LRT TRANSIT ORIENTED DEVELOPMENT STUDY AREAS SERVICING OVERVIEW Final Draft Report, December 2013
4.0 STORMWATER MANAGEMENT
4.1 EXISTING CONDITIONS
Figure 4-1 shows the overall study area with associated stormwater infrastructure.
In discussion with the City of Ottawa, no rehabilitation on the major sewers is planned within the next three years that would reduce trunk capacity.
Similarly to the sanitary servicing, the major divides in the study area for storm servicing are Highway 417 and St. Laurent Boulevard.
Overall, there are no major constraints on stormwater servicing in the study area. City staff have identified areas south of the Train study area to have shallow storm sewers and to be partially separated. Outlets to the Rideau River are influenced by the river’s water level however the zone of influence upstream in the sewer network has not yet been traced. There are few reports of flooding due to stormwater within the study area.
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Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Pipe Diameter (mm) Blair TOD Study Area 2. Imagery: City of Ottawa Transit Oriented 1050 - 1350 Hurdman TOD Study Area Development Lees TOD Study Area 1351 - 2175 Figure No. Cyrville TOD Study Area 2176 - 4500 4-1 St. Laurent TOD Study Area Title Train TOD Study Area Stormwater Trunk Infrastructure - Overall Study Area LRT TRANSIT ORIENTED DEVELOPMENT STUDY AREAS SERVICING OVERVIEW Final Draft Report, December 2013 STORMWATER MANAGEMENT
4.1.1 Lees TOD Study Area
This area covers approximately 81.6ha. The drainage area is split roughly by the Highway 417. Land use is predominantly residential, with institutional uses at the eastern TOD boundary and leisure and light industrial areas immediately north of the highway. Figure 4-2 presents the extents of the TOD area, and storm sewers in the region.
Figure 4-2: Existing Storm Sewers, Lees TOD Study Area
Sewers in the area south of the Highway are partially separated, whereas regions north of the Highway contain primarily combined sewers with some partially separated areas. City staff have identified that an EA was completed in regards to separation of sewers north of Highway 417, but was found not to be cost effective. The region maintains several outlets to the nearby Rideau River. No end-of-pipe quality controls have been noted for the region.
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4.1.2 Hurdman TOD Study Area
This area covers approximately 73.1ha. Drainage area land use is predominantly surface- drained greenspace, with commercial and residential uses at the east and south TOD boundary. Figure 4-3 presents the extents of the TOD area, and storm sewers in the region.
Figure 4-3: Existing Storm Sewers, Hurdman TOD Study Area
Sewers in the region generally drain northward to two major outfalls to the Rideau River. No end of pipe quality control has been reported for the region. Servicing in the area is constrained by the Rideau River’s water level. Although no capacity concerns have been identified by City staff, sanitary sewers in the area have potential to surcharge with impact to storm sewers in the region.
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4.1.3 Train TOD Study Area
This area covers about 100.9ha. The entire area discharges into the Rideau River via several different trunk sewers. Outlets to the Rideau River are influenced by the river’s water level. The area is considered as a partly separated sewer system. Figure 4-4 presents the extents and storm sewers.
Figure 4-4: Existing Storm Sewers, Train TOD Study Area
The study area is split by Highway 417. The area north of the Highway drains to the Rideau River via the Coventry Road storm sewer, which discharges just north of the RCMP facility. The pipes range in size from 2700 mm diameter at the outlet down to 1200 mm diameter at Belfast. East of Belfast, the sewer drains the St. Laurent Study Area as well as St. Laurent Boulevard
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north of Ogilvie. The study area north of the highway is mostly zoned Leisure and General Mixed Use.
Most of the area south of the Highway discharges to the Tremblay Road storm trunk sewer just to the south. The southern portion of the study area is zoned Transit, Mixed Use, and Industrial. The Tremblay Road sewer ranges in size within the study area from 1650 mm in the east to 1950 mm in the west. Upstream of the site area, the sewer drains the St. Laurent Study Area – the St. Laurent Shopping Centre north of the Highway and residential areas south of the Highway, as well as the Transitway eastward past the Cyrville study area. The Tremblay Oil Interceptor treats flows at the outlet.
