Arsenic emissions | The Horne Foundry could reach 20 ng/m⁠3

The Horne Smelter could reduce its arsenic emissions to a level that would achieve a concentration of 20 nanograms per cubic meter (ng/m^⁠3), much closer to the standard of 3 ng/m^⁠3 what the Quebec government suggests.

Jean-Thomas Léveillé
The Press

Prime Minister François Legault’s office said last Monday that the company had proposed a threshold of 60 ng/m^⁠3 in the application for renewal of his ministerial authorization, filed in May; a proposal that Quebec said it had rejected.

However, “the company’s proposals are found in an action plan submitted by the foundry in February 2022 and not in the request for renewal of the ministerial authorization”, recognized Thursday the Ministry of the Environment and the Fight against climate change (MELCC).

The Horne Foundry transmitted to The Press the document in question, which makes no mention of a threshold of 60 ng/m^⁠3 ; it rather evokes “a potential concentration range” of arsenic between 20 and 64 ng/m^⁠3.

This large difference is attributable to several factors, explains the document: the accuracy of “plus or minus 50%” of the atmospheric dispersion model, the actual performance of the proposed solutions, the interrelationships between the different solutions and the “variability” of the winds, which has an influence on the concentrations measured in the air.

The calculations have been refined since the plan was tabled and the Horne Foundry has sent the government a revised downward proposal, which it does not wish to publicly disclose at this time, however, the company told The Press Alexis Segal, company spokesperson.

The office of the Minister of the Environment for the Fight against Climate Change, Benoit Charette, argued Thursday that the limit of 60 ng/m^⁠3 “was mentioned as average during work meetings with the foundry”.

Reductions… by 2027

The Horne Foundry states in its action plan that the reduction of its emissions could materialize “by 2027”, the time to put in place the proposed solutions.

This schedule corresponds to the scheduled expiry of its next ministerial authorisation, which should theoretically cover the period from 2022 to 2027 – this document, which makes it possible to derogate from the ban on polluting provided for in the Environment Quality Actwas previously called “decontamination certificate”.

In addition to reducing arsenic emissions, the company’s action plan also details the expected reduction in sulfur dioxide (SO₂), which could reach 40%, and total dust emissions, which could be 10%.

However, it does not propose a specific limit for other heavy metals emitted by the smelter, such as mercury, nickel, lead, antimony, chromium, cadmium or beryllium.

The foundry decontamination certificate currently in force does not impose any specific limit for metals other than arsenic.

Nine solutions

The Horne Smelter’s action plan is a requirement of the company’s current clean-up certificate, the company said. The Press MELCC spokesperson Sophie Gauthier.

It details nine solutions proposed by the smelter to reduce the concentrations of contaminants it generates, which represent total investments of $500 million.

Of the lot, the PHENIX project has the greatest potential for reducing arsenic emissions; this new process, which reduces the number of steps required for the transformation of copper, could on its own lead to a reduction of 10 to 15% in emissions.

The ongoing development of a “transition zone” between the foundry and the first residences in the Notre-Dame district should result in a 5 to 10% reduction in arsenic concentrations in the air.

The acquisition of these residences by the company will allow it to remove the “legal” air sampling station from its facilities, by moving it to the new boundary of its property.

This move would create a methodological problem, deplores lawyer Philippe Biuzzi, from the Quebec Center for Environmental Law.

“You will no longer be able to compare the data taken at point A with the data taken at point B,” he explains.

Other proposals by the company to reduce its emissions include increasing indoor storage of the concentrates it smelts, to “reduce wind-borne dust entrainment”, paving of traffic lanes and concentrate unloading area, the improvement of existing dust collectors, and the capture and treatment of air from certain roof vents.