Nfld. & Labrador

Nalcor continues Muskrat Falls cofferdam repairs, no damages reported yet

Nalcor and its contractors are still working to repair a temporary dam at the Muskrat Falls hydroelectric project which leaked in November.

Gilbert Bennett estimates a couple more weeks until dam is satisfactory

An illustration provided by Nalcor shows guards, including a tailrace protection cofferdam, added to the Muskrat Falls site to prevent ice damage over the winter. (Submitted)

Nalcor Energy and its contractors are still working to repair a temporary dam at the Muskrat Falls hydroelectric project which leaked in November.

That leak forced the release of water held in a reservoir upstream and threatened damage to the work site as ice forms on the Churchill River.

The temporary upstream cofferdam — designed to keep the construction area dry when water levels are elevated — is being sealed with grout, according to Gilbert Bennett, a Nalcor vice-president in charge of power development.

"I think it'll probably take another couple of weeks until we have this grouted to the point where we are satisfied with the performance of the dam," Bennett told CBC's Labrador Morning.

After the leak in the fall, Nalcor had to lower water levels and come up with a plan to avoid ice damage.

Flooding the reservoir was supposed to help ice form in one uniform piece, instead of uneven chunks which could break off and crash into the construction site or get stuck in the spillway.

So far, Bennett said there hasn't been any ice damage.

Nalcor's Gilbert Bennett says there hasn't been any ice damage yet this winter but there is still a potential threat. (CBC)

"From a weather perspective, it looks like a fairly average winter in terms of ice production," Bennett said, but added "it has potential to become an issue."

Once the cofferdam is repaired, Nalcor can begin, again, to raise water levels in the reservoir.

That will also help prevent damage downstream, where natural ice dams tend to form annually, causing water and ice to back up, Bennett said. Nalcor also installed more reinforcements around the powerhouse to keep ice and water out.

Communicating risks to recreational users

Back in November, Stan Marshall, president of the crown corporation, said the threat of ice damage to the Muskrat Falls site could cause Nalcor's insurers to cancel coverage, but Bennett says that hasn't happened.

"That risk exists, and we need to take action to mitigate that, and those are the steps we're taking today," said Bennett.

As grouting continues, Bennett said workers have already begun opening and closing the five spillway gates to make sure they work.

Bennett said there's no risk in changing water levels downstream in and around areas like Mud Lake, but added snowmobilers should keep an eye out for hazards as water and ice conditions change.

"Downstream, no concerns, we're not going to be releasing water in an uncontrolled manner," Bennett said.

"We will communicate to recreational users that there are hazards that exist today upstream."


Bailey White

CBC News

Bailey White is the producer of the St. John's Morning Show, on CBC Radio One.