A small portion in the southwest corner of the study area drains to a storm sewer that crosses Riverside Drive and runs northwest to the Rideau River, staying southwest of the existing Hurdman Transitway station. This sewer collects stormwater from the Industrial Avenue trunk sewer which begins just east of Russell Road. This trunk receives drainage from several residential communities south of Industrial, including areas near Coronation and Belena Parks. Several industrial areas also drain to the Industrial Avenue sewer. Within the study area, the sewer size is 1200 mm, which is the same size at the outlet to the Rideau River. The Alta Vista Oil Interceptor treats flows at the outlet.
4.1.4 St. Laurent TOD Study Area
This area covers about 120.5ha. The area is split roughly by St. Laurent Boulevard and Highway 417. Land use north of the Highway is zoned Mixed Use, south of the Highway and west of St. Laurent Boulevard it is Residential, Leisure and Light Industrial, and south of the Highway and east of St. Laurent Boulevard land use is Light Industrial. Figure 4-5 presents the extents and storm sewers.
Most of the area north of the Highway drains to the Coventry Road storm sewer described in the previous section. St. Laurent Boulevard north of Coventry Road (and a portion just south of it) drains to this sewer. Within this study area, this sewer ranges in size from 900 mm diameter on St. Laurent to 1350 mm diameter at Belfast.
The area south of the Highway discharges to the Tremblay Road storm trunk sewer described in the previous section. Just west of St. Laurent Boulevard flows to St. Laurent Boulevard, flows drain to St. Laurent Boulevard and join with the area southeast of St. Laurent Boulevard and the Highway, outletting to a surface channel.
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Figure 4-5: Existing Storm Sewers, St. Laurent TOD Study Area
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4.1.5 Cyrville TOD Study Area
This area covers about 99.7ha. The collection area is split by Highway #417 and the interchange with Highway #174. The area north of the Highway discharges to an open channel that runs eastward under the Aviation Parkway. The ditch outlets to the Cyrville Artificial Wetlands (CAW), a City-maintained facility (originally designed for the Canadian Mortgage and housing Corporation – CMHC). The outlet structure on this facility was recently refurbished as part of an agreement with a developer. Figure 4-6 presents the extents and storm sewers.
Figure 4-6: Existing Storm Sewers, Cyrville TOD Study Area
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The CAW discharges into the Cyrville Drain, which has Municipal Drain status under the Ontario Drainage Act. The Drain has two branches: the South Cyrville Drain, and the Cote’s-Martain Drain; see Figure 4-7 for details. Legal Municipal Drain status ends at the confluence of the two Drains, just northeast of the intersection of the Aviation Parkway and Highway 417. The Drains outlet to Cummings Creek, whose eponymous watershed measures 930 ha and outlets to Green’s Creek southeast of the intersection of Innes Road and Highway 417.
The area south of the Highway within the study area is industrial and is generally surface drained in ditches and channels, eventually outletting to the Cyrville Drain. Some storm sewers in the south drain southward to the South Cyrville Drain. City staff have identified that there may be cross-connections in this industrial area south of the highway. Most of the industrial buildings have slab-on-grade foundations with no basements.
Figure 4-7: Municipal Drains Near Cyrville Study Area
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4.1.6 Blair TOD Study Area
This area covers about 118.7ha. The drainage area is split into three zones. Figure 4-8 presents the extents of the TOD area, and storm sewers in the region.
Figure 4-8: Existing Storm Sewers, Blair TOD Study Area
Firstly, the area north of Highway 174 and east of Blair Road discharges to the Ogilvie Road storm sewer which runs eastward to a culvert crossing at Jasmine Crescent. City of Ottawa staff have indicated that there have been scattered reports of flooding identified in this region, and are likely due to surface drainage concerns. Secondly, the northwest quadrant (north of the highway, west of Blair) drains into the Ogilvie Road storm sewer which runs west and discharges into the Cyrville Artificial Wetlands or drains by local storm sewer to the Gloucester City Centre Dry Pond. Both facilities discharge to the Cyrville Drain. Thirdly, the area south of the highway is drained by local storm sewer and flows to the south and is collectively referred to as the Pineview area. City staff have identified that corrective infrastructure work has taken place in the Pineview area to respond to reports of flooding in residential areas to the south: sewers are separated, inlet control devices (ICDs) were recently installed, and minor work to
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correct overland flow routes was performed. Subsurface storage and a dry pond exist within the TD commercial site on Telesat Court, and are near capacity.
4.2 CAPACITY NEEDS AND ASSESSMENT
4.2.1 Capacity Needs
Storm sewers will need to continue to convey flow without surcharging basements and any foundations which are connected to it. This does not necessarily mean that the sewer system must flow freely under gravity flow, but simply that it will not be surcharged to the point that it floods basements.
