BEHCHOKO, NWT – WATER SUPPLY PLANNING STUDY

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CSCE 2021 Annual Conference Inspired by Nature – Inspiré par la Nature

26-29 May 2021

BEHCHOKO, NWT – WATER SUPPLY PLANNING STUDY Johnson, K 1,3, Lanteigne, M2, and Keung, C1 1

EXP, Canada AECOM, Canada 3 ken.johnson@exp.com 2

Abstract: Water Supply for the Edzo settlement of Behchoko in the Northwest Territories currently consists of a surface water intake and pumphouse located in a river channel between Marian Lake and Great Slave Lake. Water and sewer are conveyed through a buried pipe system. In late winter there is a reoccurring issue of complete freezing of the water channel, and in response, water must be trucked to the water plant at a considerable cost. Edzo initiated a water supply planning study of the relative economic costs of alternate water sources for the community. Six alternate options were considered to replace the existing water supply system. The options ranged from various surface water sources adjacent to Edzo as well as ground water. The water quality of the various surface water bodies is similar with elevated concentrations of colour, iron, aluminum, and turbidity. The water quality of the well water is anticipated to have elevated iron, manganese, and hardness. The existing water treatment facility will be able to treat all the surface water sources. The six water supply options were analysed, and the well water option was eliminated from further consideration because of quantity limitations and water treatment requirements. Based upon analyses, it is recommended that the existing water supply from the West Channel be maintained with additional infrastructure, including a raw water reservoir. This option has the lowest anticipated capital cost, and operation and maintenance costs. 1

BACKGROUND

Edzo is a community located at 62o 40’ north latitude, and 116o 04’ west longitude, and is one of two settlements associated with the Tłı̨ chǫ Community Government of Behchokǫ̀, which also includes the larger community of Rae. Edzo is 106 km northwest from Yellowknife along Highway 3 and is located on a peninsula in Marian Lake approximately 24 kilometres away from Rae. The Edzo settlement is bounded on the north by Marian Lake, on the south by the North Arm of Great Slave Lake, and on the east by the West Channel between Marian Lake and the North Arm of Great Slave Lake. Edzo was constructed by the Government of the Northwest Territories in the late 1960’s and early 1970’s as an alternative townsite to Rae. The Rae townsite had planning issues with limited space for community expansion, as well as public health issues because of concerns about contaminated surface runoff impacting the drinking water supply. The first roads in Edzo were built in 1969 and the construction of the water and sewer systems began in 1970. At that time two wells were drilled within the community for the supply of potable water. Soon after the wells were commissioned, it was found that they did not have sufficient capacity to supply the community. This led to the development of a nearby surface water source which pumps raw water from the West Channel on the east edge of the community to a water treatment facility through a buried pipeline, and then subsequently distributes treated water through a buried water supply system. Low water levels in West Channel occurring in late winter, compounded by freezing of the channel have caused problems with the water supply for several decades. In the past, when this situation occurred, an alternate water supply was sourced by either trucking raw water from other locations to the water GEN 410-1


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