srm architects inc

srm Architects Inc.

Servicing & Stormwater Management Report

Type of Document Report - Site Plan Submission

Project Name 256 Rideau Street and 211 Besserer Street Ottawa, Ontario

Project Number OTT-00229167-A0

Prepared By: Sheila Clarke

Reviewed By: Alam Ansari, M.Sc., P.Eng.

exp Services Inc. 100-2650 Queensview Drive Ottawa, ON K2B 7H6 Canada

Date Submitted November 13, 2015

exp Services Inc.

srm Architects Inc. 211 Besserer and 256 Rideau Street

OTT-00229167-A0 November 13, 2015

Legal Notification This report was prepared by exp Services Inc. for the account of srm Architects Inc.

Any use which a third party makes of this report, or any reliance on or decisions to be made based on it, are the responsibility of such third parties. Exp Services Inc. accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this project

exp Services Inc.


OTT-00229167-A0 November 13, 2015

Table of Contents Page

1 Introduction ....................................................................................................................... 1

2 Stormwater Design ............................................................................................................ 2

2.1 Stormwater Management Design Criteria ................................................................. 2

2.1.1 Minor System Design Criteria ....................................................................... 2

2.1.2 Major System Design Criteria ....................................................................... 2

2.2 Runoff Coefficients ................................................................................................... 2

2.3 Pre-Development Conditions .................................................................................... 3

2.4 Allowable Release Rate ............................................................................................ 3

2.5 Post Development Runoff and Storage Requirements .............................................. 4

3 Sanitary Sewer Design ...................................................................................................... 5

4 Watermain Design ............................................................................................................. 6

5 Erosion and Sediment Control ......................................................................................... 8

6 Conclusions ....................................................................................................................... 9

List of Appendices

Appendix A –

Figure1 - Site Location Figure2 - Drainage Area Plan

Appendix B –

Email - Stormwater Management Design Criteria Table 1 – Allowable Release Rate Table 2 – Uncontrolled Flow Table 3 – Stormwater Storage Requirement Table 4 – Orifice Sizing Hydrovex Selection Chart

Appendix C –

Supply/Pressure Flow Data Email - Water Demand

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List of Drawings

Site Servicing and Grading plan SGP1 (attached separately)

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1 Introduction

This report will address the serviceability of the proposed site, specifically relating to the adequacy of the existing municipal storm sewer, sanitary sewer, and watermains to hydraulically convey the necessary storm runoff, sanitary sewage and water demands that will be placed on the existing system as a result of this proposed development located at 211 Besserer Street and 256 Rideau St, Ottawa, Ontario. The site is situated between Rideau Street and Besserer Street in the City of Ottawa, Ontario as shown on Figure 1 in Appendix A. The 0.12 hectare development being proposed by srm Architects Inc will consist of a 26 storey building with 279 apartment units and 320 sq. m. of commercial space. There will be 4 ground level vehicle parking spaces and 188 underground bicycle parking spaces. Vehicular access to the site is from the main driveway located on the south side of the site at Besserer Street. Pedestrian accesses are proposed on both the south and north sides of the property off of Rideau Street and Besserer Street. There is currently one building on the site and an asphalt parking area. There is no existing vegetation on the site.

Stormwater runoff from the site presently flows overland to Rideau Street, where it is captured into the existing storm sewer system via roadway catch basins. Existing storm and sanitary sewers and water mains are present on both Rideau Street and Besserer Street. Watermain and sanitary service connections from the proposed site will connect to the municipal services on Rideau Street. The storm service will connect to the municipal storm sewer on Besserer Street.

This report will identify any sanitary, storm or watermain servicing concerns, and provide a design brief for submission with the engineering drawings for City of Ottawa site plan approval.

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2 Stormwater Design

2.1 Stormwater Management Design Criteria

Design of the storm sewer system was completed in conformance with the City of Ottawa Design Guidelines. (October 2012). Section 5 “Storm and Combined Sewer Design” from the design manual was referenced for runoff coefficients and inlet times. The allowable release rate for the site is limited to a 5-year storm event using a time of concentration of 20 minutes and a runoff coefficient of 0.50. Flows in excess of the 5 year predevelopment runoff rate are detained onsite using onsite storage for up to the 100-year storm event. (see attached email from the City)

2.1.1 Minor System Design Criteria

The storm has been designed and sized based on the rational formula and the Manning’s Equation under free flow conditions for the 5-year storm using a 10-minute inlet time.

Inflow rates into the minor system are limited to a 5-year storm event using a time of concentration of 20 minutes, and a runoff coefficient of 0.50.

2.1.2 Major System Design Criteria

The major system has been designed to accommodate on-site detention with sufficient capacity to attenuate the 100-year design storm.

On site storage is provided and calculated for up to the 100-year design storm. Calculation of the required on-site storage volume has been supported by calculations provided in Appendix B.

