11. 24 JULY, 2009 west end flooding action plan – status update |
COMMITTEE RECOMMENDATIONS
That Council receive this report for information, and approve:
1. That Environmental Services staff be instructed to:
a) Prepare a policy on debris in creeks, drainage ditches and other drainage courses to balance water quality and water flow concerns; and
b) Co-ordinate efforts of staff in other departments and branches, as well as external agencies, to keep creeks, drainage ditches and other drainage courses free of unnecessary debris; and
c) Report back to Planning and Environment Committee on what has been put in place.
2. That Environmental Services launch a public awareness campaign on drainage issues including the role that surface accumulation of water during heavy rainfall events, the need to not remove manhole covers when water accumulates on the surface and what level of debris is acceptable or even helpful.
RECOMMANDATIONS DU COMITÉ
Que le Conseil reçoit ce rapport pour information, et approuve:
1. de donner instruction au personnel des Services environnementaux :
a) De rédiger une politique sur la présence de débris dans les ruisseaux, les fossés de drainage et les autres voies d’écoulement d’eau afin d’assurer un équilibre entre les préoccupations liées à la qualité de l’eau et celles se rapportant au débit d’eau;
b) De coordonner les efforts du personnel des autres services et directions ainsi que des organismes externes, afin que les ruisseaux, les fossés de drainage et les autres voies d’écoulement d’eau demeurent libres de débris inutiles;
c) De faire rapport au Comité de l’urbanisme et de l’environnement sur les mesures qui auront été mises en œuvre.
2. que les Services environnementaux lanceront une campagne de sensibilisation de la population sur les questions de drainage, notamment sur le rôle que joue l’accumulation d’eau à la surface du sol lors de fortes pluies, sur la nécessité de ne pas retirer les plaques d’égouts lorsque l’eau s’accumule à la surface du sol et sur le niveau de débris qui est acceptable, voire utile.
DOCUMENTATION
1. Deputy City Manager’s Report, Infrastructure Services and Community Sustainability dated 8 November 2010 (ACS2010-ICS-INF-0011).
2. Extract of PEC minutes dated 16 November 2010 (Issued separately)
Planning and Environment Committee
Comité de l'urbanisme et de l'environnement
and Council / et au Conseil
8 November 2010 / le 8 novembre 2010
Submitted by/Soumis par : Nancy Schepers, Deputy City Manager/Directrice municipale adjointe, Infrastructure Services and Community Sustainability/Services d 'infrastructure et Viabilité des collectivités
Contact Person/Personne ressource : Wayne Newell, General Manager/Directeur général, Infrastructure Services/Services des infrastructures
(613) 580-2424 x16002, Wayne.Newell@ottawa.ca
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Ref N°: ACS2010-ISC-INF-0011 |
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OBJET : |
PLAN D’ACTION POUR LES INONDATIONS DU 24 JUILLET 2009 DANS LA PARTIE OUEST DE LA VILLE – RAPPORT DE SITUATION |
That the Planning and Environment Committee and Council receive this report for information.
Que le Comité de l’urbanisme et de l’environnement et le Conseil reçoivent le présent rapport pour information.
EXECUTIVE SUMMARY
Following flooding in the City’s west end on 24 July 2009, Council directed City staff to identify causes of the flooding and to implement solutions to lower the risk of future flooding. This report provides an update on progress towards fulfilling this Council direction.
Staff are well on the way to completing this task. Causes of the flooding have been identified, some of the solutions are being implemented, and staff are in the final stages of solidifying several key aspects of an Action Plan to lower the risk of flooding in the areas.
The project is on schedule and, pending Council approval of the 2011 Draft Capital Budget, works on large-scale projects are will start in the spring of 2011.
Assumptions and Analysis:
A comprehensive investigation was undertaken to confirm the cause of flooding and identify solutions to reduce the risk of future flooding occurrences in the City’s westend. The investigation is subject to a Peer Review, which is ongoing, and results of this review will be available when the Action Plan is submitted to Council for approval in Q1 of 2011.
The following represents the key elements of the Action Plan, which will be finalized after completion of the Glen Cairn Environmental Assessment (EA) and the Peer Review.
