CITY OF TORONTO TOWER RENEWAL PROGRAM

PREPARED FOR:

City of Toronto Office of Tower Renewal

stormwater management feasibility study MARCH 2011

City Hall - 100 Queen Street West Toronto ON CA M5H 2N2

PREPARED BY:

TMIG | The Municipal Infrastructure Group Ltd. 8800 Dufferin Street Suite 200 Vaughan ON CA L4K 0C5 tel 905.738.5700 fax 905.738.0065 www.tmig.ca

Schollen & Company Inc. 220 Duncan Mill Road, Suite 109 Toronto ON CA M3B 3J5 tel 416.441.3044 fax 416.441.6010 www.schollenandcompany.com

this report has been formatted for double-sided printing cover photo credit: derek flack photography (www.derekflackphotography.com)

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Contents 1

2

3

4

Introduction ......................................................................... 1 1.1

Tower Renewal Program Overview ........................... 1

1.2

Focus of Study .......................................................... 1

1.3

Successful Examples ................................................ 2

1.4

Pilot Sites .................................................................. 5

Existing Conditions Analysis .............................................. 9 2.1

Urbanization and Stormwater Management............... 9

2.2

Existing Regulatory Framework and Objectives ................................................................. 9

2.3

Pilot Site Characterization ....................................... 13

2.1

Existing Drainage .................................................... 13

2.2

Precipitation Analysis .............................................. 19

Opportunities ..................................................................... 21 3.1

Low Impact Development ........................................ 21

3.2

Retrofit Opportunities for Low Impact Development and Source Control Approaches ............................................................. 21

Recommendations and Analysis ...................................... 27 4.1

Overview of Recommended Approaches ................ 27

4.2

Pilot Site Recommendations ................................... 29

4.3

Quantification of Benefits ........................................ 37

4.4

Costs ...................................................................... 40

4.5

Revitalization Concept Plan..................................... 43

5

Discussion and Next Steps ............................................... 46

6

References ......................................................................... 47

Appendices Appendix A:

Schematic Base Plans

Appendix B:

Calculations

Appendix C:

SWM Implementation Plans

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE iii

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figures Figure 1-1: Kelvin Grove Urban Village (credit: 3-bs.eu) ..................................................................................... 2 Figure 1-2: Jubilee Park Lake in Jamshedpur (credit sustainablecities.dk) ............................................................. 2 Figure 1-3: Corus Entertainment Building (credit archiseek.com) ..................................................................... 3 Figure 1-4: Reid's Heritage Homes LEED Platinum House, Guelph (credit: thestar.com) ..................................... 3 Figure 1-5: York University Computer Science and Engineering Building Green Roof (credit: iswm.ca) ............... 4 Figure 1-6: Augustenborg Botanical Roof Garden, Malmö (credit: sustainablecities.dk) ...................................... 5 Figure 1-7: 110 Parkway Forest Drive (credit Google) .......... 6 Figure 1-8: 215 Markham Road (credit Google) .................... 6 Figure 1-9: 200 Wellesley Street East (credit Google)........... 7 Figure 1-10: 2667 & 2677 Kipling Avenue (credit Google) ................................................................................ 7 Figure 1-11: 1765 & 1775 Weston Road (credit Google) ................................................................................ 8 Figure 2-1: Impacts of Urbanization on the Hydrologic Cycle (credit US EPA) .......................................................... 9 Figure 2-2: Tower Renewal Pilot Sites in proximity to Basement Flooding Priority Areas....................................... 12 Figure 2-3: Driveway and Catchbasin at 1765 Weston Road .................................................................................. 13 Figure 2-4: Parkway Forest Site Characterization Plan ....... 14 Figure 2-5: Markham Road Site Characterization Plan ....... 15 Figure 2-6: Wellesley Street Site Characterization Plan .................................................................................... 16 Figure 2-7: Kipling Avenue Site Characterization Plan ........ 17 Figure 2-8: Weston Road Site Characterization Plan .......... 18 Figure 2-9: Annual Precipitation Volume versus Event Depth ................................................................................. 19 Figure 3-1: Podium Green Roof at Toronto City Hall (credit City of Toronto) ........................................................ 22 Figure 3-2: Bioretention Cell at York University (credit iswm.ca) ............................................................................. 22 Figure 3-3: Biofiltration Section (credit Schollen & Company)........................................................................... 23 Figure 3-4: Permeable Pavement Driveway ........................ 23 Figure 3-5: Sample OGS (credit StormCeptor) ................... 24 Figure 3-6: Rainwater Harvesting Cistern Installation (credit Smart Watering Systems) ........................................ 25 Figure 4-1: Recommended Stormwater Management Retrofit – Parkway Forest ................................................... 30

PAGE iv ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 4-2: Recommended Stormwater Management Retrofit – Markham Road .................................................... 31 Figure 4-3: Recommended Stormwater Management Retrofit – Wellesley Street .................................................. 33 Figure 4-4: Recommended Stormwater Management Retrofit – Kipling Avenue .................................................... 34 Figure 4-5: Recommended Stormwater Management Retrofit – Weston Road ...................................................... 36 Figure 4-6: Revitalization Concept Plan .............................. 44 Figure 4-7: Revitalization Concept - Plaza View ................. 45

Tables Table 2-1: Existing Land Use Areas and Level of Imperviousness .................................................................. 13 Table 2-2: Return Period Event Rainfall Depths .................. 20 Table 2-3: Runoff Volumes ................................................. 20 Table 4-1: Runoff Volume – With Implementation of Proposed SWM/LID Measures ........................................... 38 Table 4-2: Percentage Reduction in Runoff Volume ........... 38 Table 4-3: Reduction in Runoff Volume per Unit Area ......... 39 Table 4-4: Estimated Reduction in Peak Flows ................... 39 Table 4-5: SWM/LID Measures Cost Analysis .................... 41 Table 4-6: Cost versus Benefit of Proposed LID/SWM Measures ........................................................................... 42

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE v

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

1

Introduction 1.1

Tower Renewal Program Overview Over 1,000 high-rise apartment buildings in the City of Toronto were constructed during the period extending from the 1960s and 1970s. These buildings were built to the standards of the day, but standards and building science have evolved such that today, these buildings have been determined to be highly inefficient and lacking in the physical, structural and infrastructural qualities necessary to make them functionally efficient, sustainable and viable over the long term. Most of these towers are exhibiting signs of deterioration and therefore, without improvement, are reaching the end of their serviceable lifespan. As an alternative to tearing down these older towers and starting anew, the City of Toronto has implemented the Toronto Tower Renewal Program. The objective of this program is to utilize the vast resources embodied in these existing buildings and revitalize these buildings to achieve higher levels of efficiency and sustainability with the overall goal of contributing to the realization of a more sustainable, walkable and greener City. The management of stormwater runoff is a major component of the effort to achieve the objectives of the Tower Renewal Program, particularly in consideration of the fact that the majority of the buildings that are the focus of this program are located in areas of the City that were built-out before the advent of modern stormwater management practices. As a result, the Tower Renewal Program is aimed in-part at exploring the potential to implement innovative solutions to address the management of stormwater runoff that is generated by these tower building sites, and minimize their contribution to downstream aging infrastructure.

1.2

Focus of Study The purpose of this study is to determine the role of existing tower buildings and their sites throughout the City with respect to their contribution of runoff volume to the City‟s overall storm drainage and management infrastructure, and to identify solutions that could be implemented that will be effective in reducing runoff volumes and the consequent dependency of these sites on downstream receiving storm systems in a manner that is feasible, cost effective, implementable, manageable, and desirable. The City of Toronto‟s Wet Weather Flow Management Guidelines, in combination with Toronto‟s Green Development Standard, have established a vision and determined the available level of service that can be reasonably provided by the City‟s drainage infrastructure. These programs promote the wide-spread implementation of source and conveyance controls to contribute effectively to the realization of the City‟s water management objectives, particularly with respect to quantity and quality control. Similarly, the City‟s Tower Renewal Program has initiated a review of existing buildings from a number of perspectives, and the implementation of effective stormwater management alternatives as one component of Tower Renewal will significantly increase the degree of success of this program. Furthermore, many stormwater management alternatives can yield constituent benefits such as reduced potable water consumption, reduced energy usage, and reduced maintenance effort, with corresponding economic benefits following a payback period associated with each alternative, which in combination serve as a mechanism for renewal. Community benefits can also be afforded in conjunction with the achievement of primary stormwater management objectives. For example, local food production supported through provision of common gardening areas that utilize harvested rainwater for irrigation can provide social and health benefits to the community while simultaneously achieving a number of other renewal objectives.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE 1

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

In short, this study is intended to identify innovative yet practical solutions that can be utilized to retrofit existing tower sites to reduce the volume of runoff generated by these areas, and in so doing address the combined and interrelated environmental, social, and economic objectives of Tower Renewal. 1.3

Successful Examples In general, the application of innovative practices to more effectively manage stormwater on large building sites is more practical and economical for new constructions. Limited examples of retrofit scenarios are available, nevertheless examples where new construction has incorporated less conventional stormwater management techniques provide ample guidance in the consideration of these measures for retrofit projects. Given that the built environments we have today will continue long into the future, and that these will continue to represent the majority of our built form in urban settings, investigations of practical methods to retrofit are imperative to achieve overall wet weather flow performance objectives. The paragraphs below describe a few cases of applied low impact and sustainable development technologies, both locally and abroad, which together demonstrate the benefits and feasibility of these approaches. Rainwater Harvesting

Australia is establishing a modern approach to managing stormwater that is called Water (18) Sensitive Urban Design (WSUD) . WSUD integrates all water resources and water recycling programs into the urban development process without compromising flood security or aesthetics. In order to achieve this, Australia has created a WSUD Technical Manual that provides examples of strategies Figure 1-1: Kelvin Grove Urban Village (credit: 3-b-s.eu) for a wide range of development types that include single residential development, residential multi-unit development, and publicly-owned land, among others. The Kelvin Grove Urban Village is an example of a high rise development that adhered to strict sustainable design guidelines. WSUD components were incorporated to achieve the standard of the sustainable design guidelines. Source controls were implemented as needed, and included covered bins and signage. A rainwater tank 200 kilolitres in size was constructed to enable onsite reuse of rainwater. A 50 kilolitre onsite detention tank was built to reduce the stormwater runoff peak flows. Vegetated swales and a bioretention system were also constructed on the property in order to divert and treat the stormwater before it (13) leaves the site . Jamshedpur, India is a city in which natural water resources are scarce. Therefore, as a city where water conservation is a necessity, rainwater harvesting systems have been implemented amongst locations such as local schools, residential colonies and Figure 1-2: Jubilee Park Lake in Jamshedpur (credit housing complexes. Roof runoff and sustainablecities.dk) groundwater runoff is collected, stored, and then pumped to head tanks on the top of buildings and used for toilet flushing, maintenance of garden lawns, and car washing. As a result of the implementation of these (8) systems, water conservation has improved greatly for this community .