Calculation of the required storage volumes has been prepared based on the Modified Rational Method as identified in Section 8.3.10.3 of the City’s Sewer Guidelines.

2.2 Runoff Coefficients

Runoff coefficients for impervious surfaces (roofs, asphalt, and concrete) were taken as 0.90, there were no existing or proposed pervious surfaces on the site. However, The City of Ottawa requires that the runoff coefficient for existing conditions be no greater than 0.5. Therefore 0.5 was used as the runoff coefficient for the allowable release rate from the site. The calculated average runoff coefficient for the overall site area under post-development conditions is 0.90. A runoff coefficient of 1.00 was used for the 100-year storm event.

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2.3 Pre-Development Conditions

Under pre-development conditions the site consists of building roof and asphalt parking areas. As shown in Figure 2 of Appendix A, runoff from the site flows from the sloped roof area, area E1, and asphalt parking areas, area E2, to existing catch basins on Rideau Street. The pre-development runoff coefficient for the site is 0.90 based on the areas below.

Hard Surfaces = 460 m² (roof) and 770m² (asphalt)

Soft Surfaces = 0 m²

Using a time of concentration (TC) of 20 minutes and an average runoff coefficient of 0.90, the pre-development release rates from the site is determined to be 21.6 L/s for the 5-year event and 36.9 L/s for the 100-year even using the Rational Method.

2.4 Allowable Release Rate

The City of Ottawa requires that storm runoff be released in a controlled manner. To control runoff from the site it will be necessary to limit post-development flows for all storm return periods up to the 100-year event. The allowable release rate from the site is based on the requirements of Section 8.3.7.3 of the City of Ottawa Sewer Guidelines that state that:

All commercial, institutional, and industrial site plan applications must include on-site stormwater management measures to avoid the impacts on the downstream storm system. If flow restriction information from the site in question is not available, the designer must contact the City to obtain the applicable flow allocation parameters. In most cases, all runoff must be controlled to the 2-year or 5year pre-development level depending on the design return period of the receiving sewer, and all ponding must be controlled on-site. In the case of a site re-development, over-controlling may be required if the capacity of the receiving sewer is in question. In such a case the pre-development condition will be determined using the smaller of a runoff coefficient of 0.5 (0.4 in combined areas) or the actual existing site runoff coefficient.

Correspondence with City of Ottawa staff, which is provided in Appendix B, also confirmed that the allowable release rate from the site shall be based on a 5-year storm, runoff coefficient of 0.50, and a time of concentration of 20 minutes. Using the above mentioned parameters, the allowable release rate for the site was determined to be 12.0 L/s. See Table 1 - Allowable Release Rate in Appendix B.

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2.5 Post Development Runoff and Storage Requirements

The overall imperviousness of the site has remained the same; the post-development flow will be controlled to a lower allowable release rate into the city storm sewer system. The allowable release rate from the site is 12.0 L/s. Refer to Table 1 - Allowable Release Rate in Appendix B. The site has been divided into two drainage areas, areas A1 & A2. The roof areas will be defined as area A1. Area A2 is the total area that will flow uncontrolled offsite. Refer to Figure 2 in Appendix A.

Using a post-development time of concentration (TC) of 10 minutes and average runoff coefficient of 1.00, the 100-year uncontrolled flow rate for drainage area A2 was determined to be 6.9 L/s. See Table 2 - Uncontrolled flow in Appendix B.

As the uncontrolled runoff cannot be restricted it is necessary to subtract the uncontrolled runoff from the allowable release rates. Therefore, the 100-year restricted flow rate is 5.1 L/s.

Runoff from the flat roofs of the proposed building, area A1, will be captured using roof drains that will drain to a storage tank, located below grade in the basement. The storage tank is provided in order to control the runoff in events greater than 5 year and up to 100 year. The storage tank will be designed to provide the required storage for the 100-year event. Total storage volume required to restrict flows from the site to 5.1 L/s was calculated to be 17.3m³ for the 5-year event and 42.8m³ for the 100-year event. See Table 3 - Storage Required in Appendix B. The release rate from the tank to the municipal storm sewer will be controlled by providing an ICD at the outlet from the tank. ICD sizing calculations are included in Appendix B.

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3 Sanitary Sewer Design

The sanitary service from the proposed development will be connected to the existing sanitary 300 mm diameter sanitary sewer on Rideau Street. The anticipated peak sanitary flow from the proposed 279 apartments will be approximately 8.40 L/s.

