Stormwater Management Report

747 Liverpool Road Proposed Condominium Development 747 Liverpool Road, Pickering Ontario

Prepared for: Madison Liverpool Ltd 369 Rimrock Road Toronto, ON M3J 3G2 Prepared by: Stantec Consulting Ltd 300-675 Cochrane Drive West Tower Markham, ON L3R 0B8

January 14, 2016

STORMWATER MANAGEMENT REPORT

Table of Contents 1.0

INTRODUCTION/BACKGROUND .................................................................................1.1

2.0

EXISTING CONDITIONS ...............................................................................................2.3

3.0

STORMWATER MANAGEMENT CRITERIA .....................................................................3.4

4.0 4.1 4.2 4.3 4.4

STORMWATER MANAGEMENT PLAN ...........................................................................4.6 QUANTITY CONTROL ...................................................................................................... 4.6 QUALITY CONTROL ........................................................................................................ 4.8 WATER BALANCE ............................................................................................................ 4.9 SITE GRADING AND EROSION CONTROL .................................................................... 4.1 4.4.1 PROPOSED SITE GRADING AND EMERGENCY OVERLAND FLOW ......... 4.1 4.4.2 Erosion and Sediment Control ................................................................... 4.2 STORMWATER MANAGEMENT SUMMARY ................................................................... 4.3

4.5

LIST OF TABLES Table 1 - Quantity Control Summary Table ............................................................................ 4.7 Table 2 - Soil Characteristics .................................................................................................... 4.9 Table 3 – Post Development Mitigated Water Balance Site Inputs .................................. 4.10 Table 4 - SWM Summary Table................................................................................................. 4.3 LIST OF FIGURES Figure 1 – Existing Drainage Area Figure 2 - Stormwater Management Plan LIST OF DRAWINGS Drawing C-101 – Grading Plan, Prepared by Stantec Consulting Ltd. (Jan 2016). Drawing C-102 – Servicing Plan, Prepared by Stantec Consulting Ltd. (Jan 2016). Drawing C-107 – Construction Details, Prepared by Stantec Consulting Ltd. (Jan 2016). Drawing C-108 – Erosion and Sediment Control Plan, Prepared by Stantec Consulting Ltd. (Jan 2016). Drawing C-109 – Erosion and Sediment Control Details, Prepared by Stantec Consulting Ltd. (Jan 2016). APPENDICES Appendix A – City of Pickering E-mail Correspondence SWM Criteria

STORMWATER MANAGEMENT REPORT

Appendix B – Water Balance/Erosion Control Retention Calculations Appendix C – Water Quantity Calculations Appendix D – Water Quality Calculations

STORMWATER MANAGEMENT REPORT Introduction/background January 14, 2016

1.0

INTRODUCTION/BACKGROUND

This submission is to obtain site plan approval for the development of a 1.91 hectare subject residential site in the City of Pickering, Ontario. Stantec Consulting Ltd. (Stantec) has been retained by Madison Liverpool Ltd to prepare a Stormwater Management (SWM) Report in support of the Site Plan Application for the proposed 747 Liverpool Road Development. This report summarizes how the proposed design will meet the SWM water balance, water quantity and water quality requirements for the proposed residential parcel development. The site is located at 747 Liverpool Road, in the City of Pickering. It is proposed to develop 71 condominium units; made up of 14 detached units and 57 townhouse units as per the Site Plan. The subject site is shown below in Figure 1A.

Figure 1A Subject Site

To determine the SWM requirements, we have reviewed the following documents: •

Functional Servicing and Stormwater Management Report, 747 Liverpool Road Condominium, prepared by Stantec Consulting Ltd. (January 2016).

•

City of Pickering Stormwater Management Design Guidelines, prepared by the City of Pickering.

•

City of Pickering e-mail correspondence with City Engineering Staff (October 26, 2015 – November 3, 2015) regarding SWM Criteria.

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1.1

STORMWATER MANAGEMENT REPORT Introduction/background January 14, 2016

•

Stormwater Management Planning and Design Manual, prepared by the Ministry of Environment and Climate Change (March 2003).

•

Wet Weather Flow Management Guideline (WWFMG), prepared by the City of Toronto November (2006).

•

Plan of Topographic Detail Block Q, Registered Plan M-15, Town of Pickering Regional Municipality of Durham, prepared by Donevan Fleischmann Petrich Ltd. Ontario Land Surveyors (March 20, 2013).

•

Proposed Common Element Freehold Townhouse Single-Detached House Development, Liverpool Rd. Pickering Ontario, Site Plan Drawing 15-1293-SP2 ‘Site Plan’, prepared by Flanagan Beresford and Patteson Architects (Revised Dec 1, 2015).

•

Draft Preliminary Geotechnical Investigation Report for Proposed Residential Development 747 Liverpool Road, Pickering, Ontario, (Preliminary Geotechnical Investigation Report), prepared by Amec Foster Wheeler (October 9, 2015)

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1.2

STORMWATER MANAGEMENT REPORT Existing conditions January 14, 2016

2.0

EXISTING CONDITIONS

The 1.91 hectare subject site is currently occupied by an existing school building, open grassed field and portables. It is understood that the main school building and portables will be demolished by others. Figure 1 represents the existing drainage conditions. Currently the site has three main subcatchments flowing to two separate outlets: Liverpool Road and Commerce Street. •

Existing Catchment 101 is comprised of an existing school building, portables and open grassed field that drain in a westerly direction via a combination of overland sheet flow and storm sewer to the municipal drainage system on Liverpool Road, which drains to Ilona Park Road and ultimately to Frenchman’s Bay.

