Third link: Drilling in the river this summer

Preparatory work for the third link will take place this summer with the completion of eight boreholes that will test the seabed of the St. Lawrence River to a depth of 80 metres.


Photo agency QMI, René Baillargeon

This was confirmed by Transport Minister François Bonnardel and the director of the Third Link project office, Dale Robinson protocolyesterday.

“It shows that we are doing the job. We want to carry out this important project for Lévis and the people of Quebec. It is a very serious first step to seek the scientific and technical data that will lead us to make the right decisions for the future,” said the minister.

In the middle of the river, between Québec and Lévis, near the crossing sector, lies a vessel specially equipped for geotechnical surveys. The cores taken from the bottom of the river will make it possible to learn more about the nature of the soil in which the future tunnel will be dug.


Photo agency QMI, René Baillargeon

in the rock

As part of the preliminary work, 20 holes have already been drilled, 13 on the North Shore, five on the South Shore and two in the St. Lawrence River.

“Preliminary data indicates that this is rock where the TBM will be placed,” confirmed Mr. Robinson.

Some experts were concerned about the possible presence of a very deep underwater canyon filled with sediment at the bottom of the river on the route. According to Mr. Robinson, this has not been observed before.

However, should the tunnel boring machine encounter loose rock, he believes that this would not endanger the project. “Whether it’s sediment or rock, we have the ability to create the design required. »

The depth of the rock imposes additional restrictions on the tunnel’s gradients, the engineer points out.

“The geological aspect between Quebec and Lévis means that technically this is a project that requires top-level expertise. »

These eight new drill holes will “complete this crucial phase of the project,” officials say.

At this point the river has a depth that varies between 30 and 55 meters. The drill holes will be tested at 65 and 80 meters below sea floor level. They take place from July to October.

Day and night

The barge was specially adapted for this work. A team of 15 to 20 employees works there. It has 75 m high anchor piles and suitable lifting towers. Drilling takes place day and night.

“To my knowledge, this type of drilling has never been done. It’s still very special, technically it’s important,” said Dale Robinson.

The Ministry of Transport is reluctant to present the studies on the third link.

One of them, which dates from 2020 and depicts the potential impact of the project on spatial planning, remains unavailable to the public.

Minister Bonnardel reiterated that he would publish all elements of the project “in due course”. It promises an annual update in spring.

Referring to Quebec Mayor Bruno Marchand, who asks for more information before commenting on the project, the minister reiterates that “the challenge is to reassure”. He promises to “resolve concerns”.

20 boreholes already drilled

  • 13 on the south coast
  • 5 on the North Shore
  • 2 in the river

8 holes follow

  • In the river, at a depth between 65 and 80 m in the seabed, from July to October 2022

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