September 12, 2012

Aggregates

Pits and quarries have future benefits: OSSGA

ONTARIO STONE, SAND AND GRAVEL ASSOCIATION

This is a rehabilitated aggregate extraction site at Kelso Quarry Park in Milton, Ontario.

PETER KENTER

correspondent

Part of the debate over the establishment of new aggregate sites involves the condition of former pits and quarries after the sites are decommissioned and rehabilitated.

A new study undertaken by the Ontario Stone, Sand and Gravel Association (OSSGA) attempts to quantify the condition of 337 rehabilitated aggregate sites in southern and eastern Ontario for which licences had been surrendered and rehabilitation completed.

“We didn’t embark on the study to deliver a glowing report on aggregate site conditions,” says Mike Scott, policy and legislation manager with the OSSGA and one of the authors of the study.

“We wanted to look at these sites and examine their current condition using objective criteria, identify rehabilitation trends and provide recommendations to the industry where we felt that more could be done in improving achievable long-term rehabilitation outcomes. Many sites were exemplary, while some were not what we wanted to see.”

The report argues that locating aggregate extraction sites closer to population centres where roadbuilding and other construction projects will use the product provides a net economic and environmental benefit.

Only by overcoming the perception that former extraction sites are left as “open scars” on the landscape and demonstrating that aggregate extraction represents a temporary land use will that benefit be realized.

Employing site visits and aerial photography, each of the study’s subject extraction sites was analyzed and five types of data collected.

These include: percentage of tree coverage; percentage of native vegetation; current site use; surrounding land uses; and municipal zoning.

The predominant current land uses of the rehabilitated sites in the study were varied. The sites were predominantly natural (32 per cent), residential (15 per cent), recreational (13 per cent), water (11 per cent), and open space (11 per cent), with the remaining sites were made up of industrial, agricultural, commercial, institutional, and other land uses.

The sites were largely vegetated, demonstrating 17 per cent tree coverage. An estimated 66 per cent of the plant life consisted of vegetation native to Ontario.

“We chose those standards, because tree cover and native vegetation are indicators of general ecological health,” says Scott.

The report notes that the rehabilitation of extraction sites usually includes grading slopes, applying subsoil and topsoil, and planting vegetation.

Once the extraction process is completed, the rehabilitated site may be more productive or better integrated to its surroundings than it was originally.

Scott says that the field research portion of the study provided some interesting observations.

“Of the total number of sites we visited, 82 of them were located in the area known as historical Metropolitan Toronto,” he says.

“In some cases, we were visiting residential sites where the house was now occupied by the second or third owner. Some of the people were completely unaware that their home was located on a former aggregate site.”

Among the study team’s recommendations: the creation of a central agency to collect additional data; the establishment of enhanced standards for data collection on surrendered sites; and the refinement of site rehabilitation best practices, combining the expertise of all stakeholders.

The team also recommends that future rehabilitation should concentrate on site-specific ecologies, focusing on achieving ecosystem and land-use objectives found in the surrounding landscape.

Rehabilitation efforts should also stress the seeding of native species.

“What’s interesting is that the bar is constantly being raised on site rehabilitation practices,” says Scott.

“A site rehabilitated 75 years ago might be replanted with readily available vegetation, while one rehabilitated today would be deliberately seeded with native vegetation.”

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