Since the majority of the Lees, Hurdman, Train and St. Laurent areas discharge to the Rideau River, capacity of the receiving waterbody is not an issue due to the River’s relatively large size and conveyance capacity. For the portions of Cyrville and Blair that drain to the CAW however, the volume and conveyance capacity of the CAW must be assessed to ensure that it can contain the volume of water that will be delivered to it and that it can safely convey restricted outflows and overflows. Similarly, the Cyrville Drain and associated culverts must be assessed for their capacity to convey flow and the Drain’s ability to resist erosive forces due to potentially increased flow velocities.
4.2.2 Capacity Assessment
Although the outcome of the TODs will be to increase population density surrounding the proposed LRT stations, stormwater infrastructure is not directly impacted by population density but rather by the surface imperviousness that usually results from development. Increased imperviousness results in less infiltration and more runoff versus a pervious surface. Most of the land in the proposed TOD areas is already developed such that there is only a relatively small amount of greenspace remaining. However, the Hurdman station has a significant portion of undeveloped green space and the Lees station has several pocket green spaces. Therefore, the most significant impact for stormwater infrastructure in the TODs is expected in areas that are currently pervious (or ‘green’) that are slated for future development to an impervious area.
4.2.3 Proposed Imperviousness
On the following pages, Figures 4-9 through 4-14 present proposed future land use (as identified by City TOD planners) versus existing imperviousness for the subject study areas. Greenspace areas that could be significantly hardscaped are approximately circled in red.
It can be seen from the figures that, with the exception of the Hurdman station, the potential pervious area for development is much smaller relative to the existing impervious area that can be re-developed.
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Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-9
Title Comparison of Future Land Use (left) versus Existing Imperviousness, Lees TOD Study Area V:\01225\active\other_pc\163401180\GIS\MXD\Figure_Updates_18012013\163401180_Fig4-10_HurdmanLU.mxdRevised: 2013-11-06 By:ncruikshank November, 2013 Project No.: 163401180
Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-10
Title Comparison of Future Land Use (left) versus Existing Imperviousness, Hurdman TOD Study Area V:\01225\active\other_pc\163401180\GIS\MXD\Figure_Updates_18012013\163401180_Fig4-11_TrainLU.mxdRevised: 2013-11-06 By:ncruikshank November, 2013 Project No.: 163401180
Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-11
Title Comparison of Future Land Use (left) versus Existing Imperviousness, Train/Tremblay TOD Study Area V:\01225\active\other_pc\163401180\GIS\MXD\Figure_Updates_18012013\163401180_Fig4-12_StLaurentLU.mxdRevised: 2013-11-06 By:ncruikshank November, 2013 Project No.: 163401180
Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-12
Title Comparison of Future Land Use (left) versus Existing Imperviousness, St. Laurent TOD Study Area V:\01225\active\other_pc\163401180\GIS\MXD\Figure_Updates_18012013\163401180_Fig4-13_Cyrville.mxdRevised: 2013-11-06 By:ncruikshank November, 2013 Project No.: 163401180
Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-13
Title Comparison of Future Land Use (left) versus Existing Imperviousness, Cyrville TOD Study Area V:\01225\active\other_pc\163401180\GIS\MXD\Figure_Updates_18012013\163401180_Fig4-14_Blair.mxdRevised: 2013-11-06 By:ncruikshank November, 2013 Project No.: 163401180
Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa 2. Imagery: City of Ottawa, 2013 Transit Oriented Development
Figure No. 4-14
Title Comparison of Future Land Use (left) versus Existing Imperviousness, Blair TOD Study Area LRT TRANSIT ORIENTED DEVELOPMENT STUDY AREAS SERVICING OVERVIEW Final Draft Report, December 2013 STORMWATER MANAGEMENT
4.2.3.1 Storm Sewers Capacity Assessment
The 2009 City of Ottawa Infrastructure Master Plan (IMP) does not identify any major storm sewer or SWM upgrades necessary in the TOD areas through the 2031 time horizon due to background growth; the IMP however did not anticipate TOD-induced growth.
As can be seen in the preceding six figures that for most of the stations, compared with the overall TOD area, a relatively small amount of currently-undeveloped land will be hardscaped in future. Given the small percentage increase in runoff that would result, and due to the stormwater design requirements that will be imposed on all new developments in the area (see section 4.3.1.1 for details), the peak inflow to the sewer system is not expected to change significantly from current conditions. However, portions of the Hurdman station will undergo a significant increase in imperviousness and on-site controls will be required for these areas.