Initiatives completed to date:
- Improvements made to the City’s emergency response procedures;
- Residential Protective Plumbing Program amended to enhance eligibility criteria;
- Sewer system connection requirements in new developments modified to reduce the risk of increased flows in existing sewer systems until all protective measures have been installed;
- Sewer Design Guidelines amended to include the requirement for BWVs for sanitary sewer laterals for all new residential construction;
- Stormwater inflow sources to the sanitary sewer identified and being eliminated;
- Solutions identified for all affected areas;
- Contract for sewer cover replacement and installation of inlet control devices (ICDs) awarded and implementation is underway; and
- Environmental Services Department organizational changes to provide more focus on surface drainage issues, including resident concerns related to debris along creeks.
In the short term (2010/2011):
- Finalize Glen Cairn EA for filing early in 2011;
- Finalize Peer Review;
- Continue with sewer cover replacement and installation of ICDs;
- Continue to eliminate stormwater inflow sources to the sanitary sewer system;
- Proceed to detailed design for more complex initiatives, such as Hazeldean Pumping Station upgrades, surface storage in Glen Cairn, modifications to the Glen Cairn pond and installation of new sanitary sewer in the Leacock area;
- Review storm drainage system (Kanata North) for additional enhancements to level of protection; and
- Continue to provide information to residents on ways to reduce their risk of flooding.
In the long term (2012 and beyond):
- Construction of more complex flood protection initiatives contained in the Action Plan
Legal/Risk Management Implications
There are no legal/risk management impediments to implementing the recommendation in this report.
Financial Implications:
Financial implications for all of the recommended solutions are being finalized and will be provided as part of the Action Plan to be tabled in Q1 of 2011, after completion of the Peer Review. The financial requirements will also be identified in the 2011 Draft Capital Budget.
Extensive public consultation has occurred as part of the overall flooding investigation process. A total of 12 Public Meetings have taken place since the July 24, 2009 flooding event.
In addition, a Public Advisory Committee (PAC) was established for the Kanata South area. This committee has been engaged throughout the investigation and was instrumental in providing information related to the flooding on 24 July 2009. The committee also helped to ensure the information presented to the public during consultations was communicated in a meaningful way.
Further public consultation will take place when the Glen Cairn EA report is filed for the 30-day public review. This is expected to take place in early 2011.
SOMMAIRE EXÉCUTIF
À la suite des inondations survenues le 24 juillet 2009 dans la partie ouest de la Ville, le Conseil a demandé aux employés de la Ville de cerner les causes des inondations et de mettre en œuvre des solutions pour réduire les risques d’inondations semblables à l’avenir. Le présent rapport souligne les progrès accomplis dans l’application de cette directive du Conseil.
Le personnel terminera très bientôt cette tâche. Les causes des inondations ont été cernées, certaines des solutions sont actuellement mises en œuvre et le personnel peaufine plusieurs aspects importants d’un plan d’action pour réduire les risques d’inondation dans le secteur visé.
Les échéanciers du projet sont respectés et des travaux de grande envergure devraient débuter au printemps 2011, sous réserve de l’approbation du Conseil.
Hypothèses et analyse
Une enquête détaillée a été menée afin de confirmer les causes des inondations et de trouver des solutions pour réduire les risques d’inondation dans la partie ouest de la ville. Un examen de l’enquête par les pairs est en cours et ses résultats seront dévoilés lorsque le plan d’action sera soumis à l’approbation du Conseil au cours du premier trimestre de 2011.
Ce qui suit constitue les principaux éléments du plan d’action, qui sera complété après l’achèvement de l’évaluation environnementale (EE) de Glen Cairn et l’examen par les pairs :
Initiatives complétées à ce jour :
- Améliorer les procédures d’intervention d’urgence de la Ville.
- Modifier le programme d’installation de dispositifs protecteurs sanitaires résidentiels afin de resserrer les critères d’admissibilité.
- Modifier les exigences en ce qui concerne le branchement d’égouts des nouvelles constructions pour réduire le risque d’augmentation du débit d’eau dans les systèmes d’égouts existants jusqu’à ce que toutes les mesures de protection soient installées.
- Apporter des changements aux lignes directrices en matière de conception des réseaux d’égout afin d’y inclure une exigence relative aux clapets anti-refoulement des branchements de l’égout séparatif pour toutes les nouvelles constructions résidentielles.
