HOTEL KANATA 140 HEARST WAY KANATA, ONTARIO STORMWATER MANAGEMENT REPORT. Prepared for: David Johnston Architect. Prepared By:

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1 HOTEL KANATA 140 HEARST WAY KANATA, ONTARIO STORMWATER MANAGEMENT REPORT Prepared for: David Johnston Architect Prepared By: BaseTech Consulting Inc. 309 Roywood Crescent Newmarket, Ontario L3Y 1A6 BCI Project No April, 2015

2 TABLE OF CONTENTS Page No. 1. INTRODUCTION EXISTING SITE CONDITIONS QUANTITY CONTROL MAJOR FLOW ROUTE CONVEYANCE QUALITY CONTROL WATER BALANCE SUMMARY... 6 APPENDIX 1 APPENDIX 2 APPENDIX 3 RETENTION VOLUME CALCULATIONS STAGE-STORAGE-DISCHARGE CALCULATIONS OIL/GRIT SEPARATOR DETAILS

3 HOTEL KANATA STORMWATER MANAGEMENT REPORT April, INTRODUCTION The site is located at 140 Hearst Way in Kanata as shown on the Site Plan prepared by David Johnston Architect. The existing site measures ha. and is vacant at present It is proposed to construct a three storey hotel with associated access and parking on the site with access to Hearst Way. This report examines the impacts the proposed development will have on the run-off and sedimentation from the site and measures to mitigate those impacts. The Report has used the following documentation in its preparation: 1. Site Plan prepared by David Johnston Architect. 2. The current City of Ottawa Design Guidelines and Drawings. 3. The current Missippi Valley Conservation Authority Guidelines. 4. Stormwater Management Planning and Design Manual by the Ministry of the Environment, dated March EXISTING SITE CONDITIONS The site existing site drains via overland sheet flow to the northeast corner of the site adjacent to Highway 417. The east side of the site is crossed by a 1200 mm diameter storm sewer and 600 mm sanitary sewer. The underlying soil conditions for the site consist of sensitive silty clay overlain by topsoil and silty sand/ sandy silt in places. 3. QUANTITY CONTROL The site is within the Kanata Town Centre, Stage A area which allows for a pre-development runoff coefficient of 0.7 and a time of concentration of 20 minutes. The City of Ottawa requires that post-development run-off shall match the pre-development runoff for the year storm events based on a post-development time of concentration of 10 minutes. Any excess runoff will be retained on site and discharged at pre-development rates so the there is no impact on the existing stormwater management regime. BaseTech Consulting Inc. Consulting Engineers 1

4 HOTEL KANATA STORMWATER MANAGEMENT REPORT April, 2015 Rainfall Distributions and Flows Rainfall intensities are be based on the City of Ottawa Rainfall Intensity-Duration-Frequency Curves as defined by the following equation and values: I = A mm/m (T d +C) B Storm A B C 2 year year year year year year and T d = duration (min.) Calculation of the post-development runoff coefficients is be based on the following impermeability factors: 2 10 Year 25 Year 50 Year 100 Year Buildings Paving Gravel Grass/Landscape The runoff coefficients for the lower figures have been increased for the 25, 50 and 100 year storms by 10%, 20% and 25% respectively as recommended by MTO Design Chart Discharges are calculated using the formula Q = 2.78C*I*A where Q = discharge (l/sec) A = area (ha) C = impermeability factor I = rainfall intensity (mm/hr) BaseTech Consulting Inc. Consulting Engineers 2

5 HOTEL KANATA STORMWATER MANAGEMENT REPORT April, 2015 Pre-development flows were calculated based on a time of concentration of 20 minutes for each storm. The 2 10 year Post-Development characteristics for the site are as follows: Building = Paving = Grass/Landscape = TOTAL The Post-Development Impermeability Factor = = The 25 year, 50 year and 100 year Post-Development Impermeability Factors increase to 0.66, 0.67 and 0.68 respectively. Retention volumes are be calculated based on the equation; V = (Post-Development Flow Pre-Development Flow) x T x 60 cu.m Drainage from the site will be controlled using an orifice tube at the outlet from the site. The discharge through the orifice tube will be controlled to the 2 year pre-development flow. Based on a time of concentration of 20 minutes the 2 year pre-development flow will be; Q Pre2 = 2.78 x x 0.70 x = 61.40l/sec. The 100 year post-development flow, based on a 10 minute time of concentration, will be Q Post100 = 2.78 x x 0.68 x = l/sec. The retention volume will be; V 100 = ( ) x 10 x = 85.98m 3 This was carried out for the other storms and the retention volumes are shown in Table 1 BaseTech Consulting Inc. Consulting Engineers 3

6 HOTEL KANATA STORMWATER MANAGEMENT REPORT April, 2015 TABLE 1 STORM PRE-DEVELOPMENT FLOW (l/sec.) RETENTION VOLUME (cu.m.) 2 Year Year Year Year Year Year Details of the retention volumes are shown in Appendix 1 4. MAJOR FLOW ROUTE The major flow route will continue to be towards the northeast corner of the site. 5. CONVEYANCE The development will be serviced by a catchbasin and storm sewer system connecting to the existing 1200 mm diameter storm sewer in Hearst Way. Prior to leaving the site the flow will be controlled to the 2 year Pre-development flow of l/sec. during the 2 year storm event. Control will be provided by placing a Hydrovex 200 VHV-2 flow regulator on the outlet from DCB MH1. Details for the Hydrovex are shown in Appendix 2 along with the Stage-Storage-Discharge details. The head over the flow regulator will be 1.75m and, with an invert of m, the 2 year retention level will be m. The depth of ponding during the 2 year event will be m giving a bottom of retention elevation of m. BaseTech Consulting Inc. Consulting Engineers 4

