Stormwater Management Report Les Terrasses Francesca ...

Stormwater Management Report

Les Terrasses Francesca

Presland Road, Ottawa, Ontario

June 12, 2013

Project No.: 11-5591

Submitted by

Dillon Consulting

Limited



Dillon Consulting Limited – Project Number: 11-5591 i

TABLE OF CONTENTS

Page No.

1.0 INTRODUCTION ............................................................................................................................ 1

2.0 SWM CRITERIA.............................................................................................................................. 1

3.0 SWM PLAN...................................................................................................................................... 1

3.1. Quantity Control ........................................................................................................................... 1

3.2. Quality Control ............................................................................................................................. 3

4.0 CONCLUSIONS............................................................................................................................... 3

List of Figures

Figure 1.0 Pre-Development Drainage Plan

Figure 2.0 Post-Development Stormwater Management Plan

List of Drawings

SERV-1 Grading and Servicing Plan

List of Appendices

Appendix A Detailed Calculations

Appendix B Stormceptor® Sizing Report



Dillon Consulting Limited – Project Number: 11-5591 1

1.0 INTRODUCTION

This Stormwater Management (SWM) Report has been prepared on behalf of Groupe Lépine in support

of a site plan application for the development of Les Terrasses Francesca (‘the Site’). The Site, currently

occupied by a convent constructed in the 1950s and private residence, is located in the northeast quadrant

of the intersection of Vanier Parkway and Presland Road, in the City of Ottawa (‘the City’), Ontario.

2.0 SWM CRITERIA

Based on discussions with the City of Ottawa Infrastructure Approvals Department, Rideau Valley

Conservation Authority (RVCA), and in accordance with the City’s Sewer design Guidelines (2004), it

was determined that the SWM criteria for the site consist of the following:

- Quantity Control – control the 100-year post-development flows to the 5-year pre-development

flows at C = 0.50; and

- Quality Control – Enhanced (80%) Total Suspended Solids Removal.

3.0 SWM PLAN

3.1. Quantity Control

Under existing conditions, the Site is occupied by a convent and private residence with some area

dedicated to natural landscaping; please see Figure 1.0 for the pre-development drainage plan. According

to a geotechnical report prepared by InspecSol, the Site is predominately situated on silty clay and sandy

silts. Based on a Site Servicing Report prepared by Genivar in September 2010, and correspondence with

the City of Ottawa, a runoff coefficient of C = 0.50 was assigned to represent the Site under existing

conditions.

A pre-development drainage plan (Figure 1.0) was developed to delineate existing conditions drainage

areas to existing Presland Road and Vanier Parkway outlets. Individual peak flows were calculated on the

basis of the City’s 5-year IDF data (Sewer Design Guidelines, 2004), and added together resulting in an

overall Site target. Table 1 below summarizes the 5-year target peak flows calculated by means of the

Rational Method for each catchment (see Appendix A). It should be noted that a portion of a residential

community to the north (103) drains overland onto the Site and outlets to Vanier Parkway; quantity

control will be provided for this catchment. Site target is not based on the external area.

Table 1 - Target Peak Flow Release Rates

Catchment ID Outlet 5-Year Peak

Flow Rate (L/s)

101 Vanier Parkway 37.6

102 Presland Road 134.6

SITE TARGET 172.2

Under post-development conditions, the Site will be occupied by a large terraced condo development,

landscaping and ground-level patios. Based on these post-development works and criteria noted above,

the following strategy was developed to satisfy the applicable criteria. Please refer to the pre-development

plan (Figure 1.0), the stormwater management plan (Figure 2.0) and the grading and servicing plan

(SERV-1) for additional details.

Based on information received from the City, the existing municipal system is surcharged during the 1 in

100 year event. The City indicates that the Hydrologic Grade Line (HGL) is at the pipe obvert of the




receiving municipal system. This stormwater management strategy has been developed under the same

assumption.

Site drainage from Catchments 201 and 202 will be directed and controlled in an underground detention

facility (Tank N) in the northwest corner of the building. It will be equipped with a pump that discharges

into the sewer draining to the main trunk along Vanier Parkway.

