FUNCTIONAL SERVICING AND STORMWATER MANAGEMENT STUDY 405 TWEEDSMUIR AVENUE

Transcription

1 FUNCTIONAL SERVICING AND STORMWATER MANAGEMENT STUDY FOR CITY OF OTTAWA PROJECT NO.:

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3 FOR TABLE OF CONTENTS 1.0 INTRODUCTION Existing Conditions Required Permits / Approvals Pre-consultation GUIDELINES, PREVIOUS STUDIES, AND REPORTS Existing Studies, Guidelines, and Reports WATER SUPPLY SERVICING Existing Water Supply Services Water Supply Servicing Design Water Supply Conclusion WASTEWATER SERVICING Existing Wastewater Services Wastewater Design Wastewater Servicing Conclusions STORMWATER MANAGEMENT Existing Stormwater Services Post-development Stormwater Management Target Proposed Stormwater Management System Stormwater Servicing Conclusions EROSION AND SEDIMENT CONTROL UTILITIES CONCLUSION AND RECOMMENDATIONS DAVID SCHAEFFER ENGINEERING LTD. PAGE I

4 FIGURES Figure 1 Site Location TABLES Table 1 Water Supply Design Criteria Table 2 Water Demand and Boundary Conditions Proposed Conditions Table 3 Wastewater Design Criteria Table 4 Summary of Estimated Peak Wastewater Flow Table 5 Summary of Existing Peak Storm Flow Rates Table 6 Stormwater Flow Rate Summary Table 7 Stormwater Flow Rate Summary APPENDICES Appendix A Appendix B Appendix C Appendix D Pre-consultation Notes Water Supply Wastewater Collection Stormwater Management PAGE II DAVID SCHAEFFER ENGINEERING LTD.

5 FOR PROJECT NO.: INTRODUCTION David Schaeffer Engineering Ltd. (DSEL) has been retained to prepare a Functional Servicing and Stormwater Management Study in support of the site plan control application for redevelopment of 405 Tweedsmuir Avenue. As illustrated in Figure 1, the subject property is situated on the east side of Tweedsmuir Avenue, south of Richmond Rd, and within the City of Ottawa urban boundary. The property measures approximately ha and is currently zoned R4N[776]S Figure 1: Site Location 78 DAVID SCHAEFFER ENGINEERING LTD. PAGE 1

6 The proposed development involves the construction of a 4-storey building comprised of 16 residential apartments and a covered, at-grade parking area. A site plan, prepared by Douglas Hardie Architect (DHA), illustrating the proposed development layout is included in the Drawings/Figures section at the back of this report. The objective of this report is to provide sufficient detail to support site plan control approval with respect to the adequacy and availability of site servicing. 1.1 Existing Conditions The existing property consists of one single family home and surrounding front, side and rear yard landscaping in the form of grassed lawns and a few trees. The existing elevations surrounding the house range between 70.23m and 71.07, with split drainage sloping towards the front and rear property lines respectively from the front of the house. The subject property is serviced by the existing municipal watermain and separated storm and sanitary sewers. The City has undertaken a 2011 road and watermain rehabilitation project that included the installation of a new 200mm watermain along Tweedsmuir Ave. The existing Tweedsmuir Ave 375mm dia. sanitary sewer and 750mm dia. storm sewer remain. 1.2 Required Permits / Approvals The proposed development is subject to the municipal site plan control approval process. The City of Ottawa must approve the engineering design drawings and reports prior to the issuance of site plan control. 1.3 Pre-consultation Pre-Consultation with the City of Ottawa has been conducted via for the proposed development. Pre-consultation correspondence, along with the servicing guidelines checklist, are located in Appendix A. 1.4 Summary of Revisions March REV 2 DSEL received comments from the City of Ottawa dated February 23, 2012 concerning the October 2011-REV 1 submission for 405 Tweedsmuir Avenue. In addition an updated site plan was received from DHA dated March 20, In response the March REV 2 has been updated and revised to address any comments or adjustments. PAGE 2 DAVID SCHAEFFER ENGINEERING LTD.

7 2.0 GUIDELINES, PREVIOUS STUDIES, AND REPORTS 2.1 Existing Studies, Guidelines, and Reports The following studies were utilized in the preparation of this report. Ottawa Sewer Design Guidelines, City of Ottawa, November (City Standards) Ottawa Design Guidelines Water Distribution City of Ottawa, July 2010 (Water Supply Guidelines) Stormwater Planning and Design Manual, Ministry of the Environment, March (SWMP Design Manual) Ontario Building Code Compendium Ministry of Municipal Affairs and Housing Building Development Branch, January 1, 2010 Update (OBC) DAVID SCHAEFFER ENGINEERING LTD. PAGE 3