A portion of the Cyrville area south of Highway 417 is not serviced by storm sewers. This mostly industrial area has a rural road cross-section and surface drainage is achieved via ditches, with the exception of sewers on StarTop Road. Several previous studies have been prepared which examine the potential for sewers in this area, including a report by Kostuch Engineering Ltd. in April 1987, and the Cyrville Drainage and Infrastructure Plan prepared by McNeely Engineering and McNeely-Tunnock Ltd. in February 1997. The reports found that some deepening of the Cyrville Drain would be required in order to provide invert elevations that would be sufficiently low to drain typical residential foundations by gravity. These works were carried out on the South Cyrville Drain in the late 1990s, according to a 1997 Engineer’s Report by Robinson Consultants. In any of the TOD areas, any future developments that have basements lower than existing sewers will need to be sump pumped to the storm sewer.
Overall, the storm sewers in the study areas appear to have sufficient conveyance capacity to service the TODs.
4.2.3.2 Cyrville Artificial Wetlands Facility Capacity Assessment
The CAW facility was originally developed by the CMHC for existing and future developments east of the Aviation Parkway between Ogilvie and Montreal Roads, as well as future south of Ogilvie Road, west of the Aviation Parkway. The CAW is an on-line facility which provides quality control for a 10mm rainfall event (intended to capture the ‘first flush’ of runoff). The CAW receives runoff from 272 ha catchment of development.
Based on the presumed drainage areas and level of imperviousness, the required quality and quantity storage in the facility was calculated by Paul Wisner & Associates, as well as in reports by J.L. Richards & Associates. If the imperviousness in the study areas is increased beyond what was assumed in the original design reports, modifications to the pond will be required to maintain the current level of service. Although the Cyrville and Blair TOD areas represent only a small portion of the tributary area to the CAW, the combination of future background growth
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(through infill in non-TOD areas) and the increase in imperviousness in the Cyrville and Blair areas will necessitate upgrades to the CAW facility.
4.2.3.3 Cyrville Drain Capacity Assessment
Due to the higher peak flows that would be directed to the Cyrville Drain following storm sewer construction in the Cyrville industrial area, and potentially increased flows out of the CAW, some slope stability and soil reinforcement works will be required on the Cyrville Drain to prevent erosion of the channel. From a review of recent studies, current capacity in the drain and associated culverts appears sufficient to convey the proposed flows. Design requirements for all other Cyrville or Blair TOD area development are such that excess flows generated from the development must be controlled to existing rates. Therefore, no additional flows should be conveyed to the drain.
4.2.4 Opportunities and Constraints
4.2.4.1 Future Sewer Separation Program
City staff have advised that as part of the Wet Weather Infrastructure Management Plan that is being prepared, areas of partial sewer separation (i.e. those areas where roofs or foundations are directed to the sanitary or combined sewer) will be targeted for full separation – i.e. roofs and foundations will be redirected to the storm sewer in future. In many areas, the underside of existing foundations may be below the storm sewer, therefore it is expected that all future separations will make use of sump pumps to direct flows to the storm sewer.
4.2.4.2 Sewer Age
City staff have provided Stantec with GIS files for the storm sewers in the TOD areas. These files contain installation year information for some of the sewers after 1950. Figures 4-15 through 4-20 render the pipes by colour according to their age. Although the conditions of these sewers is not known, this sewer age information may be helpful in identifying which sewers have been in service the longest and which may be higher priority for inspections or maintenance in future.
The study area contains several stretches of older sewer infrastructure (as identified in previous figures); to assess its condition and need for maintenance (especially for those sewers whose age is unknown) it is recommended that flows be sporadically monitored under the City’s temporary flow monitoring program to ensure that ongoing capacity will be available in: the Tremblay Road trunk sewer in the Train & St. Laurent areas, the St. Laurent sewers south of Highway 417, and the Transitway sewers north of Highway 417 in the Cyrville area.