- Trouver des solutions pour tous les secteurs concernés.
- Attribuer un contrat de remplacement de plaques d’égout et d’installation de dispositifs de contrôle du débit dont la mise en œuvre est en cours.
- La direction des Services environnementaux a entrepris récemment des changements organisationnels pour fournir une attention plus spécifique aux inquiétudes reliées au drainage en surface.
À court terme (2010 / 2011) :
- Terminer l’EE de Glen Cairn afin de la soumettre au début de 2011.
- Terminer l’examen par les pairs.
- Poursuivre le remplacement des plaques d’égout et l’installation de dispositifs de contrôle du débit.
- Procéder à la conception détaillée d’initiatives plus complexes, comme des améliorations à la station de pompage de Hazeldean, le stockage en surface à Glen Cairn, des modifications à l’étang de Glen Cairn et l’installation d’un nouvel égout séparatif dans le secteur de Leacock.
- Examiner le réseau d’égouts pluviaux de Kanata-Nord pour continuer d’améliorer le niveau de protection.
- Continuer de fournir aux résidents de l’information sur les moyens de réduire les risques d’inondation.
À long terme (2012 et plus tard) :
- Mise en œuvre des initiatives plus complexes, contenues dans le plan d’action, pour la protection contre les inondations.
Répercussions sur le plan juridique et de la gestion des risques
Il n’existe aucun obstacle juridique ou lié à la gestion du risque concernant la mise en œuvre de la recommandation formulée dans le présent rapport.
Répercussions financières
Les répercussions financières de toutes les solutions proposées sont mises à jour et seront incluses dans le plan d’action qui sera déposé au cours du premier trimestre de 2011, une fois l’examen par les pairs complété. Les exigences financières seront également présentées dans le budget des immobilisations provisoire de 2011, sous réserve de l’approbation du plan d’action.
De vastes consultations publiques ont été organisées dans le cadre du processus général d’enquête. Au total, 12 réunions publiques ont eu lieu depuis les inondations du 24 juillet 2009.
De plus, un comité consultatif public a été formé pour le quartier Kanata-Sud. Ce comité, qui a participé à toutes les étapes de l’enquête, a grandement contribué à la collecte de renseignements concernant les inondations du 24 juillet 2009 tout en s’assurant que lors des consultations, ces renseignements étaient présentés à la population de façon à ce qu’elle puisse les utiliser.
Il y aura d’autres consultations publiques après le dépôt du rapport de l’évaluation environnementale de Glen Cairn pour la période d’examen de 30 jours, soit au début de 2011.
On 24 July 2009, parts of the City of Ottawa experienced a significant rainstorm (over 100 mm of rain in a 24-hour period in some areas) resulting in nearly 1,500 flooded basements and sewer backups, overflows at two sewage pumping stations and seven culvert failures. These occurred primarily in the City’s west end, mainly in Ward 4 - Kanata North (Beaverbrook), Ward 5 - West Carleton-March (Carp Village), Ward 6 - Stittsville, and Ward 23 - Kanata South (Katimavik and Glen Cairn). An investigation, led by the Infrastructure Services Department (ISD) and supported by several City departments, was initiated to understand why flooding occurred, what can be done to reduce the risk of future occurrences and to implement solutions.
The investigation is being carried out in five phases: Phase 1 - Background data collection; Phase 2 - Assessment and problem definition; Phase 3 - Identification and evaluation of alternative solutions; Phase 4 - Development and approval of action plan; and Phase 5 - Implementation of approved action plan. The scope of the investigation included all west end locations that experienced flooding. The focus was on affected areas where flooding resulted in damage to private properties or to City infrastructure. While heavy rainfall and flooding also occurred in other parts of the City, flooding in other areas appears to be isolated and dispersed. These isolated cases are subject to a separate investigation on an individual basis.
On 2 September 2009, staff provided Council with a verbal update on the flood investigation. In recognition that it was only about five weeks after the flooding, the update was limited to staff’s preliminary determination of the causes, flooding statistics including historical occurrences and follow up mitigation measures, design standards, statistics of the 24 July 2009 rainfall event, the work plan for the flood investigation and the peer review process being led by the City Manager’s Office.