8 3.0 WATER SUPPLY SERVICING 3.1 Existing Water Supply Services The subject property lies within the 1W pressure zone, and the site is currently services by an existing 200mm dia. watermain within Tweedsmuir Avenue. 3.2 Water Supply Servicing Design Table 1 summarizes the Water Supply Guidelines employed in the preparation of the preliminary water demand estimate. Table 1 Water Supply Design Criteria Design Parameter Residential 1 Bedroom Apartment 1.4 P/unit Residential 2 Bedroom Apartment 2.1 P/unit Residential Average Daily Demand 350 L/d/P Residential Maximum Daily Demand 3.6 x Average Daily * Residential Maximum Hourly 5.4 x Average Daily * Commercial Average Daily Demand (Retail) 2.5 L/m 2 /d Value Residential Maximum Daily Demand 1.5 x Average Daily Residential Maximum Hourly 1.8 x Maximum Daily Minimum Watermain Size 150mm diameter Minimum Depth of Cover 2.4m from top of watermain to finished grade During Peak Hourly Demand operating pressure 350kPa and 480kPa must remain within During normal operating conditions pressure must 275kPa not drop below During fire flow operating pressure must not drop 140kPa below * - Residential Max. Daily and Max. Hourly peaking factors as per MOE Guidelines for Drinking-Water Systems Table 3-3 for 0 to 500 persons. Table 2 Water Demand and Boundary Conditions Proposed Conditions Design Parameter Anticipated Demand 1 Boundary Condition 2 (L/min) Average Daily Demand kpa / 43.7 m-h 2 O (Max Press.) Max Day + Fire Flow = kpa Peak Hour kpa / 38.3 m-h 2 O 1) Water demand calculation per Water Supply Guidelines. See Appendix B for detailed calculations. 2) Boundary conditions supplied by the City of Ottawa. Assumed ground elevation 70.00m. See Appendix B. PAGE 4 DAVID SCHAEFFER ENGINEERING LTD.

9 Table 2 summarizes the anticipated water supply, demand and boundary conditions for the proposed development based on the Water Supply Guidelines.and site boundary conditions supplied from the City of Ottawa. Refer to Appendix B for correspondence and calculations. Section of the City Design guidelines for water distribution provides guidance for determining the method for estimating Fire Demand. As indicated, the requirements for levels of fire protection on private property are covered in the Ontario Building code. Section of the OBC addresses the installation of water service pipes and fire service mains. Part 3 of the OBC outlines the requirement for Fire Protection, Occupant Safety, and Accessibility; and sub-section A provides the provisions for fire fighting. Based on trained personnel responding to the emergency, and water supply being delivered through a municipal system, the required minimum provision for water supply shall not be less than 2,700L/min or greater than 9000L/min (OBC Section A , Table 2). Therefore, a conservative estimate for the required fire supply is 9000L/min. A certified fire protection system specialist shall be employed to design the building fire suppression system(s) and confirm the actual fire flow demand. 3.3 Water Supply Conclusion The boundary condition information provided from the City of Ottawa supports the estimated water demand calculated for the proposed development. As demonstrated in Table 2, the recommended pressure range is respected during peak hour demands and at maximum system pressure. A pressure check should be conducted at the completion of construction to determine if pressure control is required. DAVID SCHAEFFER ENGINEERING LTD. PAGE 5

10 4.0 WASTEWATER SERVICING 4.1 Existing Wastewater Services Wastewater generated from the site ultimately outlets to the West Nepean Collector on Scott Street via the existing 375mm diameter sanitary sewer that runs north along Tweedsmuir Avenue. 4.2 Wastewater Design Table 3 summarizes the City Standards employed in the design of the proposed wastewater sewer system. Table 3 Wastewater Design Criteria Design Parameter Value Residential 1 Bedroom Apartment 1.4 P/unit Residential 2 Bedroom Apartment 2.1 P/unit Average Daily Demand 350 L/d/per Peaking Factor Harmon s eaking Factor Max 4 0, Min 2 0 Infiltration and Inflow Allowance 0.28L/s/ha Sanitary sewers are to be sized employing the Manning s quation Q AR S n Minimum Sewer Size 200mm diameter Minimum Manning s n Minimum Depth of Cover 2.5m from crown of sewer to grade Minimum Full Flowing Velocity 0.6m/s Maximum Full Flowing Velocity 3.0m/s Extracted from Sections 4 and 6 of the City of Ottawa Sewer Design Guidelines, November Table 4 demonstrates the estimated wastewater flow generation from the proposed site development. Refer to Appendix C for associated calculations. Table 4 Summary of Estimated Peak Wastewater Flow Design Parameter Flow (L/s) Average Dry Weather Flow Rate 0.15 Peak Dry Weather Flow Rate 0.60 Peak Wet Weather Flow Rate 0.62 o evaluate the existing local sanitary sewer network s ability to support the proposed site development, the catchment area serviced by the Tweedsmuir Avenue sanitary sewer was identified and evaluated by reviewing existing development and zoning within the area, and employing the City of Ottawa Sewer Design Guidelines (2004) Figure 4 3 Peak Flow Design Parameters to generate a conservative estimate of the existing wastewater flow conditions within the sewer. It is estimated that the local sanitary sewer system downstream of the site is currently operating at a maximum of PAGE 6 DAVID SCHAEFFER ENGINEERING LTD.

