Mike W. Bryant
Northern News Services

Yellowknife (Aug 31/01) - Diavik Diamond Mines say all is well after heavy winds partially washed away a containment barrier last week, designed to keep sediments from escaping its dredging site at Lac de Gras.

A Department of Fisheries inspector was on site Aug. 23, and noticed at least two areas where the barrier -- called a sediment curtain -- had been dislodged by wave and wind action three days earlier.

In at least one location, a sediment plume was observed flowing out of the curtain and into Lac De Gras.

The 4-5 kilometre plastic curtain was erected two months ago. Inside it, dredging crews are working to construct a rock and gravel dike in which the mine will eventually be excavated.

According to Diavik's executive director of public and governmental affairs, Tom Hoefer, up until this most recent storm the curtain has been a success.

"In the two months the curtain has been in place, it definitely works," said Hoefer.

"If a storm wind comes it should push some of the sediment underneath it."

Hoefer further explained that the curtain does not extend all the way to the bottom, but suspended sediments should be deep enough that they settle quickly once passed through.

The curtain also allows fish -- such as lake trout -- to find their way in and out of the dredge site.

The dike inside the curtain should be completed by late October.

A phone call made to Environment Canada could not determine actual wind speeds at the Lac de Gras site last week, but in Yellowknife -- 200 kilometres away -- winds reached speeds of approximately 40 km/hr on the morning of Aug. 21.

When asked if the curtain could withstand higher wind speeds than that, Hoefer couldn't answer.

"Our guys will have to deal with it," he said, but did not say how.

"We'll have to wait and see."

Regardless, the Mackenzie Valley Land and Water Working Group -- who oversee Diavik's water licence -- feel that the mining company has been operating well within established guidelines.

"Breaks in the curtain are unavoidable," said Karl Lauten, manager of regulatory reviews for the Group.

"You have to put in perspective. They have a pretty high standard of containment at the site."

Lauten added that the mine is well below the maximum parts per million of suspended solids allowed outside the curtain. Water tests put the number at Lac de Gras as under 10 parts per million. The maximum allowed is 25 parts per million.

Area habitat biologist Marc Lange said the Department of fisheries and Oceans would like to see the mine do a little better in securing the sediment curtain, but likewise saw few problems either.

"I think everybody would like no sediments being deposited in the area, even if they are meeting thresholds," said Lange.

"If the anchor points (for the curtain) can be anchored in such a way that they're not being released during storms, then we should be looking into it."