Similarly, runoff from Catchments 203 and 205 will be directed and stored in a detention facility (Tank S)

constructed within the building’s underground parking lot on the south side. This tank will be equipped

with a pump that discharges to the proposed 300 mm storm sewer. Based on direction and input from the

City, this proposed sewer will connect to the existing 1120 mm storm sewer on Presland Road. While the

City has indicated that this storm sewer is surcharged during the 1 in 100 year event, it is still

recommended to pump the stormwater from Tank S with a backwater valve to this system. This strategy

was recommended by the City rather than connect into the existing combined sewer system on Presland

Road.

Catchment 204 will drain uncontrolled from the site to Presland Road. It should be noted that the post-

development peak flow rate from Catchment 204 (20 L/s) draining overland to Presland Road is less than

the overland pre-development peak flow rate from Catchment 101 (37.6 L/s). This implies that overland

flow to Presland Road, which eventually enters the combined sewer system, is actually reduced (from

37.6 L/s to 20 L/s). This is due to the stormwater from Tank S being re-directed to the Presland Road

storm sewer.

The stormwater management strategy assumes the use of a variable rate pump at both tank locations, with

the maximum pump rate set to ensure that the overall target Site release rate (172.2 L/s) is achieved, even

with Catchment 204 being uncontrolled. Our stormwater management plan does not account for surface

storage in the design to achieve the quantity target, as sufficient storage has been provided by

underground cisterns.

In order to achieve the target Site release rate, storage volumes of 230 m3 and of 93 m

3 are required at

Tank N and Tank S, respectively. The final dimensions of the detention tanks and associated pumps will

be determined by the Mechanical Engineers during detailed design.

Please see Table 2 for a summary of the 100-year post-development peak flows, and the required and

provided storages as calculated using the Modified Rational Method (see Appendix A).




Table 2 - Summary of 100-year post-development flows and storage

Catchment

ID

Catchment

Area

(ha)

Area

Draining

To Tank

(ha)

Outlet and

Description of Quantity Control

Measures

100-Year

Peak

Flow Rate

(L/s)

Storage

Required

(m3)

Storage

Provided

(m3)

201 0.43

Vanier Parkway Landscaped area directed to underground

detention facility (Tank N) where it will be

stored and then pumped out to Vanier Parkway.

202 0.51

0.94 (To Tank N) Vanier Parkway

Roof area directed to underground detention

facility (Tank N) where it will be stored and

then pumped out to Vanier Parkway.

122 229 230

203 0.27

Presland Road Directed to underground detention facility

(Tank S) where it will be stored and then

pumped out to storm sewer on Presland Road.

205 0.05

0.32 (To Tank S) Presland Road

Directed to underground detention facility

(Tank S) where it will be stored then pumped

out to storm sewer on Presland Road.

30 93 93

204 0.04 - Presland Road Drains overland and uncontrolled to Presland

Road and eventually enters combined sewer.

20 0 0

SITE RELEASE RATE TARGET 172

3.2. Quality Control

In order to provide for quality control for the Site, an oil-grit separator (OGS) is proposed to provide

enhanced (80% TSS Removal) protection for the impervious surfaces near the entrance. It should be

noted that runoff from rooftops and pervious/landscape areas can be considered to be clean and do not

require additional treatment at Tank N. Quality control will therefore only be provided for the impervious

driveway area in front of the condo development (Catchment 203).

To achieve the Site water quality target, the Stormceptor system model STC750 is proposed. For the

detailed report please refer to Appendix B. The location of the OGS will be determined in collaboration

with the Mechanical Engineers during detailed design.

4.0 CONCLUSIONS

This report documents the development and detailed design of the Stormwater Management Plan for the

proposed development, and provides details for how the SWM Plan meets the City and RVCA criteria to

the extent practicable given the site constraints.