On 22 January 2010, staff provided a memo to the Mayor and Members of Council with a copy of the Phases 1 and 2 Summary Report. This report provided a summary of the background information collected and reviewed for the affected areas, including the evolution of design standards, the main cause of basement flooding and sewer backups, and the focus for Phase 3 – identification of solutions to reduce the risk of future flooding occurrences. The memo also included preliminary cost estimates for consideration as part of the 2010 capital budget with the understanding that final estimates would be refined as part of Phase 3.
The purpose of this report is to provide a status update on the flooding investigation and development of the Action Plan. Solutions have been identified, but the intent is to present the Action Plan in Q1 of 2011 after the EA for Glen Cairn has been completed and the results of the Peer Review are available. To ensure there are no delays for the implementation, the 2011 Draft Capital Budget will include funding provisions to allow continued implementation of the Action Plan.
Flood Investigation Process
A comprehensive investigation was undertaken to confirm the cause of flooding and identify solutions to reduce the risk of future flooding occurrences. This was undertaken using a combination of staff and engineering consultant resources. The investigation included public input, field assessments, detailed topographical surveys, fog testing of sanitary sewer systems to confirm the presence of cross-connections or undesired infiltration sources, basement elevation surveys and camera inspections of the sewer system at selected locations. For all areas, the investigation focused on the evaluation of conceptual technical solutions using detailed hydraulic models (adjusted to recreate the 24 July 2009 conditions) that were developed for the affected areas. These models where used to confirm modes of flooding and assess various alternative solutions to select a preferred approach. As outlined later in this report, public consultation with affected residents was undertaken throughout the investigation process to seek input, and to keep residents abreast of the process and the anticipated solutions.
Given the extent of flooding and complexities involved in the Glen Cairn area, the investigation followed the Class EA process. Through this comprehensive process, a number of alternative solutions were evaluated and preferred solutions identified. This information was presented at a public meeting on 15 September 2010, including solutions designed to: improve overland drainage, reduce the inflow of stormwater into the sanitary sewer system, prevent storm sewers from surcharging, reduce the water level in the Glen Cairn pond during large rainfall events, and increase the level of protection at the Hazeldean pumping station. The EA report is scheduled to be completed by the end of 2010 and filed for 30-day public comment period in early 2011. In addition, the evaluation was subject to a Value Engineering process, comprised of recognized experts in the field undertaking an independent assessment of the alternative solutions. This process has helped to reinforce the selection of the preferred technical solutions. A PAC was also established at the outset by the Ward Councillor for Kanata South. This PAC was engaged throughout the process and was instrumental in providing information related to the flooding event and ensured information presented to the public was communicated in a meaningful way.
The investigation is also subject to a Peer Review being coordinated by the City Manager and Deputy City Manager, Infrastructure Services and Community Sustainability (ISCS). That review is ongoing and results will be available when the Action Plan is submitted in Q1 of 2011.
Level of Service Objective
The west-end communities that experienced flooding and sewer backups are serviced by separated storm and sanitary sewer systems, with a few locations serviced by roadside ditches. The City's stormwater and sanitary sewer systems convey flows generated from wastewater discharges and wet weather influences and were designed and built in accordance with recognized standards that evolved over time. "Stormwater" means wet weather runoff that is collected from roads, parks, rooftops, private property and building footing drains. "Sanitary sewage" means wastewater that comes from toilets, showers, floor drains, sinks and other plumbing fixtures.
Since the mid to late 1980’s, there have been significant changes in the way communities in Ottawa are designed to handle stormwater by introducing the concept of minor and major storm drainage systems. Minor systems refer to the storm sewers that are sized and controlled to convey frequent storm events (i.e. rainfall events with a return frequency less than 5 years). Major systems refer to the grading of roads and the provision of stormwater retention facilities that are sized to handle larger less frequent storm events (i.e. rainfall events with a return frequency up to 100 years, including ability to handle historical major storm events). Communities built prior to the mid to late 1980’s include provisions for the minor system (i.e. storm sewers) only. Provisions for the major system only gradually occurred after this date.