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Categories 0 - 1874 1875 - 1950 1951 - 1970 1971 - 1990 1991 - 2000 2001 - 2010 2011 - 2013 0 250 500 m
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Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Hurdman TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented 1050 - 1350 Lees TOD Study Area Development Train TOD Study Area 1351 - 2175 Figure No. 2176 - 4500 Possible Proposed Sewers 4-15
Title Storn Sewer Year of Installation Lees TOD Study Area 370000 ±
Categories 0 - 1874 1875 - 1950 5030000 5030000 1951 - 1970 1971 - 1990 1991 - 2000 2001 - 2010 2011 - 2013
0 250 500 m
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Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Hurdman TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented 1050 - 1350 Lees TOD Study Area Development Train TOD Study Area 1351 - 2175 Figure No. Possible Proposed Sewers 2176 - 4500 4-16
Title Storn Sewer Year of Installation Hurdman TOD Study Area 370000 372000 ±
Categories 0 - 1874 1875 - 1950 1951 - 1970 1971 - 1990 1991 - 2000 2001 - 2010 2011 - 2013
0 250 500 m
V:\01225\active\other_pc\163401180\GIS\MXD\Report_figures_17102013\163401180_Fig4-17_StormSewerYr_Train.mxdRevised: 2013-10-22 By: ncruikshank 1:9,187 370000 372000 October 2013 Project No.: 163401180
Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Hurdman TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented 1050 - 1350 Lees TOD Study Area Development St. Laurent TOD Study Area 1351 - 2175 Figure No. Train TOD Study Area 2176 - 4500 4-17 Possible Proposed Sewers Title Storn Sewer Year of Installation Train TOD Study Area 372000 ± 5032000 5032000
Categories Unknown 1875 - 1950 1951 - 1970 1971 - 1990 1991 - 2000 2001 - 2010 2011 - 2013
0 250 500 m
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Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Cyrville TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented 1050 - 1350 St. Laurent TOD Study Area Development Train TOD Study Area 1351 - 2175 Figure No. Possible Proposed Sewers 2176 - 4500 4-18 Findings and Restrictions Title Storn Sewer Year of Installation St. Laurent TOD Study Area 374000 ± 5032000 5032000
Categories Unknown 1875 - 1950 1951 - 1970 1971 - 1990 1991 - 2000 2001 - 2010 2011 - 2013
0 250 500 m
V:\01225\active\other_pc\163401180\GIS\MXD\Report_figures_17102013\163401180_Fig4-19_StormSewerYr_Cyrville.mxdRevised: 2013-10-22 By: ncruikshank 1:10,000 374000 October 2013 Project No.: 163401180
Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Blair TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented Development 1050 - 1350 Hurdman TOD Study Area
1351 - 2175 Cyrville TOD Study Area Figure No. St. Laurent TOD Study Area 2176 - 4500 4-19 Title Storm Sewer Year of Installation Cyrville TOD Study Area 374000 ±
Categories Unknown 1875 - 1950 1951 - 1970 1971 - 1990 1991 - 2000 0 250 500 2001 - 2010 m 5032000 5032000
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Legend Notes Client/Project 1. Coordinate System: NAD 1983 MTM 9 City of Ottawa Existing Pipe Diameter (mm) Blair TOD Study Area 2. Airphoto: First Base Solutions, 2008 Transit Oriented 1050 - 1350 Cyrville TOD Study Area Development
1351 - 2175 Figure No. 2176 - 4500 4-20
Title Storm Sewer Year of Installation Blair TOD Study Area LRT TRANSIT ORIENTED DEVELOPMENT STUDY AREAS SERVICING OVERVIEW Final Draft Report, December 2013 STORMWATER MANAGEMENT
4.2.4.3 Overland Flow Route
City staff have also provided Stantec with a digital elevation model of the study area; see Figures 4-21 to 4-23. Using this data, we have identified several areas that may not have an overland flow outlet. This data is very coarse, however it is hoped that these areas can be flagged for further investigation.
4.2.4.4 Quality Control
Through infill development, the City has an opportunity to ask developers to improve water quality of discharge effluent. The use of on-site hydrodynamic separators to reduce suspended solids concentrations and oil and grease concentrations prior to discharge to the public trunk sewer is a common practice in the industry when water quality control is required.
Alternatively, the City could examine the option of upgrading its end-of-pipe facilities to perform better. There are oil interceptors on the storm sewer outfalls to the Rideau River which remove floatable oil. These interceptors could be retrofitted to have a larger oil storage capacity, or to have an off-line suspended solids separator which would only operate during low flows or during the ‘first-flush’ event. The Cyrville Artificial Wetlands already removes a significant amount of suspended solids, however the City may want to consider an oil interceptor to prevent spills into the facility.
