St Marys mine – Article Index

The St Marys Cement Underground Expansion Project envisions extracting 4 million tonnes of limestone each year from a new mine beneath Lake Ontario on the south side of Bowmanville.

To understand the scope of the project and its possible environmental effects, it helps to look at the logistics: how much transport capacity does it take to move 4 million tonnes per year?

St Marys says that the limestone will be shipped out as aggregate “using existing road, rail and/or dock infrastructure.” These three shipment methods have very different environmental effects, and presumably there will be further detail on the likely mix of shipping modes in the Environmental Assessment.

In coming to terms with the quantities involved, however, marine shipping is the easiest to picture. The bulk carrier Capt. Henry Jackman is a frequent visitor to the St Marys dock. It carries up to 30,550 tons of cargo (source: boatnerd.com) or 27,715 tonnes. To haul away 4 million tonnes, the Capt. Henry Jackman (or similar-sized ship) would need to make 144 trips. This would equal about 4 trips per week during an eight-month shipping season.

Since outgoing shipments of aggregate would be in addition to all the current in- and out-going shipments at the St Marys dock, one key question is: how many boatloads of aggregate could be shipped out each year assuming there are no significant changes to the docking infrastructure?

While marine transport is by far the most efficient in terms of fuel consumed per tonne per kilometer, the market for aggregate may not favour bulk port-to-port shipment. If most of the limestone aggregate is destined for construction projects scattered all around the Greater Toronto Area, then trucking will be the most cost-effective shipping method.

Suppose all the aggregate were trucked to market. Using a round figure of 20 tonnes per truck load, the 4 million tonnes would be 200,000 truckloads per year – about 770 loads each day if the hauling is done five days/week, or about 550 loads per day if hauling continues every day of the week.

There is a wide variance in truck capacity, from tri-axle dump trucks, to dump trucks with secondary trailers, to full-length tractor-trailers. However, unless most of the aggregate is sent by some combination of marine transport and rail, there will be hundreds of truckloads per day of aggregate exiting the quarry, in addition to the current shipments of cement.

The connection between the St Marys quarry and the road network is shown on the Google Maps image below.

Drivers who frequently use the Waverly Road/Highway 401 interchange just north of the quarry will attest that traffic frequently backs up at the on/off ramps for eastbound traffic (on the south side of the 401). What effect would a few hundred extra trucks/day have on this traffic?

A major recreational feature, the Waterfront Trail, would also be impacted by the additional traffic. The Waterfront Trail is routed along Waverly Road and Energy Drive just north of the quarry:

Looking west on Waterfront Trail, at junction with Waverly Road.

Users of the Waterfront Trail share the road with traffic entering and exiting the 401 in this interchange:

Looking west from Waverly Road along Energy Drive, with on/off ramps for 401 eastbound traffic.

Truck traffic going north on Waverly Road and County Road 57, or going to the westbound 401, will use the narrow bridge over the 401:

Waverly Road bridge over Highway 401 to Bowmanville and to westbound 401 access ramp.

This bridge is part of one of the two current cycling routes between Bowmanville and the Waterfront Trail (see Getting Across the 401). The combination of a narrow bridge with merging and turning traffic on either side of the bridge makes this a dangerous passage for cyclists, even without adding several hundred more heavy trucks each day.

The transport of 4,000,000 tonnes of limestone aggregate may have significant implications re traffic congestion and danger to vulnerable road users. When coupled with the wear and tear on roads and the emissions from diesel engines, the impact of transportation will be an important part of the Environmental Assessment of this project.

Top photo: the Capt. Henry Jackman approaching the St Marys dock, August 2016.