PAGE 2 ____________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

The Corus Entertainment Building on Toronto‟s Waterfront was completed in 2010, and exhibits both a green roof and a rainwater collection system for use in the building‟s water closets. This combination of measures removes 15mm of every rainfall event, which contributed to its LEED Gold certification, and also satisfied the stringent and qualitative sustainability objectives of Toronto‟s (3) waterfront revitalization initiative . In Portland, Oregon, Jonathan Gray of Interface Engineering, Inc. has been an innovator in the field of rainwater harvesting for many years. One of his earlier projects in Portland involves a six-story residential dormitory. In this project, rainwater is collected into a 5,600 gallon tank and this captured rainwater is used without further treatment as reclaimed water for both flushing water closets and urinals in the first-floor public restrooms of the building. Any excess water is then (15) used for irrigation during the drier summer months . This is just one example of the numerous rainwater harvesting projects within North America. Commercial applications of rainwater harvesting have been instituted at office buildings in Seattle to University buildings in Boston. This application becomes the sole or partial source of water for water closets and urinals, landscape irrigation, hose bibs, water features, cooling towers or secondary fire suppression. Figure 1-3: Corus Entertainment Building (credit archiseek.com)

An example of the application of rainwater harvesting to a high-rise residential building is an elderly housing complex, located in Portland, Oregon, that consists of three connecting towers (14-story, 12-story, 9-story) and contains 170 units. The expected rainwater harvesting per year is 250,000 gallons. The system is set up with a gravity tank on each tower that collects the rainfall and feeds it into the common fire sprinkler storage tank that is located under a ramp in the parking garage. The rainwater is used to support flushing of 75 water closets on the (12) lower floors as well as secondary fire suppression . In general, taller buildings have an advantage for rainwater harvesting due to the quality of the water, as it collects much less debris, such as leaves, and can be used for other purposes such as irrigation, water features or secondary fire suppression. A rainwater harvesting system has been constructed at Reid‟s Heritage Homes in Guelph, Ontario. This system was implemented as a pilot project for the University of Guelph‟s researchers to monitor the rainwater harvesting system‟s performance and water quality. Rainwater from the rooftop of the building is collected and diverted by the roof gutters and downspouts to a 6,500 litre underground cistern via a filtration device. This water is stored within the underground cistern to be pressurized and piped into the home later on. Figure 1-4: Reid's Heritage Homes LEED These uses include supplying water to three Platinum House, Guelph (credit: thestar.com) toilets, a washing machine, a dishwasher, and an underground irrigation system. This particular home will also have a dedicated hot water system to provide rainwater for the washing machine and dishwasher. The total reduction in (2) the water consumption for this particular unit is estimated to be 50% .

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE 3

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Permeable Pavement

Green pavement technologies are becoming more popular within Canada, with the concept initially brought to Ontario by German companies. Open-jointed blocks (a permeable interlocking concrete pavement) have been used in North American since the 1980s. The first installations in Ontario were slowly permeable by today‟s standards because they used relatively dense-graded aggregate in the joints. From decades of research and experience, a strictly single-sized aggregate has been developed and can produce high permeability without loss of pavement stability. Installations from the last 10 years infiltrate rain water rapidly through this newly developed single-sized aggregate, while durably withstanding vigorous (11) winter snow-clearing . A study was recently implemented at a parking lot within the King City campus of Seneca College to examine the long-term performance and effectiveness of permeable interlocking concrete pavers (PICP) within the Greater Toronto Area. During the same study, bioretention swales were also examined as part of the research of stormwater management. The parking lot was divided into three equally sized areas, each with a different lot level control; PICP, a bioretention swale and a conventional asphalt control. Flows and water quality were monitored year round in an underground vault powered by a wind turbine and three solar panels. The (10) results include the following :   





99% of rainfall on the permeable pavement infiltrated over a 30 month period. The bioswale met its design objective of infiltrating and evapotranspiring all runoff for events up to approximately 15 to 20 mm. Stormwater infiltrated through the PICP and bioswale contained significantly lower levels of typical parking lot contaminants such as zinc, lead, and hydrocarbons relative to conventional asphalt runoff. Applying de-icing salts to permeable pavements may pose a risk to groundwater quality as the concentrations of these chemicals were not reduced by infiltration through the soil or granular media. Although surface temperatures of asphalt and PICPs were similar during the winter, the capacity of PICPs to infiltrate water helped reduce the incidence of ponding and ice buildup.

Green Roofs

In 2002, a study of an extensive green roof was conducted on the Computer Science and Engineering building on the campus of York University in the City of Toronto, Ontario. The objectives of this study were to evaluate the stormwater runoff quality and quantity, quantify the stormwater management benefits of green roofs at a watershed scale through scenario modelling, assess the potential effect of green roofs on urban biodiversity, and provide recommendations on the design and maintenance of green roofs to maximize benefits related to stormwater (5) management and biodiversity . The study divided the roof into two areas with one standard to represent a typical roof and the other Figure 1-5: York University Computer Science and covered by a garden that is vegetated with Engineering Building Green Roof (credit: iswm.ca) wildflowers and has a substrate 140 mm thick. Both roofs were continuously monitored from 2003 to 2005 for rainfall volumes, surface runoff quantity, air temperature, relative humidity, soil temperature and soil moisture levels. The (5) results include the following : 

The rooftop garden reduced runoff by 63% throughout the spring, summer and fall events.

PAGE 4 ____________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

  

The garden‟s ability to retain stormwater falls as storm size and moisture content increase, and temperature decreases. The rooftop garden indicated an improved water quality over the shingled roof for suspended solids, nitrate, E.coli, heavy metals and polycyclic aromatic hydrocarbons. The flora survey showed an increase in native plans from 18 to 29 over two years and revealed that the green roof could be conducive to the establishment of conservation or rare native plans of local concern.

In 1998, the Ekostaden Project was initiated in the district of Augustenborg in Malmö, Sweden. As one of Sweden‟s largest urban sustainability projects, the target of this plan was to establish the existing schools, residential and industrial areas, and local businesses as a socially, economically, and environmentally sustainable environment. A majority of the residential developments in this district were built between the years of 1948 and 1952, with more and larger developments constructed over the next 20 years. By the 1970s, the residents began to move out of these residential areas because of the poor maintenance and out-of-date amenities. Flooding became a major problem, resulting from an undersized drainage system and impermeable surfaces. Once the Ekostaden project was implemented, the district gained 2 10,000 m of green roof vegetation and an open stormwater management drainage system. Augustenborg now contains the world‟s first Botanical Roof Garden and is the home of further (1) research and study of stormwater management through the use of green roofs .

Figure 1-6: Augustenborg Botanical Roof Garden, Malmö (credit: sustainablecities.dk)

1.4

Pilot Sites Out of the 1,000 towers and sites targeted by the overall Tower Renewal initiative, five pilot sites have been selected in consultation with Tower Renewal and Toronto Water staff to be the subject of this study. The selected pilot sites exhibit characteristics that are largely representative of the broader cohort of Tower Renewal sites. As such, an assessment of stormwater management retrofit opportunities for the pilot sites can be projected to evaluate the feasibility, costs, and benefits of these retrofits on a City-wide scale. As described in more detail in subsequent sections of this report, the pilot sites vary in location, property area, building size and existing features, but also possess common characteristics that present both opportunities and challenges when considering the broader Tower Renewal initiative. 110 Parkway Forest Drive

This property is located in the Don Valley East neighbourhood of Toronto, near Fairview Mall, and between Highway 404 and Don Mills Road to the east and west respectively, and Sheppard Avenue and Highway 401 to the north and south respectively. This high-rise residential building consists of 17 floors and 216 units. This pilot site has a total area of 2.09 hectares.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE 5

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

The population within this community has remained stable between 2001 and 2006, with only a 1.2% increase in the number of residents. The population density in the community is more than four times the Toronto average (18,000 residents per square kilometre). This density is also considerably higher than the Figure 1-7: 110 Parkway Forest Drive (credit Google) other Tower Renewal pilot (17) neighbourhoods of approximately 10,000 residents per square kilometre . Ample green space surrounds the building and the site includes an extensive area of surface parking as well as an underground garage. It appears that both parking facilities are shared with the high-rise apartment buildings nearby. Parkway Forest Park is located on the west side of Parkway Forest Drive, south of Sheppard Avenue East. Improvements to Parkway Forest Park are proposed including a new community centre, outdoor pool and landscape improvements. The site is close to Fairview Mall and a TTC subway stop. 215 Markham Road

215 Markham Road is located in the Scarborough Village neighbourhood, near the intersection of Eglinton Avenue East and Markham Road. It is one of four high-rises that are located close together on Cougar Court. This high-rise building, built in 1969, consists of 18 floors and 192 units. The total area of land of this pilot site is 1.45 hectares. Based on the 2006 census, the Scarborough Village pilot site is in an area of rapidly declining population. Between 2001 and 2006, there was a nearly 19% decrease in the recorded number of residents. It is possible that this represents a decrease in the proportion of residents who were counted in the census instead of an actual decrease in the number of residents. The population density for the area is 10,000 (17) residents per square kilometre . Results of previous studies, including assessments and consultation with property owners and residents, have initiated the proposal of several projects for this pilot Figure 1-8: 215 Markham Road (credit Google) project site. Related projects proposed include improvements to shared driveway, improvements to main pathway, community garden and beautification, and shared outdoor recreation space. The site includes a surface parking lot, daycare play yard, playground and open space. The site is underlain by a parking garage. Transit is accessible immediately adjacent the site at Markham Road as well as nearby on Eglinton Avenue East. 200 Wellesley Street East

200 Wellesley Street East is one of four buildings owned by the Toronto Community Housing Corporation (TCHC) in the St. James Town neighbourhood. The St. James Town neighbourhood encompasses the area bounded by Sherbourne Street to the west, Bloor Street to the north, Parliament Street to the east, and Wellesley Street East to the south. The

PAGE 6 ____________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

apartment buildings in this neighbourhood were constructed in the 1960s, with this specific building built in 1970. It contains 719 units within 29 floors. The total area of this pilot site is 1.84 hectares. Approximately 17,000 people live in the neighbourhood‟s apartment towers making it Canada‟s most densely populated community (65,000 people per square kilometre) and one of the most densely populated neighbour-hoods anywhere in North America. The residents of this high-rise building have access to underground parking (17) and limited access to surface parking . As illustrated in the photo, only a small proportion of the site is dedicated to surface parking with the remainder of the paved areas comprising pedestrian walkways and hardscape associated with recreational amenities the building was recently impacted by a fire and reconstruction work was ongoing at the time of the site visit conducted by the consulting team.

