Uneven Soil in Beauport Causes Concerns

Uneven Soil in Beauport Causes Concerns

On Shaky Ground: Uneven Soil in Beauport Causes Concerns

Les grottes de Courville or Courville Caves are largely responsible for the soil instability found along Rue Brideau and Xavier Giroux says Jacques Schroeder, UQAM’s professor of geomorphology.

For forty years, Schroeder has mapped various cavities of the Courville cave network on the behalf of the former City of Beauport and the current City of Quebec. These caves are a roadway for a large amount of water from the Montmorency River, which passes through here before finishing its course in la chute de la Dame Blanche, west of the Montmorency falls.

During the 80s and 90s, Schroeder explored and mapped two of these cavities located near the spot where four residential buildings have recently been condemned by the City of Quebec. These buildings were built in an area where once stood an old quarry, backfilled to allow for residential construction.

One of these cavities is located north of the old quarry and the other to the south. Schroeder believes that the soil instability has been caused by water flowing between these two cavities passing through the deepest part of the old quarry area, which has the effect of shifting sand, soil and any other material used to backfill the quarry.

“It’s not their fault of the developers, but of the caves,” he says. Water is deposited in them, and it is causing the soil to shift.
All this water comes from the Montmorency River more specifically a natural dam built upstream in 1908 where water trickles into the limestone crevices, which leads into the Courville cave network. Schroeder argues that if we lowered the water level of the dam over a meter, the water flow into the caves would decrease which would limit the problems of soil stability in the area on rue Brideau and Xavier Giroux.

Aerial photographs from the 1950s confirmed the presence of a stream to the boundaries of the former quarry that has been backfilled to allow residential construction, says Jacques Perron, spokesperson for Quebec City. Neighbours also testified that they have played and swam in this stream when they were children.

This underground stream and the backfilling of motley ground which included glass, plastic, metal and even bones were found which have contributed to the instability of the soil. “It’s not just the only cause, but it is part of the equation,” says Perron.

To understand the movement of water between the caves and the affected area, the spokesman said that they would colour the water and then follow its flow.

A sum of $500,000 is already included in the three-year capital program to foresee studies and ad hoc work to stabilize the caves.

Last year Speltech, Schroeder’s company received $64,000 to explore 250 meters of caves. There are about 1.2 km of cave near the Montmorency River.

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