7 HOTEL KANATA STORMWATER MANAGEMENT REPORT April, QUALITY CONTROL The Mississippi Valley Conservation Authority requires that all parking and access areas be provided with a facility to prevent fuel spills and sediment from entering the storm system. Therefore, an oil/grit separator, PMSU m will be provided to control any spillages/debris in the run-off. This should be designed to remove at least 70% of suspended solids from the runoff. Details are shown in Appendix 3. Regular maintenance of the oil/grit separator will be required to be carried out to the manufacturer s recommendations. Maintenance of the system should initially be carried out annually and the amount of sediment and oil accumulating monitored to assess the need to increase/decrease maintenance. Sedimentation and erosion controls should be provided during construction using the following techniques depending on site development phasing and seasonal considerations: 1) Filter cloth and snow fencing along the property boundaries. 2) Mud mat at the construction entrance. 3) Stone/filter cloth protection on catchbasins. 4) Grassing of all required areas on completion of grading. All sedimentation and erosion control measures should be carried out in accordance with current City of Ottawa and Ministry of Natural Resources guidelines. The control measures should be checked on a regular basis and after each rainfall event and repaired as necessary. 7. WATER BALANCE Due to the size of the site and the existing underlying soil conditions it is felt that the proposed development will not have an impact on the existing groundwater conditions. BaseTech Consulting Inc. Consulting Engineers 5

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9 APPENDIX 1 RETENTION VOLUME CALCULATIONS

10 RETENTION VOLUME CALCULATIONS POST-DEVELOPMENT FLOWS Discharges are calculated using the formula Q = 2.78C*I*A where Q = discharge (l/sec) A = area (ha) C = impermeability factor I = rainfall intensity (mm/hr) Time of concentration = 10 minutes Q 2POST = 2.78 x 0.62 x x = 80.28l/sec. Q 5POST = 2.78 x 0.62 x x = l/sec. Q 10POST = 2.78 x 0.62 x x = l/sec. Q 25POST = 2.78 x 0.66 x x = l/sec. Q 50POST = 2.78 x 0.62 x x = l/sec. Q 2POST = 2.78 x 0.62 x x = l/sec. Controlled flow = 61.40l/sec. RETENTION VOLUMES V 2 = ( ) X 10 X 60/1000 = 11.33m 3 V 5 = ( ) X 10 X 60/1000 = 27.85m 3 V 10 = ( ) X 10 X 60/1000 = 39.76m 3 V 25 = ( ) X 10 X 60/1000 = 59.72m 3 V 50 = ( ) X 10 X 60/1000 = 75.59m 3 V 100 = ( ) X 10 X 60/1000 = 85.98m 3

11 APPENDIX 2 STAGE-STORAGE-DISCHARGE CALCULATIONS

12 HOTEL KANATA 140 HEARST WAY STAGE-STORAGE-DISCHARGE CALCULATIONS April, 2015 STORM DEPTH ELEV. VOLUME HEAD DISCHARGE m. m. cu.m. m. l/sec YEAR YEAR YEAR YEAR YEAR YEAR

13 APPENDIX 3 OIL/GRIT SEPARATOR DETAILS

14 Project Name: 140 Hearst Way Engineer: Basetech Consulting Inc. Location: Ottawa, ON Contact: Peter Feherty, M.Sc., P.Eng. OGS #: - Report Date: 4-Mar-15 Area ha Rainfall Station # 215 Weighted C 0.62 Tc 10 minutes Particle Size Distribution FINE CDS Model CDS Treatment Capacity 20 l/s Rainfall Intensity 1 (mm/hr) CDS ESTIMATED NET ANNUAL SOLIDS LOAD REDUCTION BASED ON THE RATIONAL RAINFALL METHOD BASED ON A FINE PARTICLE SIZE DISTRIBUTION Percent Rainfall Volume 1 Cumulative Rainfall Volume Total Flowrate (l/s) Treated Flowrate (l/s) Operating Rate (%) Removal Efficiency (%) Incremental Removal (%) % 9.2% % 19.8% % 29.7% % 38.1% % 45.8% % 51.7% % 56.1% % 60.7% % 64.0% % 67.1% % 72.4% % 76.8% % 80.3% % 83.2% % 85.3% % 92.3% % 96.9% % 98.3% % 99.0% % 99.5% % 100.0% % 100.0% % 100.0% % 100.0% % 100.0% Removal Efficiency Adjustment 2 = Predicted Net Annual Load Removal Efficiency = Predicted % Annual Rainfall Treated = 1 - Based on 42 years of hourly rainfall data from Canadian Station , Ottawa ON 2 - Reduction due to use of 60-minute data for a site that has a time of concentration less than 30-minutes 6.5% 83.3% 98.1%

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