CSA S503:15 (R2019)

Preface

This is the first edition of CAN/CSA-S503, Community drainage system planning, design, and maintenance in northern communities.

Although this Standard is intended to be comprehensive, specific agencies may 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 Standards Council of Canada, as part of the Northern Infrastructure Standardization Initiative, supported by the Government of Canada's Clean Air Agenda.

In addition to the members of the Working Group and Technical Committee, CSA Group acknowledges the contributions made by Dennis Althouse, Chad Cowan, and Megan McGarrity.

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 Built Infrastructure and the Strategic Steering Committee on Construction and Civil Infrastructure, and has been formally approved by the Technical Committee.

This Standard has been approved as a National Standard of Canada by the Standards Council of Canada.

Introduction

0.1 What is unique about the north and northern surface drainage systems

The north of Canada is very unique due to its climate, 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 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 a diversity of communities in the north, a commonality between northern communities across the country is the challenges around surface drainage systems.

While the north may be regarded as a region of perpetual ice and snow because of the long and cold winter season, 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 systems in the north

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 amongst other factors create a complex web in which the persistent issues of northern drainage must be addressed. 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 may 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, as these resources might have already been committed to other projects during the summer construction season.

Even if all of the resources are available when required, the location, local ground conditions such as the presence of permafrost, and material available will influence how the culvert is installed and how long it might remain functional. The effects of climate change create challenges for the design of drainage systems in the north where there is often limited climate data available, adding to the risk and uncertainty. The situation described above is a common scenario. It assumes the predictability of the need for regular annual maintenance. It does not anticipate or address the risks, challenges, and impacts of unpredictable catastrophic events where immediate response is required and options are limited.

In most northern communities, drainage system planning, design, and maintenance are often described as ad hoc processes. 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, approaches to design, and maintenance practices are inadequately defined and often poorly understood. The result is routine and chronic degradation of community infrastructure across the north. Proper drainage planning, design, and maintenance practices are essential for the protection of community infrastructure.

The effects of a changing climate bring additional challenges to the process of planning, designing, and maintaining northern drainage systems. Irregular and, in some cases, extreme events appear to set aside what might have been considered normal in the past. Many professionals agree that the changing climate has and will continue to alter northern weather conditions. Observed impacts in the north include:

- An increase in the frequency of extreme weather events resulting in greater snow accumulation, winter rain, icing, and higher winds;

- Rapid spring melting;

- More sudden, intense precipitation events; and

- Greater weather instability in general.

All of these weather factors in the north influence how drainage planning, design, operation, and maintenance now need to be done. 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 only a first step.

Climate change assessment and adaptation tools are only now beginning to be developed and applied to infrastructure projects. One such tool, vulnerability assessments, is still in its infancy and is not routinely conducted in northern communities. Adaptation plans have been developed for selected northern communities, including Whitehorse and Yellowknife, as well as hamlets as small as Clyde River in Nunavut. Vulnerability assessments have also 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.

The results of vulnerability assessment studies that have been undertaken in the north are confirming that existing drainage plans and infrastructure are often inadequate to accommodate the effects of a changing climate. In many instances, service levels are insufficient, and repairs to drainage infrastructure are infrequently and non-routinely conducted resulting in ultimately 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 which cause changes to the ground surface can have an impact on the ground thermal regime with subsequent impacts on drainage conditions.

All regions of Canada are experiencing environmental, social, and economic impacts that might be attributed to a changing climate. In Canada's north, the climate appears to be changing at a much faster rate than the rest of Canada, creating increasing challenges for northern communities. Reducing the vulnerability of infrastructure to climate change is of critical importance for several reasons including cost and intervention capacity. 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 key 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 and 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 drainage away from community sites, whether an individual lot, a community block, a community neighbourhood, or the entire community to a point down gradient where it no longer impacts the site.

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 that must flow through the community because of 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

- specify techniques to plan for and implement community drainage systems to account for the effects of a changing climate and changing permafrost regime;

- describe practices for site and community planning that help to conserve community infrastructure, or at least avoid actively contributing to its degradation;

- provide solutions that are low cost and implementable given local constraints on capacity and resources;

- help northern communities protect community assets; and

- 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, building and land owners, and asset managers, including regulators and inspectors who are involved in selecting the drainage system used and ensuring it is constructed and operated properly. The second group includes those involved in the planning, design, 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 authorities having jurisdiction for the design, construction, and maintenance of drainage systems and their associated components in northern regions. This includes all federal and territorial acts and regulations and municipal bylaws applicable to land and water use management, community infrastructure development, and building construction.

This Standard is organized to help the user proceed sequentially through the three key steps in the implementation of a community surface drainage system. These steps are planning, design and construction, and maintenance and repair. The plan should identify

- surface water management challenges specific to a community's needs and circumstances;

- the vulnerabilities of the community and the management of identified risks;

- the implications of any risks from a health, safety, and system asset management perspective; and;

- guidance on best management practices to mitigate risks through community planning, land use management, and system design, construction, and maintenance.

To prepare a new or updated drainage plan, begin with Clause 4, Community drainage system planning. Community drainage system planning should be integrated into community plans, policies, and existing zoning by-laws 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 may be sufficient to service some communities, while for others the requirements serve as a foundation upon which additional system design elements will be layered and can be tailored to meet local needs and circumstances.

Communities with fully or partially developed drainage systems should review their drainage system plans against the requirements in Clause 4 and 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. They are discussed in the context of life cycle asset management, level of service standards, and subsequent operational decision making. Implementation can be in phases taking into account existing drainage infrastructure conditions, anticipated community growth, as well as best practices for system planning, design, construction, maintenance, and repair. A community with a partially or fully established drainage system may opt to adopt only the maintenance requirements.

Scope and application

1.1 Scope

This Standard specifies provisions for the planning, design, and maintenance of surface drainage systems within northern community boundaries. Provisions for drainage outside the community boundary are not covered by this Standard.

Note: Specific resources and expertise are required to address drainage provisions outside the community boundary. These resources and expertise might be beyond the capacity 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.

Note: 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 directly 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.

1.4 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.