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Nunavik First Nation community combats drainage challenges
Whapmagoostui is a Cree First Nation community located at the mouth of the Great Whale River, as it flows into Hudson Bay in the province of Quebec. Their reserved land is attached to the Eeyou Istchee territorial government, but located in Nunavik territory, slightly north of the 55th parallel.
The community shares this territory with their neighbouring Inuit community of Kuujjuarapik. Accessible by air and sea only, the two communities combined are home to approximately 1,800 people and are not connected to any of the southern road network.
With a freezing index in Whapmagoostui of 2,800 degree below Celsius days, above zero-degree daily temperature averages occur only from June to October, and monthly precipitations are above 60 mm from June to November. The combination of these factors was critical to the projects and led to many challenges for the community and the teams working with them on a major drainage project.
DRAINAGE PROBLEMS IN WHAPMAGOOSTUI
Geographically speaking, the land of the Whapmagoostui Indigenous Nation made for quite a challenging project. The surface is flat, and with a road network of only approximately 6 km and made of gravel, delivery had to be well thought out and planned.
Surface drainage infrastructure was practically nonexistent on the territory, apart from the presence of storm sewer pipes underneath two street segments. One of these storm sewer lines was connected to an outfall pipe discharging directly into the Great Whale River.
For most surfaces within the perimeter of the community, runoff water was conveyed through shallow roadside ditches and a few culverts, with no catch basins connected to an outlet piping to properly evacuate the water. Flooded surfaces on both streets and private and public properties appeared after heavy rainfall episodes in the summer (insufficient hydraulic capacity), and during the melting season in the spring (frozen catchment points, outlets and granular base).
Flooding had a direct impact on human activities, and pedestrian and vehicle movements were made difficult, if not impossible. Flooded areas appearing in the school vicinity also represented a health and safety hazard for children and the community.
On top of improper infrastructure, the effects of climate change had worsened the problems, with newly observed drastic daily temperature changes as spring approached and increased snow melt episodes in the shoulder seasons. These freeze-thaw cycles created potholes and cracks in the gravel street surfaces and consequently increased maintenance costs. The same type of damage occurs in the summer as increased rainstorm intensities are observed.
Finally, an increase in flash flooding and water accumulation episodes in the scarcely wooded environment of Whapmagoostui, creates an additional problem of sediment transport and settlement in the drainage system and in more sensitive parts of the natural environment.
PLANNING A SOLUTION
Beginning in 2016 and working with the help of the CIMA+ engineering team, the Cree Nation Government (CNG) and the Whapmagoostui First Nation (WFN) community representatives developed a plan to resolve the drainage and other infrastructure problems facing the community.
One of the key objectives in drafting this plan was to find ways to increase the
Construction of the stormwater detention chamber system.
participation and apprenticeship from local personnel and resources in each step of the process. As a result, a threefold plan was drafted: 1. Design a drainage master plan. 2. Recruit and train a local construction crew. 3. Coordinate the effort and commitment from CNG, WFN and CIMA+ representatives towards a work schedule that ensured construction materials, equipment and machinery required each year were designed, purchased, shipped (and properly stored) on site by air or sealift, in time to maximize the construction period.
THE DRAINAGE MASTER PLAN
CIMA+ was mandated to design a new storm sewer, and an outfall pipe to the Great Whale River. This system was designed to alleviate the flooding problem next to the primary school. While proceeding, it became clear that a different plan would be required to address the water accumulation problems occurring at other places in the community.
At the onset, CNG and WFN were called upon to assess the need to surface the streets of Whapmagoostui with asphalt pavement, as in the neighbouring community of Kuujjuarapik. The decision was made in favour of asphalt surfacing, and impervious surfaces runoff coefficients were used for the street surfaces in the calculation of flow rates.