Figure 1-9: 200 Wellesley Street East (credit Google)

Based on the results of previous completed studies, including assessments and consultation with the Toronto Community Housing (TCHC) Board and residents, several potential initiatives (17) have been proposed to enhance the site including :  

Supporting residents who wish to garden on balconies Re-instating a resident-led community garden that was previously located at the north east corner of the property

2667 & 2677 Kipling Avenue

These residential towers are located at 2667 and 2677 Kipling Avenue in the Rexdale–Jamestown area of Etobicoke, between Finch Avenue and Steeles Avenue West. Built in 1978, the two 23-floor buildings contain a total of 458 units. The site has a total area of 2.31 hectares, and there is a ravine adjacent the east side of the property. The neighbourhood is identified as a high growth area in the City, exhibiting a nearly 10% growth in population between 2001 and 2006 in comparison with the typical 1% increase observed for the entire City of Toronto. The population density within this Figure 1-10: 2667 & 2677 Kipling Avenue (credit Google) neighbourhood is more than double the Toronto average at 10,000 residents per square (17) kilometre, compared with an average 4,000 residents per square kilometre across Toronto. Concept plans for site improvements are currently being developed for 2667 and 2677 Kipling (17) Avenue. Improvements being considered include but are not limited to :  

Refurbishing one of the tennis courts at the site to create a basketball court. Creating a children‟s play area with good natural surveillance and separation from traffic.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE 7

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

 

Creating a gathering area in front of 2677 Kipling Avenue that could accommodate off-thetruck fruit and vegetable sales as part of a pilot project. General landscaping improvements, including removing and replacing dead trees, adding benches, shrubs and new trees and additional exterior lighting.

The site includes a surface parking lot, abandoned tennis court, and open space. The site is underlain by a parking garage. Transit is accessible immediately adjacent the site on Kipling Avenue. 1765 & 1775 Weston Road

This site is located on the west side of Toronto, close to the Lawrence Avenue West and Weston Road intersection. Two identical, 25-story high-rise buildings are located on the 1.61 hectare property that includes limited green space and a minimum number of trees. The property is underlain by an extensive underground parking garage and offers very little surface parking. A railway corridor runs northeast along the property line. A private Recreation Centre is situated between the 2 towers. This facility at one Figure 1-11: 1765 & 1775 Weston Road (credit Google) time housed a pool and exercise room but is no longer in use and has fallen into disrepair. A sunken garden is located in front of the Recreation Centre, however this amenity has also been abandoned and is overgrown. The walkway system within the site is sheltered by a system of colonnades. The site is generally flat and windswept. A TTC stop is located immediately adjacent to the site and there are a number of shops and restaurants located along Weston Road in the immediate vicinity of the site whose proximity contributes to walkability.

PAGE 8 ____________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

2

Existing Conditions Analysis 2.1

Urbanization and Stormwater Management Whenever it rains, water that lands on the ground surface is distributed in several directions. Some of the water infiltrates the ground (infiltration), some of it runs off the surface (runoff), and the remainder either evaporates or is consumed by plants (evapotranspiration). In natural settings, the presence of vegetation and the lack of hard surfaces defines this distribution such that a relatively small part of the rainfall produces runoff. In built communities, the introduction of hard surfaces and the reduction in vegetated cover alter this proportion such that significantly more runoff is generated, and less water makes its way into the ground to eventually recharge streams and groundwater resources. During storm events, the increase in surface runoff usually generated by urban communities can result in flooding and erosive damage to our streams and structures. In addition, human activity produces pollution, which in combination with the increased runoff can have disastrous effects. Stormwater management is needed to manage the quantity and quality of runoff generated by urban communities in order to prevent these impacts. Stormwater is conventionally managed in three stages: at the source, in the conveyance system, or at the “end-ofpipe”. The source, or lot level, is the landscape surface where the rain falls (roofs, lawns, parking lots, driveways). The conveyance system is the network of storm sewers and overland flow paths (roadways and ditches) that take the runoff from the source to the endof-pipe. The end-of-pipe systems include stormwater ponds, wetlands, oil grit separators, or infiltration basins.

Figure 2-1: Impacts of Urbanization on the Hydrologic Cycle (credit US EPA)

Low impact development (LID) is the next evolution in stormwater management that in some cases reintroduces older technologies, and provides an alternative set of mechanisms to manage stormwater that can better integrate within the urban fabric, provide relief to hard downstream infrastructure such as sewers and ponds, and distribute the management of runoff to improve our ability to adapt to climate change. In general the objectives of low impact development are to:

maximize infiltration

2.2

maximize evapotranspiration

maximize reuse

minimize hard surfaces

Existing Regulatory Framework and Objectives Within the City of Toronto, several key documents provide criteria and requirements pertaining to stormwater management, generally applicable to new development or redevelopment projects. However, these targets represent a suitable objective in the planning and design of (16) any retrofit endeavour. As described in the Tower Renewal Guidelines , “The critical mission

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. ___________________________________ PAGE 9

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

for urban stormwater management is to reduce the quantity of water entering the municipal system and to improve its quality in terms of contaminants and suspended solids.” Wet Weather Flow Management Guidelines (19)

The Wet Weather Flow Management Guidelines (November 2006) provide guidance for development and redevelopment projects with respect to the City of Toronto‟s stormwater management requirements. In particular, the WWFMG stipulates the following:

Water Balance Targets: (i) retain stormwater on-site, to the extent practicable, to achieve the same level of annual volume of overland runoff allowable from the development site under pre-development conditions; (ii) if the allowable annual runoff volume from the development site under post-development conditions is less than the pre-development conditions, then the more stringent runoff volume requirement becomes the governing target for the development site. The maximum allowable annual runoff volume from any development site is 50% of the total average annual rainfall depth; and (iii) in most cases, the minimum on-site runoff retention requires the proponent to retain all runoff from a small design rainfall event – typically 5mm through infiltration, evapotranspiration and rainwater reuse. Water Quality Targets: (i) the long-term average removal of 80% of Total Suspended Solids (TSS) on an annual loading basis from all runoff leaving the proposed development site based on the post-development level of imperviousness. Erosion Control Criteria: (i) for large development blocks (site area greater than 5ha) discharging directly and/or in proximity (within 100m) to natural watercourses, the proponents are required to complete an Erosion Analysis Report to determine the erosion control criteria for the site; (ii) for sites where it is not feasible to complete an Erosion Analysis Report, it is required that runoff from a 25mm design storm be detained on-site and released over a minimum of 24 hours; and (iii) for small infill/redevelopment sites less than 2ha, erosion control in the form of stormwater detention is normally not required, provided the on-site minimum runoff retention from a small design rainfall event (typically 5mm) is achieved under the Water Balance Criteria. Water Quantity Criteria: (i) peak flow control equivalent to 2 year -100 year control post to pre; and (ii) when the imperviousness of a development site under pre-development condition is higher than 50% (regardless of the post-development condition), the maximum value of C (Runoff Coefficient) used in calculating the pre-development peak runoff rate is limited to 0.50. As is demonstrated in Section 2.3, the average imperviousness of the Tower Renewal pilot sites is 55%, which necessitates an assumed predevelopment runoff coefficient value of 0.50. Green Development Standard (6)

The City of Toronto‟s Green Development Standard provides a set of performance measures with supporting guidelines related to sustainable site and building design for new development. In terms of water quality, quantity, and efficiency, the checklist associated with the standard includes the following: Water Balance: (i) stormwater retained on-site to the same level of annual volume of overland runoff allowable under pre-development conditions; and (ii) the first 5 mm from each rainfall retained on-site or maximum allowable annual runoff volume is no more than 50% of the total average annual rainfall depth

PAGE 10 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Water Quality: (i) 80% of total suspended solids removed from all runoff leaving the site; and (ii) E.coli controlled in runoff from sites discharging directly into Lake Ontario or waterfront areas Water Efficiency: water efficient plant material for 50% of landscaped area An overall goal of the Tower Renewal Program is to upgrade existing buildings such that they achieve standards comparable with newly constructed high-performance buildings that adhere to the requirements of the Green Development Standard. Stormwater Management Planning and Design Manual

The Ministry of Environment‟s Stormwater Management Planning and (14) Design Manual (March 2003) provides design guidance for stormwater management infrastructure necessary to satisfy provincial objectives. In particular, the manual prescribes an „enhanced‟ level of water quality control, necessary for sensitive aquatic habitats, equivalent to the removal of 80% of total suspended solids from all runoff leaving an area. The manual also provides guidance with respect to erosion attenuation and water quantity control, and details a full suite of measures intended to mitigate the impacts of urbanization. Low Impact Development Stormwater Management Planning and Design Guide

The Low Impact Development (LID) Stormwater Management Guide (8) is a joint initiative of the Toronto and Region and Credit Valley Conservation Authorities that has been developed in consultation with representatives from the Ministry of the Environment, Fisheries and Oceans Canada, GTA municipalities and the development industry. The guide was developed to provide engineers, ecologists and planners with up-to-date information and direction on landscapebased stormwater management planning and Low Impact Development stormwater management practices, and thereby help ensure the continued health of the streams, rivers, lakes, fisheries and terrestrial habitats in the CVC and TRCA watersheds. It addresses not only the planning, selection, and design of LID, but also the costs of implementing these practices. City of Toronto Basement Flooding Protection Program

On August 19, 2005, the City of Toronto experienced a severe storm event that resulted in the flooding of many residential homes, erosion of ravines and watercourses, and damage to City infrastructure such as roads, bridges, culverts and sewers. As a result, the City has initiated a number of studies in areas of chronic basement flooding. A number of these studies have been completed, and the City is now launching a multi-year Basement Flooding Protection Program to implement the solutions and help prevent basement and surface flooding. More information on this program can be found on the City‟s website: www.toronto.ca/involved/projects/basement_flooding_protection_program/index.htm The relevance of Tower Renewal within the context of basement flooding has relevance with respect to the reduced runoff that can be achieved through the introduction of Low Impact Development and source control stormwater management mechanisms. This reduction in runoff can alleviate the existing flows within storm sewers during rainfall events, thereby reducing the extent and severity of basement flooding occurrences. Figure 2-2 illustrates the locations of those Tower Renewal pilot sites that are in proximity to the City‟s Basement Flooding priority areas.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 11

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 2-2: Tower Renewal Pilot Sites in proximity to Basement Flooding Priority Areas

PAGE 12 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

2.3

Pilot Site Characterization Utilizing schematic base plans prepared for this analysis, each pilot site was characterized in terms of overall imperviousness. This characteristic was determined based on the proportion of the site that is impervious, or incapable of being penetrated by water, versus the area that is pervious, or can support infiltration. The schematic characterization plans are shown in Figure 2-4 through Figure 2-8, with full size versions provided in Appendix A. Areas typically characterized as impervious include asphalt parking areas, tennis courts, sidewalks and rooftops, as well as other hard surface amenities. It should be noted that the underground parking structures underlying all of the pilot sites do not impact the evaluation of imperviousness, although the structures do limit the effectiveness of stormwater management and low impact development approaches that rely on infiltration. Measurements were completed to define the existing land use areas for each pilot site, and these land use areas were classified in terms of four land use types; landscape, walkways, pavement, and building. A runoff coefficient of 0.25 was applied to the landscaped areas, and 0.95 to the remaining building and hard surface areas. A weighted runoff coefficient was calculated and used to determine an equivalent level of imperviousness by applying the following equation: I = (C - 0.2) / 0.7, where I is the level of imperviousness and C is the weighted runoff coefficient. The various land use areas, weighted runoff coefficients, and impervious levels for each pilot site were averaged. Detailed calculations are provided in Appendix B, with a summary provided in Table 2-1, below. The evaluation reveals that, on average, the tower renewal sites 2 exhibit an imperviousness of 55% with an average site area of 18,585 m (1.86ha). This imperviousness value is comparable to that exhibited by low density residential neighbourhoods, which form the bulk of areas affected by basement flooding.