•

Existing Catchment 102 is an open field that sheet flows in a southwesterly direction to Commerce Street and then ultimately drains to Frenchman’s Bay.

•

Existing Catchments 103A and 103B are existing external single residential lots to the north and east of the site that drain (rear lot areas only) through the subject property to Liverpool Road.

•

Existing Catchment 103C is also an existing external residential area at the southeast corner of the site that drains (rear lot areas only) through a grassed park area to Commerce Street.

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2.3

STORMWATER MANAGEMENT REPORT Stormwater management criteria January 14, 2016

3.0

STORMWATER MANAGEMENT CRITERIA

The site is subject to the criteria as laid out by the City of Pickering Stormwater Management Guidelines and supplemental information provided in the City of Pickering SWM Criteria Correspondence Email (refer to Appendix A): “The stormwater management (swm) criteria for this site has been discussed internally, and the City has determined that the following swm criteria shall be applied: 1. The quantity control criteria is to control 100 yr post-development flow to the 5 yr predevelopment (existing) flow. The 5 yr pre-development flow shall be calculated using the following: • • •

Runoff coefficient of 0.75. IDF parameters A of 2464 and B of 16. Pre-development (existing) conditions drainage area (western portion of the site) shall be determined based on the recent survey information.

2. Enhanced level of Quality control (80% TSS removal). 3. Minimum Erosion control criteria is 5mm on site retention/infiltration.” Under post development conditions, the site will drain west to an existing manhole at the intersection of Liverpool Road and Ilona Park Road, prior to discharging to an existing 600 mm diameter storm sewer on Ilona Park Road. In summary, the following criteria must be adhered to for the subject site: •

100 year post development flow match the 5 year pre-development flow for the north portion of the site (identified as Existing Catchment 101 (1.15 ha) on Figure 1) which currently drains to Liverpool road.

•

Flow from Catchment 102 originally draining to Commerce Street must now be captured and directed to Liverpool Road. Since the addition of flow cannot discharge to Liverpool for a built site condition, this catchment essentially has a “zero” outflow under post development and as such additional storage has been provided onsite to over control for this area.

•

An area of 0.26 ha of residential external flow drains through the subject site (shown as Catchment areas 103A and 103B on Figure 1) under existing conditions and will continue to do so under the post development scenario. This external flow has been accounted for in the pre-development flow target establishment.

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3.4

STORMWATER MANAGEMENT REPORT Stormwater management criteria January 14, 2016

•

Flow from Catchment 103C originally drained towards Commerce Street and will continue to do so by draining south along the proposed retaining wall at the south eastern limits of the site.

As mentioned above, the pre-development flow for the south portion of the site, identified as Catchment 102 (0.76 ha) on Figure 1 currently drains to Commerce Street. As directed by the City, under post-development the site must be ‘self-contained’ and cannot outlet to the property south of the site. Thus, Catchment 102 will be redirected to Liverpool Road. A retaining wall structure will be built along the rear portions of the south lots which will act to trap drainage and direct flow to rear lot catch basins. As such, Catchment 102 has not been included in the pre-development flow calculations and additional storage will be provided onsite to overcontrol this flow that is now directed to Liverpool Road. In summary, the 5 year pre-development flow for Catchment 101 was determined to be 227 l/s (minor system flow allowable in the storm sewer) and the 100 year external area target flow for Catchments 103A and 103B was determined to be 101 l/s (major overland flow), which results in an overall pre-development flow target of 328 l/s. The target flows were calculated using the Rational Method and a runoff coefficient of 0.75 for Catchment 101, as directed by City Engineering Staff. External Catchment areas 103A and 103B used a standard residential runoff coefficient of 0.60 (single family home) and was scaled-up to 0.75 for the 100 year storm event as per the City of Pickering SWM Design Guidelines. Refer to Figure 2 for post-development Catchment Areas. Calculations are provided in Appendix C. The time of concentration for the existing site has been established at 10 minutes. The time of concentration flow path is shown on Figure 1. Note that per the City of Pickering Engineering Stormwater criteria, the Kinematic wave equation was used to determine the site time of concentration, which resulted in an overall time of 9.9 minutes, which was rounded up to the typical municipal minimum standard time of 10 minutes. Calculations are provided in Appendix C. City Engineering Staff (Irina Marouchko) also confirmed via phone conversation that Oil Grit Separator (OGS) units are given an 80% Total Suspended Solids (TSS) removal efficiency credit and as such would be capable of achieving the site water quality objectives as a standalone device.

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3.5

STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

4.0

STORMWATER MANAGEMENT PLAN

4.1

QUANTITY CONTROL

Figure 2 illustrates controlled, uncontrolled and external drainage areas of the storm drainage plan. Below is a summary of the catchment areas: •

Post Development Catchment Area 101 and external Catchment Areas 103A and 103B are the areas of the site that will be controlled to a flow of 222 l/s through a 270 mm orifice as outlined in Table 1 below. Catchment area 101 is made up of Townhouses and Single residential homes with an overall weighted runoff coefficient of 0.73. Catchment Area 103 is made up of Catchment Area 103A and 103B and is an external area that will be conveyed through the site. The catchment is made up primarily of existing detached single family homes and has been assumed to have a runoff coefficient of 0.60 and a 100 year time of concentration of 10 minutes. Refer to Appendix C for calculations.