11 67% of the full flowing capacity, with ample capacity to accommodate the estimated 0.53 L/s peak wastewater flow increase that will be generated by the proposed site development. Refer to Appendix C for associated figures and calculations. 4.3 Wastewater Servicing Conclusions The proposed wastewater design conforms to all relevant City guidelines. Based on a capacity analysis of the local upstream and downstream sewers there is sufficient capacity for the proposed development. The capacity analysis is summarized in the Sanitary Sewer Calculation Sheet and area map located in Appendix C. Therefore, the site has adequate wastewater servicing available. 5.0 STORMWATER MANAGEMENT 5.1 Existing Stormwater Services The subject lands are located within Ottawa Central sub-watershed which is under the Rideau Valley Conservation Authority jurisdiction. It was determined that the existing development contained no stormwater management controls for flow attenuation. The estimated pre-development peak flows for the 2, 5, and 100-year are summarized in Table 5: Table 5 Summary of Existing Peak Storm Flow Rates City of Ottawa Design Storm Estimated Peak Flow Rate (L/s) 2-year year year Post-development Stormwater Management Target Stormwater management design requirements for the proposed development were reviewed with the City of Ottawa as summarized in the pre-consultation correspondence included in Appendix A. Due to the relatively small size of the subject property (<0.2ha), the stormwater management restriction imposed on the site is to include a 75mm vertical orifice restriction in the parking lot catchbasin to restrict the stormwater release rate from this area to less than 15 L/s Proposed Stormwater Management System As a manner of introducing best management practices, and in order to achieve the stormwater objectives for the proposed development, the site stormwater management DAVID SCHAEFFER ENGINEERING LTD. PAGE 7

12 design employs a combination of surface and subsurface storage in addition to roof top drainage restriction and storage. Surface and subsurface storage is available within the common parking area by introducing a 75mm diameter vertical orifice Inlet Control Device (ICD) into the outlet of the proposed catchbasin. Implementation of the 75mm ICD will restrict stormwater release from the parking lot area to a maximum flow rate of 14.6 L/s. It is not anticipated that stormwater storage will accumulate within the parking area as the rate of runoff in this area is not expected to exceed that of the flow restriction device. Roof top storage will be controlled via notched roof drains. The release rate and storage calculations for roof top attenuation have been estimated based on Zurn Industries Ltd. design guidelines for Model Z Control-Flo Single Notch drains. Other products may be specified provided that the restricted release rate and sufficient storage are provided in the roof design to meet or exceed the values summarized in Table 6. Design Storm Event Table 6 Stormwater Flow Rate Summary Restricted Rooftop Release Rate Rooftop Storage Required Average Depth of Ponding Approx. Draw Down Time (L/s) (m 3 ) (mm) (hr) 5-year year Table 7 summarizes the pre-development release rate, the target flow rate, postdevelopment flow rates. Design Storm Event Table 7 Stormwater Flow Rate Summary Pre-development Release Rate Target Release Rate Post-Dev Peak Release Rate Total Required Storage (L/s) (L/s) (L/s) (m 3 ) 5-year year Detailed stormwater management calculations are provided in Appendix D. Figure SWM-1 illustrates the site drainage characteristics. 5.4 Stormwater Servicing Conclusions The proposed stormwater management design conforms the design objectives, and the proposed stormwater management target results in a reduction in peak flow from existing conditions. PAGE 8 DAVID SCHAEFFER ENGINEERING LTD.

13 6.0 EROSION AND SEDIMENT CONTROL Soil erosion occurs naturally and is a function of soil type, climate and topography. The extent of erosion losses is exaggerated during construction where vegetation has been removed and the top layer of soil becomes agitated. Prior to topsoil stripping, earthworks or underground construction, erosion and sediment controls will be implemented and will be maintained throughout construction. Silt fence will be installed around the perimeter of the site and will be cleaned and maintained throughout construction. Silt fence will remain in place until the working areas have been stabilized and re-vegetated. Catch basins will have filter fabric installed under the grate during construction to protect from silt entering the storm sewer system. A mud mat will be installed at the construction access in order to prevent mud tracking onto adjacent roads. Erosion and sediment controls must be in place during construction. The following recommendations to the contractor will be included in contract documents. Limit extent of exposed soils at any given time. Re-vegetate exposed areas as soon as possible. Minimize the area to be cleared and grubbed. Protect exposed slopes with plastic or synthetic mulches. Install silt fence to prevent sediment from entering existing ditches. No refueling or cleaning of equipment near existing watercourses. Provide sediment traps and basins during dewatering. Install filter cloth between catch basins and frames. Plan construction at proper time to avoid flooding. Establish material stockpiles away from watercourses, so that barriers and filters may be installed. The contractor will, at every rainfall, complete inspections and guarantee proper performance. The inspection is to include: Verification that water is not flowing under silt barriers. Clean and change filter cloth at catch basins. DAVID SCHAEFFER ENGINEERING LTD. PAGE 9

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