More Water Problems at Cigar Lake

Engineering and Mining Journal, Sep 2008

Cameco Corp. reported on August 12, 2008, that renewed water inflows at its underground Cigar Lake uranium project in northern Saskatchewan had forced suspension of remediation work in the mine's No. 1 Shaft. Flooding brought major underground development at the project to a halt on October 23, 2006, and the company has been working since that time to get the project back on track.

The No. 1 Shaft had been pumped down to 430 m below surface when the most recent increase in water inflow occurred. The rate of inflow rose to about 600 m^sup 3^/hr, which was beyond the volume that could be managed while continuing to work in the shaft. The mine has a total depth of 500 m, and underground workings are at the 480-m level. Work in the shaft was suspended while Cameco engineers sought to determine the source and characteristics of the inflow, the implications for planned remediation work, and the impact on Cameco's planned production date.

"No doubt this is going to delay things," Cameco president and CEO Jerry Grandey said. "We've got to understand where the inflow is coming from, and once we understand that, then we're going to have to develop a plan to deal with it."

The company said remediation plans for the project contain options to address excess water inflows, including additional grouting from surface and ground freezing if necessary. Pumping capacity is 1,000 m^sup 3^/hr from four dedicated dewatering pumps installed in wells down to the 500-m level. The water management system is limited by the treated water release limit of 550 m^sup 3^/hr under the existing license. A 74,000-m^sup 3^ contingency storage pond at the surface allows pumping at rates above the release limit for a limited period.

The Cigar Lake project is a joint venture owned 50% by Cameco; 37% by AREVA Resources Canada; 8% by Idemitsu Canada Resources; and 5% by TEPCO Resources. The project is based on the world's largest undeveloped high-grade uranium deposit. Proven and probable reserves total more than 226.3 million lb of U^sub 3^O^sub 8^ at an average grade of 20.7%. Cameco is the operator.