2.1

Address

Landscape Area (m2)

Walkway Area (m2)

Pavement Area (m2)

Building (m2)

Total Area (m2)

Average Runoff Coefficient

Percent Impervious

Table 2-1: Existing Land Use Areas and Level of Imperviousness

Parkway Forest

10,752

1,538

7,031

1,538

20,859

0.59

56%

Markham Road

7,077

471

5,379

1,539

14,466

0.61

58%

Wellesley Street East

8,581

3,104

3,185

3,493

18,363

0.62

60%

Kipling Avenue

12,626

1,258

6,806

2,423

23,112

0.57

53%

Weston Road

9,677

1,303

2,332

2,820

16,130

0.53

47%

Existing Drainage The existing stormwater drainage systems are similar for each pilot site. The runoff from the rooftop of the buildings is collected by roof drains and conveyed via an internal piping system through the building and through the underground garage. This runoff is then discharged to the major storm sewer system running along the adjacent main road. Catch basins are located throughout the sites to collect the surface parking lot and driveway runoff. This runoff is also routed to the storm sewer system located at the adjacent road of the site.

Figure 2-3: Driveway and Catchbasin at 1765 Weston Road

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 13

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 2-4: Parkway Forest Site Characterization Plan

PAGE 14 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 2-5: Markham Road Site Characterization Plan

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 15

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 2-6: Wellesley Street Site Characterization Plan

PAGE 16 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 2-7: Kipling Avenue Site Characterization Plan

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 17

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 2-8: Weston Road Site Characterization Plan

PAGE 18 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Precipitation Analysis An evaluation of available precipitation data was undertaken to estimate the response of the pilot sites to various statistical rainfall events. A long term record of data (1965-2002), as recorded at Pearson Airport, was obtained from Environment Canada. The collected data was averaged to determine the average annual and monthly rainfall depths, which were then applied to the various land use areas established for the pilot sites to calculate the average annual and monthly runoff volumes. Detailed calculations are provided in Appendix B.

800 700 Annual PrecIpitation Volume (mm)

2.2

600 500 400 events less than or equal to 5mm comprise about 400mm, or over 50%, of average annual rainfall volume

300 200 100 0 0

5

10

15

20

25

30

35

40

Precipitation Event Depth (mm)

Figure 2-9: Annual Precipitation Volume versus Event Depth

In addition, the relationship between average annual precipitation volume and event depth was established, as illustrated in Figure 2-9. This relationship provides a basis for estimating the effectiveness of SWM measures from a water balance perspective, as a function of the depth of rainfall that could be controlled by the given measure. For example, as noted on the figure, a SWM measure that provides control of all events less than or equal to 5mm will in effect be removing over half of the average annual rainfall over the site area. Return period events describe those larger rainfall events that occur statistically once in every given return period. A 100-year return period event describes the storm that would be expected to occur once every 100 years. Return period events provide the basis for the sizing and design of storm and drainage infrastructure. As such, a range of return period events have also been reviewed within the context of this study, so that any recommended storm-water management options can also be measured from the perspective of these larger storms. The depth of each return-period storm event was established through simulation of the events using Visual OTTHYMO v2.0, with the characteristics of each event defined by the intensityduration-frequency (IDF) relationships stipulated by the Wet Weather Flow Management Guideline. The details of the simulation are provided in Appendix B, while Table 2-2 summarizes the depth of rainfall attributed to each storm event. The following excerpt from the WWFM Guideline (page 32) explains the genesis of the current IDF curves: The updated IDF curves were derived based on the rainfall statistic analysis from three Toronto Gauges: Toronto Bloor Street (Gauge #6158350 – 24 years record), Ellesmere (Gauge #6158520 – 21 years record) and Pearson Airport (Gauge #6158733), as part of the WWFMP Study. The Parameter C is of negative value because the equation is written in a “multiplication” instead of a “reciprocal” format. It can also be written in the familiar format as: I c = a/(t + b) , where, for a 2-year storm, a=21.8, b=0, and c=0.78.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 19

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Table 2-2: Return Period Event Rainfall Depths IDF Parameters (WWFM Guideline) Event

Rainfall Depth (mm) A

C

25mm

--

--

25.00

2-Year

21.8

-0.78

29.57

5-Year

32.0

-0.79

42.80

10-Year

38.7

-0.80

51.05

25-Year

45.2

-0.80

59.62

50-Year

53.5

-0.80

70.57

100-Year

59.7

-0.80

78.75

To determine the total runoff volumes for each return period event, the area associated with each land use type was multiplied with the corresponding runoff coefficient and the related return period rainfall depth. The average and total runoff volumes are summarized in Table 2-3, with detailed calculations provided in Appendix B.

Table 2-3: Runoff Volumes

Site

Average Annual Runoff (m3)

Return Period Event Runoff Volumes (m3) 25 mm

2 Year

5 Year

10 Year

25 Year

50 Year

100 Year

Parkway Forest

9,632

307

363

526

627

733

867

968

Markham Road

6,888

220

260

376

449

524

620

692

Wellesley Street East

8,965

286

338

490

584

682

807

901

Kipling Avenue

10,282

328

388

561

670

782

926

1,033

Weston Road

6,701

214

253

366

436

510

603

673

PAGE 20 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

3

Opportunities As noted in Section 2.1, there are a number of conventional and contemporary approaches that can be applied to reduce the runoff generated by a developed area. These approaches, in general, seek to intercept, attenuate, divert, or harvest runoff to achieve a net reduction in runoff volume. Opportunities that reduce runoff can also sometimes complement other renewal and revitalization initiatives, providing a multi-functional benefit that is a key principal of sustainable design. Approaches have been explored that will endeavour to achieve prevailing stormwater management targets (Section 2.2) and will reduce the runoff that needs to be managed via receiving municipal systems. The following subsections provide an overview of the existing approaches to stormwater management and Low Impact Development that can be considered as part of the overall Tower Renewal Program. 3.1

Low Impact Development As introduced in Section 2.1, Low Impact Development (LID) is the next evolution in stormwater management. In some cases LID reintroduces older technologies and adapts them to establish an alternative set of mechanisms aimed at managing stormwater that can be better integrated within the urban fabric of the City. LID solutions provide relief to hard downstream infrastructure, such as sewers and ponds, and distribute the management of runoff to improve the system‟s overall ability to adapt to climate change. LID practices include innovative site design strategies that target minimization and/or attenuation of runoff, however, they can also include small scale lot level and conveyance practices. The following list outlines examples of LID practices that are applicable to high-rise residential buildings. The majority of these (19) approaches are also listed in the City‟s WWFMG .

3.2



Increased vegetation



Pervious technologies



Route roof drainage to pocket wetlands



Oil & grit separators



Green roof technologies



Enhanced ditches/swales



Use of filters/bio-retention



Rainwater harvesting



Pervious pavement in parking areas



Reduced lot grading



Absorbent landscaping

Retrofit Opportunities for Low Impact Development and Source Control Approaches A range of criteria were utilized to determine the feasibility of implementing stormwater management retrofit measures for the tower renewal program including: cost, lifespan, maintenance requirements, quantity control effectiveness, quality control effectiveness, aesthetics, and other benefits. Increased Extent of Vegetation Cover

Planting new trees and other plants in the boulevards can be beneficial to the reduction of stormwater runoff volume and peak flow, especially where these plantings replace existing hard surfaces. Additionally, increased vegetation cover improves the water quality, absorbs greenhouse gases, and plays a role in mitigating the urban heat island effect. For the Tower Renewal pilot sites, opportunities to increase vegetation cover provide a means to reducing the

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 21

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

extent of hard surface wherever possible, and to revitalize the existing expanses of lawn that occupy much of the open space areas to increase biodiversity and enhance the urban forest. Route Roof Drainage to Pocket Wetlands

Rerouting roof drainage from the existing storm infrastructure to a wetland can be useful in reducing the pressure applied to the storm system by storing stormwater on-site and allowing it to dissipate via infiltration and evapotranspiration. Where space and drainage patterns permit, this approach has applicability to the Tower Renewal pilot sites as a method of intercepting, attenuating, and providing treatment of runoff at the source, while simultaneously naturalizing existing lawn areas for both ecological and aesthetic purposes. Green Roof

Green roofs are an extension of traditional rooftop storage techniques. A green roof is a roof with a layer of drainage and growing media that supports living vegetation. Green roofs have the benefit of reducing peak flows and runoff volume, improve air quality, lower energy use and can moderate summer air temperatures. A rooftop garden can provide a 45% reduction in (7) runoff via evapotranspiration. Toronto‟s Green Development Standard stipulates the set of requirements for the installation of green roofs on portions of building roof areas within the City. The standards set out different requirements for green roof coverage based on building type and size. In addition to the benefits of a green roof from the stormwater management point of view, sites could also benefit from green roofs from both aesthetic Figure 3-1: Podium Green Roof at Toronto City Hall (credit City of and community perspectives, Toronto) through the encouragement of community rooftop gardening. Green roofs can range in complexity from extensive (simple and typically inaccessible to the public) to intensive (more complex and generally accessible to the public). However, the presence of landscaped areas surrounding the Tower Renewal pilot site buildings yields an opportunity to utilize rooftop runoff as a resource for reuse, an application that would conflict with a green roof. In addition, existing mechanical (HVAC) equipment reduces the net area available for green roof installations. As such, for the Tower Renewal pilot sites, green roofs have not been considered, but the opportunities for green roof retrofits should be evaluated on a case-by-case basis as part of the overall Tower Renewal initiative. Bioretention Cells