Because of the community’s flat land surface, it became necessary to consider M the use of multiple outlets and conveyance infrastructure with greater hydraulic capacity. Piping systems were therefore added to the existing ditch system. To minimize pipe trenching depth and width, the use of detention chambers was considered to create hydraulic brakes.
These underground chambers were also a means to transfer excess water to underground equipment that would otherwise create flooding above ground. It was found that these chambers also contributed to sediment control before discharge into the environment.
The community’s wish was to opt for the construction of traditional paved streets with concrete curbs. This meant constructing a conventional storm sewer
C Y CM MY CY CMY K WFN recruited local personnel to form a construction crew that would, in time, qualify to operate the required machinery and equipment for trenching, backfilling, laying pipes, etc.
system with underground piping and catch basins bordering the curbs. The use of detention chambers remained the preferred element for the system to help reduce flooding and surface water accumulations at various locations within the community.
The resulting plan was a carefully engineered combination of conventional continued overleaf…
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(southern) drainage techniques and community-oriented solutions adapted to northern conditions. It also considered the Community Drainage System Planning, Design and Maintenance in Northern Communities (CAN/CSA—S503-15 standard, 2013) guidelines.
LOCAL CONSTRUCTION CREW
WFN recruited local personnel to form a construction crew that would, in time, qualify to operate the required machinery and equipment (excavator, compactor, etc.) for trenching and backfilling, laying pipes according to specified slopes, installing manholes, catch basins and waterline accessories. They were also responsible for the planning and execution of any work related to water and sewer systems.
This team was placed under the supervision of a senior site inspector from CIMA+, an experienced municipal public works coordinator. He supervised the training of the Cree construction crew and monitored their progress in the learning process. The team worked together for six consecutive construction seasons and is now capable of planning and conducting pipe laying work as an autonomous unit.
DESIGN, PROCUREMENT AND SHIPPING
Transportation and shipping of heavy machinery and materials to Whapmagoostui could only be done by sealifting out of the Eeyou Itschee coastal communities (Wemindji). The frequency of these transports was dependent on navigation constraints and under occasional severe sea conditions.
In order to start the construction work activities as soon as the weather and the soil conditions would allow it, the necessary materials and equipment had to be shipped and stored on site, ahead of time. In some instances, this required using the last scheduled barge departure a year in advance. The importance of careful planning for each activity led to an efficient on-site construction process.
CURRENT AND PROPOSED SITE DRAINAGE CONDITIONS
The drainage master plan was presented to the community in April 2017, but went through some major changes as the decision to pave the streets and install concrete curbs was made some time later. Some significant parts of the plan were built between 2016 and 2018. 2016 saw the installation of a new storm sewer, connected to an outfall pipe leading to the Great Whale River, and was installed on Gakw Street. Also in 2016, a storm sewer line was built in front of the community primary school on Whapwakw Street, with the first detention chambers installed at the back.
Phase 2 of the plan started in 2017. A new storm sewer pipe was installed in Whapstan Street, connecting the newly installed line in Gakw Street to the one of the few already existing storm sewers
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located in the hospital sector. The final connection for the detention chambers at the back of the primary school to the storm sewer of Whapmakw Street was also completed that year.
In the spring of 2018 and throughout the summer of 2018, no water accumulation was observed in the areas surrounding the primary school. The underground detention chambers were performing to the expected level to prevent surface water accumulations.
Finally, in 2018, a second major storm sewer line was constructed, with the second outfall pipe leading to the Great Whale River. Since 2019, close to 5 km of storm sewer lines have been installed, officially ending the Drainage Master Plan project. This workload was coordinated with the street paving program over a planned three-year program. A last phase remains to be completed with road paving and is scheduled to begin in 2022. References available on request.
Aerial view of Whapmagoostui.
Yves Durand, Andreanne Dumont and Isabelle Beaulac are with CIMA+. Email: yves.durand@cima.ca, andreanne.dumont@cima.ca, isabelle.beaulac@cima.ca, or visit: www.cima.ca
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