629, 633 and 675 Eastern Avenue City of Toronto Toronto & East York District Functional Servicing and Stormwater Management Report June 2013 13029
Executive Summary This Functional Servicing and Stormwater Management Report (FSSR) has been prepared in support of the Re-Zoning Application being submitted for the subject lands generally bounded by Eastern Avenue to the north and Lake Shore Boulevard to the south, between Pape Avenue and Larchmount Avenue. The site is surrounded by residential development to the north; a two-storey film studio complex to the east; a number of commercial and industrial buildings to the south (other side of Lake Shore Boulevard); and a Subaru dealership and Diamond Towing company to the west. The proposed development integrates new office, hotel and retail/service uses with the existing Toronto Film Studios buildings which will be retained. This report demonstrates that the proposed development can be serviced through the utilization of both existing and new infrastructure, without any adverse impact to the municipal services of the surrounding areas or the existing studio buildings. Water supply and fire flow requirements for the proposed development will be provided from service connections feeding off the existing 300mm diameter watermain located on Eastern Avenue. Fire flow looping through an additional connection to the existing 300mm diameter watermain on Lake Shore Boulevard is provisional upon confirmation of a water flow test that the watermain on Eastern Avenue does not provide adequate fire flows. Flow and pressure tests are scheduled to be conducted on both watermains in the summer of 2013 to confirm if there is adequate capacity in the existing water distribution system to accommodate the proposed development for fire and non-fire demands. Post-development stormwater runoff collected from the new development portion of the subject site will be controlled on-site, stored via a combination of subsurface storage systems, and released to the municipal storm sewer system at controlled release rates. Storm runoff directed overland to the right-of-ways of the proposed private driveways and service lanes will be captured by the roadway catchbasins and directed to either the 1050mm diameter storm sewer west of the site or to the 525-900mm diameter storm sewer located on Lake Shore Boulevard, via the proposed internal storm sewer system. The proposed development will also be subject to the City s Wet Weather Flow guidelines for water balance and water quality control. Stormwater flows from major rainfall events exceeding the 100-year event will be conveyed overland to the adjacent municipal road allowances, and will ultimately outlet to the West Don River. Under the proposed development scenario, the sanitary peak flows for the site were determined to be approximately 15.4 litres per second. The existing sanitary flows peak rate of 13.1 litres per second. This flow increase is considered negligible as it will only be over a short 3.0m section of relatively steep sewer before discharging to the City of Toronto s 1680mm diameter Low Level Interceptor trunk sewer. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
The subject development is proposed to also include an internal driveway and service lane network. These proposed right-of-ways will have pavement widths of 7.0m and 10.0m respectively. Respectfully Submitted, The Sernas Group (A GHD Company) Shawn Huynh Rick Tranquada, P.Eng., M.B.A. Project Coordinator Regional Manager, Community Development 905 752 4372 905 752 4378 JL/SH/er GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
Table of Contents 1. Purpose...1 2. Background...2 2.1 Investigation of Existing Utilities on Site...3 2.2 Certificate of Property Use...4 3. Servicing Requirements...5 3.1 Watermains...5 3.2 Stormwater Management...7 3.3 Sanitary Sewers... 14 3.4 Proposed Road Network... 15 Figure Index Figure 2-1 Key Plan...3 Appendices Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F Fire Protection Computations Pre-development Drainage Plan Stormwater Management Calculations Sanitary Flow Calculations Reduced Proposed Site Plan Topographic / Boundary Survey Plan Certificate of Property Use GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
1. Purpose This Functional Servicing and Stormwater Management Report has been prepared in support of the Re-Zoning Application being submitted for the subject lands. The purpose of this report is to address conceptually the provision of site grading, storm and sanitary sewers, stormwater management (SWM), water distribution, and road servicing for the proposed commercial development. Additionally, the report will provide details on stormwater management in response to Toronto s Wet Weather Flow Management Master Plan Guidelines. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 1
