Site Servicing and Stormwater Management Report, 1117 ...

Site Servicing and Stormwater Management Report, 1117 Longfields Drive and 1034 McGarry Terrace Ottawa, ON

File: 160401399

Prepared for: 1879369 Ontario Inc. cob as Saint Joseph Developments

Prepared by: Stantec Consulting Ltd. 1331 Clyde Avenue, Suite 400 Ottawa, ON K2C 3G4

February 2, 2018

Sign-off Sheet

This document entitled Site Servicing and Stormwater Management Report, 1117 Longfields Drive and 1034 McGarry Terrace Ottawa, ON was prepared by Stantec Consulting Ltd. (“Stantec”) for the account of 1879369 Ontario Inc. cob Saint Joseph Developments (the “Client”). Any reliance on this document by any third party is strictly prohibited. The material in it reflects Stantec’s professional judgment in light of the scope, schedule and other limitations stated in the document and in the contract between Stantec and the Client. The opinions in the document are based on conditions and information existing at the time the document was published and do not take into account any subsequent changes. In preparing the document, Stantec did not verify information supplied to it by others. Any use which a third party makes of this document is the responsibility of such third party. Such third party agrees that Stantec shall not be responsible for costs or damages of any kind, if any, suffered by it or any other third party as a result of decisions made or actions taken based on this document.

Prepared by

(signature) Thakshika Rathnasooriya

Reviewed by

(signature) Karin Smadella, P.Eng.

SITE SERVICING AND STORMWATER MANAGEMENT REPORT, 1117 LONGFIELDS DRIVE AND 1034 MCGARRY TERRACE OTTAWA, ON

Table of Contents

1.0 INTRODUCTION ...........................................................................................................1.1 1.1 OBJECTIVE ....................................................................................................................... 1.2

2.0 BACKGROUND ............................................................................................................2.1

3.0 WATER SUPPLY SERVICING..........................................................................................3.1 3.1 BACKGROUND ............................................................................................................... 3.1 3.2 WATER DEMANDS .......................................................................................................... 3.1 3.3 PROPOSED SERVICING .................................................................................................. 3.2 3.4 SUMMARY OF FINDINGS ................................................................................................ 3.2

4.0 WASTEWATER SERVICING ...........................................................................................4.3 4.1 BACKGROUND ............................................................................................................... 4.3 4.2 DESIGN CRITERIA ............................................................................................................ 4.3 4.3 PROPOSED SERVICING .................................................................................................. 4.3 4.4 MCGARRY TERRACE EXTENSION AND FUTURE PHASE 2 ............................................ 4.4

5.0 STORMWATER MANAGEMENT ....................................................................................5.1 5.1 OBJECTIVES ..................................................................................................................... 5.1 5.2 SWM CRITERIA AND CONSTRAINTS .............................................................................. 5.1 5.3 STORMWATER MANAGEMENT ...................................................................................... 5.2

5.3.1 Existing Conditions ....................................................................................... 5.2 5.3.2 Allowable Release Rate ............................................................................. 5.2 5.3.3 Storage Requirements ................................................................................ 5.3 5.3.4 Results ............................................................................................................ 5.5

5.4 MCGARRY TERRACE EXTENSION AND FUTURE PHASE 2 ............................................ 5.5

6.0 GRADING AND DRAINAGE.........................................................................................6.7

7.0 UTILITIES........................................................................................................................7.1

8.0 APPROVALS .................................................................................................................8.1

9.0 EROSION CONTROL DURING CONSTRUCTION ..........................................................9.2

10.0 GEOTECHNICAL INVESTIGATION AND ENVIRONMENTAL ASSESSMENT .................10.3

11.0 CONCLUSIONS ..........................................................................................................11.1 11.1 WATER SERVICING ....................................................................................................... 11.1 11.2 SANITARY SERVICING ................................................................................................... 11.1 11.3 STORMWATER SERVICING ........................................................................................... 11.1

11.4 GRADING ...................................................................................................................... 11.1


11.5 UTILITIES .......................................................................................................................... 11.1 11.6 APPROVALS/PERMITS ................................................................................................... 11.2

LIST OF TABLES Table 1: Estimated Wastewater Peak Flow ............................................................................ 4.3 Table 2: Target Release Rates .................................................................................................. 5.3 Table 3: 100 Year Summary of Roof Controls ......................................................................... 5.4 Table 4: 100 Year Storage Requirements and Release Rates ............................................. 5.4 Table 5: Phase 1 Summary 100 Year Event Release Rates .................................................. 5.5 Table 6: Pavement Structure – Car Only Parking Areas ..................................................... 10.3 Table 7: Pavement Structure – Access Lanes ...................................................................... 10.3