Bioretention involves the capture and infiltration of stormwater runoff from impervious surfaces to reduce water pollution and stabilize stream flows. Bioretention cells have an engineered and constructed subgrade, due to altered compacted soil conditions. The subgrade ensures adequate

Figure 3-2: Bioretention Cell at York University (credit iswm.ca)

PAGE 22 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

percolation of captured runoff by using a perforated drain pipe in a rock bed covered by a sandy soil mixture. A limiting factor for placement of a bioretention cell may be the lack of an outlet for the sub-drain. An outlet is necessary to ensure proper drainage. The sub-drain often outlets into the storm sewer or can discharge down gradient of the bioretention cell. Bioretention cells offer flexibility in terms of size and configuration, ranging from extensive bioretention areas and biofilters with engineered flow regulation to smaller ornamental rain gardens, and as such have applicability within the context of the Tower Renewal pilot sites where positive outlets are available. Filtration Systems

Filters can be implemented above ground or below ground as part of the storm sewer system infrastructure. Filters are generally intended to provide water quality control for small drainage areas (less than 5 hectares) by filtering the stormwater runoff prior to entering the storm sewer system. Filtration systems include surface sand filters, organic filters, underground sand filters and bioretention filters. Surface sand filtration systems consist of shallow depressions filled with sand. Pervious pipes are installed beneath the sand layer to convey the stormwater to the Figure 3-3: Biofiltration Section (credit Schollen & storm sewer system. Variations on the Company) surface sand filter include employing a layer of peat (organic filter) and placing topsoil and landscaping over the sand filter (bioretention filter). Underground sand filters are more complex and involve a large underground chamber consisting of a wet pool chamber, a filter bed chamber and an overflow chamber. Filtration can also be provided through conveyance systems such as roadside ditches and grassed swales. As with bioretention cells, filtration systems provide a wide range of flexibility in terms of size and configuration, and as such represent a suitable retrofit measure for the Tower Renewal pilot sites. Pervious Pipe Systems

Pervious pipe systems are a conveyance measure that can be incorporated into the design of a site as an LID solution. This pipe system is perforated along its length to allow stormwater to exfiltrate from the storm sewer as it is conveyed along the flow system. As with the filtration systems, pervious pipe systems can be installed in a variety of configurations, and as such can be considered as a Tower Renewal retrofit option. Permeable Pavement

Permeable pavements are a type of otherwise impervious surface treatment equipped with spaces or gaps that allow for the collection of surface runoff, thus

Figure 3-4: Permeable Pavement Driveway

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 23

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

providing the potential for infiltration and groundwater recharge. One type is permeable interlocking paving stones that have increased joint widths that are filled with granular material to allow for infiltration of runoff. The implementation of permeable pavement can result in benefits related to increased infiltration and providing some erosion control. Opportunities for the implementation of permeable pavement throughout the surface parking lots and driveways should be explored. Other types of treatments such as porous asphalt are available and can be evaluated as (16) needed . Reduced Lot Grading

This approach typically applies to residential lots, where flatter grades are implemented across the property to slow down runoff and further encourage both infiltration and evapotranspiration. Typical development standards require minimum lot grades of 2% for adequate drainage of stormwater away from buildings. Wet Weather Flow Management practices recommend the reduction of the minimum lot grades from 2% to 0.5%. Grading within 2 to 4 metres of a building should be maintained at 2% or higher to ensure that foundation drainage problems do not occur. The presence of extensive underground garage structures within all the Tower Renewal pilot sites limits the opportunity to adjust site grades to any appreciable degree. Oil & Grit Separators (OGS)

OGS are used to trap and retain oil and/or sediment in detention chambers, usually located below ground. They operate based on the principles of gravity based sedimentation for the grit, and phase separation for the oil. OGS are typically used for small drainage areas (less than 2 hectares), as part of a multi-component stormwater quality control system. The WWFMG outline the City of Toronto‟s requirements with respect to OGS‟. The City considers that these devices should not be solely relied upon to achieve water quality objectives, but should rather form part of a series of stormwater management measures, and that these devices, in the absence of additional field performance data, will only Figure 3-5: Sample OGS be credited with achieving a maximum of 50% removal of TSS. As per (credit StormCeptor) the Guideline, the list of products currently accepted by the City includes (but is not necessarily limited to) VortSentry, Vortechs, High Efficiency CDS, Baysaver Separator System, Downstream Defender, and StormCeptor. Within a retrofit setting OGS‟ have less applicability other than where a specific water quality concern is to be addressed. As such, OGS‟ have not been extensively considered within the context of Tower Renewal. Infiltration Trenches

Infiltration trenches are excavated trenches that are backfilled with an aggregate material to permit the filtration and percolation of water into sub-soils. Alternatively, some or all of the stored water may be collected by perforated under-drains (pervious pipe or filtration systems) and routed to an outflow facility. They are typically feasible for contributing drainage areas of less than 2 hectares. Infiltration trenches have a minimal contribution to the decrease in stormwater runoff, however, but can significantly improve water quality. Variations of infiltration trenches include dry wells, infiltration tanks, and surface dispersion trenches. These approaches have less applicability within the context of the Tower Renewal pilot sites, particularly when considering the constraint posed by the extensive underground parking garages.

PAGE 24 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Vegetated Swales

Vegetated channel systems serve to reduce stormwater velocities while filtering sediment and pollutants out of the stormwater. Swales are an effective way to convey water to bioretention areas and when used in combination with bioretention areas, swales serve as an additional level of pre-treatment. As most swales are designed as dry swales but variations include wet swales and bioswales. A dry swale is an engineered conveyance facility that is designed to capture and treat a water quality target volume through a filter media. They include a fabricated soil bed and a filter bed that overlies a drain system such as a perforated gravel bed that ultimately connects to the storm drainage system. A wet swale is a linear wetland system that contains standing water between storm events. A bioswale serves the same purpose as a dry swale, but the infiltration capabilities are enhanced. Bioswales can be considered as a conveyance mechanism to redirect drainage within the Tower Renewal pilot sites. Rainwater Harvesting

Rainwater harvesting is the storage and utilization of rooftop runoff for, typically, landscape irrigation. In general, the concept entails the conveyance of rooftop runoff to a cistern for storage and eventual use for watering, with the cistern size based on typical watering requirements. Lawn care literature recommends 25mm of watering per week over landscaped areas during the growing season. Rainwater harvesting provides a number of benefits, including the reduction in runoff from the site, along with a reduction in the usage of municipal water. While the cost savings in terms of municipal water to the owner are nominal based on current potable water charges, easing the community-wide strain on municipal infrastructure can have a much more substantial and long-term benefit.

Figure 3-6: Rainwater Harvesting Cistern Installation (credit Smart Watering Systems)

Rainwater harvesting potential is determined by the available area of clean surfaces, such as roofs, that can be used as catchment areas for precipitation. This precipitation will be collected and conveyed to an on-site storage system for use later on when irrigation (or other) loads are (9) the highest . Rainwater harvesting has extensive applicability within the context of the Tower Renewal pilot sites. Cistern

A cistern is an impervious storage unit that can retain stormwater for use later on. This type of storage tank is used in conjunction with a rainwater harvesting system. Cisterns are designed based on the drainage area, land use, and future use of the collected and stored rainwater. Rooftop Storage

Rooftop storage is a common method of source control that is highly effective for reducing peak flow rates but does not provide any volume control. It is developed by restricting the rate of flow from the roof drains during a storm event. Rooftop storage can be created by installing restrictors at the roof collection points. The addition of a perforated weir allows controlled discharge to the roof drain and the crest of the weir controls the maximum depth of ponding. In the context of the Tower Renewal Program, the rooftop rainwater can be put into operation for

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 25

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

multiple uses including supplying water to cooling towers, supplying water to steam radiator heating systems, and redirecting rainwater via the roof drains to supply water to the laundry facility rather than discharge to the storm system. These methods would assist in providing quantity control by reducing the runoff generated from the site, as well as reducing the load on municipal water infrastructure. Roof Drainage Diversion

The existing buildings presently drain internally directly to the municipal storm system. For rooftop areas, introducing scuppers at the roof edge, along with restrictors on the existing roof drains, will allow drainage to be conveyed to grade via systems that are external to the building to the new surface features. This option is well-suited for consideration in conjunction with proposals for re-skinning existing towers to enhance building envelop efficiency, and can be considered as a method of controlling rooftop runoff without disturbing existing roof drain to storm sewer infrastructure.

PAGE 26 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

4

Recommendations and Analysis 4.1

Overview of Recommended Approaches The recommended approaches have been considered within the context of the categories listed in Section 2.1. In combination, these approaches will reduce the volume of runoff generated by the Tower Renewal sites in an effort to address the requirements and objectives outlined in Section 2.2.

maximize infiltration

Infiltration describes the conveyance of water into the soil layer, either for interflow to nearby water bodies, or downward to recharge groundwater resources. The ability to infiltrate runoff is dependent on the suitability of the prevailing soil conditions, as well as the depth to the water table.

For the Tower Renewal pilot sites, a major challenge to any infiltration mechanism is the presence of expansive underground parking structures. Nevertheless, opportunities to infiltrate should be considered outside of the parking garage limits, and also where conveyance through the soil layer, notwithstanding the presence of the garage, can attenuate, filter, and direct water in manners that alleviate dependency on the municipal storm sewer system. Infiltration opportunities for the Tower Renewal pilot sites are largely limited to the installation of permeable pavement in existing and necessary hard-surface areas. Given the presence of the garage structures, as well as variable soil and groundwater conditions, a major consideration in the design of the permeable pavement areas is the provision for an overflow, most practically to the local storm sewer. Therefore, permeable pavement is recommended for those areas in close proximity to the adjacent right-of-way, such that the overflow can connect to the nearby storm sewer. In addition, other proposed measures such as bioretention areas, which are primarily intended to maximize evapotranspiration, will create additional potential for infiltration.