•

Post Development uncontrolled Catchment Area 102 is made up of areas 102A, 102B and 102 C, which results in a flow of 101 l/s. Catchment Areas 102A and 102B are the uncontrolled drainage areas from the townhouses and rear yard landscape areas draining to Liverpool Road. It has been assumed that half of the roofs drain towards the rear lots. Catchment Area 102C includes a small portion of uncontrolled drainage from the internal road and boulevard area adjacent to Liverpool Road, near the site entrance. The runoff coefficient for Catchment Area 102 is 0.75. Refer to Appendix C for calculations.

The site will be controlled to the allowable release rate by using a 270 mm diameter orifice plate welded and bolted at the upstream end of Control Manhole 16, which is located at the downstream end of the internal pipe network system, near the site entrance. The total outflow from this orifice during the 100 year event is 222 l/s, which is less than the allowable minor system release rate of 227 l/s. When the 100 year orifice flow is added to the uncontrolled runoff areas fronting onto Liverpool Road, the total site release rate is 323 l/s which is less than the allowable total site release rate of 328 l/s. A summary of the target discharge, storage requirements and design discharge rates are summarized in Table 3 below. The storage requirements were calculated using the Modified Rational Method. The amended soils provide a reduction in stormwater runoff volume during a 100 year storm event. The amended soils are capable of providing a minimum of 95.5 m3 of runoff volume reduction during a 100 year storm event, which corresponds to an equivalent capture depth of 5 mm. Since 150 mm of amended topsoil is being placed onsite, there is actually an equivalent calculated depth of 6.28 mm available which results in 120 m3 of storage. As such, 95.5 m3 was conservatively used and subtracted from the maximum required storage

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

value as determined using the Modified Rational Method, yielding a reduced stormwater storage detention requirement. Calculations are provided in Appendix C. As a result, the overall 100 year required detention storage for the site is 376 m3 and the storage provided is 409 m3. Storage will be provided using oversized storm sewers and manhole storage (all provided onsite). All site storm sewers have been upsized to 975 mm diameter pipes to accommodate the 100 year storm event storage requirements. Refer to Figure 2, Drawing C-101 (Site Grading Plan) and Drawing C-102 (Site Servicing Plan).

Table 1 - Quantity Control Summary Table 100 Year Event Release Rates and Storage

Catchment ID

Runoff Coef.

Area (ha)

Storage Required (m3)

Storage Provided (m3)

101+103 102

0.89 0.94

2.01 0.21

376 --

409 --

2.22

376

409

Total

Catchment 101 + 103 Allowable Release Rate (l/s)

Release Rate (l/s)

222 101 328

323

Note: Catchment 101 is controlled flow from the Site to Liverpool Road. Catchment 103 is external flow to Liverpool Road. Catchment 102 is uncontrolled flow from the Site to Liverpool Road. The Runoff Coefficients have been scaled-up by 1.25 for the 100 year event per the City of Pickering Stormwater Management Design Guidelines.

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

4.2

QUALITY CONTROL

The site has an overall weighted imperviousness of 73%. Site water quality control will be provided for the majority of the site with an Oil/Grit Separator (OGS) Stormceptor STC 6000 (or approved equivalent) installed at the outlet of the site in Control Manhole 16 (refer to servicing Drawing C-102). A small portion of the site is comprised of uncontrolled areas which cannot be directed through the OGS unit; specifically Catchments 102 A and 102 B, which are rooftop and grass areas that are considered to be areas of clean runoff (refer to Figure 2). As mentioned above in Section 3.0, City of Pickering Engineering staff indicated that an OGS unit acting alone is capable of achieving the site water quality objective of 80% TSS removal. Quality Control calculations are provided in Appendix D.

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

4.3

WATER BALANCE

A water balance model was used to determine the runoff and infiltration for the site for the postdevelopment with mitigation condition to ensure that the first 5 mm of rainfall was captured for the erosion control criterion. The site area is 1.91 ha and 5 mm of rainfall over this site is equivalent to 95.5 m3 of rain that must be captured. Based on the Preliminiary Geotechnical Investigation Report (provided under separate cover), native clayey silt was encountered below the topsoil or asphaltic concrete and fill soils in Boreholes BH1, BH3, BH5 and BH6 extending to a depth of 2.2 m below the existing ground surface. The infiltration rate of these native soils may not be ideal, therefore Amended soil was proposed for the site to allow for additional capture using the landscaped areas onsite. Amended soil is topsoil with additional materials added to increase infiltration and capture capacity. Typically, amended soils are sandier than topsoil and the amendment changes the typical soil characteristics such as porosity, field capacity, wilting point, and infiltration rate. Error! Reference source not found. below shows the soil characteristics for both topsoil and amended soil.