LIST OF FIGURES Figure 1.1: Location Plan .......................................................................................................... 1.1

LIST OF APPENDICES

WATER SUPPLY SERVICING ....................................................................... A.1 A.1 Domestic Water Demand Estimate ............................................................................ A.1 A.2 Fire Flow Requirements Per FUS .................................................................................... A.2 A.3 Boundary Conditions ..................................................................................................... A.3

WASTEWATER SERVICING ......................................................................... B.1 B.1 Sanitary Sewer Design Sheet ........................................................................................ B.1

STORMWATER MANAGEMENT .................................................................. C.2 C.1 Storm Sewer Design Sheet ........................................................................................... C.2 C.2 Rational Method Calculations .................................................................................... C.3

GEOTECHNICAL INVESTIGATION ............................................................. D.4

DESIGN CRITERIA AND REPORT EXCERPTS ................................................ E.5

DRAWINGS ................................................................................................. F.6


INTRODUCTION February 2, 2018

w:\active\160401399_1117 longfields and 1034 mcgarry terrace\design\report\servicing\rpt__2018-01-27_servicing1.docx 1.1

1.0 INTRODUCTION

This Site Servicing and Stormwater Management Report has been prepared to support an application for Site Plan Control for a property known municipally as 1117 Longfields Drive and 1034 McGarry Terrace. The site is currently zoned Mixed Use Centre Zone (MC) and is located in the City of Ottawa in the north-western quadrant of the intersection of Marketplace Avenue and Longfields Drive and is illustrated on Figure 1.1.

Figure 1.1: Location Plan

Phase 1 of the proposed mixed use development is 0.56ha in area and consists of two apartment towers above approximately 2,100 m2 of retail commercial space. A total of 290 condominium apartments are proposed with a total of 380 parking spaces, the majority of which are underground. The site access will be from Marketplace Avenue.

Phase 1 of the development will require the relocation of municipal sanitary and storm sewers currently crossing the site from north to south. The existing sewers from the existing terminus of McGarry Terrace to Marketplace Avenue will be abandoned and removed following the construction of new sanitary and storm sewers within the alignment of the future McGarry

SUBJECT PROPERTY

PHASE 1




Terrace extension. The extension of the McGarry Terrace roadway and remaining ROW infrastructure will form part of the future Phase 2 works. Details of the sewer design are included in sections 4.4 and 5.5 of this report.

The intent of this report is to provide a servicing scenario for the site that is free of conflicts, provides on-site servicing in accordance with City of Ottawa design guidelines, and utilizes the existing local infrastructure in accordance with the guidelines outlined per consultation with City of Ottawa staff.

1.1 OBJECTIVE

This servicing and stormwater management report has been prepared to present a servicing scheme that is free of conflicts and which utilizes the existing infrastructure as outlined in the different background studies outlined in Section 2.0. Infrastructure requirements for water supply, sanitary and storm sewer services are presented in this report.

Criteria and constraints provided by the City of Ottawa and background studies have been used as a basis for the servicing design of the proposed development. Specific elements and potential development constraints to be addressed are as follows:

• Prepare a detailed grading plan in accordance with the proposed site plan and existing grades.

• Relocate the existing storm and sanitary sewers that currently cross the site to the future McGarry Terrace extension right of way.

• Storm Sewer Servicing

o Define major and minor conveyance systems in conjunction with the proposed grading plan,

o Determine the stormwater management storage requirements to meet the allowable release rate for the site,

o Coordinate with the architect and mechanical engineer and provide the required information to ensure the design of the internal plumbing system meets the stormwater management criteria and restrictions for the site,

• Wastewater Servicing

o Define and size the sanitary collection system.

• Water Servicing

o Estimate water demands to characterize the proposed feed for the development which will be serviced from the existing 300 mm watermain along Marketplace Avenue,

o Watermain servicing for the development is to be able to provide average day and maximum day (including peak hour) demands (i.e. non-emergency conditions) at pressures within the acceptable range of 40 to 100 psi (275 to 690 kPa),




o Under fire flow (emergency) conditions, the water distribution system is to maintain a minimum pressure greater than 20 psi (140 kPa).