Evapotranspiration describes the combined effect of evaporation and transpiration, which is the water that is „transpired‟ by vegetation. In a maximize natural setting, evapotranspiration can take up around 60% of the evapotranspiration average annual rainfall. In an urban setting this percentage is significantly reduced, therefore maximizing the amount of vegetation can be very effective in moderating the stormwater management impacts of urbanization. For the Tower Renewal pilot sites, the presence of large lawn areas provides an excellent opportunity to maximize the potential for evapotranspiration by installing rain gardens, bioretention areas, and naturalization areas that will maximize the potential for evapotranspiration. These also provide a storage element that encourages infiltration and provide attenuation of runoff so that it enters the municipal system slowly and after storms have passed. At the very least, the relief in the topography created by varying the types of vegetation will mitigate the relatively efficient sheet flow action typical of grassed areas. Drainage from hard surfaces will be directed to the rain gardens and bioretention areas. For parking and driveway areas, the redirection of runoff can be achieved through minor regrading or by intercepting local storm pipes and catchbasin leads. For rooftop areas, introducing scuppers at the roof edge, along with restrictors on the existing roof drains, will allow drainage to be conveyed to grade via systems that are external to the building to the new surface features. This option is well-suited for consideration in conjunction with proposals for reskinning existing towers to enhance building envelop efficiency.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 27

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Rainwater reuse, or rainwater harvesting, describes the collection of runoff from a surface, storage, and subsequent use of the stored maximize water for irrigation or other uses. This practice not only reduces the reuse load on the receiving storm system, but also decreases the volume of potable water consumption. For most applications, rooftop runoff is deemed the most clean source of water, while runoff from surface parking areas and driveways, which is subject to all the contaminants associated with automobiles, requires pretreatment before reuse. Given the age of the Tower Renewal sites, the use of captured runoff for internal building needs, such as water closets and laundry, would require significant modification to the building‟s plumbing systems. As such, recommended rainwater harvesting approaches have been limited to the capture of rooftop runoff for landscape and allotment garden irrigation. In some instances, the provision of pre-treatment of surface drainage is also proposed as a means to utilize surface runoff. For rooftop runoff capture, utilizing the internal building roof drainage system by installing a cistern within the parking garage provides an opportunity to make a large volume of water available for landscape irrigation. There are indications that excess capacity exists within the underground parking garages. As a result, a rainwater cistern would provide a good alternative use for this space.

The majority of stormwater management impacts associated with urbanization are due to the increase in hard surfaces. Any efforts to minimize hard minimize the extent of hard surface will yield a direct and significant surfaces reduction in the volume of runoff generated by a site. In general, it is anticipated that the extent of hard surface that presently exists within the Tower Renewal pilot sites is associated with required functionality. Therefore, conversion of hard surface to other surface treatments has only been considered in special instances where it is known that the hard surface is not required. Noticeably abandoned tennis courts, patio areas, or swimming pools are recommended for conversion to stormwater management treatment areas.

PAGE 28 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

4.2

Pilot Site Recommendations Schematics illustrating the recommended approaches are shown in Figure 4-1 through Figure 4-5, with large scale versions provided in Appendix C. Details of the measures that are proposed to be implemented within the pilot sites are also summarized. 110 Parkway Forest Drive

The 110 Parkway Forest Drive site presently consists of a high-rise residential building with both underground and surface parking area. Ample landscaped area is available under existing conditions surrounding the building. In order to improve the management of stormwater runoff the following stormwater management measures are proposed (Figure 4-1): 

Cistern for rainwater recycling: Underground cistern captures the clean rooftop runoff for reuse and landscape irrigation during the growing season. This measure reduces the stormwater runoff generated by the residential building area and also reduces the usage of municipal water.



Rain garden: The rain garden consists of a planted depression area which allows stormwater runoff from building downspouts and surface runoff to be stored for infiltration and evapotranspiration. This measure can reduce storm runoff generated from the site and enhance the water quality of the runoff.



Bioretention areas: Bioretention areas capture surface runoff and provide water quality control and detention of stormwater runoff. The engineered subgrade provides storage for infiltration of storm runoff. This measure can reduce the runoff generated from the site through infiltration, enhance water quality, and reduce the peak flow rates.



Permeable pavement: Permeable pavement reduces the imperviousness of paved areas through the use of pervious interlocking paving stones. The engineered subgrade material beneath the permeable pavement provides storage of stormwater runoff for infiltration. This measure can reduce stormwater runoff and enhance infiltration.

215 Markham Road

The 215 Markham Road site presently consists of a high-rise residential building with both underground and surface parking areas, a daycare & playground area, and some landscaped areas. In order to improve the management of stormwater runoff the following stormwater management measures are proposed (Figure 4-2): 

Reforestation area: the reforestation area can increase the extent of infiltration and evapotranspiration through the selected vegetation species and engineered top soil medium. In addition, this feature will improve the biodiversity and aesthetic character of the site, while also enhancing the urban forest.



Rain garden attenuation area: The rain garden consists of a planted depression area which allows stormwater runoff from building downspouts and surface runoff to be stored for infiltration and evapotranspiration. This measure can reduce the storm runoff generated by the site and enhance the water quality of the runoff.



Bioretention areas: Bioretention areas capture surface runoff and provide water quality control and detention of stormwater runoff. The engineered subgrade provides storage for infiltration of storm runoff. This measure can reduce the runoff generated from the site through infiltration, enhance water quality, and reduce the peak flow rates.



Cistern for rainwater harvesting (underground garage): The underground cistern captures the clean rooftop runoff for landscape irrigation during the growing season. This measure reduces the stormwater runoff generate by the residential building area and also reduces the usage of municipal water.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 29

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 4-1: Recommended Stormwater Management Retrofit – Parkway Forest

PAGE 30 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 4-2: Recommended Stormwater Management Retrofit – Markham Road

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 31

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

200 Wellesley Street

The 200 Wellesley Street site presently consists of a residential apartment building with both underground and surface parking, a playground, a pool, and some landscaped area. In order to improve the management of stormwater runoff the following stormwater management measures are proposed (Figure 4-3): 

Water play area with UV disinfection: The water used for the water play area will be from the underground cistern which re-uses the runoff captured from the rooftop area.



Rainwater harvesting tank in underground parking for water play and irrigation system: Underground cistern captures the clean rooftop runoff for use in the water play area and for landscape irrigation during the growing season. This measure reduces the runoff generated by the residential building area and also reduces municipal water usage.



Bioretention areas: Bioretention areas capture surface runoff and provide water quality control and detention of stormwater runoff. The engineered subgrade provides storage for infiltration of runoff. This measure can reduce the runoff generated from the site through infiltration, enhance water quality, and reduce the peak flow rates.



Urban forest: Conversion of landscaped areas into urban forest will increase the extent of infiltration and evapotranspiration through the selected vegetation species and engineered top soil medium. In addition, these features will improve the biodiversity and aesthetic character of the site, while also enhancing the urban forest.



Permeable pavement: Permeable pavement reduces the imperviousness of paved areas through the use of pervious interlocking paving stones. The engineered subgrade material beneath the permeable pavement provides storage of stormwater runoff for infiltration. This measure can reduce runoff and enhance infiltration.

2667 & 2677 Kipling Avenue

The Kipling Avenue site presently consists of two residential apartment buildings with both underground and surface parking, two abandoned tennis courts, a filled-in swimming pool, and some landscaped area. In order to improve the management of stormwater runoff the following stormwater management measures are proposed (Figure 4-4): 

Constructed wetland: Constructing a wetland at the abandoned pool/court area can reduce significantly the impervious area of the site. Moreover, the wetland can provide water quality, erosion and water quantity control. The engineered subgrade material at the bottom of the wetland can provide storage for infiltration of runoff. Overall, the wetland can reduce both runoff volume and release rates from the site, enhance water quality, and provide erosion control. The amount of peak flow reduction depends on the size of the proposed wetland and any reduction in peak flow can reduce the required capacity of the downstream receiving sewer.



Bioretention areas: Bioretention areas capture surface runoff and provide water quality control and detention of runoff. The engineered subgrade provides storage for infiltration of stormwater runoff. This measure can reduce the runoff generated from the site through infiltration, enhance water quality, and reduce the peak flow rates.



Naturalized area: Naturalizing existing landscaped areas can increase the infiltration and evapotranspiration through the selected vegetation species and engineered top soil medium, while also improving biodiversity and the aesthetic character of the site.



Permeable pavement: Permeable pavement reduces the imperviousness of paved areas. The engineered subgrade beneath the permeable pavement provides storage of runoff for infiltration. This measure can reduce runoff and enhance infiltration.



Allotment gardens with cistern for irrigation: The allotment garden provides a desirable community amenity and enhances the aesthetic character of the site. Reusing the captured rooftop runoff from the cistern will reduce the runoff generated from the contributing rooftop area, and minimize the municipal water supply needed for garden irrigation.

PAGE 32 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 4-3: Recommended Stormwater Management Retrofit – Wellesley Street

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 33

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 4-4: Recommended Stormwater Management Retrofit – Kipling Avenue

PAGE 34 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

1765 & 1775 Weston Road

The Weston Road site presently consists of two residential apartment buildings with both underground and surface parking, a tennis court, a closed recreation centre, and some landscaped area. In order to improve the management of stormwater runoff the following stormwater management measures are proposed (Figure 4-5): 

Rooftop attenuation and flow redirection to scuppers and downspouts: Rooftop storage attenuates runoff and reduces the peak release rates from the building areas. Redirecting rooftop runoff to scuppers and downspouts allows for the conveyance of runoff to the landscapes areas and ultimately to the SWM or bioretention facilities. This measure will significantly reduce stormwater runoff from the building area and enhance infiltration within the site. The SWM and bioretention facilities will also provide enhanced water quality and quantity control.



Constructed wetland to attenuate surface runoff: The wetland can provide water quality, erosion and water quantity control. The engineered subgrade material at the bottom of the wetland can provide storage for infiltration of storm runoff. In general, the wetland can reduce both runoff volume and peak release rates from the site, enhance water quality, and provide erosion control.



Existing recreational centre to be demolished (pool to be converted to SWM detention facility): Constructing a SWM detention facility at the pool area inside the closed recreational centre will reduce the imperviousness of the site. Moreover, the SWM detention facility will provide water quality, erosion, and water quantity control. The amount of peak flow reduction depends on the size of the proposed SWM detention facility and any reduction in peak flow can reduce the required capacity of the downstream receiving sewer.



Existing sunken patio converted to wetland: As with the introduction of a SWM facility on the site of the recreation centre, constructing a wetland at the sunken patio area will reduce the impervious area of the site. Similarly, the wetland will reduce both runoff volume and release rates from the site, enhance water quality, and provide erosion control. The amount of peak flow reduction depends on the size of the proposed wetland and any reduction in peak flow can reduce the required capacity of the downstream receiving sewer.



Permeable pavement: Permeable pavement reduces the imperviousness of paved areas through the use of pervious interlocking paving stones. The engineered subgrade material beneath the permeable pavement provides storage of stormwater runoff for infiltration. This measure can reduce stormwater runoff and enhance infiltration.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 35

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 4-5: Recommended Stormwater Management Retrofit – Weston Road

PAGE 36 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

4.3

Quantification of Benefits Quantifying the benefits of the proposed Tower Renewal pilot site retrofits relies on the following assumptions: 

15 mm of rainfall capture under the LEED Gold criteria is set as the basis for the design and evaluation of the different measures, where applicable. The 15mm rainfall capture is selected as it represents a conservative and achievable standard.