Table 2 - Soil Characteristics Soil Characteristic

Typical

Amended

Topsoil

Soil

Porosity

0.35

0.53

Field Capacity

0.15

0.32

Wilting Point

0.10

0.13

1.5-3.5

30-70

Infiltration rate (mm/hr)

For this analysis a 40 mm, 4-hour Chicago storm was used as the design rainfall event. This storm is considered to represent a typical year’s maximum event rainfall for the City of Toronto (refer to WWFMG) considered to be fairly representative of rainfall distributions for southern Ontario, and using this storm demonstrates that the amended soil can capture a minimum of 5 mm from most rainfall events observed during the year. The water balance spreadsheet used for this analysis tracks the volume of water in each part of the system (surface runoff, soil, and groundwater) during each time-step. For the mitigated postdevelopment scenario it was assumed that only the roof runoff could be captured by the amended soils and as such downspouts for all roofs will be disconnected and directed to grade. The water balance spreadsheet uses the rainfall, soil characteristics, and drainage areas to calculate the volume of water for each of the following, for every time-step:

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

•

Rain water onto pervious;

•

Unsaturated runoff;

•

Rain into amended soil;

•

Beginning of time-step amended soil water volume (initial value is set to field capacity);

•

Water from amended soil to ground water;

•

Water that does not exfiltrate;

•

Water that stays in the amended soil;

•

Saturated runoff; and

•

Total runoff.

The inputs for the post-development mitigated water balance can be seen in Error! Reference source not found., below.

Table 3 – Post Development Mitigated Water Balance Site Inputs Parameter

Value

Unit

Roof Area

7,300

Sq. m

Landscaped/Grassed Area

6,900

Total Area

14,200

Soil Depth

100

Soil Exfiltration Rate

1

Soil Porosity

0.53

Soil Field Capacity

0.32

Soil Wilting Point

0.13

Soil Infiltration Rate

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30

Sq. m

Sq. m mm mm/hr

mm/hr

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

The soil exfiltration rate is the rate at which the native soil below the amended soil can accept water. This was chosen to be 1 mm/hr to be a conservative estimate for poorly draining soils. Water can be infiltrated on these soils; it just takes longer to infiltrate large amounts. The soil infiltration rate is the rate at which the amended soil can accept water. Typically amended soil has an infiltration rate of 70 mm/hr or higher, but 30 mm/hr is used in the water balance to account for any diminishment of infiltration capacity due to sediment or soil bind-off over the life time of the Low Impact Development (LID) measure. The soil depth is the depth of the amended soil and it is this value that is varied to achieve the 5 mm capture for the site. The recommend depth of 150 mm of amended soil captures 120 m3 prior to any saturated or unsaturated runoff. This is more than the required 95.5 m3 and is equivalent to 6.28 mm of rainfall depth over the entire 1.91 ha site area. Refer to Appendix B for detailed water balance/erosion control infiltration calculations.

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

4.4 4.4.1

SITE GRADING AND EROSION CONTROL PROPOSED SITE GRADING AND EMERGENCY OVERLAND FLOW

The grading design for the subject site has been produced based on the Site Plan prepared by FBP Architects and a Topographic Survey (Survey) prepared by DFP Surveyors dated April 9, 2013. As an infill, site perimeter grades are governed by the existing surrounding properties, and Liverpool Road to the West. The existing grading of the site gently slopes from the northeast to the southwest corners of the site with grades ranging from 84.5 m to 81.5 m. Based on the information provided in the Survey, lots along the North and East boundaries appear to be split draining lots which indicates the site conveys some external flows from these external areas. The subject site is proposed to be graded such that drainage will be self-contained, with an additional 0.31 ha of assumed external drainage from adjacent lots. Due to grading constraints, a small portion, 0.15ha of the site, lots backing onto Liverpool Road, drain across the boulevard onto Liverpool Road. In order to contain the drainage, the site is proposed to be raised at locations along the property line where flows would otherwise drain onto adjacent properties. This requires the installation of retaining walls for portions of the north, east and south boundaries, where the site perimeter grades are higher than the existing perimeter grades. The retaining wall varies from 0.2 m to 2.5 m in height. Road grade design varies from 0.5% to a maximum of 2.2% which is within the Region of Durham’s design specifications. Lot drainage is typically split or front drainage for detached lot types, and all townhouse blocks are designed as split drainage lots. All split type lots will require rear yard swales and rear lot catch basins to contain flows within the site. Rear yard drainage swales are proposed at 1.0% with a sub-drain, due to the relatively flat nature of the site. The proposed grading design has been completed in accordance with the design requirements of the City of Pickering and Region of Durham. The grading design aims to achieve the following: • • • • • •

Minimize the need for engineering fill; Minimize the import of fill operations; Contain all site drainage and convey to Liverpool; Achieve standard sewer and watermain cover; Match existing boundary grades along the property limits; and, The site grading will be designed in such a way that 100 year runoff will be captured via road and rear lot catch basins and a network of oversized storm sewers. In the event of a storm sewer blockage overland flow routes have been provided within the site right of way areas, which will convey water overland and direct it towards the site outlet at Liverpool Road. (refer to Figure 2 for emergency overland flow route location and Appendix C for calculations).

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STORMWATER MANAGEMENT REPORT Stormwater management plan January 14, 2016

The proposed grading design has been completed in accordance with the design requirements of the City of Pickering and Region of Durham. The proposed grading design can be seen in Drawing C-102.

4.4.2

Erosion and Sediment Control

Prior to the initiation of any construction within the site, a comprehensive Erosion and Sediment Control (ESC) program acceptable to the City of Pickering, Region of Durham and the TRCA must be implemented. Refer to Erosion and Sediment Control Drawings C-108 and C-109. The ESC plans propose a design of siltation control facilities which follows current City guidelines and the requirements of TRCA (Greater Golden Horseshoe Erosion and Sediment Control Guideline for Urban Construction, December 2006). Below is a list of erosion and sediment control measures that will be installed and maintained during the construction of the Subject Site: •

Temporary sediment control fences will be placed prior to grading;

•

Surface runoff conveyed through temporary interceptor swales throughout site with rock check dams;

•

CB riser drains installed throughout the Site during the post-servicing phase;

•

A temporary bulkhead will be installed in the control MH 16 near the outlet of the site to reduce release of any on captured sediment to the city’s storm sewer system;

•

All proposed open space areas will be restored with topsoil and vegetation as per the landscape restoration planting plan upon completion of grading.