4.2.4.5 Municipal Drains & Fish Habitat
The South Cyrville Municipal Drain was classified recently in 2005 as a Class ‘C’ drain by the Ministry of Natural Resources (MNR), as was the Cote’s-Martain Drain. This classification pertains to the condition of the drain, allowable maintenance works, and the level of fish habitat according to the Department of Fisheries and Oceans (DFO).
Class ‘C’ Drains have permanent flow (i.e. they are not intermittent or ephemeral streams), have a ‘warm’ temperature classification, and do not contain sensitive species and/or communities (e.g. those fish species identified in the Species at Risk Act). Previous reports have conducted fisheries surveys (Paul Wisner & Associate, 1991) and have confirmed that Cyrville Drain is warm water fish habitat, although only minnows were collected.
Typical Class ‘C’ Drain maintenance activities include brushing of the side slopes of the channel, clean-out of the Drain bed (bottom), and full clean-out. Timing restrictions exist for Drain work/maintenance in order to protect fish during critical life stages) and in-water work can only be performed when flows are not elevated. Sediment and erosion control measures are required for all work.
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Figure 4-21: Colour-Rendered Elevation Mapping of Lees and Hurdman TOD Study Areas (dark green for low areas, light green for higher areas)
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Figure 4-22: Colour-Rendered Elevation Mapping of TOD Areas (blue/green for low areas, yellow/red for higher areas)
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Figure 4-23: Colour-Rendered Elevation Mapping of Blair TOD Study Areas (dark green for low areas, light green for higher areas)
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4.3 SERVICING STRATEGIES
4.3.1 Servicing Strategies
The current storm sewer trunk infrastructure in the Lees, Train and St. Laurent TOD study areas appears sufficient to convey existing and proposed flows. The increase in surface imperviousness will be relatively small, and all future developments will be required to reduce their peak flow according to City of Ottawa design criteria. It is therefore expected that the trunk infrastructure can continue servicing these areas as long as there are not significant increases in upstream tributary areas and/or imperviousness (i.e. non-TOD lands that are nonetheless tributary to the storm sewers). If significant infill background growth occurs in these areas, the trunk infrastructure should be re-examined.
The sewers in the Cyrville TOD Study Area are similarly expected to perform in future comparably to current conditions. A new storm sewer will be required in the Cyrville Industrial area to replace the existing ditches, and assessments of the capacity of the Cyrville Artificial Wetlands and the erosion potential in the Cyrville Drain would also be required for future servicing.
The sewers in the Blair TOD Study Area are also expected to have sufficient conveyance capacity in the future. It is noted however that this analysis assumes that recommendations from the City of Ottawa study on the Pineview storm trunk were implemented and 75mm ICDs were installed on all public and private catchbasins. A major system assessment was recommended and it is assumed that all required measures have been implemented to assure safe drainage of surface flows. Any increase in imperviousness to Blair TOD areas tributary to the Pineview sewer will require on-site controls.
The Hurdman TOD Study Area has a significant area of currently undeveloped land. Consequently, the future development of these lands will significantly increase the overall imperviousness of the area. Existing developed areas are serviced by storm sewers which have sufficient capacity to continue to provide a 5-year level of service to these areas at the estimated increased imperviousness. However, on-site controls are proposed for all future developments to allow presently undeveloped lands to be serviced through the existing storm sewer trunk infrastructure.
4.3.1.1 Guidelines for Future Development
Future development of site plan and subdivision blocks in the TODs area will need to conform to existing stormwater management (SWM) criteria as laid out in several City documents:
City of Ottawa Sewer Design Guidelines, City of Ottawa, November 2004 City of Ottawa Sewer Design Guidelines Revised Section 8 – Stormwater Management, City of Ottawa, September 19, 2008
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Technical Bulletin ISD-2010-1, City of Ottawa, September 28, 2010 Technical Bulletin ISDTB-2012-1, City of Ottawa, January 31, 2012 Technical Bulletin ISDTB-2012-4, City of Ottawa, June 20, 2012 In addition to the standard SWM requirements, infill developments in the City are typically given the criteria that:
the 100 year post-development flow rate must be restricted to meet the pre- development flows from the 2 or 5 year storm (based on existing level-of-service), at a runoff coefficient of C=0.5.
the volume generated from restricting the post-development condition must be contained on-site (i.e. no overland spilling of major flows off-site)
At the time-of-writing of this report, the City has developed a document entitled “Urban Design Guidelines for Low-Rise Infill Housing”. The guidelines place additional restrictions on infill developments, mostly regarding requirements for ‘soft’ landscaping which may impact SWM. However, since new low density residential is not to be part of the TOD areas in the future, the guidelines will not be used for future TOD development approvals.