Stormwater Manzgem ent ReparlLes Terrasses Frencesca

Respectfully submitted;

Dillon

Grace Tesa,Water Resources Engineer

Lorenzo De Santis, P.Eng.Civil Engineer

eli:

{i. TñSAî0il1rË451

Díllon Consultíng Limíted - Projece Number: I1-5591 4

Figures and Drawings

Appendix A

Detailed Calculations

Project No.: 11-5591Project Name: Presland

ABC Location: City of Ottawa

IDF InformationStorm (year) 5 100

A 998.071 1735.688B 6.053 6.014 time in minutesC 0.814 0.82

tc (minutes) 10 10i (mm/hr) 104.19 178.56

Outlet CharacteristicsID Area C CxA Q5=CiA Q100=CiA

(ha) (m3/s) (m3/s)101 0.26 0.50 0.13 0.038 0.081102 0.93 0.50 0.465 0.135 0.288

SITE TARGET 1.19 0.50 0.172 0.369

Notes:1. IDF information as per the City of Ottawa Sewer Design Guidelines (2004)2. Under existing consitions runoff coefficient is to be 0.5 as the City of Ottawa Sewer Design Guidelines (2004)

M:\PROJECTS\DRAFT\11\115591 Les Terrasses Francesca - Presland\Toronto SWM\LATEST CALCS\June 112013\130611 Presland Modified Rational Method Existing Conditions 6/13/2013

Release Rates and Storage Requirements for 5-year Storm

Catchment Area Runoff CxA Flow Storage Storage Storage Sub-Surface Surface Type Diameter Invert Cd A Stage Head Orifice Major

ID Coeff. Required Provided Check Storage Storage (h) Flow Flow

(ha) (C) (m3/s) (ha-m) (ha-m) (ha-m) (ha-m) (mm) (m) (m2) (m) (m) (m3/s) (m3/s)

201+202 0.94 0.84 0.79 0.122 0.0064 0.0230 OK 0.0230 0.0000 - 0 0 0.62 0.0 0 0

203+205 0.32 0.95 0.30 0.030 0.0036 0.0093 OK 0.0093 0.0000 - 0 0 0.62 0.0 0 0204 0.04 1.00 0.04 0.012 0.0000 0.0000 uncontrolled 0 0 0.62 0.0 0 0

Total 1.30 0.87 1.13 0.164 0.0100 0.0324 0.0324 0.0000

Target 0.172 m3/s (5 year post to 5 year pre)

Release Rates and Storage Requirements for 100-year Storm

Catchment Area Runoff CxA Flow Storage Storage Storage Sub-Surface Surface Type Diameter Invert Cd A Stage Head Orifice Major

ID Coeff. Required Provided Check Storage Storage (h) Flow Flow

(ha) (C) (m3/s) (ha-m) (ha-m) (ha-m) (ha-m) (mm) (m) (m

2) (m) (m) (m

3/s) (m

3/s)

201+202 0.94 1.00 0.94 0.122 0.0229 0.0230 OK 0.0230 0.0000 - 0 0 0.62 0.0 0 0

203+205 0.32 1.00 0.32 0.030 0.0093 0.0093 OK 0.0093 0.0000 - 0 0 0.62 0.0 0 0204 0.04 1.00 0.04 0.020 0.0000 0.0000 uncontrolled 0 0 0.62 0.0 0 0

Total 1.30 1.00 1.30 0.172 0.0323 0.0324 0.0324 0.0000

Target 0.172 m3/s (100 year post to 5 year pre)

Notes:

1.100-year runoff coefficients adjusted as per MTO Drainage Design Manual (1997)

Catchment Parameters Storage Information Orifice Calculations: Q = CdA(2gh)1/2

Catchment Parameters Storage Information Orifice Calculations: Q = CdA(2gh)1/2

M:\PROJECTS\DRAFT\11\115591 Les Terrasses Francesca - Presland\Toronto SWM\LATEST CALCS\June 11 2013\130611 Presland Modified Rational MethodSummary of Storage-Flows 6/13/2013

Catchment ID 201+2025 year Modified Rational

IDF-ABC Informationstart time 5 A 998.071increment 5 B 6.053

C 0.814

Catchment ParametersArea 0.94 ha

Runoff C 0.84AxC 0.79

catchment target 0.122 m3/s

Sreq'd 64 m3

time flow vol in target vol out net(min) (m3/s) (m3) (m3/s) (m3) (m3)