The provision of major system considerations in the design of new communities has resulted in a significant increase in the level of protection against property flooding from large and infrequent rainfall events. It has made these communities more resilient to these events and impacts associated with climate change. For example, this resiliency has been demonstrated with the limited property flooding that was experienced in new neighbourhoods of Orléans (significant rainfall events that occurred in 1998 and 2006) and Kanata (2009). The key is that even though rainfall levels were significant, flows in these newer communities were controlled and channelled away from private properties. The challenge is to emulate this level of resiliency in existing communities given the constraints associated with the existing conditions (i.e. topography, depressed driveways, road and lot layouts, etc).
For existing west-end communities, the current levels of service are based on the standards in place when they were built. When evaluating these existing communities as part of the investigation process, the objective is to achieve the same level of protection that is provided in new developments built to current standards.
Key Findings and Recommended Solutions (Basement Flooding and Sewer Backups)
Several factors contributed to widespread occurrences of flooding and sewer backups in the City’s west-end. The following is intended to highlight key findings and proposed solutions related to both the storm and sanitary sewer systems. Details that are more specific to each specific area (referred to as clusters) will be provided as part of the Action Plan to be tabled in Q1 of 2011.
Storm System
1. Overtaxed storm sewers and inadequate overland drainage:
The 24 July 2009 rainfall event exceeded the design capacity of the storm drainage system. This led to water entering basements through window wells, improperly sealed BWVs or cleanouts and floor joints around foundations. Water in basements evacuated through basement floor drains contributing high extraneous flows to the sanitary sewer system.
Recommended solution:
The solution includes two key elements.
The first is to limit the amount of water that enters the storm sewers to prevent the capacity of the pipes from being exceeded. This can be accomplished by installing ICDs in catch basins and sealing manhole covers, especially those that are likely to be submerged during a large rainfall event. The benefit of this approach is that by preventing sewer pipes from exceeding their design capacity there is less likelihood that water will backup in sewer laterals which places less reliance on BWVs as a means of protection. Implementation of this solution means BWVs will serve as a line of last defence, not a first line of defence. Implementation of these measures is underway as these can be done in a cost effective manner and with little disruption to the existing community.
The second element of this solution is to channel the water that accumulates on the surface to a suitable outlet. Where possible, this can be accomplished by redirecting the water to a surface drainage ditch, a stormwater multi-use dry pond created in a park or open space or allowing the water to accumulate on the road surface. The benefit of this approach is the water would be managed or conveyed away from private properties. While there may be temporary inconveniences of water accumulation on the road surface, or in other areas, for short periods of time after a large infrequent rainfall event, this would have significantly less impact as compared to water accumulating in people’s basements. This is the approach used for new communities.
These two measures can be readily implemented in Stittsville with minor adjustments to overland drainage patterns. In the case of Glen Cairn, more significant changes are required to address overland drainage, such as modifying some parks to provide surface storage and potentially acquiring a property in the Glamorgan area to improve an outlet for overland drainage.
2. High water level in Glen Cairn Stormwater Pond and Carp River:
Storm water in the Glen Cairn and Bridlewood North communities flows through the Glen Cairn Stormwater Pond (located on the west side of Terry Fox) before outleting into the Carp River. The pond provides both water quality and quantity control benefits.
The reach of the Carp River that flows through the Glen Cairn community also contributes flow to the pond. During large rainfall events, water accumulates in the pond, and this affects the water level in this part of the river. This section of the Carp River was the subject of previous channel improvements following a 2002 flood. Based on the available observations, there are no indications to suggest that the Carp River overtopped its banks during the 24 July 2009 event. The channel improvements were effective in reducing the impact of surface flooding in the community.
Since the pond and the Carp River serve as the outlet for the storm sewers, the capacity of the storm sewers are impacted by the outlet levels during large/infrequent rainfall events. This exacerbated the overtaxing of the storm sewers. As an interim measure, sump pumps are being recommended as part of the Residential Protective Plumbing Program for homes in Glen Cairn located in the area influenced by the levels in the Glen Cairn pond and Carp River.
Recommended solution:
As part of the Glen Cairn EA, different alternative solutions were considered, such as channelizing the Carp River to improve the outlet, modifying the pond to increase its capacity and providing a storm water pumping station at the wet pond to lower the water level during significant rainfall events. The objective of these alternatives was to improve foundation drainage for homes in parts of the Glen Cairn Community by providing a more efficient outlet for the storm sewer system. At this time, the preferred solution for the purpose of flood protection is the construction of a storm water pumping station, but a technical assessment is being finalized to determine if channelization of the Carp River would be a viable longer term consideration.