4.3.1.2 Lees TOD Study Area Requirements
Existing infrastructure is of sufficient capacity to convey 5 year future development flows with minor restrictions in areas. Recommended sewer inlet restrictions are summarized in Figure 4-24.
o Trunk sewer discharging at the south east boarder of the area has 2 year level of service future development flows to the sewer should be restricted to the 2 year rate. o drainage areas at the west corner of the site draining to the 1050mm sewer running north to the combined sewer should be controlled to the 5year rate at C=0.5 to prevent sewer surcharging.
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Figure 4-24: Proposed Ultimate Lees TOD Stormwater Restrictions
4.3.1.3 Hurdman Station Requirements
The Hurdman TOD Study Area has a significant area of currently undeveloped land. Consequently, the future development of these lands will significantly increase the overall imperviousness of the area. Existing developed areas are serviced by storm sewers which have sufficient capacity to continue to provide a 5-year level of service to these areas at the estimated increased imperviousness. However, on-site controls are proposed for all future developments to allow presently undeveloped lands to be serviced through the existing storm sewer trunk infrastructure. Figure 4-25 indicates the proposed controls for future development within the Hurdman TOD Study Area. However, development conditions may require the installation of new infrastructure within the currently undeveloped area.
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Figure 4-25: Proposed Ultimate Hurdman TOD Stormwater Restrictions
4.3.2 Recommended Servicing and Costing (Ultimate Conditions)
The following sections summarize recommended improvements or additional assessment requirements for the Hurdman, Cyrville and Blair areas. No recommendations are provided for the Lees, Train, and St. Laurent areas.
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4.3.2.1 Hurdman TOD Study Area Recommended Improvements
Presently, a sewer draining areas east of Riverside Drive outlets to a ditch just south of the existing Transitway and is conveyed under the transitway to the undeveloped area to the north. Development of the lands to the north of the transitway will potentially block the drainage from the south. It is therefore proposed to connect the sewer draining from the east side of Riverside Drive to the nearby existing 750mm sewer.
If development conditions require the installation of new sewers within the undeveloped portion of the TOD area then additional costs would be incurred. A possible sewer configuration was assessed and Sewer capital cost construction estimates were made using values from "City of Ottawa Development Charges Study - Volume I, FINAL, Rev. Jan.2010", by Stantec Consulting Ltd., prepared for City of Ottawa Infrastructures Services and Community Sustainability Departments, Development Review Services.
Brownfield sanitary sewer unit costs were used for pipes smaller than 1650mm in diameter since development charges in the above-noted study did not apply for storm sewers smaller than 1650 mm. Although completed in 2010, the report uses 2008 dollars, which have been updated to 2013 dollars using 3% annual inflation.
For budgeting purposes, engineering fees (20%), contingencies (10-20%), City costs (10%), and HST (13%) were included in the cost estimate. Table 4-1 below presents the estimated lengths, diameters, and costs of the proposed sewers in the Hurdman TOD area.
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Table 4-1: Cost Estimate, Proposed Sewers in Hurdman Area
Total Cost (000s), 2013 Diameter Total Unit Cost (000s Total Cost (000s), Dollars, (mm) Length (m) $/m) 2008 Dollars assuming 3% annual inflation
900 150 $2.49 $373.65 $433.16 975 215 $2.80 $601.66 $697.49 1050 135 $3.16 $425.95 $493.80 1200 75 $3.69 $276.39 $320.41 1500 135 $4.74 $640.72 $742.77 1650 425 $2.77 $1,176.62 $1,364.02 2100 190 $4.12 $782.34 $906.94
headwalls at river 3 $40.00 $120.00 HST (13%) $660.22 Total Costs with HST (000s $): $5,738.81 Engineering and City soft costs (30%) $1,721.64
Sub-Total (000s $) $7,460.45
40% Contingency $2,984.18
Total TOD Costs (000s $): $10,444.64
4.3.2.2 Cyrville TOD Study Area Recommended Improvements
Under ultimate build-out conditions, three improvements are proposed that are associated with the Cyrville TOD area; no improvements are proposed for the St. Laurent and Train areas (see Figure 4-26):
1. Potential enlargement of existing Cyrville Artificial Wetlands (existing SWM pond)
2. Potential erosion control works on the Cyrville Drain
3. New storm sewer in Cyrville Industrial Area
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Figure 4-26: Proposed Ultimate TOD Stormwater System Improvements
Sewer capital cost construction estimates were completed using the same costing assumptions as applied to the Hurdman sewers. Table 4-2 below presents the estimated lengths, diameters, and costs of the proposed sewers in the Cyrville TOD area.