5 0.31 92.88 0.12 36.60 56.2810 0.23 137.10 0.12 73.20 63.90 << MAX. STORAGE15 0.18 164.92 0.12 109.80 55.1220 0.15 184.88 0.12 146.40 38.4825 0.13 200.32 0.12 183.00 17.3230 0.12 212.88 0.12 219.60 -6.7235 0.11 223.44 0.12 256.20 -32.7640 0.10 232.56 0.12 292.80 -60.2445 0.09 240.57 0.12 329.40 -88.8350 0.08 247.73 0.12 366.00 -118.2755 0.08 254.19 0.12 402.60 -148.4160 0.07 260.09 0.12 439.20 -179.1165 0.07 265.51 0.12 475.80 -210.2970 0.06 270.54 0.12 512.40 -241.8675 0.06 275.22 0.12 549.00 -273.7880 0.06 279.61 0.12 585.60 -305.9985 0.06 283.74 0.12 622.20 -338.4690 0.05 287.63 0.12 658.80 -371.1795 0.05 291.33 0.12 695.40 -404.07

100 0.05 294.84 0.12 732.00 -437.16

M:\PROJECTS\DRAFT\11\115591 Les Terrasses Francesca - Presland\Toronto SWM\LATEST CALCS\June 112013\130611 Presland Modified Rational Method201+202 - Mod Rtl 5yr 6/13/2013



C 0.82




Sreq'd 229 m3


5 0.63 190 0.122 37 15410 0.47 280 0.122 73 20715 0.37 336 0.122 110 22620 0.31 376 0.122 146 229 << MAX. STORAGE25 0.27 407 0.122 183 22430 0.24 432 0.122 220 21235 0.22 453 0.122 256 19740 0.20 471 0.122 293 17845 0.18 487 0.122 329 15750 0.17 501 0.122 366 13555 0.16 514 0.122 403 11160 0.15 525 0.122 439 8665 0.14 536 0.122 476 6070 0.13 546 0.122 512 3475 0.12 555 0.122 549 680 0.12 564 0.122 586 -2285 0.11 572 0.122 622 -5090 0.11 580 0.122 659 -7995 0.10 587 0.122 695 -108

100 0.10 594 0.122 732 -138




C 0.814




Sreq'd 36 m3


5 0.12 35.59 0.03 9.00 26.5910 0.09 52.53 0.03 18.00 34.5315 0.07 63.19 0.03 27.00 36.19 << MAX. STORAGE20 0.06 70.84 0.03 36.00 34.8425 0.05 76.75 0.03 45.00 31.7530 0.05 81.57 0.03 54.00 27.5735 0.04 85.61 0.03 63.00 22.6140 0.04 89.11 0.03 72.00 17.1145 0.03 92.18 0.03 81.00 11.1850 0.03 94.92 0.03 90.00 4.9255 0.03 97.39 0.03 99.00 -1.6160 0.03 99.65 0.03 108.00 -8.3565 0.03 101.73 0.03 117.00 -15.2770 0.02 103.66 0.03 126.00 -22.3475 0.02 105.45 0.03 135.00 -29.5580 0.02 107.13 0.03 144.00 -36.8785 0.02 108.71 0.03 153.00 -44.2990 0.02 110.21 0.03 162.00 -51.7995 0.02 111.62 0.03 171.00 -59.38

100 0.02 112.97 0.03 180.00 -67.03




C 0.82




Sreq'd 93 m3


5 0.22 65 0.030 9 5610 0.16 95 0.030 18 7715 0.13 114 0.030 27 8720 0.11 128 0.030 36 9225 0.09 138 0.030 45 93 << MAX. STORAGE30 0.08 147 0.030 54 9335 0.07 154 0.030 63 9140 0.07 160 0.030 72 8845 0.06 166 0.030 81 8550 0.06 171 0.030 90 8155 0.05 175 0.030 99 7660 0.05 179 0.030 108 7165 0.05 183 0.030 117 6670 0.04 186 0.030 126 6075 0.04 189 0.030 135 5480 0.04 192 0.030 144 4885 0.04 195 0.030 153 4290 0.04 197 0.030 162 3595 0.04 200 0.030 171 29

100 0.03 202 0.030 180 22


Appendix B

Stormceptor® Sizing Report

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