t = storm duration = seconds
Calculate 100 year Post Development Storm
Q = (CIA/360)
The 100 year Storm Event is to be controlled to the allowable 2 year Pre Development discharge rate of 0.013 m3/sec
calculated in Section 4
The reduction of storm water volume leaving the site will be achieved with the installation of a green roof and soft
landscape planting on the podium and attaining a Water Balance for the 5mm storm event.
Drainage Area = 0.106 Hectares
C = runoff co-efficient = 0.773 (Section 2b)
I = 59.7 / T EXP 0.80 = mm/hr (City of Toronto Wet Weather Flow Guidelines November 2006 - IDF equation - 100
year)
Control of the 100 year Post Development Storm to the 2 year Pre Development Storm
POST DEVELOPMENT CONDITION
Rainfall will be collected by way of roof drains and podium area drains and directed to the internal storm drain system
within the underground garage. The podium and roof encompass the entire property. The storm flows captured by the
storm drain system will be directed into a Stormwater Management cistern located within the underground parking
garage mid frontage against the Mutual Street foundation wall. Reference the proposed Site Servicing and Grading
Plan, Drawing No. SSG-01, attached. This drawing shows the proposed location, footprint and a cross section of the
proposed stormwater management cistern. The SWM Tank will provide detention storage for the 100 year post
development storm event. The storm discharge rate from the property will be controlled and will be reduced to a
maximum discharge rate of 0.013 m3/sec.
STRATEGY IS TO CONTROL STORM DISCHARGE RATE AND REDUCE VOLUME PRESENTLY BEING DIRECTED
INTO THE 375mm MUNICIPAL STORM SEWER
City of Toronto IDF Curve equations have been used, see attached.
5
November 2009 75
Chapter 3 – Storm Sewers
Storm Design Requirements
IDF Curves and Equations
The following intensity duration frequency (IDF) curves will be
applied to all districts across the City.
The equation of IDF curves is expressed as:
I = A T C
where:
I = intensity of rainfall in mm/hour
T = time of concentration in hours
(use 10 minutes inlet time or initial time of
concentration)
Parameters of A and C are as follows:
Table: Parameters of A and C
Return period (year) A C
2 21.8 -0.78
5 32.0 -0.79
10 38.7 -0.80
25 45.2 -0.80
50 53.5 -0.80
100 59.7 -0.80
Note: The parameter C is a negative value because the equation is
written in a "multiplication" instead of "reciprocal" format. It can also
be written in the familiar format as i = a/(t + b)C , where for a 2-year
storm, a = 21.8, b=0 and c=0.78.
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
Storm Duration
(minutes)T = Duration (hours)
I Intensity
(mm\hr)
Q = CIA/360
(m3/sec)
Q = CIAt/360
(m3)
2 0.033 907.13 0.206 24.78
4 0.067 521.01 0.119 28.46
6 0.100 376.68 0.086 30.86
8 0.133 299.24 0.068 32.69
10 0.167 250.32 0.057 34.18
12 0.200 216.35 0.049 35.45
14 0.233 191.25 0.044 36.56
16 0.267 171.87 0.039 37.55
18 0.300 156.41 0.036 38.45
20 0.333 143.77 0.033 39.27
22 0.367 133.22 0.030 40.02
24 0.400 124.26 0.028 40.73
26 0.433 116.55 0.027 41.38
28 0.467 109.84 0.025 42.00
30 0.500 103.94 0.024 42.58
32 0.533 98.71 0.022 43.14
34 0.567 94.04 0.021 43.66
36 0.600 89.84 0.020 44.17
38 0.633 86.03 0.020 44.65
40 0.667 82.57 0.019 45.11
42 0.700 79.41 0.018 45.55
44 0.733 76.51 0.017 45.97
46 0.767 73.84 0.017 46.39
48 0.800 71.37 0.016 46.78
50 0.833 69.07 0.016 47.17
52 0.867 66.94 0.015 47.54
54 0.900 64.95 0.015 47.90
56 0.933 63.09 0.014 48.25
58 0.967 61.34 0.014 48.59
60 1.000 59.70 0.014 48.92
62 1.033 58.15 0.013 49.24
64 1.067 56.70 0.013 49.55
66 1.100 55.32 0.013 49.86
68 1.133 54.01 0.012 50.16
70 1.167 52.77 0.012 50.45
72 1.200 51.60 0.012 50.73
74 1.233 50.48 0.011 51.01
76 1.267 49.41 0.011 51.29
78 1.300 48.40 0.011 51.55
80 1.333 47.43 0.011 51.81
51.81100 Year Post Development Storm Volume (m3)
6