2. Background The subject site is located south of Eastern Avenue and north of Lake Shore Boulevard, on the lands municipally known as 629, 633, and 675 Eastern Avenue, in the City of Toronto-Toronto East York District. The subject lands are bounded by Eastern Avenue to the north, existing commercial properties to the east and west, and Lake Shore Boulevard to the south. The westerly portion of the site is presently occupied and used by Toronto Film Studios. Several buildings occupy this portion of the site, and surfaces are generally paved. The easterly portion of the site is presently vacant but was formally occupied by the A.R. Clarke Tannery, which manufactured patent leather until 1977. According to old photographs, a large portion of the site was once covered with several buildings and pavement. Currently, only one building remains and the rest of the site is covered with a mixture of gravel and grass/overgrowth. A key plan indicating the site location has been provided as Figure 1.0 below. Storm runoff from the western portion of the site is captured by internal catchbasins, and directed to an existing 1050mm diameter storm sewer system along the western boundary of the site during minor storm events. The eastern portion of the site generally relied upon ground infiltration and several site catchbasins connecting to a combined sanitary/storm sewer to accommodate minor storm events. Eastern Avenue adjacent to the site is a typical urban street with curbs on both sides. The south boulevard is approximately 3.5m wide and contains a sidewalk located adjacent the curb. The north curb of the west-bound lane of Lake Shore Boulevard is located approximately 25m from the property boundary. This boulevard currently contains a 4m wide asphalt path, as well as a 1.5m wide concrete sidewalk. The proposed redevelopment will retain most of the existing buildings on the western portion and will incorporate six new buildings throughout the rest of the site. Where possible, existing building and boundary grades are maintained to avoid radical grade differences between the redeveloped site and the surrounding area. A copy of the proposed site plan is attached in Appendix E. 2 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
Figure 2.1 Key Plan *Source: Google Maps 2.1 Investigation of Existing Utilities on Site The following action was undertaken to ascertain the presence and location of possible utilities: City records were retrieved which showed storm sewer, sanitary, and watermain locations. The topographic survey identified manhole locations for the storm and sanitary sewer, and generally confirmed the existence and extent of these sewers. A detailed survey of the existing internal services in the Toronto Film Studios portion of the site which is to be retained, will be completed in order to establish a comprehensive servicing system. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 3
2.2 Certificate of Property Use The site is subject to a Certificate of Property Use (CPU) issued by the Ministry of the Environment to address Risk Management Measures (RMM) associated with a Risk Assessment conducted for the entire property. A copy of the Certificate of Property Use is included in Appendix F for reference. The RMM outlines a number of required measures to be implemented to ensure the property is suitable for the intended land use. As such, development of this site will undertake the necessary processes at the appropriate time in order to meet the requirements of the RMM. 4 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
3. Servicing Requirements 3.1 Watermains There is an existing 300mm diameter watermain located on Eastern Avenue and an existing 300mm watermain on the south boulevard of Lake Shore Boulevard. The location and size of the existing watermains in the surroundings of the subject lands have been determined from information obtained from the City of Toronto and topographic surveys. As mentioned in Section 2.1 above, the existing internal services will be surveyed and a servicing strategy between the existing and proposed portions of the site will be determined. At present, we are outlining requirements for hydrant fire-flow tests surrounding the site and will provide further details once results become available. Domestic Demand The City s Design Criteria for Sewers and Watermain, November 2009 (herein referred to as the City s Design Manual), does not define a specific method for determining domestic industrial water demand. As the development contains more than one building higher than a single storey, we have applied the City s multi-unit demand rate of 191 litres/capita/day as found in the City s Design Manual. Using an equivalent population density of 80 persons per hectare of floor-space, and a total on-site floor-space of 113,519m2 (11.4 ha), an equivalent population of 910 persons is calculated. Average Day = 191 litres/capita/day x 910 persons = 120.7 litres/min Maximum Day = 1.10 x Average Day = 132.8 litres/min Peak Hour = 0.90 x Average Day = 108.6 litres/min Fire Demand Based on the provided site plan, it is assumed that all new buildings will have protected openings (as defined by the Fire Underwriters Survey) and sprinkler systems. It is also assumed that all new buildings will be constructed of fire resistive material. Existing buildings are assumed to be constructed using conventional non-combustible materials and methods and are therefore not considered fire-resistive. Further, existing buildings are assumed to not have a fire suppression/sprinkler system installed. Given the above, the estimated fire flow required is given by the following formula (as based on the Fire Underwriters Survey): F = 220 * C * A^0.5 For a building with non-combustible construction, C = 0.8. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 5
