GLOBAL CENTRE FOR PLURALISM 330 Sussex Drive Ottawa, Ontario SITE SERVICING & STORMWATER MANAGEMENT OVERVIEW UPDATE REPORT.

Size: px

Start display at page:

Download "GLOBAL CENTRE FOR PLURALISM 330 Sussex Drive Ottawa, Ontario SITE SERVICING & STORMWATER MANAGEMENT OVERVIEW UPDATE REPORT."

Robyn Nash
5 years ago
Views:

GLOBAL CENTRE FOR PLURALISM 330 Sussex Drive Ottawa, Ontario SITE SERVICING & STORMWATER MANAGEMENT OVERVIEW UPDATE REPORT Submitted to: Kuwabara Payne McKenna Blumberg

1 GLOBAL CENTRE FOR PLURALISM 330 Sussex Drive Ottawa, Ontario SITE SERVICING & STORMWATER MANAGEMENT OVERVIEW UPDATE REPORT Submitted to: Kuwabara Payne McKenna Blumberg Architects 322 King Street West, Third Floor Toronto, Ontario M5V 1J2 Submitted by: Delcan Corporation 1223 Michael Street, Suite 100 Ottawa, Ontario K1J 7T2 EO2420EOA January 2014

2 Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page i CONTENTS 1 INTRODUCTION PURPOSE EXISTING CONDITIONS PROPOSED DEVELOPMENT STORMWATER MANAGEMENT PLAN PRE-DEVELOPMENT CONDITIONS POST-DEVELOPMENT CONDITIONS SANITARY SEWER PRE-DEVELOPMENT CONDITIONS POST-DEVELOPMENT CONDITIONS WATERMAIN CONCLUSIONS AND RECOMMENDATIONS... 6 APPENDICES: Appendix A Drawings Drawing M-1 Drainage Area Plan/Existing Site Plan Drawing M-2 Drainage Area Plan/Proposed Site Plan Drawing M-3 Conceptual Site Servicing Appendix B Stormwater Management Calculations Appendix C Fire Flow Calculations

1 INTRODUCTION Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page 1 Delcan Corporation was retained by Kuwabara Payne McKenna Blumberg

3 1 INTRODUCTION Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page 1 Delcan Corporation was retained by Kuwabara Payne McKenna Blumberg Architects (KPMB) to provide municipal engineering services for the proposed rehabilitation of the former War Museum building, which will house the new Global Centre for Pluralism (GCP). The site is located at 330 Sussex Drive, in Ottawa, Ontario. The site encompasses a total area of approximately 0.56 hectare (ha) bordered by the Royal Canadian Mint building to the north, the National Gallery of Canada to the South, Sussex Drive to the east and Lady Grey Drive to the west. The location of the site is shown on Figure 1. Figure 1: Key Plan 2 PURPOSE As a result of discussions with the City of Ottawa, it was determined that the rehabilitation of the site would be subject to stormwater management requirements for quantity control and possibly quality control at the rear of the building. As such, this report has been prepared to describe the stormwater management requirements for the site. In addition to the stormwater management requirements, this report describes the sanitary and water servicing requirements for the site. The pre- and post-development analysis completed as part of this report was based on desktop information provided by KPMB and other sources, including anecdotal information. Field investigations of the existing underground services (i.e. topographic survey, subsurface utilities investigation, CCTV

4 Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page 2 inspection, etc.) would have to be completed as part of the next stage of the project to confirm the location, size, condition and capacity of existing services and to confirm the existing grading and drainage. Until the condition and capacity of the existing services has been confirmed it is assumed that new services will be provided. 3 EXISTING CONDITIONS The subject site mainly consists of a three-storey building with a below grade basement, a large forecourt used for parking, Bruyere Laneway and relatively small grassed areas with medium sized trees. The building is currently unoccupied, but, it formerly housed the War Museum. Topography is generally flat with the back of the building sloping westerly towards Lady Grey Drive. The Sussex Drive Reconstruction project is currently underway. This project includes the replacement and upgrading of the underground infrastructure in Sussex Drive in the immediate vicinity of the site. As a result, the existing combined sewer on Sussex Drive is currently being replaced by a separated sewer system (i.e. sanitary and storm sewers) and the existing watermain is being replaced. Local site drainage consists mainly of surface runoff and some infiltration. Roof drainage is captured internally by the building plumbing and outlets to the existing combined sewer system on Sussex Drive. Surface run-off for the remainder of the site is captured by a limited number of catchbasins (1 catchbasin in the forecourt and 1 catchbasin on Bruyere Laneway). There is a third catchbasin, located at the rear of the building that captures surface runoff from the parking area. Information on the condition, location, size and slope of on-site storm sewers was not available as part of the preparation of this report. Water servicing for the building is currently provided by a 200mm diameter water service which is connected to the 305 mm diameter watermain located on Sussex Drive. The only known fire hydrant, in close proximity to the site, is located at the rear of the building on the northeast corner of the National Gallery loading area. The fire hydrant and lateral would have to be protected during the redevelopment of the GCP site. It is understood that there are currently two sanitary service laterals for the existing building (i.e. one lateral to the original building and one lateral to the addition built in 1924). The sanitary service lateral to the original building is understood to connect to the Royal Canadian Mint sewer system, while the second sanitary lateral for the building addition is connected to the Sussex Drive combined sewer system. 4 PROPOSED DEVELOPMENT The proposed development consists of a full rehabilitation of the existing three-storey building. The building will be used for offices and the GCP community centre, pending rezoning to allow the office use. The community centre for the GCP will occupy a minimum of 1393 m 2 (15,000 ft 2 ) and the offices will occupy approximately 2787 m 2 (30,000 ft 2 ). Landscaping will be incorporated around the perimeter of the site as shown on the Architect s landscape drawing (not included in this report). Storm and sanitary flows inside the building will be separated as part of the complete rehabilitation of the plumbing system. New storm and sanitary servicing connections will be made to the new storm and sanitary sewers on Sussex Drive. The plumbing modifications will also have to include the abandonment of the sanitary service lateral connected to the Royal Canadian Mint sewer system.