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
7.1.2 Total required Storage volume for 100 year storm event:
Q = required storage volume (m3)
t = storm duration = seconds
Storm Duration
(minutes)T = Duration (hours)
Q = CIAt/360
(m3)
Ot
(m3)
Q = Required Vol
(m3)
2 0.033 24.78 1.56 23.22
4 0.067 28.46 3.12 25.34
6 0.100 30.86 4.68 26.18
8 0.133 32.69 6.24 26.45
10 0.167 34.18 7.80 26.38
12 0.200 35.45 9.36 26.09
14 0.233 36.56 10.92 25.64
16 0.267 37.55 12.48 25.07
18 0.300 38.45 14.04 24.41
20 0.333 39.27 15.60 23.67
22 0.367 40.02 17.16 22.86
24 0.400 40.73 18.72 22.01
26 0.433 41.38 20.28 21.10
28 0.467 42.00 21.84 20.16
30 0.500 42.58 23.40 19.18
32 0.533 43.14 24.96 18.18
34 0.567 43.66 26.52 17.14
36 0.600 44.17 28.08 16.09
38 0.633 44.65 29.64 15.01
40 0.667 45.11 31.20 13.91
42 0.700 45.55 32.76 12.79
44 0.733 45.97 34.32 11.65
46 0.767 46.39 35.88 10.51
48 0.800 46.78 37.44 9.34
50 0.833 47.17 39.00 8.17
52 0.867 47.54 40.56 6.98
54 0.900 47.90 42.12 5.78
56 0.933 48.25 43.68 4.57
58 0.967 48.59 45.24 3.35
60 1.000 48.92 46.80 2.12
62 1.033 49.24 48.36 0.88
64 1.067 49.55 49.92 -0.37
66 1.100 49.86 51.48 -1.62
68 1.133 50.16 53.04 -2.88
70 1.167 50.45 54.60 -4.15
72 1.200 50.73 56.16 -5.43
74 1.233 51.01 57.72 -6.71
76 1.267 51.29 59.28 -7.99
78 1.300 51.55 60.84 -9.29
80 1.333 51.81 62.40 -10.59
Q = [(CiAt/360) - (Ot)]
26.45 m3 of On Site Storage is required, based on O = 0.013 cms
T = storm duration = hours
O = 0.013 m3/sec = allowable outlet release rate (Calculated in Section 4 above)
7
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
8
8.1
8.2 PROVIDED ON SITE STORAGE
a) SWM CISTERN
STORAGE AREAS
b) ROOF
STORAGE AREAS
c)
d) STORM PIPES
STORAGE AREAS
e)
STORAGE AREAS
f)
STORAGE AREAS
g)
SUBTOTAL STORAGE PROVIDED
33.75
SUBTOTAL STORAGE PROVIDED
STORAGE VOLUMES
0.00
26.45 m3 of Storage is required
Driveway
STORAGE CALCULATION
STORAGE VOLUMES
0.00
STORAGE VOLUMES
0 m3
Parking Area
STORAGE VOLUMES
REQUIRED ON SITE STORAGE
STORAGE AREAS
33.75 m3
0 m3
Cistern - 2.5m (w) x 5.4m (l) x 2.5m (d)
nil
0.00
0.00
0.00250 dia
200 dia
0.00Landscape
SUBTOTAL STORAGE PROVIDED
STORAGE VOLUMES
SUBTOTAL STORAGE PROVIDED
0
MC-3500 STORMTECH SUBSURFACE DETENTION CHAMBERS
nil
STORM MANHOLES
300 dia
TOTAL STORAGE PROVIDED 33.75 m3
nil
STORAGE VOLUMES
0 m3
SUBTOTAL STORAGE PROVIDED
0
STORAGE VOLUMES
0
SUBTOTAL STORAGE PROVIDED
0.00
0nil
0 m3
0 m3
0 m3SUBTOTAL STORAGE PROVIDED
GROUND SURFACE
INFILTRATION TRENCH
SUBSURFACE STORAGE CHAMBERS
nil
8
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
10 SIZING ORIFICE PLATE
a) ORIFICE EQUATION: Q = Cd x A x SQRT(2 x g x h)……..(1)
Cd = 0.62 (for orifice plate with thickness less than D/4)
where: A = cross sectional area
h = head
g = 9.81
h = maximum head = water surface to orifice pipe (elevation at the centre of the orifice)
Invert of discharge pipe = 86.98m
h = 0.48m
Maximum allowable release rate = Q release = 0.013 m3/sec. (Section 4 above)
substituting into equation (1)
Cross sectional area = 0.0068 m2
However, to actually construct a cistern with the available storage depth of only 0.48m is not feasible. The geometric
constraints of the cistern structure will not allowable entry for inspection and maintenance. The shallowness of the
cistern will also preclude the building's storm drain system within the underground garage from making a proper
discharge connection into the cistern above the HWL and the building's storm drain pipes within the garage would
surcharge. The cistern would have to be hung structurally from the ground floor slab and the cistern footprint would be
prohibitive.
Giving Diameter = D = 0.093 m
In completing the stormwater management review a calculation was completed based on the cistern being able to
function as a gravity system with the release rate required of Q = 0.013 m3/s up to and including the major storm event
being controlled by an orifice plate.
