Preface
This is the second edition of CSA S503, Community drainage planning, design, and maintenance in northern communities. It supersedes the previous edition published in 2015.
While this Standard is intended to be comprehensive, specific agencies might need to refine procedures as appropriate for their own usage.
The Standard was developed through the collaboration from many knowledgeable experts and representatives from Canada's territorial governments and the private sector.
CSA Group received funding for the development of this Standard from the Standards Council of Canada, as part of the Northern Infrastructure Standardization Initiative with input from the Northern Advisory Committee (NAC).
This Standard was developed by the Working Group on Community Drainage System Planning, Design and Maintenance under the jurisdiction of the Technical Committee on Northern Water, Wastewater and Stormwater and the Strategic Steering Committee on Natural Resources, and has been formally approved by the Technical Committee.
This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group.
Introduction
0.1 What is unique about the North and northern surface drainage systems
Northern Canada’s surface drainage systems are unique due to climatic variation, geography, geology, demography, and culture. The North is a region with long periods of extremely low temperatures; it is a region that is exceptionally large, diverse, and remote; it is a region with permafrost and other ground- related engineering challenges; it is a region of small, isolated communities with low population density; and, it is a region with a large indigenous population. As much as these different attributes contribute to community diversity in the North, all these communities face similar surface drainage system challenges, and subsequent costly operations.
While the winters are long and cold, it is the short warm summers and brief shoulder seasons of spring and fall that create the perpetual surface drainage issues that are catastrophic in the extreme case, and a constant challenge year after year.
0.2 Challenges for drainage design and operation in northern Canada
There are no simple, quick-fix permanent solutions to surface drainage issues in northern communities. Short construction seasons, remote locations, limited community capacity, and challenging ground conditions create a complex web of persistent issues year after year that must be resolved. As an example, the logistics involved in the installation or replacement of a simple culvert can be challenging. First, the correct size of pipe must be purchased well in advance of when it is needed. It might need to be delivered by winter road or ship, both of which operate in a narrow seasonal window. Availability of manpower and equipment cannot be assumed; these resources might have already been committed to other projects during the brief summer construction season.
Even when the necessary resources are available, the location, local ground conditions (such as the presence of permafrost), and the quality or quantity of available material will influence, for example, how culverts are installed in a specific community and how long they might remain functional.
The effects and scale of climate change are quickly emerging as the biggest challenges in the design and operation of northern surface water drainage systems. These challenges are compounded by the limited climate data available, adding to the risk and uncertainty. Limited and incomplete information is the norm in northern Canada. Consistent and regular annual maintenance is expected. However, regular maintenance alone is not sufficient to address the risks, challenges, and impacts of unpredictable catastrophic events where immediate response is required and repair capabilities are limited.
In most northern communities, drainage system planning, design, and maintenance are often carried out in an ad hoc and reactive manner. Community planners, engineers, and asset managers from across Canada's three territories, as well as Newfoundland and Labrador and Nunavik, have emphasized that conventional drainage planning and design approaches, as well as necessary maintenance practices, are inadequately defined and poorly understood. The result is routine and chronic degradation of community infrastructure across the North. Proper drainage planning, design, and maintenance practices are essential to maintain service life and protect community infrastructure.
Many professionals agree that the changing climate has, and will continue to, alter northern weather conditions. Observed impacts in the North include
a) an increase in the frequency of extreme weather events resulting in greater snow accumulation, winter rain, icing, and higher winds;
b) rapid spring melting;
c) more sudden, intense precipitation events; and
d) greater weather instability in general.
Climate change in northern Canada is occurring faster than expected, resulting in increasingly frequent and unpredictable extreme weather events. Drainage planning, design, operation, and maintenance practices must change and adapt. New tools and adaptation strategies are needed to manage the effects of climate change on community surface drainage systems. The preparation of community surface drainage plans is a first step.
Climate change assessment and adaptation tools are only now being developed and applied to infrastructure projects. One such tool, vulnerability assessments, is still in its infancy and, therefore, not routinely conducted in northern communities. Vulnerability assessments have been carried out at the territorial and regional levels, albeit in much less detail. In most cases, the impacts of snowmelt and precipitation-driven runoff have been identified as significant risks to a community. Adaptation plans have been developed for selected northern communities, including Whitehorse and Yellowknife, as well as hamlets as small as Clyde River in Nunavut.
The results of vulnerability assessment studies that have been undertaken in the North so far have confirmed that existing drainage plans and infrastructure are often inadequate to accommodate the effects of a changing climate. In many instances, levels of service are insufficient and repairs to drainage infrastructure are infrequently and non-routinely conducted. These issues ultimately result in more expensive repairs in the future. Other conditions often associated with climate change, such as warming and degrading permafrost conditions and pronounced local shifts in hydrogeology, are creating new drainage problems within communities and making existing problems worse. Furthermore, human activities that cause changes to the ground surface can have an impact on the ground thermal regime with subsequent impacts on drainage conditions.
Reducing the vulnerability of infrastructure to climate change is of critical importance for several reasons including cost and limited resources. Traditionally, there is limited redundancy built into northern infrastructure in part due to the associated high costs and the complexities that exist in remote communities. This is especially true when it comes to high-value community assets such as schools, medical buildings, community centres, and any building identified as essential infrastructure (per the National Building Code of Canada). As problems associated with the changing climate worsen, northern governments and other stakeholders are recognizing that hard choices can no longer be put off. Better tools are needed now to make decisions for infrastructure adaptation.