3. Overwhelmed drainage along Monahan Drain at Terry Fox Drive:
The TransCanada Trail (TCT), which intersects Terry Fox Drive, is the watershed boundary between the Carp and Monahan drainage systems. The area to the north of the TCT drains towards the Carp River and the area to the south drains towards the Monahan drain and on to the Jock River.
There is a culvert where the Monahan Drain crosses Terry Fox Drive. This culvert is designed to convey flow from a relatively small area. During the 24 July 2009 rainfall event, a large pool of water accumulated on the west side of Terry Fox Drive. This issue is still subject to more detailed investigation, but it appears the significant rainfall overwhelmed the Monahan Municipal Drain system and some flows were directed north towards the TCT instead of outleting to the south as intended under normal conditions. As noted, the TCT is the dividing boundary between the Carp and the Monahan systems, but there is a culvert located just east of the Hazeldean pumping station. This culvert is intended to drain rear yards from homes along Rothesay and the eastern portion of Glamorgan to the Monahan Drain. This culvert permitted flows from the Monahan Drain to reverse and move northward into the rear yards of the homes along Glamorgan and Castleglen and could have contributed flows to the Glen Cairn pond.
Recommended solution:
Grading and culvert modifications will be undertaken along the Monahan Drain, near the TCT, to minimize the risk of this situation reoccurring in the future.
4. High water level in Cattail Creek at Katimavik Road:
On 24 July 2009, high water levels were reported in Cattail Creek at Katimavik Drive. Debris, transported as a result of the storm, had partially clogged the grate of the culvert crossing Katimavik Road causing water to back into the yards of properties along Peary Way and enter basements through window wells and joints around basement floors. This resulted in high extraneous flows causing sewer backups in other homes in the immediate area. The grate has been removed until the situation is reviewed in more detail.
Recommended solution:
A hydraulic assessment was carried out to determine the capacity of the culverts and resulting water levels in Cattail Creek during large infrequent rainfall events. Based on the results, the recommendation is to increase the capacity of the existing culverts. During detailed design, the need for grating at the inlet will be reassessed.
5. Failure of BWVs on perimeter foundation drains:
Due to the significant rainfall, storm sewers were overtaxed causing water to backup in lateral connections, which created pressure on BWVs. Approximately 120 homes, mainly located in the Stittsville area, experienced failure of BWVs and this exacerbated extraneous flows to the sanitary sewer system.
Recommended solution:
In June 2010, Council approved report ACS2010-ISC-INF-0006 – Comprehensive Review of Storm and Sanitary Service Backwater Valves – Council Motion 71/11. This report included a comprehensive review to determine the mode of failure of BWVs during the 24 July 2009 event, a review of City standards with regard to current industry technology and practices, a comparison of the City’s requirements relative to peer municipalities, and a recommended plan to reduce the potential for future occurrences of basement backups related to the failure of BWVs. The following is a summary of the 5-step plan that was approved:
i. Continue with Sewer System Improvements
The City’s current Sewer Design Guidelines are based on preventing storm sewers from surcharging, therefore reducing the reliance on BWVs on perimeter foundation drains. When sewer system improvements are implemented, BWVs serve as a second line of defence instead of being the sole means of protection as is the case in communities built prior to the implementation of current standards.
ii. Expand Installation of BWVs
The review identified opportunities to increase the level of protection against sanitary sewer backups and recommended changes to the City’s Sewer Design Guidelines to include the mandatory installation of a BWV on the sanitary service lateral for all new home construction.
iii. Increase Homeowner Awareness
Through various discussions with property owners, it is apparent that many are not aware of the existence of maintenance requirements for BWVs and other measures to reduce the risk of basement flooding, including not connecting sump pump outlets to internal sanitary plumbing systems or directing eaves trough outlets away from the home. A number of measures were approved to increase homeowner awareness.
iv. Maintain BWV Inspection Practices
The City already includes two BWV inspections at different stages of construction, which is considered a best practice when compared to peer municipalities. Through the building and plumbing permit application processes, there is an opportunity to increase awareness with contractors and homeowners of the benefits of BWVs and other measures to reduce the risk of basement flooding.
v. Consult with BWV Manufacturers
The review identified technical differences related to the test pressures for the caps of storm BWVs. Follow up discussions will take place with manufacturers to raise this issue along with including maintenance literature when BWVs are purchased.