A is taken as the area of the largest floor plus 25% of each of the two immediately adjoining floors. Based on the current site plan, the worst case fire flow is generated by Existing Building 11, with an Area = 4,221 m2. Therefore F = 11,440 litres/min. As this building is a number of years old and was used as a film studio stage, it can be surmised that construction consists of limited fire resistive material, therefore fire flow can be reduced by 15%. Thus F = 9,720 litres/min. Finally, the fire flow will be increased by 75% due to exposure to structures within 45 metres of Building 20. Thus, F = 16,370 litres/min. Fire Flow Demand calculations for each building can be found in Appendix A at the back of this report. Total Demand The total demand is the greater of Maximum Day Domestic Demand plus the Fire Demand or the Peak Hour Demand. Thus, the total demand for the site is approximately 16,370 litres per minute. To confirm that the existing system is adequate to meet the fire flow requirements for the proposed development, flow and pressure tests will be scheduled in the Spring of 2013. Connections to the proposed development will be provided from the existing 300mm diameter Eastern Avenue watermain and the existing 300mm diameter watermain on Lake Shore Blvd. The site will be serviced with two separate internal systems to meet fire and domestic requirements. The proposed 200mm looped watermain system providing fire demand will be connected at the intersections of Pape Avenue and Eastern Avenue, and the future southwest driveway from Lake Shore Boulevard including double-check valve chambers at each location. The latter connection is provisional upon confirmation (via a water flow test) of adequate flows from Eastern Avenue. Should it be determined that Eastern Avenue can provide the necessary flows for fire demand, the connection to Lake Shore Boulevard would not be required. The proposed 150mm watermain providing domestic demand will be connected at Winifred Avenue and Eastern Avenue. Fire hydrants will be placed to provide fire protection throughout the site. 6 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
Per the City s requirements, a water meter inside an underground chamber will be located at the connection for the domestic watermain. The exact size and location of the aforementioned connections and internal watermain are shown on our Functional Servicing Plan (Drawing FSP-1). 3.2 Stormwater Management Existing Conditions An existing 1050mm diameter storm sewer on the adjacent property west of the proposed development runs from Eastern Avenue to Lake Shore Boulevard and services the western portion of the existing site. It is our understanding from City staff that this 1050mm diameter storm sewer typically runs at capacity under minor storm events, and is approximately one-third full during dry-weather conditions. Given that the subject lands are approximately 1.0-2.0 m above the level of the lake, it can be inferred that this pipe naturally receives backflow from Lake Ontario. In addition to the 1050mm storm sewer, there is a minor local system on Eastern Avenue that primarily provides drainage for the road, and two systems along Lake Shore Boulevard (one along the west-bound lanes and one along the east-bound lanes), which flow toward the west. The pipes in the westbound lane range in size from 525mm dia. to 900mm dia., which indicates they have been sized to accommodate lands beyond the road right-of-way. This sewer system continues west to Carlaw Avenue, where it connects to a 2550x1800 box pipe trunk storm sewer that outlets directly to Lake Ontario, just south of Commissioner Street. Finally there is a 2750mm diameter trunk storm sewer along an easement within the east boundary of the site. According to City staff, this is a trunk very deep sewer that operates as a combined sewer overflow and storage system during high flows, and is eventually pumped back into the lake as flows subside. This trunk sewer runs directly to the Lake Ontario shoreline just south of Commissioner Street. The sizes and locations of all of existing storm sewers in the vicinity of the subject lands have been determined from information provided by the City of Toronto, including plan/profile records drawings, and topographic survey. As previously discussed, the site was originally occupied by industrial buildings and pavement. As such, the pre-development conditions for the subject site consist mainly of rooftop areas and paved areas (with very little to no landscaping) with some overgrowth. Under pre-development conditions, the majority of storm runoff from the site was captured by internal catchbasins, and directed to the aforementioned 1050mm diameter storm sewer and a combined sanitary/storm sewer on Lake Shore Boulevard during minor storm events. Storm flows from major storms events were conveyed overland to both the Lake Shore Boulevard and Eastern Avenue road allowances, where flows were eventually conveyed to Lake Ontario. The subject lands are within a TRCA designated floodplain. The TRCA defines flooding areas based on the 1:350 year storm event. The TRCA floodplain program has determined that the site lands are subject to the Don River Special Policy Area (SPA), with a flooding elevation of 77.70m. New buildings constructed within the subject lands GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 7