5 Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page 3 The building will be serviced by a single 200mm diameter water service connected to the new watermain on Sussex Drive. The new stormwater management (SWM) system will be sized to attenuate the 100-year postdevelopment flow rate to the 5-year allowable release rate. 5 STORMWATER MANAGEMENT PLAN Drawings M-1 and M-2, in Appendix A, show the boundaries of the pre- and post-development drainage areas and should be read in conjunction with this report. The design approach for the stormwater management is to ensure that the post-development peak flows do not exceed the allowable release rate. As per City of Ottawa direction, the stormwater flows from the site will be controlled to the 5-year flow rate for a time of concentration of 20 minutes and a C factor of 0.50, with provision for stormwater storage for any storm events greater than the 5-year up to and including the 100-year design storm event. 5.1 PRE-DEVELOPMENT CONDITIONS As shown on Drawing M-1, in Appendix A, approximately 0.50 ha of the existing site drains uncontrolled to the Sussex Drive combined sewer system. While, 0.06 ha of the existing site, on the west side of the building, drains uncontrolled to an existing storm sewer system on Lady Grey Drive. As a result of discussions with the City of Ottawa, it was agreed that both drainage outlets noted above would remain under post-development conditions. For the pre-development conditions, the above noted areas have been used for SWM calculations purposes. The pre-development areas are summarized below. Table 1 Pre-Development Areas Surface Type Area (ha) Drainage to Sussex Building Area (C = 0.9) 0.15 Grassed Area (C = 0.2) 0.08 Hard Surface Area (C = 0.9) 0.27 Total Drainage to Sussex 0.50 Drainage to Lady Grey Drive Hard Surface Area (C = 0.9) 0.06 Total Drainage to Lady Grey Drive 0.06 The Rational Method formula has been used to calculate the pre-development stormwater runoff. The rainfall intensity is taken from the Intensity Duration Frequency (IDF) curve equations in the Ottawa Sewer Design Guidelines, October, The pre-development flow calculations are included in Appendix B. Q = 2.78 CiA, where: Q = Flow rate (L/s) C = Runoff coefficient i = Rainfall intensity (mm/hr) A = Area (ha) Rainfall intensity: 5-year Ottawa IDF curve i = / (t ) 0.814

6 Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page year Ottawa IDF curve i = / (t ) where: Runoff Coefficient C = 0.50 Time of concentration t = 20 min. 5-year IDF curve i = mm/hr, based on a 20-min. time of concentration 100-year IDF curve i = mm/hr, based on a 20-min. time of concentration Using the Rational Method formula and based on a 20 minute time of concentration and a runoff coefficient of 0.50, the 5-year pre-development flow rate for the Sussex Drive drainage area has been calculated to be 48.8 L/s. This will be used as the total allowable flow rate for post-development conditions. 5.2 POST-DEVELOPMENT CONDITIONS As discussed above, the Lady Grey Drive drainage area will continue to drain uncontrolled to the Lady Grey Drive storm sewer system. The remainder of the site, that will continue to drain to Sussex Drive, will be controlled to the predevelopment flow rate determined above, 48.8 L/s. The required storage volume to control the 100- year post-development flow rate was calculated using the modified Rational Method, as per Ottawa Sewer Design Guidelines, October The post-development storage volume calculation is included in Appendix B. For the post-development conditions, the Sussex Drive drainage areas have been used for SWM calculations purposes. The post-development areas, shown on Drawing M-2 in Appendix A, are summarized below. Table 2 Post-Development Areas Surface Type Area (ha) Drainage to Sussex Building Area (C = 0.9) 0.15 Grassed Area (C = 0.2) 0.08 Composite Area (C = 0.5) 0.02 Hard Surface Area (C = 0.9) 0.25 Total Drainage to Sussex 0.50 Based on the above noted table, the average runoff coefficient for the Sussex Drive drainage area is The modified rational method calculation indicates that, based on the allowable flow rate, the required storage to attenuate the 100-year post-development flow rate is equal to 96 m 3. The type of storage to be constructed will include a combination of surface and/or below grade (tank) storage which will be determined as part of the next stage of the project as the design is advanced. Roof storage is not recommended for this heritage building. As part of the combined sewer separation work on Sussex Drive, the roof drain leader that previously drained to the combined sewer on Sussex Drive, will be replaced with a new service to the new storm sewer manhole constructed on Bruyere Lane, as part of the Sussex Drive Reconstruction project.