The accompanying drawings included at the back of this report illustrate the proposed internal servicing and grading scheme for the site. Design drawings for the McGarry Terrace storm and sanitary sewer extension is also included at the back of the report.


BACKGROUND February 2, 2018


2.0 BACKGROUND

The following background studies have been referenced during the servicing and stormwater management design of the proposed site:

Tega Marketplace, Ottawa, ON, Site Servicing Report, Stantec Consulting Ltd., February 4, 2014

Geotechnical Investigation Update Proposed Multi-Storey Building(s), 1034 McGarry Terrace and 1117 Longfields Drive, Ottawa, ON, Paterson Group Inc., November 3, 2017

Minto Communities Inc. Infrastructure Servicing Brief, Ampersand in Chapman Mills Town Centre, DME, Revised October 2010

Nepean South Chapman Mills Stormwater Management Servicing Report – Second Addendum. IBI Group, September 2010

Nepean South Chapman Mills Stormwater Management Servicing Report. IBI Group, August 2006

South Nepean Collector Wastewater Servicing Study and Functional Design Final Report, Dillon Consulting, October 2003

City of Ottawa Design Guidelines – Water Distribution, City of Ottawa, July 2010

City of Ottawa Sewer Design Guidelines, City of Ottawa, October 2012


WATER SUPPLY SERVICING February 2, 2018


3.0 WATER SUPPLY SERVICING

3.1 BACKGROUND

The proposed mixed use development is located on the north-western side of the intersection of Marketplace Avenue and Longfields Drive in the Barrhaven community of the City of Ottawa. The property is located within the City’s Pressure Zone BARR. Average ground elevations of the site are approximately 97.05m. Under normal operating conditions, hydraulic gradelines vary from approximately 145.9m to 147.8m as confirmed through boundary conditions as provided by the City of Ottawa.

According to City of Ottawa District Plans, existing water infrastructure present on Marketplace Avenue is a 305 mm diameter PVC watermain branching off a 406 mm PVC watermain running along Longfields Drive. Given the size of the development and domestic demand requirements for the proposed high-rise buildings, Phase 1 of the site will be require two separate connections to the main within Marketplace Avenue separated by a valve for redundancy. The proposed site will be serviced via a 150mm building service connection to the existing 305 mm watermain along Marketplace Avenue, as shown on the Site Servicing Plan (see Drawing SSP-1).

3.2 WATER DEMANDS

Water demands for the development were estimated using the Ministry of Environment’s Design Guidelines for Drinking Water Systems (2008) and the Ottawa Design Guidelines – Water Distribution (2010). A daily rate of 350 L/cap/day has been applied for the population of the proposed site. Population densities have been assumed 2.1 pers./two-bedroom apartment unit, and 1.4 pers./one-bedroom apartment unit. See Appendix A.1 for detailed domestic water demand estimates. Additionally, commercial and retail domestic demands have been estimated at 50,000L/ha/day of floor area.

The average day demand (AVDY) for the entire site was determined to be 2.03 L/s. The maximum daily demand (MXDY) is 2.5 times the AVDY for residential areas and 1.5 times the AVDY for commercial areas, which sums to 4.94 L/s. The peak hour demand (PKHR) is 2.2 times the MXDY for residential areas and 1.8 times the MXDY for commercial areas, totaling 10.81 L/s.

Non-combustible combustible construction was considered in the assessment for fire flow requirements according to the FUS Guidelines, with two hour fire separations separating each floor based on requirements for buildings over six storeys in the Ontario Building Code (OBC). The FUS Guidelines indicate that low hazard occupancies include apartments, dwellings, dormitories, hotels, and schools, and as such, a low hazard occupancy / limited combustible building contents credit was applied. A sprinkler system conforming to NFPA 13 was considered, and a credit applied per FUS Guidelines. Based on calculations per the FUS Guidelines (Appendix A.2 the minimum required fire flows for this development are 117 L/s (7,000L/min).


WATER SUPPLY SERVICING February 2, 2018


3.3 PROPOSED SERVICING

Per the boundary conditions provided by the City of Ottawa and based on an approximate elevation on-site of 97.1m, adequate flows are available for the subject site with pressures ranging from 48.9m (69.2psi) to 50.8m (71.8psi). This pressure range is within the guidelines of 50-80 psi based on Ottawa’s Design Guidelines for Water Distribution. Assuming a 5psi head loss per floor of development, pressures at the 16th level of the building will be below the required 40psi, and as such, jet pumps to be designed by the mechanical engineering consultant will be required to service the upper levels of the development.