6. Alterations to roadside ditches:
In the Old Stittsville and Vanstone areas, roadside ditches provide storm drainage. In Old Stittsville areas, there appears to have been high levels of extraneous flows, as witnessed by the high flows experienced at the Fringewood pumping station during the 24 July 2009 event. This could be attributed to sump pumps being redirected away from the ditches to internal plumbing systems. For Vanstone, there have been alterations to the roadside ditches that have reduced the ability for the drainage system to handle large events. There are also eaves troughs that outlet at or near building foundations and this contributes to basement flooding.
Recommended solution:
For the Old Stittsville area, the high extraneous flows into the sanitary sewer system can be managed within the capacity of the existing system and will be the subject of further investigation.
For the Vanstone area, the intent is to reinstate roadside ditches along Vanstone Drive and Belleview Drive to improve the overall performance of the drainage system. Catch basins along the surrounding streets will be retrofitted with ICDs to limit inflow. Stormwater storage is proposed in the Hewitt, Irwin Gate and Stratas Court parks. Finally, a relief sewer is proposed to lower the hydraulic gradeline in the Hewitt Way storm sewer and direct it to the Hewitt Park storage facility.
Information will continue to be communicated to the residents on measures they can take to reduce the risk of flooding, such as directing water from eaves troughs away from foundations and not outleting sump pumps to the internal plumbing system. This was presented at the public open houses. A flyer will be prepared and delivered to homes in the affected area.
Sanitary System
1. High extraneous flows in sanitary sewers:
Sanitary sewers experienced extraneous flows significantly greater than what they were designed to handle leading to many occurrences of sewer backups in basements. These high extraneous flows were caused by basements flooded by storm water (as discussed above), entering through holes in maintenance covers that would have been submerged during the large rainfall event and through cross-connections.
Fog testing was undertaken in Glen Cairn, Katimavik and Beaverbrook to confirm the presence of cross-connections or other unwanted sources of storm water inflow into the sanitary sewer system. The fog testing identified one catch basin connected to the sanitary sewer system in the Beaverbrook area (this has already been corrected) and a number of other locations where storm water could enter the sanitary sewer system. It was also evident during the fog testing that there is potential for storm water to enter sanitary sewers through vent openings in the maintenance hole covers.
Recommended solution:
The solution includes three key elements:
The first, as discussed previously, is that restricting the flow into storm sewers to what the sewers can handle without surcharging will reduce the likelihood of BWVs failing under pressure and flooding basements. This will be accomplished through the widespread installation of ICDs in storm catch basins in all areas impacted by flooding in the Stittsville and Kanata South areas. The second element is the replacement of maintenance hole covers with solid covers. Approximately 1,400 covers will be replaced in all areas impacted in the Stittsville, Kanata South and Kanata North areas. Finally, the third element is to seal sanitary sewers and maintenance hole structures at locations identified by the fog testing to eliminate inflow sources. This will also cover the Rivington Street sanitary sewer in Carp.
The implementation of these initiatives has already been initiated.
2. Overtaxed sewage pumping stations:
Under normal operating conditions, pumping stations have adequate capacity to handle sewage flows. The high extraneous flows caused sewage pumping stations to operate at or above their design capacity (overflows occurred at Fringewood and Acres Road). This resulted in higher than usual levels in the sanitary trunk sewers further exacerbating sanitary sewer backups. This was particularly the case at the Hazeldean pumping station, which contributed to sewer backups in the Glamorgan area.
Recommended solution:
Implementing the measures to remove the extraneous flows from the sanitary sewer system, will reduce the risk of the levels reaching those experienced on 24 July 2009. Additional solutions at the Hazeldean station include improving the inlet configuration, providing a more effective overflow, increasing pumping capacity to provide a buffer between current demands and those expected from new developments and high levels experienced during severe rain storms. Technical details are being finalized as part of the Glen Cairn EA.
Other Findings (Culvert Failures)
The significant rainfall also contributed to failure of seven road culverts (all less than 3 m in size) in rural areas. None of these seven culverts contributed to basement flooding and did not result in injuries or damage to private properties.