All temporary erosion and sediment control measures will be routinely inspected and repaired during construction. Temporary controls will not be removed until the areas they serve are restored and stable.

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4.2

APPENDIX A – CITY OF PICKERING E-MAIL CORRESPONDENCE SWM CRITERIA

From: Marouchko, Irina [mailto:[email protected]] Sent: Tuesday, November 03, 2015 12:59 PM To: Johnson, Roy (Markham) Subject: RE: 747 Liverpool Road (Madison Homes)

Correct. Irina Marouchko Water Resources Engineer | Engineering & Public Works Department 905.420.4660 ext. 2072 | 1.866.683.2760 | TTY. 905.420.1739 [email protected]

Your City. Right Now. pickering.ca

From: Johnson, Roy (Markham) [mailto:[email protected]] Sent: November-03-15 12:53 PM To: Marouchko, Irina Subject: RE: 747 Liverpool Road (Madison Homes) Thanks. With respect to the “Pre-development (existing) conditions drainage area (western portion of the site) shall be determined based on the recent survey information.”, am I correct in taking this to mean that the target should only be based on what drains west to Liverpool road via catchbasin and overland, and not any area draining south to the park?

Roy Johnson, B. Eng., M. A. Sc., P. Eng. Senior Water Resources Engineer Stantec 300W-675 Cochrane Drive Markham ON L3R 0B8 Phone: (905) 415-6372 Fax: (905) 474-9889 [email protected]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.


Please consider the environment before printing this email. From: Marouchko, Irina [mailto:[email protected]] Sent: Tuesday, November 03, 2015 12:32 PM To: Johnson, Roy (Markham) Subject: RE: 747 Liverpool Road (Madison Homes)

That is right.

Irina Marouchko Water Resources Engineer | Engineering & Public Works Department 905.420.4660 ext. 2072 | 1.866.683.2760 | TTY. 905.420.1739 [email protected]

Your City. Right Now. pickering.ca

From: Johnson, Roy (Markham) [mailto:[email protected]] Sent: November-03-15 12:22 PM To: Marouchko, Irina Subject: RE: 747 Liverpool Road (Madison Homes) So, C is 1.00 and time is in minutes? Roy Johnson, B. Eng., M. A. Sc., P. Eng. Senior Water Resources Engineer Stantec 300W-675 Cochrane Drive Markham ON L3R 0B8 Phone: (905) 415-6372 Fax: (905) 474-9889 [email protected]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.


Please consider the environment before printing this email. From: Marouchko, Irina [mailto:[email protected]] Sent: Tuesday, November 03, 2015 12:21 PM To: Johnson, Roy (Markham) Subject: RE: 747 Liverpool Road (Madison Homes)

Hi Roy, The intensity for the 5 year flow should be calculated as follows: I=2464/(T+16). Regards, Irina Marouchko Water Resources Engineer | Engineering & Public Works Department 905.420.4660 ext. 2072 | 1.866.683.2760 | TTY. 905.420.1739 [email protected]

Your City. Right Now. pickering.ca

From: Johnson, Roy (Markham) [mailto:[email protected]] Sent: November-03-15 12:13 PM To: Marouchko, Irina Subject: RE: 747 Liverpool Road (Madison Homes) Hi Irina: For the 5 year “old” IDF, what is the C value? The A value seems high, as well. The current 5 year I sA=1082.901, B = 6.007, C = 0.837 Roy Johnson, B. Eng., M. A. Sc., P. Eng. Senior Water Resources Engineer Stantec 300W-675 Cochrane Drive Markham ON L3R 0B8 Phone: (905) 415-6372 Fax: (905) 474-9889 [email protected]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.


Please consider the environment before printing this email. From: Marouchko, Irina [mailto:[email protected]] Sent: Friday, October 30, 2015 9:19 AM To: Johnson, Roy (Markham) Cc: Blommers, James; Helgesen, Paal Subject: RE: 747 Liverpool Road (Madison Homes)

Hi Roy, The stormwater management (swm) criteria for this site has been discussed internally, and the City has determined that the following swm criteria shall be applied: 1. The quantity control criteria is to control 100 yr post-development flow to the 5 yr

pre-development (existing) flow. The 5 yr pre-development flow shall be calculated using the following: • Run off coefficient of 0.75. • IDF parameters A of 2464 and B of 16. • Pre-development (existing) conditions drainage area (western portion of the site) shall be determined based on the recent survey information. 2. Enhanced level of Quality control (80% TSS removal).