will be flood protected according to the Don River SPA by having all entrances and windows at least 0.30m above the flood elevation. Given the pre-development land use, 100-year pre-development storm flows for the site were determined to be approximately 497.0 L/s (NW area), 801.7 L/s (South area) and 1446.3 L/s (SW area) respectively (based on a runoff coefficient of 0.90). The predevelopment drainage plan is included in Appendix B. Stormwater Management Criteria The total site area is 7.48 hectares of which only 5.30 hectares is intended to be developed. The balance of the site consisting of 2.18 hectares (Existing Buildings 2,10 to 15, plus parking) will remain in its current state. As such, our SWM strategy is based on 5.30 hectares of redeveloped land. Based on City of Toronto s Wet Weather Flow Management Guidelines (WWFMG), the applicable SWM criteria are as follows: a) Contributing Area The area of 5.30 hectares associated with the redeveloped portion of the site, recognizing that 2.18 hectares of the site is existing and will be retained as part of the overall development, this area is excluded from the Wet Weather Flow Management calculations and results found in this FSSR. b) Water Quantity The 100-year post-development storm flows from the subject lands are to be controlled to the allowable release rate that is based on the lesser of the 2-year predevelopment flow, the 2-year rainfall event based on a composite runoff coefficient of 0.50, or the capacity of the receiving sewer. c) Water Balance On-site runoff retention from a 5mm, 24 hour storm event. d) Water Quality 80% removal of total suspended solids (TSS) on an average annual loading basis. e) Erosion & Sediment Control During Construction Temporary erosion and sediment control is to be implemented on-site during construction. f) Discharge Criteria to Municipal Infrastructure 8 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
Discharge the minor flow to the 2-year design storm event using the Rational Method / IDF Curves, or at the capacity of the sewer whichever is less. Proposed Conditions Water Quantity Based on our grading design and stormwater management concept for the proposed development, overland flow for the site is divided into three (3) major drainage areas. The Northwest portion of the site outlets to Eastern Avenue via the proposed driveway at the intersection of Winifred Avenue and Eastern Avenue; the Southwest portion of the site outlets to Lake Shore Boulevard via the proposed driveway west of Building 07; and the rest site drains towards the South, and outlets to Lake Shore Boulevard via the proposed driveway east Building 07. Separating the site into three catchment areas was required given the need to match into the existing flat lands of the surrounding area, the requirement to match existing building elevations that will be retained on-site, and the need to tie into existing sewers. Given the proposed site plan for the subject development, post-development runoff rates were calculated for the 100-year rainfall event as follows (modelling results for each area are presented in Appendix C ): a) Northwest Drainage Area 19,800 m 2 Our calculations were based on the following: Proposed rooftop areas comprised of controlled rooftop drainage and Green Roof tops where allowed for by the City s Green Roof By-Law 492. For this major drainage area, two new buildings will be constructed, allowing for a total of 978 m 2 of Green Roof space, 3,911 m 2 of controlled roof flow, and uncontrolled existing roof flow of 1200 m 2. An impervious / paved area of approximately 13,711 m 2. Given the above, the 100-year post development flow for the site was determined to be approximately 953.1 L/s. A storage volume of approximately 506 m 3 will be required to attenuate the post-development flow for this drainage area. This storage volume will be provided through the implementation of a subsurface impermeable (to prevent infiltration from the shallow groundwater table) storage system, the details of which will be established at the time of detailed design during the Site Plan Approval process. b) South Drainage Area 25,918 m 2 Our calculations were based on the following: Proposed rooftop areas comprised of controlled rooftop drainage and Green Roof tops where allowed for by the City s Green Roof By-Law 492. For this major drainage area, GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 9