0.3 Overview of community drainage systems
Community drainage systems collect runoff water from snowmelt, ice melt, precipitation, and storm events. These systems convey surface water in a planned way, either through or around the community. Drainage is collected at the lot, neighbourhood, and community-wide level, subsequently discharging the accumulated run-off down-gradient where it can be accepted into wetlands, water bodies, and landscape features, or infiltrated to the groundwater table. Care should be taken to confirm that contaminants are not introduced to the environment.
The community's drainage system needs to be planned, designed, constructed, and maintained with the capacity to handle the aggregate flow of water from all catchment areas within the community, as well as surface water that originates from outside the community and flows through the community due to topography or other factors.
0.4 Purpose of this Standard
This Standard specifies the minimum planning, design, and maintenance requirements for community drainage systems in Canada's northern communities. The purpose of this Standard is to increase the capacity of communities and individuals to prepare and implement effective community drainage plans. These plans address both existing and anticipated drainage management challenges arising from deficiencies in past practices, as well as the need to adapt to future changes in climate.
Drainage systems in small, remote northern communities have historically been poorly developed and managed. This Standard provides guidance to practitioners who are involved in the planning, design, construction, rehabilitation, and maintenance of drainage systems in northern communities.
The provisions of this Standard are derived from existing best practices and may be incorporated directly into community land use plans. Additionally, this Standard is intended to
a) specify techniques to plan for and implement community drainage systems to account for the effects of a changing climate and permafrost regime;
b) describe practices for site and community planning that help to maintain the service life of community infrastructure, as well as the natural landscape processes through avoidance, mitigation, and drainage system management practices;
c) provide low cost, practical solutions that can be adapted and implemented given local constraints on capacity and resources;
d) help northern communities protect community assets; and
e) promote public health and safety in northern communities.
0.5 Guidance to users
This Standard is designed to appeal to the needs of three audiences. The first group are the community administrators, owners of land and buildings, and asset managers, including regulators and inspectors, who are involved in decisions around selecting the drainage system to be used. This group includes the people who are responsible to ensure these systems are constructed and operated properly. The second group includes those involved in the planning and design, overseeing construction, operation, and maintenance of the surface drainage infrastructure. The third group includes those who need to understand how incorporation of best drainage practices can mitigate the impacts of a changing climate (e.g., policy makers).
Users should be aware of the requirements of the regulatory authorities having jurisdiction for design construction, operation, and maintenance of drainage systems and their associated components in northern regions. This includes all federal, territorial/provincial, and regional acts, regulations and municipal bylaws applicable to land and water use management, community infrastructure development, and building construction.
This Standard is organized to help users proceed sequentially through the three key steps in the implementation of a community surface drainage system. These steps are planning and design, construction, and maintenance and repair.
To prepare a new or updated drainage plan, begin with Clause 4.
Community drainage system planning should be integrated into community plans, policies, and existing zoning bylaws where they exist. Information inputs such as site characterization, hydrology, topography, surficial geology, climate data, and maps are required to develop drainage plans as well as overall community plans. However, a lack of a community plan should not preclude the development of a drainage plan, as one can be developed in the absence of a community plan.
Community drainage system design requirements are given in Clause 5. The basic requirements of community drainage system design might be enough to service some communities, while for others the requirements serve as a foundation upon which additional system design elements can be layered and tailored to meet local needs and circumstances.
Communities with fully or partially developed surface drainage systems should review their drainage system plans against the requirements in Clause 4and their system designs against the requirements in Clause 5 before beginning to modify an existing system.
Requirements for the long-term care of community drainage systems are described in Clause 6. These requirements are discussed in the context of life cycle asset management, level of service standards, and subsequent operational decision making. Implementation can be phased to reflect existing drainage infrastructure conditions, anticipated community growth, and best practices for system planning and design, construction, maintenance, and repair.
Scope and application
1.1 Scope
This Standard specifies provisions for the planning and design, operations, and maintenance of surface drainage systems within northern community boundaries. Provisions for drainage outside the community boundary are generally not covered by this Standard.
Note: Specific resources and expertise are required to address watershed-scale drainage provisions outside the community boundary. These resources and expertise are often not available at the community level or are beyond the mandate of an individual community.
1.2 Application
This Standard specifies provisions for site-level and community-wide drainage system planning, development, and operations. The provisions apply to drainage systems used for the collection, conveyance, detention, and discharge of excess surface water in the form of overland flow, originating from precipitation, snowmelt, or ice melt. Excess surface water is net of precipitation, soil infiltration, and evaporation.
1.3 Exclusions
This Standard does not cover
a) drainage systems associated with facilities that might inherently produce contaminated drainage, such as
i) solid waste management systems and components; and
ii) sewage treatment systems and components;
b) drainage issues resulting from storm surges in lakes or oceans;
c) drainage directly from riverine flooding;
d) subsurface drainage; and
e) watershed level drainage planning.
Note: Certain drainage circumstances are not considered in this Standard because they have requirements that are beyond the resources and expertise of many northern communities. Where applicable, these circumstances have been identified.
1.4 Dual measurements
The values given in SI units are the units of record for the purposes of this Standard. The values given in parentheses are for information and comparison only.
1.5 Terminology
In this Standard, shall is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; should is used to express a recommendation or that which is advised but not required; and may is used to express an option or that which is permissible within the limits of the standard.
Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate normative clauses from explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements.
Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.