Using boundary conditions for the proposed development under maximum day demands and a fire flow requirement of 7,000L/min per the FUS methodology, it can be confirmed that the system will maintain a residual pressure of approximately 69.9 psi; which is in excess of the required 140 kPa (20 psi). The above demonstrates that the existing watermain within Marketplace Avenue can provide adequate fire and domestic flows in excess of flow requirements for the subject site. An existing hydrant is located south of the subject site, and is within 45m of the proposed building siamese connection per OBC requirements.

3.4 SUMMARY OF FINDINGS

The proposed development is located in an area of the City’s water distribution system that has sufficient capacity to provide both the required domestic and emergency fire flows. Based on boundary conditions as provided by City of Ottawa staff, fire flows are available for this development based on FUS guidelines and as per the City of Ottawa water distribution guidelines. Two redundant services that can be isolated at the City main have been proposed for the site.


February 2, 2018


4.0 WASTEWATER SERVICING

4.1 BACKGROUND

The site will be serviced via an existing 250 mm diameter sanitary sewer running east along Marketplace Avenue ROW at the southern boundary of the site which ultimately discharges into the South Nepean Collector Sewer (see Drawing SP-1). It is proposed to make one 200mm diameter service lateral connection directly to the existing sewer to service the proposed site.

Phase 1 of the proposed development is 0.56 ha in area and will be developed with 290 residential units and 2,084 m2 of commercial floor area.

4.2 DESIGN CRITERIA

As outlined in the City of Ottawa Sewer Design Guidelines and the MOE’s Design Guidelines for Sewage Works, the following criteria were used to calculate estimated wastewater flow rates and to size the sanitary sewers:

• Minimum Velocity – 0.6 m/s (0.8 m/s for upstream sections) • Maximum Velocity – 3.0 m/s • Manning roughness coefficient for all smooth wall pipes – 0.013 • Minimum size – 200mm dia. for residential areas • Average Wastewater Generation – 350L/cap/day • Peak Factor – 4.0 (Harmon’s) • Extraneous Flow Allowance – 0.28 l/s/ha (conservative value) • Manhole Spacing – 120 m • Minimum Cover – 2.5m • Population density for single-bedroom apartments – 1.4 pers./apartment • Population density for average apartments – 1.8 pers./bedroom • Population density for two-bedroom apartments (dorms) – 2.1 pers./bedroom

4.3 PROPOSED SERVICING

The anticipated wastewater peak flow generated from the total proposed development is summarized in the table below:

Table 1: Estimated Wastewater Peak Flow Residential Units Commercial Area

Infiltration Flow (L/s) # of Units Population Peak

Factor Peak Flow

(L/s) Area (ha) Peak Factor

Peak Flow (L/s)

290 470 3.89 7.60 0.21 1.50 0.18 0.12


Wastewater Servicing February 2, 2018


Total Estimated Wastewater Peak Flow (L/s): 7.90 1. Average residential flow based on 350 L/p/day and average commercial flow based on 50,000 L/ha/day

2. Peak factor for residential units calculated using Harmon’s formula and taken as 1.50 for commercial areas

3. Infiltration flow based on 0.28 L/s/ha

The Ampersand in Chapman Mills Town Centre Infrastructure Servicing Brief (DME, Revised October 2010) included a sanitary sewer design for their proposed residential development located south of Marketplace Avenue and west of Longfields Drive. DME’s sanitary sewer design sheet accounted for flow from the proposed development site and included capacities of the downstream sanitary sewer segments along Longfields Drive. Although the DME’s design sheet estimated lower wastewater flows from the proposed development, the capacity of the receiving sewers and sewers downstream demonstrate that the system has capacity in excess of the 7.90 L/s proposed sanitary discharge from Phase 1 of the site. This was previously demonstrated in the Tega Marketplace, Site Servicing Report prepared by Stantec in support of the 2014 zoning bylaw amendment.

DME’s sanitary drainage plan and design sheet that were included in the Tega Marketplace, Site Servicing Report, 2014, have been included in Appendix B.

