Dane Gibson
Northern News Services

NNSL (Jun 25/99) - An environmental evaluation determining arsenic levels around Con Mine and the Yellowknife area has been completed and although high levels have been detected, scientists say much the arsenic is naturally occurring.

The report, prepared by working groups from the Royal Military College of Canada and the University of British Columbia, highlighted several hot spots that need attention.

"High levels of arsenic are present (in the vicinity of Con Mine), and there is potential for environmental impact because of the mobility of this contamination," the final report stated.

Although mine tailing deposits were shown to be the source of the arsenic contamination, Royal Military College's Dr. Ken Reimer said there are high background levels of naturally occurring arsenic all over the region.

"The levels in someone's backyard, while elevated compared to Canadian criteria, are still well within what appears to be the natural geology of the area," Reimer said.

"I doubt that any of the samples we took from the soils around Yellowknife contained arsenic trioxide. The natural geological form of arsenic is definitely not as toxic."

Reimer said the national acceptable level of arsenic is 12 parts per million. His group determined the natural background level in the Yellowknife area to be between 60 to 100 parts per million.

"Although that may sound concerning, the levels in and around the city are in a range not inconsistent with the levels attributable to the natural geology," he said.

Water samples were also taken from the surrounding lakes. Kam Lake and Rat Lake are seriously contaminated by past tailings dumping. Also, since 1985, wastewater from Con has been pumped and discharged directly into the Meg-Keg-Peg Lake Wetlands.

"Peg Lake, which is not the lake closest to the contaminant source, contains the highest levels of arsenic. This shows that re-mobilization through the surface water and from particulate transport is indeed taking place," the report states.

"Even if mining operations were to cease, a subsequent period of uncontaminated sediment deposit may not slow or stop the re-mobilization of arsenic."

Reimer said the Great Slave Lake and Yellowknife River were not problem areas and that the tap water in Yellowknife is "perfectly safe."

The report recommended, among other things, further study in the Rat Lake area "as the contamination found here might constitute a human and ecological health risk."

It also stated that "further study of food chain effects may be prudent."