The engineered subgrade material beneath the landscape/infiltration measures will have a minimum depth of 50 mm with a porosity of 0.3 over its entire area. This minimum depth of subgrade material ensures the capture of the 15mm rainfall.



The underground cistern is assumed to have capacity for the capture and storage of the runoff generated by a 15 mm rainfall over the contributing rooftop area.



The Pearson Airport rainfall data (1965-2002) has been applied in the average annual runoff calculation (see Section 2.2).



The Wet Weather Flow Management Guideline IDF curves have been applied for the return period runoff calculation (see Section 2.2).



The runoff coefficients for different surfaces are obtained from the Wet Weather Flow Management Guidelines.

The modeling methods for each of the proposed measures listed under Section 4.2 are summarized as follows: 

Cistern/Rainwater harvesting tank: Based on the assumption that 15 mm of the rainfall is to be captured from the contributing rooftop area. In order to model this measure, the cistern‟s contributing rooftop area base runoff coefficient (c = 0.95) will be adjusted to take into account the 15 mm rainfall capture under different return period storm events. Details of the runoff coefficient adjustment are provided in Appendix B.



Wetland/Bioretention/Rain garden areas: For the bioretention and rain garden measures, it is assumed that the subgrade material will be designed to capture the 15 mm rainfall event. In order to model this measure, the bioretention and rain garden area base runoff coefficient (c = 0.25) will be adjusted to take into account the 15mm rainfall capture under average annual and return period storm events. Details of the runoff coefficient adjustment are provided in Appendix B.



Urban Forest/ Reforestation area/Naturalized area: For the urban forest, reforestation areas, and naturalized areas, it is assumed that the designed top soil and subgrade material will have the capacity to capture the 15 mm rainfall. In order to model this measure, the urban forest, reforestation area, and naturalized area base runoff coefficient (c = 0.25) will be adjusted to take into account the 15mm rainfall capture under different return period storm events. Details of the runoff coefficient adjustment are provided in Appendix B.



Permeable pavement: The permeable pavement will be designed to capture the 15 mm rainfall through the engineered subgrade layer. In order to model this measure, the permeable pavement area base runoff coefficient (c = 0.95) will be adjusted to take into account the 15 mm rainfall capture under different return period storm events. Details of the runoff coefficient adjustment are provided in Appendix B.



SWM detention facility: The SWM detention facility has been modeled by assigning a runoff coefficient of 0.55, which represents an imperviousness of 50%. The 50% imperviousness of the SWM detention facility is based on the fact that the forebay area within the facility will be lined with concrete at the bottom for maintenance and sediment removal purpose. For return period events, the SWM facility will also serve to attenuate and reduce peak flows.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 37

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

However, determining the extent of the peak flow reduction requires a more detailed design of the detention facility, therefore the peak flow reduction associated with the SWM facility has not been quantified as part of this study.

The runoff volume generated from the five pilot sites with the implementation of the proposed SWM measures are summarized in Table 4-1. The percentage reduction of the runoff volume from the pilot sites are summarized in Table 4-2. The reduction of the runoff volume per unit area for each of the pilot site is summarized in Table 4-3. It should be noted that the adjusted 25 mm return period event runoff coefficients have been applied in the calculation of annual average runoff. Details of the calculations are provided in Appendix B.

Table 4-1: Runoff Volume – With Implementation of Proposed SWM/LID Measures

Site

Average Annual Runoff (m3)

Return Period Event Runoff Volumes (m3) 25 mm

2 Year

5 Year

10 Year

25 Year

50 Year

100 Year

Parkway Forest

8,257

259

319

482

584

688

824

925

Markham Road

5,784

184

225

341

414

488

585

658

Wellesley Street East

7,484

239

291

444

539

637

765

860

Kipling Avenue

7,850

250

305

461

560

661

791

890

Weston Road

6,079

194

232

343

412

483

575

643

Table 4-2: Percentage Reduction in Runoff Volume

Site

Average Annual Runoff Reduction (%)

Return Period Event Runoff Volume Reduction (%)

25 mm

2 Year

5 Year

10 Year

25 Year

50 Year

100 Year

Parkway Forest

14.3

15.6

12.2

8.4

7.0

6.1

5.0

4.5

Markham Road

16.0

16.0

13.6

9.4

7.8

6.8

5.6

5.0

Wellesley Street East

16.5

16.5

13.9

9.4

7.6

6.5

5.2

4.6

Kipling Avenue

23.7

23.7

21.4

17.9

16.3

15.5

14.5

13.9

Weston Road

9.3

9.3

8.2

6.4

5.7

5.3

4.8

4.5

Average

16.0

16.2

13.9

10.3

8.9

8.0

7.0

6.5

While the percentage runoff reduction from Table 4-2 is higher for the more frequent events, the greater volume of runoff generated by the less frequent events (see Table 2-2) yield slightly higher unit area runoff reductions, as shown in Table 4-3.

PAGE 38 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Table 4-3: Reduction in Runoff Volume per Unit Area

Site

Average Annual Runoff Reduction (m3/ha)

Return Period Event Runoff Volume Reduction (m3/ha)

25 mm

2 Year

5 Year

10 Year

25 Year

50 Year

100 Year

Parkway Forest

660

23

21

21

21

21

21

21

Markham Road

764

24

24

24

24

25

24

24

Wellesley Street East

807

26

26

25

24

24

23

22

Kipling Avenue

1052

34

36

43

47

52

58

62

Weston Road

386

12

13

15

15

17

18

19

Average

733

24

24

26

26

28

29

30

Reductions in return period event peak flows can be evaluated on the basis of the proportional change in the runoff coefficient from the existing to the proposed condition. This is premised on the Rational Method for estimating peak flow rates: Q = C x i x A, where Q is the flow rate, C is the runoff coefficient, i is the rainfall intensity, and A is the catchment area. Considering the existing and proposed conditions (with the implementation of the proposed LID/SWM techniques), the rainfall intensity, i, and area, A, remain constant. Therefore, a proportional change in peak flow, Q, can be estimated on the basis of the proportional change in the runoff coefficient C. Table 4-4 lists the existing and proposed runoff coefficients, and evaluates the proportional change in peak flow that could be expected through the implementation of the proposed LID/SWM measures. Runoff coefficient calculations are provided in Appendix B. Table 4-4: Estimated Reduction in Peak Flows

Site

Existing Runoff Coefficient (Cpre)

Proposed Runoff Coefficient (Cpost)

Peak Flow Reduction (%)

2 Year

5 Year

100 Year

2 Year

5 Year

100 Year

Parkway Forest

0.59

0.52

0.54

0.56

12.3

8.5

4.6

Markham Road

0.61

0.53

0.55

0.58

13.9

9.8

5.4

Wellesley Street East

0.62

0.54

0.56

0.59

13.5

8.9

4.1

Kipling Avenue

0.57

0.45

0.47

0.49

21.7

18.2

14.2

Weston Road

0.53

0.48

0.49

0.50

10.0

8.0

5.9

Average

0.55

0.50

0.52

0.54

14.3

10.7

6.8

The values in Table 4-2 and Table 4-4 have been averaged over the five pilot sites in order to determine the approximate runoff and peak flow reduction values for a typical site with the implementation of the identified SWM and LID measures. These average values yield the following notable conclusions:

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 39

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

16.0%

The reduction in average annual runoff volume achieved through implementation of the identified SWM and LID measures on a typical Tower Renewal site

10.3%

The reduction in runoff volume generated by a 5-Year Storm through implementation of the identified SWM and LID measures on a typical Tower Renewal site

10.7%

The reduction in peak flow generated by a 5-Year Storm through implementation of the identified SWM and LID measures on a typical Tower Renewal site

6.5%

The reduction in runoff volume generated by a 100-Year Storm through implementation of the identified SWM and LID measures on a typical Tower Renewal site

6.8%

The reduction in peak flow generated by a 100-Year Storm through implementation of the identified SWM and LID measures on a typical Tower Renewal site

On a volume per hectare of site area basis, the percentage reduction translates to a runoff 3 3 reduction of 733m /ha on an average annual basis and a reduction of 30m /ha during a 100year storm event. With about 1,000 sites that represent the full cohort of Tower Renewal properties, and an average site area of 1.86 hectares based on the five pilot sites (Section 2.3), implementing the proposed works would remove 1.36 million cubic metres of runoff presently draining to the City‟s storm infrastructure. The effectiveness of the proposed measures under frequent return period storm events is important since, as noted in Section 2.2, more than 50% of average annual rainfall events have a rainfall depth which is less than or equal to 5 mm. Capturing more frequent events can help achieve the water balance and erosion control objectives of the WWFMG. The peak flow reductions will directly relieve capacity in the receiving storm sewer systems during major events. It is important to note that the analysis of peak flow reductions has not included the additional peak flow attenuation that will occur through the installation of the proposed wetland and SWM detention facilities. The volume and outflow details of the proposed wetland and SWM detention facilities can and should be optimized to maximize peak flow reductions. This has particular relevance within the context of the City’s Basement Flooding Protection Program, where peak flow reductions from the Tower Renewal sites could lessen the extent of, or even eliminate the need for, infrastructure improvements required to address basement flooding concerns. 4.4

Costs A preliminary assessment of the costs associated with the proposed measures has been compiled for each of the pilot sites. The unit costs applied for the different measures are based on the following: 3



Cistern/Rainwater harvesting tank: $530/m of runoff stored (Low Impact Development SWM Planning and Design Guide)



Bioretention area and rain garden: $62,765/ha (Low Impact Development SWM Planning and Design Guide)



Wetland or SWM detention facility: $600,000/ha (based on previous projects in the Greater Toronto Area)

PAGE 40 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________ 2



Permeable pavement: $125/m (based on previous projects in the Greater Toronto Area)



Reforestation area: $68,750/ha (based on previous projects in the Greater Toronto Area)



Urban forest: $43,250/ha (based on previous projects in the Greater Toronto Area)



Naturalized area: $58,600/ha (based on previous projects in the Greater Toronto Area)

The complete cost breakdown and the overall cost for the five pilot sites are summarized in Table 4-5. It is important to note that these estimates are very preliminary and do not include engineering, contingencies, and related costs. These estimates are intended only to identify orders of magnitude for comparison purposes. Table 4-5: SWM/LID Measures Cost Analysis Pilot Site