Design Flows

Residential

Total domestic pop:

One Bedroom units (93) x 1.4 ppu: 130.2

Two Bedroom units (186) x 2.1 ppu: 390.6

Total: 520.8

Q Domestic = 520.8 x 350 l/person/day x (1/86,400 sec/day) = 2.09 L/sec

Peaking Factor M = 1 + 14 = 4.04 *use 4 maximum

4 + (369/ 1000) 0.5

Q Peak Domestic = 2.09 L/sec x 4.0 = 8.36 L/sec

Commercial

Avg. Flow = 50,000 L/ha/day

Peak Factor = 1.5

Area = 320 sq.m.

Q Peak Comm = 0.032 ha x 50,000 L/ha/day x 1.5 x (1/86,400 sec/day) = 0.03 L/sec

Infiltration

Q Infiltration = 0. 28 L/ha/sec x 0.032 ha = 0.009 L/sec

Total Peak Sanitary Flow = 8.36 + 0.03 + 0.009 = 8.40 L/sec

A 250 mm sanitary lateral has been proposed to convey flows from the proposed apartment building into the existing sanitary sewer. The proposed lateral with a minimum grade of 1.0% has a capacity of 84.2L/sec, based on Manning’s Equation under full flow conditions. Therefore, the proposed 250 mm diameter lateral will be adequate to convey the estimated peak sewage flow.

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4 Watermain Design

The available fire flows based on City provided fire flow testing results is approximately 3,257 igpm (247 L/sec) at King Edward Avenue. (Refer to Appendix C) Current fire hydrant flow testing results have been requested from the City for the fire hydrants adjacent to 256 Rideau.

Estimated domestic water demands for the development are as follows:

Residential

Average daily demand (L/sec) for 520.8 population

Residential Average Demand = 520.8 x 350 L/person/day x (1/86,400) = 2.09 L/sec

Using a peak factor of 2.5, the Maximum Daily Demand = 2.5 x 2.09 L/sec = 5.23 L/sec

Using a peak factor of 2.2, the Maximum Hour Demand = 2.2 x 2.09 L/sec = 4.60 L/sec

Commercial

Commercial area = 320m2 = 0.032ha

Average daily demand (L/sec):

Commercial Average Demand = 0.032 ha x 50,000 L/ha/day x (1/86,400) = 0.018 L/sec

Using a peak factor of 1.5, the Maximum Daily Demand yields:

Maximum Commercial Daily Demand = 0.018 x 1.5 = 0.028 L/sec

Using a peak factor of 1.8, the Maximum hourly demand yields:

Maximum Commercial Hourly Demand = 0.018 x 1.8 = 0.032 L/sec

Total Average Daily demand = 2.11 L/sec

Total Maximum Daily Demand = 5.25 L/sec

Total Maximum Hourly Demand = 4.63 L/sec

The mechanical engineer for the project has estimated the peak domestic water demand at 410 gpm (25.9 L/s) and the fire protection requirement as 325 gpm (20.5 L/sec) (Refer to Appendix C). The fire protection system will be designed by the mechanical engineer in compliance with the Ontario Building Code and NFPA 13.

Based on the estimated domestic and fire flow demands and the fire flow information provided by the City the existing water supply system will have adequate capacity to meet the domestic

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and fire demands for the project. A 203 mm diameter watermain service was installed during the Rideau Street reconstruction in 2012. This water service will be used to service the proposed development.

The building’s fire department connection (Siamese) will be located along the Rideau Street frontage to be within 45m of an existing hydrant.

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5 Erosion and Sediment Control

Temporary and permanent erosion and sediment control measures will be implemented prior to, during and after construction; and will be inspected regularly.

To prevent sediment and debris from entering the storm system during construction, the following erosion and sediment control measures will be implemented during construction in accordance with the “Guidelines on Erosion and Sediment Control for Urban Construction Sites” (Government of Ontario, May 1987):

Filter cloth will be placed under the grates of all area drains and remain in place until vegetation has been established and construction is completed;

Street sweeping and cleaning will be performed on all roads adjacent to active construction on a regular basis;

The deposits will be disposed of as per the requirements of the contract

During the course of construction, if the engineer believes that additional prevention methods are required to control erosion and sedimentation, the contractor will install additional silt fences or other methods as required to the satisfaction of the engineer, and

Construction and maintenance requirements for erosion and sediment controls to comply with Ontario Provincial Standard Specification OPSS 805, and City of Ottawa specifications.

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Appendix A:

Figure1 - Site Location Figure2 - Drainage Area Plan

SITE LOCATION256 RIDEAU STREET

SITE LOCATION

t: +1.613.688.1899 | f: +1.613.225.73302650 Queensview Drive, Unit 100Ottawa, ON K2B 8H6Canada

www.exp.com

BUILDINGS EARTH & ENVIRONMENT ENERGYINDUSTRIAL INFRASTRUCTURE SUSTAINABILITY

exp Services Inc.

LafleurMA

Text Box

OTT-00229167-A0

LafleurMA

Text Box

SRM ARCHITECTS INC.