three new buildings will be constructed, allowing for a total of 1,163 m 2 of Green Roof space and 10,955 m 2 of controlled roof flow. An impervious / paved area of approximately 13,800 m 2. Given the above, the 100-year post development flow for the site was determined to be approximately 889.8 L/s. A storage volume of approximately 373 m 3 will be required to attenuate the post-development flow for this drainage area. This storage volume will be provided through the implementation of a subsurface impermeable (to prevent infiltration from the shallow groundwater table) storage system, the details of which will be discussed further at the time of detailed design during the Site Plan Approval stage. c) Southwest Drainage Area 7,300 m 2 Our calculations were based on the following: Proposed rooftop areas comprised of controlled rooftop drainage and Green Roof tops where allowed for by the City s Green Roof By-Law 492. For this major drainage area, one new building will be constructed, allowing for a total of 1,000 m 2 of Green Roof space and 4,000 m 2 of controlled roof flow. An impervious / paved area of approximately 2,300 m 2. Given the above, the 100-year post development flow for the site was determined to be approximately 164.3 L/s. A storage volume of approximately 41 m 3 will be required to attenuate the post-development flow for this drainage area. This storage volume will be provided through the implementation of a subsurface impermeable (to prevent infiltration from the shallow groundwater table) storage system, the details of which will be discussed further at the time of detailed design during the Site Plan Approval stage. Water Balance The objective of the water balance target is to preserve pre-development hydrology through the combination of various SWM practices. According to the City s Wet Weather Flood Management Guidelines (WWFMG) guidelines the subject lands must be able to retain all the runoff from a small design rainfall event on site. The City defines a 5mm, 24-hour storm event as a small design rainfall event and is used for this calculation. This runoff must be retained through infiltration, evapotranspiration or rainwater reuse. Given a site area of 53,000 m 2 for the development, a 5mm, 24-hour storm is equivalent to approximately 265 m 3 of total site storage (53,000 m 2 x 0.005m). Under the City of Toronto stormwater management criteria and in accordance with the City s WWFMG, methods to enhance infiltration are to be implemented where possible. A few issues arise that affect the ability to implement on-site infiltration of runoff. The first issue is a shallow groundwater table. The existing groundwater table is approximately 0.5 m below 10 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
the existing surface therefore ground infiltration is very limited. The second issue is the presence of contaminated soils and groundwater on site. On this basis, we believe the City s Water Balance requirements for Wet Weather Flow by any infiltration techniques will be difficult to meet but will be reviewed in detail during detailed design stage. Rainwater harvesting whereby runoff is collected and stored for later use in irrigation is another option that was considered, however the proposed development has limited landscaping area, therefore rainwater harvesting methods would not be an economical solution. Other techniques such as grey-water collection/reuse and Green Roof retention for evapotranspiration are also viable options which can be examined further at the time of detailed design during the Site Plan Approval application stage of the project. Water Quality There are a number of Stormwater Management Practices (SWMPs) available to meet the various aspects of water quality control. However, site characteristics and the nature of the development will determine the applicability and possible usage of many of the different SWMPs. The stormwater management approach endorsed by the Ministry of the Environment (MOE) is to preserve the natural hydrologic cycle. As discussed in the March 2003 MOE manual, the establishment of water quality criteria in the absence of a subwatershed study will have a certain degree of subjectivity. The level of protection is selected such that the existing aquatic habitat is maintained or enhanced. The levels of protection identified in the manual are given as Basic, Normal, and Enhanced, where a watercourse requiring Basic protection has less stringent control requirements than one requiring Normal protection. However, the strategy acknowledges that individual development plans cannot explicitly address cumulative effects. Stormwater management measures are to be assessed in the following order: 1) stormwater lot level controls, 2) stormwater conveyance controls, and 3) end-of-pipe stormwater management facilities. Lot level controls would include such measures as: rainwater leaders discharging to infiltration areas; rainwater leaders discharging to a subsurface soakaway pits; reducing grassed site grading to a minimum of 0.5%; separate foundation drains and routing of storm runoff along grassed swales. Conveyance controls would include perforated storm sewers, pervious catchbasins, and grassed swales. The selection of conveyance control is very much dependent on municipal requirements. It must be an acceptable form of servicing for a municipality and the municipality must be willing to implement and maintain these controls. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 11