4.4 MCGARRY TERRACE EXTENSION AND FUTURE PHASE 2

The existing municipal sanitary sewer bisecting the site and connecting to the Marketplace Avenue 250 mm diameter sanitary sewer, will be relocated along the future McGarry Terrace right of way. As can be seen on Drawing SSP-1, the existing sanitary invert on McGarry Terrace is 97.76 m while the existing sanitary invert of the manhole at the intersection of McGarry Terrace and Marketplace Avenue is approximately 97.13 m. As a result, the proposed sanitary sewer along the future McGarry Terrace ROW will run at 0.80% with greater capacity than the existing sanitary sewer crossing the site (72.1 m – 200 mm dia. at 0.74%). The invert for the sanitary sewer at McGarry Terrace has been confirmed through visual inspection and site survey. Confirmation of the invert shall be conducted prior to construction.

Design flows for future Phase 2 of the development are based on the total number of residential units and commercial floor space proposed at the time of zoning minus the number of residential units and commercial floor space proposed as part of Phase 1 of the development. The sanitary sewer design sheet for the extension of the McGarry Terrace sanitary sewer is included in Appendix B.


STORMWATER MANAGEMENT February 2, 2018


5.0 STORMWATER MANAGEMENT

5.1 OBJECTIVES

The objective of this stormwater management plan is to determine the measures necessary to control the quantity/quality of stormwater released from the proposed development to criteria established during the pre-consultation/zoning process, and to provide sufficient detail for approval and construction.

5.2 SWM CRITERIA AND CONSTRAINTS

Criteria were established by combining current design practices outlined by the City of Ottawa Design Guidelines (2012), and through consultation with City of Ottawa staff. The following summarizes the criteria, with the source of each criterion indicated in brackets:

General

• Use of the dual drainage principle (City of Ottawa). • Wherever feasible and practical, site-level measures should be used to reduce and control

the volume and rate of runoff. (City of Ottawa) • Assess impact of 100 year event outlined in the City of Ottawa Sewer Design Guidelines on

major & minor drainage system (City of Ottawa) • The proposed site is not subject to quality control criteria due to the small site size and land

usage of the development (City of Ottawa). Quality control to be provided in the downstream Chapman Mills SWM Facility.

Storm Sewer & Inlet Controls

• All stormwater runoff from the ultimate site up to and including the 100 year event to be stored on site and released into the minor system at a maximum rate equivalent to 85 L/s/ha.

• Proposed site to discharge the existing 1350mm diameter storm sewer running east along Marketplace Avenue ROW at the boundary of the subject site (City of Ottawa).

• 100-year Storm HGL to be a minimum of 0.30 m below building foundation footing (City of Ottawa).

• Use of standard self-cleansing inlet-control devices where possible.




Surface Storage & Overland Flow

• 150mm of vertical clearance to be maintained between spill elevation in the street and the ground elevation at the building envelope (City of Ottawa)

• Maximum depth of flow under either static or dynamic conditions shall be less than 0.35m in the 100-year event(City of Ottawa)

• Provide adequate emergency overflow conveyance off-site (City of Ottawa)

5.3 STORMWATER MANAGEMENT

Stormwater runoff from the proposed development will be directed to an existing 1350 mm diameter storm sewer running east along Marketplace Avenue and then south along Longfields Drive towards a diversion manhole that diverts runoff from everyday rain events to the Chapman Mills Stormwater Management (SWM) Facility for quality control and runoff from major events to a diversion trunk storm sewer that discharges directly into the Jock River. Based on the finished floor elevation of the underground parking and the elevation of the existing storm sewer on Marketplace Avenue, it is recommended that sump pumps be provided as part of the building internal plumbing system to provide drainage for foundation drains and that the proposed connections to the existing Marketplace trunk storm sewer be equipped with backwater valves. The proposed site servicing plan and existing storm sewer infrastructure on Marketplace Avenue are shown on Drawing SSP-1.

5.3.1 Existing Conditions

The entirety of the site is currently partially developed consisting of two main buildings, access and parking areas, undeveloped lands, and existing retaining walls along Marketplace Avenue. Phase 1 of the sites topography is fairly steep with grades ranging from 103.9 m on the west side of the site to 97.5 m on the east side of the site along Longfields Drive.

A 200 mm diameter sanitary sewer running at 0.74% and a 525 mm diameter storm sewer running at 0.34% currently cross the site from north to south and connect the sewers along the existing section of McGarry Terrace to the sewers along Marketplace Avenue. The two sewers will be decommissioned and the services replaced by the proposed extension within the McGarry Terrace ROW. (see Drawing SSP-1).

