It should be known within the next week or so how well an unusual construction engineering experiment worked out in Timmins this past winter.

The unique engineering venture involving Goldcorp Porcupine Gold Mines and local contractor Chartrand Equipment was designed to remove hundreds of thousands of tons of earth from the middle of Three Nations Lake without upsetting the environment.

The project was a first for Northern Ontario, and the size of the project may make it a first anywhere in North America.

The decision to remove the massive amount of soil from the lake was one of the final steps in the $89 million Pamour Pit project that saw Goldcorp actually moving part of the lake so it could create a new open pit below the old lake bed. A large part of the north end of the lake, near the old Highway 101, was dammed off and dug up to allow for the pit.

Goldcorp was required to create a new portion of the lake, at least as big as the old portion of lake that was to be located in a swamp at the southeast edge of Three Nations Lake.

Goldcorp project supervisor Roger Taillefer explains that the job of creating a new section of lake went well. Work began in the fall of 2005 and continued through the winter of 2005-06 as massive excavators dug up the swamp area and created a new lake basin three to four metres deep.

The whole process was carefully watched and approved by the federal Department of Fisheries and Oceans (DFO), the Ontario Ministry of the Environment and the Ontario Ministry of Natural Resources.

In the spring of 2006, the new lake basin began filling with water … but it wasn’t quite part of Three Nations Lake just yet. DFO has instructed that an “earth plug” — basically an earthen wall — had to be constructed to separate the old lake from the new lake.

Taillefer says this was to allow the new lake to adjust to the local eco-system. Vegetation had to occur and the shoreline was worked to make it as much as possible like a real lake with deadfall logs and gravel beds for fish spawning areas.

Once it became clear the new lake was in fact become part of the eco-system, DFO directed that the earthen wall separating the two lakes had to be removed.

Taillefer said that presented a problem, because no one had a tried and true method for removing an earthen wall more than 100 metres long, without causing environmental damage. The old days of just blasting the wall away would not be acceptable. He said mining company officials worked on the idea for several weeks when it was decided to consult with Chartrand Equipment. Taillefer said the company has shown itself to be expert at working in northern conditions.

He says that’s when Chartrand presented the idea of freezing the lake right down to the lakebed, placing heavy excavators on top of the ice and digging down to remove the earthen wall.
Taillefer said it required the company to bring in snow making equipment which created a mound of snow and ice nearly three-storeys high. The weight of the snow and ice was such that it pushed down and squeezed away all the water below it.

“Our intention was to go in after the lake was frozen, take the centre of this ice plug out, take the dirt out, fill it back up with snow and then just let it thaw afterwards,” said Taillefer.
The idea worked. Thousands of tonnes of snow, ice, soil and what the workers called “loonsh*t” were successfully dug out, loaded up and trucked away.

Taillefer said it was a good idea, a novel idea, that worked. “What we accomplished here was something quite unique,” said Taillefer.

Article ID# 1527186
Story by Len Gillis
Timmins Times