End-of-pipe facilities receive water from the conveyance system and discharges the water to the receiving system. The March 2003 MOE Stormwater Management Planning and Design (SWMPD) Manual includes nine categories of end-of-pipe facilities as follows; wet ponds, wetlands, dry ponds, infiltration basins, infiltration trenches, filter strips, buffer strips, sand filters, and oil/grit separators. Physical factors such as topography, soil stratification, depth to bedrock, depth to water table and drainage areas are factors to be assessed in determining SWMP type. The manual indicates that the selection and design of an end-of-pipe system in the absence of a subwatershed plan is driven by receiving water concerns. The selection of the appropriate water quality measure is based on four factors, namely: - physical suitability; - conformity with development plan; - cost; - technical effectiveness As defined by the March 2003 SWMPD Manual and as required by the City of Toronto s Wet Weather Flow Management Master Plan (WWFMMP) Guidelines, an Enhanced level of water quality control must be achieved for the subject site. As previously noted, under the post-development conditions, the majority of the site will consist of rooftop areas and paved areas, with minimal landscaped areas. As such, it is likely that specific on-site water quality control measures will be required for this development to achieve the City of Toronto s requirement for 80% TSS removal. Oil/Grit Separators will be sized based on the calculated contributing flows and installed at all three discharge points to meet the TSS targets. Erosion and Sediment Control Erosion and sediment control will be provided on-site during construction, including silt fence around the site perimeter, silt sacks on the external catchbasins adjacent to the site and a mud mat at the access point of the site to control mud tracking by construction traffic. Regular maintenance of the erosion / sediment control measures above will be implemented throughout the duration of construction. Discharge Criteria to Municipal Infrastructure The allowable release rates for the subject lands were calculated to be 106.6 L/s (NW area); 458.1 L/s (South area); and 351.5 L/s (SW area); which are based on the 2-year predevelopment rainfall event at a composite runoff coefficient of 0.50 for the subject lands. Our calculations are presented in Appendix C. As per the Flood Flow Management (FFM) criteria mandated by Toronto and Region Conservation Authority (TRCA), the 100-year post-development flows should be attenuated to the 2-year pre-development flow of approximately 175.1 L/s (NW area), 302.3 L/s (South 12 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
area) and 632.8 L/s (SW area) respectively. Our calculations are presented in Appendix C. Based on the above, the Discharge Criteria to Municipal Infrastructure criteria represents a more conservative approach for the Northwest and Southwest discharges to the existing 1050mm storm sewer adjacent to the west side of the site; the 100-year post-development to 2-year pre-development flow governs in the case of the South discharge point to the existing 900mm storm sewer on Lake Shore Boulevard. As such, these criteria will govern the SWM design. Summary of Proposed Storm Servicing Post-development storm flows from the site have been split into three (3) separate areas (Refer to Drawing EDP-1). Minor Flows are directed to either the existing 1050mm storm sewer immediately west of the subject lands or to the existing storm sewer on Lake Shore Boulevard. These flows converge at an existing 2550x1800 box culvert storm trunk sewer that discharges to Lake Ontario at Ashbridges Bay. The size and location of the proposed internal storm sewer and associated servicing connections are shown on our Functional Servicing Plan (Drawing FSP-1). Note that the new storm sewers, connections and appurtenances will be watertight to prevent surcharging from the shallow groundwater table and to mitigate potential contamination of storm flows. Calculations for the three catchment areas can be found in Appendix C. In summary: The 100-year post-development flow for the Northwest Drainage Area was determined to be approximately 953.1 L/s. A corresponding storage volume of approximately 506 m 3 will be required to control the 100-year post-development flow to the allowable level. The 100-year post-development flow for the Southern Drainage Area was determined to be approximately 889.8 L/s. A corresponding storage volume of approximately 373 m 3 will be required to control the 100-year post-development flow to the allowable level. The 100-year post-development flow for the Southwest Drainage Area was determined to be approximately 164.3 L/s. A corresponding storage volume of approximately 41 m 3 will be required to control the 100-year post-development flow to the allowable level. It should be noted the aforementioned storage volumes will be accommodated via an impermeable subsurface storage system, which will prevent infiltration from the shallow groundwater table. The details of this subsurface storage system will be discussed further at the time of detailed design during the Site Plan Approval stage. This report provides preliminary sizing and configuration details only. As previously discussed in the Water Balance discussion, given that post-development conditions will include mostly rooftop areas, paved areas and existing site conditions, on-site infiltration is not feasible. Therefore it is likely that the provision of on-site water quality control measures will also be required for the proposed development to achieve 80% TSS removal as outlined in the WWFMMP. Oil/grit separators installed at each discharge location, downstream of each storage tank, will achieve the required TSS requirements. GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 13
