By Matthew Lozie
Home of the Yukon Gold Rush, Dawson City is a community of less than 2,000 people, However, this nearly doubles in population during the summer tourist season. The city offers a look into the past as it continually tries to maintain the original look and feel of its Klondike era.
The city provides residents with drinking water from four wells located near the adjacent Yukon River. Its existing water treatment plant was dated, cramped and did not meet the Canadian Drinking Water Quality Guidelines for well water. During the conceptual design stage, it was determined that a new treatment plant was required. Several locations were identified for a new facility.
The Yukon Government retained Associated Engineering to provide design and construction services for the new Greenfield water treatment plant. Together with Yukon-based Kobayashi + Zedda Architects, Associated Engineering provided a preliminary design for the plant, to be situated on two adjacent city lots along the prominent 5th Avenue.
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In keeping with the city’s historic setting, the design of the facility had to remain authentic to the gold rush theme. The Heritage Advisory Committee conducts a rigorous review of all new buildings in Dawson City. Initially, several building representations were proposed, including a boomtown store front. Through the consultation phase, it was decided that the building exterior would be a replica of an early 1900s cold storage building. The facade features a board and batten siding with a prominent front peak, narrow windows and a spiral staircase.
During design, several unique challenges were encountered. Due to the location of the city in a valley next to a river that is prone to ice damming and flooding, flood damage prevention was an important consideration, as well as the impact of climate change. To improve the facility’s flood and climate resilience, major electrical and controls equipment were placed on the second story of the building.
The first story was constructed from concrete. A wood frame and steel post and beam structure with dowel laminate timber panels for the roof structure were selected due to constructability restraints in this remote community.
Design of all the facility’s components considered the cold climate environment. Insulated high density polyethylene (HDPE) material was used for the extensive civil piping outside the water treatment plant, and heat tracing was used for aboveground piping.
Four different forms of energy provide power and heat to the plant. Treated water for distribution requires heating and the pipes are looped back into the plant from the distribution system to provide constant movement through the system to prevent freezing. Water is heated by a set of oil-fired boilers, as well as a heat exchanger that draws heat from the local biomass plant through an underground heating loop.
A solar photovoltaic system was added to the roof of the plant which will be used mainly in the spring and summer, making use of the extended daylight hours to supplement the building power requirements provided by Yukon Energy service. A variable speed fire pump was selected to reduce the building and backup generator sizes and maintain even water service pressure in case of a fire.
Water treatment technology consists of cartridge filters followed by ultraviolet (UV) and chlorine gas disinfection. Alternative filtration was considered, but cartridge filters were selected due to the high quality of the well water and the simplicity in operation of the system. Particle distribution analysis and total suspended solids analysis of treated water showed that cartridge filters provide appropriate treatment.
Associated Engineering created a building information modeling (BIM) model of the plant using Revit and AutoPlant that helped operations staff to visualize the plant and provide feedback.
Construction of the 6 million litres per day plant started in May 2018 and was completed in December 2019 at a cost of $13 million.
Matthew Lozie, P.Eng., is with Associated Engineering. This article appears in ES&E Magazine’s February 2020 issue.
