Restoring the landscape of an abandoned quarry

In the early 1970s, a large mountain of green granite was blasted and quarried to create products and contribute to the construction of Highway 20 in Lévis, Quebec. However, despite the importance of this project for the region, the mining of this mountain left a pit that filled with water over the years, resulting in the creation of the site known as Lac Vert. Wanting to limit the environmental risks associated with the presence of a water-filled pit, and to give the community back a pleasant landscape for the area, the owner called on Englobe to restore this abandoned former quarry.

 

The combined expertise of our teams

To achieve this, Englobe pooled the expertise of multiple teams, each of which contributed to the successful restoration of Lac Vert.

In 2014, our geo-environmental and natural environment teams started their conversation with the site owner by analyzing the site in terms of its environmental liabilities and the nature of the ecosystems found there. From then on, the issue of the existence of the lake was quickly put at the heart of the proposed plans. Englobe had to find the best way to make the most of the site. While emptying the pit proved to be the best solution, our teams had to plan in such a way that the methods and potential impacts were all properly assessed and minimized.

It was at this point that the Soil and Materials Engineering team came into play, bringing their in-depth expertise in hydrology to bear on the analysis of the impacts of "dewatering" the pit. This work also provided an opportunity for the natural environment team to attempt to figure out which animals were using the pit as a habitat, in order to relocate them before the water was withdrawn. Once this work had been completed, it was the geotechnical team's turn to get involved. They analyzed the mountain, which had been partly destroyed by quarry activity and the passage of time. They had to establish how the soils could be used and placed to stabilize the whole area efficiently and safely.

A pioneering quarry restoration project

One of the project's turning points came in July 2016, when our teams learned that the Ministry of the Environment (MELCC) intended to amend regulations to facilitate the reclamation of certain low-level contaminated soils. In the near future, these new regulations would allow the use of contaminated AB soils, which were otherwise destined for landfill sites. Englobe was a forerunner, presenting its project to the MELCC even before the regulatory changes. The Lac Vert site was the first in Quebec to reclaim AB soils.

"Initially, Englobe's mandate was to fill the quarry hole and develop the land for commercial purposes, but we came up with the idea of using low-contaminated AB soils and revegetating the whole area. This enabled us to promote the circular economy and restore the original landscape." (Hugues Lapierre, Senior Project Manager, Environmental Studies & Climate Change).

In 2018, obtaining the authorization certificate thus enabled the start of the mountain's restoration with the use of 175,000 m3 of contaminated AB soils. The Soil Treatment and Biomass Centers team stepped in to complete the final stretch of this project, making it a series of successful milestones.

A collective success

Thanks to the concept of the circular economy and collaboration between our various services and teams, Englobe was able to revive the mountain and restore its former landscape. Several species of trees were planted during the revegetation phase, including white pine, red oak and sugar maple. In terms of material, this means :

• 455,000 metric tons of soil received for the project;
• 2,500 metric tons of compost;
• 2,675 trees planted.