| Summary: | The Rayrock Mine Site is located about 145 km northwest of Yellowknife and 56 km north of Marian Lake. Rayrock Mines Limited recovered 458,000 pounds of yellow-cake between June 1957 and July 1959, leaving about 80,000 tons of tailings in two piles to the south of the mine site. The piles cover an area of about 6 and 8 ha. are free of vegetation and have small water bodies in depressions on the edges of the pile and at lowest points of the pile. These waters directly in contact with tailings appear to be high in radium and copper, reflecting the elevated concentrations of these elements in the tailings. Radium. and lead-210 concentrations are high in the tailings compared to other abandoned or inactive uranium mill tailings sites in Canada. However, the concentrations in the waste material can range from 350 to 3,300 pCi /g for Radium-226 and 350 to 3,000 pCi/g for Lead-210. A representative average concentration for Radium-226 and Lead-210 in the Rayrock tailings cannot be determined as only a small sample set has been analyzed. Contaminated soil underneath a tailings cover, particularly in the North tailings pile arid on the edges of both piles, was found. The size of the area with contaminated soil is not known , but. this soil may be a source of contamination for vegetation rooted below the thin tailings cover. A second possible source of contamination of vegetation in the vicinity may be windblown tailings originating from the more dry, South tailings pile. Although the coarse tailings are weak acid generating and have been in contact with some water bodies for more than two decades, the water pH has riot been affected. The water quality parameter analyzed for Sherman Lake and the downstream system suggest, tentatively, that on the small Lakes Alpha and Gamma have been contaminated, but all other water bodies show no evidence of contamination related to the tailings decomposition.
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