LafleurMA

Text Box

13/11/2015

C=0.90

A=0.109

A1

C=0.90

A=0.008

A2a

C=0.90

A=0.006

A2b

C=0.90

A=0.046

E1

C=0.90

A=0.077

E2

DRAINAGE AREA PLAN

SRM ARCHITECTS INC.

t: +1.613.688.1899 | f: +1.613.225.7330

2650 Queensview Drive, Unit 100

Ottawa, ON K2B 8H6

Canada

www.exp.com

BUILDINGS EARTH & ENVIRONMENT ENERGY

INDUSTRIAL INFRASTRUCTURE SUSTAINABILITY

exp Services Inc.

PRE-DEVELOPMENT

DRAINAGE AREAS

POST-DEVELOPMENT

DRAINAGE AREAS

C=0.90

A=0.289

A1

Pre-development

area (Ha)

Roof

Asphalt

E1

E2

A1

A2

.046

.077

Total

.123 .123

.109

.014

Post-development

area (Ha)

BESSERER STREET

RIDEAU STREET

BESSERER STREET

RIDEAU STREET

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Appendix B:

Email - Stormwater Management Design Criteria Table 1 – Allowable Release Rate

Table 2 – Uncontrolled Flow Table 3 – Stormwater Storage Requirement

Table 4 – Orifice Sizing Hydrovex Selection Chart

256 RideauProject: OTT-00229167-A0Date: November, 2015

Table 1 - Allowable Release Rate

Runoff Coefficient Equation

C = (Ahard x 0.9 + Asoft x 0.2 )/Atot

5 Year Event

C Intensity Area

5 Year 0.50 70.25 0.123

2.78CIA= 12.01

12.0

**Use a 20 minute time of concentration for 5 year

Equations:

Flow Equation

Q = 2.78 x C x I x A

Where:

C is the runoff coefficient

I is the intensity of rainfall, City of Ottawa IDF

A is the total drainage area

L/s


Table 2 - Uncontrolled Flow

(Drainage Area A2)

Post Dev run-off Coefficient "C"

Area Surface Ha "C" Cavg "C"*1.2 Cavg

Total Asphalt & Roof 0.014 0.90 0.90 1.00 1.00

0.014 Grass 0.000 0.20 0.20

100 Year Event C Intensity Area

100 Year 1.00 178.56 0.014

2.78CIA= 6.95

6.9

**Use a 10 minute time of concentration for 100 year

Equations:Flow Equation

Q = 2.78 x C x I x A

Where:


I is the intensity of rainfall, City of Brockville IDF


5 Year Event 100 Year Event

L/s


Table 3 - Storage Required

(Drainage Area A1)Runoff Coefficient Equation

Post Dev run-off Coefficient "C" C = (Ahard x 0.9 + Asoft x 0.2 )/Atot

Area Surface Ha "C" Cavg "C"*1.2 Cavg

Total Asphalt & Roof 0.109 0.90 1.00

Gravel 0.000 0.60 0.72

0.109 Grass 0.000 0.20 0.24

QUANTITY STORAGE REQUIREMENTS - 5 Year

0.109 = Area(ha)

0.90 = C

Return Time Intensity Flow Allowable Net Runoff To Storage

Period (min) (mm/hr) Q (L/s) Runoff (L/s) Be Stored (L/s) Req'd m3

10 104.19 28.4 5.1 23.3 14.0

20 70.25 19.2 5.1 14.1 16.9

5 YEAR 30 53.93 14.7 5.1 9.6 17.3

40 44.18 12.0 5.1 6.9 16.7

50 37.65 10.3 5.1 5.2 15.5

Max = 17.3

QUANTITY STORAGE REQUIREMENTS - 100 Year

0.109 = Area(ha)

1.00 = *C

Return Time Intensity Flow Allowable Net Runoff To Storage

Period (min) (mm/hr) Q (L/s) Runoff (L/s) Be Stored (L/s) Req'd m3

10 178.56 54.1 5.1 49.0 29.4

20 119.95 36.3 5.1 31.2 37.5

100 YEAR 30 91.87 27.8 5.1 22.7 40.9

40 75.15 22.8 5.1 17.7 42.4

50 63.95 19.4 5.1 14.3 42.8

60 55.89 16.9 5.1 11.8 42.6

Max = 42.8

Equations:Flow Equation

Q = 2.78 x C x I x A

Where:


I is the intensity of rainfall, City of Ottawa IDF


5 Year Event 100 Year Event

0.90 1.00


Table 4 - Orifice Sizing

Water Retetion Tank

For the 100-Year Event

Maximum Discharge = 5.1 (L/s)

Maximum Design Head = 2.1 (m)

Using Figure 3 from Hydrovex VHV/SVHV Vortex Flow Regulator

Model Required: 75 VHV-1

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Appendix C:

Supply/Pressure Flow Data Email - Water Demand

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