7 6 SANITARY SEWER Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page PRE-DEVELOPMENT CONDITIONS As noted above, the existing building is currently serviced by two sanitary service laterals (i.e. one lateral is connected to the Royal Canadian Mint sewer system and the other to the Sussex Drive combined sewer). The sanitary service lateral that is connected to the Royal Canadian Mint sewer system will be abandoned. As part of the Sussex Drive Reconstruction project, the new sanitary sewer in Sussex Drive is presently being constructed with a new 200mm service lateral from the new sewer to a manhole just inside the property line at 330 Sussex Drive. This manhole intercepts the two existing 100mm services from the building (the sanitary service and the roof drain service). The following sanitary peak flow estimation has been completed on the basis that the postdevelopment sanitary and storm flows on-site will be fully separated. The existing building previously housed the War Museum, including support staff. Therefore, based on the Ottawa Sewer Design Guidelines, October 2012, the average flow of 50,000 L/gross ha/d for institutional flows is used, and peak flow is obtained by using a peaking factor of 1.5. An infiltration allowance of 0.28 L/s/gross ha is also applied. Based on these design guidelines, the following is the estimated peak sanitary flow: Q = 50,000 L/gross ha/d * 0.56 ha * L/s/gross ha * 0.56 ha Q = 42,000 L/d L/s Q = 0.5 L/s L/s = 0.66 L/s Therefore, the estimated pre-development peak sanitary flow for the existing building is 0.66 L/s. 6.2 POST-DEVELOPMENT CONDITIONS The proposed rehabilitation of the existing building will accommodate office space and the Global Centre for Pluralism, which will operate similar to a community centre with a library, a dialogue centre, meetings rooms, offices and a kitchen to warm food prepared off-site. This usage falls under the same estimated average flow value from the Ottawa Sewer Design Guidelines, October 2012, of 50,000 L/gross ha/d. Therefore, the estimated post-development peak sanitary flow is the same as the predevelopment peak sanitary flow of 0.66 L/s. A new sanitary service lateral will be installed as part of the building rehabilitation which will be connected to the new sanitary manhole at 330 Sussex Drive which was provided as part of the Sussex Drive Reconstruction project. Drawing M-3, in Appendix A, shows the proposed sanitary service layout. 7 WATERMAIN The study area is located in the City s 1W water pressure zone. This zone is fed directly by the Fleet Street Pumping Station, and the high lift pumping stations located at the City s two water treatment plants. The existing 305mm watermain on Sussex Drive is being replaced as part of the Sussex Drive Reconstruction project. The majority of the watermains on adjacent streets have recently been upgraded as part of the City s capital projects. Further to discussions with the mechanical engineering consultant, it is understood that the current plumbing system will be upgraded as part of the building rehabilitation. The existing 200mm service