The extent of failure varied by location. Joint failures on corrugated steel pipe culverts caused most failures and deterioration contributed to others. Corrective action has been taken for all culverts.
Homeowner Information
Homeowners can assist in reducing the risk of basement flooding due to sewer backups in a number of ways. One of the most effective means is the removal of uncontrolled stormwater from piped systems. Although, in isolation, one individual property's contribution might appear insignificant, downspouts from eaves troughs may be one of the causes of flooding in their basement, their neighbour's properties or the properties downstream in the sewer system. Another way homeowners can reduce the risk of flooding is to ensure storm backflow valves are functioning properly and cleanout caps located in their basement are properly sealed. A qualified plumber can assist with these works, if required. A checklist has been developed to assist homeowners with ways of reducing the risk of basement flooding. Residents continue to be encouraged to participate in the City’s Residential Protective Plumbing Program. Information on these topics is available at Ottawa.ca or at Client Service Centres.
Elements of the Action Plan
The following represents the key elements of the Action Plan to be finalized after completion of the Glen Cairn EA and the Peer Review.
Initiatives completed to date:
- Improvements made to the City’s emergency response procedures;
- Residential Protective Plumbing Program amended to enhance eligibility criteria;
- Sewer connection requirements in new developments modified to reduce the risk of increased flows in existing sewer systems until all protective measures have been installed;
- Sewer Design Guidelines amended to include the requirement for BWVs for sanitary sewer laterals for all new residential construction;
- Stormwater inflow sources to the sanitary sewer identified and being eliminated;
- Solutions identified for all affected areas; and
- Contract for sewer cover replacement and installation of ICDs awarded and implementation is underway.
- The Environmental Services Department recently implemented organizational changes to provide more focus related to surface drainage issues, including resident concerns related to debris along creeks.
In the short term (2010/2011):
- Finalize Glen Cairn EA for filing early in 2011;
- Finalize Peer Review;
- Continue with sewer cover replacement and installation of ICDs;
- Continue to eliminate stormwater inflow sources to the sanitary sewer system;
- Proceed to detailed design for more complex initiatives, such as the Hazeldean Pumping Station upgrades, surface storage in Glen Cairn, modifications to the Glen Cairn pond and installation of new sanitary sewer in the Leacock area;
- Review storm drainage system (Kanata North) for additional enhancements to level of protection; and
- Continue to provide information to residents on ways to reduce their risk of flooding.
In the long term (2012 and beyond):
- Proceed to construction with more complex flood protection initiatives.
This investigation extended to affected areas in the rural areas, such as those impacted by the culvert failures and the flooded basements in the Carp Village area.
Extensive public consultation has taken place as part of the overall investigation process. The following is a summary of the Public Meetings that took place since the July 24, 2009 flooding event:
- May 19, 2009 – Glen Cairn
- July 30, 2009 – Stittsville
- September 12, 2009 – Glen Cairn (South of Carp River)
- September 12, 2009 – Glen Cairn (North of Carp River)
- September 12, 2009 – Katimavik
- October 1, 2009 – Kanata North
- February 17, 2010 – Stittsville
- April 14, 2010 – Glen Cairn Community Association meeting
- September 7, 2010 – Kanata North
- September 13, 2010 – Katimavik
- September 15, 2010 – Glen Cairn
- November 1, 2010 - Stittsville
A PAC was established for the Kanata South area. This committee was engaged throughout the investigation process and was instrumental in providing information related to the flooding event and ensure information presented to the public was communicated in a meaningful way.
Further public consultation will take place when the Glen Cairn EA report is filed for the 30-day public review. This is expected to take place in early 2011.
WARD COUNCILLOR COMMENTS
The affected Ward Councillors are aware of this report.
There are no legal/risk management impediments to implementing the recommendation in this report.
CITY STRATEGIC PLAN
This report is consistent with the Service Delivery priority of the City Strategic Plan.
N/A
The financial implications for all of the recommended solutions are being finalized and will be provided as part of the Action Plan to be tabled in Q1 of 2011, after completion of the Peer Review. The financial requirements will also be identified in the 2011 Draft Capital Budget.
Infrastructure Services will finalize Phases 3 and 4 of the investigation process and table the Action Plan for approval in Q1 of 2011.