SOMBA K'E/YELLOWKNIFE - The city is considering changing its drinking water source to Yellowknife Bay from the Yellowknife River - a switch that would require an arsenic treatment system.

The recommendation, from Edmonton-based AECOM, the company hired by the city to design the new water treatment plant to be constructed next year, was presented to about 30 Yellowknifers Tuesday night during an information session at the Yellowknife Inn.

Richard Tombs, a process engineer for AECOM, told the crowd that the consensus within his company is the city should move "forward with the design of a water treatment plant that utilizes the bay as the raw water source, that includes an arsenic treatment stage to address the annual variations in arsenic and the presence of Giant Mine."

The recommendation came with resistance from residents.

"I live here and lived here for decades," said Lorraine Hewlett. "It's really, to me, really very upsetting, the idea that our water source would be drawn downstream from a toxic waste site," she said, referring to Giant Mine, where arsenic cleanup is currently underway.

"I really in my heart feel that if you were to ask people in Yellowknife, 'Do you want to draw your water source from upstream of the toxic waste site or from downstream of the toxic waste site?' I'm pretty sure the majority of people would say upstream."

According to the Canadian Drinking Water Quality Guidelines, the maximum arsenic concentration allowed in water is 10 parts per billion. In studies done by the city since 2005, water in Yellowknife Bay has not exceeded that number, and in most cases, it was less than three parts per billion, said Tombs.

"Under the current license for water supply for the city of Yellowknife, Yellowknife Bay can be used for an emergency source of water and it has been used previously when the pipeline has required repairs," said Tombs, noting that both the bay and river are stable, high-quality water sources.

Tombs said the 8-km-long underwater pipeline used to bring water from the river to Pumphouse No. 1 downtown is reaching the end of its lifespan. The pipeline, which has been in place since 1968, needs to be replaced by 2020, he said, adding this was a major consideration in the change of water source.

The replacement would cost the city around $10 million, while the installation of an arsenic treatment system at the new water treatment plant - if Yellowknife Bay becomes the city's water source - would be about $3 million, said Tombs.

Long-time Yellowknife resident Eric Henderson, who attended the meeting, questioned the city's desire to change the "perfectly good system upstream."

"I feel taking the lake water isn't the safe way to go," he said.

If approved by council, the city's drinking water source will change to Yellowknife Bay around 2020 to coincide with the end of the water pipeline's lifespan.

The construction of a water treatment plant is a requirement of the federal government and will happen whether the water source is changed or not, said Mayor Gord Van Tighem.

"In the regulations that the Canadian Council for Ministers of the Environment put out about two or three years after Walkerton, it requires that there be filtration and we didn't do filtration before," he said.

Currently, Yellowknife tap water is only screened to keep out debris and fish and then chlorinated at Pumphouse No. 1.

The new plant, scheduled to be built in 2012 for about $18 million, will use a membrane filtration system that traps small particles in the water, such as silt and sediment.

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