3. Minimum Erosion control criteria is 5mm on site retention/infiltration.

Regards, Irina Marouchko Water Resources Engineer | Engineering & Public Works Department 905.420.4660 ext. 2072 | 1.866.683.2760 | TTY. 905.420.1739 [email protected]

Your City. Right Now. pickering.ca

From: Johnson, Roy (Markham) [mailto:[email protected]] Sent: October-28-15 5:31 PM To: Marouchko, Irina Cc: Blommers, James Subject: RE: 747 Liverpool Road (Madison Homes) Hi Irina: Thank you for the response on my question. I wanted to clarify a few items: 1. Quantity Control Requirements; and 2. “Pre-development conditions area located within Bay Ridges watershed.” Quantity Control You noted the requirement to establish a 100-year target based on 5-year storm sewer capacity, as opposed to matching post to pre for all storms. MMM Group met with Paul Helgesen of the City to discuss the capacity of existing storm sewers surrounding the site, design criteria for the site and general development requirements. MMM prepared a due diligence report for the new site owner and summarized the Storm requirement as follows: Where watershed water quantity control criteria exist the proposed development will be required to comply with the recommendations. In areas without watershed water quantity control criteria it is the policy of the City to require that post-development peak flows are controlled to pre-development levels for the 2-year through 100-year events (underlining added). This would indicate to me post to pre for each storm, not controlling 100-year post to 5-year sewer capacity. This is also my understanding based on a review of Section 4.1 Water Quantity Control Criteria of the City of Pickering Stormwater Management Guidelines. TRCA indicates that “The site appears to drain to municipal infrastructure. If this is the case, municipal quantity requirements would govern. However, if the site ultimately outlets to a tributary leading to Frenchman's bay TRCA would urge that 2 - 100 yr post-to-pre be met as closely as possible, understanding that it may be difficult without a SWM pond. If the site ultimately drains directly to Frenchman's bay, the municipal requirement would be the only requirement.”

As that difference (post to pre vs 100-year post to 5 year sewer capacity) has a significant impact on the private infrastructure, would you be able to confer with your colleague to ensure that I correctly understand the applicable quantity control criteria? Bay Ridges watershed Can you please expand your explanation on this item? What is the Bay Ridges watershed predevelopment condition we need to assess? Regards; Roy Johnson, B. Eng., M. A. Sc., P. Eng. Senior Water Resources Engineer Stantec 300W-675 Cochrane Drive Markham ON L3R 0B8 Phone: (905) 415-6372 Fax: (905) 474-9889 [email protected]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.


Please consider the environment before printing this email. -----Original Message----From: Marouchko, Irina [mailto:[email protected]] Sent: Monday, October 26, 2015 4:19 PM To: Johnson, Roy (Markham) Subject: RE: 747 Liverpool Road (Madison Homes) Hi Roy, The quantity control criteria for this site is to control 100 yr post-development flows to the allowable capacity in the existing storm sewer during 5 yr storm event. Since the drainage area plan is not available, the allowable capacity should be calculated for the pre-development conditions area located within Bay Ridges watershed using "old" IDF parameters. Regards, Irina Marouchko Water Resources Engineer | Engineering & Public Works Department 905.420.4660 ext. 2072 | 1.866.683.2760 | TTY. 905.420.1739 [email protected]

Your City. Right Now. pickering.ca

-----Original Message----From: [email protected] [mailto:[email protected]] On Behalf Of [email protected]

Sent: October-26-15 3:21 PM To: Marouchko, Irina Subject: 747 Liverpool Road (Madison Homes) Hi Irina: I wanted to confirm that the quantity control criteria for this site is control of the post development flows to the pre-development (existing) conditions, i.e. 100-year post to 100-year existing, 5-year post to 5-year existing, etc. The TRCA indicates that "The site appears to drain to municipal infrastructure. If this is the case, municipal quantity requirements would govern. However, if the site ultimately outlets to a tributary leading to Frenchman's bay TRCA would urge that 2 - 100 yr post-to-pre be met as closely as possible, understanding that it may be difficult without a SWM pond. If the site ultimately drains directly to Frenchman's bay, the municipal requirement would be the only requirement." As the site will drain to the storm sewer ultimately outletting at Frenchman's Bay, I would interpret that to mean municipal criteria governs. Regards; Roy Johnson ------------------------------------Origin: https://www.pickering.ca/en/contacts/search.aspx?s=qu31Zi5lA5HPyBC2mbBnNbjz0AeQuAleQ uAl ------------------------------------This email was sent to you by Roy Johnson through http://www.pickering.ca/.

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APPENDIX B – WATERBALANCE/EROSION CONTROL RETENTION CALCULATIONS

Area's available for Mitigative LID Measures Only use roofs as impervious surface, other impervious areas may not drain to amended soil Landscape Road Roof Driveways Total Lots 0.69 0.405 0.717 0.100 1.91

Paved Area Lawn Area Total area: Trench surf. area: Trench depth: Trench porosity: Trench full: Trench initial vol: Subsoil exfil. rate: Soil depth: Soil porosity: Soil field cap: Soil wilt point: Soil infil. rate

Amended Soil 7,168 6,882 14050 0 0 0.35 0 0 1 150 0.53 0.32 0.13 30

Soil wilt point vol: Soil porosity vol: Soil field cap vol: Soil initial vol:

134.1990 547.1190 330.336 330.336

sq.m sq.m sq.m m

Summary Amended Soil Total evaporation 0.0 cu.m Total exfiltration 250.0 cu.m Total drainflow 0.0 cu.m Total runoff 311.9 cu.m

cu.m cu.m mm/hr mm

Sum Total rainfall % Treated % untreated % Captured Effective Impervious Area

mm/hr cu.m cu.m cu.m cu.m

561.9 cu.m 561.9 cu.m 44.5% 55.5% 44.5% 55.5%

Amended Soil

All in milimeters Cumulative Cumulative mm Captured mm Captured Prior to any Runoff Prior to any Runoff