5.3.2 Allowable Release Rate

The Modified Rational Method was employed to assess the rate and volume of runoff generated during post-development conditions. The site was subdivided into subcatchments (subareas) tributary to stormwater controls as defined by the location of inlet control devices. A summary of




subareas and runoff coefficients is provided in Appendix C.2, and Drawing SD-1 indicates the stormwater management subcatchments.

Based on the Nepean South Chapman Mills Stormwater Management Servicing Report (IBI, revised September 2010) and confirmed through correspondence with IBI staff (see Appendix E) the subject site is to control the 100-year flow on site and the minor system for the total site will be restricted to 85 L/s/ha. Runoff coefficients (C) for the proposed catchment areas have been calculated based on actual pervious and impervious areas shown on the proposed site plan. C coefficient values have been increased by 25% for the post-development 100-year storm event based on MTO Drainage Manual recommendations. Peak flow rates have been calculated using the rational method as follows:

Q = 2.78 CiA Where: Q = peak flow rate, L/s A = drainage area, ha I = rainfall intensity, mm/hr (per Ottawa IDF curves) C = site runoff coefficient

The target release rate for the site is summarized in Table 1 below:

Table 2: Target Release Rates

Proposed Development

Area (ha)

Allowable Release Rate

(L/s/ha)

Qtarget

(L/s)

FUT - 2 0.17

85

14.5 EXT - 1 0.12 10.2 FUT - 1 0.10 8.5

Phase 1 0.56 47.6

5.3.3 Storage Requirements

The site requires quantity control measures to meet the restrictive stormwater release criteria. It is proposed that rooftop storage via restricted and sewers equipped with inlet control devices (ICDs) directed to a cistern located on the first parking level be used to reduce site peak outflow to target rates.

5.3.3.1 Rooftop Storage

It is proposed to retain stormwater on the building rooftops by installing restricted flow roof drains. The following calculations assume the roofs will be equipped with standard Watts Model RD-100_A_ADJ Accuflow Roof Drains which will be closed at either 25% or 50%.




Watts Drainage “Accutrol” roof drain weir data has been used to calculate a practical roof release rate and detention storage volume for the rooftops. It should be noted that the “Accutrol” weir has been used as an example only, and that other products may be specified for use, provided that the total roof drain release rate is restricted to match the maximum rate of release indicated in Table 2, and that sufficient roof storage is provided to meet (or exceed) the resulting volume of detained stormwater. Proposed drain release rates vary between the five rooftops. Storage volume and controlled release rate are summarized in Table 2:

Table 3: 100 Year Summary of Roof Controls

Area ID Area (m2) Depth (mm) Discharge (L/s) Volume Stored (m3)

Roof 1 880 145 4.92 32.30

Roof 2 1056 149 5.02 41.5

Roof 3 772 148 3.75 29.8

Roof 4 80 130 0.88 2.1

Roof 5 487 140 1.83 16.4

5.3.3.2 Subsurface Storage

Given that the proposed underground parking spans the entire Phase 1 site, it is proposed that runoff from the access road as well as runoff from all other surface/roof areas be captured through drains that will be connected to the internal plumbing system of the building. Due to grading restrictions on-site and the configuration of the proposed site plan, a minor area fronting Marketplace Avenue and Longfields Drive along the eastern edge of the site cannot be graded to enter the internal plumbing system of the building and will sheet drain offsite uncontrolled. As a result, the areas tributary to the internal plumbing system and ultimately to the proposed storm service connected to the 1350 mm diameter storm sewer on Marketplace Avenue need to be over-controlled in order to achieve the allowable release rate from the overall site.

In order to meet the allowable release rate for the overall site, considerable storage will be required to be provided underground. Table 4 summarizes the storage requirements for the entire site during the 100 year storm.

Table 4: 100 Year Storage Requirements and Release Rates

Areas Tributary to Proposed ICDs 100 Year Subsurface

Volume Requirements (m3)

100 Year Release Rate

(L/s) ROOF 1, ROOF 2, ROOF 3, ROOF 4, ROOF 5,

RAMP, PARKING 40.8 30.0

UNC-1 - 17.5




The overall 100 year release rate from the proposed site is equal to the sum of the internal plumbing system discharge, which will be restricted through an inlet control device (ICD) and underground storage (35 m3), plus the 100 year runoff generated by the uncontrolled area (UNC-1).

5.3.4 Results

Table 5 demonstrates the proposed stormwater management plan and demonstrates adherence to target peak outflow rates for the site.