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Table 4-2: Cost Estimate, Proposed Sewers in Cyrville Area
Total Cost (000s), 2013 Length Diameter Unit Cost Total Cost (000s), Dollars, Street Name (m) (mm) (000s $/m) 2008 Dollars assuming 3% annual inflation
Labrie Ave. 270 600 $1.46 $394.93 $457.83 Cyrville Rd. West of StarTop 460 1350 $4.19 $1,927.55 $2,234.56
Cyrville Rd. East of StarTop 250 975 $2.80 $699.61 $811.04
StarTop Rd., within TOD 150 1350 $4.19 $628.55 $728.66 StarTop Rd., outside of TOD 330 1500 $4.74 $1,562.96 $1,811.90
HST (13%) $785.72
Total Costs with HST (000s $): $6,829.71 Engineering and City soft costs (30%) $2,048.91
Sub-Total (000s $) $14,922.61
40% Contingency $5,969.05
Total Costs (000s $): $20,891.66
Cost TOD Area Only (000s $): $8,703.72
Based on recent experience with pond retrofits and erosion protection, it is estimated that the cost for the CAW and the Cyrville Drain will be $1.85M and $2.06M respectively. Adding the engineering fees, HST, City costs and contingency markup to these totals brings the figures to $3.81M and $4.24M. Note that retrofits and erosion protection may also be required due to development of the Blair TOD area and therefore the costs would be shared for the two TOD areas.
Table 4-3 presents the proposed improvement costs associated with the Cyrville TOD area, including the budgetary cost with applicable markups.
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Table 4-3: Stormwater Improvement Costs Associated with Cyrville TOD Area
Cost, 2013 Blair TOD Cyrville # Improvement Description Dollars share TOD share (millions$)
Potential enlargement of existing Cyrville 1 Artificial Wetlands (existing SWM pond) – $1.85 $0.96 $0.89 Shared with Blair TOD Potential erosion control works on the 2 $2.06 $1.03 $1.03 Cyrville Drain - Shared with Blair TOD New storm sewer in Cyrville Industrial 3 $8.70 N/A $8.70 Area (TOD area only) HST (13%) $1.64 $0.26 $1.38 Total Costs with HST (000s $): $14.26 $2.25 $12.00 Engineering and City soft costs (30%) $4.28 $0.68 $3.60 Sub-Total (millions $) $18.54 $2.93 $15.61 40% Contingency $7.41 $1.17 $6.24 Total Costs (millions $): $25.95 $4.10 $21.85
Local storm sewer improvements may be necessary as development proceeds, however it is anticipated that these costs will be financed by the developer, e.g. decommissioning of previous site infrastructure and replacement with new infrastructure to service a new proposed subdivision or site plan. If significant infill background growth occurs in areas that are tributary to the trunk sewers, but that are not TOD areas, the capacity of the trunk infrastructure should be re-examined.
4.3.3 Recommended Servicing and Costing (20 Year)
Servicing requirements for the 20 year horizon are dependent on the location of development. Development in the Lees, Train, St. Laurent and Blair TOD areas can proceed without any additional improvements for stormwater infrastructure. It is recommended that flows in older sewers be sporadically monitored under the City’s temporary flow monitoring program to ensure that ongoing capacity will be available within the Tremblay Road trunk sewers in the Train & St. Laurent areas, the St. Laurent sewers south of Highway 417, and the Transitway sewers north of Highway 417 in the Cyrville area.
Construction of the storm sewer in the Cyrville Industrial area would be required prior to development in that area; a detailed erosion assessment of the Cyrville Drain would also be required.
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If development were to occur in areas tributary to the CAW facility, a detailed assessment of the CAW should be performed to check quantity and quality storage requirements for future background growth in all tributary areas, as well as the impact of the proposed TOD intensification plans. The detailed erosion assessment of the Cyrville Drain would also be required.
Development within the Hurdman TOD area would require the installation of new storm sewers in the currently undeveloped area in order to provide a 5-year level of service to all areas of the TOD.
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