St Marys Underground Expansion: Will a mine be a good neighbour to a marsh?

Where do you draw the line between “moderate” and “significant” environmental effects?

Are the dust and diesel emissions from a large mining operation likely to affect the health of an adjacent wetland?

In the case of the St Marys Underground Expansion proposal, those questions would appear to be closely linked.

Under Ontario rules for screening of proposed projects, a Category C project, judged at the outset to have “Moderate Potential Environmental Effects”, faces a less stringent consultation and approval process than a Category D project, which is judged at the outset to have “Significant Potential Environmental Effects”. (See A Class Environmental Assessment for Activities of the Ministry of Northern Development and Mines under the Mining Act.)

The St Marys Underground Expansion has been slotted as Category C. The determination that the project will have only “moderate potential environmental effects” appears to be based substantially on the claim that nearly all of the activities will take place underground, and the surface footprint of the current operation will not change.

But the Project Description doesn’t give serious consideration to the cumulative effects of limestone dust and diesel emissions produced by a doubling of the scale of the extraction activities.

The St Marys operation in Bowmanville is adjacent to a conservation area which includes two marshes – the Westside Marsh and Bowmanville Marsh. Both are designated as provincially significant wetlands, and both are downwind from St Marys when the prevailing westerly and southwesterly winds are blowing.

Graphic adapted from Bowmanville Expansion Project Description, page 12. The lines at bottom marked “Declines” represent the tunnels in and out of the proposed mine.

The current quarrying operation takes out about 4 million tonnes of limestone annually, and the underground mine is projected to take out an additional 4 million tonnes.

The initial plans call for mining and primary crushing to take place underground. All the air that is pumped into the mine will be pumped back out via the exhaust tunnel. There is the potential for dust produced underground to come out with the exhaust flow; the Project Description gives little detail on how dust will be managed.

There will be additional processing of the mined limestone above ground, so there is the potential for more limestone dust being swept up in the wind.

Last but certainly not least, several hundred trucks per day will be required to haul the limestone off to market – at 20 tonnes per truck, the 4 million tonnes per year would fill 200,000 trucks.

How can we be sure that the dust and diesel particulate emissions from all this crushing and trucking will have no “significant environmental effects” on the adjacent marshes? The Project Description neither asks nor answers this question.

In a table discussing Potential Project Effects, the document repeats the same basic phrases in regards to “Areas of ecological importance, including protected areas”, “Views or aesthetics”, “Aquatic species or habitat”, “Terrestrial species or habitat”, “Endangered species”, “Migratory bird species”, “Surface water quality”, and “Soils – contaminants, sedimentation, erosion”. Regarding all these concerns, the Project Description says there will be no significant effects “since all activities will occur beneath the bed of Lake Ontario or within the existing licensed quarry area”.

It is important that in the next phase of the project screening, the possible effects of emissions get more attention in order to ensure that years of marsh rehabilitation work do not go for naught.

Central Lake Ontario Conservation Authority (CLOCA) has this vision for the Westside and Bowmanville Marshes in 2026: “The Marshes are Clean, Green, Blue, Peaceful …. All living things enjoy the protected, tranquil area of the Bowmanville/Westside Marshes Conservation Area. The wooded, old field and wetland areas of the Bowmanville/Westside Marshes provide attractive habitat for abundant wildlife, and a diversity of trees and plants. … Neighbors are implementing effective plans to minimize disruption and noise ….” (Bowmanville/Westside Marshes Conservation Area Management Plan)

But CLOCA reports also make clear that a lot of improvement is needed. A 2006 report indicated that the wetland areas of Westside and Bowmanville Marsh both ranged from “poor to good health”. A 2014 Public Information Centre on Bowmanville Marsh Restoration reported “submerged aquatic vegetation and amphibians in poor condition”, and “birds in fair condition, but showing signs of decline”.

Frogs are thought to be especially sensitive to environmental contaminants, and frogs are remarkably scarce in these marshes now. How much more air-borne pollution will settle in the marshes due to a doubling of heavy equipment emissions at the adjacent quarry/mine? Will frogs, other amphibians, and the many other inhabitants of the marshes be affected?

If the Bowmanville Underground Expansion goes ahead, will “All living things enjoy the protected, tranquil area of the Bowmanville/Westside Marshes”?

Snapping turtle at edge of Bowmanville Marsh, June 21, 2015.

Top photo: St Marys Cement quarry and kiln, February 14, 2016.