Table 5: Phase 1 Summary 100 Year Event Release Rates

100-Year Peak Discharge (L/s)

Uncontrolled – Surface 17.5

Controlled – Subsurface 30.0

Total 47.5

Target 47.6

5.4 MCGARRY TERRACE EXTENSION AND FUTURE PHASE 2

The future McGarry Terrace extension is approximately 72 m long and will be constructed with the development of Phase 2 of the site. This section of McGarry Terrace is shown on Drawing SD-1 as area FUT-1. Phase 1 of the site development will include the construction of the storm and sanitary sewers within the future McGarry Terrace ROW.

The future McGarry Terrace roadway has been designed using the “dual drainage” principle, whereby the minor (pipe) system is designed to convey the peak rate of runoff from the 85 L/s/ha flow rate), and runoff from larger events will ultimately be conveyed by both minor (pipe) and major (overland) channels such as roadways and walkways safely off site.

Based on background reports, the SWM criteria for the proposed right of way extension are the same as for the proposed mixed-use development; 85 L/s/ha into the minor system with on-site storage for up to the 100 year storm.

Currently the storm sewer at the south end of McGarry Terrace runs along a sewer easement adjacent to and through the subject property. This section of storm sewer is being abandoned and removed. As part of these works, the existing storm sewer on McGarry Terrace is being extended along the future ROW to connect with the 1350mm sewer within Marketplace Ave. A 525mm diameter storm sewer along a length of 74m is proposed for the McGarry Terrace extension and have been included on the storm design sheet.


February 2, 2018


To contain overland flow within the Phase 2 lands and avoid oversizing stormwater storage within the current phase of development, minor grading is proposed within EXT-1 and a temporary DICB will be installed on the existing 100mm storm stub at the low point in the drainage area as shown on Drawing SD-1. An IPEX Tempest LMF model 85 ICD will be used to restrict flow to the allowable 10.2 L/s based on 85 L/s and the area of 0.12ha. Upon development of the Phase 2 lands, the DICB will be decommissioned and the stormwater managed as part of the overall Phase 2 SWM design.


GRADING AND DRAINAGE February 2, 2018


6.0 GRADING AND DRAINAGE

The proposed development site measures approximately 0.56ha in area. The topography across the site is relatively flat, and currently drains from east to west, with overland flow generally being directed to the adjacent Marketplace Avenue ROW. A detailed grading plan (see Drawing GP-1) has been provided to satisfy the stormwater management requirements, adhere to any geotechnical restrictions for the site, and provide for minimum cover requirements for storm and sanitary sewers where possible. Site grading has been established to provide emergency overland flow routes required for stormwater management in accordance with City of Ottawa requirements.

The subject site maintains emergency overland flow routes for flows deriving from storm events in excess of the maximum design event to the existing Marketplace Avenue as depicted in Drawing GP-1.


UTILITIES February 2, 2018


7.0 UTILITIES

Hydro, Bell, Gas and Cable servicing for the proposed development should be readily available within subsurface utility infrastructure within the Marketplace Avenue ROW. Exact size, location and routing of utilities, along with determination of any off-site works required for redevelopment, will be finalized after design circulation.

8.0 APPROVALS

As the existing storm and sanitary sewers that currently cross the site will need to be relocated to the future McGarry Terrace extension right of way, an amendment to the existing Ontario Ministry of Environment and Climate Change (MOECC) Environmental Compliance Approval (ECA) for the McGarry Terrace sewers. In addition, Conservation Authority approval will be required for the development to proceed.

Requirement for a MOECC Permit to Take Water (PTTW) for sewer construction and/or excavation for building construction will be confirmed by the geotechnical consultant.


Erosion Control During Construction February 2, 2018


9.0 EROSION CONTROL DURING CONSTRUCTION

Erosion and sediment controls must be in place during construction. The following recommendations to the contractor will be included in contract documents.

1. Implement best management practices to provide appropriate protection of the existing and proposed drainage system and the receiving water course(s).

2. Limit extent of exposed soils at any given time. 3. Re-vegetate exposed areas as soon as possible. 4. Minimize the area to be cleared and grubbed. 5. Protect exposed slopes with plastic or synthetic mulches. 6. Provide sediment traps and basins during dewatering. 7. Install sediment traps (such as SiltSack® by Terrafix) between catch basins and frames. 8. Plan construction at proper time to avoid flooding.

The contractor will, at every rainfall, complete inspections and guarantee proper performance. The inspection is to include:

9. Verification that water is not flowing under silt barriers. 10. Clean and change silt traps at catch basins.

Refer to Drawing ECDS-1 for the proposed location of silt fences and other erosion control structures.