Parkway Forest

Feature

Unit of measure

Cistern

m3

$

Rain garden Bioretention Areas Permeable Pavement

Cost per unit of measure

Total Units

Units

Total Cost of Feature

530.00

22.57

m3

$ 11,961.57

ha

$ 62,765.00

0.04

ha

$

2,525.85

ha

$ 62,765.00

0.15

ha

$

9,443.62

m2

$

735.70

m2

$ 91,962.50

125.00

Overall Cost

Markham Road

Reforestation Area

ha

$ 68,750.00

0.10

ha

$

6,822.75

Rain garden

ha

$ 62,765.00

0.06

ha

$

3,642.25

Bioretention Areas

ha

$ 62,765.00

0.10

ha

$

6,373.16

Cistern

m3

$

23.08

m3

$ 12,231.79

530.00

Overall Cost

Wellesley Street

m3

$

530.00

31.55

m3

$ 16,720.04

ha

$ 62,765.00

0.02

ha

$

Urban Forest

ha

$ 43,250.00

0.25

ha

$ 10,899.52

2

$ 37,716.25

m

2

$

125.00

301.73

m

Overall Cost Wetland Bioretention Areas Naturalized Areas Permeable Pavement Cistern

1,549.67

$ 66,885.48

ha

$ 600,000.00

0.12

ha

$ 69,790.20

ha

$ 62,765.00

0.12

ha

$

ha

$ 58,600.00

0.32

ha

$ 18,920.94

2

$ 23,290.00

2

$

125.00

186.32

m

m3

$

530.00

18.54

m3

m

Overall Cost

Weston Road

$ 29,069.95

Rainwater Harvesting Tank Bioretention Areas

Permeable Pavement

Kipling Avenue

$ 115,893.54

Wetland

ha

$ 600,000.00

Permeable Pavement SWM Detention Facility

m2

$

ha

$ 600,000.00

125.00

$

7,497.97

9,827.79

$ 129,326.90

0.09

ha

$ 55,278.00

697.40

m2

$ 87,175.00

0.03

ha

$ 20,904.00

Overall Cost

$ 163,357.00

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 41

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Table 4-6 summarizes the total costs associated with each pilot site LID/SWM concept in comparison to the estimated benefit in terms of runoff reduction. Table 4-6: Cost versus Benefit of Proposed LID/SWM Measures

Site

Average Annual Runoff Reduction (%)

100-Year Volume Reduction (%)

100-Year Peak Flow Reduction (%)

Parkway Forest

14.3

4.5

4.6

$

115,900

Markham Road

16.0

5.0

5.4

$

29,100

Wellesley Street East

16.5

4.6

4.1

$

66,900

Kipling Avenue

23.7

13.9

14.2

$

129,300

Weston Road

9.3

4.5

5.9

$

163,400

Average

16.0

6.5

6.8

$

100,900

Approximate Cost of LID/SWM Retrofit

Table 4-6 highlights the need for detailed evaluations of each Tower Renewal site in order to identify the combination of measures that will achieve the greatest reduction in runoff (both peak flows and volumes) for the minimum cost. Table 4-5 and Table 4-6 have identified an approximate average cost of undertaking LID/SWM retrofit works at each Tower Renewal site of about $100,000. As an additional comparison, a recent sewer improvement project undertaken by TMIG within the City yielded a sewer replacement cost of approximately $10,000 per linear metre.

This comparison emphasizes the value of considering the Tower Renewal LID/SWM improvements as a possible means to avoiding costly sewer upgrade works.

PAGE 42 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

4.5

Revitalization Concept Plan Given the large extent of open space associated with many of Toronto‟s tower buildings, these sites present a significant opportunity for revitalization that could be catalyzed by the addition of new development. The introduction of new development presents the opportunity to better achieve stormwater management targets in conjunction with a full suite of other sustainability objectives while at the same time rendering these sites as more functional, liveable and desirable. For example, the site located at 1765 Weston Road encompasses an extensive proportion of open space beyond the area of the footprint of the towers themselves. Much of this underutilized area fronts on Weston Road. This situation presents the opportunity to establish new built form along the Weston Road frontage of the site, taking advantage of this prime real estate for development purposes and enlivening the street. Figure 4-6 and Figure 4-7 (full size versions in Appendix C) provide illustrations of the potential for revitalization of the Weston Road tower site. The concept plan was designed to achieve a full spectrum of sustainability objectives within an integrated scheme that melds built form, landscape and infrastructure. The Revitalization Concept Plan envisions the implementation of new mixed use buildings along the Weston Road frontage of the site. These buildings would have retail at grade and commercial/office space above. New residential units would be constructed above this 2 – 3storey podium. This new building element would shelter the landscaped areas around the bases of the existing buildings that are presently windswept and underutilized. These spaces could then be remade to incorporate amenities that support health, well-being and community building objectives. Stormwater management would be addressed for both the refitted existing building and the new infill development utilizing various source and conveyance control techniques including: 

Green roofs



Bioretention cells



Rainwater harvesting



Constructed wetlands



Permeable pavement



Storm fountains



Infiltration galleries

Rainwater collected from rooftop areas will be re-used to irrigate allotment gardens, green roofs and landscape areas. The Revitalization Concept Plan also incorporates initiatives to achieve objectives related to the following: 

Urban agriculture and healthy food



Commerce and employment



Energy conservation and generation



Multi-modal transportation



Recreation and socialization



Enhanced bio-diversity



Urban forest enhancement



Water conservation

The implementation of the Revitalization Concept Plan would invigorate Weston Road, adding new commercial opportunities, contributing to street life and benefitting the character and ambiance of the neighbourhood. The Revitalization Concept Plan is intended to illustrate the tremendous potential that many of these tower sites hold to be transformed through the infusion of new development to become more liveable, sustainable assets within the City of Toronto.

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 43

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

Figure 4-6: Revitalization Concept Plan

PAGE 44 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

Figure 4-7: Revitalization Concept - Plaza View

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 45

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM __________________________________________________________________________________________________________________ MARCH 2011

5

Discussion and Next Steps Implementation of the stormwater management strategies identified as part of the Tower Renewal program will provide effective, practical, and economic solutions to the reduction of stormwater runoff that will exemplify the City of Toronto‟s commitment to achieving its sustainability objectives, and can assist in the relief of current issues such as basement flooding. Recommendations associated with the strategies include: 

Collecting detailed information regarding soil depths and soil types throughout the pilot sites, particularly above the underground parking garages to identify constraints and improve design of the stormwater management features.



Determining the exact extent of the underground parking facilities to more accurately size and locate the runoff reducing features and determining actual requirements for parking supply based on current demand and anticipated reductions resulting from potential improvements to the transit system and cycling infrastructure and resultant reductions in private automobile ownership and use.



Conducting site investigations to reveal each site‟s existing systems such as laundry and HVAC to determine the feasibility of employing the recommended stormwater strategies and expanding the opportunities for rainwater reuse.



Completing seasonal and / or daily water analysis to optimize the sizing of the stormwater management features and more accurately predict the volume of runoff reduction that can be utilized.



Completing hydrologic simulations in conjunction with the design of all attenuation features to optimize the reduction in peak flows generated during return period events, and so relieve wet weather flow capacity in the City‟s storm sewer infrastructure. This has specific relevance to the City‟s identified basement flooding protection priority areas, where Tower Renewal improvements could minimize or eliminate the need for sewer system upgrades.



Implementing the proposed LID and SWM measures at one or more Tower Renewal pilot sites to facilitate monitoring of the effectiveness of the measures and confirm the costs, challenges, and benefits to be realized through these works.

PAGE 46 ___________________________________ THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC.

Stormwater Management Feasibility Study CITY OF TORONTO TOWER RENEWAL PROGRAM MARCH 2011 ___________________________________________________________________________________________________________________

6

References 1. Augustenborg: Green roofs and storm water channels (Sustainable Cities, 2009) http://sustainablecities.dk/en/city-projects/cases/augustenborg-green-roofs-and-storm-water-channels 2. Best Practices for New Communities (The Regional Municipality of York, November 2007) http://www.york.ca/NR/rdonlyres/2syetdqhkkmsoujkcbvyyanrwmjznqxxc3knyi2wbcgwsfzdt4dbfugwhnx yaixlmzam7nklhv3mu7xroqkfkhyk3a/ncpubpackage.pdf 3. Corus Quay (Waterfront Toronto, 2010) http://www.waterfrontoronto.ca/explore_projects2/east_bayfront/corus_quay 4. Design Guidelines for Green Surface Parking Lots (Toronto City Planning, November 2007) 5. Evaluation of an Extensive Green roof (Sustainable Technologies Evaluation Program, 2010) http://www.sustainabletechnologies.ca/Portals/_Rainbow/Documents/GR_Factsheet_Aug06.pdf 6. Green Development Standard (City of Toronto, January 2010) 7. Low Impact Development (LID) Stormwater Management Planning and Design Guide (Toronto and Region and Credit Valley Conservation Authorities, 2010) 8. Jamshedpur: Reducing water shortage through rainwater harvesting (Sustainable Cities, 2007) http://sustainablecities.dk/en/city-projects/cases/jamshedpur-reducing-water-shortage-throughrainwater-harvesting 9. Performance Evaluation of Rainwater Harvesting Systems (Toronto and Region Conservation, 2010) http://www.sustainabletechnologies.ca/Portals/_Rainbow/Documents/FINAL%20RWH%202010%20%20Exec%20Summary.pdf 10. Permeable Pavement and Bioretention Swale Demonstration (Sustainable Technologies Evaluation Program, 2010) http://www.sustainabletechnologies.ca/Portals/_Rainbow/Documents/PP_FactsheetMay09.pdf 11. Porous Pavements in North America: Experience and Importance (Ferguson, B., 2010) http://documents.irevues.inist.fr/bitstream/handle/2042/35796/23606-342FER.pdf?sequence=1 12. Rainwater Harvesting Becomes a Mainstream Sustainable Practice (Gray, J. and Yudelson, J., 2004) http://www.starkenvironmental.com/downloads/Interface_Engineering.pdf 13. Stormwater Management (Sustainable Solutions International Pty Ltd, 2010) www.sustainablesolutionsinternational.com/pdf/Water Sensitive Urban Design.pdf 14. Stormwater Management Planning and Design Manual (MOE, March 2003) http://www.ene.gov.on.ca/environment/en/resources/STD01_076363.html 15. Taking the LEED in Water Conservation (Gray, J. and Yudelson, J., March 2002) www.csemag.com/index.php?=id-1398&cHash=081010&tx_ttnews[tt_news]=22595 16. Tower Renewal Guidelines for the Comprehensive Retrofit of Multi-unit Residential Buildings in Cold Climates (Kesik, T. and Saleff, I., University of Toronto, 2009) 17. Toronto Renewal Implementation Book (City of Toronto, June 2010) 18. Water Sensitive Urban Design for Greater Adelaide (Government of South Australia, January 2011) http://www.planning.sa.gov.au/go/wsud#whatiswsud 19. Wet Weather Flow Management Guidelines (City of Toronto, November 2006)

THE MUNICIPAL INFRASTRUCTURE GROUP LTD ▪ SCHOLLEN AND COMPANY INC. __________________________________ PAGE 47