Web posted Sunday, April 15, 2007

Heavy snowpack leads to flooding concerns at mine

By Tim Bradner
Alaska Journal of Commerce

There have been record-breaking snowfalls in the Juneau area this winter, and the spring thaw will be unusually wet and sloppy.

Coeur Alaska Inc. is watching a temporary cofferdam built at Lower Slate Lake near its Kensington Mine very closely out of concern that an unusually heavy melt could lead to erosion of the structure and flooding from the lake.

The cofferdam figured in an injunction ordered by federal courts stopping construction of a permanent dam at Lower Slate Lake after conservation groups filed lawsuits against federal permits issued to Coeur for mine construction.

Work on the permanent dam was stopped, but the cofferdam, built earlier to protect the construction site and intended to be taken down, remained. The temporary dam is an earth embankment 300 feet long, 12 feet high and 30 feet to 40 feet wide at the base.

In March the Ninth Circuit Court of Appeals turned down a request by the company to built a diversion channel for meltwater runoff to protect the cofferdam.

Coeur spokesman Scott Lamb said he couldn't comment on other steps the company is taking to protect the dam because of the litigation.

Tom Crafford, the state's large mine permitting manager in the Department of Natural Resources, said state and federal agencies are monitoring the situation closely and are working with Coeur on solutions.

Through pumping, Coeur has maintained water levels in Lower Slate Lake at levels that do not threaten the cofferdam — so far at least. But there are concerns about the buildup of meltwater and spring rainstorms that are common in the region, Crafford said.

“The company was put in an awkward situation. They started work based on approvals by the government given in permits and then weren't allowed to continue work,” Crafford said. “The cofferdam has been left in place much longer than what was intended.”

Tim Bradner can be reached at tim.bradner@alaskajournal.com.

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