Site grading is to be such that storm flows greater than the 2-year rainfall event will be directed overland away from proposed buildings to the adjacent road allowances, and will ultimately drain to the West Don River. Existing drainage patterns on the adjacent properties will not be altered and stormwater runoff from the subject development will not be permitted to drain onto adjacent properties. Details of the proposed stormwater management measures will be outlined in a separate Stage-2 Stormwater Management Implementation Report to be prepared at the time of detailed design during the Site Plan Approval stage of the project. 3.3 Sanitary Sewers Existing Conditions According to drawings obtained from the City, a 300mm dia. local sanitary sewer exists on Eastern Avenue, approximately 2.5 m to 3.0 m below the road surface. This local sewer connects to a 1680 mm diameter sanitary trunk sewer (Toronto s Low Level Interceptor Sewer, or LLI) interceptor pipe at Caroline Avenue. The LLI is located underneath the westbound lane of Eastern Avenue. In addition to providing service for the buildings fronting Eastern Avenue, the local sewer also conveys the sewage from the local systems on Pape Avenue, Winnifred Avenue and Caroline Avenue to the Lower level interceptor. In addition to the above, a 300mm dia. sanitary sewer also exists under the northerly portion of the west-bound lane of Lake Shore Boulevard east of Larchmount Avenue. It slopes down toward the east and is at a depth of 2.5 to 3.0m below the road. The size and location of the existing sanitary sewers in the vicinity of the subject lands have been determined from information obtained from the City of Toronto, including plan/profile records drawings and topographic surveys. As mentioned in Section 2.1 above, the existing internal services will be surveyed and a servicing strategy between the existing and proposed portions of the site will be determined. Flows generated by the existing site are based on the following City of Toronto Design Criteria for Sewers and Watermain, dated November 2009: An industrial generation rate of 250 litres/person/day An equivalent population density of 136 persons/hectare. Peak generation factor of 3.80 based on the Harmon Peaking Factor equation An infiltration rate of 0.26 litres/second/hectare Given a site area of 7.48 hectares, a Peak Hour Sanitary flow of 13.1 L/s is calculated. Our calculations are provided in Appendix D. 14 GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029
Proposed Sanitary Servicing Contributing sanitary flows from the proposed development were calculated based on land and floor usage criteria defined by City of Toronto s Equivalent Population Density and Infiltration Rates. In summary: A commercial generation rate of 250 litres/person/day An equivalent population of 1.1 persons / 100m 2 of floor space for commercial. Total retail floor area of 113,519 m 2. Peak generation factor of 3.70 based on the Harmon Peaking Factor equation An infiltration rate of 0.26 litres/second/hectare. Given the above, a total Peak Hour Flow of 15.4 L/s is calculated. Calculations can be found in Appendix D. The proposed servicing design includes a new sewer connection the existing local sanitary system on Eastern Avenue at Caroline Avenue. Despite the flow increase relative to existing conditions, the existing receiving pipe on Eastern Avenue is 3.0m in length with a slope of approximately 17%. This translates to a negligible flow increase before discharging into the City of Toronto s 1680mm dia. Low Level Interceptor (LLI) trunk sanitary main within Eastern Avenue. The proposed internal sanitary sewer and proposed sanitary servicing connections are shown on our Functional Servicing Plan (Drawing FSP-1). Note that the new sanitary sewers, connections and appurtenances will be watertight to prevent surcharging from the shallow groundwater table. Construction of an impermeable sewer will ensure that the existing shallow groundwater table is not contaminated by raw sanitary sewage. In accordance with City of Toronto standards, backflow preventers will be provided for the proposed sanitary service connections. 3.4 Proposed Road Network The proposed development site includes a mix of private driveways and private service lanes. Driveways will have pavement widths ranging from 8.5m to 10.0m and service lanes will have 7.0m wide pavement. Concrete curb and gutter will be used to separate the paved areas from pedestrian and landscape areas. Site access is provided at four locations along Eastern Avenue, generally aligning with Pape Avenue, Winnifred Avenue, Caroline Avenue and Larchmount Avenue, and three locations along Lake Shore Boulevard GHD 629, 633 and 675 Eastern Avenue, City of Toronto Toronto & East York District Functional Servicing Report 13029 15