All in cubic metres Rain Water onto pervious 12/31/1975 23:00 1/1/1976 0:00 1/1/1976 0:10 1/1/1976 0:20 1/1/1976 0:30 1/1/1976 0:40 1/1/1976 0:50 1/1/1976 1:00 1/1/1976 1:10 1/1/1976 1:20 1/1/1976 1:30 1/1/1976 1:40 1/1/1976 1:50 1/1/1976 2:00 1/1/1976 2:10 1/1/1976 2:20 1/1/1976 2:30 1/1/1976 2:40 1/1/1976 2:50 1/1/1976 3:00 1/1/1976 3:10 1/1/1976 3:20 1/1/1976 3:30 1/1/1976 3:40 1/1/1976 3:50 1/1/1976 4:00 1/1/1976 4:10 1/1/1976 4:20 1/1/1976 4:30 1/1/1976 4:40 1/1/1976 4:50 1/1/1976 5:00 1/1/1976 5:10 1/1/1976 5:20 1/1/1976 5:30 1/1/1976 5:40 1/1/1976 5:50 1/1/1976 6:00

Precip (mm) 0.55 0.60 0.67 0.77 0.90 1.11 1.52 2.87 13.39 3.56 2.21 1.68 1.39 1.19 1.05 0.95 0.87 0.80 0.75 0.70 0.66 0.63 0.60 0.5696 0 0 0 0 0 0 0 0 0 0 0 0 0

Unsaturated Runoff

ETO 7.8 8.5 9.5 10.8 12.7 15.6 21.3 40.4 188.1 50.1 31.0 23.6 19.5 16.7 14.8 13.3 12.2 11.3 10.5 9.8 9.3 8.8 8.4 8.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 153.7 15.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Rain into Soil 0 7.8 8.5 9.5 10.8 12.7 15.6 21.3 34.4 34.4 34.4 31.0 23.6 19.5 16.7 14.8 13.3 12.2 11.3 10.5 9.8 9.3 8.8 8.4 8.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

beginning Soil Water Water from Soil Volume to GW 330.336 0.00 330.3 6.9 331.2 1.1 338.6 1.1 346.9 1.1 356.5 1.1 368.0 1.1 382.5 1.1 402.7 1.1 436.0 1.1 469.3 1.1 502.5 1.1 532.4 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 547.1 1.1 546.0 1.1 544.8 1.1 543.7 1.1 542.5 1.1 541.4 1.1 540.2 1.1 539.1 1.1 537.9 1.1 536.8 1.1 535.6 1.1 534.5 1.1 533.4 1.1

Water that does not exfiltrate 0 0.9 7.3 8.3 9.6 11.5 14.5 20.2 33.3 33.3 33.3 29.9 22.4 18.3 15.6 13.7 12.2 11.0 10.1 9.3 8.7 8.1 7.6 7.2 6.9 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1

Water that Stays in Soil 0 0.9 7.3 8.3 9.6 11.5 14.5 20.2 33.3 33.3 33.3 29.9 14.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1 -1.1

Saturated water that runsoff 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 18.3 15.6 13.7 12.2 11.0 10.1 9.3 8.7 8.1 7.6 7.2 6.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Total Runoff 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 153.7 15.7 0.0 7.7 18.3 15.6 13.7 12.2 11.0 10.1 9.3 8.7 8.1 7.6 7.2 6.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Evaporation 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.4 0.9 1.3 1.9 2.6 3.4 4.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.4 0.9 1.3 1.9 2.6 3.4 4.5 6.3 8.1 9.9 11.5 12.8 13.8 14.7 15.4 16.1 16.8 17.4 17.9 18.4 18.9 19.4 19.8 20.2

APPENDIX C – WATER QUANTITY CONTROL CALCULATIONS

Site: Job No.:

747 Liverpool Road 160622366

5 Year Existing Time of Concentration Calculations for Catchment 101 As per the City of Pickering SWM Guidelines:

L S n I

96.25 m 0.02 m/m 0.05 0.09 mm/hr

tti

8.36 mins

Assume Existing Pipe Length Assumed Existing Pipe Velocity Pipe Travel Time

140 m 1.5 m/s 1.56 mins

Assumed Existing Time of Concentration

9.91 mins

Assumed Minimum Existing Time of Concentration

10 mins

Refer to Figure 1 for time of concentration Flow Path

V:\01606\Active\160622366\Analysis\SWM\LATEST_CALCS\Adjusted Quantity Control for External\summary parking lot storage.xls

Site: Job No.:

747 Liverpool Road 160622366

Site Allowable Release Rate

IDF Parameters

a = 2464 t = 10

Runoff Coefficient:

b = 16.00 c= 1 C1 = 0.75

min

5 Year storm Rainfall Intensity as per information provided by City for "old" IDF data Refer to Appendix A

Allowable Release Rate Calculation Catchment ID

Area ha

101 EXIST

time

Intensity

Flow

t

i=a/(t+b)^c

min

mm/hr

Q=CiA/360 3 m /s

94.77

0.227

1.15 10.00 * a,b,c's as per Pickering, ON

747 Liverpool Road External Area Catchment 103A and 103B Allowable Release Rate a= t= b= c= C1 =

IDF Parameters

Runoff Coefficient:

2096.425 10 6.49 0.863 0.75

min

100 Year storm Rainfall Intensity asper City of Pickering SWM Guidelines Singles Runoff Coefficient Scaled by 1.25 as per City of Pickering SWM Guidelines