8 Site Servicing & Stormwater Management Overview Update Report January 2014 Global Centre for Pluralism Page 6 lateral will be replaced. The service lateral will be connected to the new watermain on Sussex Drive as shown on Drawing M-3, in Appendix A. The fire flow demand was estimated using the Fire Underwriters Survey, Water Supply for Public Fire Protection. The building was classified as non-combustible construction with a non-combustible occupancy type, as is typical for usages such as office space. The minimum deduction allowable for buildings with sprinkler systems, 30%, was applied to the required fire flow demand. This deduction could be increased to as much as 50% dependent on the final sprinkler system design. An increase of 28% was then applied to account for the exposure distance to the adjacent buildings. The resultant fire demand is estimated to be 133 L/s, the calculations are shown in Appendix C. This is a conservative estimate and could potentially be refined during the detailed design stage as factors such as fire walls and details of the sprinkler system are finalized. 8 CONCLUSIONS AND RECOMMENDATIONS The on-site storm sewers and related storm structures to attenuate the 100-year post-development flow rates for the Sussex Drive drainage area to the allowable post-development flow of 48.8 L/s will be designed as part of the next stage of the project. Based on this allowable flow rate, the required storage to attenuate the 100-year post-development flow rate is equal to 96 m 3. For the drainage area connected to the Lady Grey Drive Storm Sewer system, it is understood that no stormwater storage will be required as part of the site redevelopment. However, it is possible that an MOE Environmental Compliance Approval will be required given that the existing storm sewer system on Lady Grey Drive services more than one property and that quality control measures may be required. A new storm service for the roof drain leader will be connected to the new storm sewer on Sussex Drive via the new manhole on Bruyere Lane. Water servicing for the site will be provided through a new 200mm water service connection to the new 305 mm watermain on Sussex Drive. The expected fire flow demand is estimated to be 133 L/s. The peak sanitary flow for the building, including infiltration, is calculated to be 0.66 L/s. A new sanitary service lateral will be connected to the new sanitary sewer on Sussex Drive to accommodate these flows. F:\ISO\ASP\EO2420\EOA\DOCS\Servicing and Stormwater Report Nov 2013\GCP site redevelopment - servicing and stormwater report update docx

9 APPENDIX A Drawings

13 APPENDIX B Stormwater Management Calculations

14 PRE-DEVELOPMENT FLOWS Pre-development Flow - to Sussex Drive Area (ha) = 0.50 C = 0.5 allowable C factor 5 year design storm Rainfall intensity (i) (mm/hr) = /(Tc+6.053)^0.814 Tc (min) = 20 i (mm/hr) = Q (allowable) (L/s) = 2.78CiA Q = 48.8 L/s F:\ISO\ASP\EO2420\EOA\DOCS\SWM Storage Requirements November 2013

15 STORAGE CALCULATIONS Required Storage - Flows to Sussex Drive Pre-development flow (5-year storm) 48.8 L/s Allowable post-development flow 48.8 L/s 100 year Storage Requirement Area (ha) Runoff Coefficient (C ) A (ha) = 0.50 Building Post C (avg) = 0.77 Landscaping Hard Surface Composite Q (L/s) = 2.78CiA T (min.) I (mm/hr) Q (L/s) Qallow.(L/s) Qstorage Storage (m 3 ) Storage required for 100 year design storm = 95.9 m 3 F:\ISO\ASP\EO2420\EOA\DOCS\SWM Storage Requirements November 2013

16 APPENDIX C Fire Flow Calculations

17 Global Centre for Pluralism Sussex Drive, Ottawa, ON - Fire Flow Calculations 21-Jan-14 Building Type of Construction Adjusted to the nearest 1000 (minimum 2000) Reduction / Increase due to Occupancy Required Fire Flow Adjusted to the nearest 1000 (minimum 2000) Total Footprint Area Fire Flow Occupancy Factor Fire Flow with Occupancy Sprinklers Factor Reduction due to Sprinklers Exposure Factor Increase due to Exposure Fire Flow with Exposure m2 L/min L/min L/min L/min L/min L/min L/min L/s C A F O S E 330 Sussex Drive - GCP ,379 11,000-25% -2,750 8,250-30% -2,475 28% 2,269 8,044 8, Reference: Water Supply for Public Fire Protection, 1999 by Fire Underwriters Survey C Type of Construction S Sprinklers Wood Frame 1.5 Assume 30% until mechanical design is complete proving fully supervised, Ordinary Construction (masonry and combustible floors) 1 whether or not there are fire walls, etc. Non-Combustible Construction (unprotected metal structure) 0.8 Steel/concrete with masonry E Exposure Fire resistive construction (< 2 hours) 0.7 Cumulative, maximum 75% Fire resistive construction (> 2 hours) 0.6 Distance (m) % A Total Floor Area % 4180 m % % % F Fire Flow East wall 59 m 0 % 220*C*(A^0.5) West wall 5 m 10 % 2,000<F<45,000 North wall 19 m 15 % South wall 35* m 2.5 % O Occupancy 27.5 % Non-Combustible -25 % Office space/theatre Limited Combustible -15 % Combustible 0% Free Burning 15 % Rapid Burning 25 % Commercial 0% *South wall - assumed half the distance of 69m to NAG since GCP is in line with the courtyard, not the closest part of the building Used half exposure for west and south walls since they don't meet the requirements for maximum percentage exposure Delcan/EO2420EOA

Appendix K. Stormwater Management Plan

Appendix K. Stormwater Management Plan Regional Municipality of Halton - Steeles Avenue (Regional Road 8) Class EA - Industrial Drive to Regional Road 25/Martin Street Appendix K Stormwater Management Plan PR226401.001 Rev. 2 PR.DOT, 00/01