Building a water treatment plant for a remote community with extreme weather conditions comes with a unique set of challenges. Kugaaruk, Nunavut, an Inuit community with a population of 770 and growing, is the location of the coldest wind chill ever recorded in Canada, -92°C in 1975. The sea around Kugaaruk is teeming with narwhals, belugas, walruses and polar bears. The land has been a traditional hunting ground for thousands of years.
The hamlet’s water treatment plant was built in the late 1980s. It chlorinated raw water but there was no filtration or redundancy. Source water is from a manmade reservoir along the Kugaaruk River, two kilometres northeast of the Arctic bay. The bay and river surface are frozen most of the year, and when it does thaw, there are very high levels of sediments and dissolved minerals.
The plant was suffering from extensive corrosion due to chlorine spills. Some of the pipes and fittings were growing green from chlorine contact. Vandalism from hunters in the area and fire damage to one of the two generators also took its toll. As there was no utility power available until September 2013, the only power available to the plant was from a diesel generator.
According to the operators, residents considered the water from this plant to be undrinkable or over-chlorinated most of the time. They would often drive to the reservoir to refill their household water tanks rather than use water treated by the plant. In January 2010, a tidal surge introduced salt water into the reservoir, forcing residents to transport water by sled from the river upstream.
In 2012, BI Pure Water and Williams Engineering of Yellowknife were contracted by the Nunavut government to design, build and deliver a modular water treatment system to Kugaaruk. The engineering objective was to maintain functionality and reliability of the water system in consistently subzero, and often -40oC temperatures. Mobility was also a consideration. It was thought that, if salt water incursions occurred again, the plant would have to be relocated further upstream.
The site engineering for a more effective water system involved positioning the intake lines between the river surface ice, which can be 2 m or more deep, and avoiding near-bottom layers where river sediment or pockets of salt water may be present. New screens were installed on the intake pipe, and it was raised above the river bottom. Salinity sensors were installed to alert the operator of possible salt water contamination.
A new plant with two independent parallel treatment trains was designed. It included submersible intake pumps, high efficiency cartridge filtration, UV primary disinfection, chlorine residual disinfection and dual truck-fill stations, for 100% redundancy. As the UV lamps take several minutes to warm up and cycling them too often can shorten their operating life, it was decided that they would remain energized 24 hours a day.
During extended periods when no water is flowing from the reservoir into the delivery trucks, a small volume of water is retained and re-circulated through the UV units to cool the lamps. Excess heat is then transferred to the interior walls of the water treatment plant through heat exchangers, reducing demand on the interior heating units.
The old building was completely refurbished and converted into a chlorine storage and backup generator building. New chemical resistant cabinets were installed, with appropriate ventilation, for secure storage of the water treatment chemicals.
The new treatment plant not only called for ingenuity in engineering, but also in construction and delivery. It was built from three modified sea containers at BI Pure Water’s factory in Surrey, British Columbia. It was then loaded onto semi-trailer trucks for delivery to Montreal. From Montreal it was shipped to Nanisivik, a Canadian Forces naval facility at the eastern entrance to the Northwest Passage.
With perpetual broken ice in the Kugaaruk area even in summer, shipments usually have to be transferred onto a Canadian Coast Guard icebreaker to complete the final leg of the journey. The normal icebreaker serving this region, the CCGS Terry Fox, was being refitted in 2013. The replacement vessel was smaller, reducing the normal size and weight limit for cargo. So, the original engineered length of the treatment plant and weight of all its components had to be reconfigured.
Once the plant containers arrived on the open tundra, BI Pure Water staff had to complete the build of the system on site beside the reservoir.