An upstream dike has been completed at Mount Polley Mine, allowing investigators to probe the site of the original Aug. 4 dam breach.

The new structure is to make the breach area safe for inspection and work below, not to repair the original breach or retain water in the tailings pond, said Steve Robertson, Imperial Metals vice-president for corporate affairs.

"We've finished construction of the upstream dike, and now we're establishing the sumps on the upstream side of that, and that will intercept the water that's going to continue to flow out of the tailings," Robertson said in an interview Friday. "If anything should get past that, we'll have another sump outside of the breach that will capture any water that comes out through the breach and make sure that it gets put into the reclaim system."

The sumps act as settling ponds, with the water pumped back up to another pit on the site of the copper-gold mine near Williams Lake.

Robertson said the continued work addresses the 's non-compliance notice issued to the company Sept. 9, regarding discharge of water into the Hazeltine Creek channel.

Most of the available mine employees are back at work, with about 30 working on cleanup around Quesnel Lake. Work is expected to continue until there is too much snow cover to continue.

The environment ministry released more water test results Thursday, showing water collected at various sites and depths in the area remains safe to drink.

The immediate area of the tailings spill remains a "do not use" zone, and Interior Health advises local residents to avoid drinking cloudy water.