Elevation at centre of orifice (93mm dia) = 87.02m
Therefore use an Outlet Control Orifice with a 93mm diameter
Due to the above constraints, which emanate from the shallow depth of cover of the 375mm storm sewer on Mutual
Street, the stormwater management cistern is proposed to be situated on the P1 level of the underground garage. With
the cistern located within the underground garage at a lower elevation than the proposed storm service connection, a
gravity connection is not obtainable. The controlled storm water release from the cistern is proposed to be by way of
pumping with the release not to exceed 0.013 m3/sec.
h = 87.50m (maximum allowable HWL for storage in stormwater management cistern; maximum head 100 Year Storm;
including free board)
Reference the proposed Site Servicing and Grading Plan, Drawing No. SSG-1, attached. This drawing shows the
proposed location, footprint and a cross section of the proposed stormwater management cistern.
0.013 = 0.62 x A x SQRT(2 x 9.81 x 0.48)
9
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
11 QUALITY CONTROL
The City of Toronto Wet Weather Flow Guideline target for Quality Control is the long term average removal of 80% of
total suspended solids (TSS) on an annual loading basis from all runoff leaving the development property based on the
post development condition. The long term removal requirement average of 80% TSS is consistent with the "enhanced
level of protection" recommended in the Ministry of Environment's Stormwater Planning and Design Manual, March
2003.
The 59-71 Mutual Street residential development is proposed to consist of a tower and a podium fully encompassing the
propery. The development will convert the existing impervious row house roofs and paved areas into a new roof top
area which will fully encompass the property. As the Ministry of Environment classifies rooftop runoff as clean (ie. not
subject to oil and sediment) on-site quality control is not being recommended as part of the proposed development.
However, all roof drains and outdoor podium area drains will come with strainers to prevent debris from entering into the
storm drain system. These building drains will capture and direct storm flows down to the P1 underground garage and
the P1 storm drains will convey flows and connect into the storm water management cistern.
The development will also have a green roof on the tower which will provide cleansing of storm flows in advance of
capture by roof drains.
10
59-71 MUTUAL STREET RESIDENTIAL DEVELOPMENT
CITY OF TORONTO
STORMWATER MANAGEMENT REPORT
exp SERVICES INC. BRM00605384A
DECEMBER 03, 2015
12
Location (59-71
Mutual Property)Area (m2)
5mm Storm
Volume (m3)
Generated
Run Off Co-
efficient (%)
Evaporation,
Infiltration and
Transpiration Loss
(%)
Total Estimated
Loss/Re-Use for
Water Balance
(m3)
Green Roof 300 1.50 45 55 0.83
Roof Terraces 760 3.80 90 10 0.38
Roof Mechanical 0 0.00 0 0 0.00Impervious
Walkways/Outdoor
Living Areas
0 0.00 0 0 0.00
Lawn/Landscaped
Areas0 0.00 0 0 0.00
Driveway 0 0.00 0 0 0.00
TOTAL 1060 5.30 1.21
Cistern Sump
(Irrigation
Re-Use)
4.09
SUBTOTAL 4.09Bio-Swales
(Infiltration
Trenches)
0.00
SUBTOTAL 0.00MC-3500 detention
chambers
(Infiltration)
0.00
SUBTOTAL 0.00
TOTAL 1060 5.30 5.30
This development however will have landscape elements and a significant area of green roof. The green roof will
contribute to the Water Balance through evapotranspiration through vegetative growth and direct evaporation through
wind and sun effect. The landscape elements and the planting of Street Trees will similarly contribute to the Water
Balance
It is further proposed to store captured rainfall within the Stormwater Management Cistern for Re-Use as a water supply
for irrigation of the landscape elements within the development and Street Trees anticipated to be planted within the
boulevard fronting the development.
The 5mm Storm event generates over the 1060m2 of the development site a total of 5.30 m3 of volume (1060m2 x
0.005m). The estimated evaporation, infiltration and evapotranspiration from the site and water reuse, is calculated
below;
The City of Toronto Wet Weather Flow Management Guidelines (Section 2.2.2.1) stipulates that the 5mm Storm Event
be retained on site to achieve the Guideline Water Balance Target.
The 59-71 Mutual Street development building structure will encompass the entire property and there will not be an
opportunity for infiltration into the insitu soil via infiltration trenches or underground retention chambers.
BALANCE CALCULATION - EVAPO-TRANSPIRATION, EVAPORATION, INFILTRATION, IRRIGATION, WATER
REUSE
WATER BALANCE - 5mm STORM EVENT
It is seen that with the proposed green roof and landscaping elements and water Re-Use for landscape irrigation the
Water Balance for this development has been achieved. A sump within the stormwater management Cistern will be
provided with a capacity of 4.09m3 and will be connected into a separate and distinct non potable landscape irrigation
delivery system.
11