GEOTECHNICAL Investigation and Environmental Assessment February 2, 2018


10.0 GEOTECHNICAL INVESTIGATION AND ENVIRONMENTAL ASSESSMENT

A geotechnical investigation was conducted by Paterson Group in November 2017. As stated in the geotechnical investigation, the subsurface profile across the site consists of a thin layer of topsoil or flexible asphaltic concrete overlying imported fill consisting of granular crushed stone and/or dense glacial till.

Groundwater levels were measured from standpipes in boreholes BH1 to BH6. Groundwater levels recorded in December 2012 for BH1 to BH3 and in April 2013 for BH4 to BH6 ranged from 2.8 to 5.3 m below the existing ground surface and are subject to seasonal fluctuations.

Practical refusal to excavation was encountered for several boreholes. Based on geological mapping for the area, bedrock in the area consists of sandstone and dolomite with an overburden drift thickness of 10 to 25 m depth.

Pavement structures for driveways and access routes to future blocks, as well as local roadways are provided in Table 6 and Table 7 below.

Table 6: Pavement Structure – Car Only Parking Areas

Thickness (mm) Material Description

50 Wear Course – HL-3 or Superpave 12.5 Asphaltic Concrete

150 Base – OPSS Granular A Crushed Stone

300 Subbase - OPSS Granular B Type II

- Subgrade – Either fill, in situ soil,selected subgrade or OPSS Granular B Type I or II material placed over

in situ soil or fill.

Table 7: Pavement Structure – Access Lanes

Thickness (mm) Material Description

40 Wear Course – HL-3 or Superpave 12.5 Asphaltic Concrete

50 Binder Course – HL-8 or Superpave 19.0 Asphaltic Concrete

150 Base – OPSS Granular A Crushed Stone

400 Subbase - OPSS Granular B Type II


GEOTECHNICAL Investigation and Environmental Assessment February 2, 2018


- Subgrade – Either fill, in situ soil, select subgrade material or OPSS Granular B Type I or II material

placed over in situ soil or fill.


February 2, 2018


11.0 CONCLUSIONS

11.1 WATER SERVICING

Based on the supplied boundary conditions for existing watermains and estimated domestic and fire flow demands for the subject site, it is anticipated that the proposed servicing in this development will provide sufficient capacity to sustain both the required domestic demands and emergency fire flow demands of the proposed site. Fire flows greater than those required per the FUS Guidelines are available for this development.

11.2 SANITARY SERVICING

The proposed sanitary sewer network is sufficiently sized to provide gravity drainage of the site. The proposed site will be serviced by a gravity sewer service lateral which will direct wastewater flows (approx. 7.90 L/s) to the existing 250mm dia. sanitary sewer within the Marketplace Avenue ROW at the southern boundary of the property. The proposed drainage outlet has sufficient capacity to receive sanitary discharge from the site.

11.3 STORMWATER SERVICING

The proposed stormwater management plan is in compliance with the criteria specified within the Nepean South Chapman Mills Stormwater Management Servicing Report (IBI, revised September 2010) and confirmed through correspondence with IBI staff. Rooftop and surface storage has been controlled and directed to a subsurface storage tank which will release an allowable 30.0 L/s to the existing 1350mm diameter storm sewer on Marketplace Avenue. The downstream receiving sewer has sufficient capacity to receive runoff volumes from the site.

11.4 GRADING

Grading for the site has been designed to provide an emergency overland flow route as per City requirements and reflects the recommendations in the Geotechnical Investigation Report prepared by Paterson Group. Erosion and sediment control measures will be implemented during construction to reduce the impact on existing facilities.

11.5 UTILITIES

Utility infrastructure exists within the Marketplace Avenue ROW at the southern boundary of the proposed site. It is anticipated that existing infrastructure will be sufficient to provide a means of distribution for the proposed site. Exact size, location and routing of utilities will be finalized after design circulation.


CONCLUSIONS February 2, 2018


11.6 APPROVALS/PERMITS

An amendment to the MOECC Environmental Compliance Approval is expected to be required for the subject site as the existing storm and sanitary sewers that currently cross the site will need to be relocated to the future McGarry Terrace extension right of way. Requirement for a MOE Permit to Take Water (PTTW) for sewer and building construction will be confirmed by the geotechnical consultant.

Site Servicing and Stormwater Management Report, 1117 ...

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