Allowable Release Rate Calculation Outlet ID

Area

time

Intensity

Flow

t

i=a/(t+b)^c mm/hr

Q=CiA/360 m 3 /s

ha

min

103 A +103 B EXIST

0.26

10.00

186.69

0.101

Site Total Allowable Release Rate

0.328

*Existing Catchment 102 and 103C are not used to establish allowable flow rates to Liverpool Road because they currently do not flow there *Existing Catchment 103A and 103 B time of concentration has been assumed to be a minimum of 10 minutes * a,b,c's as per Pickering, ON per City of Pickering SWM Guidelines:

V:\01606\Active\160622366\Analysis\SWM\LATEST_CALCS\Adjusted Quantity Control for External\summary parking lot storage.xls

Site: Job No.:

747 Liverpool Road 160622366

Post Development Runoff Coefficient Calculation

WEIGHTED RUNOFF COEFFICIENT Controlled Area Catchment 101 Runoff Weighted Runoff Coefficient Coefficient Area (ha) Singles Townhouses

TOTAL

0.65 0.75

0.35 1.35 1.70

0.14 0.59 0.73

*14 lots approximately 243 m2 each

WEIGHTED RUNOFF COEFFICIENT Controlled Area Catchment 101 + External Area Catchment 103 Runoff Weighted Runoff Coefficient Coefficient Area (ha) Catcment 101 0.73 1.70 0.62 Singles 0.60 0.31 0.09 2.01 0.71 TOTAL WEIGHTED RUNOFF COEFFICIENT Controlled Area Catchment 101 + External Area Catchment 103 + Uncontrolled Area Catchment 102C Runoff Weighted Runoff Coefficient Coefficient Area (ha) Catcment 101 0.73 1.70 0.60 Singles 0.60 0.31 0.09 Townhouse 0.75 0.05 0.02 TOTAL 2.06 0.69

Site: Job No.:

747 Liverpool Road 160622366

1/12/2016 15:07

Orifice Equation: Q = CdA(2gh)1/2

100 Year Runoff Coef.

Area (ha)

Release Rate (l/s) 1

Storage Required (m3) 1

Ponding Depth (m)

Storage Available (m3) 3

0.89 0.94

2.01 0.21

222 101

376 0

0.00 0.00

409 0

270 uncontrolled

222 -

2.22

323

376

-

409

-

-

101 + 102 Allowable Release Rate 101 + 102 + 103 Allowable Release Rate

227 328

Catchment ID

101 + 103 102 Total

Building No. 2

Orifice Size (mm) 4

Orifice Uncontrolled Release Rate Release Rate (l/s) (l/s)

101

Location of Orifice

Water Level (m)

Head (m)

Invert

HORIZONTAL/ VERTICAL/TUBE Control

MH16 0.0

82.4 0.0

2.0 0.2

80.280 -

vertical -

-

-

-

l/s l/s

Notes: 1

As per Modified Rational Calculations

4

See Appendix B for orifice plate details

Post Development Runoff Coefficients have been scaled by 1.25 for the 100 year event as Per City of Pickering Stormwater Management Design Guidelines

V:\01606\Active\160622366\Analysis\SWM\LATEST_CALCS\Adjusted Quantity Control for External\summary parking lot storage.xls

MOD_RTNL 100.xls 12/21/2015 16:25

Modified Rational Method Project Name : 747 Liverpool Road Area ID: 101+103 Project No. : 160622366 Area = "C" = AC= Tc = Time Increment = Release Rate = Max.Storage =

2.01 0.89 1.78 10.0 5.0 221.5 376

katwil

ha

min min l/s m3

Pickering, ON a=

Mainstream Length (km) :- L = Mainstream Slope (m/km) :- S = Bransby Williams:-Tc = Time

100yr 2096.425

b=

6.485

c=

0.863

0.0

Rainfall

Storm

Runoff

Released

Storage

Intensity

Runoff

(min)

(mm/hr)

(l/s)

Volume 3 (m )

Volume 3 (m )

Volume 3 (m )

10.0

186.7

924.86

459.9

132.9

327.0

15.0

148.5

735.86

567.3

199.4

367.9

20.0

124.0

614.29

642.2

265.8

376.3

25.0

106.8

529.13

698.7

332.3

366.4

30.0

94.1

465.93

743.7

398.8

344.9

35.0

84.2

417.05

780.8

465.2

315.6

40.0

76.3

378.04

812.3

531.7

280.6

45.0

69.9

346.13

839.6

598.1

241.4

50.0

64.5

319.53

863.6

664.6

199.0

55.0

59.9

296.97

885.0

731.1

154.0

60.0

56.0

277.60

904.4

797.5

106.8

65.0

52.6

260.76

922.0

864.0

58.0

70.0

49.7

245.98

938.1

930.4

7.7

75.0

47.0

232.90

953.0

996.9

-43.9

80.0

44.7

221.23

966.9

1063.4

-96.5

85.0

42.5

210.76

979.9

1129.8

-150.0

90.0

40.6

201.30

992.0

1196.3

-204.3

95.0

38.9

192.71

1003.4

1262.7

-259.3

100.0

37.3

184.87

1014.2

1329.2

-315.0

105.0

35.9

177.70

1024.5

1395.7

-371.2

110.0

34.5

171.09

1034.2

1462.1

-427.9

115.0

33.3

165.00

1043.5

1528.6

-485.1

120.0

32.2

159.36

1052.4

1595.0

-542.7

125.0

31.1

154.11

1060.8

1661.5

-600.7